Abstract A019: Tumor Nutrient Stress Regulates Cancer-associated Fibroblast Heterogeneity

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer type with a 5-year survival rate of only 13%. PDAC is unique in that up to 90% of the tumor bulk is comprised of a dense desmoplastic stroma. Enriched within PDAC’s extensive stroma are cancer-associated fibroblasts (CAFs). CAFs orchestrate tumor progression through the secretion of signaling molecules that impact cancer and immune cell function, and extracellular matrix proteins that remodel the surrounding stroma. CAFs are functionally and transcriptionally heterogeneous, with three distinct subtype classifications: myofibroblastic (myCAF), inflammatory (iCAF), and antigen-presenting (apCAF). In PDAC, an increased iCAF to myCAF ratio has been associated with worse clinical outcomes; however, efforts to selectively target CAF populations have been met with the challenge of CAF plasticity. A better understanding of the mechanisms underlying CAF state decisions is required before pro-tumor CAFs can be targeted. A key feature of PDAC is impaired perfusion, which leads to regions of hypoxia and altered nutrient availability; however, the significance of this unique metabolic environment to CAF state remains unknown. It has been reported that nutrient stress within the tumor microenvironment directly impacts cancer cell state leading to targetable metabolic adaptions, but how these same stresses affect the CAFs that share this microenvironment have been overlooked. To investigate how the altered nutrient availability of PDAC impacts CAFs, we acclimated pancreatic stellate cells (PSCs), a precursor CAF, and patient-derived primary PDAC CAFs to culture in tumor nutrient-relevant media. Characterization of these cells by high-dimensional flow cytometry and RNA-sequencing has revealed that the nutrient environment is sufficient to alter CAF state. CAFs in conditions of tumor nutrient stress are enriched for inflammatory signatures, along with higher expression and secretion of several potent cytokines and chemokines. Changes in CAF state induced by tumor nutrient stress are reversible, highlighting nutrient availability as a dynamic regulator of CAF plasticity. Importantly, nutrient-stressed CAFs with inflammatory features are present in both murine and human PDAC tumors. Further, co-injection models have demonstrated that these tumor-like nutrient conditions are sufficient to promote tumor growth in vivo. This work demonstrates the importance of the tumor nutrient environment to CAF state decisions and state-related functions. It further suggests that incorporating metabolic features of the PDAC TME increases the fidelity of existing model systems, which may allow discovery of novel regulators of CAF heterogeneity.