Abstract 6818: Obesity-mediated perineural invasion promotes PDAC tumorigenesis
Authors: Mayengbam Shyamananda Singh , Alam Aftab , Senchanthisai Sharon , Bektas Irmak , Dey Prasenjit 
Published: March 2024

Abstract
Obesity is a modifiable host factor that has been reported to increase the risk of pancreatic ductal adenocarcinoma (PDAC) by ~60% and the mortality by two-fold, however, the exact mechanisms by which obesity enhances PDAC aggressiveness is incompletely understood. Given that nearly 74% of U.S. adults are overweight or obese (US Center for Disease Control), resolving the complex association between obesity and PDAC may unveil new targets for prevention and/or intervention to decrease incidence and improve outcomes. The prevailing notion is that obesity-induced tumor in situ factors (i.e., oxidative, hypoxic, nutrient, and biochemical) play crucial roles in enhancing cancer cell fitness and survival. However, these concepts have yet to lead to the identification of any actionable target in patients, with obesity-related cancer in general and PDAC in particular. Prior studies and our preliminary data show the presence of a distinctive tumor immune profile in PDAC models under conditions of obesity, which encompasses immune suppressive myeloid and type 2 immune cells, namely M2-like tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs), that inhibit effector CD8+ T cell expansion and function enabling PDAC progression. However, the genesis of this ‘type 2 immune cell’ dominant tumor-immune microenvironment (TIME) of obesity-driven PDAC remains to be fully understood. This led us to take a holistic approach utilizing multiple genetically engineered mouse models (GEMMs), pharmacological inhibitors, transcriptomic analysis (RNA-seq, spatial transcriptomic, and scRNA-seq), fresh PDAC patient samples, and imaging technologies (confocal microscopy) to understand the molecular mechanisms. Our novel mechanistic study using some of the above-mentioned tools shows that obesity-driven PDAC has significantly higher perineural invasion (PNI) that enhances PDAC progression. We found that sympathetic nerve terminals (of the PNI) via neurotransmitter release control the expression of integral cytokines that cause a dramatic remodeling of the TIME. Specifically, the PNI-mediated neuro-adrenergic signaling activates β2-adrenergic receptor (β2-AR) on PDAC cells, leading to increased tumor cell production/proliferation and secretion of the ‘alarmins’ IL-33 and IL-1β. Importantly, we showed that mitigation of adrenergic signaling using two separate approaches: (i) pharmacological antagonists of β2-ARs (β-blockers), and (ii) the use of a thermoneutral model leads to substantial abrogation of obesity-mediated tumor progression. These, and other key data raise the provocative question that reducing adrenergic signaling-dependent IL-33 expression and release favor a pro-inflammatory TIME and significantly increase patient survival in obesity-driven PDAC.
Citation Format: Shyamananda Singh Mayengbam, Aftab Alam, Sharon Senchanthisai, Irmak Bektas, Prasenjit Dey. Obesity-mediated perineural invasion promotes PDAC tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6818.