Preliminary Study On The Function And Mechanism Of STIP1 In Tumorigenesis And Development Of Breast Cancer

BackgroundBreast cancer is the common and leading cause of cancer-related deaths in women worldwide,and searching for specific therapeutic targets and prognostic markers is still at the forefront of research.Stress-induced phosphoprotein 1(STIP1),functions as an adapter that directs Heat Shock Protein 70 and 90 complexes,involved in many biological processes such as RNA slicing,transcription,and protein folding.Extensive studies have demonstrated that STIP1 is up-regulated in several cancers.STIP1 may act as an oncogene and regulate tumor carcinogenesis and progression.However,the role of STIP1 in breast cancer is still not completely understood.Purpose1.To investigate the expression of STIP1 in breast cancer tissues,and analyze the clinical and prognostic significance of STIP1 expression in breast cancer patients.2.To explore the effect of STIP1 aberrant expression on the malignant biological characteristics of breast cancer cells and its underlying mechanisms.Methods1.Using bioinformatics database to mine the expression profile and clinical data of breast cancer patients,analyze the relationship between STIP1 differential expression and clinicopathological parameters,and explore the prognostic value of STIP1 expression in breast cancer patients.2.Using real-time PCR and Western blot method to quantificationally detect the expression of STIP1 in breast cancer cell lines(MCF-7,MDA-MB-231)and normal mammary epithelial cell(MCF-10A).3.Suppression and overexpression the expression of STIP1 in breast cancer cells using siRNA and lentivirus,respectively.And then investigate the effects of STIP1 interference and overexpression on cell proliferation,apoptosis,migration and invasion in vitro by CCK-8,EdU,cloning formation,flow cytometry,wound healing,transwell migration and invasion experiments.4.Using Western blot to detect the expression changes of epithelial mesenchymal transition(EMT)-related markers E-cadherin,Vimentin,SNAI1 and signal-related molecules phospho-AKT,AKT,phospho-ERK1/2 and ERK1/2 in breast cancer cells after interference and overexpression STIP1.Results1.Database mining results show that STIP1 expression is elevated in breast cancer tissues,and positively correlates with advanced TNM stage,histological grade,Nottingham prognostic index,HER-2 status,basal-like status and triple-negative status.Estrogen receptor and progesterone receptor status were negatively correlated with STIP1 level in breast cancer.Patients with high STIP1 expression show significantly shortened recurrence-free survival time,distant-metastasis-free survival time,event-free survival time and metastatic relapse free survival time.2.The expression levels of STIP1 mRNA and protein in breast cancer cell lines MCF-7 and MDA-MB-231 were significantly higher than those in normal breast epithelial cells MCF-10A,especially elevated expression in triple negative breast cancer cell line MDA-MB-231.3.Interfering STIP1 expression significantly suppresses proliferation,migration and invasion abilities,and promotes apoptosis of breast cancer cells.In contrast,overexpression of STIP1 yielded the opposite effects on these phenotypes in vitro.4.STIP1 suppresses the expression of E-cadherin,promotes the expression of Vimentin and SNAI1,and activates AKT and ERK1/2 signaling pathways in breast cancer cells.ConclusionsElevated expression of STIP1 exhibited as an oncogene in breast cancer through induced EMT and involved in activation of AKT and ERK1/2 signaling pathways.STIP1 therefore may be served as a potential prognostic biomarker and therapeutic target of patients with breast cancer.