Objective To investigate if down regulation of MTDH could inhibit proliferation and induce apoptosis in breast cancer SK-BR-3 cells.Methods RNA interference was employed to reduce MTDH expression in human breast cancer SK-BR-3 cells.Western blot assay was applied to measure the down regulation of MTDH.MTT assay was performed to assess the proliferation of SK-BR-3 cell.Flow cytometry was employed to detect cell cycle and apoptosis.Western blot assay was applied to detect the molecular alterations that was associated with cell proliferation,cell cycle and apoptosis.Results MTDH down regulation significantly inhibited cell proliferation.48 hours and 72 hours after trasnfection,the absorbance value(A value)in blank control,negative control and treatment group was (2.0 ± 0.1) vs (1.9 ± 0.3) vs (0.9 ± 0.1) (P =0.02) and (2.7 ± 0.2) vs (2.5 ± 0.4) vs (1.3 ± 0.2) (P =0.008).MTDH down regulation resulted in accumulation of the G0/G1 phase cells and reduction of S and G2/M phase cells.Moreover,MTDH down regulation significantly induced cell apoptosis.The cell apoptosis rate in blank control,negative control and trial group was (1.3 ± 0.2) ％,(1.4 ± 0.3) ％ and (19.6 ± 2.7) ％ (P =0.012).MTDH down regulation resulted in a decreased expression of cyclinD1 and Bcl-2,an increased expression of P21 and the activation of caspase-3.Conclusions Reduced MTDH expression in SKBR-3 cells can inhibit proliferation and induce apoptosis,which may be associated with decreased expression of cyclinD1 and Bcl-2,an increased expression of P21 and the activation of caspase-3.

OBJECTIVETo investigate the effect of mTOR signal transduction pathway and down-regulating anti-oncogene PTEN on the growth of breast cancer MCF-7 cells.

METHODSMCF-7 cells were transfected with the eukaryotic expression plasmid pcDNA3.1-mTOR and non-loaded plasmid, and the expression of mTOR in the cells was detected using Western blotting. Flow cytometry was used to analyze apoptosis and cell cycle of the transfected cells, and the expression of PTEN was detected after transfection.

RESULTSThe cells transfected with pcDNA3.1-mTOR showed a increased growth rate than those transfected with the non-loaded plasmid and those without transfection. The expression of the protein PTEN decreased obviously in the cells after mTOR trasnfection.

CONCLUSIONmTOR can regulate the expression of PTEN via PI3K/AKT/PTEN pathways through a negative feedback mechanism. Increased mTOR expression promotes MCF-7 cell growth, suggesting the potential value of mTOR specific inhibitor in the treatment of breast cancer.

Apoptosis ; Breast Neoplasms ; pathology ; Cell Cycle ; Down-Regulation ; Gene Expression Regulation, Neoplastic ; Humans ; MCF-7 Cells ; PTEN Phosphohydrolase ; metabolism ; Plasmids ; Signal Transduction ; TOR Serine-Threonine Kinases ; genetics ; Transfection