Avaliação do efeito da istradefilina no melanoma metastático: a importância da via adenosinergica no microambiente tumoral

Abstract

Metastatic melanoma is a very aggressive skin cancer characterized by the development of strong immunosuppression in the tumor microenvironment (TME). Adenosine (ADO) is the main actor in the process of escaping from immune surveillance and maintaining the immunosuppressive state, which leads to rapid tumor progression. ADO is produced from the hydrolysis of ATP, ADP and AMP which are released in the TME. CD39, CD73 and E-ADA are cell surface enzymes responsible for controlling the concentrations of these signals, thus limiting their action. ADO acts primarily on the A2A receptor, which has been shown to be a positive regulator in the protection and promotion of tumors. ATP, on the other hand, acts as a proinflammatory molecule by activating P2 receptors, or being degraded by the enzymes of the CD39/CD73 axis to ADO. The use of A2A antagonists has been explored as a potential therapeutic target in cancer, however there is a shortage of safe and pharmacologically functional molecules available. The drug Istradefylline (IST) is a selective A2A antagonist (used in Parkinson disease) of recognized safety and bioavailability. Thus, the aim of the present work was to evaluate and compare the effect of A2A antagonism (with IST and caffeine) in a TME recreated in vitro; and to evaluate the effect of IST on tumor mass and immune organs (spleen and thymus) in a murine melanoma model. In the first experiment, we found that ADO increased the viability and proliferation of melanoma cells in a concentration-dependent manner. ATP increases viability only as a substrate for CD39 to produce ADO. IST was toxic to melanoma cells, and IST potentiated the paclitaxel-induced cytotoxic effects, reducing IC50. IST increases expression of CD39 and CD73. CD39 activity was increased and E-ADA was reduced, indicating that B16F10 (melanoma) cells promoted compensatory feedback in the production and maintenance of ADO levels. IST reduced factors associated with malignancy such as migration, adhesion, colony formation and melanin production capacity. IST significantly increases nitric oxide production, which correlates with a decline in melanoma cell viability by apoptotic events. This study supports the hypothesis that IST may be a promising cancer therapy. In the in vivo experiment. IST as a treatment for murine melanoma reduced tumor growth. IST resulted in modulation in the expression and activities of CD39, CD73, E-ADA present in the tumor, spleen and thymus, indicating an increase in the extracellular concentration of ATP and a reduction in ADO and thus a pro-inflammatory profile. IST treatment resulted in increased A2A expression in the tumor, in an attempt to restore this receptor signaling. But it also elevated the P2X7 receptor, which culminated in the release of IL-1β, IFN-γ and TNF-α. Furthermore, IST inhibited the AKT/mTOR pathway, involved in tumor growth without altering the resistance pathway to MAPK/ERK treatment. Considering the present results, we can say that IST is a promising drug for off-label use in melanoma cancer.