The pro-apoptotic effect of kefir in malignant T-lymphocytes involves a p53 dependent pathway

Abstract

Context: Kefir is an important probiotic that contains many bioactive ingredients which give it unique health benefits. Several studies have reported the anti-tumor effect of kefir on certain types of cancer. Adult lymphoblastic Leukemia (ALL) characterized by the continuous division of white blood cells in the bone marrow, and Adult T Cell Leukemia (ATL) a malignancy of activated T lymphocytes caused by Human T-cell Lymphotropic Virus type 1 (HTLV-1) will be addressed in this study. Objective: The aim of this study is to inspect the effect of a cell-free fraction of kefir on the induction of apoptosis in two malignant T-lymphocyte cell lines. Methods: CEM cells (HTLV-1 negative) and HUT-201 cells (HTLV-1 positive) leukemic cells were incubated with different concentrations of a cell free fraction of kefir. Apoptosis induction was measured using Cell Death Elisa, as well as annexin labeling followed by flow cytometry . The molecular mechanism underlying apoptosis induction was further investigated by western blots to assess the expression of the proapoptotic protein Bax, the anti-apoptotic protein Bcl-2, and p53. Results: Previous work in our lab has shown the anti-proliferative effect of kefir in both HTLV-1 negative as well as HTLV-1 positive leukemic cell lines with no significant cytotoxic effect on normal lymphocytes. We now report a dose- and time-dependent proapoptotic effect of kefir on both cell lines using Cell Death Elisa; this was further confirmed using annexin staining followed by flow cytomtery analysis. Furthermore, kefir treatment did not alter p53 expression, even though it caused an up-regulation of Bax proteins and a down-regulation of Bcl-2 in a dose and time dependent manner in both cell lines. This confirms the pro-apoptotic effect of kefir via a p53-independent mechanism in HTLV-1 negative and HTLV-1 positive cell lines. Conclusion: These results suggest that milk kefir is a promising food component in terms of cancer prevention. Further studies should aim at identifying the active ingredient in kefir responsible for its anti-tumor effect, and assessing its activity in vivo.