Search

Background/aimCancers are selectively sensitive to methionine (MET) restriction (MR) due to their addiction to MET which is overused for elevated methylation reactions. MET addiction of cancer was discovered by us 45 years ago. MR of cancer results in depletion of S-adenosylmethionine (SAM) for transmethylation reactions, resulting in selective cancer-growth arrest in the late S/G2-phase of the cell cycle. The aim of the present study was to determine if blockade of the MET-methylation axis is a highly-effective strategy for cancer chemotherapy.Materials and methodsIn the present study, we demonstrated the efficacy of MET-methylation-axis blockade using MR by oral-recombinant methioninase (o-rMETase) combined with decitabine (DAC), an inhibitor of DNA methylation, and an inhibitor of SAM synthesis, cycloleucine (CL). We determined a proof-of-concept of the efficacy of the MET-methylation-axis blockade on a recalcitrant undifferentiated/unclassified soft-tissue sarcoma (USTS) patient-derived orthotopic xenograft (PDOX) mouse model.ResultsThe o-rMETase-CL-DAC combination regressed the USTS PDOX with extensive cancer necrosis.ConclusionThe new concept of combination MET-methylation-axis blockade is effective and can now be tested on many types of recalcitrant cancer.

Bone is one of the most frequent metastatic sites in non-small cell lung cancer (NSCLC). Osimertinib, with and without bevacizumab (BV), has been investigated on advanced NSCLC patients. However, the efficacy of those drugs on bone metastasis of NSCLC has not been investigated. The human NSCLC cell line H1975, expressing red fluorescent protein (H1975-RFP), was orthotopically injected to the tibia of nude mice. The established mouse models were randomized into four treatment groups of nine mice: Control; BV alone; osimertinib alone; osimertinib and BV combination. The tumors were observed by non-invasive fluorescence imaging. Osimertinib, with or without BV, caused tumor regression, increased mouse survival, and bone remodeling in the bone metastasis models. These results suggest that osimertinib is a promising clinical option for NSCLS patients with bone metastasis.

Adult pleomorphic rhabdomyosarcoma (RMS) is a rare and malignant mesenchymal tumor. Recently, we developed a patient-derived orthotopic xenograft (PDOX) model of adult pleomorphic RMS. In the present study, we evaluated the efficacy of tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R combined with caffeine (CAF) and valproic acid (VPA) on the adult RMS PDOX. An adult pleomorphic RMS cell line was established from the PDOX model. Cell survival after exposure to CAF and VPA was assessed, and the IC50 value was calculated for each drug. The RMS PDOX models were randomized into five groups: untreated control; tumor treated with cyclophosphamide (CPA); tumor treated with CAF + VPA; tumor treated with S. typhimurium A1-R; and tumor treated with S. typhimurium A1-R + CAF + VPA. Tumor size and body weight was measured twice a week. VPA caused a concentration-dependent cytocidal effect. A synergistic effect of combination treatment with CAF was observed against the RMS cell line. For the in vivo study, all treatments significantly inhibited tumor growth compared with the untreated control. S. typhimurium A1-R combined with VPA and CAF was significantly more effective than CPA, VPA combined with CAF, or S. typhimurium A1-R alone and significantly regressed the tumor volume compared with day 0. These results suggest that S. typhimurium A1-R together with VPA and CAF could regresses an adult pleomorphic RMS in a PDOX model and therefore has important future clinical potential.

BACKGROUND/AIM:Cisplatinum (CDDP) is a first-line drug in osteosarcoma treatment and the acquisition of resistance to CDDP is associated with a poor prognosis. Peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear hormone receptor that plays important roles in cell proliferation, differentiation, development, metabolism and cell death. Recently, PPARγ was reported to enhance the efficacy, overcome resistance, and decrease the toxicity of CDDP in various human cancers. In this study we tested whether pioglitazone (PIO), a PPARγ agonist, could overcome CDDP resistance in osteosarcoma. MATERIALS AND METHODS:In this study, we used a human osteosarcoma cell line and a patient-derived orthotopic xenograft (PDOX) models of osteosarcoma. We measured cell viability of 143B human osteosarcoma cells when treated with CDDP and PIO. We randomized PDOX models of osteosarcoma into four treatment groups: Group 1, Untreated control; Group 2, PIO alone; Group 3, CDDP alone; Group 4, a combination of CDDP and PIO. Each group comprised six mice. Mice were treated for 14 days and tumor size and body weight were measured. RESULTS:Cell viability of 143B human osteosarcoma cells was significantly reduced when PIO (50 μmol/l) was combined with CDDP compared to CDDP alone. PDOX osteosarcoma tumors treated with the CDDP-PIO combination showed the strongest tumor growth inhibition compared to other treatment groups. PDOX osteosarcoma tumors treated with the CDDP-PIO combination had the least cancer cells and the most necrosis in histological section. CONCLUSION:These results suggest that combining PIO along with CDDP could be an effective treatment strategy for osteosarcoma and has important clinical potential for patients.

Background/aimBrain metastases are found in approximately 30% of patients with epidermal-growth-factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC). We compared the efficacy of two EGFR-tyrosine kinase inhibitors (TKIs), erlotinib and osimertinib on a PC-9-GFP EGFR mutant NSCLC growing in the brain of nude mice.Materials and methodsThe brain metastasis models were randomized into five groups and treated for 15 days: Control; 5 mg/kg erlotinib; 50 mg/kg erlotinib; 0.5 mg/kg osimertinib; 5 mg/kg osimertinib. Tumor volume was evaluated by non-invasive fluorescence imaging.ResultsOnly 5 mg/kg osimertinib, a low-dose compared to the clinically-equivalent dose, showed significant tumor regression compared to the control.ConclusionThis study strongly supports the high activity of osimertinib for intracranial lesions of EGFR-mutant NSCLC.

BACKGROUND/AIM:We have previously developed a novel bone-targeting platinum compound, 3Pt, and showed that it has strong inhibitory activity against osteosarcoma cells and orthotopic cell-line xenograft mouse models. In the present report, we compared the efficacy of 3Pt to cisplatinum (CDDP) in a CDDP-resistant relapsed osteosarcoma patient-derived orthotopic xenograft (PDOX) mouse model. PATIENTS AND METHODS:The tumor of a patient with osteosarcoma of the distal femur was treated with CDDP-based chemotherapy followed by surgery. The surgical specimen was used to establish a PDOX model. An osteosarcoma cell line was also established from the original patient tumor. Osteosarcoma cell viability was assessed with the WST-8 assay and the IC50 values were calculated. The PDOX models were randomized into three groups: untreated control, CDDP-treated group, and 3Pt-treated group. Tumor size and body weight were measured twice a week. RESULTS:3Pt had a strong concentration-dependent cytocidal effect in vitro. The IC50 value of 3Pt was significantly lower than that of CDDP. On day 14 of the treatment, 3Pt caused a significantly greater tumor growth inhibition compared to the untreated control and CDDP-treated mice. CONCLUSION:3Pt is a promising clinical candidate for the treatment of recalcitrant osteosarcoma.

Background/aimDedifferentiated liposarcoma (DDLPS) is recalcitrant type of sarcoma. DDLPS has a low survival rate with high recurrence and metastasis. In the present study, we evaluated the efficacy of several drugs against doxorubicin-resistant DDLPS in a patient-derived orthotopic xenograft (PDOX) model for precision oncology. To establish the PDOX model, a tumor from a patient who had recurrent high-grade DDLPS from the retroperitoneum was previously grown orthotopically in the retroperitoneum of nude mice.Materials and methodsWe randomized DDLPS PDOX models into 8 treatment groups when tumor volume became approximately 100 mm3: control, no treatment; G2, doxorubicin (DOX); G3, pazopanib (PAZ); G4, gemcitabine (GEM) combined with docetaxel (DOC); G5, trabectedin (YON); G6, temozolomide (TEM); G7, palbociclib (PAL); G8, eribulin (ERB). Tumor length and width were measured both at the beginning and at the end of treatment.ResultsAt the end of treatment (day 14), all treatments significantly inhibited DDLPS PDOX tumor growth compared to the untreated control, except DOX. ERB was significantly more effective and regressed tumor volume compared to other treatments on day 14 after initiation of treatment. No significant differences were found in the relative body weight on day 14 compared to day 0 in any group.ConclusionThe clinical potential of ERB against DDLPS is herein presented in a PDOX model.

Ischemia reperfusion injury (IRI) during liver-metastasis resection for treatment of colon cancer may increase the risk of further metastasis. Peroxisome proliferator-activated receptor-γ (PPARγ) activation has been observed to exert a protective effect against IRI and IRI-induced metastasis of hepatocellular carcinoma. The present study aimed to investigate the effect of the PPARγ agonist pioglitazone on tumor metastasis and liver injury following IRI in a mouse model of colon cancer. Pioglitazone (30 mg/kg weight) was administered orally 1.5 h before and 2 h after the initiation of ischemia and was orally administrated daily to mice from day 0-21. SL4-cancer cells expressing red fluorescent protein (SL4-RFP) (1 × 106) were injected into the spleen. Fifteen minutes after injection, the hepatoduodenal ligament was clamped with a vessel clip, and released 5 min later. Liver, blood and tumor samples were taken from mice in order to determine if inflammation was induced by IRI. The effect of pioglitazone on liver metastasis was assessed. Furthermore, the effect of pioglitazone to control the inflammatory response during IRI progression was examined. Liver metastasis along with MMP-9 activation and the production of inflammatory cytokines were resistant to pioglitazone. Our results indicate that liver metastasis and associated inflammation in mice were resistant to pioglitazone.

Liver metastasis is a recalcitrant disease that usually leads to death of the patient. The present study established a unique patient-derived orthotopic xenograft (PDOX) nude mouse model of a highly aggressive liver metastasis of colon cancer. The aim of the present study was to demonstrate proof-of-concept that candidate drug combinations could significantly inhibit growth and re-metastasis of this recalcitrant tumor. The patient's liver metastasis was initially established subcutaneously in nude mice and the subcutaneous tumor tissue was then orthotopically implanted in the liver of nude mice to establish a PDOX model. Two studies were performed to test different drugs or drug combination, indicating that 5-fluorouracil (5-FU) + irinotecan (IRI) + bevacizumab (BEV) and regorafenib (REG) + selumetinib (SEL) had significantly inhibited liver metastasis growth (p = 0.013 and p = 0.035, respectively), and prevented liver satellite metastasis. This study is proof of concept that a PDOX model of highly aggressive colon-cancer metastasis can identify effective drug combinations and that the model has future clinical potential.

Chemotherapy-resistant osteosarcoma is a recalcitrant disease. It is a frequent cause of death to the patients who are usually adolescent or young adults. The goal of the present study was to determine the efficacy of the combination of olaratumab (OLA), doxorubicin (DOX), and cisplatinum (CDDP) on osteosarcoma, which is resistant to first-line therapy, in a patient-derived orthotopic xenograft (PDOX) model. The osteosarcoma PDOX model was randomized into six treatment groups of six mice: control; CDDP alone; DOX and CDDP; OLA + DOX; OLA + CDDP; and OLA + DOX and CDDP. Tumor size and body weight were measured during 14 days of treatment. Tumor growth was regressed only by the treatment with a combination of OLA + DOX and CDDP. Tumors treated with this three-drug combination had the most tumor necrosis and the lowest Ki-67 index. The present study demonstrates the power of the PDOX model to identify novel effective treatment strategy for chemotherapy-resistant osteosarcoma.

The goal of the present study was to determine the efficacy of osimertinib (AZD9291), a third-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor for the treatment of aggressive EGFR-mutant non-small cell lung cancer (NSCLC), compared to cisplatinum (CDDP) + pemetrexed (PEM). The NSCLC cell line PC-9 expressing green fluorescence protein (PC-9-GFP) was implanted in the brain of nude mice and was treated with CDDP + PEM or AZD9291. Tumors were observed by non-invasive fluorescence imaging. AZD9291 treatment caused tumor regression in contrast to CDDP + PEM which had only a slight inhibitory effect. These results suggest that AZD9291 is a promising clinical option for NSCLC patients with brain metastasis.

Pleomorphic liposarcoma (PLPS) is a recalcitrant soft-tissue sarcoma (STS) subtype in need of transformative therapy. We have previously established a patient-derived orthotopic xenograft (PDOX) model, of PLPS with PDGFRA amplification, using surgical orthotopic implantation. In the current study, the PLPS PDOX model was randomized into 3 groups of 7 mice each: untreated control; doxorubicin (DOX)-treated; and treated with Salmonella typhimurium A1-R (S. typhimurium A1-R) expressing green fluorescent protein (GFP). Tumor volume and body weight were monitored during the treatment period. The PLPS PDOX was resistant to DOX. In contrast, the PLPS PDOX was highly sensitive to S. typhimurium A1-R. There was no significant body-weight loss among these 3 groups. Fluorescence imaging demonstrated that S. typhimurium A1-R-GFP was very effective to target the PLPS PDOX tumor. The current study demonstrates that a PLPS PDOX, resistant to first-line therapy DOX, was highly sensitive to tumor targeting S. typhimurium A1-R.

Synovial sarcoma (SS) is a recalcitrant subgroup of soft tissue sarcoma (STS). A tumor from a patient with high grade SS from a lower extremity was grown orthotopically in the right biceps femoris muscle of nude mice to establish a patient-derived orthotopic xenograft (PDOX) mouse model. The PDOX mice were randomized into the following groups when tumor volume reached approximately 100 mm3: G1, control without treatment; G2, doxorubicin (DOX) (3 mg/kg, intraperitoneal [i.p.] injection, weekly, for 2 weeks; G3, rMETase (100 unit/mouse, i.p., daily, for 2 weeks); G4 DOX (3mg/kg), i.p. weekly, for 2 weeks) combined with rMETase (100 unit/mouse, i.p., daily, for 2 weeks). On day 14 after treatment initiation, all therapies significantly inhibited tumor growth compared to untreated control, except DOX: (DOX: p = 0.48; rMETase: p < 0.005; DOX combined with rMETase < 0.0001). DOX combined with rMETase was significantly more effective than both DOX alone (p < 0.001) and rMETase alone (p < 0.05). The relative body weight on day 14 compared with day 0 did not significantly differ between any treatment group or untreated control. The results indicate that r-METase can overcome DOX-resistance in this recalcitrant disease.

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.