Ophiobolin A Induces Autophagy and Activates the Mitochondrial Pathway of Apoptosis in Human Melanoma Cells

Abstract

Ophiobolin A, a fungal toxin from Bipolaris species known to affect different cellular processes in plants, has recently been shown to have anti-cancer activity in mammalian cells. In the present study, we investigated the anti-proliferative effect of Ophiobolin A on human melanoma A375 and CHL-1 cell lines. This cellular model was chosen because of the incidence of melanoma malignant tumor on human population and its resistance to chemical treatments. Ophyobolin A strongly reduced cell viability of melanoma cells by affecting mitochondrial functionality. The toxin induced depolarization of mitochondrial membrane potential, reactive oxygen species production and mitochondrial network fragmentation, leading to autophagy induction and ultimately resulting in cell death by activation of the mitochondrial pathway of apoptosis. Finally, a comparative proteomic investigation on A375 cells allowed to identify several Ophiobolin A down-regulated proteins, which are involved in fundamental processes for cell homeostasis and viability.

Proteomics Insights into Autophagy

“…Proteomics has been used successfully to screen whole cell lysates for differential protein expression and post‐translational modifications as a function of different stress stimuli including drug treatments and radiation . Cells exposed to exogenous stimuli are lysed to obtain the entire complement of proteins that may have been affected, but without regard to cellular compartment or function.…”

“…Ophiobolin A (OP‐A), a fungal toxin and potential anticancer agent, has been determined to induce autophagy . Rodolfo et al.…”

“…Rodolfo et al. investigated the anticancer activity of OP‐A using a human melanoma cell model (A375, and CHL‐1 cell lines) . A comparative proteomics experiment was used to determine differentially regulated proteins due to OP‐A treatment.…”

“…used LC‐MS/MS to identify 24 protein spots that were significantly affected by OP‐A treatment. Among the differentially regulated proteins were fructose 1,6‐bisphosphate aldolase A (ALDOA) and triose phosphate isomerase (TPI) . These enzymes, found to be associated with autophagy, have been shown to be important in glycolysis in a cell type dependent manner .…”

Epithelial-mesenchymal transition sensitizes breast cancer cells to cell death via the fungus-derived sesterterpenoid ophiobolin A

“…This sesterterpenoid (25-carbons) is a secondary metabolite that has long been studied for its phytotoxic effects in a variety of plants and has begun to be evaluated as a cytotoxic compound 38 . Recently published cell culture-based experiments describe a role for OpA in motility inhibition 39 , membrane depolarization 40-43 , roles in inflammation 44 , and reduction in stemness 45 . In vivo data demonstrate that OpA is tolerated in mice and is effective against an orthotopic model of glioblastoma 40,46,47 .…”