Streptomycetes are gram-positive prokaryotic organisms that are known for production of many bioactive secondary metabolites like antibiotics and anticancer agents. Colon cancer is among the top 5 most common cancers worldwide, with high mortality rate. Hypoxia is a common phenomenon in most solid tumors that negatively affect clinical outcomes during the treatment of cancer. In the current study, we compared cytotoxicity of Streptomyces extracts on the viability of human colon cancer cells in normoxic and hypoxic conditions. To do so, Streptomyces were isolated from water samples and based on the production of secondary metabolites and antibacterial activities, two strains (AC7 and AC24) were selected. Then, sub-merged fermentation was applied to produce cytotoxic agents by AC7 and AC24. Afterwards, LoVo cells were treated with 60, 120 and 240 µg/ml AC7 and AC24 extracts in normoxic and hypoxic conditions and their viability was evaluated by resazurin assay after 24 h. Results indicated that both extracts reduced cell viability in normoxic condition in a dose-dependent manner. Treatment of cells with AC7 and AC24 extracts in hypoxic condition also decreased viability, and worth to note, toxicity of AC7 extract was more than AC24 extract. To sum up, current findings revealed cytotoxicity of AC7 and AC24 extracts on colon cancer cells, and future research on other cell lines would expand our knowledge regarding toxicity potential of Streptomyces extracts.

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