XIAP gene downregulation by small interfering RNA inhibits proliferation, induces apoptosis, and reverses the cisplatin resistance of ovarian carcinoma.

Objective: XIAP is one of the most important members of the inhibitors of apoptosis family. It is upregulated in various malignancies, including human ovarian carcinomas, it promotes invasion, metastasis, growth, and survival of malignant cells, and it also confers resistance to some chemotherapeutic drugs. We observed the effect of XIAP gene RNA interference (RNAi) on the proliferation, apoptosis, tumorigenicity, and chemosensitivity of the human ovarian carcinoma cells A2780/cp70.

Study Design: We used a human U6 promoter-driven DNA template approach to induce short hairpin RNA-triggered RNAi to block XIAP gene expression in the human ovarian cancer cell line A2780/cp70. A corresponding site-mutated vector was constructed as a negative control (pSilencer 2.1-NC). The expression of XIAP mRNA and protein among the stable transfected cells and the untransfected ones was detected by RT-PCR and Western blotting. The cell growth was examined and drug sensitivity was assayed using the MTT assay. Cell apoptosis was measured by flow cytometry and the tumorigenicity by using nude mice.

Results: Three stable transfected cell lines: A2780/cp70-s2, A2780/cp70-NC, and A2780/cp70-neo were established. The expression levels of XIAP gene mRNA and protein in A2780/cp70-s2 were 63.3% and 60.8%, lower than in A2780/cp70-NC, A2780/cp70-neo, and untransfected A2780/cp70 cells. The cell proliferation of A2780/cp70-s2 was reduced by up to 62.2+/-1.9%. Compared with the other cell lines, the changes in apoptotic rate in A2780/cp70-s2 was 31.1+/-1.3%, obviously increasing (P<0.05). The knockdown of XIAP retards tumorigenicity in nude mice and after 21 days the average tumor weight of the A2780/cp70-s2 group was lower by 1.62+/-0.11g (P<0.05). And the survival index in A2780/cp70-s2 cells was markedly reduced with the addition of 1 microM and 10 microM cisplatinum, respectively (P<0.05).

Conclusions: XIAP gene RNAi inhibited the proliferation of ovarian carcinoma cells and caused cells to be more sensitive to cisplatin through the reduction of its mRNA and protein. These results suggest that XIAP is an ovarian cancer-related gene and that XIAP is a potential target for therapeutic anti-cancer drugs.