Induction of G2/M cell cycle arrest and phosphorylated-extracellular signal-regulated protein kinase 1 and 2-induced caspase 3/7-independent apoptosis in HT-29 cells by the combination of fraction S1 and citrinin from Penicillium strain H9318

Abstract

OBJECTIVES: To determine the effect of potential anticancer property of secondary metabolites of Penicillium strain H9318. MATERIALS AND METHODS: Cytotoxicity of HT-29 cells was accessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide viability assay to give a preliminary comparison of the efficacy of fraction S1 and citrinin H9318. Mode of action of the combination treatment of fraction S1 and citrinin H9318 was determined by the cell cycle assay using propidium iodide-staining method performed with a flow cytometer. Further clarification of the anticancer mechanism of the combination treatment was carried out by the assays of pan-caspase, caspase-3/7, and western blot to examine the apoptosis of HT-29 cells. RESULTS: HT-29 cells show dose-dependent manner in cytotoxicity. HT-29 cells were arrested at G2/M phase with decrease in phosphorylated-retinoblastoma protein. Citrinin H9318, citrinin H9318 and fraction S1 combination-treated HT-29 cells show induction of pan-caspase. Caspase-3/7 was found decrease in the combination of citrinin H9318 and fraction S1 through up-regulation of phosphorylated-extracellular signal-regulated protein kinase 1 and 2 (p-ERK1/2). CONCLUSION: Citrinin H9318 alone did not reduce activity of caspase-3/7 significantly in the apoptosis of HT-29 cells. The combination treatment of fraction S1 and citrinin H9318 contributed to apoptosis via up-regulation of p-ERK1/2 with reduced activity of caspase-3/7.