Increased cytotoxicity of Irinotecan or 5FU by expression of p16 INK4a in A549 lung carcinoma cell

Abstract

Abstract One of the main pathways for cell cycle control is the block of cyclin D1/CDK4 by p16INK4a. In many malignancies, including lung cancer, the p16INK4a gene has been, mutated, methylated or deleted, resulting in the tumor progression. We have previously show that the C-terminal truncated form of p16 can inhibits cell growth, restrain cell cycle at G0/G1and induce cell death similar to full length. In this study we have tested whether, the truncated p16 can have additive effect on irinotecan or 5FU induced cytotoxicity in A549 lung adenocarcinoma cells. The truncated as well as full length p16 was transfected into A549 cell line and the expression level was evaluated. The cell viability and cell cycle of the cells treated with drugs was measured with MTT test and flow cytometry. Both full length and truncated p16 induced cytotoxicity in these cells. The expression of p16 decreased cell viability of A549 treated with irinotecan or 5FU were 40.99 ± 2.28 and 41.95 ± 3.28 in IC25, respectively. The viability of cells expressing p16 and treated with IC50 and IC25 of irinotecan or 5FU was significantly reduced. The expression of truncated p16 increased cytotoxicity of 5FU by 80% in IC25 treated cells. Considering the drug treated dose, the expression of truncated p16, in lower drug dose has induced more cytotoxicity. Similarly, the cell cycle arrest and subG1 was increased in cell expressing truncated p16 and treated with drug. Therefore, the expression of truncated p16 has augmented the cytotoxicity of 5FU in A549 cells and the expression of p16 or molecule similar to p16 have the potential to be used as combination therapy in treatment of lung cancer.