PTBP3 Regulates The Growth And Metastasis Of Colorectal Cancer By Promoting P53 Degradation Through UBE4A

Purpose: Colorectal cancer is one of the most common malignancies,ranking third among malignancies.Globally,there are about 1.1 million new cases of the disease and nearly 580,000 new deaths each year.Although there are more and more treatments for colorectal cancer,there is still no effective way to prevent colorectal cancer deaths.Therefore,it has become an urgent clinical,social and economic problem for us to study the mechanism of colorectal cancer.As a member of the PTB family of proteins,PTBP3 is an important RNA binding protein,whose functions involve alternative splicing,transcriptional activation and mRNA stability.Recent studies have confirmed that PTBP3 is overexpressed and play an important role in cancers,including colorectal cancer.This study intends to further verify the relationship between the expression level of PTBP3 in colorectal cancer and clinicopathology,as well as its influence on colorectal cancer and the potential mechanism.Methods:The expression level of PTBP3 in colorectal cancer and its relationship with clinicopathological data were explored by bioinformatic analysis combined with RT-q PCR and WB experiments.The function of PTBP3 on colorectal cancer were explored by CCK8,colony-forming assay,flow cytometeric analysis,transwell and tumor xenografts experiment.The downstream signaling pathways and target genes that PTBP3 may regulate in colorectal cancer were explored by bioinformatic analysis combined with RT-q PCR and WB experiments.The relationship between PTBP3 and downstream target gene UBE4 A 3-UTR region was explored by RNA stability assay,RNA binding protein immunoprecipitation assay,double luciferase reporter assay,RNA antisense purification assay,immunoprecipitation assay.The function of UBE4 A on colorectal cancer were explored by CCK8,colony-forming assay,flow cytometeric analysis,migration and transwell.The effects of PTBP3 and UBE4 A on P53 were investigated by RT-q PCR,WB and immunoprecipitation assay.Overexpression of UBE4 A in PTBP3 knockdown colorectal cancer cell lines was used to reverse the effect of PTBP3 on colorectal cancer function.Results: We showed that PTBP3 was upregulated in CRC and associated with poor prognosis.PTBP3 promoted the growth and metastasis of wild-type P53 colorectal cancer cell lines,but had no effect on mutant P53 colorectal cancer cell lines.PTBP3 regulates the expression of UBE4 A by binding to UBE4 A 3-UTR region to maintain the stability of UBE4 A mRNA.UBE4 A promotes the growth and metastasis of wild-type P53 colorectal cancer cell lines,but had no effect on mutant P53 colorectal cancer cell lines.UBE4 A mediates ubiquitination degradation of p53 protein by affecting MDM2-p53 signalin pathway.Overexpression of UBE4 A in PTBP3 knockdown colorectal cancer cell lines can partially reverse the effects of PTBP3 on the growth function of colorectal cancer.Conclusions:PTBP3 is overexpressed and correlated with a poor prognosis and plays an oncogenic role,contributing to CRC growth.Additionally,PTBP3 is closely related to the ubiquitin-mediated proteolysis signaling pathway-related gene UBE4 A and may mediate its mRNA stability to regulate its expression.Furthermore,we demonstrate for the first time that UBE4 A knockdown inhibits CRC growth and metastasis,which may be associated with p53 stability.Collectively,our results indicate that the PTBP3/UBE4A/p53 axis may be a prognostic marker and therapeutic target in CRC,potentially providing new insight into CRC progression and treatment.