Abstract PO-068: Cholesterol auxotrophy promotes the expansion of centroacinar cells giving rise to the basal subtype of pancreatic adenocarcinoma
Authors: Kotliar Michael , Surumbayeva Aizhan , Gabitova Linara , Peri Suraj , Restifo Diana , Cai Kathy Q. , Barski Artem , Astsaturov Igor 
Published: November 2021

Abstract
Gene expression analyses established at least two molecular subtypes of pancreatic adenocarcinoma (PDAC), the classical (or glandular), and the basal (or mesenchymal), each of which is associated with distinct prognoses and sensitivity to chemotherapy. It remains unclear, however, whether the basal carcinoma cells arise from a separate cell-of-origin, or are emerging from the pre-existing well-differentiated “classical” PDAC cells. To distinguish these alternatives, we conducted single-cell transcriptome analyses and virtual lineage tracing comparing cellular populations at pre-malignant stages in basal versus classical PDAC mouse models. We previously reported that chemical or genetic inhibition of the cholesterol biosynthetic pathway in KrasG12D; Trp53 (KPPC) mice predisposes to basal rather than glandular PDAC development because of the pancreas-specific increased sterol response element-binding protein 1 (SREBP1) activity and TGFβ signaling that induces cancer cell stemness and the EMT (PMID: 32976774). Pancreas-selective knockout of a conditional allele of cholesterol pathway gene, Nsdhl (NAD(P)-dependent steroid dehydrogenase-like), renders pancreatic epithelial cells cholesterol auxotrophs and drives basal PDAC in the majority of animals (KPPCN mice). At 5-6 weeks of age, grossly and microscopically tumor-free pancreatic tissues were selected for single-cell isolation and single-cell RNA sequencing (scRNA seq) using the 10X platform. After standard filtering and sample normalization procedures, downstream analyses included identification of relevant cell clusters using Seurat, lineage tracing algorithms, and in silico modeling of autocrine and paracrine signaling interactions between subsets of PDAC and non-malignant cells. Our key findings are as follows: 1) premalignant KPPCN pancreata exhibit a massive expansion of cancer-associated fibroblasts (CAFs) of predominantly inflammatory differentiation (iCAFs); 2) despite relatively fewer ADM and PanIN pre-malignant lesions in KPPCN compared to KPPC, scRNA seq identifies the significant expansion of epithelial cells with features of centroacinar and stem-like cells (increased expression of Aldh1a2, Nes, Sox9, Ly6a, Cxcl12, and Met); these centroacinar-like cells, while retaining epithelial identity (Epcam, Cdh1), also exhibit features of pluripotency by co-expression of Ins2 and other stem cell markers; 3) alignment with basal PDAC (KPPCN) and classical (KPPC) carcinoma cell populations strongly suggests the continuity of clonal evolution of the centroacinar-like cells towards the basal PDAC. While our genetic model does not recapitulate the multiple alternative pathways leading to basal PDAC development, cholesterol auxotrophy via SREBP1 may be a factor governing the expansion of undifferentiated precursors, which via interactions with cancer-promoting iCAFs, drive basal PDAC development.
Citation Format: Michael Kotliar, Aizhan Surumbayeva, Linara Gabitova, Suraj Peri, Diana Restifo, Kathy Q. Cai, Artem Barski, Igor Astsaturov. Cholesterol auxotrophy promotes the expansion of centroacinar cells giving rise to the basal subtype of pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-068.