Azacitidine enhances sensitivity of platinum-resistant ovarian cancer cells to carboplatin through induction of apoptosis

OBJECTIVE: The objective of the study was to investigate whether azacitidine sensitizes platinum-resistant ovarian cancer cells to carboplatin and the possible mechanisms involved. STUDY DESIGN: We tested the in vitro antitumor activity of azacitidine both alone and combined with carboplatin in the ovarian cancer cell line 2008/C13 and Hey by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assays and investigated the potential mechanisms by flow cytometry, terminal transferase deoxyuridine 5-triphosphate nick-end labeling assay, Western blot, reverse transcriptase-polymerase chain reaction (PCR), and promoter methylation-specific PCR. RESULTS: Sequential treatment (ie, 24-hour azacitidine pretreatment followed by 48-hour cotreatment with azacitidine and carboplatin) significantly inhibited growth in 2008/C13 and Hey cells. More apoptotic cells were induced in 2008/C13 cells by sequential treatment than by a single drug. Increased cleaved caspase-3 and -8 were seen in 2008/C13 cells after sequential treatment with azacitidine and carboplatin. DR4 was demethylated, and DR4 messenger ribonucleic acid expression was increased in 2008/C13 cells after the 24-hour azacitidine treatment. CONCLUSION: Azacitidine enhanced the sensitivity of platinum-resistant ovarian cancer cells to carboplatin associated with caspase-3- and -8-dependent apoptosis pathway and reexpression of DR4.