Anja K. Bosserhoff

Expression of Dickkopf genes is strongly reduced in malignant melanoma

The Dickkopf (DKK) genes were originally identified as factors inducing head formation in Xenopus. The genes code for inhibitors that are involved in Wnt signaling. We speculate that loss of DKK expression plays a role in development or progression of malignant melanoma. Thus, we evaluated melanoma cell lines and tissue samples of malignant melanoma for loss of DKK, especially DKK-3 transcription. We found that DKK-1, -2 and -3 were downregulated or lost in all cell lines and in most of the tumor samples analysed. Reduced DKK-3 expression occurred as early as in primary tumors detected by both immunohistochemical and reverse transcription–polymerase chain reaction RT–PCR analysis. Functional assays with stable DKK-3 transfected cell lines revealed that DKK-3 expression increased cell-cell adhesion and decreased cell migration. Further, downregulation of fibronectin, snail-1 and re-expression of E-cadherin was found in the DKK-3 expressing cell clones supporting a role of DKK-3 in tumor progression. Our studies thus indicate that loss of DKK-3 expression may contribute to melanoma progression.

miRNA Expression Profiling in Melanocytes and Melanoma Cell Lines Reveals miRNAs Associated with Formation and Progression of Malignant Melanoma

Although deregulated expression of microRNAs (miRNAs) demonstrably contributes to the development and progression of all types of human cancers, little data are available about the changes in miRNA expression levels in malignant melanoma. In our study, we performed microarray-based miRNA profiling of melanocytes and melanoma cell lines derived from either primary tumors or metastatic melanomas. In addition, we analyzed miRNA expression patterns of melanoma cell clones in which the expression of melanoma specific genes was stably knocked down by antisense techniques. We also generated miRNA expression profiles for two derivatives of a melanoma cell line that differ in their invasive potential. Comparing miRNA expression patterns of melanocytes and subsets of melanoma cell lines, we identified large cohorts of miRNAs associated with malignant transformation as well as with the progression of the disease and with metastatic colonization. Surprisingly, the bulk of miRNAs that deregulated most strongly was not described to be of importance in tumor development before. The results of our study, therefore, not only provide insights into alterations in the miRnomes of melanocytes and melanoma cell lines during melanoma progression but also present a large assortment of miRNAs to be analyzed for their potential as diagnostic markers or targets for therapies in the future.

A novel MCP-1 gene polymorphism is associated with hepatic MCP-1 expression and severity of HCV-related liver disease.

BACKGROUND AND AIMS Factors influencing the progression of chronic hepatitis C virus (HCV) infection are poorly understood. Monocyte chemotactic protein-1 (MCP-1) is a potent chemokine, and its hepatic expression is up-regulated during chronic HCV infection mainly in activated hepatic stellate cells (HSC). In this study, we investigated the correlation of the functional -2518 MCP-1 promoter polymorphism with hepatic MCP-1 expression and the disease outcome in patients with HCV. METHODS MCP-1 genotyping was performed in 206 patients and 139 healthy controls. Hepatic MCP-1 messenger RNA (mRNA) expression was quantified by real-time PCR in 58 HCV patients. Cytokine-induced MCP-1 secretion of activated human HSC (n = 13) was determined by enzyme-linked immunosorbent assay (ELISA). Mobility-shift assays were performed using probes corresponding to the MCP-1 promoter sequence (-2511 to -2528) with or without the A to G mutation at -2518. RESULTS Frequency of MCP-1 genotypes did not differ between HCV patients and controls. However, carriers of the G allele were significantly more frequent in HCV patients with more advanced fibrosis and severe inflammation. In accordance, hepatic MCP-1 mRNA levels were significantly higher in patients with more advanced fibrosis and in patients carrying the G allele. Furthermore, cytokine-induced MCP-1 secretion of HSC isolated from carriers of the G allele was significantly higher, and there was binding activity in nuclear extracts from activated HSC specifically to the G allele, providing a potential mechanism for the differences seen. CONCLUSIONS Inheritance of the -2518 MCP-1 G allele, which appears to affect hepatic MCP-1 expression, may predispose HCV patients to more severe hepatic inflammation and fibrosis.

Down-regulation of CYLD expression by Snail promotes tumor progression in malignant melanoma

High malignancy and early metastasis are hallmarks of melanoma. Here, we report that the transcription factor Snail1 inhibits expression of the tumor suppressor CYLD in melanoma. As a direct consequence of CYLD repression, the protooncogene BCL-3 translocates into the nucleus and activates Cyclin D1 and N-cadherin promoters, resulting in proliferation and invasion of melanoma cells. Rescue of CYLD expression in melanoma cells reduced proliferation and invasion in vitro and tumor growth and metastasis in vivo. Analysis of a tissue microarray with primary melanomas from patients revealed an inverse correlation of Snail1 induction and loss of CYLD expression. Importantly, tumor thickness and progression-free and overall survival inversely correlated with CYLD expression. Our data suggest that Snail1-mediated suppression of CYLD plays a key role in melanoma malignancy.

Functional implication of BMP4 expression on angiogenesis in malignant melanoma

Analyses of malignant melanomas revealed a strong expression of bone morphogenic proteins (BMPs) and their autocrine effect in promoting cell invasion and migration. Here, we report a paracrine effect of BMPs on the vascular network. Both BMP2 and BMP4 induced tube formation as well as the migratory efficiency of microvascular endothelial cells. Melanoma cells with reduced BMP activity attracted less endothelial cells in invasion assays than control cells. Furthermore, reduction of BMPs in melanoma cells had a strong effect on vasculogenic mimicry. Tube formation on matrigel was analysed for melanoma cells as well as in co-cultures of endothelial and melanoma cells. Melanoma cells with reduced BMP activity were not capable of forming cord-like structures by themselves and additionally inhibited tube formation of the endothelial cells. Genes involved in angiogenesis turned out to be strongly downregulated in these cell clones. Tumors derived from cells with impaired BMP activity showed reduced tumor growth or large necrotic areas owing to lack of angiogenesis in in vivo analyses.

Systematic search for gastric cancer-specific genes based on SAGE data: melanoma inhibitory activity and matrix metalloproteinase-10 are novel prognostic factors in patients with gastric cancer

Gastric cancer (GC) is one of the most common malignancies worldwide. Genes expressed only in cancer tissue will be useful molecular markers for diagnosis and may also be good therapeutic targets. However, little is known about cancer-specific genes, at least in GC. In this study, we searched for GC-specific genes by serial analysis of gene expression (SAGE) data analysis and quantitative reverse transcription (RT)–PCR. Comparing GC SAGE libraries with those of various normal tissues in the SAGEmap database, we identified 54 candidate GC-specific genes. Quantitative RT–PCR analysis of these candidates revealed that APin protein (APIN), taxol resistance-associated gene 3 (TRAG3), cytochrome P450, family 2, subfamily W, polypeptide 1 (CYP2W1), melanoma inhibitory activity (MIA), matrix metalloproteinase-10 (MMP-10), dickkopf homolog 4 (DKK4), GW112, regenerating islet-derived family, member 4 (REGIV), and HORMA domain-containing 1 (HORMAD1) were expressed much more highly in GC than in 14 kinds of normal tissues. Immunohistochemical staining for MIA, MMP-10, and DKK4 was found in 47 (31.1%), 68 (45.0%), and two (1.3%) of 151 GCs, respectively, and staining for both MIA and MMP-10 was correlated with poor prognosis in advanced GC (P=0.0001 and 0.0141, respectively). Moreover, enzyme-linked immunosorbent assay showed high levels of MMP-10 (65/69, 94.2%) in serum samples from patients with GC. Levels of MIA were raised in a small proportion of serum samples from patients with GC (4/69, 5.8%). In Boyden chamber invasion assays, MIA-transfected GC cells were up to three times more invasive than cells transfected with empty vector. Taken together, these results suggest that MMP-10 is a good marker for the detection of GC and that MIA and MMP-10 are prognostic factors for GC. As expression of MIA and MMP-10 is narrowly restricted in cancer, these two molecules may be good therapeutic targets for GC.

Reduced expression of Hugl-1, the human homologue of Drosophila tumour suppressor gene lgl, contributes to progression of colorectal cancer.

The human gene, human giant larvae (Hugl-1/Llg1/Lgl1) has significant homology to the Drosophila tumour suppressor gene lethal(2)giant larvae (lgl). The lgl gene codes for a cortical cytoskeleton protein, Lgl, that binds Myosin II and is involved in maintaining cell polarity and epithelial integrity. The human protein, Hugl-1 contains several conserved functional domains found in Lgl, suggesting that these proteins may have closely related functions. Whether loss of Hugl expression plays a role in human tumorigenesis has so far not been extensively investigated. Thus, we evaluated tumour tissues from 94 patients undergoing surgery for colorectal cancer (CRC) for loss of Hugl-1 transcription and compared our findings with the clinical data from each of these patients. We found that Hugl-1 was lost in 75% of tumour samples and these losses were associated with advanced stage and particularly with lymph node metastases. Reduced Hugl-1 expression during the adenoma-carcinoma sequence occurring as early as in colorectal adenomas was detected by both immunohistochemical and reverse transcription–polymerase chain reaction analysis. Functional assays with ecdysone-inducible cell lines revealed that Hugl-1 expression increased cell adhesion and decreased cell migration. Our studies thus indicate that downregulation of Hugl-1 contributes to CRC progression.

Upregulation of HMG1 leads to melanoma inhibitory activity expression in malignant melanoma cells and contributes to their malignancy phenotype

ABSTRACT Malignant transformation of melanocytes to melanoma cells closely parallels activation of melanoma inhibitory activity (MIA) expression. We have previously shown that upregulation of MIA occurs on a transcriptional level and involves the highly conserved region (HCR) promoter element. We further observed that the HCR element interacts with the melanoma-associated transcription factor (MATF) and thereby confers strong promoter activation. In this study we identify the peptide sequence of MATF and show that it is identical with the transcription factor HMG1. HMG1 was upregulated in malignant melanoma cells and further activated by hypophosphorylation. Stable antisense-HMG1 expression in melanoma cells led to the reduction of MIA promoter activity and protein expression, indicating that HMG1 is a potent regulator of MIA expression. Interestingly, chromatin immunoprecipitation and electrophoretic mobility shift experiments indicated that HMG1 and the NF-κB family member p65 both interact and bind to the HCR promoter element. In summary, our study proves HMG1 and p65 to be important factors in MIA regulation and melanoma progression.

MOUSE CD-RAP/MIA GENE : STRUCTURE, CHROMOSOMAL LOCALIZATION, AND EXPRESSION IN CARTILAGE AND CHONDROSARCOMA

A cDNA encoding a novel protein has been previously isolated from two independent sources: melanoma cell cultures and chondrocytes. The protein from human melanoma cell lines and tumors is called melanoma inhibitory activity (MIA) (Blesch et al. [1994] Cancer Res. 54:5695–5701) and the protein from primary bovine chondrocytes and cartilaginous tissues is called cartilage‐derived retinoic acid‐sensitive protein (CD‐RAP) (Dietz and Sandell [1996] J. Biol. Chem. 271:3311–3316). In order to investigate the gene regulation and function of CD‐RAP/MIA, the mouse gene locus was isolated and analyzed. Developmental expression was determined by in situ hybridization to mouse embryos. Expression was limited to cartilaginous tissues and was initiated with the advent of chondrogenesis, remaining abundant throughout development. The mouse gene was isolated and sequenced from a 129Sv library and sequenced directly from an additional strain, B6C3Fe. The mouse CD‐RAP/MIA gene is 1.5 kbp and consists of four exons. The promoter sequence of the gene contains many potential regulatory domains including 8 basic helix‐loop‐helix protein‐binding domains and an AT‐rich domain, both motifs shown to be present in the cartilage‐specific enhancer of the type II procollagen gene. Other potential cis‐acting motifs include binding sites for GATA‐1, NF‐IL6, PEA3, w‐elements, NFκB, Zeste and Sp1. The gene, called cdrap, was localized to the end of an arm of chromosome 7 at the same site as the transforming growth factor β1 (Tgf‐β1) and the glucose phosphate isomerase 1 (Gpi1) genes. Potential mouse mutants that mapped to the same region of chromosome 7 were identified. Two of the potential mutants with skeletal phenotypes were sequenced, pudgy (pu) and extra toes with spotting (Xsj); however, no mutations were found in the coding sequence. To determine whether CD‐RAP/MIA is associated with tumors of cartilage, mRNAs from a variety of rodent tissues and cell lines were screened. Expression was detected in a rodent tumor, the Swarm rat chondrosarcoma and a chondrosarcoma cell line derived from it, but not in other tissues or tumors of non‐cartilage origin. Immunolocalization revealed CD‐RAP/MIA protein localized in cartilage only. These results show that the normal expression of CD‐RAP/MIA is limited to cartilage; however, pathologically, it is expressed both in melanoma and chondrosarcoma. The restricted expression of CD‐RAP/MIA may provide an opportunity to monitor cartilage metabolic activity as well as the tumor activity of melanoma and chondrosarcoma. Dev. Dyn. 208:516–525, 1997.

Connective Tissue Growth Factor Causes Glaucoma by Modifying the Actin Cytoskeleton of the Trabecular Meshwork

The most critical risk factor for optic nerve damage in cases of primary open-angle glaucoma (POAG) is an increased intraocular pressure (IOP) caused by a resistance to aqueous humor outflow in the trabecular meshwork (TM). The molecular pathogenesis of this increase in outflow resistance in POAG has not yet been identified, but it may involve transforming growth factor TGF-β2, which is found in higher amounts in the aqueous humor of patients with POAG. Connective tissue growth factor (CTGF) is a TGF-β2 target gene with high constitutive TM expression. In this study, we show that either adenoviral-mediated or transgenic CTGF overexpression in the mouse eye increases IOP and leads to optic nerve damage. CTGF induces TM fibronectin and α-SMA in animals, whereas actin stress fibers and contractility are both induced in cultured TM cells. Depletion of CTGF by RNA interference leads to a marked attenuation of the actin cytoskeleton. Rho kinase inhibitors cause a reversible decline in the IOP of CTGF-overexpressing mice to levels seen in control littermates. Overall, the effects of CTGF on IOP appear to be caused by a modification of the TM actin cytoskeleton. CTGF-overexpressing mice provide a model that mimics the essential functional and structural aspects of POAG and offer a molecular mechanism to explain the increase of its most critical risk factor.