A French CDK4-positive melanoma family with a co-inherited EDNRB mutation

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Cutaneous melanoma

In the past decade, major advances have been made in the understanding of melanoma. New predisposition genes have been reported and key somatic events, such as BRAF mutation, directly translated into therapeutic management. Surgery for localised melanoma and regional lymph node metastases is the standard of care. Sentinel-node biopsy provides precise staging, but has not been reported to affect survival. The effect of lymph-node dissection on survival is a topic of investigation. Two distinct approaches have emerged to try to extend survival in patients with metastatic melanoma: immunomodulation with anti-CTLA4 monoclonal antibodies, and targeted therapy with BRAF inhibitors or MEK inhibitors for BRAF-mutated melanoma. The combination of BRAF inhibitors and MEK inhibitors might improve progression-free survival further and, possibly, increase overall survival. Response patterns differ substantially-anti-CTLA4 immunotherapy can induce long-term responses, but only in a few patients, whereas targeted drugs induce responses in most patients, but nearly all of them relapse because of pre-existing or acquired resistance. Thus, the long-term prognosis of metastatic melanoma remains poor. Anti-PD1 and anti-PDL1 antibodies have emerged as breakthrough drugs for melanoma that have high response rates and long durability. Biomarkers that have predictive value remain elusive in melanoma, although emerging data for adjuvant therapy indicate that interferon sensitivity is associated with ulceration of the primary melanoma. Intense investigation continues for clinical and biological markers that predict clinical benefit of immunotherapeutic drugs, such as interferon alfa or anti-CTLA4 antibodies, and the mechanisms that lead to resistance of targeted drugs.

Early progress in epigenetic regulation of endothelin pathway genes

Control of gene transcription is a major regulatory determinant for function of the endothelin pathway. Epigenetic mechanisms act on tissue-specific gene expression during development and in response to physiological stimuli. Most of the limited evidence available on epigenetic regulation of the endothelin pathway focuses on the EDN1 and EDNRB genes. Examination of whole genome databases suggests that both genes are influenced by histone modifications and DNA methylation. This interpretation is supported by studies directed at detecting epigenetic action on the two genes. The clearest illustration of epigenetic factors altering endothelin signalling is DNA methylation-associated EDNRB silencing during tumourigenesis. This review summarizes our current understanding of epigenetic regulation of the endothelin pathway genes. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

Melanoma prone families with CDK4 germline mutation: phenotypic profile and associations with MC1R variants

Background

CDKN2A and CDK4 are high risk susceptibility genes for cutaneous malignant melanoma. Melanoma families with CDKN2A germline mutations have been extensively characterised, whereas CDK4 families are rare and lack a systematic investigation of their phenotype.

Methods

All known families with CDK4 germline mutations (n=17) were recruited for the study by contacting the authors of published papers or by requests via the Melanoma Genetics Consortium (GenoMEL). Phenotypic data related to primary melanoma and pigmentation characteristics were collected. The CDK4 exon 2 and the complete coding region of the MC1R gene were sequenced.

Results

Eleven families carried the CDK4 R24H mutation whereas six families had the R24C mutation. The total number of subjects with verified melanoma was 103, with a median age at first melanoma diagnosis of 39 years. Forty-three (41.7%) subjects had developed multiple primary melanomas (MPM). A CDK4 mutation was found in 89 (including 62 melanoma cases) of 209 tested subjects. CDK4 positive family members (both melanoma cases and unaffected subjects) were more likely to have clinically atypical nevi than CDK4 negative family members (p<0.001). MPM subjects had a higher frequency of MC1R red hair colour variants compared with subjects with one tumour (p=0.010).

Conclusion

Our study shows that families with CDK4 germline mutations cannot be distinguished phenotypically from CDKN2A melanoma families, which are characterised by early onset of disease, increased occurrence of clinically atypical nevi, and development of MPM. In a clinical setting, the CDK4 gene should therefore always be examined when a melanoma family tests negative for CDKN2A mutation.

EDNRB gene variants and melanoma risk in two southern European populations

BACKGROUND

EDNRB gene variants were reported to be associated with melanoma risk in French patients, with the S305N variant showing the highest frequency.

AIM

To verify the S305N association with melanoma risk in an independent larger French population (378 patients, 389 controls); to investigate the role of EDNRB variants in melanoma risk in an Italian population (133 patients, 118 controls); and to explore the association of CDKN2A or CDK4 mutations with the S305N EDNRB variant in a subgroup of patients (59 French, 12 Italian) with a suspected hereditary predisposition to melanoma (familial melanoma, sporadic multiple primary melanoma or melanoma associated with pancreatic cancer).

METHODS

The S305N variant was genotyped in the French population, while the EDNRB gene in the Italian population was entirely sequenced.

RESULTS

Overall, there was no significant difference in the frequency of the S305N variant between patients with sporadic melanoma and controls in either the French or the Italian population. However, a significantly higher S305N allele frequency was detected in French patients with a suspected hereditary predisposition to melanoma compared with controls (P = 0.04). In addition, in this subgroup of patients, the S305N allele was also significantly associated with the presence of CDKN2A mutations (P = 0.04).

CONCLUSIONS

Our results showed no evidence of association of the S305N EDNRB polymorphism with sporadic melanoma risk in either the French or Italian populations, but there was an indication that EDNRB might be a melanoma-predisposing gene in French patients with a suspected hereditary predisposition to melanoma.

Roles of endothelin signaling in melanocyte development and melanoma

Endothelin (Edn) signaling via the G-coupled, Edn receptor type B (Ednrb) is essential for the development of melanocytes from the neural crest (NC) and has been associated with melanoma progression. Edn3 plays varying roles during melanocyte development, promoting the proliferation and self-renewal of NC-derived multi- and bi-potential precursors as well as the survival, proliferation, differentiation and migration of committed melanocyte precursors. Melanocyte differentiation is achieved via the interaction of Ednrb and Kit signaling, with Ednrb being specifically required in the final differentiation step, rather than in the initial specification of melanocytic fate. Ednrb has also been implicated in the de-differentiation of mature melanocytes, a process that takes place during the malignant transformation of these cells. Ednrb was found to be upregulated in melanoma metastases and was shown to alter tumor-host interactions leading to melanoma progression. Antagonists to this receptor were shown to inhibit melanoma cell growth and increase the apoptotic rate of these cells, and to lead to disease stabilization in melanoma patients. Thus, Edn signaling inhibition may prove useful in the treatment of certain types of melanoma.

Childhood melanoma

Pediatric melanoma is rare but increasing in incidence. Because early diagnosis and treatment improves prognosis, clinicians need to include it as a possible diagnosis when evaluating a pigmented lesion in a pediatric patient. Some risk factors for melanoma include xeroderma pigmentosum, giant congenital melanocytic nevi, dysplastic nevus syndrome, atypical nevi, many acquired melanocytic nevi, family history of melanoma, and immunosuppression. Definitive treatment is with surgical excision. Adjuvant therapies such as chemotherapy, immunotherapy, and radiation therapy can be used in advanced cases.

Epidemiology of invasive cutaneous melanoma

Data are presented on the current incidence of melanoma with recent and predicted future trends illustrating a likely continuing increase in incidence. Risk factors for developing melanoma are discussed, including current known melanoma susceptibility genes. Phenotypic markers of high-risk subjects include high counts of benign melanocytic naevi. Other risk factors considered include exposure to natural and artificial ultraviolet radiation, the effect of female sex hormones, socioeconomic status, occupation, exposure to pesticides and ingestion of therapeutic drugs including immunosuppressives and non-steroidal anti-inflammatory drugs. Aids to earlier diagnosis are considered, including public education, screening and use of equipment such as the dermatoscope. Finally, the current pattern of survival and mortality is described.

Genetic risk factors for melanoma

The genetic basis of melanoma is complex and has both inherited and acquired components. Different genomic approaches have been used to identify a number of inherited risk factors, which can be stratified by penetrance and prevalence. Rare high-penetrance factors are expressed in familial clustering of melanoma and include mutations in CDKN2A (encoding p16(INK4a) and p14(ARF)) and CDK4. These genes are involved in cell-cycle arrest and melanocyte senescence and are nearly invariably targeted by somatic mutations during melanoma progression. Low-penetrance factors are common in the general population and include single-nucleotide polymorphisms in or near MC1R, ASIP, TYR and TYRP1. These genes are major determinants of hair and skin pigmentation, but their role in melanoma development remains unclear. This review describes the efforts that have led to the current understanding of melanoma susceptibility as the result of complex gene-gene and gene-environment interactions. Despite the significant advances, the majority of familial cases remain unaccounted for.

Molecular pathogenesis of cutaneous melanocytic neoplasms

Melanoma is the deadliest form of skin cancer without an effective treatment. An understanding of the genetic basis of melanoma has recently shed light on some of the mechanisms of melanomagenesis. This review explores the major genes involved in familial and sporadic cutaneous melanoma with an emphasis on CDKN2A, CDK4, MC1R, and MAPK pathway targets (e.g., RAS and BRAF), apoptosis regulators (e.g., BCL-2, AKT, and APAF-1), and the tumor-suppressor genes TP53 and PTEN. New directions for therapeutics based on our current knowledge of the genes implicated in melanoma are also discussed.

Identification of a CDK4 R24H mutation-positive melanoma family by analysis of early-onset melanoma patients in Latvia

We have analysed 47 early-onset (< or =40 years) Latvian melanoma patients for the involvement of the melanoma susceptibility loci CDKN2A and CDK4. We observed no disease-related mutations in CDKN2A, but one patient had a CDK4 R24H mutation and strong family history of melanoma. Haplotype analysis using microsatellite markers and single nucleotide polymorphisms showed that the Latvian haplotype is unique compared with that of other melanoma families with the R24H mutation. This finding supports the proposal that codon 24 is a mutational hotspot in the CDK4 gene.

p16INK4a-induced senescence is disabled by melanoma-associated mutations

The p16^INK4a-Rb tumour suppressor pathway is required for the initiation and maintenance of cellular senescence, a state of permanent growth arrest that acts as a natural barrier against cancer progression. Senescence can be overcome if the pathway is not fully engaged, and this may occur when p16^INK4a is inactivated. p16^INK4a is frequently altered in human cancer and germline mutations affecting p16^INK4a have been linked to melanoma susceptibility. To characterize the functions of melanoma-associated p16^INK4a mutations, in terms of promoting proliferative arrest and initiating senescence, we utilized an inducible expression system in a melanoma cell model. We show that wild-type p16^INK4a promotes rapid cell cycle arrest that leads to a senescence programme characterized by the appearance of chromatin foci, activation of acidic β-galactosidase activity, p53 independence and Rb dependence. Accumulation of wild-type p16^INK4a also promoted cell enlargement and extensive vacuolization independent of Rb status. In contrast, the highly penetrant p16^INK4a variants, R24P and A36P failed to arrest cell proliferation and did not initiate senescence. We also show that overexpression of CDK4, or its homologue CDK6, but not the downstream kinase, CDK2, inhibited the ability of wild-type p16^INK4a to promote cell cycle arrest and senescence. Our data provide the first evidence that p16^INK4a can initiate a CDK4/6-dependent autonomous senescence programme that is disabled by inherited melanoma-associated mutations.

Population-based prevalence of CDKN2A and CDK4 mutations in patients with multiple primary melanomas

The presence of multiple primary cutaneous melanomas (MPM) has been advocated as guidance to identifying melanoma families. Frequencies of CDKN2A mutations in materials of sporadic MPM cases from pigmented lesion clinics vary between 8 and 15%. Patients with MPM have therefore been regarded as good candidates for CDKN2A mutational screening. We describe a population-based study where all persons in Norway diagnosed with MPM between 1953 and 2004 (n = 738 alive per April 2004) were invited to participate. Three-hundred-and-ninety patients (52.8%) responded confidentially. Mutations in CDKN2A were found in 6.9% of the respondents. Eighty-one MPM patients (20.8%) reported that they belonged to melanoma families, and 17 (21.0%) of these harboured a CDKN2A mutation, compared to 3.2% of the nonfamilial cases. The probability of finding a CDKN2A mutation increased when the patients had three or more melanomas, or a young age of onset of first melanoma. We identified five novel CDKN2A variants (Ala57Gly, Pro81Arg, Ala118Val, Leu130Val, and Arg131Pro) and four that previously have been reported in melanoma families (Glu27X, Met53Ile, Arg87Trp, and Ala127Pro). A large deletion (g.13623_23772del10150) encompassing exon 1alpha and the 5' part of exon 2 was detected in six patients with a family history of melanoma. Three patients, belonging to the same family, had the CDK4 Arg24His mutation. The frequency of CDKN2A mutations was lower than previously reported in other studies, an observation which probably is due to the population-based design of our study.

G-protein-coupled receptors and melanoma

G-protein-coupled receptors (GPCR) are the largest family of receptors with over 500 members. Evaluation of GPCR gene expression in primary human tumors identified over-expression of GPCR in several tumor types. Analysis of cancer samples in different disease stages also suggests that some GPCR may be involved in early tumor progression and others may play a critical role in tumor invasion and metastasis. Currently, >50% of drug targets to various human diseases are based on GPCR. In this review, the relationships between several GPCR and melanoma development and/or progression will be discussed. Finally, the possibility of using one or more of these GPCR as therapeutic targets in melanoma will be summarized.