Research On The Mechanism Of FGFR1 Regulating Proliferation,Epithelial-Mesenchymal Transition,and Metastasis In FGFR1-Amplified Lung Cancer

Introduction and Objective:Epithelial-mesenchymal transition(EMT)is an important process for cancer metastasis,drug resistance and cancer stem cells.Activation of fibroblast growth factor receptor 1(FGFR1)was found to promote EMT and metastasis in prostate and breast cancers,but the effects and mechanisms in lung cancer was unclear.This research aimed to explore whether and how activation of FGFR1 promotes EMT and metastasis in FGFR1-amplified lung cancer,to clarify its molecular mechanism,and to explore the clinical significance of this mechanism in FGFR1-targeted therapy.Methods:Firstly,we used FGFR1 ligands fibroblast growth factor 2(FGF2)and specific short interfering RNAs(siRNAs)to activate and inhibit FGFR1 in FGFR1-amplified lung cancer cell lines,respectively.And CCK8,Western blot,qPCR,scratch and Transwell assays,and immunofluorescence staining were performed to explore the mechanisms of FGFR1 in cell proliferation,EMT,migration and invasion in FGFR1-amplified lung cancer.Secondly,MEK/ERK inhibitor AZD6244 and sustained autophosphorylation variant ERK2_R67S plasmid were used to explore by which mechanism Sry(sex determining region of Y chromosome)-related HMG box 2(SOX2)was upregulated by FGFR1.Furthermore,we used lentivirus transduction to generate SOX2-overexpressing and SOX2-silened stable cell lines,and examined whether FGFR1 promotes proliferation,EMT and metastasis by upregulation of SOX2.Thirdly,orthotopic and subcutaneous lung cancer xenograft models were established to demonstrate the effects of FGFR1 inhibition on tumor growth,SOX2 expression,EMT,and metastasis in vivo.Finally,the clinical relevance of FGFR1 and SOX2 overexpression was investigated using lung cancer patient datasets.Results:Activation of FGFR1 promoted proliferation,EMT,migration and invasion in FGFR1-amplified lung cancer cell lines H1581 and DMS114,whereas inhibition of FGFR1 suppressed these processes.FGFR1 activation upregulated expression of SOX2 by downstream phosphorylated ERK1/2;and the upregulation of SOX2 by sustained autophosphorylation variant ERK2_R67S plasmid was not suppressed by FGFR1 inhibitor AZD4547 or MEK/ERK inhibitor AZD6244.And SOX2 expression was also significantly upregulated in ERK2_R67S lentivirus transfected stable cell lines in vivo.Overexpression of SOX2 promoted cell proliferation,EMT,migration and invasion in vitro and in vivo.Importantly,activation of FGFR1 could not promote these processes in SOX2-silenced stable cell lines.In orthotopic and subcutaneous lung cancer xenograft models,inhibition of FGFR1 suppressed tumor growth,SOX2 expression,EMT and metastasis.Higher expression of FGFR1 and SOX2 were positively correlated,and both were associated with shorter survival in lung cancer patients.Discussion and Conclusion:In this research,we identified a novel signaling pathway that activation of FGFR1 upregulated expression of SOX2 by downstream phosphorylated ERK1/2.The newly defined FGFR1-ERK1/2-SOX2 axis promotes cell proliferation,EMT,migration and invasion,and tumor metastasis in FGFR1-amplified lung cancer cell lines H1581 and DMS114 in vitro and in vivo.This research has important clinical significance for FGFR1-targeted therapy in lung cancer.