Jürgen Tepel

Genome-wide association scan identifies a colorectal cancer susceptibility locus on 11q23 and replicates risk loci at 8q24 and 18q21.

In a genome-wide association study to identify loci associated with colorectal cancer (CRC) risk, we genotyped 555,510 SNPs in 1,012 early-onset Scottish CRC cases and 1,012 controls (phase 1). In phase 2, we genotyped the 15,008 highest-ranked SNPs in 2,057 Scottish cases and 2,111 controls. We then genotyped the five highest-ranked SNPs from the joint phase 1 and 2 analysis in 14,500 cases and 13,294 controls from seven populations, and identified a previously unreported association, rs3802842 on 11q23 (OR = 1.1; P = 5.8 × 10−10), showing population differences in risk. We also replicated and fine-mapped associations at 8q24 (rs7014346; OR = 1.19; P = 8.6 × 10−26) and 18q21 (rs4939827; OR = 1.2; P = 7.8 × 10−28). Risk was greater for rectal than for colon cancer for rs3802842 (P < 0.008) and rs4939827 (P < 0.009). Carrying all six possible risk alleles yielded OR = 2.6 (95% CI = 1.75–3.89) for CRC. These findings extend our understanding of the role of common genetic variation in CRC etiology.

Meta-analysis of genome-wide association data identifies four new susceptibility loci for colorectal cancer

Genome-wide association (GWA) studies have identified multiple loci at which common variants modestly influence the risk of developing colorectal cancer (CRC). To enhance power to identify additional loci with similar effect sizes, we conducted a meta-analysis of two GWA studies, comprising 13,315 individuals genotyped for 38,710 common tagging SNPs. We undertook replication testing in up to eight independent case-control series comprising 27,418 subjects. We identified four previously unreported CRC risk loci at 14q22.2 (rs4444235, BMP4; P = 8.1 × 10−10), 16q22.1 (rs9929218, CDH1; P = 1.2 × 10−8), 19q13.1 (rs10411210, RHPN2; P = 4.6 × 10−9) and 20p12.3 (rs961253; P = 2.0 × 10−10). These findings underscore the value of large sample series for discovery and follow-up of genetic variants contributing to the etiology of CRC.

A genome-wide association scan identifies the hepatic cholesterol transporter ABCG8 as a susceptibility factor for human gallstone disease

With an overall prevalence of 10–20%, gallstone disease (cholelithiasis) represents one of the most frequent and economically relevant health problems of industrialized countries. We performed an association scan of >500,000 SNPs in 280 individuals with gallstones and 360 controls. A follow-up study of the 235 most significant SNPs in 1,105 affected individuals and 873 controls replicated the disease association of SNP A-1791411 in ABCG8 (allelic P value PCCA = 4.1 × 10−9), which was subsequently attributed to coding variant rs11887534 (D19H). Additional replication was achieved in 728 German (P = 2.8 × 10−7) and 167 Chilean subjects (P = 0.02). The overall odds ratio for D19H carriership was 2.2 (95% confidence interval: 1.8–2.6, P = 1.4 × 10−14) in the full German sample. Association was stronger in subjects with cholesterol gallstones (odds ratio = 3.3), suggesting that His19 might be associated with a more efficient transport of cholesterol into the bile.

Anti–Tumor Necrosis Factor Therapy Inhibits Pancreatic Tumor Growth and Metastasis

Chronic inflammation has been implicated in the pathogenesis of many severe autoimmune disorders, as well as in diabetes, pulmonary diseases, and cancer. Inflammation accompanies most solid cancers including pancreatic ductal adenocarcinoma (PDAC), one of the most fatal cancers with surgery being the only curative therapeutic approach currently available. In the present work, we investigated the role of the major proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) in the malignancy of PDAC cells in vitro and in vivo. In vitro, TNFalpha strongly increased invasiveness of Colo357, BxPc3, and PancTuI cells and showed only moderate antiproliferative effect. TNFalpha treatment of mice bearing orthotopically growing PDAC tumors led to dramatically enhanced tumor growth and metastasis. Notably, we found that PDAC cells themselves secrete TNFalpha. Although inhibition of TNFalpha with infliximab or etanercept only marginally affected proliferation and invasiveness of PDAC cells in vitro, both reagents exerted strong antitumoral effects in vivo. In severe combined immunodeficient mice with orthotopically growing Colo357, BxPc3, or PancTuI tumors, human-specific anti-TNF antibody infliximab reduced tumor growth and metastasis by about 30% and 50%, respectively. Importantly, in a PDAC resection model performed with PancTuI cells, we found an even stronger therapeutic effect for both anti-TNF compounds. Infliximab and etanercept reduced the number of liver metastases by 69% and 42%, respectively, as well as volumes of recurrent tumors by 73% and 51%. Thus, tumor cell-derived TNFalpha plays a profound role in malignancy of PDAC, and inhibition of TNFalpha represents a promising therapeutic option particularly in adjuvant therapy after subtotal pancreatectomy.

Increased proteasome subunit protein expression and proteasome activity in colon cancer relate to an enhanced activation of nuclear factor E2-related factor 2 (Nrf2)

An elevated proteasome activity contributes to tumorigenesis, particularly by providing cancer cells with antiapoptotic protection and efficient clearance from irregular proteins. Still, the underlying mechanisms are poorly known. In this study, we report that in colon cancer patients, higher proteasome activity was detected in tumoral tissue compared with surrounding normal tissue, and also that increased levels of proteasomal subunit proteins, such as S5a/PSMD4 and α-5/PSMA5, could be detected. Colon tumors showed higher nuclear levels of nuclear factor E2-related factor 2 (Nrf2), a transcription factor supposed to be involved in the control of proteasomal subunit protein expression. The induction or overexpression of Nrf2 led to stronger S5a and α-5 expression in the human colon cancer cell lines, Colo320 and Lovo, as well as in NCM460 colonocytes along with higher proteasome activity. The small interfering RNA (siRNA)-mediated Nrf2 knockdown decreased S5a and α-5 expression and reduced proteasome activity. Additionally, Nrf2-dependent S5a and α-5 expression conferred protection from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, an effect preceded by an increased nuclear factor (NF)-κB activation and higher expression of antiapoptotic NF-κB target genes. These findings point to an important role of Nrf2 in the gain of proteasome activity, thereby contributing to colorectal carcinogenesis. Nrf2 may therefore serve as a potential target in anticancer therapy.

COGENT (COlorectal cancer GENeTics) : an international consortium to study the role of polymorphic variation on the risk of colorectal cancer

It is now recognised that a part of the inherited risk of colorectal cancer (CRC) can be explained by the co-inheritance of low-penetrance genetic variants. The accumulated experience to date in identifying these variants has served to highlight difficulties in conducting statistically and methodologically rigorous studies and follow-up analyses. The COGENT (COlorectal cancer GENeTics) consortium includes 20 research groups in Europe, Australia, the Americas, China and Japan. The overarching goal of COGENT is to identify and characterise low-penetrance susceptibility variants for CRC through association-based analyses. In this study, we review the rationale for identifying low-penetrance variants for CRC and our proposed strategy for establishing COGENT.

Genetic investigation of DNA‐repair pathway genes PMS2, MLH1, MSH2, MSH6, MUTYH, OGG1 and MTH1 in sporadic colon cancer

Mutations in DNA repair genes have previously been identified as causative factors for hereditary nonpolyposis colon cancer (HNPCC). Recent evidence also supports an association between DNA sequence variation in these genes and sporadic colorectal carcinoma (CRC). Genetic investigation of DNA repair genes PMS2, MLH1, MSH2, MSH6, MUTYH, OGG1 and MTH1, as possible susceptibility factors for sporadic CRC, was done using both a haplotype tagging and a candidate (i.e. coding) single nucleotide polymorphism (SNP) approach. Some 1,068 patients with operated CRC (median age at diagnosis: 59 years) were compared to 738 sex‐matched control individuals (median age: 67 years). Haplotype tagging SNPs, previously reported risk variants and all known coding SNPs with a minor allele frequency >0.005 were genotyped in PMS2 (N = 10), MLH1 (N = 11), MSH2 (N = 18), MSH6 (N = 15), MUTYH (N = 7), OGG1 (N = 11) and MTH1 (N = 3). No evidence for an association between CRC and any of the 7 genes was detected, neither with the tagging or coding SNPs nor in a sliding window haplotype analysis (all nominal p‐values >0.05). The previously reported risk variants D132H in MLH1 and R154H in OGG1 were not even observed in the German population. Genetic CRC risk factors so far identified in DNA repair genes seem to be rare and population‐specific. Their association with the disease could not be replicated in German CRC samples. It remains to be elucidated by more systematic, large‐scale experiments whether common variants in the same genes, but present across populations, represent risk factors for sporadic CRC.

Genetic and functional identification of the likely causative variant for cholesterol gallstone disease at the ABCG5/8 lithogenic locus†

The sterolin locus (ABCG5/ABCG8) confers susceptibility for cholesterol gallstone disease in humans. Both the responsible variant and the molecular mechanism causing an increased incidence of gallstones in these patients have as yet not been identified. Genetic mapping utilized patient samples from Germany (2,808 cases, 2,089 controls), Chile (680 cases, 442 controls), Denmark (366 cases, 766 controls), India (247 cases, 224 controls), and China (280 cases, 244 controls). Analysis of allelic imbalance in complementary DNA (cDNA) samples from human liver (n = 22) was performed using pyrosequencing. Transiently transfected HEK293 cells were used for [3H]‐cholesterol export assays, analysis of protein expression, and localization of allelic constructs. Through fine mapping in German and Chilean samples, an ∼250 kB disease‐associated interval could be defined for this locus. Lack of allelic imbalance or allelic splicing of the ABCG5 and ABCG8 transcripts in human liver limited the search to coding single nucleotide polymorphisms. Subsequent mutation detection and genotyping yielded two disease‐associated variants: ABCG5‐R50C (P = 4.94 × 10−9) and ABCG8‐D19H (P = 1.74 × 10−10) in high pairwise linkage disequilibrium (r2 = 0.95). [3H]‐cholesterol export assays of allelic constructs harboring these genetic candidate variants demonstrated increased transport activity (3.2‐fold, P = 0.003) only for the ABCG8‐19H variant, which was also superior in nested logistic regression models in German (P = 0.018), Chilean (P = 0.030), and Chinese (P = 0.040) patient samples. Conclusion: This variant thus provides a molecular basis for biliary cholesterol hypersecretion as the mechanism for cholesterol gallstone formation, thereby drawing a link between “postgenomic” and “pregenomic” pathophysiological knowledge about this common complex disorder. (HEPATOLOGY 2012)

Lymphatic spread of ductal pancreatic adenocarcinoma is independent of lymphangiogenesis.

Early lymph node metastasis is common in pancreatic ductal adenocarcinoma (PDAC). The present study has examined the relationship of lymphatic spread to lymph vessel development and the expression of lymphangiogenic cytokines in a series of well‐characterized PDACs. The hot spot method revealed the intratumoural and peritumoural lymphatic vessel density (LVD) to be slightly higher in PDACs than in the normal pancreas. The average intratumoural LVD, however, was strikingly decreased. There was no overexpression of vascular endothelial growth factor (VEGF)‐C and VEGF‐D in PDACs compared with the normal pancreas. LVD and expression of lymphangiogenic cytokines were not related to any of the biological tumour features or to patient survival. Three orthotopic nude mouse PDAC models did not reveal any increase in tumour‐associated LVD, despite a high rate of lymph node metastasis. Lymph vessel proliferation was comparable in PDAC and chronic pancreatitis, in both humans and mice. In conclusion, increased lymphangiogenic activity is not required for and does not significantly affect the lymphatic spread of PDAC. The reduced number of human and murine intratumoural lymph vessels indicates that lymphatic metastasis takes place predominantly via peritumoural lymphatic vessels. The weak expression of lymphangiogenic cytokines in neoplastic cells and lymphatic vessel proliferation in peritumoural regions and chronic pancreatitis indicate that inflammation may be the reason for the low rate of lymphangiogenesis. Copyright

Investigation of innate immunity genes CARD4, CARD8 and CARD15 as germline susceptibility factors for colorectal cancer.

BackgroundVariation in genes involved in the innate immune response may play a role in the predisposition to colorectal cancer (CRC). Several polymorphisms of the CARD15 gene (caspase activating recruitment domain, member 15) have been reported to be associated with an increased susceptibility to Crohn disease. Since the CARD15 gene product and other CARD proteins function in innate immunity, we investigated the impact of germline variation at the CARD4, CARD8 and CARD15 loci on the risk for sporadic CRC, using a large patient sample from Northern Germany.MethodsA total of 1044 patients who had been operated with sporadic colorectal carcinoma (median age at diagnosis: 59 years) were recruited and compared to 724 sex-matched, population-based control individuals (median age: 68 years). Genetic investigation was carried out following both a coding SNP and haplotype tagging approach. Subgroup analyses for N = 143 patients with early manifestation of CRC (≤50 age at diagnosis) were performed for all CARD loci and subgroup analyses for diverse age strata were carried out for CARD15 mutations R702W, G908R and L1007fs. In addition, all SNPs were tested for association with disease presentation and family history of CRC.ResultsNo significant differences were observed between the patient and control allelic or haplotypic spectra of the three genes under study for the total cohort (N = 1044 patients). None of the analysed SNPs was significantly associated with either tumour location or yielded significant association in the familial or non-familial CRC patient subgroups. However, in a patient subgroup (≤45 age at diagnosis) with early disease manifestation the mutant allele of CARD15 R702W was found to be significantly associated with disease susceptibility (9.7% in cases vs 4.6% in controls; Pallelic = 0.008, Pgenotypic = 0.0008, ORallelic = 2.22 (1.21-4.05) ORressessive = 21.9 (1.96-245.4).ConclusionVariation in the innate immunity genes CARD4, CARD8 and CARD15 is unlikely to play a major role in the susceptibility to CRC in the German population. But, we report a significant disease contribution of CARD15 for CRC patients with very early disease manifestation, mainly driven by variant R702W.