Stromal Hedgehog Signaling Is Associated with Favorable Outcomes in Pancreatic Cancer

Aberrant activation of the Hedgehog (Hh) signaling pathway can be observed in various malignancies, particularly in stroma-rich tumors like pancreatic ductal adenocarcinoma (PDAC). In PDAC, Hh signaling is thought to foster an abundant stroma, making it an appealing target for stoma-targeted therapy. However, the use of Hh antagonists in the clinic has thus far not been successful. To reassess the clinical merit of Hh-targeted therapy in PDAC, we sought to better characterize the role of Hh signaling in tumor-stroma crosstalk. Here, we show that Hh ligands are not prognostic per se in PDAC, despite being associated with the favorable classical molecular subtype. Perturbing Hh ligand expression in PDAC cells can effectively alter their trans-signaling capacity but does not impact tumor growth in vivo. However, co-injecting PDAC cells with Smo-proficient MEFs resulted in a significant reduction in xenograft growth, suggesting that Hh-related effects on tumor growth are largely mediated through the stroma. By analyzing transcriptomic sequencing data from co-cultures, comprising human PDAC cells and mouse fibroblasts treated with a Hh-blocking antibody, we could identify stromal hits that are responsive to Hh ligands. We then leveraged the obtained set of genes to allow patient stratification based on stromal response to Hh ligands. We believe that a subset of PDAC patients may benefit from the use of Hh-targeted therapies and thereby encourage the use of our stratification tool to guide their use in PDAC clinical care.