Rapamycin enhances chemosensitivity of endometrial cancer cells to adria-mycin

AIM: To explore the therapeutic effect of adriamycin combined with rapamycin on endometrial cancer cells. METHODS: Two endometrial carcinoma cell lines with different PTEN gene states were chosen: HEC-1A (wild type) and Ishikawa (mutant type). Before adriamycin administration, the cells were pretreated with low concentration of rapamycin for 24 h. The cell viability and 50% inhibitory concentration (IC₅₀) of adriamycin at 24 h were determined by MTT assay. Multiple drug effect/combination index (CI) was used to evaluate the interaction between adriamycin and rapamycin. Apoptotic rate was measured by flow cytometry. The effects of the drugs on phosphorylation of PI3K/Akt and apoptosis protein caspase-3 were detected by Western blotting. RESULTS: Both adriamycin and rapamycin showed obvious growth inhibitory effects on the 2 endometrial cancer cell lines in a time- and dose-dependent manner. After pretreated with rapamycin, IC₅₀ of adriamycin decreased sharply. In Ishikawa cells, it decreased from (21.3±3.8) μmol/L to(11.9±1.2) μmol/L,P<0.05. In HEC-1A cells, it decreased from (14.3±2.8) μmol/L to (8.2±0.9) μmol/L,P<0.05. Combination index value of the 2 drugs was more than 1.15 in the 2 endometrial cancer cell lines, indicating synergistic effects. The combination therapy of adriamycin with rapamycin increased apoptotic rates in the 2 cell lines, and induced the down-regulation of phosphorylated Akt and over-expression of caspase-3 as compared with single drug treatment (P<0.05). CONCLUSION: Adriamycin combined with rapamycin significantly enhances the chemosensitivity of endometrial cancer cells and reduces drug resistance, which will become a new trend for treating endometrial cancer.