DNA demethylation and tri-methylation of H3K4 at the TACSTD2 promoter are complementary players for TROP2 regulation in colorectal cancer cells.

TROP2 is a powerful cancer driver in colorectal cancer cells. Divergent epigenetic regulation mechanisms for the corresponding TACSTD2 gene exist such as miRNAs or DNA methylation. However, the role of TACSTD2 promoter hypermethylation in colorectal cancer has not been investigated yet. In this study, TROP2 expression strongly correlated with promoter methylation in different colorectal tumor cell lines. Treatment with 5-Azacytidine, a DNMT1 inhibitor, led to demethylation of the TACSTD2 promoter accompanied by an increase in TROP2 protein expression. TROP2 expression correlated with promoter methylation in vivo in human colon tumor tissue, thereby verifying promoter methylation as an important factor in the regulation of TROP2 expression in colorectal cancer. When performing a ChIP-Seq analysis in HCT116 and HT29 cells, we found that TACSTD2 promoter demethylation was accompanied by tri-methylation of H3K4. In silico analysis of GSE156613 data set confirmed that a higher binding of histone mark H3K4me3 around the TACSTD2 promoter was found in TACSTD2 high expressing tumors of colon cancer patients compared to the corresponding adjacent tumor tissue. Moreover, the link between TROP2 and the H3K4me3 code was even evident in tumors showing high intratumoral heterogeneity for TROP2 staining. Our data provide novel evidence for promoter demethylation and simultaneous gains of the active histone mark H3K4me3 across CpG-rich sequences, both being complementary mechanisms in the transcriptional regulation of TACSTD2 in colon cancer. The functional consequences of TROP2 loss in colorectal cancer needs to be further investigated.

Hypermethylation and loss of retinoic acid receptor responder 1 expression in human choriocarcinoma.

BACKGROUND: Human placental development resembles tumorigenesis, due to the invasive and fusogenic potential of trophoblasts. However, these features are tightly controlled in trophoblasts. Disturbance of this spatial and temporal regulation is thought to contribute to the rare formation of choriocarcinomas. Promoter hypermethylation and loss of the tumor suppressor Retinoic acid receptor responder 1 (RARRES1) were shown to contribute to cancer progression. Our study investigated the epigenetic and transcriptional regulation of RARRES1 in healthy human placenta in comparison to choriocarcinoma cell lines and cases. METHODS: Three choriocarcinoma cell lines (Jeg-3, JAR and BeWo) were treated with three different retinoic acid derivates (Am580, Tazarotene and all-trans retinoic acid) and 5-aza-2'-deoxycytidine. We analyzed RARRES1 promoter methylation by pyrosequencing and performed realtime-PCR quantification to determine RARRES1 expression in placental tissue and trophoblastic cell lines. Additionally, RARRES1 was stained in healthy placentas and in biopsies of choriocarcinoma cases (n = 10) as well as the first trimester trophoblast cell line Swan71 by immunofluorescence and immunohistochemistry. RESULTS: In the choriocarcinoma cell lines, RARRES1 expression could not be induced by sole retinoic acid treatment. Stimulation with 5-aza-2'-deoxycytidine significantly induced RARRES1 expression, which then could be further increased with Am580, Tazarotene and all-trans retinoic acid. In comparison to healthy placenta, choriocarcinoma cell lines showed a hypermethylation of the RARRES1 promoter, which correlated with a reduced RARRES1 expression. In concordance, RARRES1 protein expression was lost in choriocarcinoma tissue. Additionally, in the trophoblastic cell line Swan71, we found a significant induction of RARRES1 expression with increased cell density, during mitosis and in syncytial knots. CONCLUSIONS: Our findings showed that RARRES1 expression is absent in choriocarcinoma due to promoter methylation. Based on our analysis, we hypothesize that RARRES1 might exert tumor suppressive functions in multiple cellular processes (e.g. cell cycle regulation, adhesion, invasion and apoptosis).

Multi-colour FISH in oesophageal adenocarcinoma-predictors of prognosis independent of stage and grade.

BACKGROUND: Oesophageal adenocarcinoma or Barrett's adenocarcinoma (EAC) is increasing in incidence and stratification of prognosis might improve disease management. Multi-colour fluorescence in situ hybridisation (FISH) investigating ERBB2, MYC, CDKN2A and ZNF217 has recently shown promising results for the diagnosis of dysplasia and cancer using cytological samples. METHODS: To identify markers of prognosis we targeted four selected gene loci using multi-colour FISH applied to a tissue microarray containing 130 EAC samples. Prognostic predictors (P1, P2, P3) based on genomic copy numbers of the four loci were statistically assessed to stratify patients according to overall survival in combination with clinical data. RESULTS: The best stratification into favourable and unfavourable prognoses was shown by P1, percentage of cells with less than two ZNF217 signals; P2, percentage of cells with fewer ERBB2- than ZNF217 signals; and P3, overall ratio of ERBB2-/ZNF217 signals. Median survival times for P1 were 32 vs 73 months, 28 vs 73 months for P2; and 27 vs 65 months for P3. Regarding each tumour grade P2 subdivided patients into distinct prognostic groups independently within each grade, with different median survival times of at least 35 months. CONCLUSIONS: Cell signal number of the ERBB2 and ZNF217 loci showed independence from tumour stage and differentiation grade. The prognostic value of multi-colour FISH-assays is applicable to EAC and is superior to single markers.

Mutation landscape in melanoma patients clinical implications of heterogeneity of BRAF mutations.

BACKGROUND: The detection of V600E BRAF mutations has fundamental clinical consequences as the treatment option with BRAF inhibitors such as vemurafenib or dabrafenib yields response rates of ~48%. Heterogeneity with respect to BRAF mutation in different metastases has been described in single cases. As this has important implications for the determination of BRAF status and treatment of patients, it is essential to acquire more data. METHODS: A total of 300 tumour samples from 187 melanoma patients were analysed for BRAF mutations by pyrosequencing. Equivocal results were confirmed by capillary sequencing. Clinical data with respect to melanoma type, tumour site and survival were summarised for 53 patients with multiple analysed tumour samples (2-13 per patient). RESULTS: BRAF mutations were found in 84 patients (44.9%) and 144 tumour samples (48%) with BRAF mutations in 45.5% of primary tumours and 51.3% of metastases, respectively. In 10 out of 53 patients (18.9%) where multiple samples were analysed results were discordant with respect to mutation findings with wild-type and mutated tumours in the same patient. Mutations did not appear more frequently over the course of disease nor was its occurrence associated with a specific localisation of metastases. CONCLUSION: As heterogeneity with respect to BRAF mutation status is detected in melanoma patients, subsequent testing of initially wild-type patients can yield different results and thus make BRAF inhibitor therapy accessible. The role of heterogeneity in testing and for clinical response to therapy with a BRAF inhibitor needs to be further investigated.

Rare BRAF mutations in melanoma patients: implications for molecular testing in clinical practice.

BACKGROUND: The detection of V600E BRAF mutation in melanoma is fundamental since here BRAF inhibitors represent an effective treatment. Non-V600E BRAF mutations that may also respond are not detected by certain screening methods. Thus, knowledge about detection of these mutations is needed. METHODS: A total of 276 tumour samples from 174 melanoma patients were investigated for BRAF mutations by pyrosequencing. Rare mutations were confirmed by capillary sequencing and compared with findings from COBAS test and immunohistochemistry using a novel BRAF antibody. Melanoma type, localisation, and survival were summarised. RESULTS: BRAF mutations were found in 43% of patients (124 tumours in 75 patients). Among those, 14 patients (18.7%) exhibited rare mutations. The V600EK601del and V600DK601del mutations have never been described before in melanoma. Furthermore, V600K, V600E2, and V600D, V600G, V600R, and L597S mutations were detected. Mutations were not detected by COBAS test in 7 out of these 14 patients and immunohistochemistry only reliably detected patients with the V600E2 and V600EK601del mutation. CONCLUSION: Accurate diagnosis of rare BRAF mutations is crucial. We show that pyrosequencing is accurate, highly sensitive, reliable, and time saving to detect rare BRAF mutations. Missing these rare variant mutations would exclude a subset of patients from available effective BRAF-targeting therapy.

Expression of oncogenic BARD1 isoforms affects colon cancer progression and correlates with clinical outcome.

BACKGROUND: Colon cancer predisposition is associated with mutations in BRCA1. BRCA1 protein stability depends on binding to BARD1. In different cancers, expression of differentially spliced BARD1 isoforms is correlated with poor prognosis and decreased patient survival. We therefore suspected a role of BARD1 isoforms in colon cancer. METHODS: We performed immunohistochemistry in 168 colorectal cancers, using four antibodies directed against differentially expressed regions of BARD1. We determined structure and relative expression of BARD1 mRNA isoforms in 40 tumour and paired normal peri-tumour tissues. BARD1 expression was correlated with clinical outcome. RESULTS: BARD1 isoforms were expressed in 98% of cases and not correlated with BRCA1. BARD1 mRNA isoforms were upregulated in all tumours as compared with paired normal peri-tumour tissues. Non-correlated expression and localisation of different epitopes suggested insignificant expression of full-length (FL) BARD1. Expression of N- and C-terminal epitopes correlated with increased survival, but expression of epitopes mapping to the middle of BARD1 correlated with decreased survival. Middle epitopes are present in oncogenic BARD1 isoforms, which have pro-proliferative functions. Correlated upregulation of only N- and C-terminal epitopes reflects the expression of isoforms BARD1δ and BARD1φ. CONCLUSION: Our results suggest that BARD1 isoforms, but not FL BARD1, are expressed in colon cancer and affect its progression and clinical outcome.

hMLH1 promoter hypermethylation and MSI status in human endometrial carcinomas with and without metastases.

We investigated the methylation status of mismatch repair gene hMLH1 in 80 primary human endometrial carcinomas (ECs) and in 30 metastatic lesions. It was correlated to the expression of hMLH1 protein, microsatellite instability (MSI) of ECs and to the well-known clinico-pathological variables of cancer. The hMLH1 promoter methylation was detected in 24 out of 64 (37.5 %) primary ECs but only in one out of 18 (5.6 %) metastatic lesions investigated. Promoter hMLH1 hypermethylation was found more often in early stage ECs and was associated with a decrease of hMLH1 protein expression immunohistochemically. An inverse relationship between hMLH1 expression and clinical stage of the disease was found (p = 0.048). Interestingly, there was a significant correlation between MSI and hMLH1 protein expression level (p = 0.042). MSI phenotype was found more often in EC metastases compared to the primary tumors (66.7 % vs 29.3 %; p = 0.039). However, neither hMLH1 promoter hypermethylation nor MSI was independent predictive factors for patient's outcome. Using an in vitro model we showed that hMLH1 methylation is reversible. These data showed that hMLH1 methylation with a consequent protein decrease occurred early during EC tumorigenesis and may cause a MSI phenotype, which occurs relatively late. MSI may be an important mechanism supporting further the tumor progression. These findings may have importance for the specific chemosensitization of the primary tumors/metastases and can improve our understanding of endometrial carcinogenesis in humans.

P53-dependent antiproliferative and pro-apoptotic effects of trichostatin A (TSA) in glioblastoma cells.

Glioblastomas are known to be highly chemoresistant, but HDAC inhibitors (HDACi) have been shown to be of therapeutic relevance for this aggressive tumor type. We treated U87 glioblastoma cells with trichostatin A (TSA) to define potential epigenetic targets for HDACi-mediated antitumor effects. Using a cDNA array analysis covering 96 cell cycle genes, cyclin-dependent kinase inhibitor p21(WAF1) was identified as the major player in TSA-induced cell cycle arrest. TSA slightly inhibited proliferation and viability of U87 cells, cumulating in a G1/S cell cycle arrest. This effect was accompanied by a significant up-regulation of p53 and its transcriptional target p21(WAF1) and by down-regulation of key G1/S regulators, such as cdk4, cdk6, and cyclin D1. Nevertheless, TSA did not induce apoptosis in U87 cells. As expected, TSA promoted the accumulation of total acetylated histones H3 and H4 and a decrease in endogenous HDAC activity. Characterizing the chromatin modulation around the p21(WAF1) promoter after TSA treatment using chromatin immunoprecipitation, we found (1) a release of HDAC1, (2) an increase of acetylated H4 binding, and (3) enhanced recruitment of p53. p53-depleted U87 cells showed an abrogation of the G1/S arrest and re-entered the cell cycle. Immunofluorescence staining revealed that TSA induced the nuclear translocation of p21(WAF1) verifying a cell cycle arrest. On the other hand, a significant portion of p21(WAF1) was present in the cytoplasmic compartment causing apoptosis resistance. Furthermore, TSA-treated p53-mutant cell line U138 failed to show an induction in p21(WAF1), showed a deficient G2/M checkpoint, and underwent mitotic catastrophe. We suggest that HDAC inhibition in combination with other clinically used drugs may be considered an effective strategy to overcome chemoresistance in glioblastoma cells.

[Gastrointestinal stromal tumors: evolution of a tumor concept from unclassifiable neoplasms to targeted molecular therapy]. / Gastrointestinale Stromatumoren : Evolution eines Tumorkonzepts von unklassifizierbaren Neoplasien zur zielgerichteten molekularen Therapie.

The discovery of activating oncogenic C-KIT and PDGFRA mutations in gastrointestinal stromal tumors (GIST) represented the key for the development of innovative targeted molecular therapy using the tyrosine kinase inhibitors (TKI) Imatinib (Glivec(R)), Sunitinib and other substances. This makes a precise histopathological diagnosis a major prerequisite, supplemented by appropriate risk stratification for the assessment of the expected biological behavior of individual tumors. Current knowledge demonstrates that the presence of kinase mutations in C-KIT and PDGFRA and their localization within the gene sequence as well as the mutation type are of great importance for planning appropriate treatment (drug selection and dose recommendation), but also for the assessment of prognosis and explanation of secondary resistance to TKI after initial response. This article gives an overview on current developments in the histopathological and molecular diagnostics of GIST and the role of kinase mutation analysis for optimizing patient treatment.

Serous oligocystic adenoma (SOIA) of the pancreas--first reported case of a genetically fixed association in a patient with hereditary non-polyposis colorectal cancer (HNPCC).

Cystic tumor lesions of the pancreas are relatively uncommon. Advances in imaging and pathohistology, including immunohistochemistry, have led to the detection and classification of novel tumor entities. A promoting aspect is the extended indication profile in pancreatic surgery, in particular, because of lower perioperative morbidity and mortality. One of these classified cystic neoplasms of the pancreas is serous oligocystic adenoma (SOIA), a rare and benign tumor lesion. We report on a 41-year-old man with a cystic lesion within the pancreatic head. Therefore, he underwent pylorus-preserving cephal duodenopancreatectomy. Pathohistologic investigation revealed a SOIA. He had a medical history significant for subtotal colectomy because of a synchronous double colonic carcinoma. Both tumor tissue specimens had been characterized for a high level of microsatellite instability (MSI) and loss of hMLH1, as well as for a corresponding germ line mutation in hMLH1 gene, leading to the diagnosis of hereditary non-polyposis associated colon cancer (HNPCC). The case is remarkable since the SOIA revealed MSI and loss of hMLH1 protein in the tumor cells that has never been reported for this tumor type. In addition, there is a rare and extraordinary association between SOIA and HNPCC, which has never been published before, since SOIA, in this case, could have been developed in the setting of HNPCC syndrome.

DNA hypermethylation regulates the expression of members of the Mu-class glutathione S-transferases and glutathione peroxidases in Barrett's adenocarcinoma.

BACKGROUND: The accumulation of reactive oxygen species and subsequent oxidative DNA damage underlie the development of Barrett's oesophagus (BO) and its progression to Barrett's dysplasia (BD) and adenocarcinoma (BAC). METHODS: The promoter regions of 23 genes of the glutathione S-transferase (GST) and glutathione peroxidase (GPX) families were systematically analysed. Quantitative bisulfite pyrosequencing, real-time RT-PCR, western blot and immunohistochemical (IHC) analysis methods were utilised in this study. RESULTS: 14 genes were identified that have CpG islands around their transcription start sites: GSTs (GSTM2-M5, GSTA4, GSTP1, GSTZ1, GSTT2, GSTO1 and GSTO2) and GPXs (GPX1, GPX3, GPX4 and GPX7). Analysis of an initial set of 20 primary samples demonstrated promoter DNA hypermethylation and mRNA downregulation of GPX3, GPX7, GSTM2, GSTM3 and GSTM5 in more than half of the BAC samples. Further analysis of 159 primary human samples (37 normal, 11 BO, 11 BD and 100 BACs) indicated frequent hypermethylation (>or=10% methylation) of GPX3 (62%), GPX7 (67%), GSTM2 (69.1%) and GSTM3 (15%) in BACs. A significant inverse correlation between DNA methylation and mRNA expression level was shown for GPX3 (p<0.001), GPX7 (p = 0.002), GSTM2 (p<0.001) and GSTM5 (p = 0.01). Treatment of oesophageal cancer cell lines with 5-aza-2'-deoxycytidine and trichostatin-A led to reversal of the methylation pattern and re-expression of these genes at the mRNA and protein levels. The IHC analysis of GPX3, GPX7 and GSTM2 on a tissue microarray that contained 75 BACs with normal squamous oesophageal samples demonstrated an absent to weak staining in tumours (52% for GPX3, 57% for GPX7 and 45% for GSTM2) and a moderate to strong immunostaining in normal samples. CONCLUSION: Epigenetic inactivation of members of the glutathione pathway can be an important mechanism in Barrett's tumourigenesis.

Oxidative stress in ulcerative colitis-associated carcinogenesis.

Oxidative stress is defined as an imbalance between generation of reactive oxygen species (ROS) and decreased antioxidant defense systems. Oxidative stress develops particularly in inflammatory reactions because the inflammatory cells, neutrophils, and macrophages produce large amounts of ROS. It has been known for a long time that oxidative stress in inflamed tissue can pave the way for malignant tumors, and that it is a major pathogenetic factor for the well-established correlation between inflammatory diseases and cancer. Oxidative stress has long been associated with the pathogenesis of chronic inflammatory bowel disease (IBD)-related colorectal cancer. This article provides an overview of the pathology of ROS and presents recent advances concerning the role of ROS in IBD-related colorectal carcinogenesis (Fig. 1).

Trichostatin A causes p53 to switch oxidative-damaged colorectal cancer cells from cell cycle arrest into apoptosis.

Many studies aim at improving therapeutic efficacy by combining strategies with oxidative stress-inducing drugs and histone deacetylase (HDAC) inhibitors in colorectal cancer. As p53 and p21(WAF1) are essential in oxidative stress-induced DNA damage, we investigated epigenetic regulation of p21(WAF1) promoter. Firstly, HCT116 p53(+)/(+) and p53(-)/(-) colorectal cancer cells were treated with H(2)O(2) for 6 hrs and 24 hrs (early/late response). Chromatin immunoprecipitation revealed transcriptional transactivation of p21(WAF1) in HCT116 p53(+)/(+) cells as shown by increased binding of p53 and acetylated H4 around two p21(WAF1) promoter sites, the responsible element (RE) and the Sp1 site, while both proteins bound preferentially on the RE. Interestingly, H3 was not involved, suggesting H4-specific transactivation of the p21(WAF1) promoter. H(2)O(2) addition resulted in G(2)/M arrest of both HCT116 cell lines without significant cell death. To investigate whether a HDAC inhibitor strengthens G(2)/M arrest, we pretreated cells with Trichostatin A (TSA). In HCT116 p53(+)/(+) cells, we found (i) remarkably increased acetylated H4 around both p21(WAF1) promoter regions, especially at the Sp1 site; (ii) increased acetylation of p53 at lysines 320 and 382;(iii) displacement of HDAC1 from the Sp1 site, thus inhibiting its repression effect and increasing p53 binding.p53 seems to trigger H4-acetylation around the p21(WAF1) promoter because there was nearly no H4 acetylation in HCT116 p53(-)/(-) cells. For the first time we show that there is a time-dependent TSA mode of action with increased p53-dependent histone H4 acetylation at the p21(WAF1) promoter in early response, and decreased acetylation in late response. Reduced p53-triggered transactivation of p21(WAF1) in late response allows cells to re-enter cell cycle, and TSA causes p53 to simultaneously induce apoptosis.

Modulation by polyamines of apoptotic pathways triggered by procyanidins in human metastatic SW620 cells.

We showed previously that inhibition of polyamine catabolism with the polyamine oxidase inhibitor MDL 72527 (MDL) potentiates the apoptotic effects of apple procyanidins (Pcy) in SW620 cells. Here we report that Pcy caused an activation of the intrinsic apoptotic pathway through enhanced polyamine catabolism and mitochondrial membrane depolarization. MDL in the presence of Pcy caused a profound intracellular depletion of polyamines and exerted a protective effect on mitochondrial functions. MDL potentiation of Pcy-triggered apoptosis was reversed by addition of exogenous polyamines. In addition, MDL in combination with Pcy activated the extrinsic apoptotic pathway through enhanced TRAIL-death receptor (DR4/DR5) expression. Potentiation of Pcy-triggered apoptosis by MDL was inhibited when cells were exposed to specific inhibitors of DR4/DR5. These data indicate that the depletion of intracellular polyamines by MDL in the presence of Pcy caused a switch from intrinsic to extrinsic apoptotic pathways in human colon cancer-derived metastatic cells.

Close localization of DAP-kinase positive tumour-associated macrophages and apoptotic colorectal cancer cells.

The death-associated protein kinase (DAP-kinase) is a cytoskeleton-associated protein crucially involved in the induction of early apoptotic pathways. Aberrant hypermethylation of the DAP-kinase promoter plays a major role in tumorigenesis. We aimed to investigate the inactivation of DAP-kinase and its association with apoptotic cell death in 94 colorectal carcinomas. DAP-kinase promoter hypermethylation and mRNA expression were investigated using methylation-specific PCR and real-time RT-PCR, respectively. The expression of DAP-kinase, Fas, and Fas-ligand (FasL) proteins was studied by immunohistochemistry and immunofluorescence. Apoptosis of tumour cells was investigated using the TUNEL assay. DAP-kinase was expressed in tumour cells and tumour-invading macrophages and was closely associated with high numbers of apoptotic tumour cells. DAP-kinase expression co-localized with FasL overexpression in tumour-associated macrophages, and aberrant promoter hypermethylation was verified in more than 50% of carcinomas. There was a tendency for proximal tumours to show DAP-kinase promoter methylation more frequently (p = 0.07). Promoter methylation resulted in a decrease or loss of DAP-kinase protein expression in tumour cells and tumour-associated macrophages. Simultaneously, a decreased apoptotic count and loss of Fas/FasL expression was observed in tumour cells. Our study is the first to demonstrate DAP-kinase expression in invading tumour-associated macrophages in colorectal cancer. The presence of similar expression levels of DAP-kinase in tumour cells and associated macrophages, and their dependence on the promoter methylation status of the tumour cells, suggests cross talk between these cell types during apoptotic cell death.

Rb-loss is associated with high malignancy in chondrosarcoma.

Loss of function of the human retinoblastoma gene (Rb) is a frequent genetic abnormality in human malignancies and causes a disturbance in the cell cycle and loss of normal proliferation and differentiation. We studied the loss of heterozygosity (LOH) of the Rb gene in 31 formalin-fixed, paraffin-embedded cartilaginous tumors using polymerase chain reaction. The tumors were subdivided into 8 cases of dedifferentiated (DD) chondrosarcoma, 17 cases of conventional chondrosarcoma (nine grade 1, seven grade 2 and one grade 3), 4 enchondromas and 2 chondroblastomas. Both components of DD chondrosarcoma, the low-grade and anaplastic components, were separated by a microdissection approach. The genetic data were correlated with the expression of the Rb protein examined by Rb immunohistochemistry. We found Rb-LOH in one grade 3 chondrosarcoma, and in the anaplastic component in 7 of 8 cases of DD chondrosarcoma (89% of all high-grade chondrosarcomas). All tumors with Rb-LOH were immunohistochemically Rb-negative. The only case of DD chondrosarcoma negative for Rb-LOH in both components of the tumor also showed weak expression of the Rb protein in the anaplastic component. All benign cartilaginous tumors, low-grade chondrosarcomas and low-grade tumor components of DD chondrosarcomas were negative regarding Rb-LOH but positive in Rb immunohistostaining. We concluded that Rb-LOH predominantly occurs in high-grade chondrosarcomas. However, it is not a marker for identifying low-grade tumors with a tendency towards progression or local recurrence.

Molecular targets for tumour progression in gastrointestinal stromal tumours.

BACKGROUND AND AIMS: The distinction between benign and malignant gastrointestinal stromal tumours (GISTs) is often unclear at the clinical and histopathology levels. GISTs are believed to arise from the stem cells of Cajal. In order to define genetic biomarkers and identify target genes related to GIST progression, we analysed and compared benign and malignant GISTs with verified follow up data using cDNA expression arrays. METHODS: Eight genes were frequently overexpressed in malignant GISTs and their overexpression was confirmed using quantitative real time reverse transcription-polymerase chain reaction. These genes included ezrin (villin 2 (VIL2)), collagen 8 alpha 1 subunit (COL8A1), G2/mitotic specific cyclin B1 (CCNB1), high mobility group protein (HMG2), TSG101 tumour susceptibility protein, CENP-F kinetochore protein, protein tyrosine kinase 2 (FAK), and protein kinase DYRK2. To test these genes in a clinical setting, we obtained diagnostic samples of 16 additional GISTs that were classified at diagnosis as benign, malignant, and uncertain malignant potential (UMP). RESULTS: There was remarkable gene overexpression in all malignant GISTs. Statistical analyses revealed significant correlations between overexpression of several gene pairs in malignant GISTs. We found the strongest correlations (rho>0.70) among the significant correlations (p<0.01) between CCNB1-CENP-F (rho = 0.87) and CCNB1-FAK (rho = 0.73). Gene expression of the UMP GISTs suggested two different groups. Three UMP GISTs had gene expression consistent with malignant tumours and their follow up data revealed that indeed these patients had recurrences later on. On the other hand, UMP GISTs that had low gene expression levels continued free of disease for several years. CONCLUSIONS: These results provide insight into the oncogenesis of GISTs and suggest that testing the expression profile of a number of genes may segregate GISTs into groups of different tumour behaviour.

[Biallelic inactivation of the p16-Gen in a metachronous triple carcinoma in the oropharyngeal region]. / Biallelische Inaktivierung des p16-Gens bei metachronem Dreifachkarzinom im oropharyngealen Bereich.

AIMS: Recent studies have shown that most Dutch families with atypical multiple-mole melanoma (FAMMM) have a 19-bp deletion (p16-Leiden) in exon 2 of the p16 gene. Apart from reports on metachronous pancreatic tumors, other cancer types have never been described in such families. Due to heterozygous p16-Leiden constitution, our proband with multiple head and neck carcinomas was a suitable model for studying the type of p16 inactivation according to the Knudson-two-hit model. METHODS: p16 mutations in exons 1 and 2 were determined using PCR-SSCP-Sequencing analysis. p16 methylation was assessed by methylation-specific PCR. RESULTS: All three metachronous (larynx, pharynx, oral cavity) tumors had a methylated p16 promotor. The p16 protein loss detected by immunohistochemistry clearly confirmed a complete loss of p16 tumor suppressor function. Thus, all three tumors exhibited biallelic inactivation of p16, caused by aberrant methylation of the p16 promotor. CONCLUSIONS: This is the first report on p16-Leiden mutation in head and neck cancer. We provide evidence that the somatic methylation of p16 promotor is associated with the germline transmission of p16-Leiden mutation. This is an example for the rare event of in which aberrant methylation acting as the 'second hit' in a familial cancer syndrome. Our results show that this epigenetic event is equivalent to genetic alterations (mutation/LOH) confirming the Knudson's hypothesis for tumor suppressor gene inactivation.