Estudo da indoleamina 2,3-dioxigenase 1 no câncer de bexiga: correlação com parâmetros clinicopatológicos, relação com BCG e sua inibição química

Abstract

Bladder cancer (BC) has a high rate of recurrence and progression even after TUR associated with BCG immunotherapy. Indoleamine 2,3-dioxigenase 1 (IDO) is an immunomodulatory enzyme implied in the immune escape and progression of several types of cancer, acting through signaling pathways, such as GCN2 (general control nonderepressible 2) and AHR (aryl hydrocarbon receptor). Because it is strongly induced by interferon-gamma, a BCG-induced cytokine, IDO may be responsible for part of the progression of BC after conventional treatment. The inhibition of IDO becomes attractive, but the effect of inhibitors over its pathways in BC is not known. The objectives were: (i) to verify if the IDO is associated with the progression of the BC; (ii) verify whether BCG induces IDO in the BC; and (ii) check if two usual IDO inhibitors interfere with the GNC2 and AHR pathways in the BC. Biopsies from 155 patients with BC were selected for the study, 88 with non-muscle-invasive BC (NMI) and 67 with muscle-invasive BC (MI). Immunohistochemistry for IDO was performed to correlate its expression with clinicopathological data acquired from medical records. The effect of BCG on the expression of IDO was investigated in culture of human lines of BC and in in vivo model, evaluating it by means of immunohistochemistry and real-time PCR. Inhibitors of IDO 1-methyl-D-tryptophan (MT) and INCB024360 (INCB) were evaluated in cell culture and MT in animal model. The inhibition of IDO was measured by measuring L-quinurenine in the supernatant and the activation of the GCN2 and AHR pathways by real-time PCR for CHOP and CYP1A1, respectively. As a result, the expression of IDO correlates positively with the progression of the BC (grade and stage). The use of BCG had no effect on the expression of IDO, either in culture or in animal model. The evaluated inhibitors were effective in inhibiting IDO, but MT induced the AHR pathway triggered by IDO, as an agonist. In conclusion, (i) the IDO has the potential to assist in the prognosis of BC, as it is associated with advanced degree and stage of BC; (ii) BCG does not directly induce the expression of IDO in BC, remaining as a safe adjuvant treatment; (iii) between the two IDO inhibitors evaluated, the INCB is promising, while MT offers risk for activating the AHR pathway, a pathway recognized as a potential for tumor escape and progression.