Abstract 3648: Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1

Abstract Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an extremely heterogeneous tumor microenvironment (TME) paired with a sparse and compromised vascular network. These features of the TME shape drug responses and contribute to PDAC’s distinctive chemotherapeutic resistance. Prior work demonstrated that inhibition of the Hedgehog (Hh) signaling pathway using Smoothened (Smo) inhibitors led to increased angiogenesis. However, the precise mechanisms through which the Hh pathway regulates angiogenesis has remained elusive and subsequent studies with different agents and timepoints yielded conflicting data. Frustratingly, the phenotype could not be recreated in simple co-culture models. In order to maintain the cellular heterogeneity and spatial organization that characterizes PDAC, we developed a novel tumor explant system for short-term cultures of both murine and human PDAC. Briefly, we cultured intact 300 μm slices of PDAC tissue on a modified gelatin platform system with a novel culture medium informed by the metabolic composition of PDAC tumor interstitial fluid. This system replicates some of the nutrient/waste gradient of PDAC and enables tumors to be cultured up to one week maintaining the representation of multiple cell types. Studies in explants were complemented by work in the Kras-LSL.G12D/+, p53-LSL.R172H/+, Pdx1-Cre (KPC) genetically engineered model of PDAC. Comparison of short versus long-term Smo inhibition in KPC mouse pancreatic tumors revealed a robust increase in vessel density in short-term treatment that is lost at later timepoints. Studies in murine and human PDAC explants employing different Smo inhibitors demonstrated increased endothelial tip cell formation upon two days of treatment, resulting in increased vessel density after four days. Computational analyses of human PDAC single cell RNAseq data identified candidate cellular subsets potentially involved in the signaling cascade. RNAseq of pre- and on-treatment tumor samples from KPC mice identified Wif1 as a candidate Hh pathway target gene that effected these programs. Mechanistic studies in tumor explants reveal a complex, multi-step mechanism involving several cell types that led to suppression of angiogenesis in PDAC. These studies both provide a candidate mechanism for Hh-mediated angiosuppression and also demonstrated how the tumor explant platform can elucidate complex intercellular signaling cascades in both murine and human PDAC. Citation Format: Marie C. Hasselluhn, Amanda R. Decker, Alvaro Curiel Garcia, Carlo Maurer, Dafydd H. Thomas, Kenneth P. Olive. Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3648.