AHNAK2 Is A Novel Prognostic Marker And Oncogenic Protein For Clear Cell Renal Cell Carcinoma

Objective:Clear cell renal cell carcinoma(ccRCC)is the most common renal carcinoma and a devastating type of cancer,responsible for approximately 75%of cases of kidney cancer.To identify novel oncogenes overexpressed in clear cell renal cell carcinoma(ccRCC),we performed integrative data-mining analysis across multiple datasets from the Oncomine database.AHNAK2 was identified as one of the novel overexpressed genes.AHNAK2 is a member of the AHNAK family and has been implicated in mediating stress-induced FGF1 secretion.However,the function of AHNAK2 is currently unknown in cancer cells.In this study,we attempt to explore the function and mechisms of AHNAK2 in clear cell renal cell carcinoma progression.Methods:The expression pattern of AHNAK2 was assessed by quantitative real time polymerase chain reaction(qRT-PCR)and immunostaining in human clear cell renal cell carcinoma(ccRCC)cells and clinical samples.Prognostic analysis was performed using the Kaplan-Meter method.Cell proliferation,cell apoptosis,colony formation,migration and xenograft models were used to determine the effects of AHNAK2 in ccRCC.AHNAK2 promoter activity was analyzed using chromatin immunoprecipitation and luciferase reporter assays.AHNAK2-related downstream mechanism was examined by qRT-PCR and immunoblotting and studied in clinical samples.All statistical tests were two-sided.Results:Levels of AHNAK2 mRNA and protein were upregulated significantly in ccRCC compared to adjacent normal tissues.High expression of AHNAK2 was correlated with tumor progression and poor survival(two sources:n=355,hazard ratio(HR)=2.063,95%confidence interval(CI)=1.063 to 4.006,p=0323;n=494,HR=1.54,95%CI=1.04 to 2.28,p=.0225).Knockdown of AHNAK2 enhanced cell apoptosis and inhibited tumor growth in vitro and in vivo.Hypoxic activation of the expression of AHNAK2 was HIF1?-dependent.Knockdown of AHNAK2 impaired hypoxia-induced epithelial-mesenchymal transition(EMT)and lipid synthesis.Conclusion:AHNAK2 is upregulated in ccRCC and hypoxic upregulation of AHNAK2 can drive tumorigenesis and progression by supporting EMT and lipid synthesis.Thus,AHNAK2 is a novel prognostic marker and an oncogenic protein for ccRCC.