Piericidina A1 de Streptomyces SP. recuperada de sedimento do arquipélago Fernando de Noronha altera fenótipo de células tumorais

Abstract

Cancer is a major health problem and presents great biological complexity, making it extremely difficult to develop effective therapeutic strategies to treatment of the disease, especially in advanced stages. Natural products play an important role in pharmacology because of the notorious contribution to the development of drugs as pharmacological tools. The marine sediment is a profitable source of microorganisms that produce secondary metabolites with biomedical properties, and the actinomycetes, Gram-positive bacteria, are excellent producers of compounds with diverse biological activities. In this work, the pharmacological potential of the microbiota recovered from the marine sediment collected in Fernando de Noronha Archipelago was investigated in tumor cells in culture. Sixteen actinomycete lineages were isolated, 7 of which yielded cytotoxic crude extracts (inhibition of growth > 75%) in human colorectal cancer cells HCT-116. The mean inhibitory concentration (IC50) values of the crude extracts varied from 0.06 to 10g/mL. The BRA-399 strain, identified as Streptomyces sp., presented the highest potency (IC50 = 0.06g/mL) and was selected to proceed with the purification of the active principle and characterization of the biological effect in tumor cells. Through a bioguided chemical fractionation, Piericidin A1 (PA1) was isolated, and other molecules of the same class were identified. The cytotoxicity of PA1 was then investigated in 2 tumoral lineages, HCT-116 and in murine metastatic melanoma (B16-F10). The MTT, SRB, cell count and membrane integrity by cytometry assays were performed with both cell lines to obtain a cell proliferation inhibition profile caused by PA1 at 24, 48 and 72h. The results showed cell proliferation inhibition in both lineages at the highest tested concentrations (between 3.8nM and 12M). Lower concentrations (0.1 to 24pM) inhibited proliferation in HCT-116 cells, but not in B16-F10 cells. Despite the unique potency, cells had the membrane integrity preserved at almost all concentrations, except the greater, 12M. PA1 blocks the complex I of the electron transport chain, and the change in the energy metabolism is a hallmark of tumor cells involved in tumor agressiveness. From these observations, some experiments were carried out to evaluate the influence of PA1 on the agressiveness of tumor cells (HCT-116 and B16-F10) in the concentration of 500fM. Cells pretreated with PA1 showed an increase in IC50 compared to treatment with the chemotherapeutic doxorubicin. Treatment with PA1 also increased the cell migration rate in B16-F10, as well as induced morphological alterations compatible with greater migratory activity cells, reinforcing the hypothesis that the alteration caused by PA1 in the tumor cell metabolism may induce alteration in their phenotype.