Expression profiling identifies genes involved in neoplastic transformation of serous ovarian cancer.

BACKGROUND: The malignant potential of serous ovarian tumors, the most common ovarian tumor subtype, varies from benign to low malignant potential (LMP) tumors to frankly invasive cancers. Given the uncertainty about the relationship between these different forms, we compared their patterns of gene expression. METHODS: Expression profiling was carried out on samples of 7 benign, 7 LMP and 28 invasive (moderate and poorly differentiated) serous tumors and four whole normal ovaries using oligonucleotide microarrays representing over 21,000 genes. RESULTS: We identified 311 transcripts that distinguished invasive from benign tumors, and 20 transcripts that were significantly differentially expressed between invasive and LMP tumors at p < 0.01 (with multiple testing correction). Five genes that were differentially expressed between invasive and either benign or normal tissues were validated by real time PCR in an independent panel of 46 serous tumors (4 benign, 7 LMP, 35 invasive). Overexpression of SLPI and WNT7A and down-regulation of C6orf31, PDGFRA and GLTSCR2 were measured in invasive and LMP compared with benign and normal tissues. Over-expression of WNT7A in an ovarian cancer cell line led to increased migration and invasive capacity. CONCLUSION: These results highlight several genes that may play an important role across the spectrum of serous ovarian tumorigenesis.

H-cadherin expression reduces invasion of malignant melanoma.

Melanocytic behavior, survival, and proliferation are regulated through a complex system of cell-cell adhesion molecules. Pathologic changes leading to development of malignant melanoma, upset the delicate homeostatic balance between melanocytes and keratinocytes and can lead to altered expression of cell-cell adhesion and cell-cell communication molecules. Malignant transformation of melanocytes frequently coincides with loss of E-cadherin expression. We now show loss of another member of the superfamily of classical cadherins, H-cadherin (CDH13), which may be involved in the development of malignant melanoma. The provided data show that H-cadherin expression is lost in nearly 80% of the analyzed melanoma cell lines. Knockdown of H-cadherin using siRNA increases invasive capacity in melanocytes. Functional assays show that the re-expression of H-cadherin decreases migration and invasion capacity, as well as anchorage-independent growth in comparison to control melanoma cells. Furthermore, melanoma cells, which re-express H-cadherin via stable transfection show a reduction in rate of tumor growth in a nu/nu mouse tumor model in comparison to the parental control transfected cell lines. Our study presents for the first time the down-regulation of H-cadherin in malignant melanomas and its possible functional relevance in maintenance healthy skin architecture.

Macrophage inhibitory cytokine-1 is overexpressed in malignant melanoma and is associated with tumorigenicity.

The incidence of malignant melanoma has increased dramatically over the past four decades. Metastatic melanoma is associated with poor prognosis, as the current treatments do not have a significant impact on prolonging survival or decreasing mortality. We have identified a member of the transforming growth factor-beta superfamily, macrophage inhibitory cytokine (MIC)-1, which is highly expressed in melanoma cells. Of 53 melanoma cell lines that were examined for relative MIC-1 expression by western blot analysis, 35 (66%) showed significantly higher levels of MIC-1 compared to normal melanocytes. Primary melanoma biopsies (15 of 22) were found to contain cells expressing low levels of MIC-1 as determined by immunohistochemistry. In contrast, all metastatic melanoma biopsies examined (16 of 16) had strong expression of MIC-1. Expression of MIC-1 was found to be dependent on the mitogen-activated protein kinase pathway, and is a transcriptional target of the microphthalmia-associated transcription factor. Knockdown of MIC-1 expression using stable short-hairpin RNA in three melanoma cell lines showed a significant decrease in tumorigenicity (P<0.0001). These results indicate that MIC-1 may function to promote development of more aggressive melanoma tumors. MIC-1 may be suitable for development as a serum diagnostic and is a possible target for the treatment of metastatic melanoma.

Histone deacetylase inhibitors and malignant melanoma.

The search for antimelanoma agents acting by terminal differentiation via the pigmentation pathway has so far been unsuccessful, in part because of tumor heterogeneity and loss of function of pigmentation genes. Some differentiation agents, however, have emerged as inhibitors of histone deacetylases (HDAC), with consequences for chromosome remodeling, cell cycle arrest and selective toxicity in cultured melanoma cells compared with normal melanocytes. Few effects have been found on pigmentation, except paradoxically the down-regulation of TRP-1. Of the many genes regulated by HDAC inhibitors, induction of p21(WAF1/Cip1) is the most consistent finding and is associated with G(1) or G(2) phase blocks. Some melanoma cell lines appear to lack an HDAC inhibitor-specific G(2) checkpoint and viability is thus compromised by dividing with inappropriately-modified chromatin. Most cultured melanoma cells undergo apoptosis following treatment with HDAC inhibitors, via a mitochondrial and caspase-dependent pathway. However, the molecular mechanism may vary with cell line and HDAC inhibitor class. Tumor selectivity cannot yet be attributed to specific types or levels of HDACs, nor has the possibility of acetylation of non-histone targets been excluded. Elucidation of these complexities may be rewarding, in terms of directing the multiple consequences of inhibiting histone deacetylation towards overcoming the therapeutic problems of melanoma heterogeneity and emergence of resistance. Success in the clinic may require combination with agents that synergize with the cell cycle blocking and pro-apoptotic action of HDAC inhibitors.

Antiproliferative and phenotype-transforming antitumor agents derived from cysteine.

Selective destruction of malignant tumor cells without damaging normal cells is an important goal for cancer chemotherapy in the 21st century. Differentiating agents that transform cancer cells to either a nonproliferating or normal phenotype could potentially be tissue-specific and avoid side effects of current drugs. However, most compounds that are presently known to differentiate cancer cells are histone deacetylase inhibitors that are of low potency or suffer from low bioavailability, rapid metabolism, reversible differentiation, and nonselectivity for cancer cells over normal cells. Here we describe 36 nonpeptidic compounds derived from a simple cysteine scaffold, fused at the C-terminus to benzylamine, at the N-terminus to a small library of carboxylic acids, and at the S-terminus to 4-butanoyl hydroxamate. Six compounds were cytotoxic at nanomolar concentrations against a particularly aggressive human melanoma cell line (MM96L), four compounds showed selectivities of > or =5:1 for human melanoma over normal human cells (NFF), and four of the most potent compounds were further tested and found to be cytotoxic for six other human cancer cell lines (melanomas SK-MEL-28, DO4; prostate DU145; breast MCF-7; ovarian JAM, CI80-13S). The most active compounds typically caused hyperacetylation of histones, induced p21 expression, and reverted phenotype of surviving tumor cells to a normal morphology. Only one compound was given orally at 5 mg/kg to healthy rats to look for bioavailability, and it showed reasonably high levels in plasma (C(max) 6 microg/mL, T(max) 15 min) for at least 4 h. Results are sufficiently promising to support further work on refining this and related classes of compounds to an orally active, more tumor-selective, antitumor drug.