Characterization of Cytotoxic Proteins from King Tuber Oyster Medicinal Mushroom, Pleurotus tuber-regium (Agaricomycetes), Sclerotium for Human Breast MDA-MB-231 Cancer Cells.

In targeted therapy, proteins/peptides are expected to be more effective as anticancer and/or antitumor agents. Our previous study showed that the protein fraction of Pleurotus tuber-regium (Fr.) Singer sclerotia (PS60) possesses significant cytotoxic activity against the MDA-MB-231 breast cancer cell line, with a 50% inhibitory concentration (IC50) of 0.75 ± 0.57 μg/mL. The current study aimed to further separate and characterize cytotoxic PS60 proteins from P. tuber-regium sclerotia toward MDA-MB-231. The separation of PS60 was conducted using fast protein liquid chromatography. The MTT assay was used to analyze the cytotoxic activity of the protein peaks separated from PS60. Then all of the protein peaks were characterized using liquid chromatography quadrupole time-of-flight mass spectrometry analysis. Three protein peaks (Q1, Q2, and Q3) were successfully separated from PS60. Both the PS60 and protein peaks have shown significant cytotoxic effects against MDA-MB-231 cell growth, with an IC50 < 1.00 μg/mL. Cytotoxic proteins were identified and characterized as kinesin-like protein and keratin type 1, cytoskeletal 10. Several potential cytotoxic proteins from P. tuber-regium sclerotia reactive against MDA-MB-231 breast cancer cells were identified.