Unusual dimeric flavonoids (brachydins) induce ultrastructural membrane alterations associated with antitumor activity in cancer cell lines

Abstract

Notwithstanding the advances in molecular target-based drugs, chemotherapy remains the most common cancer treatment, despite its high toxicity. Consequently, effective anticancer therapies with fewer adverse effects are needed. Therefore, this study aimed to determine the anticancer activity of the dichloromethane fraction (DCMF) isolated from Arrabidae brachypoda roots, whose components are three unusual dimeric flavonoids. The toxicity of DCMF was investigated in breast (MCF-7), prostate (DU145), and cervical (HeLa) tumor cells, as well as non-tumor cells (PNT2), using sulforhodamine B (cell viability), Comet (genotoxicity), clonogenicity (reproductive capacity) and wound healing (cell migration) assays, and atomic force microscopy (AFM) for ultrastructural cell membrane alterations. Molecular docking revealed affinity between albumin and each rare flavonoid, supporting the impact of fetal bovine serum in DCMF antitumor activity. The IC₅₀ values for MCF7, HeLa, and DU145 were 2.77, 2.46, and 2.51 µg/mL, respectively, and 4.08 µg/mL for PNT2. DCFM was not genotoxic to tumor or normal cells when exposed to twice the IC₅₀ for up to 24 h, but it inhibited tumor cell migration and reproduction compared to normal cells. Additionally, AFM revealed alterations in the ultrastructure of tumor nuclear membrane surfaces, with a positive correlation between DCMF concentration and tumor cell roughness. Finally, we found a negative correlation between roughness and the ability of DCMF-treated tumor cells to migrate and form colonies with more than 50 cells. These findings suggest that DCFM acts by causing ultrastructural changes in tumor cell membranes while having fewer toxicological effects on normal cells.

Keywords:

• Arrabidaea brachypoda
• atomic force microscope
• cell membrane
• chemotherapy
• natural products

Acknowledgement

The authors wish to express their gratitude to the Nanobiotechnology Laboratory at the Federal University of Uberlandia in Minas Gerais, Brazil (particularly to Professor Luiz Ricardo Goulart Filho, in memoriam) and the Mutagenesis Laboratory at the University of Franca in São Paulo, Brazil (particularly, Professor Denise Crispim Tavares Barbosa) for donating the cell lines used in this study.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES - Finance Code 001; grant number 88887.472618/2019–00-PROCAD-AM). This research was also supported by Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA), grant number 00838/17-Universal.