Abstract 5004: Chemopreventive potential of Lactobacillus kefiri P-IF, a novel kefir product, on Ehrlich ascites carcinoma cells
Authors: El-Din Nariman K. Badr , Shabana Sameh , Abdulmajeed Bashar A. , Ghoneum Mamdooh 
Published: July 2017

Purpose: Lactic acid bacteria are advantageous microorganisms that exert beneficial effects for maintaining health. Our previous studies have shown that Lactobacillus kefiri P-IF, a novel kefir product, has the ability to activate dendritic cells, and to induce apoptosis in human gastric cancer cells and MDR myeloid leukemia cells in vitro. In this study, we aimed to evaluate the anticancer effect of L. kefiri P-IF against animal bearing Ehrlich Ascites Carcinoma (EAC) and investigate the mechanisms of action.

Materials and Methods: Mice were inoculated intramuscularly with EAC cells to develop solid tumors. L. kefiri P-IF was administered orally (2mg/kg/day) to mice 6 days/week, either two days before tumor cell inoculation or nine days after inoculation to mice bearing solid tumors. Tumor growth, blood lymphocyte levels, cell cycle progression, apoptosis, apoptotic regulators expression, TNF-α expression, changes in mitochondrial membrane potential (MMP), PCNA, and CD4+ and CD8+T cells in tumor cells were quantitatively evaluated by flow cytometry or RT-PCR. Further studies in vitro were carried out where EAC cells were cultured in the presence of L. kefiri P-IF at different concentrations (0, 0.6, 1.25, 2.5, and 5 mg/mL) for 1, 24, and 48 hrs. % cell viability and IC50 was estimated by MTT assay.

Results: 100% of mice that were inoculated with EAC cells alone developed tumors. Mice pretreated with L. kefiri P-IF showed tumor incidence in 76.5% of the animals. Treatment with L. kefiri P-IF markedly reduced tumor weight: 64.6% for pretreatment and 48.6% for post treatment. Mice treated with L. kefiri P-IF showed profound suppression of tumor marker PCNA expression and cell cycle arrest in the sub-G0/G1 phase, as indicated by elevation in the apoptotic cell population by 2.7 and 2.3 fold of control for pretreatment and post treatment, respectively. Pretreatment or post treatment with L. kefiri P-IF in EAC mice increased the Apoptosis index/ Proliferation index ratio by 3.4 and 2.4 fold, respectively versus control. L. kefiri P-IF treatment modulated apoptotic regulators, including upregulation of p53 expression, increased Bax/Bcl-2 ratio, decreased MMP of cancer cells, and activation of caspase-3 expression. L. kefiri P-IF intake maintained blood lymphocytes within the normal levels, increased the number of infiltrating CD4+ and CD8+ T cells within the tumor, and enhanced TNF-α expression. Finally, L. kefiri P-IF enhanced cytotoxicity against EAC cells in vitro, as shown by IC50 of 3.30 mg/ml, 1.56 mg/ml, and 1.11 mg/ml for 1, 24, and 48 hrs, respectively.

Conclusion: In conclusion, L. kefiri P-IF, a novel symbiotic microbe, may have chemopreventive potential to reduce tumor incidence and tumor growth by inducing apoptosis in EAC cells via mitochondrial dependent pathway, suppressing cell proliferation, and stimulating the immune system.

L. kefiri P-IF was provided by Paitos Co., Ltd. Yokohama, Kanagawa, Japan. .

Citation Format: Nariman K. Badr El-Din, Sameh Shabana, Bashar A. Abdulmajeed, Mamdooh Ghoneum. Chemopreventive potential of Lactobacillus kefiri P-IF, a novel kefir product, on Ehrlich ascites carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5004. doi:10.1158/1538-7445.AM2017-5004