Prognostic parameters for the primary care of melanoma patients: what is really risky in melanoma?

[Translational research and diagnostics of melanoma]

Although early stage malignant melanoma (MM) has a favorable prognosis five year survival rate is poor (<10%) in patients suffering from distant metastases. Due to molecular typing of MM recently high response rates were achieved in metastatic MM by using specific inhibitors directed against the mutated form of BRAF kinase, e.g. Vemurafinib and Dabrafinib. Therefore BRAF mutation analysis has become standard of care in advanced MM and pathologists are urged to provide a quality guaranteed molecular diagnostics. However, squamous neoplasias (e. g., keratoacanthomas) and recurrences of MM mostly within 6 months during targeted therapy point to the need of further translational research. Thus new drugs, such as MEK inhibitors, based on the MAP-kinase pathway downstream of BRAF have already effectively been used. Finally, the impact of molecular characteristics in different subtypes of MM (acral, mucosal, uveal) will be discussed with respect to their specific mutational spectrum (e.g. cKIT , NRAS , GNAQ).

Integrative genomics identifies gene signature associated with melanoma ulceration

Background

Despite the extensive research approaches applied to characterise malignant melanoma, no specific molecular markers are available that are clearly related to the progression of this disease. In this study, our aims were to define a gene expression signature associated with the clinical outcome of melanoma patients and to provide an integrative interpretation of the gene expression -, copy number alterations -, and promoter methylation patterns that contribute to clinically relevant molecular functional alterations.

Methods

Gene expression profiles were determined using the Affymetrix U133 Plus2.0 array. The NimbleGen Human CGH Whole-Genome Tiling array was used to define CNAs, and the Illumina GoldenGate Methylation platform was applied to characterise the methylation patterns of overlapping genes.

Results

We identified two subclasses of primary melanoma: one representing patients with better prognoses and the other being characteristic of patients with unfavourable outcomes. We assigned 1,080 genes as being significantly correlated with ulceration, 987 genes were downregulated and significantly enriched in the p53, Nf-kappaB, and WNT/beta-catenin pathways. Through integrated genome analysis, we defined 150 downregulated genes whose expression correlated with copy number losses in ulcerated samples. These genes were significantly enriched on chromosome 6q and 10q, which contained a total of 36 genes. Ten of these genes were downregulated and involved in cell-cell and cell-matrix adhesion or apoptosis. The expression and methylation patterns of additional genes exhibited an inverse correlation, suggesting that transcriptional silencing of these genes is driven by epigenetic events.

Conclusion

Using an integrative genomic approach, we were able to identify functionally relevant molecular hotspots characterised by copy number losses and promoter hypermethylation in distinct molecular subtypes of melanoma that contribute to specific transcriptomic silencing and might indicate a poor clinical outcome of melanoma.