Identification of RB1 Gene as a Immune-Related Prognostic Signature Based on Tumor Mutation Burdens in Bladder Cancer

Abstract

Background: Bladder cancer (BC) is known as the eleventh most common malignant tumor all over the world, for either males or females. Developing effective regimens targeting more promising biomarkers aiming for better prognosis are required. Immune checkpoint inhibitors (ICI) have been demonstrated as a prospective and practical means to resist cancers. Theoretically, adequate infiltration of immune cells indicates more immunotherapy targets and may promise better prognosis.Methods: Full transcriptome data (n=433), clinical information (n=581) and mutation sequencing (n=412) were obtained freely from The Cancer Genome Atlas and independent mutation sequencing data of 101 samples were acquired from International Cancer Genome Consortium. Statistical processing was conducted using R packages with R x64 4.0.2. Gene biologically functional research was performed with gene set enrichment analysis (GSEA) based on Kyoto Encyclopedia of Genes and Genomes (KEGG) database. 22 types of immune cell infiltration were assessed and calculated in 398 samples of BC tumors.Results: Tumor mutation burdens (TMB) of mutant type groups were higher than wild type groups for 19 genes, except for FGFR3 and CREBBP verifying that genomic mutation associates positively with TMB in BC tumor. Kaplan-Meier analysis showed high mutation frequency on RB1 had a negative effect on prognosis of BC patients and RB1 was an independent prognostic factor (p=0.004, HR=1.776) in BC. It was also demonstrated that RB1 mainly participate in singling pathways of cell proliferation and cell cycle. Proportions and correlation of 22 types of immune cells in 433 samples were determined. Immune cells with similar function are inclined to co-exist in tumor microenvironment of BC. Among them, regulatory T cells (Tregs) were detected as a negatively correlated type immune cell to mutation of RB1 that probably increases the incidence of tumor immune escaping in BC.Conclusion: RB1 can be identified as an independent prognostic predictor, and there is a chance for contribution to poor overall survival as the mutation occurs. What's more, mutation of RB1 also functions as a biomarker that represses the infiltration of Tregs, increasing the incidence of tumor immune escaping in BC.