The Synergetic Efficacy And Mechanism Of NVP-BEZ235 And STA-9090 Against HER2-positive Breast Cancer Cell Lines

Objective : To investigate the resistance mechanism of NVP-BEZ235 in HER2-positive breast cancer cell lines,and the combination effect of NVP-BEZ235 with STA-9090.Methods :(1)MTT assay was used to assess cell proliferous inhibition of NVP-BEZ235 and STA-9090 in HER2-positive bresast cancer cells.(2).Western blot was applied to reveal the protein expression and action of receptor tyrosine kinases(RTKs)HER family and related proliferous signaling pathway in time-dependent manner,and the combination effect of NVP-BEZ235 with STA-9090.(3)Apoptotic induction was detected by flow cytometry.(4)The inhibitory effect of colony formation was tested by colony formation assay.Results:(1)NVP-BEZ235 and STA-9090 obviously inhibited cell proliferation in HER2 positive breast cancer cell lines MDA-MB-453 and SKBR3,with IC50 of 0.0696、0.0815 and 0.0103、0.0358 μmol·L-1,respectively,the CI index was between 0.4-0.7.(2)NVP-BEZ235 induced feedback increase of HER family members expression and activity,including EGFR、HER2 and HER3;In addition,the activity of MAPK pathway was increased and Akt was rephosphorylated on T308 but lacking S473.(3)NVP-BEZ235 and STA-9090 induced apoptosis of HER2 positive breast cancer separately and achieved a more pronounced effect together.(4)NVP-BEZ235 or STA-9090 suppressed the colony formation of HER2-positive breast cancer cells and had a synernetic effect together.(5)STA-9090 inhibited HER family activation and expression caused by NVP-BEZ235 and degraded the phosporylation of Akt and ERK,increased the antitumor activity of NVP-BEZ235.Conclusion:(1)NVP-BEZ235 shows potent anti-proliferative effect against HER2-positive breast cancer cells MDA-MB-453 and SKBR3 in vitro and is synergistic with STA-9090.(2)NVP-BEZ235 relieves the feedback suppression of HER family receptors expression and activity,and induces Ras/Raf/ERK axis expression,PI3 K pathway is reactivated but lacking Akt S473.(3)STA-9090 increases the apoptosis and inhibition of cell proliferation induced by NVP-BEZ235,decreases MAPK pathway activity and inhibits the upstream signals expression of NVP-BEZ235,this may be the mechanism of synergy.