Abstract A013: Tumor microenvironmental metabolites regulate cancer-associated fibroblast heterogeneity

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a prominent desmoplastic response with a high abundance of cancer-associated fibroblasts (CAFs). CAFs are a functionally and transcriptionally heterogeneous population of cells and include inflammatory CAFs (iCAFs), thought to promote tumor growth via the secretion of cytokines and chemokines, as well as myofibroblasts CAFs (myCAFs), thought to restrain tumor growth via the secretion of extracellular matrix. The iCAF and myCAF states are plastic. Preventing the interconversion of CAF populations could have significant clinical benefits, but how this plasticity is regulated is largely unknown. Cytokines like IL1a and growth factors like TGFb are required but not sufficient to induce changes in the CAF state. Instead, their effect is dependent on the presence of other environmental factors. We recently demonstrated that cancer cell-derived cytokines synergize with hypoxia to induce a transition from a myCAF- towards and an iCAF state, indicating that metabolic factors in the TME can modulate the CAF state in combination with signaling molecules. To identify other extracellular metabolic factors that synergize with cytokines in regulating CAF plasticity, we performed a high-content screen using a human blood chemical library in combination with our recently developed fibroblast reporter (FIRE) system incorporating iCAF (IL6-EGFP) and myCAF (Acta2-DsRed) transcriptional reporters. Out of hundreds of compounds, we identified and validated one purinergic metabolite that synergizes with the cytokines IL1a and TNFa to promote IL6 expression in a time- and dose-dependent manner. Intriguingly, previous studies have reported that this metabolite accumulates in the PDAC TME to a high micromolar range. Metabolite and cytokine treatment together induce pancreatic stellate cells (PSCs) to upregulate production and secretion of pro-inflammatory cytokines including IL6, CXCL1 and LIF. Pretreatment of PSCs with physiological concentrations of this metabolite is sufficient to alter the fibroblast state and to promote tumor growth when co-injected with PDAC cells in vivo. Mechanistically, we find that this metabolite acts by activating non-canonical purinergic signaling. These findings support the idea that TME metabolites can alter PDAC progression by regulating CAF heterogeneity through synergy with cancer cell-derived signaling molecules.