Abstract 5500: Sensitivity of metastatic breast cancer (4T1) cells to apoptotic effect by Lactobacillus kefiri P-IF via a mechanism that involves hole piercing in cancer cells

Abstract

Abstract Objective: Metastasis, the spread of cancer from its origin, is primarily responsible for the majority of deaths from human solid-organ cancer. Lactobacillus kefiri P-IF, a freeze-dried form of heat-killed L. kefiri, is a specific strain of lactic acid bacteria that has a unique DNA sequence and PET scans showing a 99.6% homology with regular kefiris. In the current study, we evaluate the apoptotic effect of L. kefiri P-IF on metastatic breast cancer (MBC) cells. Materials and Methods: 4T1, murine MBC, were cultured with different concentrations of L.kefiri P-IF (0, 1.25, 2.5 and 5 mg/ml) and the apoptotic response was assessed by propidium iodide assay and trypan blue exclusion test. Changes in mitochondrial membrane potential (MMP) were monitored by flow cytometry. Changes in percentages of cancer cells bearing holes were examined by Giemsa-stained cytospin preparation under a light microscope. Results: L.kefiri P-IF induced apoptosis in 4T1 cells. Incubation with L. Kefiri P-IF at 5 mg/ml induced apoptosis in 91% of 4T1 cells compared to 7% apoptosis for control untreated cells. A significant apoptotic effect by L.kefiri P-IF was detected as early as 90 min post exposure with cancer cells, showing 25 fold increase in apoptotic non-adherent cells as compared to control untreated cells. The apoptotic effect was further increased 30 to 75 fold at 24 and 48 hours, respectively. The induction of apoptosis by L.kefiri P-IF was associated with significant decrease in the polarization of MMP and an increase in the percentages of adherent cells bearing multiple holes, suggesting that the mechanism by which L.kefiri P-IF induces its apoptotic effect involves piercing holes in cancer cells. Thes holes are shown to vary in circumference and depth. Control untreated adherent cells showed 40% cells with no holes and 43% cells bearing more than 5 holes. In contrast, L.kefiri P-IF treated adherent cells showed only 7% cells with no holes, while cells bearing more than 5 holes reached 87 %, this represents a 2 fold increase in cells with multiple holes over control cells. Conclusion: These results suggest that L.kefiri P-IF exerts an apoptotic effect on MBC cells by a mechanism that involves the hole piercing in cancer cells, and may represent a new class of adjuvants for the treatment of metastatic breast cancer. L.kefiri P-IF was provided by Paitos Co., Ltd. Yokohama, Kanagawa, Japan. Citation Format: Mamdooh H. Ghoneum. Sensitivity of metastatic breast cancer (4T1) cells to apoptotic effect by Lactobacillus kefiri P-IF via a mechanism that involves hole piercing in cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5500. doi:10.1158/1538-7445.AM2014-5500