Background & objective: The breast and ovarian cancer susceptibility gene BRCA1 acts as a tumor suppressor gene, its product expresses in a cell cycle-dependent manner. Inheritance of a mutant allele of BRCA1 leads to increased risk of developing breast,and ovarian cancers. Lovastatin, as a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase),is the main rate-limiting enzyme of endogenous cholesterol biosynthesis pathway. This study was to evaluate the effect and mechanism of combined application of BRCA1 and lovastatin on cell cycle distribution of MCF-7 cells.
Methods: MCF-7 cells were transfected with expression vector pcDNA3-beta-HA-hsBRCA1 containing full-length BRCA1, and named MCF-7BRCA1 cells. The expression of BRCA1 gene was examined with reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. After cultured with 8 micromol/L lovastatin, growth curve and MTT assay were used to determine cell proliferation capacity; the cell cycle distribution was measured with flow cytometry (FCM). Meanwhile,the protein expression of Cyclin D1 and retinoblastoma (Rb) were analyzed by Western blot analysis.
Results: The pcDNA3-beta-HA-hsBRCA1 plasmids were successfully transfected into MCF-7 cells and expressed stably. The growth curve and MTT assay results showed that cell proliferation capacity decreased in the cells cultured with lovastatin for 4 days. FCM showed that S phase, and G2/M phase of BRCA1-infected cells decreased,while G0/G1 phase increased after cultured with lovastatin, the cells were blocked in G0/G1 phase at 72 h post-treatment by lovastatin. Ectopic expression of BRCA1 leads to decrease of the Rb protein and Cyclin D1 protein. Overall data showed that the effects of Lovastatin were more obviously in MCF-7BRCA1 cells than MCF-7 cells.
Conclusions: Overexpression of BRCA1 protein may amplify sensibility of breast cancer to lovastatin,and enhance the anti-tumor effect of lovastatin.