SP1.1.7PBX4 functions as a novel oncogene and promotes angiogenesis in colorectal cancer: A comprehensive analysis of the PBX gene family

Abstract

Abstract Aims Pre-B-cell Leukaemia (PBX) genes are important in organ development during embryogenesis. To date, four members of the PBX family (PBX1, PBX2, PBX3, PBX4) have been identified to be involved in human cancers, but little is known about their role in colorectal cancer (CRC). The aim of this study was to determine their differential expression, prognostic role and function in CRC. Methods Molecular and overall survival (OS) data from 614 patients with CRC were obtained from the National Cancer Institute, Tissue Cancer Genome Atlas (TCGA) database. To investigate the differential PBX gene mRNA expression, we performed a comparative cancer to normal computational analysis in edgeR. To determine PBXs prognostic value, we conducted Kaplan-Meier survival analysis and COX regression, selecting 10-year OS as primary outcome. Lastly, to explore the effect of PBX4 in CRC cell growth and angiogenesis, we performed gene expression modulation experiments using a PBX4-overexpressing plasmid-vector. Cell proliferation and VEGFA angiogenic factor expression were defined as primary and secondary in vitro outcomes respectively. Results Among PBXs only PBX4 was significantly upregulated showing a 4-fold increase in CRC vs normal colon (p < 0.0001). Survival analysis showed that only high PBX4 mRNA expression was associated with increased risk for worse OS in patients with CRC (HR:1.3 95%CI:1-1.6, p = 0.02). Functionally, overexpression of PBX4 significantly increased CRC cell proliferation in vitro (p < 0.001) and markedly upregulated the expression of VEGFA (p < 0.0001). Conclusions Comprehensive analysis of the PBX gene family identifies that PBX4 may function as a novel oncogene and may promote angiogenesis through VEGFA in CRC.