Role of SCFAs in gut microbiome and glycolysis for colorectal cancer therapy

Gut bacteria affect the tumoral immune milieu: distorting the efficacy of immunotherapy or not？

Immunotherapy using immune-checkpoint inhibitors is revolutionizing oncotherapy. However, the application of immunotherapy may be restricted because of the lack of proper biomarkers in a portion of cancer patients. Recently, emerging evidence has revealed that gut commensal bacteria can impact the therapeutic efficacy of immune-checkpoint inhibitors in several cancer models. In addition, testing the composition of gut bacteria provides context for prediction of the efficacy and toxicity of immunotherapy. In this review, we discuss the impacts of gut commensal bacteria on the tumoral immune milieu, highlighting some typical bacteria and their associations with immunotherapy.

Milk fermented with Lactococcus lactis KLDS4.0325 alleviates folate status in deficient mice

Folate is an essential B vitamin and its deficiency is common in many parts of the world. Natural folate produced by microorganisms may be an alternative to chemically synthesized folic acid (FA) as a dietary supplement. Previously, two lactic acid bacteria (LAB) strains, a high folate-producing Lactococcus lactis subsp. lactis KLDS4.0325 and a weak folate-producing Lactococcus lactis subsp. lactis KLDS4.0613, were identified. The aim of this study was to evaluate the effect of milk fermented with L. lactis KLDS4.0325 (folate-enriched fermented milk, FEFM) in alleviating folate deficiency status using murine folate deficiency models. In addition, the link between gut microbiota diversity and folate levels in mice was investigated. Results showed that FEFM increased FA and 5-methyltetrahydrofolate (5-MTHF) concentrations in the whole blood and liver, and decreased plasma homocysteine (Hcy) levels. 16S rDNA sequence analysis also revealed that the supplementation of FEFM (containing 0.6 μg mL^-1 folate) and 0.6 μg d^-1 FA (FEFM + LFA) significantly improved the poor status of the gut microbiota composition caused by folate deficiency, and the effect was better than that with 1.2 μg d^-1 FA (HFA) supplementation. Our findings show that FEFM can be used as a folate-fortified food to alleviate folate deficiency effectively. In addition, it may be considered as a partial or total replacement for synthetic FA.

Sodium butyrate modulates gut microbiota and immune response in colorectal cancer liver metastatic mice

Colorectal cancer (CRC) liver metastasis (CLM) is the leading death cause of CRC patients, but there is no satisfied approach to treat CLM. Gut microbiota plays a pivotal role in CRC initiation and development. Targeting dysbiosis of the gut microbiota might open up new opportunities for CLM treatment. Here, we investigated the efficacy of sodium butyrate (NaB), a major product of gut microbial fermentation, in modulating gut microbiota in CLM mice. NaB supplement decreased mouse colon cancer CT26 cell liver metastasis in intrasplenic tumor injection model of BALB/c mice. Using 16S rRNA gene sequencing, we found altered microbiota composition in CLM mice, characterized by increases of Firmicutes and Proteobacteria. NaB beneficially changed dysbiosis in CLM mice. Functional analysis of the KEGG pathways showed that NaB changed pathways related to immune system diseases and primary immunodeficiency in CLM mice. In addition, NaB decreased T regulatory cells and increased natural killer T cells and T helper 17 cells, accordingly decreased IL-10 and increased IL-17 secretion in CLM mice liver. In conclusion, NaB beneficially modulated gut microbiota and improved host immune response in CLM mice. These findings demonstrate the therapeutic potential of NaB in CLM treatment.

Comparative effect of sodium butyrate and sodium propionate on proliferation, cell cycle and apoptosis in human breast cancer cells MCF-7

INTRODUCTION

Short-chain fatty acids (SCFAs) are ubiquitous lipids produced as a result of bacterial fermentation of dietary fiber. While their role in colorectal cancer is well known, the effect of SCFAs in breast cancer is poorly defined.

OBJECTIVE

To understand the various effects of SCFAs on breast carcinogenesis, we investigated the effect of sodium butyrate (NaB) and sodium propionate (NaP) in MCF-7 cell line.

MATERIALS AND METHODS

Cells were incubated with different concentrations of NaB or NaP for 24, 48, 72 or 96 h. Cell proliferation was assayed using MTT kit. Cell cycle was performed using propidium iodide staining then analyzed with a flow cytometer. Apoptosis was assessed by Hoechst technique and cell-cycle sub-G1 phase.

RESULTS

NaB and NaP inhibited MCF-7 cell proliferation in a dose-dependent manner with respective IC₅₀ of 1.26 mM and 4.5 mM, thus indicating that NaB is more potent than NaP. Low and medium levels of both SCFAs induced morphology changes which are characteristic of a differentiated phenotype. Flow cytometry analysis revealed a blockage in G1 growth phase. Interestingly, removing NaB or NaP from culture media after few days of treatment showed a reversible effect on cell morphology and proliferation where cells reentered the cycle after 24 h of drug wash-out. Finally, treatment with medium levels of these molecules induced low MCF-7 apoptosis, while higher doses led to massive apoptosis.

CONCLUSION

Our results show that SCFAs may be considered as an interesting inhibitor for breast cancer progression.

Effect of Short Chain Fatty Acids on Age-Related Disorders

Recent studies have indicated a prominent role of intestinal microbiota in regulation of several physiological aspects of the host including development and activation of the immune system and control of metabolism. In this review, we focused our discussion on bacterial metabolites produced from dietary fiber fermentation called short-chain fatty acids, which act as a link between the microbiota and host cells. Specifically, we described how modifications in their intestinal levels are associated with development of age-related pathologies including metabolic diseases and type 2 diabetes, hypertension, cardiovascular and neurodegenerative diseases. We also highlight their impact on the development of cancer.

Gut butyrate-producing organisms correlate to Placenta Specific 8 protein: Importance to colorectal cancer progression

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Genes from stools have molecular significance with CRC tumorgenesis.

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SCFAs, the metabolites of microbiota, can suppress CRC tumorigenesis.

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Relationship between colonic genes, gut microbiota, or their metabolites is significant.

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Changes of PLAC8 and butyrate-producing organisms were found in stools of CRC patients.

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Butyrate can reduce the CRC formation through regulating PLAC8 expression.

Tumor metastasis or recurrence often occurs in patients with curative resection of colorectal cancer (CRC). Placental-specific 8 (PLAC8), which has increased expression in stool, may be associated with CRC recurrence. Insights into the role of PLAC8 in CRC recurrence and its clinical significance may support to develop strategies for preventing CRC recurrence and deterioration. Clinical tissues, cell and animal models were used to clarify the roles of PLAC8 in CRC tumorigenesis, invasion, and migration. Next-generation sequencing of 16S ribosomal DNA has been used to assess the gut microbiota in stool of CRC patients. We found that PLAC8 was upregulated in tissues from patients with late-stage CRC. In our in vitro studies, PLAC8 was dynamically regulated in mitotic cells. Overexpressed PLAC8 was nucleated at the centrosome during mitosis, and therefore, PLAC8 overexpression might increase cell growth and migration (all p < 0.05). The tumorigenic and invasive effects of PLAC8 on CRC cells were also confirmed in a xenograft mouse model. We further identified reduced levels of two butyrate-producing organisms, Butyricicoccus and Prevotella spp., in stools from CRC patients. We found that butyrate downregulated PLAC8 expression and induced apoptosis in PLAC8-overexpressing cells. Our data suggests that PLAC8 gene and protein expression and dysbiosis of gut microflora, especially in butyrate-producing microorganisms, may be indicators of CRC progression.