C-Src Inhibitor Selectively Inhibit Vimentin Positive Triple-negative Breast Cancer

Backgrounds: The treatment of triple-negative breast cancer(TNBC)is currently a worldwide problem in the field of tumor therapy.Proto-oncogene c-Src is highly expressed in various subtypes of breast cancer,but studies have found that inhibitors targeting c-Src have a stronger inhibitory effect on TNBC than other subtypes of breast cancer in vitro.This study investigated the mechanism that causes c-Src inhibitors selectively inhibit TNBC.Objective: To investigate the different level inhibitory effect of c-Src inhibitors on different subtypes of breast cancer cell lines,and further study the molecular mechanism of selective inhibition of TNBC by c-Src inhibitors in order to guide the clinical treatment of TNBC patients.Materials and methods: Four different subsets of breast cancer cell linesSUM1315MO2(TNBC),MDA-MB-231(TNBC),T-47D(HER2+)and SK-BR-3(ER+)-and c-Src family kinase inhibitor PP2 were used in this study.Firstly,a variety of cell function experiments(CCK-8,Colony formation assay,Cell cycle analysis,Wound-healing assay,Cellular migration and invasion assay)were used to verify c-Src inhibitors selectively inhibit TNBC.The signal pathways affected by c-Src inhibitors were explored by real-time q RT-PCR and Western blot methods.Furthermore,short hairpin RNA(sh RNA)was used to study the mechanism of how vimentin participates in and affects the efficacy of PP2.Finally,a tumor xenograft mouse model was used to demonstrate the effect of vimentin expression on c-Src inhibitor treatment of TNBC.Results: Herein,we demonstrated that PP2 was effective to inhibit the phosphorylation of c-Src in the four cell lines.However,PP2 only preferentially reduced S phase of cell cycles and inhibited colony formation in TNBC cell lines,SUM1315MO2 and MDA-MB-231,but not in SK-BR-3 and T-47 D cells.In addition,PP2 also effectively blocked the cell migration/invasion and epithelial-mesenchymal transition(EMT)in SUM1315MO2 and MDA-MB-231.An EMT biomarker,vimentin was highly expressed in two TNBC cell lines when they were compared with SK-BR-3 and T-47 D cells.Further depletion of vimentin by short hairpin RNA(sh RNA)remarkably attenuated the inhibitory effects of the c-Src inhibitor on TNBC cells in vitro and in vivo.Conclusions: The inhibitory effect of c-Src inhibitor on TNBC was significantly stronger than that of non-TNBC.High expression of vimentin allows c-Src inhibitors to control TNBC proliferation,migration,and invasion by inhibiting cell cycle and EMT.This study provides a basis for guiding the clinical to use c-Src inhibitors in TNBC patients,Vimentin may be considered as an important biomarker for subdividing TNBC.