Abstract PR-014: Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1

Abstract

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 contributes to PDAC’s distinctive chemotherapeutic resistance. Prior work demonstrated that inhibition of the Hedgehog (Hh) signaling using Smoothened (Smo) inhibitors relieved some of the local angiogenic suppression. However, the precise mechanisms through which the Hh pathway regulates angiogenesis has remained elusive. Subsequent studies evaluating different timepoints yielded conflicting data on the role of Hedgehog signaling in angiogenesis. In order to replicate the heterogeneity and spatial patterning of cells in pancreatic tumors, 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 tissues in 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 culture up to one week with good representation of multiple cell types. Studies in explants were complemented by work in the 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, which 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 target gene that effected these programs. Mechanistic studies in tumor explants reveal a complex, multi-step mechanism involving multiple cell types that led to suppression of angiogenesis in PDAC. These studies demonstrate how the tumor explant platform can elucidate complex intercellular signaling cascades and provide a candidate mechanism for the Hh-mediated suppression of angiogenesis in PDAC. Citation Format: Marie C. Hasselluhn, Amanda R. Decker, Alvaro Curiel Garcia, Carlo Maurer, Dafydd Thomas, Kenneth P. Olive. Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1 [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 PR-014.