Potential Predictive Value Of TP53/RB1 Mutation Statuses And Tumor Immunophenotype For Response To PD-1 Blockade Immunotherapy In Urinary Bladder Cancer

Background:With an estimated 81,190 new cases and 17,240 deaths are estimated to occur in United States,bladder cancer has become one of the most common and lethal cancers worldwide.In China,although the incidence and mortality rates are relatively low,the incidence rate has increased in recent years,with an estimated 80,500 new cases and32,900 deaths annually.The recent attempt of immune checkpoint inhibitors targeting the programmed cell death 1(PD-1)and PD-1 ligand(PD-L1)has revolutionized the management of metastatic urothelial carcinoma.However,the identification of predictive biomarkers that could discern patients who could benefit from checkpoint immunotherapy remains an ongoing challenge.We carried out an integrated analysis based on multiple-dimensional types of data,including clinical,genomic and transcriptomic data from cohorts of bladder cancer patients to identify clinically useful biomarkers for anti–PD-1/PD-L1 therapy.Methods:Multiple-dimensional types of data,including clinical,genomic and transcriptomic data bladder cancer patients were retrieved from online database.The RNA sequencing profiles,somatic mutation and PD-L1 amplification data of bladder cancer were analyzed.Bladder cancer samples belonged to four tumor microenvironment immune types(TMITs)as follows:type I,with expressions level of PD-L1 and CD8A higher than their median values,respectively;type II,with expressions level of PD-L1 and CD8A lower than their median values,respectively;type III,with higher PD-L1 expression and lower CD8A expression in contrast to their median values,respectively;and type IV,with lower PD-L1 expression and higher CD8A expression in contrast to their median values,respectively.Gene set enrichment analysis was performed to associate the potential signature of genes with the TP53 or RB1 mutation status and TMITs.Results:1)Our research demonstrated that TP53/RB1 mutations prominently increased PD-L1 expression and facilitated CD8~+T-cell infiltration,and accompanied with a higher proportion of double positive PD-L1/CD8A and increased mutational burden than corresponding wild-type groups.Specifically,TP53 mutation was significantly correlated with high somatic mutations,high rate of transition/transversion(Ti/Tv),high rate of C>G transverse and high smoking index(pack/year).Further analysis concentrated on the potential molecular mechanism found that TP53/RB1 mutations altered a group of genes involved in cell-cycle regulating,DNA replication and damage repair.TP53 and/or RB1 mutation patients obtained a significantly prolonged progression free survival compared with wildtype patients(6.59 months vs.2.12months,P=0.006).Overall survival was also found to be longer in bladder patients with TP53 and/or RB1 mutation(14.01 months vs.8.10 months,P=0.032).2)TIMT subtypes were not significantly associated with overall survival or disease free survival in urothelial cancer.TMIT I facilitates CD8+T-cell infiltration and activates T-effector and interferon gamma(IFN-?)associated gene signature.The number of somatic mutations,cytolytic activity,IFN-?mRNA expression and TIGIT mRNA expression in TMIT I was remarkably higher than those in other TMIT groups.Our results showed a high rate of C>T transversion and a high rate of Ti/Tv in TMIT I bladder tumors.The RB1 mutation was significantly associated with TMIT I bladder cancer and be significantly co-occurring with the TP53 mutation.However,FGFR3mutation and TP53 mutation were mutually exclusive in TMIT II bladder tumors.More importantly,different amino acid changes by FGFR3/RB1 mutations were also found between TMIT I and TMIT II bladder cancer,such as amino acid changes in“Immunoglobulin I-set domain(260-356)”and“Protein tyrosine kinase(472-748)”.We also detected 9 genes as significantly cancer-associated genes in TMIT I bladder cancer,of which,RAD51C has been reported to play an important role in DNA damage responses.Further analysis concentrated on the potential molecular mechanism found that TMIT I was significantly associated with anti-tumor immune-related signaling pathway,and kataegis was present on chromosome 21 in TMIT I bladder tumors.Conclusions:1)We discovered a prominent significance of TP53 and RB1 mutations in boosting PD-L1 expression,facilitating the T cell infiltration,and augmenting tumor immunogenicity.2)We provided evidence that TP53/RB1 mutations might represent a pair of useful predictive biomarkers of response to anti–PD-1/PD-L1 therapy in urothelial carcinoma.3)The classification of bladder cancer into four TMITs on the bases of the PD-L1expression and the CD8+CTLs statuses is an appropriate approach for bladder tumor immunotherapy.4)TMIT I(high PD-L1/high CD8A)is significantly correlated with more somatic mutation burden,and facilitates CD8+T-cell infiltration and activates T-effector and IFN-?associated gene signature.