Apoptosis In Anti-Tumor Effect Of Irinotecan Is Mediated By P53 In Human Hepatocellular Carcinoma Cell Line.

Purpose Frequently used anti-cancer drug irinotecan(CPT11), inhibitor of DNA synthesis, is recently known as to have apoptosis effect, though little is known yet. This study investigated this apoptosis mechanism in human hepatocelluar carcinoma cell lines (Huh7). Methods The cells were cultured with SN38, active metabolite of CPT11, for 24 h. The cells were analyzed to investigate expression of p53 protein and apoptosis related protein by Western Blotting. In addition to this, another group of cells were cultured with SN38 after p53 antisense(AS) pre-treatment for 24 h and were analyzed by immunocytochemistry for apoptosis related protein evaluation. Results SN38 decreased cell survival, and increased expression of p53, caspase-3 and CAD (caspase-activated DNase). Expression of Bcl-xL was suppressed by SN38. On the other hand, in p53 AS pre-treated cells, SN38 decreased expression of p53 protein and apoptosis was suppressed. Caspase-3 expression was induced by SN38 while suppressed by p53 AS+SN38 treatment. Anti-apoptotic protein Bcl-xL was suppressed by SN38 while not by p53 AS+SN38. Conclusion This study proved active metabolite SN38 increased p53, apoptosis inducing protein caspase-3, and decreased anti-apoptotic protein Bcl-xL, while these changes were reversed by p53 AS pre-treatment. these results suggest that p53-mediated apoptosis is important mechanism for CPT11 anti-tumor effect on human hepatocellular carcinoma. Clinical Pharmacology & Therapeutics (2004) 75, P60–P60; doi: 10.1016/j.clpt.2003.11.228