Tumor-Specific Nascent Nine-Peptide-Epitopes Prediction and Bioinformatics Characterization in Human Colorectal Cancer

Abstract

Background/Aims: Neoantigens are peptides produced by translation of mutant exons and existed in tumor tissues instead of normal tissues, thus, we desired to investigate the antigenic peptide epitopes of cancerspecific neoantigen, to detect the affinity of the nonapeptide with the corresponding Human Leukocyte Antigen I (HLA I) allele molecule, in order to understand the relationship of mutant exon genes of Colorectal Cancer (CRC) patients and the drive genes that are currently known for tumorigenesis of CRC. Methods: The next generation sequencing (NGS) method was used to detect the whole genome sequence and HLA I allele types of tumor tissues and adjacent tissues of 5 CRC patients. pVAC-Seq was applied to identify the nascent nonapeptides generated from exon mutations. The affinity of polypeptides with respective HLA I molecules in CRC was calculated by using NETMHC 4.0 Server. The molecular localization, molecular function, and signal pathways of mutant genes in 5 CRC patients were performed by FunRich 3.1.3 software. The TIMER website was applied to predict the analysis of intratumoral immune cell infiltration associated with the gene mutations in 5 CRC patients. Results: Fifty-six tumor-specific neo-nonapeptides were predicted from 54 different exon gene mutations. The 56 tumor new nonapeptide sequences were different from the shared motif of the HLA I allele. We explored that the tumor-specific nascent nonapeptide mainly bound to HLA-A.02*03, HLA-B.58*01 and HLA-B.11*01, and the affinity analysis results suggested that 14 of the nonapeptides had strong binding force, 20 nonapeptides had weak binding force, and 22 nonapeptides had no binding force. 54 mutant exons of 5 CRC patients were chiefly located in Leading edge membrane, Fanconi anaemia nuclear complex, and Azurophil granule. The molecular functions of these genes were involved in DNA-directed DNA polymerase activity, Vitamin or cofactor transporter activity, and Receptor signaling protein tyrosine kinase activity. 54 gene mutations had key roles in Translesion synthesis by Pol zeta, Translesion synthesis by DNA polymerases bypassing lesion on DNA template, and DNA Damage Bypass. We found that the mutant FMN2 had more infiltration of CD8+ T cells in the tumor than the wild type, and the mutant ZNF717 had more infiltration of CD8+ T cells and neutrophils in the tumor than the wild type, the difference was statistically significant. Conclusion: This study provides a preliminary result to illustrate that the prediction and bioinformatics feature of tumor-specific new nine-peptide-epitopes in CRC. It is hoped that the cancer-specific neoantigen will be used for adjuvant immunotherapy after radical surgery of colorectal cancer, and the mutant genes of CRC can also be used as landmarks for postoperative recurrence and metastasis of colorectal cancer.