Melanoma Genomics

Current insights and future perspectives of ultraviolet radiation (UV) exposure: Friends and foes to the skin and beyond the skin

Ultraviolet (UV) radiation is ubiquitous in the environment, which has been classified as an established human carcinogen. As the largest and outermost organ of the body, direct exposure of skin to sunlight or UV radiation can result in sunburn, inflammation, photo-immunosuppression, photoaging and even skin cancers. To date, there are tactics to protect the skin by preventing UV radiation and reducing the amount of UV radiation to the skin. Nevertheless, deciphering the essential regulatory mechanisms may pave the way for therapeutic interventions against UV-induced skin disorders. Additionally, UV light is considered beneficial for specific skin-related conditions in medical UV therapy. Recent evidence indicates that the biological effects of UV exposure extend beyond the skin and include the treatment of inflammatory diseases, solid tumors and certain abnormal behaviors. This review mainly focuses on the effects of UV on the skin. Moreover, novel findings of the biological effects of UV in other organs and systems are also summarized. Nevertheless, the mechanisms through which UV affects the human organism remain to be fully elucidated to achieve a more comprehensive understanding of its biological effects.

The Assessment of Anti-Melanoma Potential of Tigecycline-Cellular and Molecular Studies of Cell Proliferation, Apoptosis and Autophagy on Amelanotic and Melanotic Melanoma Cells

High mortality, aggressiveness, and the relatively low effectiveness of therapy make melanoma the most dangerous of skin cancers. Previously published studies presented the promising therapeutic potential of minocycline, doxycycline, and chlortetracycline on melanoma cells. This study aimed to assess the cytotoxicity of tigecycline, a third-generation tetracycline, on melanotic (COLO 829) and amelanotic (A375) melanoma cell lines. The obtained results showed that tigecycline, proportionally to the concentration and incubation time, efficiently inhibited proliferation of both types of melanoma cells. The effect was accompanied by the dysregulation of the cell cycle, the depolarization of the mitochondrial membrane, and a decrease in the reduced thiols and the levels of MITF and p44/42 MAPK. However, the ability to induce apoptosis was only found in COLO 829 melanoma cells. A375 cells appeared to be more resistant to the treatment with tigecycline. The drug did not induce apoptosis but caused an increase in LC3A/B protein levels-an autophagy marker. The observed differences in drug action on the tested cell lines also involved an increase in p21 and p16 protein levels in melanotic melanoma, which was related to cell cycle arrest in the G1/G0 phase. The greater sensitivity of melanotic melanoma cells to the action of tigecycline suggests the possibility of considering the use of the drug in targeted therapy.

A genome-wide epistatic network underlies the molecular architecture of continuous color variation of body extremities

Deciphering the molecular architecture of coat coloration for a better understanding of the biological mechanisms underlying pigmentation still remains a challenge. We took advantage of a rabbit French experimental population in which both a pattern and a gradient of coloration from white to brown segregated within the himalayan phenotype. The whole experimental design was genotyped using the high density Affymetrix® AxiomOrcun™ SNP Array and phenotyped into 6 different groups ordered from the lighter to the darker. Genome-wide association analyses pinpointed an oligogenic determinism, under recessive and additive inheritance, involving genes already known in melanogenesis (ASIP, KIT, MC1R, TYR), and likely processed pseudogenes linked to ribosomal function, RPS20 and RPS14. We also identified (i) gene-gene interactions through ASIP:MC1R affecting light cream/beige phenotypes while KIT:RPS responsible of dark chocolate/brown colors and (ii) a genome-wide epistatic network involving several others coloration genes such as POT1 or HPS5. Finally, we determined the recessive inheritance of the English spotting phenotype likely involving a copy number variation affecting at least the end of the coding sequence of the KIT gene. Our analyses of coloration as a continuous trait allowed us to go beyond much of the established knowledge through the detection of additional genes and gene-gene interactions that may contribute to the molecular architecture of the coloration phenotype.

Chromosome 3 and 8q aberrations in Uveal Melanoma show greater impact on survival in patients with light iris versus dark iris color

PURPOSE

Individuals with gray, blue, or green iris have a higher chance of developing uveal melanoma (UM) than those with brown eyes. We wondered whether iris pigmentation might not only be related to predisposition to UM, but also to its behavior and therefore compared clinical, histopathologic, and genetic characteristics of UM between eyes with different iris colors.

DESIGN

We determined iris color in a large cohort of patients who had undergone an enucleation for UM. Clinical and histopathological tumor characteristics, chromosome status, and survival were compared between three groups, based on iris color.

PARTICIPANTS

412 patients with choroidal/ciliary body UM, who had undergone primary enucleation at the Leiden University Medical Center (LUMC), Leiden, The Netherlands, between 1993 and 2019, divided into three groups, based on iris color (gray/blue, green/hazel, and brown). Validation cohort: 934 choroidal/ciliary body UM patients treated at Wills Eye Hospital (WEH), Philadelphia, United States.

METHODS

Comparison of clinical, histopathologic, and genetic characteristics of UM in patients with different iris colors.

MAIN OUTCOME MEASURES

Melanoma-related survival in UM patients, divided over three iris color groups, in relation to the tumor's chromosome 3 and 8q status.

RESULTS

Moderate and heavy tumor pigmentation was especially seen in eyes with brown iris (p < 0.001). Survival did not differ between patients with different iris colors (p = 0.28). However, in patients with a light iris, copy number changes in chromosome 3 and 8q had a greater influence on survival than in patients with a dark iris. Similarly, chromosome 3 and chromosome 8q status affected survival more among patients with lightly-pigmented tumors than in patients with heavily-pigmented tumors. The WEH cohort similarly showed a greater influence of chromosome aberrations in light-eyed individuals.

CONCLUSIONS

While iris color by itself did not relate to survival of UM patients, chromosome 3 and 8q aberrations had a much larger influence on survival in patients with light iris compared to those with brown iris. This suggests a synergistic effect of iris pigmentation and chromosome status in the regulation of oncogenic behavior of UM. Iris color should be taken into consideration when calculating the risk for developing metastases.

Aetiology and Pathogenesis of Cutaneous Melanoma: Current Concepts and Advances

Melanoma develops from malignant transformations of the pigment-producing melanocytes. If located in the basal layer of the skin epidermis, melanoma is referred to as cutaneous, which is more frequent. However, as melanocytes are be found in the eyes, ears, gastrointestinal tract, genitalia, urinary system, and meninges, cases of mucosal melanoma or other types (e.g., ocular) may occur. The incidence and morbidity of cutaneous melanoma (cM) are constantly increasing worldwide. Australia and New Zealand are world leaders in this regard with a morbidity rate of 54/100,000 and a mortality rate of 5.6/100,000 for 2015. The aim of this review is to consolidate and present the data related to the aetiology and pathogenesis of cutaneous melanoma, thus rendering them easier to understand. In this article we will discuss these problems and the possible impacts on treatment for this disease.

Defining the Criteria for Reflex Testing for BRAF Mutations in Cutaneous Melanoma Patients

Targeted therapy has been developed through an in-depth understanding of molecular pathways involved in the pathogenesis of melanoma. Approximately ~50% of patients with melanoma have tumors that harbor a mutation of the BRAF oncogene. Certain clinical features have been identified in BRAF-mutated melanomas (primary lesions located on the trunk, diagnosed in patients <50, visibly pigmented tumors and, at times, with ulceration or specific dermatoscopic features). While BRAF mutation testing is recommended for stage III-IV melanoma, guidelines differ in recommending mutation testing in stage II melanoma patients. To fully benefit from these treatment options and avoid delays in therapy initiation, advanced melanoma patients harboring a BRAF mutation must be identified accurately and quickly. To achieve this, clear definition and implementation of BRAF reflex testing criteria/methods in melanoma should be established so that patients with advanced melanoma can arrive to their first medical oncology appointment with a known biomarker status. Reflex testing has proven effective for a variety of cancers in selecting therapies and driving other medical decisions. We overview the pathophysiology, clinical presentation of BRAF-mutated melanoma, current guidelines, and present recommendations on BRAF mutation testing. We propose that reflex BRAF testing should be performed for every melanoma patient with stages ≥IIB.