BRCA1 Associated Protein Activates Esophageal Squamous-cell Carcinoma Invasiveness

Background&Aims:Metastasis is a major cause of cancer death but the molecular mechanism remains largely unknown.It has been suggested that genes involved in cancer development may also be relevant to cancer invasiveness.This study investigated whether esophageal squamous cell carcinoma(ESCC)susceptibility genes identified in our previous studies also play a role in metastasis.Methods:We analyzed effects of 47 ESCC susceptibility genes on cancer cell migration in vitro by RNA interfering-based on-chip assays.Candidate gene was expressed or knocked down in ESCC cells(KYSE30 and KYSE150)and HeLa cells using lentiviral vectors;we analyzed effects on migration and invasion in vitro.Cells were grown as xenograft tumors in nude mice and tumor volume and metastases were quantified.Cells were also analyzed for molecule mechanism promoting metastasis by reporter assay,immunofluorescence,immunoblotting and immunoprecipitation assays.Besides,levels of mRNAs and proteins in tissue samples were measured by RNA sequencing,immunoblotting or immunohistochemistry.Log-rank test was used to compare survival by different mRNA levels.Hazard ratio and 95%confidence interval were calculated by Cox multivariate models.Results:We identified BRCA1 associated protein(BRAP)as a player in cancer cell invasiveness.Knockdown of BRAP reduced invasion of ESCC cells in culture and metastasis of xenograft tumors in mice.Cells overexpressed BRAP were more invasive in assays and had increased NF-?B activation via phosphorylating IKK? by PKCa which leads to phosphorylation and degradation of IKB?.Cells overexpressed BRAP had increased expression of NF-KB-regulated,metastasis-associated genes,such as matrix metalloproteinase 9(MMP9)and vascular epithelial growth factor C(VEGFC).ESCC tissues had increased BRAP copy number and levels of mRNA and protein compared with non-tumor tissues;the increased mRNA levels were associated with reduced patients'survival time.Conclusion:In an analysis of ESCC samples and cell lines,we associated increased expression of BRAP with tumor invasiveness and patient survival time.Overexpression of BRAP in ESCC cell lines activates NF-?B signaling,upregulates expression of MMP9 and VEGFC and forms metastatic xenograft tumors in mice.Overexpression of BRAP might be used as a therapeutic target for ESCC.