Apoptosis-inducing Metabolite from Marine Mangrove Actinobacteria VITGAP173.

Abstract

Marine actinobacteria have proven to be a remarkable source of bioactive metabolites. The present study focused on the isolation of anticancer metabolites from marine actinobacteria. Streptomyces sp. VITGAP173 was found to have promising anticancer activity against breast cancer cell lines (MCF-7). Bioassay-guided fractionation was followed to identify the bioactive metabolites from crude ethyl acetate extract of VITGAP173, which yielded four fractions. Fraction B exhibited the highest cytotoxic activity against MCF-7 cell lines among the four fractions. Further structural characterization of the fraction was done by FTIR and NMR spectroscopy. The fraction-2 induced cytotoxicity against MCF-7 cell lines and the half maximal inhibition (IC50) value was calculated as 4.7 μg/ml. To elucidate the possible mechanism of cell death, MCF-7 cells were treated with fraction-2 for 24 hours and the morphological changes were examined using acridine orange - ethidium bromide (AO/EB) staining. The fraction also increased the reactive oxygen species (ROS) generation (Flow cytometry, DCFHDA). The molecular mechanism of fraction-induced cell death was analysed by real-time PCR, which revealed that the fraction promotes apoptosis through the CHOP-ATF-4 pathway involved in ER stress signalling. The present findings suggested the apoptosis-inducing potential of fraction-2 in breast cancer therapy.