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Background/aim: Ivermectin was initially utilized as a veterinary medication, demonstrating efficacy against various parasites. Pancreatic cancer is currently one of the most recalcitrant diseases. The aim of the present study was to demonstrate the synergy of the combination of recombinant methioninase (rMETase) and ivermectin to eradicate human pancreatic cancer cells in vitro., Materials and Methods: MiaPaCa-2 human pancreatic cancer cells were cultured in Dulbecco's modified Eagle's medium (DMEM) with the addition of 10% fetal bovine serum and 1 IU/ml penicillin/streptomycin. Reduction of cell viability by rMETase alone and ivermectin alone and their combination on MiaPaCa-2 cells was determined with the WST-reagent. Four experimental groups were examined in vitro: control group without treatment; ivermectin alone; rMETase alone; ivermectin combined with rMETase., Results: The IC 50 of ivermectin for MiaPaCa-2 cells was 5.9 μM. The IC 50 of rMETase on MiaPaCa-2 cells was 2.93 U/ml. Ivermectin (5.9 μM) plus rMETase (2.93 U/ml) synergistically greatly reduced the viability of MiaPaCa-2 cells, compared to ivermectin alone (80% reduction vs. 45% reduction, respectively p<0.05)., Conclusion: The combination of ivermectin and rMETase effectively eradicated MiaPaCa-2 pancreatic cancer cells. The present results indicate the future clinical potential of the combination of rMETase, currently administered orally to patients as a dietary supplement, and oral ivermectin on pancreatic cancer., (Copyright © 2025 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Methionine addiction, known as the Hoffman effect, makes cancer cells more sensitive to methionine restriction than normal cells. However, the long-term effects of methionine restriction on cancer and normal cells have not been thoroughly studied., Materials and Methods: HCT-116 human colorectal-cancer cells and Hs27 normal skin fibroblasts were treated with 0-8 U/ml of recombinant methioninase (rMETase) for 12 days. The cells were cultured in Dulbecco's modified Eagle's medium in 96-well tissue-culture plates., Results: HCT-116 cells were sensitive to all concentrations of rMETase from 0.125 U/ml to 8 U/ml. After day-8 of treatment, HCT-116 cells were acutely sensitive to rMETase, especially at rMETase concentrations of 0.5 U/ml or higher. Normal Hs27 fibroblasts were much less sensitive to rMETase: In the range of 0.125 U/ml to 0.5 U/ml, rMETase had no effect on Hs27 cells. rMETase concentrations up to 2 U/ml had a slight initial effect on Hs27 cells, whereas at concentrations ranging from 4 U/ml to 8 U/ml, rMETase reduced Hs27 viability over the 12-day test period, with acute loss of viability observed after eight days of exposure., Conclusion: Cancer cells were significantly more sensitive to rMETase than normal cells, with an acute loss of cell viability observed in cancer cells after eight days of treatment at concentrations of 0.5 U/ml or higher. These findings highlight the large difference in sensitivity between cancer and normal cells to rMETase and introduce the phenomenon of acute cell death in methionine restriction, which we term "methionine-depletion catastrophe"., (Copyright © 2025 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Docetaxel combined with gemcitabine is a second-line treatment for soft-tissue sarcoma; however, its effectiveness is limited because of docetaxel resistance. The objective of the present study was to determine the potential of recombinant methioninase (rMETase) to enhance the efficacy of docetaxel on high-docetaxel-resistant human fibrosarcoma cells in vitro., Materials and Methods: Docetaxel-resistant HT1080 (DTR-HT1080) human fibrosarcoma cells were established by culturing them in by progressively increasing concentrations of docetaxel from 0.02 to 9 nM in vitro. The IC 50 values for docetaxel and rMETase, as well as the efficacy of their combination, in inhibiting HT1080 human fibrosarcoma cells, DTR-HT1080 cells, and Hs27 normal human fibroblasts were determined. Four experimental groups were examined in vitro: control group without treatment; docetaxel alone; rMETase alone; docetaxel combined with rMETase., Results: The IC 50 of docetaxel for DTR-HT1080 cells was 7.57 nM, compared to the parental HT1080 cells with an IC 50 of 1.68 nM, a 4.5-fold increase. The IC 50 of docetaxel on Hs27 fibroblasts was 4.46 nM. The IC 50 of rMETase on HT1080 cells was 0.75 U/ml (data from [6]). The IC 50 of rMETase on DTR-HT1080 cells was 0.55 U/ml. The IC 50 of rMETase on Hs27 fibroblasts was 0.93 U/ml (data from [6]). Docetaxel (1.68 nM [IC 50 ]) plus rMETase (0.75 U/ml [IC 50 ]) synergistically reduced the viability of HT1080 cells (p<0.05). In contrast, docetaxel (4.46 nM) plus rMETase (0.93 U/ml) did not reduce the viability of Hs27 fibroblasts, compared to either agent alone. The combination of rMETase (0.55 U/ml [IC 50 ]) and docetaxel (1.68 nM [IC 50 of the parental cells]) overcame docetaxel resistance of DTR-HT1080 cells, resulting in an inhibition of 48.1% compared to docetaxel alone (6.8%) or rMETase alone (37.5%) (p<0.05). rMETase thus increased the efficacy of docetaxel 7-fold on docetaxel-resistant human fibrosarcoma cells., Conclusion: The combination of docetaxel and rMETase was synergistic on HT1080 fibrosarcoma cells, but not normal fibroblasts. rMETase plus docetaxel synergistically reduced the high docetaxel resistance of DTR-HT1080 cells. The present results indicate the clinical potential of rMETase to reduce docetaxel resistance in soft-tissue sarcoma patients in the future., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Docetaxel combined with gemcitabine is a second-line therapy for osteosarcoma, but its efficacy is limited by the development of docetaxel resistance. The aim of the present study was to determine whether recombinant methioninase (rMETase) could reverse docetaxel resistance developed in osteosarcoma cells., Materials and Methods: Docetaxel-resistant 143B (DTR-143B) osteosarcoma cells were established by treating the parental 143B cells to increasing docetaxel concentrations (0.14-24 nM) over 5 months. The 50% inhibitory concentration (IC 50 ) of docetaxel and rMETase as well as their combination on human osteosarcoma cells 143B and DTR-143B were determined. Four groups were analysed in vitro: untreated control; docetaxel; rMETase; docetaxel plus rMETase., Results: The IC 50 value of docetaxel for DTR-143B cells was 31.1 nM, compared to 4.38 nM for the parental 143B cells, a 7-fold increase. The combination of rMETase (0.53 U/ml) and docetaxel (4.38 nM) sensitized DTR-143B cells to docetaxel resulting in an inhibition of 73.7% compared to docetaxel alone (7.3%) or rMETase alone (54.6%) (p<0.05). rMETase thus increased the efficacy of docetaxel 10-fold on docetaxel-resistant osteosarcoma cells., Conclusion: rMETase reversed docetaxel resistance of DTR-143B in vitro. The present results indicate the clinical potential of rMETase to overcome docetaxel resistance in osteosarcoma patients., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Methionine restriction selectively arrests cancer cells during the S-phase of the cell cycle. We hypothesized that DNA damage may occur in S-phase in cancer cells during methionine restriction. To determine if this occurs, we used MiaPaCa-2 Tet-On 53BP1-green fluorescent protein (GFP) pancreatic cancer cells, which report GFP fluorescence in real time after DNA-damage response (DDR) in these cells. We also determined whether a chemotherapy drug in combination with methionine restriction increases the rate of DNA damage., Materials and Methods: MiaPaCa-2 Tet-On 53BP1-GFP cells were used for in vitro experiments. The 25% and 50% inhibitory concentrations (IC 25 and IC 50 , respectively) of recombinant methioninase (rMETase) and paclitaxel on MiaPaCa-2 Tet-On 53BP1-GFP pancreatic cancer cells were determined. Cell viability and DDR with rMETase alone, paclitaxel alone, and their combination were measured in MiaPaCa-2 Tet-On 53BP1-GFP cells., Results: The IC 25 of rMETase on MiaPaCa-2 Tet-On 53BP1-GFP cells was 1.66 U/ml. The IC 25 for paclitaxel on MiaPaCa-2 Tet-On 53BP1-GFP cells was 3.31 nM. The combination of rMETase and paclitaxel synergistically reduced the viability of MiaPaCa-2 Tet-On 53BP1-GFP cells. The IC 50 of paclitacel on MiaPaCa-2 Tet-On 53BP1-GFP cells was 5.1 nM. The IC 50 of rMETase on MiaPaCa-2 Tet-On 53BP1-GFP cells was 2.3 U/ml. The combination of rMETase (IC 50 ) plus paclitaxel (IC 50 ) on MiaPaCa-2 Tet-On 53BP1-GFP cells also caused more DNA damage than either agent alone., Conclusion: The present study suggests the synergy of methionine restriction and chemotherapy is due, at least in part, to DNA damage of cancer cells., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Drug resistance has been a recalcitrant problem for sarcoma patients for many decades. Trabectedin is a second-line chemotherapy for soft-tissue sarcoma that often leads to resistance and death of the patients. The objective of the present study was to address the issue of trabectedin-chemoresistance in HT1080 fibrosarcoma cells by combining recombinant methioninase (rMETase) with trabectedin and examining their efficacy on trabectedin-resistant fibrosarcoma cells in vitro., Materials and Methods: Trabectedin-resistant HT1080 (TR-HT1080) cells were generated by subjecting HT1080 human fibrosarcoma cells to increasing trabectedin concentrations (3.3-8 nM). IC 50 values for trabectedin and rMETase were compared for HT1080 and TR-HT1080 cells. TR-HT 1080 cells were placed into four groups to determine synergy of rMETase and trabectedin on TR-HT1080 cells: a control group with no treatment; a group treated with trabectedin (3.3 nM); a group treated with rMETase (0.75 U/ml); and a group treated with both trabectedin (3.3 nM) and rMETase (0.75 U/ml)., Results: The IC 50 value of trabectedin- on TR-HT1080 cells was 42.9 nM, whereas the IC 50 value of trabectedin on the parental HT1080 cells was 3.3 nM, indicating a 13-fold increase. The combination of rMETase (0.75 U/ml) and trabectedin (3.3 nM) was synergistic on TR-HT1080 cells resulting in an inhibition of 64.2% compared to trabectedin alone (5.7%) or rMETase alone (50.5%) (p<0.05). rMETase increased the efficacy of trabectedin 11-fold on trabectedin-resistant fibrosarcoma cells., Conclusion: The combined administration of trabectedin and rMETase was synergistic on the viability of TR-HT1080 cells in vitro. The combination of rMETase and trabectedin has promising clinical potential for overcoming chemo-resistance of soft-tissue sarcoma., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: A major challenge in treating soft-tissue sarcoma is the development of drug resistance. Eribulin, an anti-tubulin agent, is used as a second-line chemotherapy for patients with unresectable or metastatic soft-tissue sarcoma. However, most patients with advanced soft-tissue sarcoma are resistant to eribulin and do not survive. Recombinant methioninase (rMETase) targets the fundamental and general hallmark of cancer, methionine addiction, termed the Hoffman Effect. The present study aimed to show how much rMETase could increase the efficacy of eribulin on eribulin-resistant fibrosarcoma cells in vitro., Materials and Methods: HT1080 human fibrosarcoma cells were exposed to step-wise increasing concentrations of eribulin from 0.15-0.4 nM to establish eribulin-resistant HT1080 (ER-HT1080). ER-HT1080 cells were cultured in vitro and divided into four groups: untreated control; eribulin treated (0.15 nM); rMETase treated (0.75 U/ml); and eribulin (0.15 nM) plus rMETase (0.75 U/ml) treated., Results: The IC 50 of eribulin on ER-HT1080 cells was 0.95 nM compared to the IC 50 of 0.15 nM on HT1080 cells, a 6-fold increase. The IC 50 of rMETase on ER-HT1080 and HT1080 was 0.87 U/ml and 0.75 U/ml, respectively. The combination of rMETase (0.75 U/ml) and eribulin (0.15 nM) was synergistic on ER-HT1080 cells resulting in an inhibition of 80.1% compared to eribulin alone (5.0%) or rMETase alone (47.1%) (p<0.05). rMETase thus increased the efficacy of eribulin 16-fold on eribulin-resistant fibrosarcoma cells., Conclusion: The present study showed that the combination of eribulin and rMETase can overcome high eribulin resistance of fibrosarcoma. The present results demonstrate that combining rMETase with first- or second-line therapy for soft-tissue sarcoma has the potential to overcome the intractable clinical problem of drug-resistant soft-tissue sarcoma., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Doxorubicin is first-line therapy for soft-tissue sarcoma, but patients can develop resistance which is usually fatal. As a novel therapeutic strategy, the present study aimed to determine the synergy of recombinant methioninase (rMETase) and doxorubicin against HT1080 fibrosarcoma cells compared to Hs27 normal fibroblasts, and rMETase efficacy against doxorubicin-resistant HT1080 cells in vitro., Materials and Methods: The 50% inhibitory concentrations (IC 50 ) of doxorubicin and rMETase, as well as their combination efficacy, against HT1080 human fibrosarcoma cells, Hs27 normal human fibroblasts and doxorubicin-resistant HT1080 (DR-HT1080) cells were determined. Dual-color HT1080 cells which expressed red fluorescent protein (RFP) in the cytoplasm and green fluorescent protein (GFP) in the nuclei were used to visualize nuclear fragmentation during treatment. Nuclear fragmentation was observed with an IX71 fluorescence microscope., Results: The IC 50 for doxorubicin was 3.3 μM for HT1080 cells, 12.4 μM for DR-HT1080 cells, and 7.25 μM for Hs27 cells. The IC 50 for rMETase was 0.75 U/ml for HT1080 cells, 0.42 U/ml for DR-HT1080 cells, and 0.93 U/ml for Hs27 cells. The combination of rMETase and doxorubicin was synergistic against fibrosarcoma cells but not against normal fibroblasts. The combination of doxorubicin plus rMETase also caused more fragmented nuclei than either treatment alone in HT1080 cells. rMETase alone was highly effective against the DR-HT1080 cells as well as the parental HT1080 cells., Conclusion: The present results indicate the future clinical potential of rMETase in combination with doxorubicin for fibrosarcoma, including doxorubicin-resistant fibrosarcoma., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Cancer cells are addicted to L-methionine (L-Met) and have a much greater requirement for L-Met than normal cells due to excess transmethylation, termed the Hoffman effect. By targeting this vulnerability through dietary restriction of L-Met, researchers have been able to achieve promising results in inhibiting tumor growth and eradicating cancer cells. Methioninase (EC 4.4.1.11; METase) catalyzes the transformation of L-Met into α-ketobutyrate, ammonia, and methanethiol. The use of METase was initially limited due to its poor stability in vivo, high immunogenicity, and enzyme-induced inactivating antibodies. These issues could be partially resolved by PEGylation, encapsulation in erythrocytes, and various site-directed mutagenesis. The big breakthrough came when it was discovered that METase is effectively administered orally. The enzyme L-asparaginase is approved by the FDA for treatment of acute lymphoblastic leukemia. METase has more potential as a therapeutic since addiction to L-Met is a general and fundamental hallmark of cancer., Competing Interests: Declaration of competing Interest The authors declare no conflict of interest. This article does not contain description of studies involving human participants or animals performed by any of the authors., (Copyright © 2024. Published by Elsevier B.V.)

Background/aim: The alkylating agent trabectedin, which binds the minor groove of DNA, is second-line therapy for soft-tissue sarcoma but has only moderate efficacy. The aim of the present study was to determine the synergistic efficacy of recombinant methioninase (rMETase) and trabectedin on fibrosarcoma cells in vitro, compared with normal fibroblasts., Materials and Methods: HT1080 human fibrosarcoma cells expressing green fluorescent protein (GFP) in the nucleus and red fluorescent protein (RFP) in the cytoplasm and Hs27 normal human fibroblasts, were used. Each cell line was cultured in vitro and divided into four groups: no-treatment control; trabectedin treated; rMETase treated; and trabectedin plus rMETase treated. The dual-color HT1080 cells were used to quantitate nuclear fragmentation in each treatment group., Results: The combination of rMETase and trabectedin was highly synergistic to decrease HT1080 cell viability. In contrast, there was no synergy on Hs27 cells. Moreover, nuclear fragmentation occurred synergistically with the combination of trabectedin and rMETase on dual-color HT1080 cells., Conclusion: The combination treatment of trabectedin plus rMETase was highly synergistic on fibrosarcoma cells in vitro suggesting that the combination can improve the outcome of trabectedin alone in future clinical studies. The lack of synergy of rMETase and trabectedin on normal fibroblasts suggests the combination is not toxic to normal cells. Synergy of the two drugs may be due to the high rate of nuclear fragmentation on treated HT1080 cells, and the late-S/G 2 cell-cycle block of cancer cells by rMETase, which is a target for trabectedin. The results of the present study suggest the future clinical potential of the combination of rMETase and trabectedin for soft-tissue sarcoma., (Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Lactic acid bacteria (LAB) have excellent tolerance to the gastrointestinal environment and high adhesion ability to intestinal epithelial cells, which could be closely related to the LuxS/AI-2 Quorum sensing (QS) system. Here, the crucial enzymes involved in the synthesis of AI-2 was analyzed in Lacticaseibacillus paracasei S-NB, and the luxS deletion mutant was constructed by homologous recombination based on the Cre-lox system. Afterwards, the effect of luxS gene on the probiotic activities in L. paracasei S-NB was investigated. Notably, the tolerance of simulated gastrointestinal digestion, AI-2 production, ability of auto-aggregation and biofilm formation significantly decreased (p < 0.05 for all) in the S-NB△luxS mutant. Compared to the wild-type S-NB, the degree of reduction in the relative transcriptional level of the biofilm -related genes in Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was diminished when co-cultured with S-NB△luxS. Furthermore, the inhibitory effect of S-NB△luxS on the adhesion (competition, exclusion and displacement) of E. coli ATCC 25922 and S. aureus ATCC 25923 to Caco-2 cells markedly decreased. Therefore, comprehensive analysis of the role by luxS provides an insight into the LuxS/AI-2 QS system of L. paracasei S-NB in the regulation of strain characteristics and inhibition of pathogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Streptococcus suis (S. suis) regulates biofilm formation through LuxS/AI-2 quorum sensing system, increasing drug resistance and exacerbating infection. The anti-hyperglycaemic agent metformin has anti-bacterial and anti-biofilm activities. This study aimed to investigate the anti-biofilm and anti-quorum sensing activity of metformin in S. suis. We first determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of metformin on S. suis. The results indicated that metformin showed no obvious inhibitory or bactericidal effect. Crystal violet staining showed that metformin significantly inhibited the formation of S. suis biofilm at sub-MIC concentration, which was also confirmed by scanning electron microscopy. Then, we quantified the AI-2 signal molecules in S. suis, and the results showed that metformin had a significant inhibitory effect on the production of AI-2 signal in S. suis. Inhibition of enzyme activity and molecular docking experiments showed that metformin has a significant binding activity to LuxS protein. In addition, qRT-PCR results showed that metformin significantly down-regulated the expression of AI-2 synthesis-related genes luxS and pfs, and adhesion-related genes luxS, pfs, gapdh, sly, fbps, and ef. Western blotting also showed that metformin significantly reduced the expression of LuxS protein. Our study suggests that metformin seems to be a suitable candidate for the inhibition of S. suis LuxS/AI-2 QS system and prevention of biofilm formation, which provided a new idea for the prevention and control of S. suis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Aims: Vibrio parahaemolyticus is an important foodborne pathogen worldwide, which can cause gastroenteritis. This study aimed to investigate the effect of quorum sensing system LuxS/AI-2-related gene luxS on the biological characteristics and antimicrobial resistance of V. parahaemolyticus Vp2015094 from shellfish, which carried a multi-antimicrobial-resistant plasmid., Methods and Results: The critical gene luxS related to the synthesis of AI-2 in V. parahaemolyticus Vp2015094 was knocked out by homologous recombination with suicide plasmid. The effect of luxS on the biological characteristics of V. parahaemolyticus was determined by comparing the growth, AI-2 activity, motility, biofilm formation ability, and antibiotic resistance between the wildtype strain and the luxS deletion mutant. Compared with wildtype strain, the production of AI-2, the motility and biofilm formation ability, antimicrobial resistance, and conjugation frequency of luxS deletion mutant strain were decreased. The transcriptome sequencing showed that the transcriptional levels of many genes related to motility, biofilm formation, antimicrobial resistance, and conjugation were significantly downregulated after luxS deletion., Conclusions: Quorum sensing system LuxS/AI-2-related gene luxS in V. parahaemolyticus Vp2015094 played an important role in growth characteristics, biofilm formation, antimicrobial resistance, and resistance genes' transfer., (© The Author(s) 2023. Published by Oxford University Press on behalf of Applied Microbiology International.)

Ferroptosis is a major cause of cardiotoxicity induced by doxorubicin (DOX). Previous studies have shown that hydrogen sulfide (H 2 S) inhibits ferroptosis in cardiomyocytes and myoblasts, but the underlying mechanism has not been fully elucidated. In this study, we investigated the role of H 2 S in protecting against DOX-induced cardiotoxicity both in vivo and in vitro, and elucidated the potential mechanisms involved. We found that DOX downregulated the expression of glutathione peroxidase 4 (GPX4) and NFS1, and upregulated the expression of acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) expression level, resulting in increased lipid peroxidation and ferroptosis. Additionally, DOX inhibited MFN2 expression and increased DRP1 and FIS1 expression, leading to abnormal mitochondrial structure and function. In contrast, exogenous H 2 S inhibited DOX-induced ferroptosis by restoring GPX4 and NFS1 expression, and reducing lipid peroxidation in H9C2 cells. This effect was similar to that of the ferroptosis antagonist ferrostatin-1 (Fer-1) in protecting against DOX-induced cardiotoxicity. We further demonstrated that the protective effect of H 2 S was mediated by the key mitochondrial membrane protein optic atrophy 3 (OPA3), which was downregulated by DOX and restored by exogenous H 2 S. Overexpression of OPA3 alleviated DOX-induced mitochondrial dysfunction and ferroptosis both in vivo and in vitro. Mechanistically, NFS1 has an inhibitory effect on ferroptosis, and NFS1 deficiency increases the susceptibility of cardiomyocytes to ferroptosis. OPA3 is involved in the regulation of ferroptosis by interacting with NFS1. Post-translationally, DOX promoted OPA3 ubiquitination, while exogenous H 2 S antagonized OPA3 ubiquitination by promoting OPA3 s-sulfhydration. In summary, our findings suggested that H 2 S protects against DOX-induced cardiotoxicity by inhibiting ferroptosis via targeting the OPA3-NFS1 axis. This provides a potential therapeutic strategy for the treatment of DOX-induced cardiotoxicity., Competing Interests: Declaration of Competing Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023. Published by Elsevier Inc.)

Background/aim: The present study aimed to determine if oral methioninase (o-rMETase) combined with oxaliplatinum (OXA) plus 5-fluorouracil (5-FU) increases survival of mice with peritoneal-carcinomatosis formed from HCT-116 green fluorescent protein (GFP)-expressing colon-cancer cells implanted intra-peritoneally in nude mice., Materials and Methods: HCT-116-GFP human colon-cancer cells (2×10 6 ) were injected intraperitoneally in athymic nude mice. Forty-five HCT-116-GFP colon-cancer peritoneal-carcinomatosis nude-mouse models were divided into the following groups: untreated control; combination of 5-FU (50 mg/kg, once a week), plus OXA (6 mg/kg, once a week); combination of 5-FU + OXA + o-rMETase (100 unit/day). Tumor growth was followed weekly using non-invasive GFP imaging for 3 weeks. At necropsy, tumor tissue was obtained. Frozen sections were made for fluorescence imaging. Tumor tissues were also stained with hematoxylin and eosin. The date of death of all mice was recorded., Results: o-rMETase combined with 5-FU + OXA significantly reduced peritoneal growth of the HCT-116 tumor compared to the untreated control or the combination 5-FU and OXA group. Histological analysis revealed extensive necrosis induced by the o-rMETase + 5-FU + OXA combination. The combination of 5-FU plus OXA and o-rMETase achieved significantly longer survival of the mice with peritoneal carcinomatosis compared to the control or combination of 5-FU plus OXA treatments., Conclusion: o-rMETase shows future clinical promise for increasing the survival of patients with peritoneal metastasis of colon cancer when combined with first-line treatment of this recalcitrant disease., (Copyright © 2023 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Streptococcus suis LuxS/AI-2 quorum sensing system regulates biofilm formation, resulting in increased pathogenicity and drug resistance, and diminished efficacy of antibiotic treatment. The remaining peony seed cake after oil extraction is rich in monoterpenoid glycosides, which can inhibit the formation of bacterial biofilm. In this study, we investigated the effect of seven major monocomponents (suffruticosol A, suffruticosol B, suffruticosol C, paeonifloin, albiflorin, trans-ε-viniferin, gnetin H) of peony seed meal on minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of S. suis . The results showed that the MICs of the seven single components were all greater than 200 μg/mL, with no significant bacteriostatic and bactericidal advantages. Crystal violet staining and scanning electron microscope observation showed that the seven single components had a certain inhibitory effect on the biofilm formation ability of S. suis at sub-MIC concentration. Among them, the ability of paeoniflorin to inhibit biofilm was significantly higher than that of the other six single components. AI-2 signaling molecules were detected by bioreporter strain Vibrio harvey BB170 . The detection results of AI-2 signal molecules found that at 1/2 MIC concentration, paeoniflorin significantly inhibited the production of S. suis AI-2 signal, and the inhibitory effect was better than that of the other six single components. In addition, molecular docking analysis revealed that paeoniflorin had a significant binding activity with LuxS protein compared with the other six single components. The present study provides evidence that paeoniflorin plays a key role in the regulation of the inhibition of S. suis LuxS/AI-2 system and biofilm formation in peony seed meal., Competing Interests: The authors declare no conflict of interest.

Background/aim: Primary osteosarcoma of the breast is a very rare malignancy that shares histological features with osteosarcoma. It is also highly sensitive to methionine restriction due to methionine addiction. We previously established a patient-derived orthotopic xenograft (PDOX) nude-mouse model derived from tumor tissue of a patient with primary mammary osteosarcoma. In the present study, we investigated the efficacy of oral-recombinant methioninase (o-rMETase), combined with rapamycin, an inhibitor of mammalian target of rapamycin (mTOR) kinase, on a mammary osteosarcoma PDOX nude-mouse model., Materials and Methods: The PDOX mouse model was established by surgically transplanting a specimen of primary osteosarcoma of the breast into the mammary gland of nude mice. Mice implanted with tumors were randomly divided into four groups: Control group, N=5; rapamycin-treated group, N=5; o-rMETase-treated group, N=5; and a group treated with the combination of o-rMETase and rapamycin, N=5. Mice were treated for 2 weeks after transplantation, and tumor volume was measured during the treatment period., Results: Treatment with the combination of rapamycin and o-rMETase eradicated the osteosarcoma of the breast compared to the untreated control (p=0.000008). o-rMETase alone did not significantly inhibit tumor growth, and rapamycin alone only partially inhibited the tumor (p=0.78 and p=0.018, respectively) compared to the untreated control. There was not a significant difference in mouse weight between the groups., Conclusion: The combination of rapamycin and o-rMETase was highly effective against primary osteosarcoma of the breast in a PDOX model, suggesting a future clinical strategy for this rare cancer type that currently has no first-line treatment., (Copyright © 2022 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: All cancer types so far tested are methionine-addicted. Targeting the methionine addiction of cancer with recombinant methioninase (rMETase) has shown great progress in vitro, in mouse models, and in the clinic. However, administration of rMETase requires multiple doses per day. In the present study, we determined if rMETase-producing Escherichia coli JM109 (E. coli JM109-rMETase) might be an effective anticancer agent when installed into the microbiome., Materials and Methods: E. coli JM109-rMETase was administered to a syngeneic model of MC38 colon cancer growing subcutaneously in C57BL/6 mice. JM109-rMETase was administered orally by gavage to the mice twice per day. Tumor size was measured with calipers., Results: The administration of E. coli JM109-rMETase twice a day significantly inhibited MC38 colon-cancer growth. E. coli JM109-rMETase was found in the stool of treated mice, indicating it had entered the microbiome., Conclusion: The present study indicates the potential of microbiome-based treatment of cancer targeting methionine addiction., (Copyright © 2022, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Methionine addiction is a fundamental and general hallmark of cancer, termed the Hoffman effect. Methionine addiction is due to excessive use of and dependence on methionine by cancer cells. In the present report, we correlated the extent of methionine addiction and degree of malignancy with the amount and stability of methylated histone H3 lysine marks., Materials and Methods: We established low- and high-malignancy variants from a parental human pancreatic-cancer cell line and compared their sensitivity to methionine restriction and histone H3 lysine methylation status., Results: A low-malignancy, low-methionine-addiction revertant of the parental pancreatic-cancer cell line had less methylated H3K9me3 and was less sensitive to methionine restriction effected by recombinant methioninase (rMETase) than the parental cell line. A high-malignancy variant of the pancreatic cancer cell line had increased methylated H3K9me3 and was more sensitive to methionine restriction by rMETase with regard to inhibition of proliferation and to instability of histone H3 lysine methylation than the parental cell line. Orthotopic malignancy in nude mice was reduced in the low-methionine-addiction revertant and greater in the high-malignancy variant than in the parental cell line., Conclusion: The present study indicates that the degree of malignancy is linked to the extent of methionine addiction and the level and instability of trimethylation of histone H3, suggesting these phenomena are linked as a fundamental basis of oncogenic transformation., (Copyright © 2022, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Streptococcus suis ( S. suis ), more specifically serotype 2, is a bacterial pathogen that threatens the lives of pigs and humans. Like many other pathogens, S. suis exhibits quorum sensing (QS) system-controlled virulence factors, such as biofilm formation that complicates treatment. Therefore, impairing the QS involving LuxS/AI-2 cycle in S. suis , may be a promising alternative strategy for overcoming S. suis infections. In this study, we investigated paeoniflorin (PF), a monoterpenoid glycoside compound extracted from peony, as an inhibitor of S. suis LuxS/AI-2 system. At a sub-minimal inhibitory concentration (MIC) (1/16 MIC; 25 μg/ml), PF significantly reduced biofilm formation by S. suis through inhibition of extracellular polysaccharide (EPS) production, without affecting bacterial growth. Moreover, evidence was brought that PF reduces AI-2 activity in S. suis biofilm. Molecular docking indicated that LuxS may be the target of PF. Monitoring LuxS enzymatic activity confirmed that PF had a partial inhibitory effect. Finally, we showed that the use of PF in a mouse model can relieve S. suis infections. This study highlighted the anti-biofilm potential of PF against S. suis , and brought evidence that it may as an inhibitor of the LuxS/AI-2 system to prevent S. suis biofilm-related infections. PF can thus be used as a new type of natural biofilm inhibitor for clinical application.

The methionine dependence is a well known phenomenon in metabolism of cancer cells. Methionine γ-lyase (EC 4.4.1.11, MGL) catalyzes the γ-elimination reaction of L-methionine and thus could effectively inhibit the growth of malignant cells. Recently we have demonstrated that the mutant form of the enzyme C115H MGL can be used as a component of the pharmacological pair enzyme/S-(allyl/alkyl)-L-cysteine sulfoxides to yield thiosulfinates in situ. Thiosulfinates were shown to be toxic to various cancer cell lines. Therefore the application of the enzyme in enzyme pro-drug therapy may be promising. The conjugates of MGL and C115H MGL with polysialic acid were obtained and their kinetic and pharmacokinetic parameters were determined. The formation of polysialic shell around the enzyme was confirmed by atomic force microscopy. The half-life of conjugated enzymes increased 3-6 times compared to the native enzyme. The cytotoxic effect of conjugated MGL against methionine dependent cancer cell lines was increased two times compared to the values for the native enzymes. The anticancer efficiency of thiosulfinates produced by pharmacological pair C115H MGL/S-(allyl/alkyl)-L-cysteine sulfoxides was demonstrated in vitro. The results indicate that the conjugates of MGL with polysialic acid could be new antitumor drugs., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Purpose: Advanced ovarian clear cell carcinoma (OCCC) is a recalcitrant disease, often resistant to the first-line platinum-based therapy. Using a novel patient-derived orthotopic xenograft (PDOX) nude-mouse model of OCCC, we tested whether oral-recombinant methioninase (o-rMETase) could enhance the efficacy of paclitaxel (PTX)., Methods: The OCCC PDOX model was established and passaged in nude mice. The OCCC PDOX models were randomized into 5 groups. G1: untreated control; G2: paclitaxel (PTX) (20 mg/kg, intraperitoneal (i.p.) injection, weekly); G3: o-rMETase (100 units, oral, daily); G4: PTX (20 mg/kg, i.p. injection, weekly) + carboplatinum (CBDCA) (40 mg/kg, i.p. injection weekly); G5: PTX (20 mg/kg, i.p. injection, weekly) + o-rMETase (100 units, oral, daily). The treatment period was 2 weeks., Results: The combination of PTX and o-rMETase arrested OCCC tumor growth (relative tumor volume: 1.09 ± 0.63 (mean ± SD)) compared with the untreated control (relative tumor volume: 3.92 ± 1.04 (mean ± SD)) (p < 0.0001). There was no significant difference in relative tumor volume between PTX plus o-rMETase and PTX plus CBDCA (relative tumor volume: 1.39 ± 0.37 (mean ± SD)) (p = 0.93)., Conclusion: PTX plus o-rMETase arrested the OCCC tumor growth. o-rMETase is readily administered and can greatly enhance first-line therapy of a recalcitrant cancer. The novel and effective treatment strategy in the present report has future clinical potential for patients with OCCC, especially for patients who cannot well tolerate platinum-based therapy.

Background/aims: Targeted drug delivery vehicles with low immunogenicity and toxicity are needed for cancer therapy. Here, we prepare an active targeting drug carrier of low immunogenicity and toxicity for targeted therapy., Methods: Immature dendritic cells (imDCs) from BALB/c mice were used as donor cells of exosomes (Exos) that were transfected with the plasmids expressing fusion proteins of a tumor-targeting peptide known as internalizing RGD (iRGD) to construct a type of tumor-targeting iRGD-Exos and observe the interaction between these iRGD-Exos. Also, recombinant methioninase (rMETase) was loaded into the iRGD-Exos by electroporation to construct iRGD-Exos-rMETase and to assess the tumor-targeting function of the iRGD-Exos-rMETase. Finally, 30 BALB/c were randomly divided into five groups (n = 6), to observe tumor growth in vivo., Results: The iRGD-Exos-rMETase was 99.58 nm in diameter and presented a unique "goblet" structure under transmission electron microscopy (TEM), with the encapsulation efficiency (EE) of 19.05%. iRGD-Exos-rMETase group has the strongest tumor suppressive effect. Compared to the iRGD-Exos-rMETase group, rMETase group and the blank-Exos-rMETase group were less effective, while the PBS group and the iRGD-Exos group showed no inhibitory effect on tumor growth. After treatment, the iRGD-Exos-rMETase group had gastric tumors significantly smaller and lighter than the other groups (P < 0.05)., Conclusion: The iRGD-Exos-rMETase is an effective antitumor therapy that delivers rMETase to tumor tissue using the iRGD-Exos. With its favorable inhibitory effect and tumor-targeting function, the iRGD-Exos-rMETase shows excellent potential value and exciting prospects in clinical applications.

Objectives: Methionine addiction is a fundamental and general hallmark of cancer caused by enhanced methyl flux. In the present study, we effected a novel methionine-methylation blockade to target a patient-derived orthotopic xenograft model of pancreatic cancer., Methods: The pancreatic cancer patient-derived orthotopic xenograft mouse models were randomized into 6 groups of 8 mice each and treated for 2 weeks: untreated control; azacitidine; oral recombinant methioninase (o-rMETase); o-rMETase plus cycloleucine; o-rMETase plus cycloleucine plus azacitidine (triple-methyl blockade therapy); and gemcitabine (positive control)., Results: Triple-methyl blockade therapy arrested tumor growth (mean relative tumor volume, 1.03 [standard deviation, 0.36]) and was significantly more effective compared with azacitidine (P = 0.0001); o-rMETase (P = 0.007); or o-rMETase plus cycloleucine (P = 0.04). Gemcitabine alone also inhibited but did not arrest tumor growth (mean relative tumor volume, 1.50 [standard deviation, 0.30]). The percentage of cancer cells that were negative for 5-methylcytosine staining in immunohistochemistry, indicating reduction of DNA methylation, increased with triple-methyl blockade therapy (37.5%), compared with gemcitabine (1.8%); o-rMETase (2.8%); azacitidine (9.0%); or o-rMETase plus cycloleucine (10.6%)., Conclusions: This new concept of triple-methyl blockade therapy has clinical potential for pancreatic cancer, which is currently a recalcitrant disease., Competing Interests: The authors declare no conflicts of interest. AntiCancer, Inc uses patient-derived orthotopic xenograft models for contract research. Q.H. and Y.T. are employees of AntiCancer, Inc. N.S., J.Y., Y.T., H.N., S.I., K.H., and R.M.H. are or were unsalaried associates of AntiCancer, Inc., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

ABP 798 is a proposed biosimilar to rituximab reference product (RP), an anti-CD20 monoclonal antibody. Pharmacokinetics (PK), pharmacodynamics (PD), and safety results from the comparative clinical study that evaluated the PK, PD, safety, efficacy, and immunogenicity of ABP 798 versus rituximab RP are presented here. Subjects with moderate to severe rheumatoid arthritis (RA) received 2 doses of ABP 798, United States-sourced RP (rituximab US) or European Union-sourced RP (rituximab EU), each consisting of two 1000-mg infusions 2 weeks apart. For the second dose (week 24), ABP 798- and rituximab EU-treated subjects received the same treatment; rituximab US-treated subjects transitioned to ABP 798. End points included area under the serum concentration-time curve from time 0 extrapolated to infinity and maximum observed serum concentration following the second infusion of the first dose (PK) and percentage of subjects with complete CD19+ cell depletion days 1-33 (PD). Primary analysis established PK similarity between ABP 798 and rituximab RP based on 90% confidence intervals of the adjusted geometric mean ratios being within a prespecified equivalence margin of 0.8 and 1.25. Complete CD19+ B-cell depletion on day 3 among groups confirmed PD similarity. These findings demonstrated PK/PD similarity between ABP 798 and rituximab RP in subjects with moderate to severe RA., (© 2020 The Authors. Clinical Pharmacology in Drug Development published by Wiley Periodicals LLC on behalf of American College of Clinical Pharmacology.)

Background/aim: The aim of the study was to determine if oral recombinant methioninase (o-rMETase) can sensitize an orthotopic bladder tumor in nude mice to low-dose cisplatinum (CDDP)., Materials and Methods: The green fluorescent protein (GFP)-expressing UM-UC-3-GFP bladder cancer was surgically orthotopically implanted (SOI) to the bladder in nude mice. The treatment was initiated when the primary tumor volume reached 100 mm 3 Mice were assigned to 3 groups: G1: Saline vehicle (0.1 ml per mouse, oral, twice per day); G2: low-dose CDDP (0.5 mg/kg, intraperitoneal twice per week); G3: o-rMETase + low-dose CDDP (100 units per mouse, oral, twice per day + 0.5 mg/kg, intraperitoneal twice per week, respectively). Tumor volume and body weight were measured twice per week. The expression of Ki-67 was detected by immunohistochemistry to evaluate cell proliferation., Results: The combination of o-rMETase and low-dose CDDP increased inhibition efficacy compared to low-dose CDDP monotherapy, on primary-tumor growth (p=0.032) and metastasis (p=0.002)., Conclusion: The combination of o-rMETase with low-dose CDDP has future clinical potential for bladder cancer., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Methionine addiction is a general and fundamental hallmark of cancer. Methionine addiction can be targeted by methionine restriction (MR). Our laboratory has studied methionine addiction in cancer and MR for almost 50 years. The present study describes oral recombinant methioninase (o-rMETase), as a supplement, to induce MR in cancer patients., Patients and Methods: One patient, a 67-year-old female with high-stage ovarian cancer took o-rMETase twice a day at 250 units per dose for approximately one month. A second patient, a 76-year-old male with bone-metastatic prostate cancer, took o-rMETase twice a day at 250 units per dose during three months., Results: The first patient's circulating methionine levels decreased 50% within 4 hours of taking 250 units of o-rMETase. The second patient's PSA dropped approximately 70% over 3 months. During this time the patient's hemoglobin increased., Conclusion: o-rMETase has no side effects and is potentially efficacious. Future studies involving larger cohorts of patients with high-stage cancer are required to determine if o-rMETase, as a supplement, can increase survival and improve the quality of life., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Dedifferentiated liposarcoma (DDLPS) is associated with a poor survival rate even with multi-modality treatment. In the present study, we evaluated the efficacy of recombinant methioninase (rMETase) combined with tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R against a doxorubicin-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) mouse model., Materials and Methods: A recurrent high-grade DDLPS from the right retroperitoneum of a patient was grown orthotopically in the retroperitoneum of nude mice to establish a PDOX model. The PDOX models were randomly divided into the following groups: Control, no treatment; doxorubicin monotherapy; rMETase monotherapy; S. typhimurium A1-R monotherapy; S. typhimurium A1-R and rMETase combination therapy. Tumor length and width were measured before and after treatment., Results: On day 14 after treatment, all treatments significantly inhibited DDLPS PDOX tumor growth compared to the untreated control except for doxorubicin monotherapy. rMETase combined with S. typhimurium A1-R was significantly more effective and regressed tumor volume compared to either rMETase or S. typhimurium A1-R alone. The relative body weight did not significantly differ between days 0 and 14 for individual groups., Conclusion: The combination of rMETase and S. typhimurium A1-R has important clinical potential for this recalcitrant sarcoma., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Purpose: Cancers are methionine (MET) and methylation addicted, causing them to be highly sensitive to MET restriction. The present study determined the efficacy of restricting MET with oral-recombinant methioninase (o-rMETase) and the DNA methylation inhibitor, azacitidine (AZA) on a chemotherapy-resistant osteosarcoma patient-derived orthotopic xenograft (PDOX) mouse model., Methods: The osteosarcoma PDOX models were randomized into five treatment groups of six mice: control; doxorubicin (DOX) alone; AZA alone; o-rMETase alone; o-rMETase-AZA combination. Tumor size and body weight were measured during the 14 days of treatment., Results: We found that tumor growth was arrested only by the o-rMETase-AZA combination treatment, as tumors with this treatment exhibited tumor necrosis with degenerative change., Conclusion: This study suggests that o-rMETase-AZA combination has clinical potential for patients with chemoresistant osteosarcoma.

Objective: To investigate the molecular mechanism of recombinant methioninase (rMETase) in promoting apoptosis of gastric cancer cells., Methods: Gastric cancer SGC-7901 cells were treated with rMETase (final concentration of 1.25 and 2.50 mmmol/L) for 72 h, and the changes in the cell viability were detected using CCK-8 method and the cell morphology changes were observed under an inverted microscope. Plate colony formation assay was used to evaluate colony formation ability of the cells, and flow cytometry was performed to analyze the changes in cell apoptosis and cell cycles. Glucose and lactate levels in the culture medium were determined using a colorimetric method and ATP concentration was detected using a fluorescence microplate reader; Western blotting was used to assess the effect of rMETase on PI3K/Akt pathway, glucose transporter-1 (GLUT-1), glycolysis- related proteins and apoptotic proteins in SGC-7901 cells., Results: rMETase significantly inhibited the proliferation and clonal formation, promoted cell apoptosis, and induced cell cycle arrest in S phase in SGC-7901 cells ( P < 0.05). With the increase of rMETase concentration, the cells showed obviously decreased glucose intake accompanied by decreased glycolysis and ATP concentration ( P < 0.001). The results of Western blotting showed that the expressions of PI3K, p-Akt/t-Akt, GLUT-1, and the key glycolytic enzymes HK2, PFKM, LDHA, antiapoptosis protein Bcl-2 were all downregulated and the pro-apoptotic proteins Bax and caspase-3 were up-regulated in response to rMETase treatment in SGC-7901 cells ( P < 0.01)., Conclusions: rMETase can inhibit aerobic glycolysis, induce apoptosis and inhibit the proliferation of SGC-7901 cells by inhibiting the activity of PI3K/Akt/GLUT-1 pathway, suggesting its potential as a therapeutic agent for gastric cancer.

Citrobacter freundii methionine γ-lyase (MGL), in addition to the physiological reaction, catalyzes the β-elimination reaction of S-alk(en)yl-L-cysteine sulfoxides to yield thiosulfinates, which have antibacterial activity. We have obtained the mutant form C115H MGL, which cleaves S-alk(en)yl-L-cysteine sulfoxides more effectively than the wild type enzyme does. The binary system MGL/S-alk(en)yl-L-cysteine sulfoxides may be considered as a new pharmacological pair in enzyme prodrug therapy (EPT). Despite of the successful application of this pair in antibacterial studies in vitro, in vivo experiments may lead to several problems typical of therapeutic proteins including a relatively short-lasting biological activity. To circumvent these problems, we have investigated several approaches to improve safety and efficacy of the enzyme component of the pharmacological pair. This included covalent attachment of poly(ethylene glycol) to the enzyme, its encapsulation in liposomes and polymeric vesicles (PICsomes). The steady-state and pharmacokinetic parameters of modified/encapsulated enzyme were determined. It was demonstrated that the encapsulation in PICsomes prolongs in vivo stability of C115H MGL to over 42 h compared to PEGylated enzyme (3 h). Antibacterial activity of binary system ("pharmacological pair") modified/encapsulated enzyme/S-alk(en)yl-L-cysteine sulfoxides was tested and remained the same as for the naked enzyme. Thus, the usage of MGL-loaded PICsomes as enzymatic nanoreactors in ETP to produce antimicrobial thiosulfinates is promising., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Methionine deprivation induces growth arrest and death of cancer cells. To eliminate l-methionine we produced, purified, and characterized the recombinant pyridoxal 5'-phosphate (PLP)-dependent l-methionine γ -lyase (MGL)- BL929 from the cheese-ripening Brevibacterium aurantiacum Transformation of an Escherichia coli strain with the gene BL929 from B. aurantiacum optimized for E. coli expression led to production of the MGL-BL929. Elimination of l-methionine and cytotoxicity in vitro were assessed, and methylation-sensitive epigenetics was explored for changes resulting from exposure of cancer cells to the enzyme. A bioreactor was built by encapsulation of the protein in human erythrocytes to achieve sustained elimination of l-methionine in extracellular fluids. Catalysis was limited to α , γ -elimination of l-methionine and l-homocysteine. The enzyme had no activity on other sulfur-containing amino acids. Enzyme activity decreased in presence of serum albumin or plasma resulting from reduction of PLP availability. Elimination of l-methionine induced cytotoxicity on a vast panel of human cancer cell lines and spared normal cells. Exposure of colorectal carcinoma cells to the MGL-BL929 reduced methyl-CpG levels of hypermethylated gene promoters including that of CDKN2A, whose mRNA expression was increased, together with a decrease in global histone H3 dimethyl lysine 9. The MGL-erythrocyte bioreactor durably preserves enzyme activity in vitro and strongly eliminates l-methionine from medium., (Copyright © 2019 by The American Society for Pharmacology and Experimental Therapeutics.)

Cancer cells are methionine (MET) dependent compared to normal cells as they have an elevated requirement for MET in order to proliferate. MET restriction selectively traps cancer cells in the S/G 2 phase of the cell cycle. The cell cycle phase can be visualized by color coding with the fluorescence ubiquitination-based cell cycle indicator (FUCCI). Recombinant methioninase (rMETase) is an enzyme that effectively degrades MET. rMETase induces S/G 2 -phase blockage of cancer cells which is identified by the cancer cells' green fluorescence with FUCCI imaging. Cancer cells in G 1 /G 0 are the majority of the cells in solid tumors and are resistant to the chemotherapy. Treatment of cancer cells with standard chemotherapy drugs only led to the majority of the cancer cell population being arrested in G 0 /G 1 phase, identified by the cancer cells' red fluorescence in the FUCCI system. The G 0 /G 1 -phase cancer cells are chemo-resistant. Tumor targeting Salmonella typhimurium A1-R (S. typhimurium A1-R) was used to decoy quiescent G 0 /G 1 stomach cancer cells growing in nude mice to cycle, with subsequent rMETase treatment to selectively trap the decoyed cancer cells in S/G 2 phase, which made them highly sensitive to chemotherapy. Subsequent cisplatinum (CDDP) or paclitaxel (PTX) chemotherapy was then administered to kill the decoyed and trapped cancer cells, which completely prevented or regressed tumor growth. In a subsequent experiment, a patient-derived orthotopic xenograft (PDOX) model of recurrent CDDP-resistant metastatic osteosarcoma was eradicated by the combination of Salmonella typhimurium A1-R decoy, rMETase S/G 2 -phase cell cycle trap, and CDDP cell kill. Salmonella typhimurium A1-R and rMETase pre-treatment thereby overcame CDDP resistance. These results demonstrate the effectiveness of the new chemotherapy paradigm of "decoy, trap, and kill" chemotherapy.

The elevated methionine (MET) requirement of cancer cells is termed MET dependence and is possibly the only known general metabolic defect in cancer. Targeting MET by recombinant methioninase (rMETase) can arrest the growth of cancer cells in vitro and in vivo due to their elevated requirement for MET. rMETase can also potentiate chemotherapy drugs active in S phase due to the selective arrest of cancer cells in S/G 2 phase during MET restriction (MR). We previously reported that rMETase, administrated by intraperitoneal injection (ip-rMETase), could inhibit tumor growth in mouse models of cancer including patient-derived orthotopic xenograft (PDOX) mouse models. We subsequently compared ip-rMETase and oral rMETase (o-rMETase) on a melanoma PDOX mouse model. o-rMETase was significantly more effective than ip-rMETase to inhibit tumor growth without overt toxicity. The combination of o-rMETase+ip-rMETase was significantly more effective than either monotherapy and completely arrested tumor growth. Thus, o-rMETase is effective as an anticancer agent with the potential of clinical development for chronic cancer therapy as well as for cancer prevention. o-rMETase may also have potential as an antiaging agent for healthy people, since MR has been shown to extend the life span of a variety of different organisms.

Methionine (MET) is a general target in cancer due to the excess requirement of MET by cancer cells. MET has been effectively restricted by recombinant methioninase (rMETase) in mouse models of cell-line tumors. This chapter reviews the efficacy of rMETase on patient-derived orthotopic xenograft (PDOX) mouse models of human cancer. Ewing's sarcoma is a recalcitrant disease even though development of multimodal therapy has improved patients' outcome. A Ewing's sarcoma was implanted in the right chest wall of nude mice to establish a PDOX model. rMETase effectively reduced tumor growth compared to the untreated control. The MET level both of plasma and supernatants derived from sonicated tumors was lower in the rMETase treatment group. Body weight did not significantly differ at any time points between the two groups. A PDOX nude mouse model of a BRAF V600E-mutant melanoma was established in the chest wall of nude mice and also tested with rMETase in combination with a first-line melanoma drug, temozolomide (TEM). Combination therapy of TEM and rMETase was significantly more efficacious than either monotherapy. The results reviewed in this chapter demonstrate the clinical potential of rMETase.

This chapter reviews the effect of methionine (MET) restriction, via treatment with recombinant methioninase (rMETase), on DNA methylation of cancer cells. CCRF-CEM human cancer cells were treated with rMETase under subcytotoxic conditions. The rMETase-treated cells contained significantly lower levels of genomic methylated DNA than did untreated control cells. DNA methylation was measured by incorporation of the methyl group of [ 3 H]methyl-S-adenosylmethionine into DNA and by methylation-sensitive arbitrarily-primed PCR. DNA hypomethylation effected by rMETase was of similar extent to that effected by treatment of the cells with the DNA methyltransferase inhibitor 5-azacytidine.

Liposarcoma is the most common type of soft tissue sarcoma. Among the subtypes of liposarcoma, dedifferentiated liposarcoma (DDLPS) is recalcitrant and has the lowest survival rate. The aim of the present study is to determine the efficacy of metabolic targeting with recombinant methioninase (rMETase) combined with palbociclib (PAL) against a doxorubicin (DOX)-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) model. A resected tumor from a patient with recurrent high-grade DDLPS in the right retroperitoneum was grown orthotopically in the right retroperitoneum of nude mice to establish a PDOX model. The PDOX models were randomized into the following groups when tumor volume reached 100 mm 3 : G1, control without treatment; G2, DOX; G3, PAL; G4, recombinant methioninase (rMETase); G5, PAL combined with rMETase. Tumor length and width were measured both pre- and post-treatment. On day 14 after initiation, all treatments significantly inhibited tumor growth compared to the untreated control except DOX. PAL combined with rMETase was significantly more effective than both DOX, rMETase alone, and PAL alone. Combining PAL and rMETase significantly regressed tumor volume on day 14 after initiation of treatment and was the only treatment to do so. The relative body weight on day 14 compared with day 0 did not significantly differ between each treatment group. The results of the present study indicate the powerful combination of rMETase and PAL should be tested clinically against DDLPS in the near future., (Published by Elsevier Inc.)

Pancreatic cancer is a recalcitrant disease. Gemcitabine (GEM) is the most widely-used first-line therapy for pancreatic cancer, but most patients eventually fail. Transformative therapy is necessary to significantly improve the outcome of pancreatic cancer patients. Tumors have an elevated requirement for methionine and are susceptible to methionine restriction. The present study used a patient-derived orthotopic xenograft (PDOX) nude mouse model of pancreatic cancer to determine the efficacy of recombinant methioninase (rMETase) to effect methionine restriction and thereby overcome GEM-resistance. A pancreatic cancer obtained from a patient was grown orthotopically in the pancreatic tail of nude mice to establish the PDOX model. Five weeks after implantation, 40 pancreatic cancer PDOX mouse models were randomized into four groups of 10 mice each: untreated control (n = 10); GEM (100 mg/kg, i.p., once a week for 5 weeks, n = 10); rMETase (100 units, i.p., 14 consecutive days, n = 10); GEM+rMETase (GEM: 100 mg/kg, i.p., once a week for 5 weeks, rMETase: 100 units, i.p., 14 consecutive days, n = 10). Although GEM partially inhibited PDOX tumor growth, combination therapy (GEM+rMETase) was significantly more effective than mono therapy (GEM: p = 0.0025, rMETase: p = 0.0010). The present study is the first demonstrating the efficacy of rMETase combination therapy in a pancreatic cancer PDOX model to overcome first-line therapy resistance in this recalcitrant disease.

The elevated methionine (MET) use by cancer cells is termed MET dependence and may be the only known general metabolic defect in cancer. Targeting MET by recombinant methioninase (rMETase) can arrest the growth of cancer cells in vitro and in vivo. We previously reported that rMETase, administrated by intra-peritoneal injection (ip-rMETase), could inhibit tumor growth in a patient-derived orthotopic xenograft (PDOX) model of a BRAF-V600E mutant melanoma. In the present study, we compared ip-rMETase and oral rMETase (o-rMETase) for efficacy on the melanoma PDOX. Melanoma PDOX nude mice were randomized into four groups of 5 mice each: untreated control; ip-rMETase (100 units, i.p., 14 consecutive days); o-rMETase (100 units, p.o., 14 consecutive days); o-rMETase+ip-rMETase (100 units, p.o.+100 units, i.p., 14 consecutive days). All treatments inhibited tumor growth on day 14 after treatment initiation, compared to untreated control (ip-rMETase, p<0.0001; o-rMETase, p<0.0001; o-rMETase+ip-rMETase, p<0.0001). o-rMETase was significantly more effective than ip-rMETase (p = 0.0086). o-rMETase+ip-rMETase was significantly more effective than either mono-therapy: ip-rMETase, p = 0.0005; or o-rMETase, p = 0.0367. The present study is the first demonstrating that o-rMETase is effective as an anticancer agent. The results of the present study indicate the potential of clinical development of o-rMETase as an agent for chronic cancer therapy and for cancer prevention and possibly for life extension since dietary MET reduction extends life span in many animal models.

The exploitation of methionine-depleting enzyme methionine γ-lyase (MGL) is a promising strategy against specific cancer cells that are strongly dependent on methionine. To identify MGL from different sources with high catalytic activity and efficient anticancer action, we have expressed and characterized MGL from Clostridium novyi and compared its catalytic efficiency with the previously studied MGL from Citrobacter freundii. The purified recombinant MGL exhibits k cat and k cat /K m for methionine γ-elimination reaction that are 2.4- and 1.36-fold higher than C. freundii enzyme, respectively, whereas absorption, fluorescence, and circular dichroism spectra are very similar, as expected on the basis of 87% sequence identity and high conservation of active site residues. The reactivity of cysteine residues with DTNB and iodoacetamide was investigated as well as the impact of their chemical modification on catalytic activity. This information is relevant because for increasing bioavailability and reducing immunogenity, MGL should be decorated with polyethylene glycol (PEG). It was found that Cys118 is a faster reacting residue, which results in a significant decrease in the γ-elimination activity. Thus, the protection of Cys118 before conjugation with cysteine-reacting PEG represents a valuable strategy to preserve MGL activity. The anticancer action of C. novyi MGL, evaluated in vitro against prostate (PC-3), chronic myelogenous leucemia (K562), and breast (MDA-MB-231 and MCF7) cancer cells, exhibits IC 50 of 1.3 U mL -1 , 4.4 U mL -1 , 1.2 U mL -1 , and 3.4 U mL -1 , respectively. A higher cytotoxicity of C. novyi MGL was found against cancer cells with respect to C. freundii MGL, with the exception of PC-3, where a lower cytotoxicity was observed. © 2017 IUBMB Life, 69(9):668-676, 2017., (© 2017 International Union of Biochemistry and Molecular Biology.)

Methionine dependence is due to the overuse of methionine for aberrant transmethylation reactions in cancer. Methionine dependence may be the only general metabolic defect in cancer. In order to exploit methionine dependence for therapy, our laboratory previously cloned L-methionine α-deamino-γ-mercaptomethane lyase [EC 4.4.1.11]). The cloned methioninase, termed recombinant methioninase, or rMETase, has been tested in mouse models of human cancer cell lines. Ewing's sarcoma is recalcitrant disease even though development of multimodal therapy has improved patients'outcome. Here we report efficacy of rMETase against Ewing's sarcoma in a patient-derived orthotopic xenograft (PDOX) model. The Ewing's sarcoma was implanted in the right chest wall of nude mice to establish a PDOX model. Eight Ewing's sarcoma PDOX mice were randomized into untreated control group (n = 4) and rMETase treatment group (n = 4). rMETase (100 units) was injected intraperitoneally (i.p.) every 24 hours for 14 consecutive days. All mice were sacrificed on day-15, 24 hours after the last rMETase administration. rMETase effectively reduced tumor growth compared to untreated control. The methionine level both of plasma and supernatants derived from sonicated tumors was lower in the rMETase group. Body weight did not significantly differ at any time points between the 2 groups. The present study is the first demonstrating rMETase efficacy in a PDOX model, suggesting potential clinical development, especially in recalcitrant cancers such as Ewing's sarcoma.

l-Methionine γ-lyase (MGL), a pyridoxal 5'-phosphate-dependent enzyme, possesses anti-tumor activity. However, the low activity of MGL blocks the anti-tumor effect. This study describes an efficient production process for the recombinant MGL (rMGL) from Idiomarina constructed using the overexpression plasmid in Escherichia coli BL21 (DE3), purification, and large-scale production. The enzyme produced by the transformants accounted for 53% of the total proteins and accumulated at 1.95 mg/mL using a 500 L fermentor. The enzyme was purified to approximately 99% purity using a high-pressure mechanical homogenizer and nickel (Ni) Sepharose 6 Fast Flow (FF) chromatography. Then, the enzyme was polished by gel filtration, the endotoxins were removed using diethyl-aminoethanol (DEAE) Sepharose FF, and the final product was lyophilized with a vacuum freeze dryer at -35 °C. The specific activity of rMGL in the lyophilized powder was up to 108 U/mg. Compared to the control, the enzyme significantly inhibited cellular proliferation in a concentration-dependent manner as tested using the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and induced cellular apoptosis as analyzed by Annexin V-fluorescein isothiocyanate (FITC) with fluorescence-activated cell sorting (FACS) in leukemia cells. This paper demonstrated the cloning, overexpression, and large-scale production protocols for rMGL, which enabled rMGL to be used as a novel anti-leukemic drug.

Background: Enzyme prodrug therapy shows promise for the treatment of solid tumors, but current approaches lack effective/safe delivery strategies. To address this, we previously developed three enzyme-containing fusion proteins targeted via annexin V to phosphatidylserine exposed on the tumor vasculature and tumor cells, using the enzymes L-methioninase, purine nucleoside phosphorylase, or cytosine deaminase. In enzyme prodrug therapy, the fusion protein is allowed to bind to the tumor before a nontoxic drug precursor, a prodrug, is introduced. Upon interaction of the prodrug with the bound enzyme, an anticancer compound is formed, but only in the direct vicinity of the tumor, thereby mitigating the risk of side effects while creating high intratumoral drug concentrations. The applicability of these enzyme prodrug systems to treating prostate cancer has remained unexplored. Additionally, target availability may increase with the addition of low dose docetaxel treatment to the enzyme prodrug treatment, but this effect has not been previously investigated. To this end, we examined the binding strength and the cytotoxic efficacy (with and without docetaxel treatment) of these enzyme prodrug systems on the human prostate cancer cell line PC-3., Results: All three fusion proteins exhibited strong binding; dissociation constants were 0.572 nM for L-methioninase-annexin V (MT-AV), 0.406 nM for purine nucleoside phosphorylase-annexin V (PNP-AV), and 0.061 nM for cytosine deaminase-annexin V (CD-AV). MT-AV produced up to 99% cell death (p < 0.001) with limited cytotoxicity of the prodrug alone. PNP-AV with docetaxel created up to 78% cell death (p < 0.001) with no cytotoxicity of the prodrug alone. CD-AV with docetaxel displayed up to 60% cell death (p < 0.001) with no cytotoxicity of the prodrug alone. Docetaxel treatment created significant increases in cytotoxicity for PNP-AV and CD-AV., Conclusions: Strong binding of fusion proteins to the prostate cancer cells and effective cell killing suggest that the enzyme prodrug systems with MT-AV and PNP-AV may be effective treatment options. Additionally, low-dose docetaxel treatment was found to increase the cytotoxic effect of the annexin V-targeted therapeutics for the PNP-AV and CD-AV systems.

Aspergillus flavipes L-methioninase (AfMETase) exhibits reliable pharmacokinetic properties and anticancer potency in vitro[10]. To maximize its therapeutic efficiency as protection against in vivo proteolysis, reduction of antigenicity and hyperammoniemia, the enzyme was PEGylated and coupled with glutamate dehydrogenase (GDH). The highest degree of PEGylation was measured at 40-50/1 molar ratio of PEG to AfMETase, with a lower mobility on SDS-PGE, compared to the native AfMETase. The activity of free AfMETase was reduced to 66.2% and further to 50% upon PEGylation and GDH conjugation, respectively. The highest degree of surface NH2 modification of AfMETase-GDH co-immobilizates (65%), was reported using 300 mM glutaraldehyde, with 31% methionine conversion. Using L-cysteine and L-methionine as active site protectors, the activity of PEG-AfMETase and PEG-AfMETase-GDH was increased by 14.4 and 32.9-fold, respectively. At 45°C, PEG-AfMETase, PEG-AfMETase-GDH and AfMETase-GDH conjugate have a T1/2 10.3, 8.5 and 7.6 h, inactivation rate (Kr) 0.021, 0.03 and 0.016 min, with 2.0, 1.65 and 1.47-fold stabilization, respectively. Kinetically, the three immobilizates have a relatively similar Km values for L-methionine (7.4-7.9 mM), with lower affinity to homocysteine and cysteine, with stability to PLP-enzyme inhibitors (propargylglycine and hydroxylamine), indicating the protective effect by PEG moieties on the enzyme structure. Also, the three immobilizates exhibited improved stability against proteolysis in vitro, comparing to free AfMETase., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Methionine starvation can powerfully modulate DNA methylation, cell cycle transition, polyamines and antioxidant synthesis of tumor cells, in contrary to normal ones. Aspergillus flavipesl-methioninase was previously characterized by our studies, displaying affordable biochemical properties comparing to Pseudomonas putida enzyme (ONCASE). Thus, the objective of current study was to evaluate the catalytic properties of Af-METase in New Zealand rabbits, exploring its antitumor efficacy. In vivo, Af-METase (40.8 U/ml) have T(1/2) 19.8 h, elimination constant 0.088 U/h and apparent volume distribution 85 U/ml. Also, Af-METase has two maxima one at A(280 nm) (apo-enzyme) and at A(420 nm) (internal Schiff base of PLP), unlike control plasma (without enzyme). The two peaks of absorption spectra were detected maximally at 15 min then the absorbance at 420 nm was subsequently decreased with circulation time, due to dissociation of the co-enzyme. The A₂₈₀/₄₂₀ ratio was increased from 1.69 to 5.81 with circulation time from 15 to 30 h. Rabbits plasma methionine was depleted from 18.7 μM (control) to 8.8 μM after 1h of enzyme injection and completely omitted after 2 h till 19 h, assuming the sustainability of negligible levels of methionine (< 2 μM) in plasma of rabbits, for about 17 h. Upon infusion of PLP, the T(½) of Af-METase was significantly prolonged by 3.2 fold, assuming the fully reconstitution of the enzyme. The holo-AfMETase still retained its co-enzyme, completely, till 33 h of PLP infusion. From spectral studies, the internal aldimine linkage of apo-Af-METase was constructed upon PLP infusion, with fully catalytic structure after less than 4h of its infusion, the A₂₈₀/₄₂₀ ratio being not relatively changed till 45 h. After 25 days of last enzyme dose, the titer of IgG was increase by about 1.66 fold comparing to control (without enzyme). However, IgM was not detected along the tested challenge points. In vitro, plasma anti-Af-METase neutralizing antibodies (NAb) were assessed, with no significant reduction on activity of Af-METase by Nab. All the hematological parameters were in normal range, otherwise, the RBCs titer and platelet level was slightly increased, after 25 days of Af-METase injection, comparing to control. There is no obvious negative effect on chemistry of liver, kidney, glucose, lipids, and other electrolytes. Additionally, the anticancer activity of Af-METase was evaluated against five types of human cancer cell lines, in vitro. The enzyme showed a powerful activity against prostate (PC3), liver (HEPG2) and breast (MCF7) cancers, with IC₅₀ 0.001 U/ml, 0.26 U/ml and 0.37 U/ml, respectively., (Published by Elsevier Inc.)

Human ovarian cancer cells specifically bind the isoflavone daidzein. A chemical conjugate between daidzein and the garlic enzyme alliinase was prepared. The conjugate specifically bound to ovarian cancer cells and upon addition of the prodrug alliin, it effectively produced cytotoxic allicin molecules which killed the cancer cells. In vivo targeting and antitumor effect was confirmed by NIR and bioluminescence imaging using daidzein-alliinase-CyTE-777 conjugates and luciferase-expressing ovarian cancer cells. Co-localization of the fluorescent conjugate with bioluminescence was observed for intraperitoneal tumors while nonconjugated alliinase did not accumulate. Biodistribution studies with Europium-labeled conjugate revealed a five fold higher uptake in tumors as compared to other tissues. Treatment of tumor bearing mice with daidzein-alliinase and alliin effectively attenuated tumor progression during the first 12 days while a 5-fold increase in bioluminescence was detected in placebo-treated animals. Autopsy revealed only small individual foci of luminescence at the site of tumor cells inoculation. Histological examination of organs and tissues did not reveal any additional foci of carcinoma or signs of toxicity. These results suggest that the targeted alliinase conjugates in the presence of alliin, generated therapeutically effective levels of allicin which were capable of suppressing tumor progression of intraperitoneal ovarian cancer in an animal model.

Elevated dependence on methionine of cancer cells is a cancer-specific metabolic defect. Recombinant L-methionine alpha,gamma-lyase (rMETase), an L-methionine depleting enzyme cloned from Pseudomonas putida, was shown to have efficacy on a broad series of cancer cell lines. Twenty-one different human tumor cell lines (4 lung, 4 colon, 4 kidney, 4 melanoma, 3 CNS, and 2 prostate) from the NCI Human Tumor Cell Line Screen and 7 human normal cell strains were treated with rMETase in vitro. We showed that rMETase had a mean IC(50) (units rMETase/ml) for the following cancer cell types: renal, 0.07; colon, 0.04; lung, 0.12; prostate, 0.01; melanoma, 0.19; and CNS, 0.195, which was approximately one order of magnitude lower than that for normal cell strains: skin fibroblasts, 4; aortic smooth muscle cells, 0.88; aortic endothelial cells, 0.8; keratinocytes, 0.75; and bronchial epithelial cells, 0.75. rMETase was also conjugated with polyethylene glycol (PEG). PEG-rMETase also had high cancer cell-killing activity. In vitro studies, animal studies and clinical trials have now shown that methionine restriction is an effective anticancer strategy. Cells from many different types of cancer are methionine dependent. The most effective strategy to deplete methionine is with the use of rMETase. PEG-rMETase offers additional advantages of increasing the circulating half-life and reducing the immunogenicity of rMETase which is a bacterial protein. The results of the current study demonstrate the broad clinical potential for rMETase and PEG-rMETase for cancer treatment.

The elevated dependence on methionine of tumor cells is a cancer-specific metabolic defect. In current studies, the recombinant L-methionine alpha,gamma-lyase (rMETase), an L-methionine depleting enzyme cloned from Pseudomonas putida, was shown to have efficacy in a broad series of cancer cell lines. Twenty-one different human tumor cell lines (4 lung, 4 colon, 4 kidney, 4 melanoma, 3 CNS, and 2 prostate) from the NCI Human Tumor Cell Line Screen and 7 human normal cell strains were treated with rMETase in vitro. We showed that rMETase had mean IC(50) (units rMETase/ml) for the following cancer cell types: renal cancer, 0.07; colon cancer, 0.04; lung cancer, 0.12; prostate cancer, 0.01; melanoma, 0.19; and CNS cancer, 0.195, which was approximately one order of magnitude lower than that for normal cell strains: skin fibroblasts, 4; aortic smooth muscle cells, 0.88; aortic endothelial cells, 0.8; keratinocytes, 0.75, and bronchial epithelial cells, 0.75. rMETase was also conjugated with polyethylene lycol (PEG). PEG-rMETase also had high cell-kill activity. In vitro studies, animal studies and clinical trials have now shown that methionine restriction is an effective anticancer strategy. Cells from many different types of cancers are methionine dependent. The most effective strategy to deplete methionine is with the use of rMETase. PEG-rMETase offeres additional advantages of increasing the circulating half-life and reducing the immunogenicity of rMETase which is a bacterial protein. The results of the current study demonstrate the broad clinical potential for rMETase and rMETase for cancer treatment.

Background: Previously, we reported that a novel fusion protein consisting of an amino-terminal fragment of urokinase linked to the amino terminus of the enzyme L-methioninase inhibited MCF-7 breast cancer cells in vitro to a greater extent than treatment with L-methioninase., Materials and Methods: The fusion protein, L-methioninase and a mutated fusion protein without L-methioninase activity were produced by recombinant methods. The effects of fusion protein, L-methioninase, and mutated fusion protein treatment on the proliferation and motility of SK-LU-i lung and PC-3 prostate and cancer cells were measured in vitro using a culture wounding assay., Results: The fusion protein produced a dose-dependent inhibition of the proliferation and motility of both cancer cell lines. In addition, the fusion protein was found to be significantly more effective than L-methioninase alone or mutated fusion protein., Conclusion: Our results suggest that this fusion protein has potential as a selective therapeutic agent for the treatment of various methionine-dependent cancers.

Melanoma is a highly metastatic cancer resistant to current chemotherapeutic and radiotherapeutic approaches. Several studies have shown that interactions between cancer cells and the extracellular matrix (ECM) are critical for the survival and invasion of metastatic cancer cells. In this study, we examine the effects of methylselenol generated from selenomethionine (SeMet) by methioninase (METase) on cell proliferation, adhesion, and expression of integrins in murine melanoma B16F10 cells, which are metastatic in the lungs of syngeneic C57BL/6J mice. Combined treatment with SeMet-METase decreased the expression of integrins alpha(4), beta(1), alpha(nu), and beta(3), and inhibited melanoma-ECM adhesion. Caspase-mediated apoptosis was induced following loss of cell adherence. Phosphorylation of focal adhesion kinase (FAK) and Akt, related to integrin-mediated survival, were decreased upon treatment with SeMet-METase while phosphorylation of p38, PKC-delta, and IkappaBalpha increased. In the presence of specific inhibitors of p38, PKC-delta, and NF-kappaB, expression of integrins and cell adhesion to ECM were maintained and cell apoptosis was prevented in SeMet-METase-treated melanoma cells. Treatment with caspase inhibitors restored cell viability and blocked poly (ADP-ribose) polymerase (PARP) cleavage, but did not restore integrin expression and cell adhesion to ECMs reduced by SeMet-METase. Based on these results, we propose that combined treatment with SeMet-METase induces caspase-mediated apoptosis in melanoma cells by altering integrin expression and adhesion. Furthermore, activation of p38, PKC-delta, and NF-kappaB is a prerequisite for the down-regulation of integrin expression, followed by detachment-mediated apoptosis.