Melanoma - Research

Research

Pharmacotherapy research for unresectable or metastatic malignant melanoma offers new treatment possibilities. In addition to the advances with recently approved agents, ongoing research into combination therapy, such as dabrafenib and trametinib, may reveal a more effective and better-tolerated option for patients with metastatic melanoma. One important pathway in melanin synthesis involves the transcription factor MITF. The MITF gene is highly conserved and is found in people, mice, birds, and even fish. MITF production is regulated via a fairly straightforward pathway. UV radiation causes increased expression of transcription factor p53 in keratinocytes, and p53 causes these cells to produce melanocyte-stimulating hormone (MSH), which binds to melanocortin 1 receptors (MC1R) on melanocytes. Ligand-binding at MC1R receptors activates adenylate cyclases, which produce cAMP, which activates CREB, which promote MITF expression. The targets of MITF include p16 (a CDK inhibitor) and Bcl2, a gene essential to melanocyte survival. It is often difficult to design drugs that interfere with transcription factors, but perhaps new drugs will be discovered that can impede some reaction in the pathway upstream of MITF.

Studies of chromatin structure also promise to shed light on transcriptional regulation in melanoma cells. It has long been assumed that nucleosomes are positioned randomly on DNA, but murine studies of genes involved in melanin production now suggest that nucleosomes are stereotypically positioned on DNA. When a gene is undergoing transcription, its transcription start site is almost always nucleosome-free. When the gene is silent, however, nucleosomes often block the transcriptional start site, suggesting that nucleosome position may play a role in gene regulation.

Finally, given the fact that melanin helps protect skin cells from UV-induced damage, new melanoma prevention strategies could involve attempts to induce melanin synthesis in individuals who would otherwise get sunburns. Redheads, for example, do not tan because they have MC1R mutations. In mice, it has been shown that the melanin production pathway can be rescued downstream of MC1R.

A study published on January 27, 2011, by M. Raza Zaidi et al. shows that interferon-γ links ultraviolet radiation to melanomagenesis in mice. Using a mouse model that allowed the visual tracking and purification of melanocytes using a green fluorescent dye, data showed that UVB-induced, macrophage-enhanced interferon-γ release results in melanoma growth, proliferation and immunoevasion. Based on these results, the interferon-γ pathway can potentially serve as part of new therapeutic measures to treat patients suffering from malignant melanoma, as well as a potential preventive strategy against UV-induced radiation.