Abstract: Objective To explore the effects of lysyl oxidase（LOX） silencing on proliferation in the breast cancer cell line MDA-MB-231. Methods MDA-MB-231 cultures were divided into three test groups:the RNAi group，the Mock negative control group，and the Con control group，LOX， Ki-67 and cyclin D1 mRNA expression was analyzed by real-time RT-PCR，and LOX protein expression was analyzed by Western blot. Cell growth and proliferation of transfected cells were measured by MTT and cell colony formation assays. Results Expression of both LOX mRNA and protein was significantly down-regulated in the RNAi group. This group also showed significantly less cell growth，less cell colony formation，and lower levels of Ki-67 and cyclin D1 mRNA than the Mock and Con groups（P<0.05）. Conclusions Transfecting MDA-MB-231 cells with LOX-RNAi-LV can significantly interfere with LOX mRNA and protein expression，inhibiting growth and proliferation of breast cancer cells.These effects may be related to down-regulation of Ki-67 and cyclin D1.

Key words: Breast neoplasms, Lysyl oxidase （LOX）, RNA interference, Cell proliferation, Proliferation factor