EFFECTS OF THE STEROID OUABAIN ON THE LYMPHOCYTE POPULATION IN A SUBCUTANEOUS MODEL OF MURINE MELANOMA (B16F10)

INTRODUCTION AND OBJECTIVES: Ouabain (OUA) is a steroid initially used to treat heart failure and such effects are due to its potential as a specific inhibitor of Na+/K+-ATPase. OUA has been described as an endogenous substance, therefore, it has a role in the modulation of the immune system and acts as a modulator of inflammatory responses. Melanoma is a tumor derived from epidermal melanocytes, considered the most lethal skin cancer, with high mortality rates. The aim of, this study was investigate the in vivo effects of OUA on the immune response of C57BL/6 mice with subcutaneous melanoma. MATERIAL AND METHODS: C57BL/6 mice were injected intraperitoneally for three consecutive days with 200 ul of DMEM medium in the control (CTR) and melanoma (MEL) groups or with 0.56mg/Kg of OUA in the Ouabain (OUA) and melanoma plus. Ouabain groups (MEL+OUA). On the 4th day, half of the animals from the CTR and OUA groups were euthanized for internal control of the experiment and the MEL and MEL+OUA groups were inoculated subcutaneously on the flank with melanoma (B16F10). On the 21st day, all other animals were euthanized to remove the spleen, mesenteric and inguinal lymph nodes. The cells were stained with different antibodies and flow cytometry analysis was performed. RESULTS AND CONCLUSION: Our preliminar results show that, on the 4th day, the treatment with OUA decreases the percentage and absolut number of B cells in the spleen, confirming the previous results of our group. In inguinal lymph node, ouabain decreases the number absolut number of B lymphocytes besides CD4+ and CD8+ T lymphocytes. On the 21st day there was a decrease in percentage of CD4+ T cells in the MEL+OUA group when compared to the control group in inguinal lymph node. On the other hand, there was an increase in the absolut number of B cells in the MEL+OUA group when compared to the other groups. These results point to a possible effect of ouabain on the recruitment of B lymphocytes to the tumor draining lymph node.