Verhandlungen der Deutschen Gesellschaft fur Pathologie最新文献

Mastocytosis is characterized by an abnormal proliferation and accumulation of mast cells (MC) in one or more organ systems. The current WHO classification discriminates cutaneous mastocytosis (CM) and various forms of systemic mastocytosis (SM). While CM usually follows a bening and often self-limiting course, SM is a persistent disease in which a somatic KIT mutation at codon 816 (i.e. D816V) is detectable in MC in at least 80% of cases. Symptoms in mastocytosis result from MC-derived mediators and, less frequently, from destructive tissue infiltration by MC. The clinical course of SM is usually indolent, but sometimes it may be highly aggressive and rapidly devastating. KIT is a transmembrane class III receptor tyrosine kinase which is required for MC growth, differentiation, and functional activation. Mutations in codon 816 of the KIT gene result in ligand-independent (constitutive) activation of KIT signaling and, thus, may play a central role in the pathogenesis of SM. Since there are no curative options, therapy for the aggressive forms of SM is based on cytoreductive agents, e.g. interferon-alpha (IFN-alpha) and cladribine. The expression of KIT in neoplastic MC has led to the development of targeted therapies using tyrosine kinase inhibitors (TKI) like STI571 (Imatinib, Gleevec). Unfortunately, the KIT mutation D816V is associated with relative resistance against STI571. However, TKIs with activity against KIT D816V-positive cells have recently been developed, and some of them (dasatinib, nilotinib/AMN107, PKC412) are already tested in phase I/II trials. In addition, non-TK KIT signaling inhibitors (e.g. geldanamycin, rapamycin) or monoclonal antibodies directed against neoplastic MC may evolve as future therapeutic options.

Invasion by colorectal carcinomas is characterized by an epithelial-mesenchymal transition (EMT)-like de-differentiation of the tumor cells. However a re-differentiation towards an epithelial phenotype, resembling a mesenchymal-epithelial transition (MET) is detectable in metastases. This indicates that malignant progression is based on dynamic processes, which can not be explained solely by irreversible genetic alterations, but must be additionally regulated by the tumor environment. The main oncoprotein in colorectal cancer is the Wnt-pathway effector beta-catenin, which is overexpressed due to mutations in the APC tumor suppressor in most cases. EMT of the tumor cells is associated with a nuclear accumulation of the transcriptional activator beta-catenin, which is reversed in metastases. Nuclear beta-catenin is involved in two fundamental processes in embryonic development: EMT and stem cell formation. Accumulating data demonstrate that aberrant nuclear expression of beta-catenin can confere these two abilites also to tumor cells. The unusual combination of EMT with stem cell competence might result in a migrating tumor stem cell, which drives tumor invasion and metastasis.

Testicular germ cell tumors comprise of group of pluripotent tumors including seminomas and nonseminomas, arise from intratubular germ cell neoplasia and originate from the primordial germ cells/ gonocytes. Many well characterized markers of embryonic stem cells including CD9, PODXL and centromere-specific histone-H3-like protein CENPA are consistently expressed in TGCTs. In embryonic stem cells, pluripotency and self renewal capacities are provided by a network of OCT3/4, NANOG and SOX2. In testicular germ cell tumors, pluripotency genes OCT3/4 und NANOG are upregulated both, in seminomas and non-seminomas, while SOX2 is differentially upregulated in embryonal carcinomas only. Similar to embryonic stem cells, most histological elements of type II GCTs are sensitive to chemotherapy and irradiation. Furthermore, all invasive TGCTs show a consistent gain of the short arm of chromosome 12, as found in ES cells upon extensive in vitro culturing. Moreover, the genetic constitution of testicular germ cell tumors can also be linked to characteristics of embryonic stem cells, likely related to their specific inability to repair DNA damage and their high sensitivity to apoptotic cell death. In conclusion, testicular germ cell tumors represent embryonic cancers found in adults. Both the seminomas and nonseminomas have their specific population of stem cells representative of the primordial germ cells/gonocytes and for embryonic stem cells, respectively.

Aims: Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer related mortality worldwide. The incidence is dramatically increasing and no effective systemic treatments are available accentuating the urgent need for novel treatment approaches. A growing body of evidence suggest that COX-2 signaling is implicated in carcinogenesis and this study was conducted to evaluate the potential of selective COX-2 inhibition for the treatment and prevention of HCCs.

Methods: The significance of COX-2 inhibition in HCCs was investigated in vitro (HCC cell-lines), in vivo (xenotransplanted tumors in nude mice) and ex vivo (precission-cut tissue sclice-cultures). Apoptosis-signaling was analyzed by means of immunohistochemistry, Western Blot analyses, Caspase-assays, FACS analyses after Nicoletti-staining, death receptor FACS-analysis, determination of mitochondrial membrane potential, and siRNA knockdown of Mcl-1.

Results: Selective COX-2 inhibition led to a marked tumor-specific growth inhibition of human HCCs in vitro, in vivo and ex vivo based on reduction of proliferation and induction of apoptosis. Both, the death receptor (extrinsic)-, as well as the mitochondrial (intrinsic)-apoptotic pathways were involved. COX-2 inhibition led to an increased surface expression of death receptors and a marked down-regulation of Mcl-1, followed by translocation of Bax to mitochondria and a consecutive release of cytochrome c. Of clinical importance, COX-2 inhibition acted synergistically with chemotherapeutic drugs in the induction of apoptosis whereas primary human-hepatocytes were not sensitized towards apoptosis.

Conclusion: COX-2 inhibition offers therapeutic and preventive potential in HCC.

Tuberculosis remains a leading cause of morbidity and mortality worldwide. A rapid and reliable diagnosis and discrimination from infections with nontuberculous mycobacteria (NTM) is critical. Frequently, formalin-fixed, paraffin-embedded (FFPE) tissues remain the only source for detection of micro-organisms in suspected cases of mycobacterial infection. Recently, numerous methods, including PCR assays, in situ hybridization and immunohistochemistry have been developed for detection of mycobacteria in FFPE samples. PCR-based assays are directed either against M.tbc.-specific sequences, such as IS6110, or amplify regions common to many mycobacterial species, e.g. the 65 kDa antigen, and then require sequencing or restriction fragment length polymorphism for species identification. Whereas the detection of DNA of M.tbc. in the correct setting is always of clinical relevance, the presence of various NTM species has to be interpreted with great caution due to their ubiquitous nature. However, the routine application of molecular tests has demonstrated that NTM infections are more common than previously thought, even in non-immunosuppressed hosts. The introduction of real-time PCR technology allows precise quantification of mycobacterial DNA and can be used for species identification through melting point analysis or appropriate DNA probes. Application of these assays originally developed for clinical microbiology offer a great opportunity for diagnostic improvement in molecular pathology as compared to qualitative PCR, mainly due to an increased specificity and a lower risk of contamination. Given the clinical impact of a positive molecular result for M. tbc., future efforts have to be aimed at standardization and quality control.

Aims: The identification of precursor lesions has a great impact on our understanding of tumorigenesis. In this study we investigated whether preneoplastic lesions can be identified in sporadic gastrinomas and in gastrinomas in multiple endocrine neoplasia type 1 (MEN1) patients. These lesions were tested for loss of heterozygosity (LOH) of the MEN1 gene locus on chromosome 11q13.

Material and methods: Tissue specimens from 25 patients with Zollinger-Ellison syndrome (ZES) were analyzed. The MEN1 status was assessed clinically and by mutational analysis. For simultaneous analysis of hormones and allelic deletions a combined FISH fluorescence in situ hybridization/immunofluorescence protocol was established.

Results: Hyperplastic gastrin cell lesions were present in the nontumorous mucosa of all MEN1 patients, but not in 12 patients with sporadic duodenal gastrinomas. The hyperplastic gastrin cells retained both 11q13 alleles. 11q13 LOH was, however, detected in duodenal gastrinomas, some as small as 300 microm in diameter, in 13 patients with MEN1.

Conclusions: MEN1-associated duodenal gastrinomas, but not sporadic gastrinomas, are associated with gastrin cell hyperplasia. It is therefore likely that hyperplastic gastrin cell lesions precede the development of MEN1-associated duodenal gastrinomas. Allelic deletion of the MEN1 gene locus may reflect a decisive initial event in the development of multifocal MEN1-associated gastrinomas from hyperplastic gastrin cell lesions.

Objectives: This study analyzes changes in the degree of global methylationlevel in myelodysplastic syndrome during progression of the disease.

Methods: Methylation status was analyzed in 127 patients with histologically confirmed MDS and 26 reactive controls. We employed Pyrosequencing, Luminometric Methylation Assay (LUMA) and a realtime PCR-based quantitative assay.

Results: We detected an increase of methylation level of LINE-1 sequences using pyrosequencing and an increase of methylation in the HpaII recognition site employing LUMA during the progression of MDS. Methylation sensitive quantitative PCR showed no statistically significant differences, only a trend.

Conclusions: LINE-1 and methylation sensitive cleavage of DNA can act as a surrogatmarker for global DNA methylation. The genome wide hypermethylation of MDS is a distinct feature of this disease. It discriminates MDS from other neoplasia and may explains the success of hypomethylation inducing reagents like azadeoxycytidine in MDS therapy.

The classification of soft tissue tumors is based on the recognition of the resemblance to normal tissue or cells. Nowadays, molecular pathologic findings essentially may contribute to the diagnosis. In daily practice, however, the evaluation of HE sections and immunohistochemical findings are most important because these methods are widely available. Nevertheless, misinterpretations are possible if certain rules and limitations in data utilization for diagnosis are not considered. There are some problematic zones referring to this in which especial attention is mandatory. By means of examples difficulties are explained which may result from overlapping morphological features between soft tissue tumors, between nerve sheath tumors and melanocytic neoplasms, and between soft tissue tumors and sarcomatoid carcinomas. The necessity of a careful interpretation of immunohistochemical findings is underscored with selecting actin positivity as example. Finally, difficulties in determining the dignity of a soft tissue tumor are discussed. Moreover, tumor heterogeneity may under certain conditions render more difficult the classification of a soft tissue tumor.

Lymphoid organs such as thymus and lymph node develop from anlagen during embryonic development. This process is known to rely and chemokine producing stroma cells as well as lymphoid tissue inducers (LTI) cells expressing the chemokine receptors. In addition to those secondary lymphoid organs it is well known that lymphoid structures can be induced even in adults as a consequence of chronic inflammatory insults. Currently little is known about the molecular mechanisms that control the development, maintenance and organization of these tertiary lymphoid organs. In this presentation, I will summaries present knowledge on the role of the chemokine system during lymphoid organ development and will present new data on the role of chemokine-driven homing of regulatory T cells in controlling the development of tertiary lymphoid organs.