Inflammation and Cancer: Triggers, Mechanisms, and Consequences.

Growing evidence suggests that microbes can influence the efficacy of cancer therapies. By studying colon cancer models, we found that bacteria can metabolize the chemotherapeutic drug gemcitabine (2',2'-difluorodeoxycytidine) into its inactive form, 2',2'-difluorodeoxyuridine. Metabolism was dependent on the expression of a long isoform of the bacterial enzyme cytidine deaminase (CDDL), seen primarily in Gammaproteobacteria. In a colon cancer mouse model, gemcitabine resistance was induced by intratumor Gammaproteobacteria, dependent on bacterial CDDL expression, and abrogated by cotreatment with the antibiotic ciprofloxacin. Gemcitabine is commonly used to treat pancreatic ductal adenocarcinoma (PDAC), and we hypothesized that intratumor bacteria might contribute to drug resistance of these tumors. Consistent with this possibility, we found that of the 113 human PDACs that were tested, 86 (76%) were positive for bacteria, mainly Gammaproteobacteria.

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Potential role of intratumor bacteria in mediating tumor resistance to the chemotherapeutic drug gemcitabine.

Colorectal cancers comprise a complex mixture of malignant cells, nontransformed cells, and microorganisms. Fusobacterium nucleatum is among the most prevalent bacterial species in colorectal cancer tissues. Here we show that colonization of human colorectal cancers with Fusobacterium and its associated microbiome—including Bacteroides , Selenomonas , and Prevotella species—is maintained in distal metastases, demonstrating microbiome stability between paired primary and metastatic tumors. In situ hybridization analysis revealed that Fusobacterium is predominantly associated with cancer cells in the metastatic lesions. Mouse xenografts of human primary colorectal adenocarcinomas were found to retain viable Fusobacterium and its associated microbiome through successive passages. Treatment of mice bearing a colon cancer xenograft with the antibiotic metronidazole reduced Fusobacterium load, cancer cell proliferation, and overall tumor growth. These observations argue for further investigation of antimicrobial interventions as a potential treatment for patients with Fusobacterium -associated colorectal cancer.

Analysis of Fusobacterium persistence and antibiotic response in colorectal cancer

Metastasis is the hallmark of cancer that is responsible for the greatest number of cancer-related deaths. Yet, it remains poorly understood. The continuous evolution of cancer biology research and the emergence of new paradigms in the study of metastasis have revealed some of the molecular underpinnings of this dissemination process. The invading tumor cell, on its way to the target site, interacts with other proteins and cells. Recognition of these interactions improved the understanding of some of the biological principles of the metastatic cell that govern its mobility and plasticity. Communication with the tumor microenvironment allows invading cancer cells to overcome stromal challenges, settle, and colonize. These characteristics of cancer cells are driven by genetic and epigenetic modifications within the tumor cell itself and its microenvironment. Establishing the biological mechanisms of the metastatic process is crucial in finding open therapeutic windows for successful interventions. In this review, the authors explore the recent advancements in the field of metastasis and highlight the latest insights that contribute to shaping this hallmark of cancer.

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Molecular principles of metastasis: a hallmark of cancer revisited

Colorectal cancer (CRC) is among the most lethal and prevalent malignancies in the world and was responsible for nearly 881,000 cancer-related deaths in 2018. Surgery and chemotherapy have long been the first choices for cancer patients. However, the prognosis of CRC has never been satisfying, especially for patients with metastatic lesions. Targeted therapy is a new optional approach that has successfully prolonged overall survival for CRC patients. Following successes with the anti-EGFR (epidermal growth factor receptor) agent cetuximab and the anti-angiogenesis agent bevacizumab, new agents blocking different critical pathways as well as immune checkpoints are emerging at an unprecedented rate. Guidelines worldwide are currently updating the recommended targeted drugs on the basis of the increasing number of high-quality clinical trials. This review provides an overview of existing CRC-targeted agents and their underlying mechanisms, as well as a discussion of their limitations and future trends.

/pdf/comprehensive-review-of-targeted-therapy-for-colorectal-3ed735uy8v.pdf

Comprehensive review of targeted therapy for colorectal cancer

Fusobacterium nucleatum Promotes Chemoresistance to Colorectal Cancer by Modulating Autophagy.

Genome-wide association studies (GWASs) implicate 16q22.1 locus in risk for colorectal cancer (CRC). However, the underlying oncogenic mechanisms remain unknown. Here, through comprehensive filtration, we prioritized rs7198799, a common SNP in the second intron of the CDH1, as the putative causal variant. In addition, we found an association of CRC-risk allele C of rs7198799 with elevated transcript level of biological plausible candidate gene ZFP90 via expression quantitative trait loci analysis. Mechanistically, causal variant rs7198799 resides in an enhancer element and remotely regulate ZFP90 expression by targeting the transcription factor NFATC2. Remarkably, CRISPR/Cas9-guided single-nucleotide editing demonstrated the direct effect of rs7198799 on ZFP90 expression and CRC cellular malignant phenotype. Furthermore, ZFP90 affects several oncogenic pathways, including BMP4, and promotes carcinogenesis in patients and in animal models with ZFP90 specific genetic manipulation. Taken together, these findings reveal a risk SNP-mediated long-range regulation on the NFATC2-ZFP90-BMP4 pathway underlying the initiation of CRC.

/pdf/a-16q22-1-variant-confers-susceptibility-to-colorectal-4lbmvef78q.pdf

A 16q22.1 variant confers susceptibility to colorectal cancer as a distal regulator of ZFP90.

Chronic inflammation and gut microbiota dysbiosis are risk factors for colorectal cancer. In clinical practice, patients with inflammatory bowel disease (IBD) have a greatly increased risk of developing colitis-associated colorectal cancer (CAC). However, the underlying mechanism of the initiation of CAC remains unknown. Systematic analyses using an existing genome-wide association study (GWAS) and conditional deletion of Zfp90 (encoding zinc finger protein 90 homolog) in a CAC mouse model indicated that Zfp90 is a putative oncogene in CAC development.Strikingly, depletion of the gut microbiota eliminated the tumorigenic effect of Zfp90 in the CAC mouse model. Moreover, fecal microbiota transplantation demonstrated that Zfp90 promoted CAC dependent on the gut microbiota. Analysis of 16s rDNA sequences in fecal specimens from the CAC mouse model allowed us to speculate that a Prevotella copri-defined microbiota might mediate the oncogenic role of Zfp90 in the development of CAC. Mechanistic studies revealed Zfp90 accelerated CAC development through the TLR4-PI3K-AKT-NF-κB pathway. Our findings revealed the crucial role of the Zfp90-microbiota-NF-κB axis in creating a tumor-promoting environment and suggested therapeutic targets for CAC prevention and treatment.

https://www.tandfonline.com/doi/pdf/10.1080/19490976.2021.1917269

ZFP90 drives the initiation of colitis-associated colorectal cancer via a microbiota-dependent strategy.

Epidemiological studies have indicated an association between statin use and reduced incidence of colorectal cancer (CRC), and work in preclinical models has demonstrated a potential chemopreventive effect. Statins are also associated with reduced dysbiosis in the gut microbiome, yet the role of the gut microbiome in the protective effect of statins in CRC is unclear. Here we validated the chemopreventive role of statins by retrospectively analysing a cohort of patients who underwent colonoscopies. This was confirmed in preclinical models and patient cohorts, and we found that reduced tumour burden was partly due to statin modulation of the gut microbiota. Specifically, the gut commensal Lactobacillus reuteri was increased as a result of increased microbial tryptophan availability in the gut after atorvastatin treatment. Our in vivo studies further revealed that L. reuteri administration suppressed colorectal tumorigenesis via the tryptophan catabolite, indole-3-lactic acid (ILA). ILA exerted anti-tumorigenic effects by downregulating the IL-17 signalling pathway. This microbial metabolite inhibited T helper 17 cell differentiation by targeting the nuclear receptor, RAR-related orphan receptor γt (RORγt). Together, our study provides insights into an anti-cancer mechanism driven by statin use and suggests that interventions with L. reuteri or ILA could complement chemoprevention strategies for CRC. 

https://doi.org/10.1038/s41564-023-01363-5

Ji-Xuan Han

Papers

Fusobacterium nucleatum Promotes Chemoresistance to Colorectal Cancer by Modulating Autophagy.

A 16q22.1 variant confers susceptibility to colorectal cancer as a distal regulator of ZFP90.

ZFP90 drives the initiation of colitis-associated colorectal cancer via a microbiota-dependent strategy.

Microbiota-derived tryptophan catabolites mediate the chemopreventive effects of statins on colorectal cancer