Induction of Apoptosis with Cyrtopodion Scabrum Extract in Colon Cancer Cells: A Preliminary Study on Targeting P53 Signaling Pathway

Background: Cyrtopodion scabrum is a kind of lizard, widely distributed in southwestern, central, and eastern Iran. In our previous studies, we showed the selective anticancer properties of Cyrtopodion scabrum extract (CSE) against certain gastroin- testinal cancer cell lines with no significant harmful effects on the normal cells. Method: This in vitro study was conducted to investigate the mechanism of action of CSE in SW742 (colon cancer cell line) using western blotting, real-time polymerase chain reaction (PCR), and PI staining/flow cytometry analysis. Results: Western blot analysis showed that CSE upregulates P53 protein expression significantly in SW742 cancer cell line, while QRT-PCR results revealed that P53 mRNA did not increase accordingly. It is proposed that TP53 protein play its role as a tumor suppressor through the protein stability mechanism and not through the increase in the gene expression. Considering this fact, for TP53 stabilization, two of its target genes, p21 and mdm2, were regulated. We evaluated the mRNA expression of these two genes as well. The obtained data showed a significant increase in both genes by CSE (1000 μg/ml), suggesting that the induction of G2 cell cycle arrest, which we previously reported, may happen through P53 and P21over-expression. No significant decrease was observed in apoptosis when SW742 cells were co-treated with CSE and the inhibitor of P53 transcriptional activity, (PFT)-α, indicating that the induction of apoptosis with CSE did not occur through P53-dependent transcriptional activity. Conclusion: The obtained results herein revealed that the observed anticancer effect of CSE may occur through TP53 upregulation, yet with P53-independent tran- scriptional activity.