Potencial antitumoral das proteínas TRAIL e IL-2 expressas e veiculadas por Salmonella Typhimurium atenuada em modelo de câncer colorretal

Abstract

Colorectal cancer is the third most diagnosed malignant disease and the fourth leading cause of cancer-related deaths in the world. Cancer treatments are not fully effective and low selectivity to tumor tissue has marked side effects, so there is a high importance of studies that seek new alternatives for the treatment of this disease. In this work we use an attenuated strain of Salmonella as a live bacterial vector, which prefers to invade the tumor microenvironment and can produce heterologous proteins with immunotherapeutic potential. The objectives were to develop plasmids and insert them into the attenuated Salmonella SL3261, containing the genes that encode tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and Interleukin 2 (IL-2); and evaluate, in vitro and in vivo, the antitumor potential of these strains in colorectal tumor (HCT-8 strain). Confirmation of protein construction and expression was done by electrophoresis, Western Blot and ELISA, with anti-TRAIL and anti-IL-2 monoclonal antibodies. The effect on HCT-8 was determined by the cytotoxicity test (MTT), Griess reaction and apoptosis assay (Annexin V). To analyze tumor progression in vivo, mice received tumor cells and, after tumor implantation, were treated with the constructed strains. Tumor size was calculated every three days and tumor weight was determined after euthanasia. The results demonstrated that the expression vector construction was effective and the proteins were expressed by SL3261. In vitro tests showed decreased viability and increased cell death in groups treated with SL3261_TRAIL and SL3261_IL-2 when compared to control groups, and nitric oxide production. Regarding the in vivo tests, the SL3261, SL3261_TRAIL and SL3261_MIX (TRAIL + IL-2) treatments showed antitumor effect in this model, since they presented decreased tumors compared to the untreated control 14 days after treatment. Thus, it is suggested that TRAIL and IL-2, expressed by SL3261, have antitumor effect in the colorectal cancer model, proposing a possible immunotherapy against this type of tumor.