An Investigation of the Complex Effects of a Saccharomyces cerevisiae Cytoplasmic Extract on Apoptosis in K562 Cells

Background: Saccharomyces cerevisiae, a common probiotic, can induce in vitro apoptosis in human cancer cells, which could explain its antitumor activity. Objectives: The present study was conducted to investigate the in vitro effects of a cytoplasmic extract from S. cerevisiae on the proliferation and viability of a K562 (chronic myeloid leukemia) cell line. Methods: S. cerevisiae was cultured and then disrupted by sonication. After centrifugation, the harvested supernatant was considered to be a cytoplasmic extract. The protein concentration was determined by the Biuret method and the extract was diluted to concentrations of 500, 1000, and 2000 mu g protein/ml. The frequencies of apoptosis and necrosis were assessed in extract-treated K562 cells by electrophoresis to show DNA segmentation and by flow cytometry. Results: The cytoplasmic extract exhibited a time-dependent antitumor activity. DNA electrophoresis did not reveal apoptosis and necrosis in the treated cells, but the DNA bands were weak. The flow cytometry results indicated the induction of apoptosis as well as necrosis in the K562 cell line and the intensity of apoptosis increased with time. Conclusions: The cytoplasmic extract of S. cerevisiae investigated here may inhibit cell growth and induce apoptosis of chronic myeloid leukemia cells.