Abram Handly-Santana

Pancreatic stellate cells (PSCs) differentiate into cancer-associated fibroblasts (CAFs) that produce desmoplastic stroma, thereby modulating disease progression and therapeutic response in pancreatic ductal adenocarcinoma (PDA). However, it is unknown whether CAFs uniformly carry out these tasks or if subtypes of CAFs with distinct phenotypes in PDA exist. We identified a CAF subpopulation with elevated expression of α-smooth muscle actin (αSMA) located immediately adjacent to neoplastic cells in mouse and human PDA tissue. We recapitulated this finding in co-cultures of murine PSCs and PDA organoids, and demonstrated that organoid-activated CAFs produced desmoplastic stroma. The co-cultures showed cooperative interactions and revealed another distinct subpopulation of CAFs, located more distantly from neoplastic cells, which lacked elevated αSMA expression and instead secreted IL6 and additional inflammatory mediators. These findings were corroborated in mouse and human PDA tissue, providing direct evidence for CAF heterogeneity in PDA tumor biology with implications for disease etiology and therapeutic development.

Pancreatic ductal adenocarcinoma (PDA) is a lethal malignancy with limited treatment options. Although metabolic reprogramming is a hallmark of many cancers, including PDA, previous attempts to target metabolic changes therapeutically have been stymied by drug toxicity and tumour cell plasticity. Here, we show that PDA cells engage an eIF4F-dependent translation program that supports redox and central carbon metabolism. Inhibition of the eIF4F subunit, eIF4A, using the synthetic rocaglate CR-1-31-B (CR-31) reduced the viability of PDA organoids relative to their normal counterparts. In vivo, CR-31 suppresses tumour growth and extends survival of genetically-engineered murine models of PDA. Surprisingly, inhibition of eIF4A also induces glutamine reductive carboxylation. As a consequence, combined targeting of eIF4A and glutaminase activity more effectively inhibits PDA cell growth both in vitro and in vivo. Overall, our work demonstrates the importance of eIF4A in translational control of pancreatic tumour metabolism and as a therapeutic target against PDA.

Abstract Paracrine interactions between pancreatic stellate cells (PSCs) and tumor cells play key roles in pancreatic cancer tumorigenesis. However, attempts to therapeutically target the PSCs have implied that PSCs may also restrain tumor growth, raising the possibility of diverse and dynamic pathophysiological roles of these cells in cancer. In order to gain a deeper understanding of the functional heterogeneity found among PSCs, we have developed an organotypic co-culture system that allows the study of functional interactions between pancreatic tumor-derived organoids and PSCs in a three-dimensional basement membrane matrix (Matrigel). PSCs embedded in Matrigel acquire a quiescent phenotype and restore their vitamin A droplets similar to PSCs found in healthy pancreata in vivo. In co-culture the PSCs proliferate, form lattices around the organoids, and secrete extracellular matrix proteins and inflammatory cytokines. In turn, the organoids proliferate more rapidly in co-culture with PSCs compared to their mono-cultured counterparts, as well as survive passaging in reduced media conditions. Furthermore, we show that PSCs can differentiate into two distinct subtypes with different phenotypic features depending on the spatial proximity to the co-cultured organoids. PSCs found in direct contact with tumor cells express higher levels of smooth muscle actin (SMA), while PSCs that are more distant from the tumor cells show low SMA expression and gain a secretory phenotype. The secreted factors from this subtype of PSCs activate signaling pathways important for survival and proliferation in tumor organoids. We demonstrate that these two subtypes are mutually exclusive, and can both be found in vivo with similar spatial distribution as seen in the co-culture system. Taken together, we have identified two subtypes of PSCs present in pancreatic cancer with potentially different pathophysiological functions. Preferentially targeting one of these subtypes in future clinical trials may positively affect patient outcomes. Citation Format: Daniel Öhlund, Abram Handly-Santana, Ela Elyada, Giulia Biffi, David A. Tuveson.{Authors}. Pancreatic stellate cell heterogeneity in cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B73.