Clinical and Molecular Characterization of Patients at Risk for Hereditary Melanoma in Southern Brazil

Characterization of Potential Melanoma Predisposition Genes in High-Risk Brazilian Patients

Increased genetic risk for melanoma can occur in the context of germline pathogenic variants in high-penetrance genes, such as CDKN2A and CDK4, risk variants in low- to moderate-penetrance genes (MC1R and MITF), and possibly due to variants in emerging genes, such as ACD, TERF2IP, and TERT. We aimed to identify germline variants in high- and low- to moderate-penetrance melanoma risk genes in Brazilian patients with clinical criteria for familial melanoma syndrome. We selected patients with three or more melanomas or melanoma patients from families with three tumors (melanoma and pancreatic cancer) in first- or second-degree relatives. Genetic testing was performed with a nine-gene panel (ACD, BAP1, CDK4, CDKN2A, POT1, TERT, TERF2IP, MC1R, and MITF). In 36 patients, we identified 2 (5.6%) with germline pathogenic variants in CDKN2A and BAP1 and 4 (11.1%) with variants of uncertain significance in the high-penetrance genes. MC1R variants were found in 86.5%, and both red hair color variants and unknown risk variants were enriched in patients compared to a control group. The low frequency of germline pathogenic variants in the high-penetrance genes and the high prevalence of MC1R variants found in our cohort show the importance of the MC1R genotype in determining the risk of melanoma in the Brazilian melanoma-prone families.

Family-based whole-exome sequencing identifies rare variants potentially related to cutaneous melanoma predisposition in Brazilian melanoma-prone families

Genetic predisposition accounts for nearly 10% of all melanoma cases and has been associated with a dozen moderate- to high-penetrance genes, including CDKN2A, CDK4, POT1 and BAP1. However, in most melanoma-prone families, the genetic etiology of cancer predisposition remains undetermined. The goal of this study was to identify rare genomic variants associated with cutaneous melanoma susceptibility in melanoma-prone families. Whole-exome sequencing was performed in 2 affected individuals of 5 melanoma-prone families negative for mutations in CDKN2A and CDK4, the major cutaneous melanoma risk genes. A total of 288 rare coding variants shared by the affected relatives of each family were identified, including 7 loss-of-function variants. By performing in silico analyses of gene function, biological pathways, and variant pathogenicity prediction, we underscored the putative role of several genes for melanoma risk, including previously described genes such as MYO7A and WRN, as well as new putative candidates, such as SERPINB4, HRNR, and NOP10. In conclusion, our data revealed rare germline variants in melanoma-prone families contributing with a novel set of potential candidate genes to be further investigated in future studies.

Molecular landscape of Hereditary Melanoma

Melanoma is considered the most lethal skin cancer and its incidence has increased during the past decades. About 10 % of cases are classified as hereditary melanoma. Genetic predisposition usually manifests itself clinically as early onset and multiple cutaneous melanomas. Several genes have been identified as involved to melanoma susceptibility, some of them still with unknown clinical relevance. Beyond melanoma, the affected families are also more prone to develop other malignancies, such as pancreatic cancer. The identification of risk families and involved genes is of great importance, since different forms of oncological surveillance are recommended. However, well established guidelines to standardize both the selection of individuals and the genetic panel to be requested are still lacking. Given the importance of the genetic counseling and testing in the context of clinical suspicion of hereditary melanoma, this paper aims to review the literature regarding genetic panel indications worldwide.

CDKN2A Polymorphism in Melanoma Patients in Colombian Population: A Case-Control Study

INTRODUCTION

Melanoma is the most aggressive type of skin cancer, with poor prognosis in advanced stages. The incidence and mortality rates have increased in recent years. Single nucleotide polymorphisms p.R24P, p.M53I, p.G101W, p.V126D, and p.A148T in the CDKN2A (HGNC ID: 1787) gene have been associated with the development of melanoma in different populations; however, this association has not been studied in Colombia.

METHODS

Cutaneous melanoma patients and healthy controls (85 cases and 166 controls) were included in this study. These subjects were screened through HRM-qPCR assay and detected variants in exon 1 and 2 of CDKN2A gene and confirmed with Sanger sequencing. Chi-square test was used to compare allele and genotype distributions between cases and controls. Odds ratio (OR) with 95% confidence interval (CI) was calculated to determine the association between polymorphisms and haplotypes with melanoma susceptibility. Statistical and haplotype analyses were performed using Stata® and R-Studio®.

RESULTS

Fifty-four percent of women were identified both in cases and controls. The frequencies of melanoma subtypes were 36,47% lentigo maligna, 24,71% acral lentiginous, 23,53% superficial extension, and 15,29% nodular. Variants in the CDKN2A gene were 11.76% in cases and 8.43% in controls. The most frequent was p.A148T in 5.88% of cases and in 4.82% of controls. GGTTG haplotype showed statistically significant differences between cases and controls (p value = 0.04).

CONCLUSION

CDKN2A polymorphisms p.G101W, p.R24P, p.M53I, and A148T are not associated with melanoma susceptibility in the Colombian population; further studies regarding genetic interaction and additive effects between more variants are required.

Characterization of individuals at high risk of developing melanoma in Latin America: bases for genetic counseling in melanoma

Purpose:

CDKN2A is the main high-risk melanoma-susceptibility gene, but it has been poorly assessed in Latin America. We sought to analyze CDKN2A and MC1R in patients from Latin America with familial and sporadic multiple primary melanoma (SMP) and compare the data with those for patients from Spain to establish bases for melanoma genetic counseling in Latin America.

Genet Med18 7, 727–736.

Methods:

CDKN2A and MC1R were sequenced in 186 Latin American patients from Argentina, Brazil, Chile, Mexico, and Uruguay, and in 904 Spanish patients. Clinical and phenotypic data were obtained.

Genet Med18 7, 727–736.

Results:

Overall, 24 and 14% of melanoma-prone families in Latin America and Spain, respectively, had mutations in CDKN2A. Latin American families had CDKN2A mutations more frequently (P = 0.014) than Spanish ones. Of patients with SMP, 10% of those from Latin America and 8.5% of those from Spain had mutations in CDKN2A (P = 0.623). The most recurrent CDKN2A mutations were c.-34G>T and p.G101W. Latin American patients had fairer hair (P = 0.016) and skin (P < 0.001) and a higher prevalence of MC1R variants (P = 0.003) compared with Spanish patients.

Genet Med18 7, 727–736.

Conclusion:

The inclusion criteria for genetic counseling of melanoma in Latin America may be the same criteria used in Spain, as suggested in areas with low to medium incidence, SMP with at least two melanomas, or families with at least two cases among first- or second-degree relatives.

Genet Med18 7, 727–736.

Epidemiology of melanoma in the South of Brazil: study of a city in the Vale do Itajaí from 1999 to 2013

BACKGROUND

Cutaneous melanoma is a highly aggressive malignancy with increasing incidence worldwide. The southern Brazilian state of Santa Catarina has one of the highest incidence rates of melanoma in the country.

OBJECTIVE

To evaluate the epidemiological profile of melanoma patients in a southern city of Brazil.

METHODS

a cross-sectional retrospective study was conducted, aiming to detect the clinical and histopathological characteristics of cutaneous melanoma diagnosed in the city of Brusque - SC, between 1999 and 2013.

RESULTS

A total of 213 cases in 212 individuals were studied. More than 50% of the patients were females (p< 0.05). The trunk was the most commonly affected site (p< 0.05), followed by the upper limbs. Nodular and superficial spreading melanomas were the most commonly detected in histological analyses. They did not differ statistically in frequency, but were more prevalent than other histopathological subtypes (p< 0.05). There was no statistically significant difference between invasive and noninvasive melanomas (p= 0.2441). Among the invasive melanomas, those with Breslow thicknesses < 1 mm and between 1-2mm were more prevalent (p< 0.05).

CONCLUSIONS

In this study we found a higher frequency of melanomas in female patients and patients aged over 51. The trunk was the most commonly affected site. Nodular and superficial spreading melanomas prevailed. Among invasive melanomas, those with Breslow thicknesses < 2 mm were the most frequent. This paper highlights the epidemiological profile of melanoma patients in the city and may help to identify and aid in the follow-up of those who are most likely to present the disease.

Germline CDKN2A mutations in Brazilian patients of hereditary cutaneous melanoma

Approximately 10 % of all cutaneous melanoma cases occur in a familial context. The major susceptibility gene for familial melanoma is CDKN2A. In Latin America, genetic studies investigating melanoma predisposition are scarce. The aim of this work was to investigate germline CDKN2A point mutations and genomic rearrangements in a cohort of 59 Brazilian melanoma-prone patients. Screening of CDKN2A alterations was performed by sequencing and multiplex ligation probe amplification. Germline CDKN2A mutations affecting p16(INK4a) were detected in 8 unrelated probands (13.6 %), including 7 familial cases and one patient with multiple melanomas; 4 out of 8 mutation carriers met the criteria for familial melanoma and had multiple primary lesions. Although this study adds to the literature on melanoma susceptibility in Latin America, it is limited by the small size of the cohort. Our findings suggest that stringent inclusion criteria led to a substantially increased rate of CDKN2A mutation detection. This consideration should be taken into account when referring patients for genetic screening in a setting of limited budget, such as in developing countries.

Genetic variations of patients with familial or multiple melanoma in Southern Brazil

BACKGROUND

Patients with familial melanoma or multiple primary melanoma represent a high-risk population to hereditary melanoma. Mutations in susceptibility genes, such as CDKN2A, CDK4 and MC1R, have been associated with the development of melanoma.

OBJECTIVES

The purpose of this study was to determine the genotypic background of patients with familial and/or multiple melanoma in southern Brazil.

METHODS

This study analysed 33 cases (5 patients with multiple primary melanoma and 28 patients from families with at least two well documented cases) and 29 controls. Genomic analysis of CDKN2A and CDK4 genes by PCR-SSCP analysis and sequencing and direct sequencing of MC1R were performed in all individuals.

RESULTS

No functional mutations in CDKN2A or CDK4 were detected in the 62 individuals. Infrequent variants in polymorphic loci of CDKN2A gene were identified in 15 participants (24.2%) and 24/33 (72.8%) cases and 19/27 (70.4%) controls reported at least one infrequent variant in MC1R (P = 0.372). Furthermore, a non-significant tendency towards an association between melanoma risk and MC1R variants G274A and C451T and a non-significant linear tendency to the number of infrequent high-risk variants in MC1R were observed.

CONCLUSIONS

These results suggest that in southern Brazilian population, CDKN2A or CDK4 germinal alterations may have a weaker influence than previously thought and environmental risk factors may play a central role in melanoma susceptibility. However, considering the tendency observed for gene MC1R, low-penetrance genes may be a relevant aetiological factor in southern Brazil with fair skin population and high sunlight exposure.

The CDKN2A p.A148T variant is associated with cutaneous melanoma in Southern Brazil

Several germline mutations and sequence variants in cancer predisposition genes have been described. Among these, the CDKN2A p.A148T variant appears to be frequent in patients with melanoma, at least in certain ethnic groups. In this case-control study, we evaluated 127 patients with cutaneous melanoma and 128 controls from Southern Brazil, the region with the highest melanoma incidence rates in the country. Using PCR-RFLP, we demonstrate that CDKN2A p.A148T variant was significantly more frequent in patients with melanoma than in controls (12.6% vs 3.9%; P=0.009). There was no association between presence of the polymorphism and tumor thickness, site of the primary tumor, melanoma subtype, age at diagnosis, quantitative and qualitative number of nevi. Patients with a positive family of history for other cancers were particularly prone to carry the CDKN2A p.A148T allele. All patients with p.A148T-positive melanoma reported European ancestry, especially German, and this was confirmed using a panel of ancestry-informative INDELs. Our data suggest that CDKN2A p.A148T is a melanoma susceptibility allele in Southern Brazil and is particularly common in patients with melanoma of predominantly European ancestry.

Management of melanoma families

In this review we have aimed to focus on the clinical management of familial melanoma patients and their relatives. Along this line three major topics will be discussed: (1) management/screening of familial melanoma families: what is advised and what is the evidence thereof; (2) variability of families worldwide with regard to clinical phenotype, including cancer spectrum and likelihood of finding germline mutations and (3) background information for clinicians on the molecular biology of familial melanoma and recent developments in this field.

CDKN2A mutations in melanoma families from Uruguay

BACKGROUND

Familial melanoma, a cluster of several cases within a single family, accounts for approximately 10% of cases of melanoma. Hereditary melanoma is defined as two or more first-degree relatives having melanoma. A member of a melanoma-prone family has a 35-70-fold increased relative risk of developing a melanoma. Genetic susceptibility is linked to the major susceptibility genes CDKN2A and CDK4, and the minor susceptibility gene MC1R.

OBJECTIVES

To determine the clinical and genetic characteristics of cutaneous melanoma in melanoma-prone families from Uruguay.

METHODS

We studied 13 individuals from six melanoma-prone families living in Uruguay. Phenotype, familial and personal history were recorded. Molecular screening of CDKN2A and CDK4 was done by polymerase chain reaction-single strand conformational polymorphism analysis. The MC1R gene was sequenced.

RESULTS

Mutations in CDKN2A were detected in five of six families: c.-34G>T, p.G101W and p.E88X. A novel germline mutation p.E88X, associated with hereditary melanoma in two unrelated families, is described. We hypothesize that a founder effect occurred probably in the Mediterranean region. No mutations in CDK4 were detected. Six different MC1R variants, all previously reported, were present in Uruguayan families.

CONCLUSIONS

The overall rate of deleterious CDKN2A mutations in our familial melanoma pedigrees, even though the sample size is small, was considerably higher (83%) than the often quoted range.

CARF: an emerging regulator of p53 tumor suppressor and senescence pathway

Replicative senescence, a major outcome of normal cells with finite lifespan, is a widely accepted in vitro model for ageing studies. Limited repair and defense mechanisms of normal cells, in addition to DNA alterations and oncogene inductions under stress, are believed to result in senescence as a protective mechanism to prevent undesirable proliferation of cells. The ARF/p53/p21(cip1/waf1) tumor suppression pathway acts as a molecular sensor and regulator of cellular stress, senescence, and immortalization. Understanding the molecular regulation of this pathway by intrinsic and extrinsic signals is extremely important to address unsolved questions in senescence and cancer. CARF was first discovered as a binding partner of ARF and has since been shown to have both ARF-dependent and -independent functions that converge to regulate p53 pathway. CARF directly binds to p53 and HDM2, and functions in a negative feedback pathway. Whereas CARF transcriptionally represses HDM2 to increase p53 activity, HDM2 in return degrades CARF. Thus, CARF may act as a novel key regulator of the p53 pathway at multiple checkpoints. The aim of this article is to discuss the current knowledge about functions of CARF and its impact on p53 pathway in regulation of senescence and carcinogenesis.