Ralf J. Rieker

Histologic classification of thymic epithelial tumors: comparison of established classification schemes.

The object of our multicenter retrospective study was to compare the new histologic World Health Organization (WHO) classification and the classical histologic Bernatz classification in terms of interobserver agreement and prognostic importance. The influence of coexisting diseases was also analyzed using the Charlson score. We evaluated 218 patients from 5 different hospitals who were treated between 1967 and 1998. The statistical methods of analysis included Kaplan‐Meier estimates of survival curves and the application of Cox proportional hazards models to identify sets of prognostic factors for survival. Interobserver agreement was assessed by kappa coefficients. For both WHO and Bernatz classifications, interobserver agreement was good (weighted kappa > 0.87). However, the subdiversification of the “bioactive” WHO subgroup (B1, B2, B3) resulted in an interobserver agreement of only 0.49 within this group. In multivariable models, both the WHO classification and the Bernatz classification including carcinomas showed similar prognostic capabilities. The B3 type in the WHO classification and the predominantly epithelial type in the Bernatz classification had an intermediate prognostic ranking in comparison with the carcinomas and with the other subgroups. For both classifications, further simplification and subclassification into 3 subgroups led to classes with good discriminative power in respect to survival. In addition, very good interobserver agreement was observed in the simplified classifications. Comorbidity, sex, age of the patient and lymphofollicular hyperplasia had no major influence on overall survival. Both classifications showed similar prognostic power. Interobserver agreement of the type B subgroups was only moderate. By simplification of the classifications, subgroups with distinct survival could be identified.

β-catenin accumulation and mutation of the CTNNB1 gene in hepatoblastoma

Hepatoblastoma is a rare malignant tumor of the liver that occurs in children at an average age of 2 to 3 years. Epidemiologic studies have shown an increased frequency of this tumor type in families affected by adenomatous polyposis coli. In addition to the epidemiologic data, molecular genetic studies suggest that inactivation of the APC tumor suppressor may be involved in hepatoblastoma tumorigenesis. A major function of APC is the downregulation of β‐catenin, a transcription‐activating protein with oncogenic potential. In an ongoing immunohistochemical study of β‐catenin expression in sporadic cases of tumor types that are associated with adenomatous polyposis coli, we observed increased β‐catenin levels in the cytoplasm and in the nuclei of three investigated hepatoblastomas. Sequencing of exon 3 of the β‐catenin gene (CTNNB1) revealed an activating mutation in one of the tumor samples. Our data indicate for the first time that β‐catenin accumulation may play a role in the development of hepatoblastoma and that activating mutations of the β‐catenin gene may substitute biallelic APC inactivation in this tumor type. Genes Chromosomes Cancer 25:399–402, 1999.

Overexpression of the far upstream element binding protein 1 in hepatocellular carcinoma is required for tumor growth

We identified the far upstream element binding protein 1 (FBP1), an activator of transcription of the proto‐oncogene c‐myc, in a functional yeast survival screen for tumor‐related antiapoptotic proteins and demonstrated strong overexpression of FBP1 in human hepatocellular carcinoma (HCC). Knockdown of the protein in HCC cells resulted in increased sensitivity to apoptotic stimuli, reduced cell proliferation, and impaired tumor formation in a mouse xenograft transplantation model. Interestingly, analysis of gene regulation in these cells revealed that c‐myc levels were not influenced by FBP1 in HCC cells. Instead, we identified the cell cycle inhibitor p21 as a direct target gene repressed by FBP1, and in addition, expression levels of the proapoptotic genes tumor necrosis factor α, tumor necrosis factor–related apoptosis‐inducing ligand, Noxa, and Bik were elevated in the absence of FBP1. Conclusion: Our data establish FBP1 as an important oncoprotein overexpressed in HCC that induces tumor propagation through direct or indirect repression of cell cycle inhibitors and proapoptotic target genes. (HEPATOLOGY 2009.)

EGFR mutational status in a large series of Caucasian European NSCLC patients: data from daily practice.

Background:The prognosis of metastatic non-small cell lung cancer (NSCLC) is still poor. Activating epithelial growth factor receptor (EGFR) mutations are important genetic alterations with dramatic therapeutical implications. Up to now, in contrast to Asian populations only limited data on the prevalence of those mutations are available from patients with Caucasian and especially European ethnicity.Methods:In this multicentre study, 1201 unselected NSCLC patients from Southern Germany were tested in the daily clinical routine for EGFR mutation status.Results:Activating EGFR mutations were found in 9.8% of all tumours. Mutations in exons 18, 19 and 21 accounted for 4.2%, 61.9% and 33.1% of all mutations, respectively. Non-smokers had a significantly higher rate of EGFR mutations than smokers or ex-smokers (24.4% vs 4.2%; P<0.001). Non-lepidic-non-mucinous adenocarcinomas (G2) accounted for 45.5% of all activating EGFR mutations and 3.5% of all squamous cell carcinomas were tested positive. Thyroid transcription factor 1 protein expression was significantly associated with EGFR mutational status.Conclusion:These comprehensive data from clinical routine in Germany add to the knowledge of clinical and histopathological factors associated with EGFR mutational status in NSCLC.

Targeting heat shock protein 90 with non-quinone inhibitors: a novel chemotherapeutic approach in human hepatocellular carcinoma.

The inhibition of heat shock protein 90 (Hsp90) has emerged as a promising antineoplastic strategy in diverse human malignancies. Hsp90 has been predicted to be involved in hepatocellular carcinoma (HCC) development; however, its role in hepatocarcinogenesis remains elusive. Using chemically distinctive Hsp90 inhibitors, we show that Hsp90 capacitates the aberrant expression and activity of crucial hepatocarcinogenesis‐driving factors (e.g., insulin‐like growth factor receptor 1, hepatocyte growth factor receptor, protein kinase B, v‐raf‐1 murine leukemia viral oncogene homolog 1, and cyclin‐dependent kinase 4). In vitro, Hsp90 inhibition with both geldanamycin analogs (17‐allylamino‐17‐desmethoxygeldanamycin (17‐AAG) and 17‐dimethylaminoethylamino‐17‐desmethoxygeldanamycin (17‐DMAG)) and the non‐quinone compound 8‐(6‐iodobenzo[d][1,3]dioxol‐5‐ylthio)‐9‐(3‐(isopropylamino)propyl)‐9H‐purin‐6‐amine (PU‐H71) reduced the viability of various HCC cell lines, induced the simultaneous degradation of numerous hepatocarcinogenic factors, and caused substantial cell cycle arrest and apoptosis. In contrast, nontumorigenic hepatocytes were less susceptible to Hsp90 inhibition. Because conventional geldanamycin‐derivate Hsp90 inhibitors induce dose‐limiting liver toxicity, we tested whether novel Hsp90 inhibitors lacking the benzoquinone moiety, which has been deemed responsible for hepatotoxicity, can elicit antineoplastic activity without causing significant liver damage. In HCC xenograft mouse models, PU‐H71 was retained in tumors at pharmacologically relevant concentrations while being rapidly cleared from nontumorous liver. PU‐H71 showed potent and prolonged in vivo Hsp90 inhibitory activity and reduced tumor growth without causing toxicity. Conclusion: Hsp90 constitutes a promising therapeutic target in HCC. Non‐quinone Hsp90 inhibitors exhibit tumor‐specific accumulation and exert potent antineoplastic activity without causing significant hepatotoxicity. (HEPATOLOGY 2009.)

Cystic lymphangioma of the small-bowel mesentery : Case report and a review of the literature

Cystic lymphangioma of the small-bowel mesentery is a rare manifestation of an intraabdominal tumor in elderly patients. We present a case of a small-bowel mesentery lymphangioma, causing fever and chills and present clinical and pathologic features. Furthermore, etiology and differential diagnosis of this tumor are discussed.

ISL1 expression is not restricted to pancreatic well-differentiated neuroendocrine neoplasms, but is also commonly found in well and poorly differentiated neuroendocrine neoplasms of extrapancreatic origin

The human insulin gene enhancer-binding protein islet-1 (ISL1) is a transcription factor involved in the differentiation of the neuroendocrine pancreatic cells. Recent studies identified ISL1 as a marker for pancreatic well-differentiated neuroendocrine neoplasms. However, little is known about ISL1 expression in pancreatic poorly differentiated and in extrapancreatic well and poorly differentiated neuroendocrine neoplasms. We studied the immunohistochemical expression of ISL1 in 124 neuroendocrine neoplasms. Among pancreatic neuroendocrine neoplasms, 12/13 with poor differentiation were negative, whereas 5/7 with good differentiation but a Ki67 >20% were positive. In extrapancreatic neuroendocrine neoplasms, strong positivity was found in Merkel cell carcinomas (25/25), pulmonary small cell neuroendocrine carcinomas (21/23), medullary thyroid carcinomas (9/9), paragangliomas/pheochromocytomas (6/6), adrenal neuroblastomas (8/8) and head and neck neuroendocrine carcinomas (4/5), whereas no or only weak staining was recorded in pulmonary carcinoids (3/15), olfactory neuroblastomas (1/4) and basaloid head and neck squamous cell carcinomas (0/15). ISL1 stained the neuroendocrine carcinoma component of 5/8 composite carcinomas and also normal neuroendocrine cells in the thyroid, adrenal medulla, stomach and colorectum. Poorly differentiated neuroendocrine neoplasms, regardless of their ISL1 expression, were usually TP53 positive. Our results show the almost ubiquitous expression of ISL1 in extrapancreatic poorly differentiated neuroendocrine neoplasms and neuroblastic malignancies and its common loss in pancreatic poorly differentiated neuroendocrine neoplasms. These findings modify the role of ISL1 as a marker for pancreatic neuroendocrine neoplasms and suggest that ISL1 has a broader involvement in differentiation and growth of neuroendocrine neoplasms than has so far been assumed.

Clusters of chromosomal imbalances in thymic epithelial tumours are associated with the WHO classification and the staging system according to Masaoka

Using comparative genomic hybridisation, we investigated chromosomal imbalances in 28 cases of thymic epithelial neoplasms including type A, B2, B3, the A component of type AB and different subtypes of type C thymoma. To identify different patterns of chromosomal aberrations associated with the biological behaviour and the histological diversity of thymomas, a hierarchical cluster analysis of 65 cases was performed. The here‐reported Comparative Genomic Hybridisation (CGH) data (28 cases) of partly uninvestigated tumour subtypes were pooled with previously published data of chromosomal imbalances of 37 thymomas (Zettl et al. [Am J Pathol 2000;157:257–66]). The analysis of 278 chromosomal subbands yielded 2 main clusters. The first main cluster was characterised by gains of the chromosomal arm 1q, consisted only of type C and B3 thymomas and was further subdivided into 2 subgroups. To the first subgroup only thymomas were attributed, which, in addition to gains of the chromosomal arm 1q, showed losses on 6q and 16q, whereas tumours belonging to the second subgroup exhibited no further recurrent chromosomal alterations. The second main cluster was formed by a heterogeneous group of thymoma types (types A, AB, B2, B3 and C), showing no specific pattern of chromosomal imbalances. In 19 thymomas, no chromosomal imbalances could be detected (3 type B2 and 5 type A thymomas of our study as well as 11 type A thymomas investigated by Zettl et al., Am J Pathol 2000;157:257–66). Chromosomal imbalances were more frequent in type C thymomas than in other subtypes. The distribution of tumour stages according to Masaoka (p = 0.003) and the World Health Organisation (WHO) classification (p < 0.0001) was significantly different in the clusters and subgroups obtained. The groups reflect the staging system and the WHO classification and show that type B3 and type C carcinomas have a strong relationship concerning their chromosomal imbalances. Furthermore, chromosomal imbalances detected in some type A thymomas might be responsible for the aggressive behaviour described in a few cases of this thymoma subtype.

Mutational activation of the RAS-RAF-MAPK and the Wnt pathway in small intestinal adenocarcinomas.

Background: Adenocarcinomas of the small and the large intestine share risk factors and morphological features but both tumor types seem to follow different genetic pathways. The aim of this study on small intestinal carcinomas was to analyze alternative mechanisms of activation of pathways that are typically affected in colorectal cancer. Methods: Twenty‐one sporadic carcinomas were investigated for mutations in KRAS, BRAF, the β‐catenin gene CTNNB1, and the mutational cluster region of APC. Immunohistochemical analysis was performed with a monoclonal antibody for β‐catenin, the transcriptionally active downstream component of wnt signaling. Results: Oncogene mutations were found in 13 (62%) small intestinal adenocarcinomas. Twelve tumors displayed a KRAS mutation, and a novel BRAF mutation at codon 603/604 was seen in one carcinoma without KRAS mutation. One tumor harbored a CTNNB1 mutation consisting of an insertion of 247 nucleotides deriving from chromosome 9. APC mutations were identified in 2 tumors. Immunohistochemistry demonstrated nuclear accumulation of β‐catenin in 5 carcinomas. These carcinomas included the tumor with a CTNNB1 mutation but not those with APC mutations. Conclusions: Our data show frequent activation of the RAS‐RAF‐MAPK pathway through mutations of either KRAS or, infrequently, BRAF. Activation of the wnt pathway through accumulation of β‐catenin may have a role in a subset of small intestinal adenocarcinomas but in contrast to colorectal carcinoma, accumulation of β‐catenin is generally not caused by inactivating APC or activating CTNNB1 mutations.

Comparison of losses of heterozygosity and replication errors in primary colorectal carcinomas and corresponding liver metastases

In order to investigate genetic alterations specific to liver metastases of colorectal carcinomas, losses of heterozygosity and replication errors have been compared in 15 cases of primary colorectal carcinoma and in the corresponding metastatic liver tumours. Fifteen microsatellite markers located on 13 different chromosomal arms were used in the study. The LOH patterns of the primary and the metastatic tumours were identical in eight cases and showed differences in seven cases. Areas of deletion predominantly or completely common to the colorectal and the metastatic tumour were detected on chromosomes 5q, 8p, 17p, 18q, and 22q. Preferential loss in metastatic tumours was observed on chromosomal arm 3p. Replication errors were found in four primary tumours and in three of the corresponding secondaries. A replication error phenotype specific to a metastasis was not observed. Copyright