Avaliação da atividade de enzimas antioxidantes e da mieloperoxidase em pacientes com adenocarcinoma colorretal esporádico

Abstract

Colorectal cancer (CRC) is the second most incident cancer in women and the third most incident in men, both in Brazil and worldwide. For 2020, about 1 million deaths due to CRC are estimated, with the majority of cases of this neoplasm being sporadic, that is, they do not have a family history and the main histological subtype diagnosed is adenocarcinoma. The development of CRC is closely related to environmental factors, in addition to the involvement of oxidative stress in its pathogenesis. It is not yet well established whether oxidative stress in tumor cells results from an increase in the production of oxidants or from defects in defense mechanisms. However, since tumor cells are often in hypoxia, the regulation of their antioxidant defenses is altered. Thus, the aim of this study was to evaluate the activity of antioxidant enzymes and myeloperoxidase in patients with sporadic colorectal adenocarcinoma. For the study, 19 patients with CRC and 10 healthy subjects were selected for the control group. The activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione S-transferase (GST), as well as myeloperoxidase (MPO) were evaluated. The collection of blood from the patients was carried out in the facilities of the Hospital Regional do Oeste, located in Chapecó/SC. The project was approved by the Human Research Ethics Committee of the Federal University of Fronteira Sul (UFFS), under protocol number: 87508918.4.0000.5564. SOD and GST activities were greater in the group of patients with CRC compared to the control group. Regarding MPO, its activity was statistically lower in the group of patients with CRC compared to the control group (p<0.05). The increase in the activity of SOD and GST, in patients with CRC, considers the existence of a compensatory mechanism to the increase in the production of reactive oxygen species (ROS) in the tumor environment. Thus, the greater availability of substrate for these enzymes would be increasing its activities. In addition, the actions of the GST are also associated with the signaling pathways of tumor development and a mechanism of resistance to chemotherapy, a fact that could be favoring the development of CRC in these patients, as well as it could impair the efficiency of therapeutic protocols with antineoplastic agents. Regarding MPO, even though its activity is involved in inflammatory and carcinogenic processes, it appears to be a protective role in CRC. Its basal activity is related to immune defense against tumors and its deficiency is linked to an increase in the incidence of colon tumors and to chronic inflammation not linked to pathogens. Also, the increase in hydrogen peroxide (H 2 O 2 ), substrate of MPO, is related to the progression of the CRC. The results of this study demonstrate that a change in the activity of the studied enzymes may be associated with the progression of CRC, making them important biological markers associated with the development of tumors.