Deciphering the Colorectal Cancer Gut Microbiota: Association vs. Causality

Tumor bacterial markers diagnose the initiation and four stages of colorectal cancer

Increasing evidence has supported dysbiosis in the faecal microbiome along control-adenoma-carcinoma sequence. In contrast, the data is lacking for in situ tumor bacterial community over colorectal cancer (CRC) progression, resulting in the uncertainties of identifying CRC-associated taxa and diagnosing the sequential CRC stages. Through comprehensive collection of benign polyps (BP, N = 45) and the tumors (N = 50) over the four CRC stages, we explored the dynamics of bacterial communities over CRC progression using amplicons sequencing. Canceration was the primarily factor governing the bacterial community, followed by the CRC stages. Besides confirming known CRC-associated taxa using differential abundance, we identified new CRC driver species based on their keystone features in NetShift, including Porphyromonas endodontalis, Ruminococcus torques and Odoribacter splanchnicus. Tumor environments were less selective for stable core community, resulting in heterogeneity in bacterial communities over CRC progression, as supported by higher average variation degree, lower occupancy and specificity compared with BP. Intriguingly, tumors could recruit beneficial taxa antagonizing CRC-associated pathogens at CRC initiation, a pattern known as “cry-for-help”. By distinguishing age- from CRC stage-associated taxa, the top 15 CRC stage-discriminatory taxa contributed an overall 87.4% accuracy in diagnosing BP and each CRC stage, in which no CRC patients were falsely diagnosed as BP. The accuracy of diagnosis model was unbiased by human age and gender. Collectively, our findings provide new CRC-associated taxa and updated interpretations for CRC carcinogenesis from an ecological perspective. Moving beyond stratifying case-control, the CRC-stage discriminatory taxa could add the diagnosis of BP and the four CRC stages, especially the patients with poor pathological feature and un-reproducibility between two observers.

Genomic, Microbial and Immunological Microenvironment of Colorectal Polyps

Simple Summary

Colorectal cancers (CRC) initiate from small cell clusters known as polyps. Colonoscopic surveillance and removal of polyps is an important strategy to prevent CRC progression. Recent advances in sequencing technologies have highlighted genetic mutations in polyps that potentially contribute to CRC development. However, CRC might be considered more than a genetic disease, as emerging evidence describes early changes to immune surveillance and gut microbiota in people with polyps. Here, we review the molecular landscape of colorectal polyps, considering their genomic, microbial and immunological features, and discuss the potential clinical utility of these data.

Abstract

Colorectal cancer (CRC) develops from pre-cancerous cellular lesions in the gut epithelium, known as polyps. Polyps themselves arise through the accumulation of mutations that disrupt the function of key tumour suppressor genes, activate proto-oncogenes and allow proliferation in an environment where immune control has been compromised. Consequently, colonoscopic surveillance and polypectomy are central pillars of cancer control strategies. Recent advances in genomic sequencing technologies have enhanced our knowledge of key driver mutations in polyp lesions that likely contribute to CRC. In accordance with the prognostic significance of Immunoscores for CRC survival, there is also a likely role for early immunological changes in polyps, including an increase in regulatory T cells and a decrease in mature dendritic cell numbers. Gut microbiotas are under increasing research interest for their potential contribution to CRC evolution, and changes in the gut microbiome have been reported from analyses of adenomas. Given that early changes to molecular components of bowel polyps may have a direct impact on cancer development and/or act as indicators of early disease, we review the molecular landscape of colorectal polyps, with an emphasis on immunological and microbial alterations occurring in the gut and propose the potential clinical utility of these data.

Lipopolysaccharide promotes metastasis via acceleration of glycolysis by the nuclear factor-κB/snail/hexokinase3 signaling axis in colorectal cancer

BACKGROUND

Cancer cell is generally characterized by enhanced glycolysis. Inflammasome activation is interaction with glycolysis. The concentration of lipopolysaccharide (LPS), a classic inflammasome activator, is significantly higher in colorectal cancer tissue than in normal intestinal mucosa. However, the mechanism of LPS on glycolysis and metastasis has not been fully elucidated. This study aimed to investigate the roles of LPS on inflammasome activation, glycolysis, and metastasis, and unravel metformin's potential in treatment of CRC.

METHODS

We detected inflammasome activation and cell motility following LPS exposure in CRC cell lines. Glycolysis analysis was performed, and the key glycolytic rate-limiting enzymes were detected. Dual-luciferase reporter gene assay, co-immunoprecipitation, chromatin immunoprecipitation (ChIP) analysis, and ChIP-reChIP assay were performed to identify the specific mechanisms of LPS on glycolysis. Mouse metastasis models were used to determine the effects of LPS and metformin on metastasis. Correlation analysis of the expression of various molecules was performed in 635 CRC samples from The Cancer Genome Atlas and 83 CRC samples from our lab.

RESULTS

LPS activates caspase-1 through NF-κB and upregulates the expression of Snail and HK3 depending on caspase-1 activation. LPS potentiates migration and invasion depending on accelerated glycolysis, which could be reversed by knockdown of glycolytic rate-limiting enzyme HK3. Nuclear Snail is upregulated by NF-κB under LPS treatment and then forms a complex with NF-κB, then directly binds to the HK3 promoter region to upregulate the expression of HK3. Metformin suppresses the NF-κB/Snail/HK3 signaling axis that is activated by LPS and then inhibits LPS-induced metastasis. In vivo, LPS-treated cells form more metastasis in the lungs of mice, and metformin completely reverses this effect of LPS.

CONCLUSION

LPS activates inflammasomes in cancer cells through NF-κB and promotes metastasis through glycolysis enhanced by the NF-κB/Snail/HK3 signaling pathway in CRC. Metformin could prevent this effect of LPS.

Cell primitive-based biomimetic functional materials for enhanced cancer therapy

Cell primitive-based functional materials that combine the advantages of natural substances and nanotechnology have emerged as attractive therapeutic agents for cancer therapy. Cell primitives are characterized by distinctive biological functions, such as long-term circulation, tumor specific targeting, immune modulation etc. Moreover, synthetic nanomaterials featuring unique physical/chemical properties have been widely used as effective drug delivery vehicles or anticancer agents to treat cancer. The combination of these two kinds of materials will catalyze the generation of innovative biomaterials with multiple functions, high biocompatibility and negligible immunogenicity for precise cancer therapy. In this review, we summarize the most recent advances in the development of cell primitive-based functional materials for cancer therapy. Different cell primitives, including bacteria, phages, cells, cell membranes, and other bioactive substances are introduced with their unique bioactive functions, and strategies in combining with synthetic materials, especially nanoparticulate systems, for the construction of function-enhanced biomaterials are also summarized. Furthermore, foreseeable challenges and future perspectives are also included for the future research direction in this field.