Search

New selective, efficacious chemotherapy agents are in demand as traditional drugs display side effects and face growing resistance upon continued administration. To this end, bioactive molecules such as peptides are attracting interest. RT2 is a cationic peptide that was used as an antimicrobial but is being repurposed for targeting cancer. In this work, we investigate the mechanism by which this peptide targets Caco-2 human colon cancer cells, one of the most prevalent and metastatic cancers. Combining label-free proteomics with bioinformatics data, our data explore over 1000 proteins to identify 133 proteins that are downregulated and 79 proteins that are upregulated upon treatment with RT2. These changes occur in a dose-dependent manner and suggest the former group are related to anticancer cell proliferation; the latter group is closely related to apoptosis levels. The mRNA levels of several genes (FGF8, PAPSS2, CDK12, LDHA, PRKCSH, CSE1L, STARD13, TLE3, and OGDHL) were quantified using RT-qPCR and were found to be in agreement with proteomic results. Collectively, the global change in Caco-2 cell protein abundance suggests that RT2 triggers multiple mechanisms, including cell proliferation reduction, apoptosis activation, and alteration of cancerous cell metabolism.

A comparative study of human colon HCT-116 xenograft in nude mice treated with and without peptide RT2 at high doses is performed along with a label-free proteomic analysis of the tissue in order to understand the potential mechanisms by which RT2 acts in vivo against colorectal tumors. RT2 displays no significant systematic toxicity, but reduces tumor growth after either intraperitoneal or intratumoral injection demonstrating it is a safe and efficacious antitumor agent in vivo. Of the 3196 proteins identified by label-free proteomics, 61 proteins appear only in response to RT2 and are involved in cellular processes largely localized in the cells and cell parts. Some of the proteins identified, including CFTR, Wnt7a, TIA1, PADI2, NRBP2, GADL1, LZIC, TLR6, and GPR37, have been reported to suppress tumor growth and are associated with cell proliferation, invasion, metastasis, angiogenesis, apoptosis, and immune evasion. Our work supports their role as tumor biomarkers and reveals RT2 has a complex mechanism of action in vivo., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Background/aim: Many antimicrobial peptides have been shown to have anticancer activity against human cancer cell lines. Cationic KT2 peptide, derived from white blood cell extract of Crocodylus siamensis has antibacterial activity and antitumor activity against human cervical cancer cells, but there are no data on the effect of KT2 peptide on tumor growth in vivo. The anticancer activity of KT2 peptide on human colon cancer xenografts was investigated in nude mice., Materials and Methods: Tumors in nude mice (BALB/c -nu/nu mice) were induced by subcutaneous injection with HCT116 cells. Twelve days after cancer cell xenograft, mice were treated by intratumoral injection with phosphate-buffered saline or KT2 peptide (25 and 50 mg/kg) once every 2 days for a total of four times and mice were sacrificed at 2 days after the last treatment., Results: KT2 peptide treatment did not lead to significant difference in mouse body weight among groups, but reduced both tumor volume and weight of colon cancer xenografts. Moreover, KT2 peptide increased the expression of apoptotic proteins, such as BCL2-associated X (BAX), cleaved caspase-3, and poly (ADP-ribose) polymerase and reduced that of BCL2 apoptosis regulator in xenograft tumors., Conclusion: This finding suggests that KT2 peptide may inhibit tumor growth via apoptosis induction in this mouse model and supports the antitumor ability of KT2 peptide., (Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

RT2, derived from the leukocyte peptide of Crocodylus siamensis, can kill human cervical cancer cells via apoptosis induction, but no evidence has shown in vivo. In this study, we investigated the antitumor effect of RT2 on human colon cancer xenografts in nude mice. Twenty-four mice were injected subcutaneously with human colon cancer HCT 116 cells. Eleven days after cancer cell implantation, the mice were treated with intratumoral injections of phosphate buffered saline (PBS) or RT2 (0.01, 0.1, and 1 mg/mouse) once every 2 days for a total of 5 times. The effect of a 10-day intratumoral injection of RT2 on body weight, biochemical, and hematological parameters in BALB/c mice showed no significant difference between the groups. Tumor volume showed a significant decrease only in the treatment group with RT2 (1 mg/mouse) at day 6 (P < .05), day 8 (P < .01), and day 10 (P < .01) after the first treatment. The protein expression levels of cleaved poly (ADP-ribose) polymerase (PARP), apoptosis-inducing factor (AIF), and the p53 tumor suppressor protein (p53) in xenograft tumors increased after treatment with RT2 (1 mg/mouse) compared to those in the PBS-injected group. Moreover, RT2 increased the expression of Endo G and Bcl-2 family proteins. Therefore, the peptide RT2 can inhibit tumor growth via the induction of apoptosis in an in vivo xenograft model., (© 2018 Wiley Periodicals, Inc.)

Conventional colon cancer treatments have been associated with side effects. Consequently, the discovery of novel effective and safe therapies is urgently needed. Hence, cationic antimicrobial peptides KT2 and RT2 were evaluated towards human colon cancer HCT-116 cells. The MTT assay indicated that both KT2 and RT2 exhibited anticancer activity with good therapeutic indices, and were found to be non-toxic to non-cancerous Vero cells. The IC 50 values of KT2 were determined as 111.96 and 90.25 μg/mL while RT2 showed IC 50 as 104.07 and 87.84 μg/mL after 12 and 24 h treatments, respectively. Moreover, KT2 and RT2 treatment caused a significant reduction in PI3K, AKT1 and mTOR mRNA expression levels, which resulted in suppression either of HCT-116 proliferation or migration. The mechanism involved in apoptosis induction were due to decreased Bcl-2 and XIAP and increased p53, cytochrome c, caspase-2, caspase-3, caspase-8, and caspase-9 mRNA expression levels. These effects increased the level of cell cycle associated gene p21 and decreased cyclin B1 and cyclin D1 expression., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Cancer represents one of the most significant threats to human health on a global scale. Hence, the development of effective cancer prevention strategies, as well as the discovery of novel therapeutic agents against cancer, is urgently required. In light of this challenge, this research aimed to evaluate the effects of several potent bioactive peptides and proteins contained in crocodile white blood cell extract (cWBC) against LU-1, LNCaP, PC-3, MCF-7, and CaCo-2 cancer cell lines. The results demonstrate that 25, 50, 100, and 200 μg/ml cWBC exhibits a strong cytotoxic effect against all investigated cell lines (IC₅₀ 70.34-101.0 μg/ml), while showing no signs of cytotoxicity towards noncancerous Vero and HaCaT cells. Specifically, cWBC treatment caused a significant reduction in the cancerous cells' colony forming ability. A remarkable suppression of cancerous cell migration was observed after treatment with cWBC, indicating potent antimetastatic properties. The mechanism involved in the cancer cell cytotoxicity of cWBC may be related to apoptosis induction, as evidenced by typical apoptotic morphology features. Moreover, certain cWBC concentrations induced significant overproduction of ROS and significantly inhibited the S-G₂/M transition in the cancer cell. The molecular mechanisms of cWBC in apoptosis induction were to decrease Bcl-2 and XIAP expression levels and increase the expression levels of caspase-3, caspase-8, and p53. These led to a decrease in the expression level of the cell cycle-associated gene cyclin-B1 and the arrest of cell population growth. Consequently, these findings demonstrate the prospect of the use of cWBC for cancer therapy.

The plasma and serum of Crocodylus siamensis have previously been reported to exhibit potent antimicrobial, antioxidant, and anti-inflammatory activities. During wound healing, these biological properties play a crucial role for supporting the formation of new tissue around the injured skin in the recovery process. Thus, this study aimed to evaluate the wound healing properties of C. siamensis plasma and serum. The collected data demonstrate that crocodile plasma and serum were able to activate in vitro proliferation and migration of HaCaT, a human keratinocyte cell line, which represents an essential phase in the wound healing process. With respect to investigating cell migration, a scratch wound experiment was performed which revealed the ability of plasma and serum to decrease the gap of wounds in a dose-dependent manner. Consistent with the in vitro results, remarkably enhanced wound repair was also observed in a mouse excisional skin wound model after treatment with plasma or serum. The effects of C. siamensis plasma and serum on wound healing were further elucidated by treating wound infections by Staphylococcus aureus ATCC 25923 on mice skin coupled with a histological method. The results indicate that crocodile plasma and serum promote the prevention of wound infection and boost the re-epithelialization necessary for the formation of new skin. Therefore, this work represents the first study to demonstrate the efficiency of C. siamensis plasma and serum with respect to their wound healing properties and strongly supports the utilization of C. siamensis plasma and serum as therapeutic products for injured skin treatment.

Known antimicrobial peptides KT2 and RT2 as well as the novel RP9 derived from the leukocyte extract of the freshwater crocodile (Crocodylus siamensis) were used to evaluate the ability in killing human cervical cancer cells. RP9 in the extract was purified by a combination of anion exchange column and reversed-phase HPLC, and its sequence was analyzed by mass spectrometry. The novel peptide could inhibit Gram-negative Vibrio cholerae (clinical isolation) and Gram-positive Bacillus pumilus TISTR 905, and its MIC values were 61.2 µM. From scanning electron microscopy, the peptide was seen to affect bacterial surfaces directly. KT2 and RT2, which are designed antimicrobial peptides using the C. siamensis Leucrocin I template, as well as RP9 were chemically synthesized for investigation of anticancer activity. By Sulforhodamine B colorimetric assay, these antimicrobial peptides could inhibit both HeLa and CaSki cancer cell lines. The IC50 values of KT2 and RT2 for HeLa and CaSki cells showed 28.7-53.4 and 17.3-30.8 µM, while those of RP9 were 126.2 and 168.3 µM, respectively. Additionally, the best candidate peptides KT2 and RT2 were used to determine the apoptotic induction on cancer cells by human apoptosis array assay. As a result, KT2 and RT2 were observed to induce apoptotic cell death in HeLa cells. Therefore, these results indicate that KT2 and RT2 with antimicrobial activity have a highly potent ability to kill human cervical cancer cells.

Hemoglobin (Hb) is an important component in red blood cells of the vertebrate. It is a major respiratory protein with oxygen or carbon dioxide transport function. Hb has been reported to contain bioactive peptides which have antibacterial and antioxidant activities. In this study, the alpha-chain hemoglobin(αHb) gene of Crocodylus siamensis was cloned into the three different expression vectors and expressed in Escherichia coli BL21 (DE3). The recombinant αHb proteins from all constructs could be expressed and purified. The result from UV-visible absorption spectra showed a similar pattern of all recombinant proteins to the oxy-hemoglobin form of intact Hb. The different recombinant αHb could exhibit antioxidant activities. All recombinant proteins could inhibit the growth of Bacillus spp. Especially, most of the recombinant proteins could inhibit the growth of Bacillus amyloliquefaciens TISTR 1045 better than intact one. The result obtained from this study can provide us further information about the possibility using of αHb as a supplementary food., (Copyright © 2015 Elsevier Inc. All rights reserved.)