NetrinG1+ Cancer-Associated Fibroblasts Generate Unique Extracellular Vesicles that Support the Survival of Pancreatic Cancer Cells Under Nutritional Stress

Abstract

It is projected that in 5 years, pancreatic cancer will become the second deadliest cancer in the United States. A unique aspect of pancreatic ductal adenocarcinoma (PDAC) is its stroma; rich in cancer-associated fibroblasts (CAFs) and a dense CAF-generated extracellular matrix (ECM). These pathogenic stroma CAF/ECM units cause the collapse of local blood vessels rendering the tumor microenvironment nutrient-poor. PDAC cells are able to survive this state of nutrient stress via support from CAF-secreted material, which includes small extracellular vesicles (sEVs). The tumor-supportive CAFs possess a distinct phenotypic profile, compared to normal-like fibroblasts, expressing NetrinG1 (NetG1) at the plasma membrane, and active Integrin α5β1 localized to the multivesicular bodies; traits indicative of poor patient survival. We herein report that NetG1+ CAFs secrete sEVs that stimulate Akt-mediated survival in nutrient-deprived PDAC cells, protecting them from undergoing apoptosis. Further, we show that NetG1 expression in CAFs is required for the pro-survival properties of sEVs. Additionally, we report that the above-mentioned CAF markers are secreted in distinct subpopulations of EVs; with NetG1 being enriched in exomeres, and Integrin α5β1 being enriched in exosomes. Finally, we found that NetG1 and Integrin α5β1 were detected in sEVs collected from plasma of PDAC patients, while their levels were significantly lower in plasma-derived sEVs of sex/age-matched healthy donors. The discovery of these tumor-supporting CAF-EVs elucidates novel avenues in tumor-stroma interactions and pathogenic stroma detection.

Assessment of technical and clinical utility of a bead-based flow cytometry platform for multiparametric phenotyping of CNS-derived extracellular vesicles

“…Although these markers seem to be related to the biological background of the disease, the limited sample size does not allow to draw definite conclusions but might provide some guidance for follow-up analysis. Notably, the EV-Neuro assay can be used as a technology to identify disease-associated EV subtypes of functional or pathological relevance that could (i) serve as source of biomarkers [ 46 ], (ii) provide potential targets for therapeutic intervention [ 45 , 47 ], or (iii) provide a route for targeted drug delivery [ 4 , 48 ].…”

Paracrine enhancement of tumor cell proliferation provides indirect stroma-mediated chemoresistance via acceleration of tumor recovery between chemotherapy cycles

“…Multiple cytokines and ECM components, produced by CAFs (e.g., HGF, FGFs, fibronectin, etc.) have been shown to strongly reduce the sensitivity of cancer cells to therapeutic agents in multiple contexts of targeted and cytotoxic therapies (6,(13)(14)(15)(16). Therefore, we asked whether the known correlation between poor prognosis and high stromal gene signature can be reduced to a correlation with CAFs.…”

Rethinking the Roles of Cancer-Associated Fibroblasts in Pancreatic Cancer

“…Thus, we consider CAF together with its native ECM (CAF + ECM) as a functional unit, 23 a concept coined by Dr. Edna Cukierman, will not only improve how we study CAF biology, but is mandatory to better understand the PDAC microenvironment as a whole. It is well known that the CAF + ECM unit imposes a physical barrier for treatment and penetration in PDAC 32 ; but more than physical, CAF + ECM is an entity that harbors reservoirs of secreted factors 33 , 34 in the tumor microenvironment (TME), including immunomodulatory factors, 35 , 36 metabolites, 37 , 38 and prosurvival factors, 34 making this unit a potential master controller of cancer progression. Additionally, the underlying fibrillar structure of collagens can also dictate disease progression 2 , 39 and cellular functions.…”

“…In addition to overcoming the nutrient-poor TME that challenges their own survival, they also provide metabolic support to other cells in their TME, including cancer cells, by providing lipids, amino acids, exosomal content, nucleosides, carbohydrates, and by recycling metabolic waste products. 26 , 37 , 38 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 Not surprisingly, there are many studies focusing on targeting different metabolic programs in CAFs, with successful functional outcomes initially, such as with glutaminase inhibitors. 74 , 75 Nevertheless, there are many redundant metabolic circuits that allow cells to rewire these circuits, 76 overcoming nutrient deficiencies induced by metabolic enzyme blockade.…”