Fractionation and Characterization of Bioactive Components in Kefir Mother Culture that Inhibit Proliferation of Cultured MCF-7 Human Breast-Cancer Cells

Breast cancer is the most commonly diagnosed cancer in women. Resistance to therapy is the major reason for failure of cancer treatment (Mesner et al., 1997). There is a critical need to identify new chemotherapeutic agents that can increase susceptibility to anti-breast cancer drugs or overcome resistance mechanisms, which would improve patient outcomes, prevent relapse, and prolong patient survival. Kefir is an acidic and mildly alcoholic fermented milk that originated in the Caucasian mountains of former Soviet Union, and enjoys a rich tradition of health benefits. Consumption of fermented dairy foods has been associated with lower incidence of breast cancer (Ronco et al., 2002). Research on the putative health benefits of fermented milks suggested that by-products of bacterial fermentation of proteins, lipids and carbohydrates present in fermented milks exert health benefits beyond basic nutrition including anti-tumor action, immune system enhancement and antioxidant effects (Parvez et al., 2006). Conjugated linoleic acid (Schonberg et al., 1995), sphingolipids (Dillehay et al., 1994), polysaccharides (Shiomi et al., 1982), organic acids (Garrote et al., 2000) and some proteins and peptides (Svensson et al., 1999) have been shown to have antimutagenic and antitumor effects. Promising results regarding anti-tumor activity of yogurt extracts in cell culture (Biffi et al., 1997) and kefir extracts in animal feeding studies (Cervikbas et al., 1994; Furukawa et al., 2000; Shiomi et al., 1982) have been reported. However, the bioactive components in kefir and the mechanisms involved in the various biofunctional effects of kefir are still not well characterized, particularly in terms of anti-cancer activities. In our recent studies, kefir extracts exerted potent anti-proliferative effects on cultured human mammary tumor cells as compared to extracts of yogurt or milk (Chen et al., 2007). The aim of the present study was to fractionate and characterize bioactive components in kefir mother culture that exert antiproliferative effects in MCF-7 cells.