Abstract
The present study was carried out to evaluate the effect of phagocytosis of killed yeast on the induction of apoptosis in two human solid tumors of the gastrointestinal (GI): the squamous cell carcinomas of the tongue (SCCA) are (SCC -4 and SCC-9) and the adenocarcinomas of the colon (ADENOCA) are (Caco-2 and DLD-1). Cancer cells were cultured with heat killed Saccharomyces cerevisiae, baker's and brewer's yeast, at ratio of yeast to cancer cells = 10:1. The percentage of tumor cells that had attached/phagocytosed yeast and oxidative burst was determined by using oxidative sensitive dye (DCFH-DA) and flow cytometry. SCC-4 and colon Caco-2 cells demonstrated initial high levels of phagocytosis that peaked (35.8-52.8%) at 2 hr. The oral SCC-9 and colon DLD-1 cells demonstrated low phagocytic activity (7-12%). Phagocytosis was not associated with oxidative burst. Upon phagocytosis of yeast, cancer cells underwent apoptosis that was maximized at 4 hr. Yeast-induced apoptosis was significant in SCC-4 (45%), as compared with SCC-9 cells (17%), and Caco-2 (76%), as compared with DLD cells (12%). Apoptosis in cancer cells was inhibited by caspase inhibitor, Z-VAD-FMK; this suggests that caspases may be involved in apoptosis of the GI cancers. This data may have clinical implications for the treatment of solid tumors.
Footnotes
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↵* Data was partially presented at The Annual Meeting of the American Academy of Otolaryngology-Head and Neck Surgery Foundation in New York, New York, September 19-22, 2004.
- Received December 2, 2004.
- Accepted January 7, 2005.
- Copyright© 2005 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved