Bioactive Compounds from Sponge Associated Bacteria: Anticancer Activity and NRPS-PKS Gene Expression in Different Carbon Sources

Abstract

Sponge associated bacteria with diverse NRPS-PKS genes could be the alternative source of bioactive compounds. This study aimed to analyze the activity as well as the regulatory mechanism regarding the anticancer properties derived from these bacteria against cancer cell lines. Extraction of bacterial metabolites using ethyl acetate solvent resulted yield ranging from 0.003 to 0.016% (w/v). Six extracts of bacterial metabolites showed markedly cytotoxic activity against 8 human hematopoietic cancer cell lines, with IC₅₀ value 27.24 to 533.73 μg mL^-1 in a dose dependent response, as assessed by MTT test. Supporting those results, reduction of cell density, morphological changes including cell shrinkage and formation of the apoptotic body of cancer cells lines, were found. As it might be due to the inhibitory effect of bacterial extract treatment. Apoptosis assay determined by annexin V-FITC apoptosis analysis showed that apoptotic cells were induced by bacterial extract after 6 h of treatment. Thus suggesting that the extract could be one of the external signals that activate the signal transduction pathway of apoptosis, especially in MOLT4 cells, acute lymphoblastic leukemic cell lines. Cell cycle analysis using propidium iodide revealed that the extract HAA 01 caused cell cycle arrest, since most of the MOLT4 cells were accumulated in Sub-G1 phase after 24 h of extract treatment. Interestingly, glycerol, lactose and amylum were the more preferable carbon source to produce anticancer compounds, than glucose. Our study indicates that anticancer activity of HAA 01 (identified as Bacillus subtilis based on API identification) extract is highly correlated with NRPS-PKS gene expression which is likely regulated by the type of carbon source.