Abstract Colon cancer is the fifth most common malignancy among Iranian men and third among Iranian women, respectively. Although various chemotherapeutic regimens are available for colon cancer patients, unfavorable side effects and acquired resistance limit their application. To investigate new approaches for colon cancer treatment, we evaluated anticancer potential of Streptomyces extracted from Persian Gulf in vitro. After isolation and antibacterial screening of Streptomyces extracts, two strains were selected (AC7 and AC24). For in vitro toxicity assay, HT-29 cells, as well as normal fibroblasts, were treated with 60, 120 and 240 µg/ml AC7 and AC24 extracts for 24 h. Then, viability was evaluated by alamarBlue assay and morphological alterations were recorded. Results revealed that viability of HT-29 cells and fibroblasts dramatically decreased upon treatment with both extracts, while toxicity of AC7 extract was more than AC24 extract. Based on obtained findings, AC7 and AC24 extracts induced their effects in a cell type- and dose-dependent manner. In conclusion, our findings indicated cytotoxicity of AC7 and AC24 strains from Persian Gulf for the first time, although more research is required to determine their mechanism of action.

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