Avaliação da atividade antitumoral da fração diclorometânica obtida das raízes de Arrabidaea brachypoda (DC BUREAU)

Abstract

Cancer affects millions of people, representing one of the biggest public health problems worldwide. Available treatments have several adverse effects and little specificity. Thus, the need for more effective therapeutic options, with less toxicity and greater specificity, has intensified the search for new drugs. Arrabidaea brachypoda is a native plant of the Brazilian Cerrado known as "cipó-una", "santo cipó", "cervejinha do campo", popularly used in the treatment of inflammation, kidney stones and pain. Our main aim was to evaluate the antitumor potential of the dichloromethane fraction (DCMF) obtained from A. brachypoda roots, whose components are three dimeric flavonoids of unusual structures, called brachydins. Sulforhodamine B assay results revealed DCMF cytotoxicity, and the impact of fetal bovine serum (FBS) on this activity. In silico analysis showed strong affinity between serum albumin and brachydins, confirming the impact of FBS concentration on the antitumor activity of DCMF. Based on this, cancer cells from breast (MCF7), cervix (HeLa), prostate (DU145), as well as non-tumor prostate cells (PNT2), were maintained in culture medium with 1% FBS and treated with different DCMF concentrations (1 to 8 μg/mL). Assays revealed IC50's of 2.77, 2.46, 2.51 μg/mL and 4.08 μg/mL for MCF7, Hela, DU145 and PNT2, respectively. Genotoxicity analysis by the comet assay revealed that DCMF does not cause DNA damage when both tumor and non -tumor cells are exposed to 1⁄2 IC50, IC50 and double IC50 for 3 and 24 hours. In addition, DCMF inhibited colony formation (by clonogenic assay) of tumor cells in a concentration-dependent manner (r = -0.944, p <0.05), with almost total inhibition in HeLa and MCF7 cells exposed to their respective IC50. Additionally, treatments with 2.5 μg/mL and 1.25 μg/mL significantly inhibited DU145 colony formation by 87.3 and 39.2%, respectively. Cell migration was evaluated by the wound healing assay, which revealed reduced mobility of DU145 cells (r = -0.751, p < 0.05), whereas there was no effect on the PNT2 cell line. Atomic Force Microscopy (AFM) analysis revealed ultrastructural changes (holes) on the nuclear membrane surfaces of DCMF-treated DU145 cells. Additionally, there was a positive correlation between cell membrane roughness and fraction concentration (r= 0.857, p < 0.05), with 7.9 ± 0.43 nm for untreated cells, and 11.6 ± 1.42 nm and 15.37 ± 3.9 for tumor cells exposed to 2.5 μg/mL and 1.25 μg/mL, respectively. All these findings support the antitumor activity of DCMF and suggest that the induction of ultrastructural changes in the cell membrane may be one of the mechanisms of action of brachydins.