Apoptosis of Human Multidrug-Resistant Myeloid Leukemia (HL60/AR) Cells by Thymax Plus Lactobacillus Kefiri P-IF★

We have recently reported the susceptibility of human Multidrug-Resistant (MDR) myeloid leukemia (HL60/AR) cells to the apoptotic effect of L. kefiri P-IF, a freeze-dried form of heat-killed Lactobacillus kefiri. In this study, we evaluated the synergizing apoptotic effects of L. kefiri P-IF in the presence of Thymax, a gross thymic extract, on HL60/AR cells. To identify any synergistic effect of these two agents, tumor cells were cultured for three days with 0.6-5.0 mg/ ml L. kefiri P-IF alone, 0.6-5.0 mg/ml Thymax alone, or a combination of both agents. The apoptotic response was assessed using a propidium iodide assay. The expression of Bcl-2, an anti-apoptotic protein, was determined by flow cytometry. Results showed that L. kefiri P-IF and Thymax induced apoptosis in HL60/AR cells in a dose dependent manner that was detected at 0.6 mg/mL and maximized at 5 mg/mL. However, treatment by L. kefiri P-IFplus Thymax synergistically induced higher levels of apoptosis in cancer cells that exceeds the effect of either agent alone. The synergistic apoptotic effect was associated with decreased expression of Bcl-2. This combination may represent a new class of adjuvant for the treatment of myeloid leukemia.