Comprehensive mutational analysis of CDKN2A and CDK4 in Greek patients with cutaneous melanoma.

BACKGROUND: The penetrance of CDKN2A mutations is subject to geographical and latitudinal variation and is presumably dictated by ultraviolet radiation exposure and possibly other co-inherited genetic factors. The frequency of mutations increases with the number of family members affected and the number of primary tumours, and also fluctuates with geography. To date, little is known about the prevalence of CDKN2A mutations in patients with melanoma from Greece. OBJECTIVE: To characterize the frequency of CDKN2A and CDK4 mutations in a hospital-based population of Greek patients with melanoma. METHODS: Three hundred and four consecutive single primary melanoma (SPM), nine familial melanoma (FM) and seven multiple primary melanoma cases (MPM) were assessed for sequence variants in exons 1α, 1ß and 2 of CDKN2A and exon 2 of CDK4. RESULTS: Germline CDKN2A mutations were detected in 10 of 304 SPM (3·3%), in four of seven MPM (57%) and in two of nine FM (22%) cases. The most common mutation was a Northern European allele (p16 p.R24P) detected in eight individuals. Five previously unreported CDKN2A variants were also identified: -34G>C, c.41_43delins20bp, c.301G>C (p.G101R), c.301G>A (p.G101E) and c.296_297insGACC. We also describe the first report of a CDK4 p.R24H substitution in a Greek family. CONCLUSIONS: The Greek population appears to harbour a higher prevalence of the CDKN2A mutation than other reported cohorts. This supports the notion that genetic susceptibility may play a stronger influence in a country with a relatively low incidence of melanoma. Furthermore, the identification of Northern European alleles suggests that gene migration may be responsible, in part, for the observed cases in Greece.

EphA2 is a critical oncogene in melanoma.

EphA2 is a member of the Eph family of receptor tyrosine kinases and is highly expressed in many aggressive cancer types, including melanoma. We recently showed that EphA2 is also upregulated by ultraviolet radiation and is able to induce apoptosis. These findings suggest that EphA2 may have different, even paradoxical, effects on viability depending on the cellular context and that EphA2 mediates a delicate balance between life and death of the cell. To functionally clarify EphA2's role in melanoma, we analyzed a panel of melanoma cell lines and found that EphA2 levels are elevated in a significant fraction of the samples. Specific depletion of EphA2 in high-expressing melanoma cells using short hairpin RNA led to profound reductions in cellular viability, colony formation and migration in vitro and a dramatic loss of tumorigenic potential in vivo. Stable introduction of EphA2 into low-expressing cell lines enhanced proliferation, colony formation and migration, further supporting its pro-malignant phenotype. Interestingly, transient expression of EphA2 and/or Braf(V600E) in non-transformed melanocytes led to significant and additive apoptosis. These results verify that EphA2 is an important oncogene and potentially a common source of 'addiction' for many melanoma cells. Moreover, acute induction of EphA2 may purge genetically susceptible cells, thereby uncovering a more aggressive population that is in fact dependent on the oncogene.