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

Colorectal cancer (CRC) is the third most common cancer and the fourth most common cause of cancer-related death. Most cases of CRC are detected in Western countries, with its incidence increasing year by year. The probability of suffering from colorectal cancer is about 4%–5% and the risk for developing CRC is associated with personal features or habits such as age, chronic disease history and lifestyle. In this context, the gut microbiota has a relevant role, and dysbiosis situations can induce colonic carcinogenesis through a chronic inflammation mechanism. Some of the bacteria responsible for this multiphase process include Fusobacterium spp, Bacteroides fragilis and enteropathogenic Escherichia coli. CRC is caused by mutations that target oncogenes, tumour suppressor genes and genes related to DNA repair mechanisms. Depending on the origin of the mutation, colorectal carcinomas can be classified as sporadic (70%); inherited (5%) and familial (25%). The pathogenic mechanisms leading to this situation can be included in three types, namely chromosomal instability (CIN), microsatellite instability (MSI) and CpG island methylator phenotype (CIMP). Within these types of CRC, common mutations, chromosomal changes and translocations have been reported to affect important pathways (WNT, MAPK/PI3K, TGF-β, TP53), and mutations; in particular, genes such as c-MYC, KRAS, BRAF, PIK3CA, PTEN, SMAD2 and SMAD4 can be used as predictive markers for patient outcome. In addition to gene mutations, alterations in ncRNAs, such as lncRNA or miRNA, can also contribute to different steps of the carcinogenesis process and have a predictive value when used as biomarkers. In consequence, different panels of genes and mRNA are being developed to improve prognosis and treatment selection. The choice of first-line treatment in CRC follows a multimodal approach based on tumour-related characteristics and usually comprises surgical resection followed by chemotherapy combined with monoclonal antibodies or proteins against vascular endothelial growth factor (VEGF) and epidermal growth receptor (EGFR). Besides traditional chemotherapy, alternative therapies (such as agarose tumour macrobeads, anti-inflammatory drugs, probiotics, and gold-based drugs) are currently being studied to increase treatment effectiveness and reduce side effects.

/pdf/colorectal-carcinoma-a-general-overview-and-future-2e96vugrtz.pdf

Colorectal Carcinoma: A General Overview and Future Perspectives in Colorectal Cancer

Circular RNA cSMARCA5 inhibits growth and metastasis in hepatocellular carcinoma.

Fusobacterium nucleatum has long been found to cause opportunistic infections and has recently been implicated in colorectal cancer; however, it is a common member of the oral microbiota and can have a symbiotic relationship with its hosts. To address this dissonance, we explore the diversity and niches of fusobacteria and reconsider historic fusobacterial taxonomy in the context of current technology. We also undertake a critical reappraisal of fusobacteria with a focus on F. nucleatum as a mutualist, infectious agent and oncogenic microorganism. In this Review, we delve into recent insights and future directions for fusobacterial research, including the current genetic toolkit, our evolving understanding of its mechanistic role in promoting colorectal cancer and the challenges of developing diagnostics and therapeutics for F. nucleatum.

/pdf/fusobacterium-nucleatum-symbiont-opportunist-and-1rnank755u.pdf

Fusobacterium nucleatum - symbiont, opportunist and oncobacterium.

Influence of the Gut Microbiome, Diet, and Environment on Risk of Colorectal Cancer

Association of Fusobacterium nucleatum infection with colorectal cancer in Chinese patients

MicroRNAs have emerged as crucial regulators of tumorigenesis. However, it remains unknown whether miR-181a is involved in the pathogenesis of gastric cancer. In this study, we found that miR-181a is overexpressed in human gastric cancer tissues. Ectopic expression of miR-181a mimic promoted the proliferation, colony formation, migration, and invasion and inhibited the apoptosis of SGC-7901 gastric cancer cells, whereas ectopic expression of miR-181a inhibitor inhibited the malignant phenotypes of SGC-7901 cells. Site-directed mutagenesis and luciferase reporter assay demonstrated that miR-181a repressed KLF6 expression by targeting its 3'-UTR. Western blot analysis further showed that KLF6 protein was significantly decreased or increased when miR-181a mimic or inhibitor was transfected into SGC-7901 cells, respectively. In summary, these data suggest that KLF6 gene is a direct target of miR-181a and miR-181a functions as an oncomir in gastric cancer by repressing the expression of tumor suppressor KLF6.

MicroRNA-181a promotes gastric cancer by negatively regulating tumor suppressor KLF6

Recent evidences show that genetic polymorphisms falling in miRNA binding sites can alter the strength of miRNA binding and disturb miRNA-mediated posttranscriptional regulation. Our study aimed to investigate the role of single-nucleotide polymorphisms (SNPs) in putative miRNA binding sites in gastric cancer (GC). Based on microarray and quantitative reverse transcription PCR analyses, we found that miR-181a was significantly upregulated in GC tissues. Bioinformatics survey was used to explore SNPs within miR-181a binding sites. Three SNPs were genotyped in a case-control study (500 cases and 502 controls). The T allele genotypes (rs12537CT and TT) of MTMR3 were found associated with significantly increased GC risk [adjusted odds ratio 1.72, 95% confidence interval (CI) 1.36-2.16, P = 3.99×10(-5)] and poor overall survival [hazard ratio (HR) 1.38, 95% CI 1.03-1.83, P = 0.029], although they were not an independent prognostic factor in multivariate Cox regression analysis (HR 1.28, 95% CI 0.95-1.72, P = 0.11). We further demonstrated that the rs12537CT genotype carriers had lower MTMR3 mRNA expression levels than CC genotype carriers in GC tissues (P = 0.013), whereas no significant difference in miR-181a expression levels was found (P = 0.135). Luciferase assay revealed that miR-181a directly targeted MTMR3, and its suppressive effect was enhanced when the rs12537C allele was substituted by T variant, although the difference was not significant (P = 0.055). Our study suggested that rs12537 is associated with susceptibility and prognosis of GC in southern Han Chinese, and miR-181a and its target gene MTMR3 play important roles in GC.

/pdf/genetic-polymorphism-at-mir-181a-binding-site-contributes-to-4atuwo37b7.pdf

Genetic polymorphism at miR-181a binding site contributes to gastric cancer susceptibility

As a member of the tissue inhibitor of metallo-proteinases (TIMP) family, it has been reported that TIMP-3 is involved in human cancer development. However, the function of TIMP-3 in hepatocellular carcinoma (HCC) development is unclear. We aimed to determine the biological role of TIMP-3 in HCC by evaluating the effects of its methylation status and expression on HCC cell function. TIMP-3 expression in HCC tissues was visibly analyzed by immunohistochemistry. Methylation of the TIMP-3 promoter was evaluated by methylation-specific PCR. Effects of TIMP-3 on HCC cell growth, apoptosis, migration, and invasion were examined by transfecting the TIMP-3-expressing plasmid, pCMV6. TIMP-3 was expressed in non-tumorous live tissue, but silenced or downregulated in 60% of HCC cases (P<0.05). Reduced protein expression of TIMP-3 was associated with reduced tumor differentiation (P=0.003) and increased metastatic activity (P=0.005) in HCC cell lines. Promoter methylation contributed to the TIMP-3 inactivation. Overexpression of TIMP-3 in HCC cell lines suppressed cell proliferation, induced apoptosis, and inhibited migration and invasion in vitro. TIMP-3 expression is suppressed by promoter methylation in HCC. This inhibitory protein acts as a functional tumor suppressor by inhibiting HCC cell proliferation, invasion, and migration and by inducing apoptosis and cell cycle arrest at the G2/M phase.

/pdf/expression-and-inhibitory-role-of-timp-3-in-hepatocellular-50b21k1l4j.pdf

Expression and inhibitory role of TIMP-3 in hepatocellular carcinoma

NIMA-related kinase 2 (Nek2) is often upregulated in human cancer and is important in regulating the cell cycle and gene expression, and maintaining centrosomal structure and function. The present study aimed to investigate the expression pattern, clinical significance, and biological function of Nek2 in hepatocellular carcinoma (HCC). mRNA and protein levels of Nek2 were examined in HCC and corresponding normal liver tissues. The MTT and soft agar colony formation assays, and flow cytometry were employed to assess the roles of Nek2 in cell proliferation and growth. In addition, western blot analysis was performed to assess the expression of cell cycle- and proliferation-related proteins. The results revealed that Nek2 was upregulated in HCC tissues and cell lines. The clinical significance of Nek2 expression was also analyzed. Inhibiting Nek2 expression by siRNA suppressed cell proliferation, growth, and colony formation in hepatocellular carcinoma cell line HepG2 cells, induced cell cycle arrest in the G2/M phase by retarding the S-phase, and promoted apoptosis. Furthermore, Nek2 depletion downregulated β-catenin expression in HepG2 cells and diminished expression of Myc proto-oncogene protein (c-Myc), cyclins D1, B1, and E and cyclin-dependent kinase 1, whilst increasing protein levels of p27. This demonstrates that overexpression of Nek2 is associated with the malignant evolution of HCC. Targeting Nek2 may inhibit HCC cell growth and proliferation through the regulation of β-catenin by the Wnt/β-catenin pathway and therefore may be developed as a novel therapeutic strategy to treat HCC.

/pdf/nima-related-kinase-2-regulates-hepatocellular-carcinoma-4mjfx3e46v.pdf

Bo Shen

Papers

Association of Fusobacterium nucleatum infection with colorectal cancer in Chinese patients

MicroRNA-181a promotes gastric cancer by negatively regulating tumor suppressor KLF6

Genetic polymorphism at miR-181a binding site contributes to gastric cancer susceptibility

Expression and inhibitory role of TIMP-3 in hepatocellular carcinoma

NIMA-related kinase 2 regulates hepatocellular carcinoma cell growth and proliferation.