Physciosporin suppresses mitochondrial respiration, aerobic glycolysis, and tumorigenesis in breast cancer

Background: Physciosporin (PHY) is one of the potent anticancer lichen compound. Recently, PHY was shown to suppress colorectal cancer cell proliferation, motility, and tumorigenesis through novel mechanisms of action. Purpose: We investigated the effects of PHY on energy metabolism and tumorigenicity of the human breast cancer (BC) cells MCF-7 (estrogen and progesterone positive BC) and MDA-MB-231 (triple negative BC). Methods: The anticancer effect of PHY on cell viability, motility, cancer metabolism and tumorigenicity was evaluated by MTT assay, migration assay, clonogenic assay, anchorage-independent colony formation assay, glycolytic and mitochondrial metabolism analysis, qRT-PCR, flow cytometric analysis, Western blotting, immunohistochemistry in vitro; and by tumorigenicity study with orthotopic breast cancer xenograft model in vivo. Results: PHY markedly inhibited BC cell viability. Cell-cycle profiling and Annexin V-FITC/PI double staining showed that a toxic dosage of PHY triggered apoptosis in BC cell lines by regulating the B-cell lymphoma-2 (Bcl-2) family proteins and the activity of caspase pathway. At non-toxic concentrations, PHY potently decreased migration, proliferation, and tumorigenesis of BC cells in vitro. Metabolic studies revealed that PHY treatment significantly reduced the bioenergetic profile by decreasing respiration, ATP production, and glycolysis capacity. In addition, PHY significantly altered the levels of mitochondrial (PGC-1 alpha) and glycolysis (GLUT1, HK2 and PKM2) markers, and downregulated transcriptional regulators involved in cancer cell metabolism, including beta-catenin, c-Myc, HIF-1 alpha, and NF-kappa B. An orthotopic implantation mouse model of BC confirmed that PHY treatment suppressed BC growth in vivo and target genes were consistently suppressed in tumor specimens. Conclusion: The findings from our in vitro as well as in vivo studies exhibit that PHY suppresses energy metabolism as well as tumorigenesis in BC. Especially, PHY represents a promising therapeutic effect against hormoneinsensitive BC (triple negative) by targeting energy metabolism.