Research Of Predictive Markers And Its Influencing Factors For Colorectal Cancer Immunotherapy

IntroductionColorectal cancer(CRC)is a common digestive system tumor,its new cases account for approximately 10.2%of new global cancer cases.Currently,immune checkpoint inhibitor(ICI)has showed unprecedented clinical activity in colorectal cancer,patients with high microsatellite instability(MSI-H)and defective mismatch repair(dMMR)are the dominant population of ICI treatment,but even for the dominant population,the objective response rate(ORR)of them treated by single or combination therapy is only about 40-50%,and there are still other factors that affect the effect of ICI.Recently,KEYNOTE-177 prompted ICI emerged in the neoadjuvant treatment of CRC,the NICHE phase II clinical trial was pleasantly surprised to find that microsatellite stabilized CRC benefited 25%of neoadjuvant immunotherapy,it can be seen that there are indeed other factors affecting susceptibility of ICI.To date,tumor mutational burden(TMB)has been found to screen the beneficiaries of ICI treatment of CRC,and age,sex and specific gene mutations have also been found to be predictive markers of ICI,but these are controversial and need to be explored in the field of ICI treatment of CRC.ObjectiveThe purpose of this study was to explore the predictive effects of sex,age,and gene mutations on CRC patients treated with ICI through bioinformatics analysis,and explore whether other immune factors such as tumor immunogenicity and immune microenvironment in addition to MSI,affect the effect of ICI,and how to affect the above prediction markers.MethodsWe first collected a CRC clinical cohort receiving ICI from the Memorial Sloan Kettering Cancer Center(MSKCC)in the United States.This cohort contains clinical baseline characteristics,survival data,and somatic mutation data.Subsequently,through univariate Cox regression analysis,Kaplan-Meier survival analysis and the log-rank test,the above clinical characteristics data and somatic mutation data were used to initially identify the age,sex,and specific mutation gene types related to the prognosis of immune checkpoint inhibitor therapy,and determine the predictive markers.After that,the influence factors of various predictive markers on ICIs was analyzed.Besides CRC clinical chort treated by ICI of MSKSS outside,we also adopt the clinical data,somatic mutation data,neoantigen data and transcriptome sequencing data of CRC samples in The Cancer Genome Atlas(TCGA),and analysis the relationship between the above predictive markers and the immunogenicity such as TMB and neoantigen load,gene expression level related to immune response,and the number of mutations in the DNA damage and repair(DDR)pathways.Then,we analysis the infiltration types of immune cells in the tumor microenvironment(TME)of different prognostic factors by CIBERSORT web portal(http://cibersort.stanford.edu/).Finally,"Kyoto Encyclopedia of Genes and Genomes(KEGG)",Gene Ontology(GO)and REACTOME database are used to explore the immune related pathway by Gene Set Enrichment Analysis(GSEA).Except CIBERSORT and GSEA need to be carried out on the corresponding website or software,all other analyses are done in R software(version 3.6.1)Results1.prognostic factors of ICI in treatment of CRCOur study screened 109 samples in MSKCC and 511 cases in the TCGA database.And we found that TMB>11 mutation/Mb(TMB-high),age>65 years,male,mutations in genes RNF43,CREBBP,NOTCH3,PTCH1,CIC,DNT1,and SPEN were significantly associated with longer OS of colorectal cancer treated by ICI,while the mutations in genes APC and TP53 were significantly associated with poorer OS.2.Influencing mechanism of various prognostic factors of ICIThrough a series of bioinformatics analysis of 109 CRC samples receiving ICI treatment in MSKCC and 511 CRC samples in TCGA,it is found that the reason why good prognostic markers bring better survival benefits to patients with CRC may be related to higher immunogenicity such as TMB and neoantigen load,the immune phenotypehigh with highly expression of gene related to immune response,highly infiltrating immune-active cells such as CD8+T cells,active immune-active pathways,and DNA damage repair pathways with an increased number of mutations.ConclusionOur study illustrated a comprehensive prognostic factors for the ICI treatment of CRC patients by bioinformatics analysis,from clinical characteristics such as age and sex to specific gene mutations,and found that tumor immunogenicity,immune microenvironment characteristics,etc.can affect the efficacy of ICI in the treatment of CRC and thus affect the predictive role of predictive marker,providing some new ideas for immunotherapy in colorectal cancer patients.In order to further confirm the predictive markers of ICI,molecular biology studies and prospective clinical trial studies are needed.