Cytotoxicity effect of secondary metabolites of Streptomyces koyangensis and Streptomyces tunisiensis isolated from saline soils of Garmsar City on human breast cancer cell line (MCF-7, IBRC C10082)

Background: Streptomyces is one of the most important prokaryotic microorganisms, and their secondary metabolites have high antimicrobial and cytotoxic properties. Three-quarters of the antibiotics known to be produced by these bacteria. As a result, finding new effective compounds from these microorganisms can be a way to treat cancer. The aim of this study was to isolate and screen halophilic or halotolent Streptomycetes from Garmsar salt cave soil that have the ability to produce metabolites with cytotoxic properties against human breast cancer cell line (MCF-7, IBRC C10082). Materials and methods: Isolation of Streptomyces from soil sample was done by serial dilution method and cultured on casein agar with 15% Nacl. The isolates were identified by microscopic and macroscopic examinations and the presence of diaminopalimic acid (DAP) in their cell wall. The cytotoxic effect was evaluated using MTT assay and 16SrRNA sequencing was performed to select selected streptomycetes. Results: Secondary metabolites of 2 Streptomyces showed a 50% reduction in the concentration of human breast cancer cells. Streptomyces sp.2 was 100% similar to Streptomyces koyangensis and Streptomyces sp.25 was 95.4% similar to Streptomyces tunisiensis. Conclusion: The results of this study showed that Streptomyces sp.2 and Streptomyces sp.25 secondary metabolites had cytotoxic effect against MCF-7 human breast cancer cell line. The metabolite produced by them can be an option for further studies and provide more effective treatment with fewer side effects in the treatment of this disease.