Proceedings of Oncobiology Symposiums
Proceedings of XIV Oncobiology Symposium

INTRODUCTION AND OBJECTIVES: Ouabain is a steroid produced by mammals in stressful situations. Recent studies have shown its role in the modulation of B and regulatory T cells, which negatively regulate antitumor responses. Therefore, our main objective was to study if ouabain, by the modulation of lymphocytes in vivo, improves the response to murine melanoma. MATERIAL AND METHODS: The C57Bl/6 mice were divided into 4 groups: a control group (injected with DMEM medium), a ouabain group (injected intraperitoneally with 0.56mg/Kg of ouabain for three consecutive days), a melanoma group (injected with 106 melanoma cells) and a melanoma plus ouabain group. Two experimental protocols were performed: in one, the melanoma cells were injected intraperitoneally and in the other, the cells were subcutaneously injected. In addition, the time of the ouabain injection also underwent variations with animals being injected before (pre-treatment) or after the tumor (post-treatment) in order to approach the clinical reality. On the 21st day after injections, euthanasia was performed to remove the organs, followed by flow cytometry cell analysis. RESULTS AND CONCLUSION: Regulatory T lymphocytes were reduced in the spleen after in vivo pre-treatment with ouabain in the intraperitoneal tumor protocol. Moreover, in the intraperitoneal pre-treatment, it was observed that ouabain maintains the number of B lymphocytes in the spleen and improves animal survival. In the same tumor protocol, but post-treated with ouabain, the reduction of TCD4+, TCD8+, and B lymphocytes was observed regardless of the treatment with ouabain. In the subcutaneous tumor model post-treated with ouabain there was the tendency, although not statistically significant, of total B and T lymphocytes reduction in the spleen and no alterations in the lymph nodes. The ouabain did not interfere directly in the in vitro viability of melanoma cells. In conclusion, ouabain acts as an immunomodulator, improving the survival of animals with melanoma only in previous treatment in the intraperitoneal tumor protocol.