Comparative bioinformatical analysis of pancreatic head cancer and pancreatic body/tail cancer.

This study is to analyze differentially expressed genes (DEGs) and mutation signatures of pancreatic head cancer and pancreatic body/tail cancer. Pancreatic Adenocarcinoma (PAAD) RNA-seq data, mutation data and clinical data were downloaded and collected from The Cancer Genome Atlas (TCGA), FireHose and CBioPortal. According to the anatomic location, the patients were divided into 146 cases of pancreatic head cancer and 28 cases of pancreatic body/tail cancer. Then survival analysis was performed by Kaplan-Meier and log-rank test. Furthermore, DEGs were screened by R package Deseq2. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein-protein interaction (PPI) were then carried out by DAVID and String. Online tool TIMER was used to analyze the immune cells infiltration. R package maftools and GenVisR were applied to analyze frequently mutated genes and mutant-allele tumor heterogeneity (MATH) of PAAD. Survival of patients with pancreatic body/tail cancer was better than those with pancreatic head cancer (median survival, 24.05 vs 19.45 months, p = 0.048). And 496 significant DEGs (|log2 FoldChange| > 1.5,false discovery rate (FDR) < 0.05) were identified, including 253 downregulated genes and 243 upregulated genes. And there were 13 Go terms (4 biological processes, 6 cellular components and 3 molecular functions) and 3 KEGG pathways (Pancreatic secretion, Fat digestion and absorption, Protein digestion and absorption) (FDR < 0.05). B cells and CD4 + T cells infiltration were more significant in pancreatic head cancer. MATH scores of pancreatic body/tail cancer were higher than pancreatic head cancer, while χ2 test of top 10 frequently mutated genes showed little difference between them. There were prognostic and genetic differences between pancreatic head cancer and pancreatic body/tail cancer. PAAD originated from different location may have different biology natures and should not be treated with same strategy.