Intratumoral macrophage counts correlate with tumor progression in colorectal cancer

Background

The role of intratumoral tumor‐associated macrophages (TAMs) in colorectal cancer (CRC) is not clear. We aim to examine the relationships of TAMs and the clinicopathologic features of CRC and the expression of matrix metalloproteinases (MMP)‐2 and MMP‐9.

Methods

Immunohistochemical staining of CD68, MMP‐2, and MMP‐9 was determined in tissue samples from CRC patients. To test the biological effect of macrophages on tumor cells, cancer cells were cocultured with macrophages and function change of cancer cells were examined.

Results

Intratumoral TAM count correlated with depth of invasion (P = 0.048), lymph node metastasis (P < 0.0001), and staging (P < 0.0001) of CRC. MMP‐2 and MMP‐9 expression was significantly associated with lymph node metastasis and staging. A significant association between intratumoral TAM counts and MMP‐2 (P < 0.0001) and MMP‐9 (P < 0.0001) expression was noted. When cocultured with macrophages, cancer cells increased their invasiveness and migration and elevated MMP‐2 and MMP‐9 secretion.

Conclusions

Intratumoral TAMs cause cancer cells to have a more aggressive behavior, and this may be due to an upregulation of tumor cell‐derived MMP‐2 and MMP‐9. Examination of intratumoral TAMs can serve as a progressive marker for CRC patients. J. Surg. Oncol. 2010;102:242–248. © 2010 Wiley‐Liss, Inc.     

Polymethoxyflavones prevent benzo[a]pyrene/dextran sodium sulfate‐induced colorectal carcinogenesis through modulating xenobiotic metabolism and ameliorate autophagic defect in ICR mice

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental carcinogenic pollutants and they have become an important issue in food contamination. Dietary intake of PAHs has been recognized as a major route of human exposure. However, the mechanisms behind dietary PAH‐induced colorectal cancer (CRC) remain unclear. Several studies have shown that polymethoxyflavones (PMFs) are effective in preventing carcinogen‐induced CRC or colitis. In this study, we investigated the preventive effect of PMFs on benzo[a]pyrene/dextran sulfate sodium (BaP/DSS)‐induced colorectal tumorigenesis in ICR mice. We found that PMFs significantly prevented BaP/DSS‐induced colorectal tumor formation. BaP mutagenic metabolite and DNA adducts were found to be reduced in colonic tissue in the PMFs‐treated groups through the modulation of BaP metabolism. At the molecular level, the results of RNA‐sequencing indicated that PMFs ameliorated BaP/DSS‐induced abnormal molecular mechanism change including activated inflammation, downregulated anti‐oxidation targets, and induced metastasis genes. The autophagic defect caused by BaP/DSS‐induced tumorigenesis was improved by pretreatment with PMFs. We found BaP/DSS‐induced CRC may be a Wnt/β‐catenin independent process. Additionally, consumption of PMFs extracts also altered the composition of gut microbiota and made it similar to that in the control group by increasing butyrate‐producing probiotics and decreasing CRC‐related bacteria. BaP in combination with DSS significantly induced colorectal tumorigenesis through induced DNA adduct formation, abnormal gene expression, and imbalanced gut microbiota composition. PMFs were a powerful preventive agent that suppressed BaP/DSS‐induced CRC via modulating multiple pathways as well as ameliorating autophagic defect. These results demonstrated for the first time the chemopreventive efficacy and comprehensive mechanisms of dietary PMFs for preventing BaP/DSS‐induced colorectal carcinogenesis.     

The association between −1304T>G polymorphism in the promoter of MKK4 gene and the risk of sporadic colorectal cancer in southern Chinese population

MKK4 (mitogen‐activated protein kinase kinase 4, NM_003010.2), which belongs to the mitogen‐activated protein kinase pathways, possesses functions in tumorigenesis. We hypothesized the genetic variants in MKK4 gene may alter its functions and thus cancer risk. In current hospital‐based case‐control study of 706 patients with sporadic colorectal cancer (CRC) and 723 sex‐age–frequency‐matched control subjects in a southern Chinese population, we genotyped two polymorphisms of MKK4 promoter (i.e., ?1304T>G, rs3826392 and ?1044A>T, rs3809728) and assessed their associations with the risk of sporadic CRC. Compared with ?1304TT genotypes, ?1304TG had a significantly decreased risk of CRC (adjusted odds ratios [OR] = 0.56; 95% CI = 0.44–0.72; p = 3.53 × 10^?6), the ?1304GG carriers had a further decreased risk of CRC (OR = 0.40; 95% CI = 0.23–0.70; p = 1.32 × 10^?3), and there was a significant trend for an allele dose effect on risk of CRC (p_trend = 2.64 × 10^?7). The decreased risk associated with ?1304G variant genotypes (i.e., TG+GG) was more pronounced in the subjects older than 60 years (adjusted OR = 0.41; 95% CI = 0.29–0.57; p = 2.25 × 10^?7), in ever drinkers (adjusted OR = 0.41; 95% CI = 0.28–0.59; p = 2.42 × 10^?6). The age and alcohol drinking status interacted with ?1304G variant genotypes on reducing cancer risk (p values for interaction were 0.015 and 0.043, respectively). Western blotting analysis showed that the levels of Mkk4 protein in sporadic CRC neoplastic tissues were significantly higher in the carriers of ?1304G variant genotypes than that in those with ?1304TT genotypes. However, no significant association was observed between ?1044A>T polymorphism and risk of CRC. To the best of our knowledge, this is the first study of genetic variants in MKK4 and cancer susceptibility. Larger studies are needed to validate our findings. © 2009 UICC     

P21‐activated kinase 5 is overexpressed during colorectal cancer progression and regulates colorectal carcinoma cell adhesion and migration

P21‐activated kinase 5 (PAK5) is the recently identified member of the group B p21‐activated kinase (PAK) family which are effectors of the small GTPase Cdc42 and Rac1, known to regulate cell motility and activate cell‐survival signaling pathways. However, overexpression of PAK5 has not been associated with any cancers so far. Interestingly, we found that PAK5 was overexpressed in a variety of colorectal carcinoma (CRC) cell lines in a Western‐blotting examination. Therefore, in this study, we aim to examine the PAK5 expression during CRC progression and to answer if PAK5 is involved in malignant progression of CRC. By immunohistochemistry, our results showed that PAK5 expression was increased with CRC progression through the adenoma to carcinoma sequence, with the most significant increases in invasive and metastatic CRCs (p < 0.0001). Furthermore, increased PAK5 expression was also found with the development of CRC from lower Duke's grades to higher ones (p < 0.01). Moreover, PAK5 was also increased from well to poorly differentiated CRCs (p < 0.01). Using gain and loss of function experiments, we found that PAK5 reduced CRC cell adhesion but promoted their migration on collagen type I. Taken together, our study demonstrated that PAK5 expression increased significantly with malignant progression of CRC and that PAK5 might promote CRC metastasis by regulating CRC cell adhesion and migration. © 2009 UICC     

Identification of candidate genes carrying polymorphisms associated with the risk of colorectal cancer by analyzing the colorectal mutome and microRNAome

BACKGROUND:

The presence of single‐nucleotide polymorphisms (SNPs) within the 3′‐untranslated regions of genes could affect the binding between a microRNA (miRNA) and its target, with consequences on gene expression regulation. Considering the important role of miRNAs in carcinogenesis, it is hypothesized here that these SNPs could also affect the individual risk of colorectal cancer (CRC).

METHODS:

To test this hypothesis, a list was developed of 140 somatically mutated genes deduced from previous works on the mutome of the CRC. A further selection was conducted of SNPs within target sites for miRNAs that are expressed only in the colorectum (the colorectal microRNAome) and having adequate population frequencies. This yielded 12 SNPs that were genotyped in a case‐control association study on 717 colorectal cases and 1171 controls from the Czech Republic.

RESULTS:

Statistically significant associations were found between the risk of CRC and the variant alleles of KIAA0182 (rs709805) (odds ratio = 1.57; 95% confidence interval = 1.06‐2.78, for the variant homozygotes) and NUP210 genes (rs354476) (odds ratio = 1.36; 95% confidence interval = 1.02‐1.82, for the variant homozygotes).

CONCLUSIONS:

The results support the study hypothesis and highlight the importance of SNPs within miRNA‐dependent regulatory regions. Further studies on the role exerted by NUP210 and KIAA0182 in colorectal carcinogenesis are warranted. Cancer 2012. © 2012 American Cancer Society.     

Contribution of rare germline copy number variations and common susceptibility loci in Lynch syndrome patients negative for mutations in the mismatch repair genes

In colorectal carcinoma (CRC), 35% of cases are known to have a hereditary component, while a lower proportion (～5%) can be explained by known genetic factors. In this study, copy number variations (CNVs) were evaluated in 45 unrelated patients with clinical hypothesis of Lynch syndrome (Amsterdam or Bethesda criteria); negative for MLH1, MSH2, MSH6, PMS2, CHEK2*1100delC and TP53 pathogenic mutations; aiming to reveal new predisposing genes. Analyses with two different microarray platforms (Agilent 180K and Affymetrix CytoScan HD) revealed 35 rare CNVs covering 67 known genes in 22 patients. Gains (GALNT6 and GALNT11) and losses (SEMA3C) involving the same gene families related to CRC susceptibility were found among the rare CNVs. Segregation analysis performed on four relatives from one family suggested the involvement of GALNT11 and KMT2C in those at risk of developing CRC. Notably, in silico molecular analysis revealed that 61% (41/67) of the genes covered by rare CNVs were associated with cancer, mainly colorectal (17 genes). Ten common SNPs, previously associated with CRC, were genotyped in 39 index patients and 100 sporadic CRC cases. Although no significant, an increased number of risk alleles was detected in the index cases compared with the sporadic CRC patients. None of the SNPs were covered by CNVs, suggesting an independent effect of each alteration in cancer susceptibility. In conclusion, rare germline CNVs and common SNPs may contribute to an increased risk for hereditary CRC in patients with mismatch repair proficiency.     

Single nucleotide polymorphisms in the hypoxia‐inducible factor‐1 gene and colorectal cancer risk

With an incidence of about 300 000 new cases colorectal cancer (CRC) is the second leading cause of cancer‐related death in Europe and the United States. Environmental and genetic factors influence CRC risk. Hypoxia‐inducible factor‐1 (HIF‐1), a heterodimeric protein composed of two subunits, HIF‐1 alpha and HIF‐1 beta, plays a critical role in oxygen homeostasis and is involved in angiogenesis and cell proliferation. The gene for the HIF‐1 alpha subunit (HIF1A) carries two common missense mutations—P582S (rs11549465) and A588T (rs11549467)—which both have been related to increased trans‐activation capacity of HIF1A. In our case–control study we investigated the association between these polymorphisms and CRC risk. We investigated 381 patients with histologically confirmed CRC and 2156 control subjects. HIF1A genotypes were determined by exonuclease (TaqMan) assays. For determination of microvessel density (MVD) tumor sections were stained using a mouse monoclonal antibody recognizing the pan‐endothelial marker CD31. In a multivariate logistic regression analysis including age and sex neither the HIF1A 582S allele (Odds ratio: 1.204; 95% confidence interval 0.911–1.592; P = 0.193) nor the 588T allele was significantly associated with CRC (Odds ratio: 0.851; 95% confidence interval 0.444–1.631; P = 0.626). However, in an exploratory analysis, the HIF1A 588T allele was associated with tumor localization (P = 0.016) and tumor size (P = 0.003). MVD was similar in tumors of patients carrying HIF1A 588T allele and patients without this rare allele. We conclude that functional polymorphisms in the HIF1A gene do not modify CRC risk but maybe associated with clinic‐pathological features of the disease. © 2010 Wiley‐Liss, Inc.     

ANKLE1 N6-Methyladenosine-related variant is associated with colorectal cancer risk by maintaining the genomic stability

The N⁶-Methyladenosine (m⁶A) modification plays an important role in many biological processes, especially tumor development. However, little is still known about how it affects colorectal cancer (CRC) carcinogenesis. Here, we first systematically investigate the association of variants related to m⁶A modification with the CRC risk in 1,062 CRC cases and 2,184 controls by using our exome-wide association data and followed by two replication sets including 7,341 CRC cases and 7,902 controls. The variant rs8100241 located in ANKLE1 was significantly associated with CRC risk (odds ratio = 0.88, 95% confidence interval = 0.84–0.92, p = 4.85 × 10⁻⁸) in 8,403 cases and 10,086 controls. This variant was previously identified to be associated with the susceptibility of breast cancer with BRCA1 mutation triple negative breast cancer. Further functional analysis indicated that overexpression of the rs8100241[A] allele significantly increased the ANKLE1 m⁶A level and facilitated the ANKLE1 protein expression compared to that of rs8100241[G] allele. We further found the ANKLE1 m⁶A modification was catalyzed by the “writer” complex (METTL3, METTL14, or WTAP) and recognized by the “reader” YTHDF1. Mechanistically, we found that the ANKLE1 functions as a potential tumor suppressor that inhibits cell proliferation and facilitates the genomic stability. An elevated frequency of micronucleated cells, increased cell proliferation, and colony formation ability were observed when ANKLE1 knockdown. Our study illustrated that the germline missense variant can increase CRC risk by influencing ANKLE1 m⁶A level, highlighting a clinical potential of variants-associated m⁶A modification as a risk marker for CRC prevention.     

Expression of the MAP kinase phosphatase DUSP4 is associated with microsatellite instability in colorectal cancer (CRC) and causes increased cell proliferation

DUSP4 (MKP‐2), a member of the mitogen‐activated protein kinase phosphatase (MKP) family and potential tumor suppressor, negatively regulates the MAPKs (mitogen‐activated protein kinases) ERK, p38 and JNK. MAPKs play a crucial role in cancer development and progression. Previously, using microarray analyses we found a conspicuously frequent overexpression of DUSP4 in colorectal cancer (CRC) with high frequent microsatellite instability (MSI‐H) compared to microsatellite stable (MSS) CRC. Here we studied DUSP4 expression on mRNA level in 38 CRC (19 MSI‐H and 19 MSS) compared to matched normal tissue as well as in CRC cell lines by RT‐qPCR. DUSP4 was overexpressed in all 19 MSI‐H tumors and in 14 MSS tumors. Median expression levels in MSI‐H tumors were significantly higher than in MSS‐tumors (p < 0.001). Consistently, MSI‐H CRC cell lines showed 6.8‐fold higher DUSP4 mRNA levels than MSS cell lines. DUSP4 expression was not regulated by promoter methylation since no methylation was found by quantitative methylation analysis of DUSP4 promoter in CRC cell lines neither in tumor samples. Furthermore, no DUSP4 mutation was found on genomic DNA level in four CRC cell lines. DUSP4 overexpression in CRC cell lines through DUSP4 transfection caused upregulated expression of MAPK targets CDC25A, CCND1, EGR1, FOS, MYC and CDKN1A in HCT116 as well as downregulation of mismatch repair gene MSH2 in SW480. Furthermore, DUSP4 overexpression led to increased proliferation in CRC cell lines. Our findings suggest that DUSP4 acts as an important regulator of cell growth within the MAPK pathway and causes enhanced cell growth in MSI‐H CRC.     

Potent antitumor activity of cabozantinib,a c‐MET and VEGFR2 inhibitor,in a colorectal cancer patient‐derived tumor explant model

Antiangiogenic therapy is commonly used for the treatment of colorectal cancer (CRC). Although patients derive some clinical benefit, treatment resistance inevitably occurs. The MET signaling pathway has been proposed to be a major contributor of resistance to antiangiogenic therapy. MET is upregulated in response to vascular endothelial growth factor pathway inhibition and plays an essential role in tumorigenesis and progression of tumors. In this study, we set out to determine the efficacy of cabozantinib in a preclinical CRC patient‐derived tumor xenograft model. We demonstrate potent inhibitory effects on tumor growth in 80% of tumors treated. The greatest antitumor effects were observed in tumors that possess a mutation in the PIK3CA gene. The underlying antitumor mechanisms of cabozantinib consisted of inhibition of angiogenesis and Akt activation and significantly decreased expression of genes involved in the PI3K pathway. These findings support further evaluation of cabozantinib in patients with CRC. PIK3CA mutation as a predictive biomarker of sensitivity is intriguing and warrants further elucidation. A clinical trial of cabozantinib in refractory metastatic CRC is being activated.     

Possible involvement of Wnt11 in colorectal cancer progression

Our previous report revealed that the expression of Frizzled‐7 (FZD7) in colorectal cancer (CRC) and its possible role in CRC progression. In this study we measured the expression levels of candidate FZD7 ligands, Wnt3 and Wnt11 in colon cancer cell lines (n = 7) and primary CRC tissues (n = 133) by quantitative RT‐PCR. We also examined the functional effects of Wnt11 with the use of Wnt11 transfectants of colon cancer HCT‐116 cells. Wnt11 transfectants showed the increased proliferation and migration/invasion activities compared to mock cells. Western blot analysis of transfectants revealed that phosphorylation of JNK and c‐jun was increased after Wnt11 transfection. Wnt11 mRNA expression was significantly higher in the stage I, II, III, or IV tumor tissues than in non‐tumor tissues (overall P < 0.003), while there was no significant difference in Wnt3 mRNA expression between tumor and non‐tumor tissues. In addition, Wnt11 mRNA expression was significantly higher in patients with recurrence or death after surgery than in those with no recurrence (disease free) after surgery (P = 0.018). We also compared the expression levels of Wnt11 mRNA with those of FZD7 mRNA in the same CRC samples. Wnt11 mRNA expression was significantly higher in patients with higher FZD7 mRNA levels than in those with lower FZD7 mRNA levels (P = 0.0005). The expression levels of Wnt11 mRNA were correlated with those of FZD7 mRNA (P < 0.0001). These data suggest that Wnt11 may play an important role in CRC progression. © 2011 Wiley Periodicals, Inc.     

Emergency treatment of complicated colorectal cancer in the elderly. Should the surgical procedure be influenced by the factor ‘age’?

KESISOGLOU I., PLIAKOS I., SAPALIDIS K., DELIGIANNIDIS N. & PAPAVRAMIDIS S. (2009) European Journal of Cancer Care
Emergency treatment of complicated colorectal cancer in the elderly. Should the surgical procedure be influenced by the factor ‘age’? The complication rate in patients affected by colorectal cancer (CRC) is high and the prognosis especially in the elderly patients is poor. The aim of this retrospective study is to compare the complicated CRC outcome between elderly patients and a group of patients younger than 70 years old, treated at the same time period. Between 1997 and 2007, 24 patients older than 70 years old with CRC (Group A), in an emergency situation, were operated on by the same team of surgeons. During the same time period, 20 patients, aged less than 70 years (Group B), with similar clinical and surgical findings, were operated on. All patients had undergone emergency procedures for occlusion, perforation and haemorrhage. We compared both groups in terms of preoperative health status, morbidity and mortality rates. According to ASA classification, Group A was considered of greater intraoperative danger (P= 0.01). Despite the fact that there was no statistically significant difference between the two groups, patients aged >70 years presented higher morbidity and mortality rates. This fact is probably due to their overall health status. The surgical approach of patients with complicated CRC should not be influenced by the patient's age.     

MicroRNA-29a promotes colorectal cancer metastasis by regulating matrix metalloproteinase 2 and E-cadherin via KLF4

Background:

Growing evidence suggests that miR-29a has an important role in regulating tumourigenesis and development of various types of cancer. However, the role and the underlying mechanism of miR-29a in colorectal cancer (CRC) remain largely unknown.

Methods:

MiR-29a targeted gene was identified by the luciferase assay and western blot. MiR-29a function was analysed by invasion assays and the orthotopic transplantation mouse model. The miR-29a pathway was assayed by real-time PCR, western blot and chip analysis.

Results:

KLF4 was identified as a direct target gene of miR-29a. MiR-29a promoted CRC cell invasion, which was blocked by re-expression of KLF4. In addition, MMP2 was identified as a novel direct target of KLF4. Both miR-29a overexpression and KLF4 knockdown promoted MMP2 expression but inhibited E-cadherin expression. Furthermore, clinical data indicated that both miR-29a high expression and KLF4 mRNA low expression were associated with metastasis and poor prognosis in CRC patients, and KLF4 protein expression was inversely correlated with MMP2 but positively correlated with E-cad protein expression.

Conclusion:

Increased expression of miR-29a promoted CRC metastasis by regulating MMP2/E-cad through direct targeting KLF4, which highlights the potential of the miR-29a inhibitor as a novel agent against CRC metastasis.     

Meta-analysis of 16 studies of the association of alcohol with colorectal cancer

Alcohol consumption is an established risk factor for colorectal cancer (CRC). However, while studies have consistently reported elevated risk of CRC among heavy drinkers, associations at moderate levels of alcohol consumption are less clear. We conducted a combined analysis of 16 studies of CRC to examine the shape of the alcohol–CRC association, investigate potential effect modifiers of the association, and examine differential effects of alcohol consumption by cancer anatomic site and stage. We collected information on alcohol consumption for 14,276 CRC cases and 15,802 controls from 5 case-control and 11 nested case-control studies of CRC. We compared adjusted logistic regression models with linear and restricted cubic splines to select a model that best fit the association between alcohol consumption and CRC. Study-specific results were pooled using fixed-effects meta-analysis. Compared to non-/occasional drinking (≤1 g/day), light/moderate drinking (up to 2 drinks/day) was associated with a decreased risk of CRC (odds ratio [OR]: 0.92, 95% confidence interval [CI]: 0.88–0.98, p = 0.005), heavy drinking (2–3 drinks/day) was not significantly associated with CRC risk (OR: 1.11, 95% CI: 0.99–1.24, p = 0.08) and very heavy drinking (more than 3 drinks/day) was associated with a significant increased risk (OR: 1.25, 95% CI: 1.11–1.40, p < 0.001). We observed no evidence of interactions with lifestyle risk factors or of differences by cancer site or stage. These results provide further evidence that there is a J-shaped association between alcohol consumption and CRC risk. This overall pattern was not significantly modified by other CRC risk factors and there was no effect heterogeneity by tumor site or stage.     

The CHEK2 I157T variant and colorectal cancer susceptibility: a systematic review and meta-analysis

Background: The cell cycle checkpoint kinase 2 (CHEK2) gene I157T variant may be associated with anincreased risk of colorectal cancer, but it is unclear whether the evidence is sufficient to recommend testing forthe mutation in clinical practice. Materials and Methods: We systematically searched PubMed, EMBASES,Elsevier and Springer for relevant articles before Apr 2012. Summary odds ratios (ORs) and 95% confidenceintervals (95% CIs) were calculated using a fixed-effects or random-effects models with Review Manager 5.0software. Results: A total of seven studies including 4,029 cases and 13,844 controls based on the search criteriawere included for analysis. A significant association of the CHEK2 I157T C variant with unselected CRC wasfound (OR = 1.61, 95% CI = 1.40–1.87, P < 0.001). We also found a significant association with sporadic CRC(OR = 1.48, 95% CI = 1.23–1.77, P < 0.001) and separately with familial CRC (OR = 1.97, 95% CI = 1.41–2.74, P< 0.001). Conclusion: This meta-analysis demonstrates that the CHEK2 I157T variant may be another importantCRC-predisposing gene, which increases CRC risk, especially in familial CRC.     

结直肠癌组织中KIAA1522的表达 及临床意义

目的：检测KIAA1522蛋白在结直肠癌中的表达变化并评价其临床意义。方法：应用组织芯片-免疫组织化学染色技术,检测96例结直肠癌组织及其配对癌旁正常组织中KIAA1522蛋白的表达情况,并对其阳性表达率与结直肠癌临床病理指标及患者预后的关系进行统计学分析。结果：KIAA1522蛋白在癌旁正常结直肠上皮细胞中主要定位于细胞浆,阳性表达率为12.5%（12/96）,而在结直肠癌组织中KIAA1522蛋白阳性表达率为81.3%（78/96）,两者间差异显著（P < 0.05）。Kaplan-Meier生存分析结果显示,KIAA1522蛋白阳性表达与结直肠癌患者术后3年无瘤生存期短显著正相关（P=0.017,Log-rank检验）。多因素Cox回归分析结果表明,KIAA1522蛋白阳性表达是结直肠癌患者预后不良的独立预测因素（P=0.020）。卡方检验的分析结果显示,KIAA1522蛋白阳性表达与肿瘤的远处转移正相关（P=0.012,Fisher精确检验）。结论：KIAA1522在结直肠癌组织中的阳性表达与肿瘤的远处转移及患者术后生存期短显著相关,可能作为预测结直肠癌患者预后及转移的潜在分子标志。     

Prospective study of oral microbiome and colorectal cancer risk in low-income and African American populations

Oral microbiome may play an important role in cancer pathogenesis. However, no study has prospectively investigated the association of the oral microbiome with subsequent risk of developing colorectal cancer (CRC). We conducted a nested case–control study including 231 incident CRC cases and 462 controls within the Southern Community Cohort Study with 75% of the subjects being African-Americans. The controls were individually matched to cases based on age, ethnic group, smoking, season-of-study enrollment and recruitment method. Oral microbiota were assessed using 16S rRNA gene sequencing in pre-diagnostic mouth rinse samples. Multiple bacterial taxa showed an association with CRC risk at p <0.05. Oral pathogens Treponema denticola and Prevotella intermedia were associated with an increased risk of CRC, with odds ratios (ORs) and 95% confidence intervals (CIs) of 1.76(1.19–2.60) and 1.55(1.08–2.22), respectively, for the individuals carrying these bacteria compared to non-carriers. In the phylum Actinobacteria, Bifidobacteriaceae was more abundant among CRC patients than among controls. In the phylum Bacteroidetes, Prevotella denticola and Prevotella sp. oral taxon 300 were associated with an increased CRC risk, while Prevotella melaninogenica was associated with a decreased risk of CRC. In the phylum Firmicutes, Carnobacteriaceae, Streptococcaceae, Erysipelotrichaceae, Streptococcus, Solobacterium, Streptococcus sp. oral taxon 058 and Solobacterium moorei showed associations with a decreased risk of CRC. Most of these associations were observed among both African- and European-Americans. Most of the associations were not significant after Bonferroni correction for multiple testing, which may be conservative. Our study suggests that the oral microbiome may play a significant role in CRC etiology.     

Novel colon cancer susceptibility variants identified from a genome‐wide association study in African Americans

Genome‐wide association studies (GWAS) in ethnic/racial minority populations can help to fine‐map previously identified risk regions or discover new risk loci because of the genetic diversity in these populations. We conducted a GWAS of colorectal cancer (CRC) in 6,597 African Americans (1,894 cases and 4,703 controls) (Stage 1) and followed up the most promising markers in a replication set of 2,041 participants of African descent (891 cases and 1,150 controls) (Stage 2). We identified a novel variant, rs56848936 in the gene SYMPK at 19q13.3, associated with colon cancer risk (odds ratio 0.61 for the risk allele G, p = 2.4 × 10^?8). The frequency of the G allele was 0.06 in African Americans, compared to <0.01 in Europeans, Asians and Amerindians in the 1000 Genomes project. In addition, a variant previously identified through fine‐mapping in this GWAS in the region 19q13.1, rs7252505, was confirmed to be more strongly associated with CRC in the African American replication set than the variant originally reported in Europeans (rs10411210). The association between rs7252505 and CRC was of borderline significance (p = 0.05) in a Hispanic population GWAS with 1,611 CRC cases and 4,330 controls. With the three datasets combined, the odds ratio was 0.84 for the risk allele A (95% confidence interval 0.79–0.89, p = 3.7 × 10^?8). This study further highlights the importance of conducting GWAS studies in diverse ancestry populations.