Abstract B031: Targeting hyaluronic acid in pancreatic ductal adenocarcinoma uncovers novel therapeutic opportunities

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related deaths, with a five-year survival rate around 12%. In PDAC, cancer-associated fibroblasts (CAFs) play a vital role in promoting the desmoplastic and immunosuppressive tumor microenvironment (TME), and have emerged as relevant cancer targets. CAFs produce intratumoral hyaluronic acid (HA) whose accumulation induces high interstitial fluid-pressure (IFP) which can interfere with drug delivery. Moreover, HA has been linked with tumor escape from immune surveillance. Systemic administration of Hyaluronidase, via the PEGPH20 formulation, has reduced stromal HA, normalized IFP, and consequently improved the efficiency of the cytotoxic compound, gemcitabine, leading to increased survival in mice. In this study we have decided to eliminate HA by a different approach involving its synthesis rather than inducing its degradation. To this end, we have genetically targeted the three genes encoding HA synthases (Has1, 2, 3). Has1 and Has3 null alleles were generated by CRISPR technology in mouse embryos since they are nor essential for embryonic development. To eliminate Has2, we used existing conditional Has2lox alleles (Matsumoto et al. 2019, PMID XXXX) along an inducible allele, Rosa26-CreERT2, encoding an inducible Cre-ERT2 recombinase to allow the systemic ablation of the conditional Has2lox alleles in adult mice upon exposure to a Tamoxifen-containing (TAM) diet. These alleles were added to the standard KPF strain (KRas +/FSFG12V;P53F/F;Pdx1-FlpO) to determine the effect of HA elimination in tumor-bearing mice. Exposure of these adult animals to the TMA diet induced significant levels of HA depletion leading to reprogramming of tumoral, stromal and immune cells leading to significantly reduced tumor progression. Tumor cells were more differentiated as illustrated by higher expression of cytokeratin19 and additional epithelial cell adhesion molecules. Furthermore, these tumor cells displayed reduced proliferative capacity, mor limited EMT, migration and invasive capacity. Interestingly, they also exhibited upregulated Kras expression. At the stroma level, we observed less fibrotic tissue, decreased collagen deposition, reduced CAFs activation,and changes in the CAF populations, with high content of iCAFs (Inflammatory CAFs) and very low content in myCAFs (Myofibroblast CAFs). More importantly, we also observed infiltration of CD8+ T cells. Notably, HA depletion enhanced the efficacy of gemcitabine, the anti-CTLA-4 and the panras inhibitor darasonrasib, either alone or in combination of anti-CTLA-4. In summary, HA depletion in PDAC produced multiple changes at different levels that opens up new opportunities for therapeutic interventions. Citation Format: Pian Sun, Ángeles Durán, Federico Virga, María Diaz-Meco, Jorge Moscat, Carmen Guerra, Mariano Barbacid. Targeting hyaluronic acid in pancreatic ductal adenocarcinoma uncovers novel therapeutic opportunities [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_3):Abstract nr B031.