Katharina Balschun

Hepatitis B virus-induced lipid alterations contribute to natural killer T cell-dependent protective immunity

In most adult humans, hepatitis B is a self-limiting disease leading to life-long protective immunity, which is the consequence of a robust adaptive immune response occurring weeks after hepatitis B virus (HBV) infection. Notably, HBV-specific T cells can be detected shortly after infection, but the mechanisms underlying this early immune priming and its consequences for subsequent control of viral replication are poorly understood. Using primary human and mouse hepatocytes and mouse models of transgenic and adenoviral HBV expression, we show that HBV-expressing hepatocytes produce endoplasmic reticulum (ER)-associated endogenous antigenic lipids including lysophospholipids that are generated by HBV-induced secretory phospholipases and that lead to activation of natural killer T (NKT) cells. The absence of NKT cells or CD1d or a defect in ER-associated transfer of lipids onto CD1d results in diminished HBV-specific T and B cell responses and delayed viral control in mice. NKT cells may therefore contribute to control of HBV infection through sensing of HBV-induced modified self-lipids.

Distinct DNA methylation patterns in cirrhotic liver and hepatocellular carcinoma

Abberrant DNA methylation is one of the hallmarks of cancerogenesis. Our study aims to delineate differential DNA methylation in cirrhosis and hepatic cancerogenesis. Patterns of methylation of 27,578 individual CpG loci in 12 hepatocellular carcinomas (HCCs), 15 cirrhotic controls and 12 normal liver samples were investigated using an array‐based technology. A supervised principal component analysis (PCA) revealed 167 hypomethylated loci and 100 hypermethylated loci in cirrhosis and HCC as compared to normal controls. Thus, these loci show a “cirrhotic” methylation pattern that is maintained in HCC. In pairwise supervised PCAs between normal liver, cirrhosis and HCC, eight loci were significantly changed in all analyses differentiating the three groups (p < 0.0001). Of these, five loci showed highest methylation levels in HCC and lowest in control tissue (LOC55908, CELSR1, CRMP1, GNRH2, ALOX12 and ANGPTL7), whereas two loci showed the opposite direction of change (SPRR3 and TNFSF15). Genes hypermethylated between normal liver to cirrhosis, which maintain this methylation pattern during the development of HCC, are depleted for CpG islands, high CpG content promoters and polycomb repressive complex 2 (PRC2) targets in embryonic stem cells. In contrast, genes selectively hypermethylated in HCC as compared to nonmalignant samples showed an enrichment of CpG islands, high CpG content promoters and PRC2 target genes (p < 0.0001). Cirrhosis and HCC show distinct patterns of differential methylation with regards to promoter structure, PRC2 targets and CpG islands.

HER2/neu testing in primary colorectal carcinoma.

Background:Anti-HER2/neu therapy is well-established in breast and gastric carcinoma. The increased understanding of this pathway led to the identification of new promising drugs in addition to trastuzumab, offering further perspectives. The role of HER2/neu in colorectal carcinoma is controversially discussed, as discrepant data has been reported.Methods:Here, we retrospectively assessed the prevalence of HER2/neu positivity in a large series of colorectal carcinoma, testing HER2/neu status according to current recommendations. We correlated the results to clinico-pathological data and patient survival.Results:Overall, in 1645 primary colorectal carcinoma cases, 1.6% of the cases were HER2/neu positive. HER2/neu positivity significantly correlated with higher UICC stages (P=0.017) and lymph node metastases (P=0.029). In the subgroup of sigmoideal and rectal carcinomas, positive HER2/neu status was associated with T-category (P=0.041) and higher UICC stages (P=0.022). Although statistically not significant, HER2/neu-positive colorectal carcinomas displayed a tendency to poorer overall survival.Conclusions:These results illustrate the importance of testing HER2/neu by approved diagnostic techniques and scoring systems. We assume that although the prevalence of HER2/neu positivity in colorectal carcinoma is low, HER2/neu testing in advanced, nodal-positive colorectal carcinoma is reasonable, offering a potential target in high risk colorectal carcinoma.

KRAS, NRAS, PIK3CA Exon 20, and BRAF Genotypes in Synchronous and Metachronous Primary Colorectal Cancers: Diagnostic and Therapeutic Implications

Targeted therapy of advanced colorectal carcinoma (CRC) necessitates KRAS genotyping. Because we were interested in diagnostic and therapeutic consequences, we studied the KRAS, NRAS, PIK3CA exon 20, and BRAF genotypes in synchronous and metachronous primary CRCs; in addition, we studied their available metastases. We studied 21 patients with 43 synchronous and 2 metachronous adenocarcinomas of the colorectum (n = 20) and stomach (n = 1). Five patients had liver metastases and one had a distant lymph node metastasis. Genomic DNA was extracted from microdissected tumor tissue. The DNA was analyzed by Sanger sequencing and pyrosequencing. Fifty-seven different neoplastic lesions were genotyped, showing 18 (31.6%) KRAS, 2 (3.5%) NRAS, and 7 (12.3%) BRAF mutations, distributed among 10 (47.6%), 1 (4.8%), and 5 (23.8%) of the patients. An identical genotype of all synchronous primary CRCs was found only in 7 (35%) of the patients; the remainder had dissimilar genotypes in various combinations. Interestingly, a single patient had an unknown KRAS genotype (c.37_39dupGGC). Six patients with 13 primary carcinomas had distant metastases. In three of these patients, the metastasis shared the genotype only with one of the primary tumors, because the other primary tumors had another genotype. Synchronous and metachronous primary CRCs of the same patient have variable KRAS, NRAS, and BRAF genotypes. When metastases occur in these patients, the genotype has diagnostic and therapeutic implications and should be determined from the simultaneous or metachronous distant metastases.

Prognostic and putative predictive biomarkers of gastric cancer for personalized medicine.

We investigated various phenotypic and genotypic biomarkers of gastric cancer (GC) testing the following hypotheses: are these biomarkers suitable for the identification of GC subtypes, are they of prognostic significance, and should any of these biomarkers be considered to tailor patient treatment in the future. The study cohort consisted of 482 patients. pTNM-stage was based on surgical pathologic examination. The Laurén and mucin phenotype was assessed. Helicobacter pylori and Epstein-Barr virus infections were documented. The following biomarkers were determined: BRAF, KRAS, NRAS, and PIK3CA genotype, microsatellite instability, mucin 1, mucin 2, mucin 5, and mucin 6, CD10, E-cadherin, &bgr;-catenin, and lysozyme. The histologic phenotype correlated with 10/13 (77%) clinicopathologic patient characteristics and 6/13 (46%) immunohistochemical/molecular biological biomarkers. Inversely, immunohistochemical biomarkers (mucin phenotype, E-cadherin, &bgr;-catenin, and lysozyme) were unsuitable for subclassification of GC. It showed too much overlap between the different subtypes. Among the genotypes, only microsatellite instability correlated with tumor type being more prevalent in intestinal and unclassified GCs. Patient survival correlated significantly with 8 (62%) clinicopathologic and 5 (36%) immunohistochemical/molecular biomarkers. Interestingly, in proximal GCs, KRAS mutation was associated with worse prognosis, as was persistent H. pylori infection in unclassified GCs. Mucin 2 (all patients, proximal GCs) and PIK3CA (exon 20; intestinal type GC) prognosticated independently patient survival. The biomarkers examined herein are unsuitable to aid histologic classification of GC. However, several of them show a correlation with either phenotype and/or prognosis and may be considered to tailor patient treatment in the future, such as KRAS, PIK3CA, MSI, and H. pylori status.

Endoscopic ultrasound of the colon for the differentiation of Crohn's disease and ulcerative colitis in comparison with healthy controls

Diagnosis of inflammatory bowel disease (IBD) is based on clinical presentation, colonoscopy and histology. Differentiation of Crohns disease (CD) and ulcerative colitis (UC) can be difficult in some patients. Endoscopic ultrasound (EUS) provides high resolution images of the gastrointestinal wall (GI) and may be an alternative to differentiate CD/UC.

LGR4 and LGR6 are differentially expressed and of putative tumor biological significance in gastric carcinoma

Gastric cancer (GC) is one of the most common causes of cancer-related deaths worldwide. We investigated the differential expression and putative tumor biological significance of five G-protein-coupled receptors (GPCRs) in GC, i.e., LGR4, LGR6, GPR34, GPR160, and GPR171. Based on our previous microarray analyses, we identified five candidate genes in human GC samples. Real-time RT-PCR was carried out to validate their expression in malignant and non-malignant tissues on an independent collective comprising 32 GC patients with and without lymph node metastases. Selected protein targets LGR4 and LGR6 were further validated on paraffin-embedded sections of ten intestinal and ten poorly cohesive (diffuse)-type GCs and their corresponding non-malignant tissue using immunohistochemistry. Additionally, the putative tumor biological significance of LGR4 and LGR6 was studied using tissue microarrays obtained from a cohort of 481 GC patients. On transcriptional level, GPR34, GPR160, and GPR171 were not differentially expressed in GC compared with non-neoplastic mucosa. LGR4 and LGR6 were up-regulated on transcriptional (real-time RT-PCR) and translational (immunohistochemistry) levels in GC. Furthermore, in tissue microarray analysis, LGR6 expression was significantly associated with local tumor growth (T-category; p = 0.04) and correlated with patient survival. LGR4 expression was significantly correlated with nodal spread (N-category; p = 0.025). Our systematic analysis indicates that LGR4 and LGR6 may play a role in GC biology. Future studies will have to demonstrate whether these are also putative diagnostic, prognostic, and/or therapeutic targets for GC.

Detection of KRAS and BRAF mutations in advanced colorectal cancer by allele-specific single-base primer extension

Evaluation of: Magnin S, Viel E, Baraquin A et al. A multiplex SNaPshot assay as a rapid method for detecting KRAS and BRAF mutations in advanced colorectal cancers. J. Mol. Diagn. 13(5), 485–492 (2011). Since mutations in the KRAS and BRAF genes are associated with resistance to therapy with anticancer drugs targeting the EGF receptor pathway, the analysis of KRAS and BRAF mutational status has become an important tool in the clinical management of patients with advanced colorectal cancer. To be useful in the clinical setting, a diagnostic assay has to address several issues related to the sensitivity and specificity of the method, the modularity of the assay, the turnaround time and the running costs. A variety of methods have been applied to the diagnosis of KRAS and BRAF mutational status. Although there is a good concordance between different methods, differences exist regarding sensitivity, multiplexing capacity and costs. In this article, we review a recently published assay for the simultaneous detection of diagnostically relevant KRAS and BRAF mutations and discuss this work in the context of conventional diagnostic methods.

Metabolic Signature of Electrosurgical Liver Dissection

Background and Aims High frequency electrosurgery has a key role in the broadening application of liver surgery. Its molecular signature, i.e. the metabolites evolving from electrocauterization which may inhibit hepatic wound healing, have not been systematically studied. Methods Human liver samples were thus obtained during surgery before and after electrosurgical dissection and subjected to a two-stage metabolomic screening experiment (discovery sample: N = 18, replication sample: N = 20) using gas chromatography/mass spectrometry. Results In a set of 208 chemically defined metabolites, electrosurgical dissection lead to a distinct metabolic signature resulting in a separation in the first two dimensions of a principal components analysis. Six metabolites including glycolic acid, azelaic acid, 2-n-pentylfuran, dihydroactinidiolide, 2-butenal and n-pentanal were consistently increased after electrosurgery meeting the discovery (p<2.0×10−4) and the replication thresholds (p<3.5×10−3). Azelaic acid, a lipid peroxidation product from the fragmentation of abundant sn-2 linoleoyl residues, was most abundant and increased 8.1-fold after electrosurgical liver dissection (preplication = 1.6×10−4). The corresponding phospholipid hexadecyl azelaoyl glycerophosphocholine inhibited wound healing and tissue remodelling in scratch- and proliferation assays of hepatic stellate cells and cholangiocytes, and caused apoptosis dose-dependently in vitro, which may explain in part the tissue damage due to electrosurgery. Conclusion Hepatic electrosurgery generates a metabolic signature with characteristic lipid peroxidation products. Among these, azelaic acid shows a dose-dependent toxicity in liver cells and inhibits wound healing. These observations potentially pave the way for pharmacological intervention prior liver surgery to modify the metabolic response and prevent postoperative complications.