Effect of combined 5-aza-2′deoxycytidine and cisplatin treatment on the P15 lung adenocarcinoma cell line

Aberrant promoter hypermethylation resulting in the epigenetic silencing of apoptosis-associated genes is a key process in the chemotherapeutic treatment of cancer. The nucleoside analog, 5-aza-2'deoxycytidine (DAC), inhibits the activity of DNA methyltransferase enzymes and is able to restore the expression levels of genes that have been silenced by aberrant DNA methylation. The aim of the present study was to investigate the effect of combined treatment with DAC and cisplatin (CDDP) on the lung adenocarcinoma cell line, P15. Growth inhibition was examined using a clone formation assay and growth inhibitory activities by cell counting during treatment with DAC alone, CDDP alone or DAC followed by CDDP. In addition, changes in the mRNA expression levels of various apoptosis-associated genes following treatment with increasing concentrations of DAC were determined using reverse transcription-polymerase chain reaction. Furthermore, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis was used to detect the number of apoptotic P15 tumor cells following treatment with DAC and/or CDDP. The results indicated that DAC treatment alone restored the mRNA expression levels of p73, p16(INK4a), B-cell lymphoma (Bcl)-2-associated agonist of cell death and Bcl-2-associated X protein. In addition, combined therapy with DAC and CDDP was found to significantly suppress the growth of P15 tumor cells compared with DAC or CDDP treatment alone. In conclusion, DAC may enhance the chemosensitivity of the P15 cell line to treatment with CDDP.