Melanoma

Melanoma History Epidemiology & Causes Genetics Symptoms and signs Prevention Diagnosis Types of primary melanoma Prognostic factors Treatment Complications Future thought

Genetics

Familial melanoma is genetically heterogeneous, and loci for familial melanoma have been identified on the chromosome arms 1p, 9p and 12q. Multiple genetic events have been related to the pathogenesis of melanoma. The multiple tumor suppressor 1 (CDKN2A/MTS1) gene encodes p16INK4a - a low-molecular weight protein inhibitor of cyclin-dependent protein kinases (CDKs) - which has been localised to the p21 region of human chromosome 9. Today, melanomas are diagnosed only after they become visible on the skin. In the future, however, physicians will hopefully be able detect melanomas based on a patient’s genotype, not just his or her phenotype. Recent genetic advances promise to help doctors to identify people with high-risk genotypes and to determine which of a person’s lesions have the greatest chance of becoming cancerous. A number of rare mutations, which often run in families, are known to greatly increase one’s susceptibility to melanoma. One class of mutations affects the gene CDKN2A. An alternative reading frame mutation in this gene leads to the destabilization of p53, a transcription factor involved in apoptosis and in fifty percent of human cancers. Another mutation in the same gene results in a non-functional inhibitor of CDK4, a [cyclin-dependent kinase] that promotes cell division. Mutations that cause the skin condition Xeroderma Pigmentosum (XP) also seriously predispose one to melanoma. Scattered throughout the genome, these mutations reduce a cell’s ability to repair DNA. Both CDKN2A and XP mutations are highly penetrant. Other mutations confer lower risk but are more prevalent in the population. People with mutations in the MC1R gene, for example, are two to four times more likely to develop melanoma than those with two wild-type copies of the gene. MC1R mutations are very common; in fact, all people with red hair have a mutated copy of the gene. Two-gene models of melanoma risk have already been created, and in the future, researchers hope to create genome-scale models that will allow them to predict a patient’s risk of developing melanoma based on his or her genotype. In addition to identifying high-risk patients, researchers also want to identify high-risk lesions within a given patient. Many new technologies, such as optical coherence tomography (OCT), are being developed to accomplish this. OCT allows pathologists to view 3-D reconstructions of the skin and offers more resolution than past techniques could provide. In vivo confocal microscopy and fluorescently tagged antibodies are also proving to be valuable diagnostic tools.