Antiproliferative and Apoptotic Activities of the Medicinal Mushroom Phellinus rimosus (Agaricomycetes) on HCT116 Human Colorectal Carcinoma Cells.

Abstract

Phellinus rimosus is a host-specific wood-rotting polypore that has been reported to be used by some tribes in Kerala, India, for curing mumps. We isolated a novel polysaccharide-protein complex from Ph. rimosus (PPC-Pr) that possessed significant antitumor activity. In this study, we examined the antiproliferative and apoptotic properties of PPC-Pr using human colon cancer cell line HCT116 as a model system. HCT116 cells were cultured in the presence of PPC-Pr at various concentrations (100-1000 μg/mL) for 24-96 hours, and the percentage of cell viability was evaluated using a 3-(4-5 dimethylthiozol-2-yl) 2-5-diphenyl-tetrazolium bromide (MTT) assay. The results showed that PPC-Pr inhibited cell viability in a time- and concentration-dependent manner. The antiproliferative effect of PPC-Pr was associated with apoptosis on HCT116 cells. We analyzed the morphological changes in the PPC-Pr-treated HCT116 cells using fluorescent DNA-microscopy with 4',6-diamidino-2-phenylindole dihydrochloride hydrate (DAPI) and acridine orange-ethidium bromide (AO/EB) staining. With DAPI staining, the cells treated with PPC-Pr showed nuclear shrinkage and chromatin condensation. Apoptotic morphology in cellular bodies as well as chromatin condensation were also confirmed by AO/EB double staining. Oligonucleosomal DNA fragmentation in PPC-Pr-treated cells was evaluated using a comet assay. The comet assay showed that control cells had few nuclei with fragmented chromatin, whereas apoptotic nuclei were more frequent in PPC-Pr-treated cells. These investigations indicate that the polysaccharide-protein complex from Ph. rimosus possesses antiproliferative activity and induces marked apoptosis in tumor cells in vitro.