EPHA4 is overexpressed but not functionally active in Sézary syndrome.

EPHA4 belongs to the largest subfamily of receptor tyrosine kinases. In addition to its function during development, overexpression of EPHA4 in tumors has been correlated with increased proliferation, migration and poor survival. Several genome-wide transcription profiling studies have demonstrated high EPHA4 expression in Sézary syndrome (SS), a leukemic variant of cutaneous CD4+ T-cell lymphoma (CTCL) with an aggressive clinical course and poor prognosis. In this study we set out to explore the functional role of EPHA4 in SS. Both high EPHA4 mRNA and protein expression was found in circulating SS-cells of patients compared to healthy CD4+ T-cells. However, using a phosphospecific EPHA4 antibody, phosphorylation of the EPHA4 kinase domain was not detected in either circulating or skin residing SS cells. Moreover, treatment with the phosphatase inhibitor pervanadate did not result in detectable phosphorylation of the EPHA4 kinase domain, in either SS cells or in healthy CD4+ T-cells. Thus, the results from our study confirm high EPHA4 expression in SS cells both on the mRNA and protein levels, making EPHA4 a good diagnostic marker. However, the overexpressed EPHA4 does not appear to be functionally active and its overexpression might be secondary to other oncogenic drivers in SS, like STAT3 and TWIST1.

Molecular profiling of cutaneous squamous cell carcinomas and actinic keratoses from organ transplant recipients.

BACKGROUND: The risk of developing cutaneous squamous cell carcinoma (SCC) is markedly increased in organ transplant recipients (OTRs) compared to the normal population. Next to sun exposure, the immunosuppressive regimen is an important risk factor for the development of SCC in OTRs. Various gene mutations (e.g. TP53) and genetic alterations (e.g. loss of CDKN2A, amplification of RAS) have been found in SCCs. The aim of this genome-wide study was to identify pathways and genomic alterations that are consistently involved in the formation of SCCs and their precursor lesions, actinic keratoses (AKs). METHODS: To perform the analysis in an isogenic background, RNA and DNA were isolated from SCC, AK and normal (unexposed) epidermis (NS) from each of 13 OTRs. Samples were subjected to genome-wide expression analysis and genome SNP analysis using Illumina's HumanWG-6 BeadChips and Infinium II HumanHap550 Genotyping BeadChips, respectively. mRNA expression results were verified by quantitative PCR. RESULTS: Hierarchical cluster analysis of mRNA expression profiles showed SCC, AK and NS samples to separate into three distinct groups. Several thousand genes were differentially expressed between epidermis, AK and SCC; most upregulated in SCCs were hyperproliferation related genes and stress markers, such as keratin 6 (KRT6), KRT16 and KRT17. Matching to oncogenic pathways revealed activation of downstream targets of RAS and cMYC in SCCs and of NFκB and TNF already in AKs. In contrast to what has been reported previously, genome-wide SNP analysis showed very few copy number variations in AKs and SCCs, and these variations had no apparent relationship with observed changes in mRNA expression profiles. CONCLUSION: Vast differences in gene expression profiles exist between SCC, AK and NS from immunosuppressed OTRs. Moreover, several pathways activated in SCCs were already activated in AKs, confirming the assumption that AKs are the precursor lesions of SCCs. Since the drastic changes in gene expression appeared unlinked to specific genomic gains or losses, the causal events driving SCC development require further investigation. Other molecular mechanisms, such as DNA methylation or miRNA alterations, may affect gene expression in SCCs of OTRs. Further study is required to identify the mechanisms of early activation of NFκB and TNF, and to establish whether these pathways offer a feasible target for preventive intervention among OTRs.

Fragment based lead discovery of small molecule inhibitors for the EPHA4 receptor tyrosine kinase.

The in silico identification, optimization and crystallographic characterization of a 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine scaffold as an inhibitor for the EPHA4 receptor tyrosine kinase is described. A database containing commercially available compounds was subjected to an in silico screening procedure which was focused on finding novel, EPHA4 hinge binding fragments. This resulted in the identification of 6,7,8,9-tetrahydro-3H-pyrazolo[3,4-c]isoquinolin-1-amine derivatives as EPHA4 inhibitors. Hit exploration yielded a compound with 2 µM (IC(50)) affinity for the EPHA4 receptor tyrosine kinase domain. Soaking experiments into a crystal of the EPHA4 kinase domain gave a 2.11Å X-ray structure of the EPHA4 - inhibitor complex, which confirmed the binding mode of the scaffold as proposed by the initial in silico work. The results underscore the strength of fragment based in silico screening as a tool for the discovery of novel lead compounds as small molecule kinase inhibitors.

Aberrant heparan sulfate proteoglycan localization, despite normal exostosin, in central chondrosarcoma.

The tumor suppressor genes EXT1 and EXT2 are involved in the formation of multiple osteochondromas, which can progress to become secondary peripheral chondrosarcomas. The most common chondrosarcoma subtype is primary central chondrosarcoma, which occurs in the medullar cavity of bone. The EXT1/EXT2 protein complex is involved in heparan sulfate proteoglycan (HSPG) biosynthesis, which is important for signal transduction of Indian hedgehog (IHH), WNT, and transforming growth factor (TGF)-beta. The role of EXT and its downstream targets in central chondrosarcomas is currently unknown. EXT1 and EXT2 were therefore evaluated in central chondrosarcomas at both the DNA and mRNA levels. Immunohistochemistry was used to assess HSPG (CD44v3 and SDC2), WNT (beta-catenin), and TGF-beta (PAI-1 and phosphorylated Smad2) signaling, whereas IHH signaling was studied both by quantitative polymerase chain reaction and in vitro. mRNA levels of both EXT1 and EXT2 were normal in central chondrosarcomas; genomic alterations were absent in these regions and in 30 other HSPG-related genes. Although HSPGs were aberrantly located (CD44v3 in the Golgi and SDC2 in cytoplasm and nucleus), this was not caused by mutation. WNT signaling negatively correlated with increasing histological grade, whereas TGF-beta positively correlated with increasing histological grade. IHH signaling was active, and inhibition decreased cell viability in one of six cell lines. Our data suggest that, despite normal EXT in central chondrosarcomas, HSPGs and HSPG-dependent signaling are affected in both central and peripheral chondrosarcomas.

The role of noncartilage-specific molecules in differentiation of cartilaginous tumors: lessons from chondroblastoma and chondromyxoid fibroma.

BACKGROUND: Chondroblastoma (CB) and chondromyxoid fibroma (CMF) are benign tumors of bone morphologically recapitulating cartilage differentiation. CMF can resemble high-grade central chondrosarcoma (HGCCS) because of its cellular atypia. The mechanism that drives this morphologic spectrum of cartilage differentiation is unclear. METHODS: CMFs and CBs were hybridized on a complementary DNA microarray that was enriched for cartilage-specific genes. Data were analyzed by Linear Model for Microarray Analysis and were compared with previous data on osteochondromas and HGCCS. Verification was performed in an extended series. RESULTS: None of the 68 genes that were differentially expressed in CB versus CMF, including several extracellular matrix (ECM) and ECM-degradation genes, were related specifically to cartilage. Perlecan, versican, collagen 4A2 (Col4A2), and cell-cell adhesion genes, such as CD166, were significantly higher in CMF. Sixty genes were expressed differentially in CMF versus HGCCS. Higher expression levels of CD166, cyclin D1 (CCND1), and p16INK4A were observed in CMF. CONCLUSIONS: The current findings indicated that differential expression of adhesion and ECM molecules, such as CD166, versican, perlecan, and Col4A2, may interfere with cartilaginous differentiation. The decreased expression of CCND1, p16INK4A, and CD166 in HGCCS reflects impairment of cell cycle progression and of cell-cell adhesions in malignant tumors and is of use in the differential diagnosis of CMF.

The role of EXT1 in nonhereditary osteochondroma: identification of homozygous deletions.

BACKGROUND: Multiple osteochondromas is a hereditary syndrome that is characterized by the formation of cartilage-capped bony neoplasms (osteochondromas), for which exostosis (multiple)-1 (EXT1) has been identified as a causative gene. However, 85% of all osteochondromas present as solitary (nonhereditary) lesions in which somatic mutations in EXT1 are extremely rare, but loss of heterozygosity and clonal rearrangement of 8q24 (the chromosomal locus of EXT1) are common. We examined whether EXT1 might act as a classical tumor suppressor gene for nonhereditary osteochondromas. METHODS: Eight nonhereditary osteochondromas were subjected to high-resolution array-based comparative genomic hybridization (array-CGH) analysis for chromosome 8q. The array-CGH results were validated by subjecting tumor DNA to multiple ligation-dependent probe amplification (MLPA) analysis for EXT1. EXT1 locus-specific fluorescent in situ hybridization (FISH) was performed on nuclei isolated from the three tissue components of osteochondroma (cartilage cap, perichondrium, bony stalk) to examine which parts of the tumor are of clonal origin. RESULTS: Array-CGH analysis of tumor DNA revealed that all eight osteochondromas had a large deletion of 8q; five tumors had an additional small deletion of the other allele of 8q that contained the EXT1 gene. MLPA analysis of tumor DNA confirmed these findings and identified two additional deletions that were smaller than the limit of resolution of array-CGH. FISH analysis of the cartilage cap, perichondrium, and bony stalk showed that these homozygous EXT1 deletions were present only in the cartilage cap of osteochondroma. CONCLUSION: EXT1 functions as a classical tumor suppressor gene in the cartilage cap of nonhereditary osteochondromas.

cDNA expression profiling of chondrosarcomas: Ollier disease resembles solitary tumours and alteration in genes coding for components of energy metabolism occurs with increasing grade.

Conventional central chondrosarcomas are malignant cartilaginous tumours, occasionally arising secondary to either solitary or multiple (Ollier disease) enchondromas. Recurrences may have progressed in grade. The aims of the present study were to identify putative differences in gene expression between solitary and Ollier disease-related tumours, and to elucidate signalling pathways involved in tumour progression by genome-wide cDNA expression analysis. Arrays enriched for cartilage-specific cDNAs and genes involved in general tumourigenesis were used to analyse enchondromas (n = 3, two with Ollier disease), chondrosarcomas of different grades (n = 19, three with Ollier disease), normal resting-zone cartilage (n = 2), and chondrosarcoma cells in culture (n = 7). The arrays were analysed by unsupervised hierarchical clustering, significant analysis of microarray, and T-tests. Confirmation of data was performed by immunohistochemistry and quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Ollier disease cases and solitary tumours revealed similar expression profiles, suggesting that the same signalling pathways are involved in tumourigenesis. Interestingly, JunB protein expression was significantly higher in grade I chondrosarcomas than in enchondromas (p = 0.009), which could be of diagnostic relevance. Upon chondrosarcoma progression, matrix-associated genes are down-regulated, reflecting the histology of high-grade tumours. An increase in glycolysis-associated, and a decrease in oxidative phosphorylation-related, genes was found in high-grade tumours. These findings suggest an adaptation in energy supply upon progression towards higher grade.

The use of Bcl-2 and PTHLH immunohistochemistry in the diagnosis of peripheral chondrosarcoma in a clinicopathological setting.

Distinguishing osteochondroma from low-grade secondary peripheral chondrosarcoma can be difficult. In osteochondroma, growth-signalling pathways are thought to be downregulated through exostosin (EXT) inactivation. A previous pilot study focusing on expression of putative EXT downstream effectors indicated that progression of osteochondroma towards grade I chondrosarcoma was characterised by upregulation of Bcl-2 and parathyroid hormone-like hormone (PTHLH). We investigated their use as diagnostic markers in a large nationwide series of 71 osteochondromas and 34 chondrosarcomas. Bcl-2 immunohistochemistry proved to be a valuable diagnostic tool: scoring negative in 95% (specificity) of the osteochondromas and positive in 57% (sensitivity) of the chondrosarcomas, reaching a positive predictive value of 84% and negative predictive value of 82%. Positivity was not related to age, hereditary status, gender or thickness of the cartilage cap. Presence of internal controls and verification using mRNA in situ hybridisation strengthened the reliability of the immunohistochemical staining. PTHLH showed more variable staining, being positive in osteochondromas from females or adolescent males, suggesting age- and gender-dependent expression. Thus, in cases where the distinction between osteochondroma and chondrosarcoma is difficult, Bcl-2 is a valuable diagnostic marker for malignancy, regardless of tumour size, patient gender or age, and this can be extended with PTHLH for non-adolescent male patients.

Absence of IHH and retention of PTHrP signalling in enchondromas and central chondrosarcomas.

Enchondromas and conventional central chondrosarcomas are, respectively, benign and malignant hyaline cartilage-forming tumours that originate in the medulla of bone. In order to gain a better understanding of the molecular process underlying malignant transformation of enchondroma, and to investigate whether there is a biological difference between conventional central cartilaginous tumours and those of enchondromatosis or with phalangeal localization, a series of 64 enchondromas (phalanx, n = 21; enchondromatosis, n = 15) and 89 chondrosarcomas (phalanx, n = 17; enchondromatosis, n = 13) was collected. Indian Hedgehog (IHH)/parathyroid hormone related peptide (PTHrP) signalling, an important pathway in chondrocyte proliferation and differentiation within the normal growth plate, was studied by immunohistochemical analysis of the expression of PTHrP, PTHR1, Bcl-2, p21, cyclin D1, and cyclin E. Quantitative real-time PCR for IHH, PTCH, SMO, and GLI2 was performed on a subset of tumours. The data show that IHH signalling is absent in enchondromas and central chondrosarcomas, while PTHrP signalling is active. There was no difference in the expression of any of the molecules between 35 enchondromas and 26 grade I central chondrosarcomas, indicating that PTHrP signalling is not important in malignant transformation of enchondroma. Higher expression of PTHR1 and Bcl-2 was associated with increasing histological grade in chondrosarcoma, suggesting involvement in tumour progression. No difference was found between samples from enchondromatosis patients and solitary cases, suggesting no difference in PTHrP signalling. A small subset of phalangeal chondrosarcomas demonstrated down-regulation of PTHrP, which may be related to its more indolent clinical behaviour. Thus, in both enchondromas and central chondrosarcomas, PTHrP signalling is active and independent of IHH signalling, irrespective of the presence or absence of enchondromatosis.

Multiple osteochondromas: clinicopathological and genetic spectrum and suggestions for clinical management.

Multiple Osteochondromas is an autosomal dominant disorder characterised by the presence of multiple osteochondromas and a variety of orthopaedic deformities. Two genes causative of Multiple Osteochondromas, Exostosin-1 (EXT1) and Exostosin-2 (EXT2), have been identified, which act as tumour suppressor genes. Osteochondroma can progress towards its malignant counterpart, secondary peripheral chondrosarcoma and therefore adequate follow-up of Multiple Osteochondroma patients is important in order to detect malignant transformation early.This review summarizes the considerable recent basic scientific and clinical understanding resulting in a multi-step genetic model for peripheral cartilaginous tumorigenesis. This enabled us to suggest guidelines for clinical management of Multiple Osteochondroma patients. When a patient is suspected to have Multiple Osteochondroma, the radiologic documentation, histology and patient history have to be carefully reviewed, preferably by experts and if indicated for Multiple Osteochondromas, peripheral blood of the patient can be screened for germline mutations in either EXT1 or EXT2. After the Multiple Osteochondroma diagnosis is established and all tumours are identified, a regular follow-up including plain radiographs and base-line bone scan are recommended.

Inhibition of glutathione S-transferase in rat hepatocytes by a glycine-tetrazole modified S-alkyl-GSH analogue.

Glutathione (GSH) conjugates inhibit enzymes that are involved in drug metabolism and drug resistance, but their cellular uptake is very low. To improve membrane-permeability, we synthesized a novel GSH-conjugate analogue with a tetrazole carboxylate isostere at the glycine position. Introduction of the tetrazole decreases inhibitory potency towards CDNB conjugation by glutathione S-transferase. However, the tetrazole derivative inhibited 2-bromoisovalerylurea conjugation in rat liver cytosol, as well as in hepatocytes.