Schwann cells support oncogenic potential of pancreatic cancer cells through TGFβ signaling

Pancreatic ductal adenocarcinoma (PDAC) is one of the solid tumors with the poorest prognosis. The stroma of this tumor is abundant and composed of extracellular matrix and stromal cells (including cancer-associated fibroblasts and immune cells). Nerve fibers invading this stroma represent a hallmark of PDAC, involved in neural remodeling, which participates in neuropathic pain, cancer cell dissemination and tumor relapse after surgery. Pancreatic cancer-associated neural remodeling is regulated through functional interplays mediated by physical and molecular interactions between cancer cells, nerve cells and surrounding Schwann cells, and other stromal cells. In the present study, we show that Schwann cells (glial cells supporting peripheral neurons) can enhance aggressiveness (migration, invasion, tumorigenicity) of pancreatic cancer cells in a transforming growth factor beta (TGF beta)-dependent manner. Indeed, we reveal that conditioned medium from Schwann cells contains high amounts of TGF beta able to activate the TGF beta-SMAD signaling pathway in cancer cells. We also observed in human PDAC samples that high levels of TGF beta signaling activation were positively correlated with perineural invasion. Secretome analyses by mass spectrometry of Schwann cells and pancreatic cancer cells cultured alone or in combination highlighted the central role of TGF beta in neuro-epithelial interactions, as illustrated by proteomic signatures related to cell adhesion and motility. Altogether, these results demonstrate that Schwann cells are a meaningful source of TGF beta in PDAC, which plays a crucial role in the acquisition of aggressive properties by pancreatic cancer cells.