Genetic basis of susceptibility to melanoma

The management of hereditary melanoma, FAMMM syndrome and germline CDKN2A mutations: a narrative review

Familial atypical multiple mole melanoma (FAMMM) syndrome is a rare autosomal dominant disorder, in which patients present with a large number of melanocytic naevi and a strong history of malignant melanoma, usually at a young age. The most common genetic alteration, implicated in 40 per cent of FAMMM syndrome families, is a mutation of cyclin-dependent kinase inhibitor 2A (CDKN2A).1 CDKN2A encodes the tumour suppressor gene p16INK4a, a critical cell cycle inhibitor.2 The diagnosis and management of patients with FAMMM syndrome is relevant to the plastic surgeon who manages melanoma. However, clear guidelines on its diagnostic criteria and its relationship to associated but distinct syndromes, such as hereditary melanoma and B-K mole syndrome, are lacking in the extant literature. The aim of this review is to clarify the diagnostic criteria and management principles for FAMMM syndrome. We propose a new system of classifying FAMMM syndrome patients as a subset of all patients with hereditary melanoma. We also present a management algorithm for these distinct patient groups (FAMMM syndrome, hereditary melanoma and germline CDKN2A mutations).

Dysplastic Nevi are a Risk Factor for Uveal Melanoma

Many studies have characterized the phenotypic features of individuals who are likely to develop cutaneous melanoma. One of the major items included in melanoma risk assessment has been the presence of clinically atypical nevi (dysplastic nevi). This study assessed the number of subjects with dysplastic nevi in groups of patients with uveal melanoma or cutaneous melanoma and in a group of volunteer controls. The SPSS program was used to calculate the odds ratios (hereafter called relative risks; RR) and 95% confidence intervals (C) in melanoma patients and controls. The RR was 4.36 for uveal melanoma (95% Cl 1.84-10.36) and 4.22 for cutaneous melanoma (95% Cl 1.81-9.84). These results suggest that cutaneous dysplastic nevi are a significant risk factor for uveal melanoma.

Anatomic Distribution of Cutaneous Melanomas and Painful Sunburns in Adults

Background:

Data show that intermittent painful sunburns are an important causative factor for cutaneous malignant melanoma.

Objective:

This study was undertaken to determine whether the differences in the anatomic distribution of melanomas in men, compared to women, could be accounted for by the distribution of sunburns and whether the high incidence of melanomas on the lower extremities of women is associated with the distribution of sunburns.

Methods:

One hundred and fifty nonmelanoma patients, men and women aged 20 to 60 years, recalled having painful sunburns within the previous 6 months. The locations of the sunburns were indicated on body surface diagrams. The locations of 1168 melanomas as recorded in the NYU-Melanoma Cooperative Group data base were plotted on anatomic diagrams. The anatomic distribution of melanomas and of sunburns for men and women were compared.

Results:

There was no statistically significant difference in the distribution of sunburns on any anatomic location in men as compared to women. However, there was a disproportionately high number of melanomas on the backs of men and on the legs of women. In both men and women, there was a significant difference between the anatomic distribution of painful sunburns and melanomas.

Conclusion:

Since the anatomic distribution of painful sunburns is similar in men and women, whereas the anatomic distribution of melanomas differ, it would appear that factors in addition to sunburns in adults account for the differences in the anatomic distribution of melanomas in men and women.

Importance of polymorphisms in NF-κB1 and NF-κBIα genes for melanoma risk, clinicopathological features and tumor progression in Swedish melanoma patients

PURPOSE

Importance of polymorphisms in NF-kappaB1 and NF-kappaBIalpha genes for melanoma risk, clinicopathological features and tumor progression is analyzed in Swedish melanoma patients.

PATIENTS AND METHODS

Functional polymorphisms of NF-kappaB1 and NF-kappaBIalpha genes were examined in 185 melanoma patients and 438 tumor-free individuals. Associations of the polymorphisms with melanoma risk, age and pigment phenotypes of the patients and clinicopathological tumor characteristics were analyzed. DNAs were isolated from mononuclear cells of venous blood. Polymorphisms of the genes were genotyped by a PCR-RFLP technique, and transcription level of NF-kappaBIalpha was examined by a quantitative real-time reverse transcription PCR.

RESULTS

Both ATTG insertion polymorphism of NF-kappaB1 and A to G polymorphism of NF-kappaBIalpha genes were correlated with melanoma risk, especially, in a combination of ATTG( 2 )/ATTGT(2) and GG. NF-kappaB1 ATTG(2)/ATTG(2) and NF-kappaBIalpha GG genotypes were associated with male gender and age >65 years (at diagnosis). Patients with ATTG(1)/ATTG(1 )genotype had thinner tumors and lower Clark levels at diagnosis. Frequency of ATTG(1)/ATTG(1) genotype was higher in patients with melanomas on intermittently sun-exposed pattern of the body and NF-kappaBIalpha GG was more frequent in the patients with melanomas at rarely exposed sites. There were no differences in the gene transcription level between patients with different NF-kappaBIalpha genotypes.

CONCLUSION

NF-kappaB1 and NF-kappaBIalpha genes might be susceptible genes for melanoma risk and functional polymorphisms of these genes might be biological predictors for melanoma progression.

Mucosal melanomas

Cutaneous malignant melanoma is a common malignancy and has been increasing at an alarming rate in the United States. Sun exposure is a well-known risk factor related to this disease and much is understood regarding the etiology and epidemiology of cutaneous melanomas. In contrast, primary mucosal melanomas represent an extremely rare malignancy and do not have the same risk factors or behavior patterns. They occur in areas that have no sun exposure and solid predisposing risk factors have not been identified, making this disease very difficult to diagnose or screen for. It is usually diagnosed at a later stage and carries a poor prognosis. Identifying the differences between a primary lesion and a metastatic melanoma is often challenging, because of the lack of definitive criteria, both pathologically and clinically. The rich vascular and lymphatic network surrounding these lesions may be responsible for their aggressive behavior and poor prognosis. In addition, the obscure locations where mucosal melanomas occur are an obvious reason why these lesions often go unnoticed until symptoms develop. Recent literature has raised significant questions regarding recommended treatment strategies. Earlier reports advocated radical surgery as the mainstay of therapy; however, local recurrence and survival were unchanged whether radical surgery or local excision was performed, and the most recent data are favoring the conservative approach when appropriate. Unfortunately, a multitude of adjuvant therapies have been tried without any success. Adjuvant radiotherapy plays a role when combined with surgery, particularly in the head and neck region and female genitalia, but this is reserved for nodal and locoregionally advanced disease and has had no effect when used as a prophylactic method. It is difficult to make significant advances in treatment strategies because of the rarity of the disease. As an example, one in 75 persons born in the year 2000 will develop cutaneous melanoma in his lifetime, compared with four cases per ten million people diagnosed with mucosal melanoma per year in the United States. Possible new therapies based on new biologic and immunologic findings may have future promise on being able to impact this disease. Until then, this aggressive tumor continues to have a poor prognosis, and surgical resection continues to be the mainstay of primary therapy.

Significant impact of promoter hypermethylation and the 540 C>T polymorphism of CDKN2A in cutaneous melanoma of the vertical growth phase

Promoter hypermethylation, mutations, and loss of heterozygosity in the CDKN2A gene as well as polymorphisms at the 3'-untranslated region were determined in vertical growth phase melanomas. Methylation-specific polymerase chain reaction in soluti and in situ showed that 19% of the cases were hypermethylated at the CDKN2A promoter region, and some of these cases were heterogeneous with both methylated and unmethylated tumor cells. Methylation was associated with increased tumor cell proliferation by Ki-67 expression (P = 0.01) and decreased patient survival (P = 0.025). Point mutations in CDKN2A were found in 4% of the cases, whereas 90% had loss of heterozygosity at one or more of 4 markers studied. Furthermore, presence of the 540 C>T polymorphism at the 3'-untranslated region of CDKN2A (23%) was associated with improved survival in multivariate analysis (hazard ratio, 2.6; P = 0.02). Our results suggest that promoter methylation of the CDKN2A gene is present in a subgroup of the tumors and associated with increased tumor cell proliferation and reduced survival. Further, the 540 C>T polymorphism might define a distinct subgroup of low-grade vertical growth phase melanomas. These findings support a significant role of the CDKN2A gene in melanoma progression.

Melanoma genetics: an update with focus on the CDKN2A(p16)/ARF tumor suppressors

Investigative interest in atypical nevi and familial melanoma has contributed to the identification of several candidate melanoma loci within the human genome. Molecular defects in both tumor suppressor genes and oncogenes have been pathogenically linked to melanoma in recent studies. Of the loci currently characterized, the major gene resides on chromosome 9p and encodes a tumor suppressor designated p16. This gene, which is also known as CDKN2A, is either mutated or deleted in a large majority of melanoma cell lines, as well as in many uncultured melanoma cells and in the germline of melanoma kindreds. A novel aspect of the p16 locus is that it encodes not just one but two separate gene products that are transcribed in alternative reading frames. Both products function as negative regulators of cell cycle progression. The p16 protein itself executes its effects by competitively inhibiting cyclin-dependent kinase 4, which is a factor necessary for cellular progression through a major regulatory transition of the cell division cycle. Inherited and acquired deletions or point mutations in the p16 gene increase the likelihood that potentially mutagenic DNA damage will escape repair before cell division. Notably, the second product of the locus, ARF (for alternative reading frame), regulates cell growth through independent effects on the p53 pathway. Although there is little evidence that ARF by itself is involved in the pathogenesis of melanoma, deletions at the p16 locus disable two separate pathways that control cell growth. These recent advances open up the possibility of genetic testing for melanoma susceptibility in the setting of familial melanoma and suggest novel therapeutic strategies for melanoma based on gene therapy or small molecule mimicry targeted to the correction of defects in the p16 regulatory pathway. (J Am Acad Dermatol 2000;42:705-22.)

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be familiar with the historical aspects of melanoma genetics and should have a greater understanding of the CDKN2A(p16)/ARF tumor suppressor genes.

The expression of p16(INK4a), the product of a tumor suppressor gene for melanoma, is upregulated in human melanocytes by UVB irradiation

BACKGROUND

The genetic locus CDKN2A has been linked to familial melanoma, and mutations or deletions in its coding sequence are seen in some cases of sporadic and familial melanomas. The protein encoded by CDKN2A, p16(INK4a), functions as a negative regulator of cell cycle progression and as a tumor suppressor, but the regulatory mechanisms involved in controlling its expression remain poorly defined.

OBJECTIVE

This study tested the hypothesis that UVB irradiation, which transiently inhibits the growth of human melanocytes, is one of the regulators of p16(INK4a) expression.

METHODS

Cultured human melanocytes were irradiated with UVB over a sublethal dosage range, and p16(INK4a) protein and mRNA levels were quantified at varying times thereafter by quantitative immunostaining and by Western and Northern blotting.

RESULTS

Levels of p16(INK4a) protein in melanocytes increased significantly after sublethal UVB irradiation as compared with nonirradiated cells. Northern analysis indicated that p16(INK4a) messenger RNA coordinately increased in a dose-dependent manner more than 2-fold in irradiated cells at the tested doses.

CONCLUSION

UVB irradiation transcriptionally activates the expression of p16(INK4a) in cultured human melanocytes. Therefore the growth arrest that occurs with irradiation of melanocytes could be mediated, in part, by upregulation of p16(INK4a). This transient arrest may allow repair of UVB-induced DNA damage before cell division. Conversely, hereditary or acquired defects in CDK4A that give rise to functional insufficiency of p16(INK4a) could permit the premature propagation of melanocytes harboring potentially carcinogenic DNA damage.

Oral mucosal melanoma: epidemiology and pathobiology

The vast majority of healthy individuals have some form of melanocytic lesions with most having several cutaneous melanocytic nevocellular nevi. The incidence of cutaneous melanoma, despite improved prevention and early diagnosis of precursor melanocytic lesions, is on the increase with a projection that one in 75 persons born in the year 2000 will develop cutaneous melanoma in his/her lifetime. With cutaneous melanoma, the number, location and type of nevi, sun exposure and inability to tan, and presence or absence of dysplastic nevi affect transformation to a malignant process. Certain familial factors, syndromes, cytogenetic abnormalities, and mutations in tumor suppressor genes also influence tumor formation. In contrast, mucosal melanoma involving the oral cavity and head and neck regions is not as well understood or characterized. No doubt, this is due to the fact that this subtype of melanoma accounts for less than 1% of all cases. Mucosal melanomas tend to present at a higher stage, are more aggressive, and in a vertical growth phase of disease. A definitive precursor lesion for mucosal melanoma has not been identified; however, atypical melanocytic hyperplasia may represent a proliferative phase before overt tumorigenesis occurs. Melanoma-related antigens, growth factors, and proliferation markers have been identified in cutaneous melanoma, and allow for development of immunotherapy directed against melanoma-associated entities. It is currently possible to evaluate the cytogenetic make-up of precursor melanocytic lesions and frank melanoma, and the constitutional genetic background of individuals at risk for melanoma. No doubt, as concerted investigations of mucosal melanomas of the oral cavity and head and neck evolve, similar factors will be identified which will direct therapy and predict recurrence and survival. In the not too distant future, innovative retroviral transfection, antibodies against specific melanoma-associated factors, vaccination against melanoma, and gene therapy to repair cytogenetic abnormalities and tumor suppressor gene mutations may provide effective therapy and protection against melanomas.

Multiple primary melanoma

BACKGROUND

Incidence rates of cutaneous malignant melanoma (CMM) have been increasing for decades among Caucasian populations worldwide. Multiple factors identify persons at increased risk of CMM, including those with a family history of melanoma and those with atypical moles. Approximately 6-12% of melanomas are familial and approximately 12% of patients with familial melanoma have multiple primary melanomas.

OBJECTIVE

To report a case of a patient with atypical moles and with 17 multiple primary melanomas. To review the literature on multiple primary melanomas as well as to review the genetics and treatment of melanoma.

CONCLUSION

Patients with numerous atypical moles and a family or personal history of melanoma are at greatest risk for developing CMM. Patients from this population tend to develop CMM approximately 10 years earlier than the general population and have an increased risk for developing multiple primary melanomas. Since genetic tests capable of detecting individuals with an inherited susceptibility to CMM are not available, it is important to identify those patients with an increased risk and monitor them closely with regular total-body examinations.

Deletions of the region 17p11-13 in advanced melanoma revealed by cytogenetic analysis and fluorescence in situ hybridization

The significance of the p53 tumour-suppressor gene in the oncogenesis of a variety of malignant tumours has been demonstrated over recent years. However, the role of p53 in human malignant melanoma is still unclear. Therefore, we investigated melanoma metastases from 11 patients cytogenetically and with fluorescence in situ hybridization (FISH) after short-term culture, employing a p53 region-specific probe for 17p13.1 and a probe detecting the centromere of chromosome 17. Furthermore, paraffin-embedded tissue samples from nine of these patients were investigated immunohistochemically for expression of the p53 protein. Deletions of the short arm of chromosome 17 were seen in six melanomas in cytogenetic analysis. With FISH, three malignant melanomas had clones with only one p53-allele and an additional four malignant melanomas showed a reduced number of signals at the p53 tumour-suppressor gene locus compared with signals for the centromeric region of chromosome 17. This was confirmed by immunohistochemistry. Our results suggest that the 17p11-13 region is frequently deleted in malignant melanomas and that p53 or other genes located on this band might contribute to the malignant potential of advanced melanoma.

Expression of the tumor suppressor gene product p16INK4 in benign and malignant melanocytic lesions

The gene MTS1 encodes p16INK4, an inhibitor of cyclin-dependent kinase 4, and is frequently deleted, mutated, or silenced by promoter methylation in melanoma cells and in the germline of familial melanoma patients. Although MTS1 may thus be the candidate melanoma suppressor gene that maps to chromosome 9p21, it is not clear how dysfunction at that locus temporally relates to melanoma progression. To further test its role in sporadic melanoma, the expression of p16INK4-protein and -mRNA was characterized in melanomas and melanocytic nevi by immunocytochemistry and in situ reverse transcriptase-polymerase chain reaction. Histologic tissue sections were immunolabeled with anti-p16INK4 antibody for 108 melanocytic lesions, including common and atypical nevi, in situ melanomas, primary invasive melanomas, and metastatic tumors. A subset of the lesions was analyzed for expression of p16INK4-mRNA, employing forward and reverse intron-bridging primers for reverse transcriptase-polymerase chain reaction amplification of the transcript corresponding to exons 1 and 2 of MTS1. Strong immunolabeling was detected in the melanocytes of common nevi and of nevi with architectural disorder and cytologic atypia. By digital image analysis, in contrast, labeling intensity decreased significantly and progressively in the melanocytes of in situ, invasive, and metastatic melanomas. Results from the in situ reverse transcriptase-polymerase chain reaction analysis were confirmatory, showing a strong signal in the melanocytic nevi but progressive signal attenuation with increasing stage of melanoma. These data indicate correlation between gradual loss of expression of the MTS1 locus and progression of melanoma, further supporting an emerging role for the gene in the malignant transformation of melanocytes. The failure to demonstrate reduced expression in nevi suggests either that these lesions are not an early stage in melanoma development, in contrast to prevailing assumptions, or that loss of p16INK4 function is not an initiating event in melanocyte transformation.

Lower Frequency of Sister Chromatid Exchanges and Altered Frequency of HLA B-region Alleles among Individuals with Sporadic Dysplastic Nevi

Sister chromatid exchanges (SCE) were analyzed in peripheral blood lymphocytes of 24 individuals, following diagnosis, and prior to surgical removal, of a sporadic dysplastic nevus (DN). Lower SCE values and variability were found in 23 sporadic DN individuals compared with controls (2.52+0.12 and 3.76±0.22 SCE/cell, respectively). These DN individuals, contrarily to healthy controls and some types of tumor patients whose cells are hypersensitive to mutagenic agents, did not show increased SCE rates as a consequence of cigarette smoking, alcohol consumption and diagnostic radiation treatments. These observations are in contrast with clinical evidence that similar lesions are both markers or risk and precursors of malignancy in individuals with multiple nevi, affected by the dysplastic nevus syndrome (DNS) or belonging to FMM (familial malignant melanoma) families. Three HLA class I alleles out of 72 tested were found more frequently in sporadic DN individuals compared with controls: B37 (p<0.05), B52 (p<0.01) and B70 (p<0.01). Whether the greater chromosomal stability (as shown by the SCE analysis), and/or the altered frequency of some HLA alleles could influence the chance of developing cutaneous malignancy in DN individuals is yet to be evaluated.

Genomic instability in 1p and human malignancies

Both cytogenetic and molecular genetic approaches have unveiled non-random genomic alterations in 1p associated with a number of human malignancies. These have been interpreted to suggest the existence of cancer-related genes in 1p. Earlier studies had employed chromosome analysis or used molecular probes mapped by in situ hybridization. Further, studies of the various tumor types often involved different molecular probes that had been mapped by different technical approaches, like linkage analysis, radioactive or fluorescence in situ hybridization, or by employing a panel of mouse x human radiation reduced somatic cell hybrids. The lack of maps fully integrating all loci has complicated the generation of a comparative and coherent picture of 1p damage in human malignancies even among different studies on the same tumor type. Only recently has the availability of genetically mapped, highly polymorphic loci at (CA)n repeats with sufficient linear density made it possible to scan genomic regions in different types of tumors readily by polymerase chain reaction (PCR) with a standard set of molecular probes. This paper aims at presenting an up-to-date picture of the association of 1p alterations with different human cancers and compiles the corresponding literature. From this it will emerge that the pattern of alterations in individual tumor types can be complex and that a stringent molecular and functional definition of the role that Ip alterations might have in tumorigenesis will require a more detailed analysis of the genomic regions involved.