Pancreatic Ductal Adenocarcinoma (PDAC) is one of the cancers with the worst 5- year survival rates due - among others - to late detection and lack of an effective therapy. A dense desmoplastic reaction is one of the main characteristics of PDAC microenvironment, mainly due to an increase of number/activity of pancreatic stellate cells (PSCs), which are the main contributors in the production of extracellular matrix proteins, such as collagens. In this complex microenvironment, consisting of both cellular and noncellular components, metabolically active cells and dying cells can release high concentrations of ATP in the extracellular compartment. Among all the purinergic receptors, P2X7 receptor (P2X7R), with its peculiar double-faced role in both cell death and cell proliferation, has been shown to be involved in the progression of some types of cancer. Thus, the aim of our study was to investigate the possible role of P2X7R in PDAC behaviour in vitro and in vivo.
We detected a higher P2X7R protein level in several human PDAC cells compared to a “normal” human pancreatic duct epithelial cell line, which localized mostly on the plasma membrane. From the functional point of view, we observed that a sustained activation of the P2X7 receptor using ATP and BzATP (a more potent agonist) resulted in a cytotoxic effect, mainly ascribed to necrosis. The allosteric inhibition of the receptor led to a drastic reduction in cell proliferation in all PDAC cell lines. Moreover, P2X7R showed a crucial role in PDAC cell migration and invasion. Stimulation of the receptor with BzATP or ATP markedly increased migration and invasion compared to the control cells. The allosteric inhibition of P2X7R reduced cancer cell migration and invasion significantly.
We detected P2X7R expression in tissues deriving from an orthotopic xenograft PDAC mouse model. Furthermore, we transplanted cells that were stably transfected with luciferase (PancTu-1 Luc), to monitor tumor growth through bioluminescence detection and confirmed in vivo the anti-proliferative effect of the allosteric inhibitor AZ10606120. In addition, staining of the primary tumor revealed a significant reduction in the number/activity of murine PSCs in mice treated with the inhibitor compared to the control, which correlated with a substantial reduction in collagen deposition.
In conclusion, we showed that the P2X7 receptor plays multiple crucial roles in in vitro and in vivo PDAC progression, opening a new possibility of PDAC treatment.