Carotenoid pigment of Halophilic archaeon Haloarcula sp. A15 induces apoptosis of breast cancer cells

Abstract The halophilic microorganisms living in extreme environments contain high concentrations of carotenoids with notable medical abilities. The purpose of this study was to evaluate the anticancer effect of carotenoids extracted from native Iranian halophilic microorganisms with the ability to inhibit breast cancer cell line. To begin the study, 40 halophilic strains were cultured, and 8 strains capable of producing pigmented colonies were chosen from those cultured strains. In the next step, from among 8 strains using MTT assay, 1 capable of reducing cell viability of the breast cancer MCF‐7 cell line was chosen as a selective strain. The principal carotenoid was characterized using UV‐visible, FT‐IR spectroscopic, and LC‐MASS analyses. Using real time PCR technique, the expression of genes specific for apoptosis, in the presence or absence of carotenoid, was examined. Among all strains, carotenoid extracted from strain A15 had the most potent cytotoxic effect on breast cancer cell line (IC 50 = 0.0645 mg/mL). 16S rRNA gene analysis showed that strain A15 had similarity with Haloarcula hispanica for about 99.5%. According to the analysis results, it could be estimated that the principal carotenoid extracted form Haloarcula sp. A15 was similar to bacterioruberin. Both early and late apoptosis were increased significantly about 10% and 39%, respectively, due to upregulation of CASP3, CASP8, BAX genes expression in MCF‐7 cell line. In contrast, the expression of genes MKI67 , SOX2 were significantly downregulated in treated MCF‐7 cell line. The results of this study showed that Halophilic archaeon strain could be a good candidate for the production of high added‐value bacterioruberin due to its possible anticancer properties.