A novel purified Lactobacillus acidophilus 20079 exopolysaccharide, LA-EPS-20079, molecularly regulates both apoptotic and NF-\u03baB inflammatory pathways in human colon cancer

Nehal M El-Deeb,Abdelrahman M Yassin,Lamiaa A Al-Madboly,Amr El-Hawiet

doi:10.1186/s12934-018-0877-z

Abstract

BackgroundThe direct link between inflammatory bowel diseases and colorectal cancer is well documented. Previous studies have reported that some lactic acid bacterial strains could inhibit colon cancer progression however; the exact molecules involved have not yet been identified. So, in the current study, we illustrated the tumor suppressive effects of the newly identified Lactobacillus acidophilus DSMZ 20079 cell-free pentasaccharide against colon cancer cells. The chemical structure of the purified pentasaccharide was investigated by MALDI-TOF mass spectrum, 1D and 2D Nuclear Magnetic Resonance (NMR). The anticancer potentiality of the purified pentasaccharide against both Human colon cancer (CaCo-2) and Human breast cancer (MCF7) cell lines with its safety usage pattern were evaluated using cytotoxicity, annexin V quantification and BrdU incorporation assays. Also, the immunomodulatory effects of the identified compound were quantified on both LPS-induced PBMC cell model and cancer cells with monitoring the immunophenotyping of T and dendritic cell surface marker. At molecular level, the alteration in gene expression of both inflammatory and apoptotic pathways were quantified upon pentasaccharide-cellular treatment by RTqPCR.ResultsThe obtained data of the spectroscopic analysis, confirmed the structure of the newly extracted pentasaccharide; (LA-EPS-20079) to be: α-d-Glc (1→2)][α-l-Fuc(1→4)] α-d-GlcA(1→2) α-d-GlcA(1→2) α-d-GlcA. This pentasaccharide, recorded safe dose on normal mammalian cells ranged from 2 to 5 mg/ml with cancer cells selectivity index, ranged of 1.96–51.3. Upon CaCo-2 cell treatment with the non-toxic dose of LA-EPS-20079, the inhibition percentage in CaCo-2 cellular viability, reached 80.65 with an increase in the ratio of the apoptotic cells in sub-G0/G1 cell cycle phase. Also, this pentasaccharide showed potentialities to up-regulate the expression of IKbα, P53 and TGF genes.ConclusionThe anticancer potentialities of LA-EPS-20079 oligosaccharides against human colon cancer represented through its regulatory effects on both apoptotic and NF-κB inflammatory pathways.

Highlights

The direct link between inflammatory bowel diseases and colorectal cancer is well documented
The characteristic chemical shifts of 1.27 ppm in 1H-Nuclear Magnetic Resonance (NMR) spectrum and 16.24 ppm in 13C-NMR spectrum resonances was assigned for H6 and C6, respectively, of a 6-deoxyhexose which was assigned as fucose
The MALDI-TOF mass spectrum, in the positive mode, of LA-EPS-20079, showed a single peak at m/z 877.109, corresponding to a compound of molecular formula, C30H46O28Na that was attributed to the pseudomolecular ion [M + Na]+

Summary

Introduction

The direct link between inflammatory bowel diseases and colorectal cancer is well documented. In the current study, we illustrated the tumor suppressive effects of the newly identified Lactobacillus acidophilus DSMZ 20079 cell-free pentasaccharide against colon cancer cells. The majority of conventional chemotherapeutic agents, targeting actively dividing cells, do not show selective toxicity towards cancer cells leading to healthy cell damage. Cancer cells might develop resistance to conventional chemotherapeutic agents through various mechanisms, such as, increased expression of drug detoxifying enzymes and drug transporters and increased ability to repair DNA defects in cellular machinery that mediate apoptosis [3]. There is a pressing demand for targeted therapies that are capable of killing cancer cells selectively without affecting normal healthy cells or at least to act as adjuvants to lower the therapeutic doses and increase efficiency of conventional anticancer drugs. Synthesis of exopolysaccharides by lactic acid bacteria (LAB) is a well-known phenomenon which exists as a cell-bound EPS, adhering closely to the bacterial surface, or releases EPS into the surrounding medium [4]

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Conclusion