Preclinical evaluation of antisense bcl‐2 as a chemosensitizer for patients with gastric carcinoma

BACKGROUND: Because bcl-2 is a critical factor for anticancer drug-induced apoptosis, the authors conducted a preclinical evaluation of antisense (AS) bcl-2 as an enhancer of the chemotherapeutic effect in the treatment of patietns with gastric carcinoma. METHODS: AS bcl-2 was used with 18-mer phosphorothiated oligonucleotides in the MKN-45 gastric carcinoma cell line. Drug sensitivity in vitro was evaluated using the methyl-thiazoldiphenyl tetrazolium assay, and antitumor effects in vivo were evaluated using the nude mouse xenograft. Apoptosis was determined with the terminal deoxyuridine triphosphate nick-end labeling assay. AS bcl-2 in vitro was treated with lipofectin, whereas it was administered intraperitoneally for 6 consecutive days twice every 2 weeks in vivo. Anticancer drugs were administered intraperitoneally four times per week. RESULTS: bcl-2 was down-regulated to 60% of its initial value after treatment with 1.0 muM AS bcl-2 compared with the controls of random and mismatched oligonucleotides. Drug sensitivity to doxorubicin, cisplatin, and paclitaxel (TXL) was increased 3-4-fold when used in combination with AS bcl-2, which was determined with 50% inhibitory concentration values, compared with the control group. Increased drug sensitivity was associated with apoptosis, which increased in Bax and poly-adenosine diphosphate (ADP-ribose) polymerase and decreased in phosphorylated Akt (pAkt). The antitumor effect of cisplatin and TXL in vivo was enhanced significantly in combination with AS bcl-2. Down-regulation of bcl-2 was observed on Day 4 after the treatment with AS bcl-2. CONCLUSIONS: Combination treatment with AS bcl-2 and anticancer drugs, including cisplatin and TXL, may be a new strategy for enhancing chemotherapeutic effects in the treatment of gastric carcinoma.