Atuação de STAT3 diante do perfil de estresse oxidativo em linhagem de mama

Abstract

The STAT3 pathway is constitutively activated in different kinds of tumor, and it is associated with progression and metastasis, due to the function that plays in the proliferation, angiogenesis, migration, invasion, and resistance to apoptosis. Besides the traditional mechanisms of activation of STAT3 pathway as cytokines and growth factors, the oxidative stress in the tumor cells is able to maintain activated. Further the activation by ROS, some research shows a possible regulation by STAT3 from base excision (BER) repair pathway genes, the main responsible for restoring the damage caused by oxidation. Although there is a relation between ROS and STAT3 pathway, but there s no comprehension about the reverse way, how could the STAT3 modulate the oxidative stress. On this, the present work aimed to investigate the relation between the STAT3 pathway and the oxidative stress profile. The assay WST-1 was made to measure the viability after the STAT3 inhibition (Stattic), the BER pathway inhibition (CRT0044786), the doxorubicin treatment and the inhibition of BER pathway in cell line MDA-MB-231. The flow cytometry assay was realized to evaluate the ROS totals levels after inhibition the STAT3 and BER pathways. Then was investigate some reactive species of oxygen, hydroperoxide, NO, and GSH antioxidant, after inhibition of STAT3 pathway. Was performed an assay immunocytochemistry to evaluate a the STAT3 relation with the proteins NRF2, NFκ-B, and 3-NT, responsible for cells detoxification. The assay RT-qPCR was proposed to evaluate the levels of mRNA of APEX1 after inhibition BER pathway. The obtain results show the line cell MDA-MB-231 is dependent on the STAT3 pathway for survival, there was a reduction of 40% on the 10µM concentration in 24 hours of treatment. After inhibition of BER was a reduction of 50 % on the 1 mM of CRT after 6 hours of treatment. The ROS total levels showed a reduction after the STAT3 inhibition, approximately 20 %, 30 % and 90 % on the 5 µM, 10 µM and 20 µM concentration, respectively. The levels of hydroperoxide did not change after inhibition of STAT3, the NO levels rose 25 µM, and the levels of GSH rose 2, approximately. Later the inhibition of STAT3, the NRF2 levels decrease 0,6, the NFκ-B levels reduced 0,6 and the 3-NT levels increased 3, approximately. The mRNA of APEX1 increased 250 times after inhibition of BER pathway. Therefore, the present work indicates that the STAT3 and BER are important for the cell survival, and there is a possible influence of STAT3 for the regulation of ROS levels on the breast cancer cells line.