Christiane Schewe

Strong inhibition of mammalian lipoxygenases by the antiinflammatory seleno-organic compound ebselen in the absence of glutathione

Both human recombinant 5-lipoxygenase (EC 1.13.11.34) and 15-lipoxygenase (EC 1.13.11.33, mammalian enzyme) purified from rabbit reticulocytes were inhibited in the absence of glutathione (GSH) by submicromolar concentrations of the seleno-organic compound ebselen. These concentrations were comparable to those of the enzymes. Soybean lipoxygenase-1 (EC 1.13.11.33, plant enzyme) was not inhibited, whereas prostaglandin endoperoxide synthase-1 (EC 1.14.99.1) was inhibited only at much higher concentrations of ebselen (IC50 = 37.7 +/- 4.3 microM). The action of ebselen on reticulocyte 15-lipoxygenase (IC50 = 0.17 +/- 0.01 microM) was studied in detail. Inhibition occurred instantaneously and appeared to be reversible and was largely abolished by a 20-fold molar excess of GSH over ebselen. In the presence of 1 mM GSH 50% inhibition was observed only at ebselen concentrations as high as 234 +/- 27 microM. 13S-hydroperoxy-9Z, 11E-octadecadienoic acid, the lipoxygenase product formed from linoleic acid, augmented the inhibitory effect at low concentrations and caused a partial reversal at high concentrations. A variety of derivatives or structural analogues of ebselen were also tested and proved to be either inactive or weaker inhibitors of 15-lipoxygenase. We have concluded that the potent inhibition of 15-lipoxygenase by ebselen is due neither to GSH peroxidase-like activity nor to lowering of the hydroperoxide tone. The pharmacological implications of these unique characteristics of the action of ebselen on lipoxygenases are then discussed.

Chromosomal imbalances in brain metastases of solid tumors.

Metastases account for approximately 50% of the malignant tumors in the brain. In order to identify structural alterations that are associated with tumor dissemination into the central nervous system we used Comparative Genomic Hybridization (CGH) to investigate 42 brain metastases and 3 primary tumors of 40 patients. The metastases originated from lung cancer (14 cases), melanomas (7), carcinomas of breast (5), colon (5), kidney (5), adrenal gland (1) and thyroid (1). In addition, tumors of initially unknown primaries were assessed in 3 cases. The highest incidence of DNA gains were observed for the chromosomal regions 1q23, 8q24, 17q24‐q25, 20q13 (>80% of cases) followed by the gain on 7p12 (77%). DNA losses were slightly less frequent with 4q22, 4q26, 5q21, 9p21 being affected in at least 70% of the cases followed by deletions at 17p12, 4q32‐q34, 10q21, 10q23‐q24 and 18q21‐q22 in 67.5% of cases. Two unusual narrow regional peaks were observed for the gain on 17q24‐q25 and loss on 17p12.The incidence at individual loci can be viewed at our CGH online tumor database at http://www.amba.charite.de/cgh. The metastases of each tumor type showed a recurrent pattern of changes. In those cases with primary tumor and metastases available, the CGH pattern exhibited a high degree of conformity. In conclusion, our data suggests that specific genetic lesions are associated with tumor dissemination into the nervous system and that CGH analysis may be a useful supplementary tool for classification of metastases with unknown origin.

Nucleolin as Activator of Human Papillomavirus Type 18 Oncogene Transcription in Cervical Cancer

High risk human papillomaviruses (HPVs) are central to the development of cervical cancer and the deregulated expression of high risk HPV oncogenes is a critical event in this process. Here, we find that the cell protein nucleolin binds in a sequence-specific manner to the HPV18 enhancer. The DNA binding activity of nucleolin is primarily S phase specific, much like the transcription of the E6 and E7 oncoproteins of HPV18 in cervical cancer cells. Antisense inactivation of nucleolin blocks E6 and E7 oncogene transcription and selectively decreases HPV18+ cervical cancer cell growth. Furthermore, nucleolin controls the chromatin structure of the HPV18 enhancer. In contrast, HPV16 oncogene transcription and proliferation rates of HPV16+ SiHa cervical cancer cells are independent of nucleolin activity. Moreover, nucleolin expression is altered in HPV18+ precancerous and cancerous tissue from the cervix uteri. Whereas nucleolin was homogeneously distributed in the nuclei of normal epithelial cells, it showed a speckled nuclear phenotype in HPV18+ carcinomas. Thus, the host cell protein nucleolin is directly linked to HPV18-induced cervical carcinogenesis.

Molecular HPV Typing as a Diagnostic Tool to Discriminate Primary From Metastatic Squamous Cell Carcinoma of the Lung

In this study, typing of human papilloma virus (HPV) was performed in squamous cell carcinomas of the lung (n=26) as well as putative primaries of head and neck (n=21) and female genital tract (n=5) of the same patients, to test whether additional information to discriminate lung primaries from metastases can be gained by a direct comparison of the HPV status in both tumors. In 3 (14.2%) patients with head and neck as well as lung squamous cell carcinoma, an identical HPV subtype could be detected in both tumors suggesting metastatic disease. In 9 (42.9%) cases, discordant HPV status strongly suggested secondary primaries of the lung. In the remaining 9 (42.9%) patients, no HPV was evident in either tumor. In all patients with carcinomas of the cervix uteri an identical HPV subtype was detected in the cervical and in the lung tumor. In conclusion, the results suggest HPV typing, a method routinely used in cervical biopsies for years, as a very useful diagnostic tool to discriminate primary from metastatic squamous cell carcinoma of the lung, which in our cohort in 57.1% of cases allowed for almost definite classification.

Analysis of PIK3CA mutations in breast cancer subtypes.

Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit &agr; (PIK3CA) is a central element of a signaling pathway involved in cell proliferation, survival, and growth. Certain mutations in this pathway result in enhanced PI3K signaling, which is associated with oncogenic cellular transformation and cancer. The aims of this study were to characterize different types of PIK3CA mutations in exons 9 and 20 in a series of primary breast carcinomas and to correlate the results with clinicopathologic parameters and survival. We used frozen tissue samples and sequenced exons 9 and 20 for a series of 241 patients with a diagnosis of breast carcinoma. We found that 15.8% of the primary breast carcinomas possessed PIK3CA mutations in either exon 9 or exon 20. The rate of PIK3CA mutations was increased in HR+/HER2− tumors (18.6%), but this difference did not reach a statistical significance. The lowest rate of mutations was observed in HR+/HER2+ tumors (5.3%). No statistically significant association was found between the presence of PIK3CA mutations and the prognostic/clinical features of breast cancer, including histologic subtype, Her2 status, axillary lymph node involvement, tumor grade, and tumor stage. However, the presence of the H1047R mutation in 10 samples was associated with a statistically significantly worse overall survival. PIK3CA mutation was found to be a frequent genetic change in all breast cancer subtypes but occurred with the highest rate in HR+/HER2− tumors. Further studies are needed to validate the prognostic impact of different PIK3CA mutations.

Inter-laboratory validation of PCR-based detection of Mycobacterium tuberculosis in formalin-fixed, paraffin-embedded tissues

The present study is based on the initiative for quality assurance in pathology of the German Society of Pathology and the Professional Association of German Pathologists. Four panel laboratories with experience and expertise in polymerase chain reaction (PCR) detection of Mycobacterium tuberculosis were selected to establish the prerequisites for continuous external laboratory trials, in particular, by providing pre-tested specimens and evaluation criteria for participating institutes. In the first step, the four panel laboratories performed an internal trial to test their own reliability and reproducibility. Paraffin sections and DNA preparations from 34 tissues (25 clinical specimens and 9 controls) totalling to 66 samples were evaluated by each panel institute according to their own protocols. The methodologies differed and are described in detail. Despite these differences, a high degree of inter-laboratory reliability was achieved. In this report, we summarise our results including the correlation with the histology and provide recommendations for applying PCR-based methodology for the detection of mycobacterial DNA in surgical specimens. Supplementary data are available online at http://www.charite.de/ch/patho (rubric “Forschung”). Pre-tested specimens are now available for the external trial and can be ordered from the steering institute via Oligene (http://www.oligene.com/). All molecular pathology laboratories are invited to participate in this quality assurance initiative.

Fatal atypical T-cell proliferation associated with Epstein-Barr virus infection.

We report the case of a young Caucasian man who presented with polyneuropathy and severe, ultimately fatal, congestive heart failure in the context of a chronic active Epstein–Barr virus (EBV) infection. Post‐mortem examination revealed both monoclonal and polyclonal proliferation of EBV‐positive atypical T lymphocytes within different organs. Predominant infiltration of the nervous system and heart with extensive myocardial scarring accounted for the clinical symptoms. The remarkable features of this case are (i) the occurrence in a Caucasian patient, (ii) the absence of detectable immunodeficiency, and (iii) the myocardial destruction by EBV‐infected monoclonal T cells.

HPV typing and CGH analysis for the differentiation of primary and metastatic squamous cell carcinomas of the aerodigestive tract

Human papilloma virus (HPV) typing and Comparative Genomic Hybridisation (CGH) analysis can be used in the classification of multiple tumours of the aerodigestive tract for the differentiation between secondary malignancy versus metastasis. We present 3 exemplary cases of patients with multiple squamous cell carcinomas, localised within the head and neck region, cervical lymph node and the lung. In two patients, HPV typing identified HPV type 16 in the tonsillar carcinomas and the corresponding cervical lymph node and lung carcinoma indicating that the latter were metastatic spreads. In case 1, CGH confirmed the clonal relationship. Case two showed a peculiar syncytial growth pattern with lymphocytic infiltration which may constitute a potential morphological marker for HPV infection. In case three, a vallecular carcinoma was HPV negative while a lung cancer was positive for HPV type 6 indicating two independent primary tumours. Our case triplet illustrates the variability of HPV infection in squamous cell cancer of the aerodigestive tract and power as well as limitations of morphology, HPV typing and tumour genetics in the classification of multiple tumours.

Applicability of a System for fully automated nucleic acid extraction from formalin-fixed paraffin-embedded sections for routine KRAS mutation testing.

Due to the approval of various new targeted therapies for the treatment of cancer, molecular pathology laboratories with a diagnostic focus have to meet new challenges: simultaneous handling of a large number of samples, small amounts of input material, and fragmentation of nucleic acids because of formalin fixation. As a consequence, fully automated systems for a fast and standardized extraction of high-quality DNA from formalin-fixed paraffin-embedded (FFPE) tissues are urgently needed. In this study, we tested the performance of a fully automated, high-throughput method for the extraction of nucleic acids from FFPE tissues. We investigated the extraction performance in sections of 5 different tissue types often analyzed in routine pathology laboratories (cervix, colon, liver, lymph node, and lung; n=340). Furthermore, we compared the quality, labor input, and applicability of the method for diagnostic purposes with those of a laboratory-validated manual method in a clinical setting by screening a set of 45 colorectal adenocarcinoma for the KRAS mutation. Automated extraction of both DNA and RNA was successful in 339 of 340 FFPE samples representing 5 different tissue types. In comparison with a conventional manual extraction protocol, the method showed an overall agreement of 97.7% (95% confidence interval, 88.2%-99.9%) for the subsequent mutational analysis of the KRAS gene in colorectal cancer samples. The fully automated system is a promising tool for a simple, robust, and rapid extraction of DNA and RNA from formalin-fixed tissue. It ensures a standardization of sample processing and can be applied to clinical FFPE samples in routine pathology.