Viljoen Katie S, Dakshinamurthy Amirtha, Goldberg Paul, Blackburn Jonathan M
Institute of Infectious Disease & Molecular Medicine, Division of Medical Biochemistry, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
Surgical Gastroenterology Unit, Department of Surgery, Groote Schuur Hospital, Cape Town, South Africa.
PLoS One. 2015 Mar 9;10(3):e0119462. doi: 10.1371/journal.pone.0119462. eCollection 2015.
Various studies have presented clinical or in vitro evidence linking bacteria to colorectal cancer, but these bacteria have not previously been concurrently quantified by qPCR in a single cohort. We quantify these bacteria (Fusobacterium spp., Streptococcus gallolyticus, Enterococcus faecalis, Enterotoxigenic Bacteroides fragilis (ETBF), Enteropathogenic Escherichia coli (EPEC), and afaC- or pks-positive E. coli) in paired tumour and normal tissue samples from 55 colorectal cancer patients. We further investigate the relationship between a) the presence and b) the level of colonisation of each bacterial species with site and stage of disease, age, gender, ethnicity and MSI-status. With the exception of S. gallolyticus, we detected all bacteria profiled here in both tumour and normal samples at varying frequencies. ETBF (FDR = 0.001 and 0.002 for normal and tumour samples) and afaC-positive E. coli (FDR = 0.03, normal samples) were significantly enriched in the colon compared to the rectum. ETBF (FDR = 0.04 and 0.002 for normal and tumour samples, respectively) and Fusobacterium spp. (FDR = 0.03 tumour samples) levels were significantly higher in late stage (III/IV) colorectal cancers. Fusobacterium was by far the most common bacteria detected, occurring in 82% and 81% of paired tumour and normal samples. Fusobacterium was also the only bacterium that was significantly higher in tumour compared to normal samples (p = 6e-5). We also identified significant associations between high-level colonisation by Fusobacterium and MSI-H (FDR = 0.05), age (FDR = 0.03) or pks-positive E. coli (FDR = 0.01). Furthermore, we exclusively identified atypical EPEC in our cohort, which has not been previously reported in association with colorectal cancer. By quantifying colorectal cancer-associated bacteria across a single cohort, we uncovered inter- and intra-individual patterns of colonization not previously recognized, as well as important associations with clinicopathological features, especially in the case of Fusobacterium and ETBF.
多项研究已提供了将细菌与结直肠癌联系起来的临床或体外证据，但此前这些细菌尚未在同一队列中通过定量聚合酶链反应（qPCR）进行同时定量。我们对来自55名结直肠癌患者的配对肿瘤和正常组织样本中的这些细菌（具核梭杆菌属、解没食子酸链球菌、粪肠球菌、产肠毒素脆弱拟杆菌（ETBF）、肠致病性大肠杆菌（EPEC）以及afaC或pks阳性大肠杆菌）进行了定量。我们进一步研究了以下两者之间的关系：a）每种细菌的存在情况；b）每种细菌在疾病部位和分期、年龄、性别、种族以及微卫星不稳定性（MSI）状态方面的定植水平。除了解没食子酸链球菌外，我们在此处分析的所有细菌在肿瘤和正常样本中均有不同频率的检出。与直肠相比，ETBF（正常样本和肿瘤样本的错误发现率分别为0.001和0.002）以及afaC阳性大肠杆菌（正常样本的错误发现率为0.03）在结肠中显著富集。ETBF（正常样本和肿瘤样本的错误发现率分别为0.04和0.002）以及具核梭杆菌属（肿瘤样本的错误发现率为0.03）在晚期（III/IV期）结直肠癌中的水平显著更高。到目前为止，具核梭杆菌是检测到的最常见细菌，在82%的配对肿瘤样本和81%的配对正常样本中出现。具核梭杆菌也是唯一在肿瘤样本中显著高于正常样本的细菌（p = 6×10⁻⁵）。我们还发现具核梭杆菌的高定植水平与微卫星高度不稳定（MSI-H）（错误发现率 = 0.05）、年龄（错误发现率 = 0.03）或pks阳性大肠杆菌（错误发现率 = 0.01）之间存在显著关联。此外，我们在队列中专门鉴定出了非典型EPEC，此前尚未有其与结直肠癌相关的报道。通过对同一队列中的结直肠癌相关细菌进行定量，我们发现了以前未被认识到的个体间和个体内定植模式，以及与临床病理特征的重要关联，尤其是在具核梭杆菌和ETBF的情况下。
