No abstract

It is common knowledge that some natural antimicrobial peptides also have a tumoricidal effect. We have shown that the peptides defensin and cathelicidin LL37 have cytostatic effects on human tumor cell lines HT29 (colorectal carcinoma) and A549 (alveolar carcinoma). In order to determine the modulating mechanism of these peptides we assessed the gene expression of the AKT, HIF-1α, XBP, NRF2, PERK, CHOP, BCL2, IRE1α and PI3K molecular targets involved in the survival, growth, proliferation and apoptosis pathways of tumor cells in the presence or absence of the studied peptides. Thus, this research enabled us to determine molecular markers and methods of assessment and monitoring of tumor cell cytotoxicity by high-performance molecular biology techniques. Defensin and cathelicidin LL37 activated tumor cell apoptosis, especially for the HT29, but also for A549 line, by increasing gene expression of CHOP and by lowering BCL2 gene expression. Oxidative stress determined the increase in gene expression of XBP, which directly influenced CHOP. The decrease in NRF2 gene expression highlighted the inhibition of cell proliferation, while the decrease in HIF1α gene expression evidenced the decrease in cell survival.

Many studies have highlighted the anti-tumor properties of some natural peptides known to have antimicrobial virtues. In this study, we evaluated the tumoricidal potential of dermaseptin, defensin, cecropin A and B on tumor cell lines: M14K (human mesothelioma). The viability study was performed using PE V Annexin and 7-AAD (7-amino-actinomycin D) (BD Pharmingen). This test was used to detect and measure apoptosis by flow cytometry technique. The experimental results of our study revealed that the cytotoxic effects of the four peptides depend on their concentration. In this in vitro experimental study, we found that the cytotoxic effect of the four cytotoxic peptides used depended on their concentration in the tumor cell culture medium, being significant at concentrations of 120mM and maintained at concentrations of 60�M. At 30�M concentrations these tumoricidal effects were insignificant. Of all the studied peptides, dermaseptin has the most powerful effect and the weakest effect b - defensin - 1.

We evaluated, by the flow cytometry technique, the viability of two tumor cell lines: colorectal carcinoma (HT-29) and human A549 arcinoma incubated with the cytotoxic peptide LL-37. The results obtained for the two cell lines HT-29 and A549 are significantly different under the action of cathelicidin LL-37. At high concentrations of 20mM, cellular apoptosis was over 30% higher for colorectal adenocarcinoma line compared to that by peptide exposure. Apoptosis was also significant in low-concentration (4uM) catechidine-labeled lung cancer cells for 48 h. Also, optimization of primers was sought to evaluate gene expression for, Bcl2, IL6, IL8. Determination of gene expression for these molecular targets under the action of the cytotoxic peptide was performed in order to evaluate the immune response of tumor cells. For this purpose, the genetic material (RNA) was extracted from cell cultures and reversed in cDNA, which was subsequently amplified by the qRT-PCR technique. Evaluation of tumor cell metabolism was done by determining the gene expression for Bcl2, IL6, IL8 by the action of the cytotoxic peptides used. The cytotoxic effect of cathelicidin LL-37 for the two cell lines HT29 and A549 is supported by the decrease in IL-6 and IL-8 gene expression. The increase in Bcl2 expression for cells exposed to the action of the peptide is explained by the increase in anti-apoptotic protein synthesis that explains the fight of tumor cells for survival and proliferation.