Immune-related somatic mutation genes are enriched in PDACs with diabetes

The bidirectional interaction between pancreatic cancer (PanCa) and diabetes has been confirmed by epidemiological studies, but until now, the underlying molecular mechanisms for this connection is not fully understood yet. Here, we analyzed the clinical and genomic data of 26 pancreatic ductal adenocarcinoma (PDAC) patients without diabetes, and six diabetic PDAC patients, whose tumors underwent targeted next-generation sequencing (551 cancer-related genes included). Ingenuity Pathway Analysis (IPA) was performed to investigate genetic alterations and biological consequences associated with PDACs with or without diabetes. We identified 345 somatic mutations of 153 genes in test cohort and a positive association between diabetes duration and somatic mutation burden. KRAS, TP53, and SMAD4 were the top3 commonly mutated genes at a similar frequency compared to the Cancer Genome Atlas (TCGA) data. Several novel but infrequent mutations in other genes (MDC1, PRB2, and PRB4) were also found. Besides, 13 mutated genes (PIK3CD, SNCAIP, IRF4, HLA-A, NOTCH4, PIM1, ETV6, B2M, CD70, PRDM14, TGFBR1, FLT1, and PARP2) were uniquely found in the diabetic group, mainly involved in immune-related pathways. Further targeted sequencing of these genes in an independent validation cohort (n = 50) revealed significant enrichment in the diabetic group (n = 18, P = 2.6964E-08). Long-standing diabetes (≥3-year duration) may induce increasing somatic mutations with time, facilitating tumor initiation. Gene mutants associated with immune-related pathways could be used to distinguish the diabetic PDAC patients from the non-diabetic cases and allow more selective treatment.