Influência do catabolismo do triptofano via indoleamina 2,3-dioxigenase sobre a indução da angiogênese por hipóxia no câncer de bexiga

Abstract

Two processes are crucial for the development and progression of bladder cancer (BC), angiogenesis and immune escape, which are related through key molecules specially induced in a hypoxic environment controlled by HIF-1 α. Indoleamine 2,3-dioxygenase-1 (IDO1) is an immunomodulating enzyme induced by interferon-gamma (IFN-γ ) that has been linked to angiogenesis in some neoplasms. It is possible that its activity is modulated during hypoxia, affecting local inflammation and the production of new vessels. The aim of the study was to verify whether the situation of hypoxia with alteration of HIF1α alters the expression of IFN-γ and IDO1 and whether the activity of IDO1 influences angiogenesis in BC. In an in vitro phase, T24 cells were subjected to different times of hypoxia with and without oxygen recovery. CoCl2 was also used as a stabilizer for HIF-1 α without hypoxia. HIF-1α, VEGF-A, IFN-γ and IDO1 were analyzed by ELISA or qRT-PCR, and IDO1 activity by Lkynurenine measurement (HPLC). In another phase, HUVEC cells were incubated with a high concentration of L-kynurenine and/or with a low concentration of tryptophan for analysis of vascular tubes. In the in vivo phase, CB-bearing animals were treated with 1-methyl-tryptophan (IDO1 inhibitor) to assess angiogenesis (CD31 immunohistochemistry). As a result, hypoxia increased IFN-γ, while IDO expression and activity significantly decreased. The decrease in IDO1 expression correlated negatively with VEGF-A expression. The simulation of an environment with a high concentration of L-kynurenine and a low concentration of tryptophan decreased the formation of vascular tubes. In an animal model, IDO1 inhibition increased blood vessel formation. In conclusion, in BC, during hypoxia there is an increase in IFN-γ, but there is a decrease in IDO1 expression and activity, effects possibly mediated by HIF-1α. The low activity of IDO1 during hypoxia favors angiogenesis in BC.