Studio dell’azione antiproliferativa di oxaliplatino e pemetrexed in linee cellulari di carcinoma del colon-retto: meccanismi cellulari e molecolari

Oxaliplatin is active in the treatment of colorectal cancer and its effect is improved upon combination with thymidylate synthase (TS) inhibitors. Pemetrexed is polyglutamated by the folylpolyglutamate synthase (FPGS) and blocks folate metabolism and DNA synthesis by inhibiting TS, dihydrofolate reductase (DHFR) and glycinamide ribonucleotide formyltransferase (GARFT). The present study evaluated the pharmacological interaction between oxaliplatin and pemetrexed and established the optimal combination schedule in colorectal cancer cell lines. HT29, WiDr, SW620 and LS174T cells were treated with drugs, alone or in combination: a dose-dependent inhibition of cell growth was observed after oxaliplatin and pemetrexed exposure, while a synergistic interaction was observed mostly with sequential combinations. Oxaliplatin enhanced cellular population in the S-phase thus rendering cells more sensitive to pemetrexed. Drug combinations increased apoptotic index with respect to single agents, and treatment with oxaliplatin and pemetrexed inhibited Akt phosphorylation. RT-PCR showed a correlation between the FPGS/(TS×DHFR×GARFT) ratio and pemetrexed sensitivity, as well as a downregulation of genes involved in DNA repair (ERCC1 and ERCC2), TS, DHFR and GARFT after drug exposure. These data demonstrate that oxaliplatin and pemetrexed synergistically interact against colon cancer cells, through modulation of cell cycle, inhibition of Akt phosphorylation, induction of apoptosis and modulation of gene expression.