HPB SO33 - Transcriptomic characterisation of the diabetogenic pancreatic ductal adenocarcinoma phenotype

Abstract Background New-onset diabetes mellitus (NOD) can manifest as a consequence of pancreatic ductal adenocarcinoma (PDAC), although not all PDAC patients develop NOD. For many patients, hyperglycaemia begins 3 years prior to PDAC diagnosis, with 30% of PDAC patients experiencing NOD by the time their cancer is diagnosed. The mechanisms underlying the onset of diabetes mellitus (DM) in PDAC and its consequences for disease development, detection and treatment are not well understood. The aim of this study was to characterise the transcriptomic differences between PDAC tumours that present with NOD compared to those that do not. Method Eight tumour samples from patients undergoing surgery for PDAC (4 without DM (HbA1c <35), 4 with NOD (HbA1c >65, within 3 years of cancer diagnosis) underwent single cell-RNA sequencing (scRNAseq) after taking intra-operative biopsies using Chromium 10X Genomics technology. Unique cell clusters were identified using CellRanger and cell types annotated using scATOMIC and singleR datasets. Manual annotation was undertaken when results were not agreeable after consulting the literature. Differential expression between groups was performed using DESeq2. Significant genes were identified as having a log2 fold-change >1.5 and p<0.05. Gene set enrichment was performed using Reactome. Analysis was conducted in RStudio. Results Single cell suspensions were created with a mean cell count of 1.2 million cells and a mean viability of 90%. PDAC cells and the full complement of tumour microenvironmental cells were recovered. Significant differential expression was seen in the PDAC cells themselves, CD4+ cells, macrophages, mast cells and fibroblasts. Cancer associated fibroblasts (CAFs) seemed not to differ. PDAC cells with NOD seemed to be enriched in MYC oncogenes whereas those without DM seemed to be enriched in KRAS mutations. There was a mixture of “basal” and “classical” transcriptional subtypes between the two groups. Conclusion Differences between diabetogenic PDAC and non-diabetogenic PDAC have been observed at the transcriptional level. Diabetogenic tumours seem to be promoted by MYC oncogenes and be more inflammatory than non-diabetogenic tumours. These findings require validation which will be done on independent samples using spatial transcriptomics to allow endocrine-exocrine crosstalk to be determined. Understanding the molecular pathways in diabetogenic pancreatic tumours could enhance future strategies to detect PDAC earlier and to target diabetes-associated vulnerabilities for therapeutic purposes.