Abstract B093: Alcoholic chronic inflammation driven CREB mediates acinar-to-ductal reprogramming and promote neoplastic progression
Authors: Mehra Siddharth , Srinivasan Supriya , Bianchi Anna , Dosch Austin , Singh Samara , Garrido Vanessa , De Castro Silva Iago , Krishnamoorthy Varunkumar , Jinka Sudhakar , Datta Jashodeep , Merchant Nipun B. , Nagathihalli Nagaraj 
Published: January 2024

Abstract
Introduction: Alcoholic chronic pancreatitis (ACP) is a progressive fibroinflammatory disease of the pancreas often characterized by extensive acinar cell injury leading to acinar-to-ductal metaplasia (ADM). However, the impact of ADM associated with ACP on the acceleration of oncogenic mutant Kras (Kras*)-driven tumorigenesis remains poorly understood. In this study, we aimed to unravel the underlying mechanism by which ACP-induced dysfunction and with Kras*, leads to the development of irreversible ADM and premalignant lesions that establish a tumor-permissive microenvironment for the emergence of high-grade pancreatic intraepithelial neoplasia (PanINs). Methods: ACP mice model was developed in acinar cell-specific Ptf1aCreERTM/+, Ptf1aCreERTM/+; LSL-KrasG12D/+ (KC), and genetic ablation of cyclic AMP response element-binding protein 1 (CREB) in KC (KCC−/−) mice crossed with or without R26R-EYFP reporter mice, and these mice were fed with alcohol-enriched or regular diet along with repetitive caerulein administration. Lineage tracing studies and acinar explants were employed to investigate the fate of adult acinar cells. ACP-induced mice were subsequently euthanized either 3 days or 21 days after ACP induction, the pancreas was collected for immunohistochemical analysis and examined for ADM, PanINs, fibrosis, and inflammation. To gain insights into the molecular mechanisms; kinase array analysis, acinar cell explant culture, Western blot and qPCR-based studies were conducted. Additionally, single-cell RNA sequencing (scRNA-seq) was employed to investigate cell-specific transcriptomic changes focusing on distinct cellular compartments. Results: Lineage tracing studies showed that ACP-induced ADM stems from direct transdifferentiating adult acinar cells to a ductal phenotype in Kras* mice. ACP induction with Kras* cooperatively provided a sustained Kras - dependent oncogenic program in inflammation-induced metaplastic progenitor cells. The upregulation of CREB accompanied this process of malignant transformation. CREB activation persists even after ACP withdrawal in KC mice compared to Ptf1aCreERTM/+ mice without mutant Kras. Acinar-specific CREB ablation attenuated advanced PanIN lesion development, impeding tumor progression in Kras* mice. Additionally, it reduced inflammation-induced tissue injury and facilitated acinar cell recovery. ScRNA-seq analysis revealed gene enrichment favoring acinar cell homeostasis and downregulation of ductal gene signatures in KCC−/− mice, further emphasizing CREB's pivotal role in modulating these cellular processes. Conclusion: Our findings demonstrate that Kras* sustains an irreversible ADM and PanIN through continuous activation of CREB. Additionally, we have identified that CREB mediates an oncogenic transcriptional program that drives tumor progression in the context of inflammation-induced disease. Importantly, our study reveals that ACP synergistically cooperates with Kras*-driven activated CREB, promoting the progression of ADM toward high-grade PanINs.
Citation Format: Siddharth Mehra, Supriya Srinivasan, Anna Bianchi, Austin Dosch, Samara Singh, Vanessa Garrido, Iago De Castro Silva, Varunkumar Krishnamoorthy, Sudhakar Jinka, Jashodeep Datta, Nipun B. Merchant, Nagaraj Nagathihalli. Alcoholic chronic inflammation driven CREB mediates acinar-to-ductal reprogramming and promote neoplastic progression [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B093.