CDKN2 explains part of the clinical phenotype in Dutch familial atypical multiple-mole melanoma (FAMMM) syndrome families

Identification of high-risk germline variants for the development of pancreatic cancer: Common characteristics and potential guidance to screening guidelines

Pancreatic cancer (PC) is a product of a variety of environmental and genetic factors. Recent work has highlighted the influence of hereditary syndromes on pancreatic cancer incidence. The purpose of this review is to identify the high-risk syndromes, common variants, and risks associated with PC. The study also elucidates common characteristics of patients with these mutations, which is used to recommend potential changes to current screening protocols for greater screening efficacy. We analyzed 8 syndromes and their respective variants: Hereditary Breast and Ovarian Cancer (BRCA1/2), Familial Atypical Multiple Mole Melanoma Syndrome (CDKN2A), Peutz-Jeghers Syndrome (STK11), Lynch Syndrome (PMS2, MLH1, MSH2, MSH6, EPCAM), Ataxia Telangiectasia (ATM), Li-Fraumeni Syndrome (TP53), Fanconi Anemia (PALB2), and Hereditary Pancreatitis (PRSS1, SPINK1, CFTR). Of 587 studies evaluated, 79 studies fit into our inclusion criteria. Information from each study was analyzed to draw conclusions on these variants as well as their association with pancreatic cancer. Information from this review is intended to improve precision medicine and improve criteria for screening.

PALLD mutation in a European family conveys a stromal predisposition for familial pancreatic cancer

BACKGROUNDPancreatic cancer is one of the deadliest cancers, with low long-term survival rates. Despite recent advances in treatment, it is important to identify and screen high-risk individuals for cancer prevention. Familial pancreatic cancer (FPC) accounts for 4%-10% of pancreatic cancers. Several germline mutations are related to an increased risk and might offer screening and therapy options. In this study, we aimed to identity of a susceptibility gene in a family with FPC.METHODSWhole exome sequencing and PCR confirmation was performed on the surgical specimen and peripheral blood of an index patient and her sister in a family with high incidence of pancreatic cancer, to identify somatic and germline mutations associated with familial pancreatic cancer. Compartment-specific gene expression data and immunohistochemistry were also queried.RESULTSThe identical germline mutation of the PALLD gene (NM_001166108.1:c.G154A:p.D52N) was detected in the index patient with pancreatic cancer and the tumor tissue of her sister. Whole genome sequencing showed similar somatic mutation patterns between the 2 sisters. Apart from the PALLD mutation, commonly mutated genes that characterize pancreatic ductal adenocarcinoma were found in both tumor samples. However, the 2 patients harbored different somatic KRAS mutations (G12D and G12V). Healthy siblings did not have the PALLD mutation, indicating a disease-specific impact. Compartment-specific gene expression data and IHC showed expression in cancer-associated fibroblasts (CAFs).CONCLUSIONWe identified a germline mutation of the palladin (PALLD) gene in 2 siblings in Europe, affected by familial pancreatic cancer, with a significant overexpression in CAFs, suggesting that stromal palladin could play a role in the development, maintenance, and/or progression of pancreatic cancer.FUNDINGDFG SFB 1321.

Families with BAP1-Tumor Predisposition Syndrome in The Netherlands: Path to Identification and a Proposal for Genetic Screening Guidelines

Germline pathogenic variants in the BRCA1-associated protein-1 (BAP1) gene cause the BAP1-tumor predisposition syndrome (BAP1-TPDS, OMIM 614327). BAP1-TPDS is associated with an increased risk of developing uveal melanoma (UM), cutaneous melanoma (CM), malignant mesothelioma (MMe), renal cell carcinoma (RCC), meningioma, cholangiocarcinoma, multiple non-melanoma skin cancers, and BAP1-inactivated nevi. Because of this increased risk, it is important to identify patients with BAP1-TPDS. The associated tumors are treated by different medical disciplines, emphasizing the need for generally applicable guidelines for initiating genetic analysis. In this study, we describe the path to identification of BAP1-TPDS in 21 probands found in the Netherlands and the family history at the time of presentation. We report two cases of de novo BAP1 germline mutations (2/21, 9.5%). Findings of this study combined with previously published literature, led to a proposal of guidelines for genetic referral. We recommend genetic analysis in patients with ≥2 BAP1-TPDS-associated tumors in their medical history and/or family history. We also propose to test germline BAP1 in patients diagnosed with UM <40 years, CM <18 years, MMe <50 years, or RCC <46 years. Furthermore, other candidate susceptibility genes for tumor types associated with BAP1-TPDS are discussed, which can be included in gene panels when testing patients.

CDKN2A Germline Rare Coding Variants and Risk of Pancreatic Cancer in Minority Populations

Background: Pathogenic germline mutations in the CDKN2A tumor suppressor gene are rare and associated with highly penetrant familial melanoma and pancreatic cancer in non-Hispanic whites (NHW). To date, the prevalence and impact of CDKN2A rare coding variants (RCV) in racial minority groups remain poorly characterized. We examined the role of CDKN2A RCVs on the risk of pancreatic cancer among minority subjects.Methods: We sequenced CDKN2A in 220 African American (AA) pancreatic cancer cases, 900 noncancer AA controls, and 183 Nigerian controls. RCV frequencies were determined for each group and compared with that of 1,537 NHW patients with pancreatic cancer. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for both a case-case comparison of RCV frequencies in AAs versus NHWs, and case-control comparison between AA cases versus noncancer AA controls plus Nigerian controls. Smaller sets of Hispanic and Native American cases and controls also were sequenced.Results: One novel missense RCV and one novel frameshift RCV were found among AA patients: 400G>A and 258_278del. RCV carrier status was associated with increased risk of pancreatic cancer among AA cases (11/220; OR, 3.3; 95% CI, 1.5-7.1; P = 0.004) compared with AA and Nigerian controls (17/1,083). Further, AA cases had higher frequency of RCVs: 5.0% (OR, 13.4; 95% CI, 4.9-36.7; P < 0.001) compared with NHW cases (0.4%).Conclusions: CDKN2A RCVs are more common in AA than in NHW patients with pancreatic cancer and associated with moderately increased pancreatic cancer risk among AAs.Impact: RCVs in CDKN2A are frequent in AAs and are associated with risk for pancreatic cancer. Cancer Epidemiol Biomarkers Prev; 27(11); 1364-70. ©2018 AACR.

Germline CDKN2A/P16INK4A mutations contribute to genetic determinism of sarcoma

BACKGROUND

Sarcomas are rare mesenchymal malignancies whose pathogenesis is poorly understood; both environmental and genetic risk factors could contribute to their aetiology.

METHODS AND RESULTS

We performed whole-exome sequencing (WES) in a familial aggregation of three individuals affected with soft-tissue sarcoma (STS) without TP53 mutation (Li-Fraumeni-like, LFL) and found a shared pathogenic mutation in CDKN2A tumour suppressor gene. We searched for individuals with sarcoma among 474 melanoma-prone families with a CDKN2A-/+ genotype and for CDKN2A mutations in 190 TP53-negative LFL families where the index case was a sarcoma. Including the initial family, eight independent sarcoma cases carried a germline mutation in the CDKN2A/p16INK4A gene. In five out of seven formalin-fixed paraffin-embedded sarcomas, heterozygosity was lost at germline CDKN2A mutations sites demonstrating complete loss of function. As sarcomas are rare in CDKN2A/p16INK4A carriers, we searched in constitutional WES of nine carriers for potential modifying rare variants and identified three in platelet-derived growth factor receptor (PDGFRA) gene. Molecular modelling showed that two never-described variants could impact the PDGFRA extracellular domain structure.

CONCLUSION

Germline mutations in CDKN2A/P16INK4A, a gene known to predispose to hereditary melanoma, pancreatic cancer and tobacco-related cancers, account also for a subset of hereditary sarcoma. In addition, we identified PDGFRA as a candidate modifier gene.

The Genes and Genetics of Malignant Melanoma

Background:

Population-based studies have identified several clinical variables associated with an increased risk of developing cutaneous melanoma that include phenotype, amount of and response to sun exposure, and family history. However, these observations are of limited relevance to clinical practice as the risk associated with each factor is individually modest and the characteristics of these variables lack precision when applied to a particular individual.

Objective:

To review the literature regarding recent advances made in the understanding of the genes and genetics of clinical variables associated with an increased risk of melanoma.

Conclusion:

Variants of the MC1R (melanocortin-1 receptor) have been identified as major determinants of high-risk phenotypes, such as red hair and pale skin, and the ability to tan in response to UV exposure. Several studies also suggest that such variants may increase melanoma risk independent of their contribution to phenotype. A strong genetic basis for both nevus density and size has been demonstrated and the link between nevi and the development of MM has become better defined. Finally, germline defects in several genes involved in cell cycle regulation, namely, p16 and CDK4, have been demonstrated in many familial melanoma kindreds. This progress has introduced the prospect of genetic testing as a means of identifying a limited number of high-risk individuals who can be targeted with regular screening and education regarding UV exposure and skin self-examination. Ultimately, through rational genetic therapy targeted to correcting the underlying molecular defect, altering the natural history of melanoma development may be possible.

International consensus guidelines 2012 for the management of IPMN and MCN of the pancreas

The international consensus guidelines for management of intraductal papillary mucinous neoplasm and mucinous cystic neoplasm of the pancreas established in 2006 have increased awareness and improved the management of these entities. During the subsequent 5 years, a considerable amount of information has been added to the literature. Based on a consensus symposium held during the 14th meeting of the International Association of Pancreatology in Fukuoka, Japan, in 2010, the working group has generated new guidelines. Since the levels of evidence for all items addressed in these guidelines are low, being 4 or 5, we still have to designate them "consensus", rather than "evidence-based", guidelines. To simplify the entire guidelines, we have adopted a statement format that differs from the 2006 guidelines, although the headings are similar to the previous guidelines, i.e., classification, investigation, indications for and methods of resection and other treatments, histological aspects, and methods of follow-up. The present guidelines include recent information and recommendations based on our current understanding, and highlight issues that remain controversial and areas where further research is required.

Molecular signatures of pancreatic cancer

CONTEXT

The introduction of genome- and epigenome-wide screening techniques has dramatically improved our understanding of the molecular mechanisms underlying the development of pancreatic cancer. There are now 3 recognized histologic precursors of pancreatic cancer: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions is associated with specific molecular alterations.

OBJECTIVE

To understand the molecular characteristics of pancreatic ductal adenocarcinoma and its precursor lesions.

DATA SOURCES

PubMed (US National Library of Medicine).

CONCLUSIONS

In this review, we briefly summarize recent research findings on the genetics and epigenetics of pancreatic cancer. In addition, we characterize these molecular alterations in the context of the histologic subtypes of pancreatic cancer.

Molecular signatures of pancreatic cancer

CONTEXT

The introduction of genome- and epigenome-wide screening techniques has dramatically improved our understanding of the molecular mechanisms underlying the development of pancreatic cancer. There are now 3 recognized histologic precursors of pancreatic cancer: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions is associated with specific molecular alterations.

OBJECTIVE

To understand the molecular characteristics of pancreatic ductal adenocarcinoma and its precursor lesions.

DATA SOURCES

PubMed (US National Library of Medicine).

CONCLUSIONS

In this review, we briefly summarize recent research findings on the genetics and epigenetics of pancreatic cancer. In addition, we characterize these molecular alterations in the context of the histologic subtypes of pancreatic cancer.

The complexity of pancreatic ductal cancers and multidimensional strategies for therapeutic targeting

The directions of differentiation and the molecular features of ductal pancreatic cancer have by now been explored in reasonable detail. Already, diagnoses and therapeutic strategies benefit from observations distinguishing the major variant types of pancreatic cancer and the differing stages of disease at presentation. Additionally, individual patients differ within each variant type. In certain high-risk groups, this permits focused screening efforts. The tumorigenic influences that characterize individual patients are increasingly considered appropriate in defining clinical treatment plans. As a result, multiple variables affect success when individualizing screening or therapy. These competing variables often limit the potential for success: some variables dominate and should receive greater consideration than others. Simplistic expectations, often falsely optimistic, for individualized care may fail to 'pan out' in the real world. The development of individualized care will be efficient only when the full complexity of the disease is embraced.

Familial cutaneous melanoma

Approximately 5-10 % of all cutaneous melanomas occur in families with hereditary melanoma predisposition. Worldwide, approximately 20-40% of kindreds with familial elanoma harbor germline mutations in the CDKN2A gene, located on chromosome 9p21, which encodes two different proteins, p16INK4 and p14ARF, both involved in regulation of cell cycle progression and induction of senescence. In different populations several recurring CDKN2A founder mutations have been described. The risk of melanoma in CDKN2A mutations carriers varies between populations and is higher in regions with high sun exposure and high incidence of melanoma in the general population. Some CDKN2A mutations have been associated not only with melanoma but also with increased risk of other malignancies--most notably pancreatic carcinoma. A much smaller number of families have germline mutations in the CDK4 gene on chromosome 12q14, encoding a cyclin dependent kinase which normally interacts with p16INK4A. The management of families with hereditary melanoma is discussed.

Clinical and genetic analysis of 18 pancreatic carcinoma/melanoma-prone families

Families with both melanoma and pancreatic cancer are extremely rare and some are affected with the autosomal dominant inherited familial atypical multiple mole melanoma-pancreatic cancer (FAMMM-PC) syndrome. The phenotypic and genotypic expressions of such pancreatic cancer-melanoma prone families are not well defined. The National Case Collection of Familial Pancreatic Cancer of the Deutsche Krebshilfe includes 110 pancreatic cancer families, 18 of which (16%) show an association of pancreatic cancer and melanoma. These 18 families were analysed regarding their phenotype and the prevalence of germline mutations in the candidate genes CDKN2A, BRCA2, CHEK2, NOD2, ARL11 and Palladin (PALLD). There were two types of families: five families with the FAMMM-PC phenotype and 13 PC/melanoma families without the multiple mole phenotypes (PCMS). The prevalences of PC and melanoma in the two types of families were similar. The prevalence of other tumour types, especially breast carcinoma, was higher (11%) in PCMS- than in FAMMM-PC families (2.4%, p = 0.02). CDKN2A mutations were identified in 2 of 18 (11%) PCMS families. A cosegregating BRCA2 mutation was detected in one PCMS family without breast cancer. None of the reported germline mutations in the NOD2, Palladin, ARL11 or CHEK2 genes were detected in either type of family. In conclusion, families with an accumulation of PC and melanoma show a large variety of phenotypic expression, which is not always consistent with the FAMMM-PC phenotype. More PC/melanoma-prone families need to be analysed to clarify whether such families represent variations of the FAMMM-PC syndrome or two distinct hereditary cancer syndromes.

Selection criteria for genetic assessment of patients with familial melanoma

Approximately 5% to 10% of melanoma may be hereditary in nature, and about 2% of melanoma can be specifically attributed to pathogenic germline mutations in cyclin-dependent kinase inhibitor 2A (CDKN2A). To appropriately identify the small proportion of patients who benefit most from referral to a genetics specialist for consideration of genetic testing for CDKN2A, we have reviewed available published studies of CDKN2A mutation analysis in cohorts with invasive, cutaneous melanoma and found variability in the rate of CDKN2A mutations based on geography, ethnicity, and the type of study and eligibility criteria used. Except in regions of high melanoma incidence, such as Australia, we found higher rates of CDKN2A positivity in individuals with 3 or more primary invasive melanomas and/or families with at least one invasive melanoma and two or more other diagnoses of invasive melanoma and/or pancreatic cancer among first- or second-degree relatives on the same side of the family. The work summarized in this review should help identify individuals who are appropriate candidates for referral for genetic consultation and possible testing.

Genome-wide linkage scan for atypical nevi in p16-Leiden melanoma families

In most Dutch melanoma families, a founder deletion in the melanoma susceptibility gene CDKN2A (which encodes p16) is present. This founder deletion (p16-Leiden) accounts for a significant proportion of the increased melanoma risk. However, it does not account for the Atypical Nevus (AN) phenotype that segregates in both p16-Leiden carriers and non-carriers. The AN-affected p16-Leiden family members are therefore a unique valuable resource for unraveling the genetic etiology of the AN phenotype, which is considered both a risk factor and a precursor lesion for melanoma. In this study, we performed a genome-wide scan for linkage in four p16-Leiden melanoma pedigrees, classifying family members with five or more AN as affected. The strongest evidence for an atypical nevus susceptibility gene was mapped to chromosome band 7q21.3 (two-point LOD score=2.751), a region containing candidate gene CDK6.

New founder germline mutations of CDKN2A in melanoma-prone families and multiple primary melanoma development in a patient receiving levodopa treatment

Germline mutations in the CDKN2A gene have been shown to predispose individuals to cutaneous malignant melanoma. Here, we describe three melanoma-prone families and one isolated patient affected by multiple melanoma who carried a tandem germline mutation of CDKN2A at the nucleotide level, [c.339G>C;c.340C>T], [p.Leu113Leu;p.Pro114Ser]. We also describe three other melanoma-prone families that carried a missense germline CDKN2A mutation, c.167G>T, p.Ser56Ile. All these families and patients resided in southeast France. We analyzed six 9p21 markers where the CDKN2A gene is located and found that carrier haplotypes for both mutations were consistent with two respective common founder ancestors. In one family, we identified two fourth-degree relatives homozygous for the Ser56Ile mutation, indicating a possible consanguinity. Furthermore, we observed that a carrier of the founder CDKN2A [p.Leu113Leu;p.Pro114Ser] mutation as well as two MC1R moderate-risk variants, [p.Arg151Cys(+)p.Arg163Gln] developed 22 primary melanomas in the three years that followed initiation of levodopa therapy for Parkinson's disease. This observation suggests that there is a need for reconsideration of the hypothesis that levodopa may play a role in melanoma development, at least when in the context of a high-risk genetic background.

Genotype/phenotype of familial pancreatic cancer

It is estimated that 5% to 10% of pancreatic cancer cases are attributable to hereditary factors. We believe that the number of cases that are genetic in etiology are even greater, however, based not on a classic autosomal dominant pattern of inheritance but rather when one takes into account low-penetrant inherited susceptibility factors. There is also a growing recognition that the development of pancreatic cancer in pancreatic cancer-prone families is dependent not only on genetic variables but on nongenetic factors. The aim of this article is to review the challenges in identifying pancreatic cancer-prone families and how environmental factors interact with genetic factors in these families.

Hereditary melanoma and predictive genetic testing: why not?

BACKGROUND

Since p16-Leiden presymptomatic testing for hereditary melanoma has become available in the Netherlands, the benefits and risks of offering such testing are evaluated. The current paper investigated why the non-participants were reluctant to participate in genetic testing.

METHODS

Sixty six eligible individuals, who were knowledgeable about the test but had not participated in genetic testing by January 2003, completed a self-report questionnaire assessing motivation, anxiety, family dynamics, risk knowledge and causal attributions.

RESULTS

Non-participants reported anxiety levels below clinical significance. A principal components analysis on reasons for non-participation distinguished two underlying motives: emotional and rational motivation. Rational motivation for non-participation was associated with more accurate risk knowledge, the inclination to preselect mutation carriers within the family and lower scores on anxiety. Emotional motivation for non-participation was associated with disease misperceptions, hesitation to communicate unfavourable test results within the family and higher scores on anxiety.

CONCLUSION

Rational and emotional motivation for non-participation in the genetic test for hereditary melanoma was found. Emotionally motivated individuals may be reluctant to disseminate genetic risk information. Rationally motivated individuals were better informed than emotionally motivated individuals. It is suggested that a leaflet is added to the invitation letter to enhance informed decision-making about genetic testing.

Cutaneous melanoma: family screening and genetic testing

The incidence of cutaneous melanoma (CM) has been steadily increasing in recent decades. Ultraviolet radiation (UVR) exposure, in the form of intermittent heavy exposure and severe sunburns in childhood, is believed to be the most important environmental contribution to CM risk. Genetic determinants also modulate CM risk, probably to a greater extent than environmental exposure. Certain heritable traits such as prominent numbers of common and atypical melanocytic nevi, skin type, dense UVR-induced freckling, and hair color are all known to be associated with increased CM risk. Very rarely, a heritable mutation in a high-risk gene renders the susceptible individual at extreme risk for CM. Families may carry one or more of the other high-risk phenotypic traits leading to uncertainty about how to quantify CM risk and provide management recommendations. Commercial genetic testing for the known high-risk inherited genetic mutations is available but is only relevant for those rare families likely to be carrying identifiable mutations. CM screening and risk intervention programs are being established internationally for families at markedly increased risk. Algorithms based on the level of risk are proposed.

Aberrant DNA Methylation in Cutaneous Malignancies

In recent years it has become evident that in addition to genetic mutations also epigenetic alterations are causally related to the development and progression of cancer. The epigenetic mechanism most relevant in the pathogenesis of cancer appears to be aberrant methylation of tumor-suppressor gene promoters associated with transcriptional downregulation. Malignancies arising in the skin are the most prevalent in humans. The most common are basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (SCC), melanoma, and cutaneous lymphoma. The visibility and accessibility of cutaneous tumors facilitate the scientific study of sequential epigenetic alterations occurring during tumorigenesis and might make treatment of malignant skin lesions using locally applied demethylating agents possible. In this review, we summarize the current knowledge concerning alterations of DNA methylation in BCC, SCC, melanoma, and cutaneous lymphoma. Furthermore, the potential "epigenotoxic" effects of ultraviolet radiation, an environmental carcinogen implicated in the tumorigenesis of most cutaneous malignancies, will be discussed. From the limited number of investigations of promoter hypermethylation in cutaneous malignancies, it is already clear that a great number of potential tumor-suppressor genes are epigenetically silenced in skin cancer, including components of signaling pathways critical in the pathogenesis of these malignancies.

Risk factors for pancreatic adenocarcinoma: are we ready for screening and surveillance?

Of all common malignancies, pancreatic cancer has the lowest survival rate. According to estimates by the American Cancer Society, in 2004, 31,860 Americans were diagnosed, and 31,270 died from this near universally lethal disease. Unfortunately, only a small minority of patients are diagnosed when the extent of disease is still localized and thus potentially curable. These dismal survival results could be improved by developing successful screening and prevention strategies. Routine screening is not currently suggested for pancreatic cancer; however, there may be a benefit in a select group of patients identified to be at high risk for developing this disease. It is recommended that surveillance be performed on these high-risk individuals in a research setting to allow for the development of a successful detection strategy.

CDKN2A Common Variants and Their Association with Melanoma Risk: A Population-Based Study

The population frequencies of the CDKN2A variants remain undetermined. In Poland there are three common variants of CDKN2A: an alanine to threonine substitution (A148T), Nt500c&gt;g and Nt540c&gt;t, which have been detected in other populations. To establish if they are associated with an increased malignant melanoma (MM) risk we did an association study based on genotyping 471 patients with MM and 1,210 random control subjects from the same Polish population. We found a significantly increased frequency of the A148T variant among patients with MM (7.0%) in comparison with the general population (2.9%). The incidence of the A148T variant remained greater in both unselected and familial melanoma subgroups. A statistically significant positive association was seen for unselected MM (odds ratio, 2.529; P = 0.0003), especially in patients diagnosed under 50 years of age (odds ratio, 3.4; P = 0.0002). The A148T carrier population (heterozygous G/A alleles) was more likely to have a relative with malignancy compared with the noncarrier population (57% versus 36%, respectively; P = 0.03). Further examination of the CDKN2A promoter sequence done in 20 melanoma patients with the A148T change (heterozygous G/A alleles) and 20 patients with MM without this alteration identified it was in linkage disequilibrium with a polymorphism in the promoter region at position P-493. We found no statistically significant overrepresentation of the Nt500c&gt;g and the Nt540c&gt;t polymorphisms in the Polish melanoma population. In conclusion, the A148T variant of the CDKN2A gene seems to be associated with an increased risk of development of MM. Additional studies are required to confirm whether this particular change is associated with increased risk of other nonmelanoma malignancies.

Identification of high-risk pancreatic cancer-prone families

Pancreatic cancer-prone families provide a unique resource for studying the etiology, natural history, genetics, and treatment of pancreatic cancer. The only effective way of identifying these families is by obtaining a complete family history, since it is not possible to differentiate sporadic pancreatic cancer cases from hereditary cases based on either clinical presentation or features. These families also would benefit greatly from early detection or prevention strategies. Ultimately, this knowledge could be applied to the more common sporadic form of pancreatic cancer, where diagnosis is almost always late, and prognosis remains quite grim.

Influence of Genes, Nevi, and Sun Sensitivity on Melanoma Risk in a Family Sample Unselected by Family History and in Melanoma-Prone Families

BACKGROUND

Few family studies have investigated the effects of genetic, environmental, and host factors on melanoma risk, and most have been restricted to high-risk families. We assessed the role of these factors on melanoma risk in two types of families: families ascertained through melanoma probands but unselected by family history and melanoma-prone families.

METHODS

Data on pigmentary traits, nevus phenotypes, exposure to sun, and reactions to sunlight were collected from 295 families unselected by family history and 53 melanoma-prone families. We modeled melanoma risk using a logistic regressive model incorporating the effect of a melanoma-predisposing gene, familial dependence, and potential risk factors (e.g., pigmentary traits, nevus phenotypes, history of sun exposure, skin reactions to sunlight). Maximum-likelihood estimates of the parameters of the regressive model were used to compute odds ratios associated with each risk factor and age-specific melanoma risk depending on the genotype at the melanoma-predisposing gene and the effects of risk factors. All statistical tests were two-sided.

RESULTS

In the families unselected by family history, there was statistically significant evidence (P<.001) for a dominant gene, with melanoma risk reaching 0.49 and 0.67 by age 80 years in male and female gene carriers, respectively. Melanoma risk was statistically significantly influenced by total nevi (odds ratio of hazard function [OR] = 5.81, 95% confidence interval [CI] = 3.47 to 8.99), sun exposure (OR = 5.37, 95% CI = 4.44 to 6.36), and sunburn interacting with the gene (OR = 26.31, 95% CI = 7.56 to 99.22 in gene carriers and OR = 1.67, 95% CI = 1.36 to 2.03 in noncarriers). Twenty of the 53 melanoma-prone families had cosegregating mutations in CDKN2A, a gene known to be associated with melanoma. In these 53 families, three risk factors in addition to CDKN2A mutations increased melanoma risk: dysplastic nevi (OR = 2.32, 95% CI = 2.08 to 2.58), total nevi (OR = 1.99, 95% CI = 1.61 to 2.20) and sunburn (OR = 5.16, 95% CI = 4.82 to 5.52).

CONCLUSIONS

Together, a melanoma-predisposing gene (identified as being CDKN2A in melanoma-prone families), number of nevi and/or dysplastic nevi, and sun-related covariates influence melanoma risk in both families unselected by family history and melanoma-prone families.

Familial melanoma: a complex disorder leading to controversy on DNA testing

The initial enthusiasm generated by the discovery of the first susceptibility gene found for melanoma has slightly dampened over recent years. For the majority of melanoma families the underlying gene defect is still not known, so the search for other melanoma genes is continuing. Also, the increased risk of melanoma does not seem to be restricted to mutation carriers, but is present even in non-mutation carriers in melanoma families. The underlying defect of familial melanoma is less straightforward than previously thought; both environmental and hereditary risk modifiers intermingle in a perplexing way. This makes familial melanoma a complex disorder which deserves the close attention of both clinicians and researchers, especially as the opinion on gene testing in familial melanoma has not yet achieved consensus. On the one hand, there is a rising demand from families for genetic testing; on the other hand, there is the clinicians' concern about the value of such testing.

Melanoma and the Problem of Malignancy

Of the overt biological properties exhibited by malignant cells two appear to command particular attention; these are (1) the transmigratory ability which empowers these cells to invade surrounding tissues and results in their metastatic and destructive potential, and (2) their ability to evade detection by the immune system of the host. Both of these characteristics may well involve several disparate mechanisms. However, it may be that there are some metabolic features that are common to malignant neoplasms which could go some way to explaining one of these behavioural anomalies. It is proposed that abnormalities of oxidative metabolism of cancer cells, resulting in the generation of reactive oxygen species, are responsible for the inhibition of the functions of vicinal antigen-presenting cells and, thus, the failure of the immune system to recognize tumour-specific antigens likely to be expressed by malignant cells as part of their transmigratory capability.

Germline splicing mutations of CDKN2A predispose to melanoma

Coding mutations of the CDKN2A gene on chromosome 9p21 cosegregate with 25-60% of familial melanoma cases, but there remains a number of 9p21-linked kindreds that lack germline coding mutations of CDKN2A. We sequenced CDKN2A exons 1alpha, 2, 3, and the adjacent intronic regions in 167 melanoma-prone families (at least two affected first-degree relatives), and detected four splice site variations, three of which cosegregate with the disease. RT-PCR experiments verified that these three variants, including an AGgt to ATgt mutation that demonstrates a founder effect, do affect splicing. While an exon 1alpha splice donor site mutation incompletely abolishes splicing, the correctly spliced mRNA yields a protein (Q50P) that cannot effectively interact with CDK4. We also performed RT-PCR on mRNA from 16 melanoma-prone kindreds to search for cryptic splice sites deep within introns, but identified no splice variants. Meanwhile, we screened 139 affected families using allele-specific PCR for the recently discovered IVS2-105A>G mutation, but found only one family that possesses this alteration. We conclude that splice site mutations do predispose to disease in a subset of melanoma-prone kindreds. Characterization of additional splice site variants and other noncoding alterations of CDKN2A should allow us to detect a wider range of mutations in at-risk patients.

Genetics of melanoma predisposition

Predisposition to melanoma is genetically heterogeneous. Two high penetrance susceptibility genes, CDKN2A and CDK4, have so far been identified and mapping is ongoing to localize and identify others. With the advent of a catalogue of millions of potential DNA polymorphisms, attention is now also being focused on identification of genes that confer a more modest contribution to melanoma risk, such as those encoding proteins involved in pigmentation, DNA repair, cell growth and differentiation or detoxification of metabolites. One such pigmentation gene, MC1R, has not only been found to be a low penetrance melanoma gene but has also been shown to act as a genetic modifier of melanoma risk in individuals carrying CDKN2A mutations. Most recently, an environmental agent, ultraviolet radiation, has also been established as a modifier of melanoma risk in CDKN2A mutation carriers. Hence, melanoma is turning out to be an excellent paradigm for studying gene-gene and gene-environment interactions.

Melanoma etiology: where are we?

Melanoma incidence rates are rising rapidly, particularly in older men. Older men are also more likely to have thick melanomas, which confer high mortality and morbidity. The reasons for the rate of increase are not known; increasing sun and UV exposure, however, is the major hypothesized explanation. In the past several years, two major susceptibility genes for melanoma, CDKN2A and CDK4, have been identified, but the two genes together account for a minority of familial melanoma. Other high-risk susceptibility genes are being sought actively. Genetic epidemiologic studies suggest that penetrance of each of the two identified genes is altered by other factors, either genetic or environmental. Epidemiologic studies have also identified other major host factors important in the development of melanoma. In European, North American, and Australian populations, the presence of clinically identified dysplastic nevi confers greatly increased risk of melanoma. A new measure of sun exposure, based on individual residential history, confers substantially increased risk of melanoma. Recent surveys of sun behavior in the US reveal extensive sunburning and use of tanning beds in adolescents and adults. Sun protective behaviors are not as prevalent as in Australia, where population rates of melanoma are stabilizing.

Homozygous germline mutation of CDKN2A/p16 and glucose-6-phosphate dehydrogenase deficiency in a multiple melanoma case

CDKN2A is regarded as a major melanoma susceptibility gene. A 19 bp deletion has been detected within Dutch families with familial atypical multiple mole-melanoma syndrome. Genetic analysis revealed two individuals with germline deletions in both copies of CDKN2A. One of them did not develop atypical naevi or melanoma, but died of adenocarcinoma at the age of 54 years. This report describes the results of the investigation of the second p16-null individual, who was also found to have glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and who has developed many atypical naevi and seven melanomas. Using electron microscopic techniques, striking alterations in melanosomal structures and deviations in their sulphur, iron and calcium composition indicating a strong preference for phaeomelanogenesis and increased oxidative stress were found in the naevus cells of the patient. Using an in vitro model, we demonstrated that leaking melanin precursors may strongly enhance oxidative DNA damage through iron release from ferritin. We conclude that the homozygous p16 deletion is not sufficient for the development of a dysplastic naevus phenotype and melanoma. However, when an additional modifying factor, such as G-6-PD deficiency, increases the level of oxidative DNA damage in melanin-producing cells, the risk of developing atypical naevi and their malignant transformation may increase significantly.

Is there a role for genetic testing in patients with melanoma?

Autosomal dominant inheritance of mutations in the locus or the gene may confer a high risk of cutaneous melanoma development. The penetrance of mutations is influenced by UV exposure. Inherited variants in the melanocortin-1 receptor also confer increased risk of cutaneous melanoma. Features associated with increased genetic susceptibility to cutaneous melanoma include the presence of multiple affected first-degree relatives on one side of the family, multiple primary melanomas in the same individual, earlier age of onset, and the presence of multiple atypical nevi, but none of these factors reliably predicts for the presence of mutations. It is currently premature to offer predictive DNA testing for melanoma outside of defined research protocols. This is because of (1). the low likelihood of finding mutations in known melanoma susceptibility genes, even in more than 60% of melanoma-prone kindreds; (2). the broad confidence limits on current estimates of lifetime penetrance of mutations and the wide variation in this penetrance with locality; (3). a high "background" incidence of melanoma in non-mutation carriers in melanoma-prone families; (4). current uncertainties about the factors determining the functionality and phenotypic expression of the trait among carriers of these mutations (penetrance), even if found; and (5). the lack of proved efficacy of melanoma prevention and surveillance strategies, even for mutation carriers. Rather than singling out those deemed to be at high risk because of family history, all patients carrying risk factors for cutaneous melanoma should be subject to stringent programs of sun protection and skin surveillance.

eMelanoBase: an online locus-specific variant database for familial melanoma

A proportion of melanoma-prone individuals in both familial and non-familial contexts has been shown to carry inactivating mutations in either CDKN2A or, rarely, CDK4. CDKN2A is a complex locus that encodes two unrelated proteins from alternately spliced transcripts that are read in different frames. The alpha transcript (exons 1alpha, 2, and 3) produces the p16INK4A cyclin-dependent kinase inhibitor, while the beta transcript (exons 1beta and 2) is translated as p14ARF, a stabilizing factor of p53 levels through binding to MDM2. Mutations in exon 2 can impair both polypeptides and insertions and deletions in exons 1alpha, 1beta, and 2, which can theoretically generate p16INK4A-p14ARF fusion proteins. No online database currently takes into account all the consequences of these genotypes, a situation compounded by some problematic previous annotations of CDKN2A-related sequences and descriptions of their mutations. As an initiative of the international Melanoma Genetics Consortium, we have therefore established a database of germline variants observed in all loci implicated in familial melanoma susceptibility. Such a comprehensive, publicly accessible database is an essential foundation for research on melanoma susceptibility and its clinical application. Our database serves two types of data as defined by HUGO. The core dataset includes the nucleotide variants on the genomic and transcript levels, amino acid variants, and citation. The ancillary dataset includes keyword description of events at the transcription and translation levels and epidemiological data. The application that handles users' queries was designed in the model-view-controller architecture and was implemented in Java. The object-relational database schema was deduced using functional dependency analysis. We hereby present our first functional prototype of eMelanoBase. The service is accessible via the URL www.wmi.usyd.edu.au:8080/melanoma.html.

CDKN2A germline mutations in familial pancreatic cancer

OBJECTIVE

To evaluate the prevalence of mutations in the CDKN2A gene encoding p16 and p14 in familial pancreatic cancer (FPC).

SUMMARY BACKGROUND DATA

The genetic basis of FPC is still widely unknown. Recently, it has been shown that germline mutations in the p16 tumor suppressor gene can predispose to pancreatic cancer. The presence of p14 germline mutations has yet not been determined in this setting.

METHODS

Eighteen families with at least two first-degree relatives with histologically confirmed pancreatic cancer and five families with at least one patient with pancreatic cancer and another first-degree relative with malignant melanoma of the German National Case Collection for Familial Pancreatic Cancer were analyzed for CDKN2A germline mutations including p16 and p14 by direct DNA sequencing. All participating family members were genetically counseled and evaluated by a three-generation pedigree.

RESULTS

None of 18 FPC families without malignant melanoma revealed p16 mutations, compared to 2 of 5 families with pancreatic cancer and melanoma. Truncating p16 germline mutations Q50X and E119X were identified in the affected patients of pancreatic cancer plus melanoma families. None of the 23 families revealed p14 germline mutations.

CONCLUSIONS

CDKN2A germline mutations are rare in FPC families. However, these data provide further evidence for a pancreatic cancer-melanoma syndrome associated with CDKN2A germline mutations affecting p16. Thus, all members of families with combined occurrence of pancreatic cancer and melanoma should be counseled and offered screening for p16 mutations to identify high-risk family members who should be enrolled in a clinical screening program.

Phenotypic variation in eight extended CDKN2A germline mutation familial atypical multiple mole melanoma-pancreatic carcinoma-prone families: the familial atypical mole melanoma-pancreatic carcinoma syndrome

BACKGROUND

Hereditary pancreatic carcinoma shows extant phenotypic and genotypic heterogeneity as evidenced by its integral association with a variety of hereditary cancer syndromes inclusive of the familial atypical multiple mole melanoma (FAMMM) syndrome in concert with CDKN2A (p16) germline mutations.

METHODS

Creighton University's familial pancreatic carcinoma resource comprises 159 families of which 19 (12%) show the FAMMM cutaneous phenotypes. The authors describe eight families with the FAMMM-pancreatic carcinoma (FAMMM-PC) association in concert with a CDKN2A germline mutation. Each family was thoroughly educated about all facets of the study, including the molecular genetics, reduced penetrance of CDKN2A mutations, and their variable expressivity. Genetic counseling was provided to each patient.

RESULTS

Diversity in cancer presentation within and among the families was noteworthy, wherein melanoma predominated in certain of the families whereas pancreatic carcinoma predominated in others. Early-onset pancreatic carcinoma (at ages 35, 45, 46, and 49 years) appeared in some of the families whereas markedly later-onset pancreatic carcinoma occurred in others. There were four incidences of melanoma and pancreatic carcinoma as double primaries in the same individuals. One patient with melanoma and pancreatic carcinoma had a third primary of breast carcinoma. Another patient had sarcoma, esophageal carcinoma, and two melanoma primaries, whereas his daughter had sarcoma and was a carrier of a CDKN2A mutation.

CONCLUSIONS

The authors suggest that these tumors may collectively, in concert with CDKN2A mutations, constitute a "new" putative hereditary carcinoma syndrome referred to as FAMMM-PC. More clinical and molecular genetic research on additional families with pancreatic carcinoma in concert with the FAMMM will be required.

Melanocortin-1 receptor variant R151C modifies melanoma risk in Dutch families with melanoma

Germline mutations of the cell-cycle regulator p16 (also called "CDKN2A") in kindreds with melanoma implicate this gene in susceptibility to malignant melanoma. Most families with familial atypical multiple-mole melanoma (FAMMM) who are registered at the Leiden dermatology clinic share the same p16-inactivating deletion (p16-Leiden). Incomplete penetrance and variable clinical expression suggest risk modification by other genetic and/or environmental factors. Variants of the melanocortin-1 receptor (MC1R) gene have been shown to be associated with red hair, fair skin, and melanoma in humans. Carriers of the p16-Leiden deletion in Dutch families with FAMMM show an increased risk of melanoma when they also carry MC1R variant alleles. The R151C variant is overrepresented in patients with melanoma who are from families with the p16-Leiden mutation. Although some of the effect of the R151C variant on melanoma risk may be attributable to its effect on skin type, our analyses indicate that the R151C variant contributes an increased melanoma risk even after statistical correction for its effect on skin type. These findings suggest that the R151C variant may be involved in melanoma tumorigenesis in a dual manner, both as a determinant of fair skin and as a component in an independent additional pathway.

Haplotype analysis and age estimation of the 113insR CDKN2A founder mutation in Swedish melanoma families

Germline mutations in the CDKN2A tumor suppressor gene located on 9p21 have been linked to development of melanomas in some families. A germline 3-bp insertion in exon 2 of CDKN2A, leading to an extra arginine at codon 113 (113insR), has been identified in 17 Swedish melanoma families. Analysis of 10 microsatellite markers, spanning approximately 1 Mbp in the 9p21 region, showed that all families share a common allele for at least one of the markers closest to the CDKN2A gene, suggesting that the 113insR mutation is an ancestral founder mutation. Differences in the segregating haplotypes, due to meiotic recombinations and/or mutations in the short-tandem-repeat markers, were analyzed further to estimate the age of the mutation. Statistical analysis using a maximum likelihood approach indicated that the mutation arose 98 generations (90% confidence interval: 52-167 generations), or approximately 2,000 years, ago. Thus, 113insR would be expected to have a more widespread geographic distribution in European and North American regions with ancestral connections to Sweden. Alternatively, CDKN2A may lie in a recombination hot spot region, as suggested by the many meiotic recombinations in this narrow approximately 1-cM region on 9p21.

Update on familial pancreatic cancer

Approximately 5% to 10% of patients with pancreatic cancer have one or more first-degree relatives with this disease. A subset of these individuals have a hereditary form of pancreatic cancer designated by association with such hereditary disorders as familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, hereditary pancreatitis, or familial atypical multiple mole melanoma (FAMMM) syndrome. A subset of those FAMMM kindred with the CDKN2A (p16) germline mutation that expresses both pancreatic cancer and malignant melanoma may constitute a new hereditary pancreatic cancer-prone syndrome.

The FAMMM syndrome: epidemiology and surveillance strategies

Research into the epidemiology of the melanoma-prone FAMMM syndrome, molecular genetics of the occurrences of melanoma, the photobiology of DNA damage/repair, diagnostic epiluminescence, microscopic/imaging techniques, and a new concept of photoprotection have altered melanoma strategies in surveillance and prevention. Molecular genetic research has implicated the importance of hereditary aspects of melanoma and associated malignancies. High-risk pedigrees can be identified through an informatic analysis of the occurrence patterns of melanoma and systemic cancers in kindreds. All ultraviolet radiation results in cutaneous DNA damage and in high-risk individuals may cause melanoma. We may reverse the epidemic trend in melanoma occurrences in these high-risk pedigrees if we are willing to change our cultural approach to sunlight exposure with restrictive sunlight behavior, wearing of ultraviolet protective clothes, the use of broad-spectrum ultraviolet protection from nightly topical dihydroxyacetone coupled with daytime UVB sunscreens, and periodic surveillance.

Responses to ultraviolet-B in cell lines from hereditary melanoma kindreds

Ultraviolet-B (UV-B) triggers a cascade of events involving cell cycle control genes leading ultimately to DNA repair or apoptosis. The hypothesis examined here is that the genetic abnormality predisposing to melanoma affects the ability of the cell to respond appropriately to UV-B, so favouring mutagenesis. Epstein-Barr virus-transformed lymphoblastoid cell lines from hereditary melanoma kindreds were irradiated with UV-B, and changes in p53, p21 and Bcl-2 expression and cell cycle phase distribution were analysed. Twenty-two cell lines were tested: 12 carriers of melanoma susceptibility and 10 non-carriers (unaffected first degree relatives). At 24 h after irradiation with 50 J/m2, 15 of the 22 cell lines showed a rise in G2/M. After 400 J/m2, all the cell lines showed a reduction or loss of G2/M and 17 of the 22 showed an S phase delay. More carriers than noncarriers of melanoma susceptibility showed significant S phase delay after 50 J/m2 (seven out of 12 carriers versus two out of 10 non-carriers). Six of the 10 pairs (carrier versus non-carrier) tested showed discordant cell cycle responses; however the nature of the difference was not universal. Bcl-2 reduction was seen 4 h post-irradiation in all the carriers and non-carriers. The p53 and p21 responses, although showing some individual variations, were not related to carrier status. These results show individual variations in response to UV-B irradiation among cell lines from the members of hereditary melanoma kindreds, but no consistent differences between carriers and non-carriers of melanoma susceptibility.

Genetic counseling and testing for germline p16 mutations in two pancreatic cancer-prone families

The mortality from pancreatic cancer coincides closely with its incidence, indicating a dismal outlook. Hereditary factors probably account for approximately 5%-10% of the pancreatic cancer burden. The molecular genetic etiology of pancreatic cancer is only beginning to be identified. We describe our genetic counseling experience with 2 large families prone to pancreatic cancer-malignant melanoma in which p16 (CDKN2) germline mutations had been identified. Members of each family underwent intensive counseling before and at the time of disclosure of p16 germline mutation findings. Two non-cancer-affected siblings from each of the 2 families had p16 mutations identified in DNA from their peripheral blood lymphocytes. In each case, a parent affected with pancreatic cancer also harbored the p16 mutation identified in DNA from their respective tumor blocks. The sibling pairs stated that they would seriously consider prophylactic pancreatectomy if biomarkers or imaging findings suggested a precancerous state. Our experience highlights limited options for managing these families and emphasizes the need for better tools to diagnose pancreatic cancer at a curable stage.

Genetics of familial and sporadic melanoma

Like many other cancers, melanoma has a significant genetic basis. However, its genetic pathways may involve multiple genes with probable interactions with sun exposure. Germline mutations in p16 or CDKN2A are found in a significant percentage of relatively rare melanoma families but p16 mutations are uncommon in sporadic tumours. p16 may still be involved by other mechanisms of inactivation; however, it is clear that other melanoma genes remain to be discovered. Family, case-control, twin and sib-pair analyses as well as DNA chip technology may shed some light on genes involved in melanocytic differentiation and skin pigmentation. Recent public health campaigns have not been very successful in changing behaviour regarding tanning, and the relationship between sun exposure and melanoma is very complex. With the understanding of genetic alterations leading to this tumour, follow-up strategies and behavioural interventions may be more specifically designed to target high risk groups.

Haplotype analysis of two recurrent CDKN2A mutations in 10 melanoma families: evidence for common founders and independent mutations

Germ-line mutations in CDKN2A have been shown to predispose to cutaneous malignant melanoma. We have identified 2 new melanoma kindreds which carry a duplication of a 24bp repeat present in the 5' region of CDKN2A previously identified in melanoma families from Australia and the United States. This mutation has now been reported in 5 melanoma families from 3 continents: Europe, North America, and Australasia. The M53I mutation in exon 2 of CDKN2A has also been documented in 5 melanoma families from Australia and North America. The aim of this study was to determine whether the occurrence of the mutations in these families from geographically diverse populations represented mutation hotspots within CDKN2A or were due to common ancestors. Haplotypes of 11 microsatellite markers flanking CDKN2A were constructed in 5 families carrying the M53I mutation and 5 families carrying the 24bp duplication. There were some differences in the segregating haplotypes due primarily to recombinations and mutations within the short tandem-repeat markers; however, the data provide evidence to indicate that there were at least 3 independent 24bp duplication events and possibly only 1 original M53I mutation. This is the first study to date which indicates common founders in melanoma families from different continents.

Segregation analysis of cutaneous melanoma in Queensland

To investigate whether the familial clustering of cutaneous melanoma is consistent with Mendelian inheritance of a major autosomal gene, maximum likelihood segregation analyses were performed in a population-based sample of 1,912 families ascertained through a proband with melanoma diagnosed in Queensland between 1982 and 1990. Analyses were performed with the S.A.G.E. statistical package, using the REGTL program for a binary trait with a variable age of onset. We sought medical confirmation for all family members reported to have had melanoma, and only medically verified cases among relatives were included in the analyses. The hypothesis of codominant Mendelian inheritance gave a significantly better fit to the data than either dominant or recessive Mendelian inheritance, or environmental transmission. Overall, both Mendelian inheritance of a single major gene, and purely environmental transmission were rejected (P < 0.001). In both the single major gene and environmental models, there was strong evidence of familial dependence in melanoma occurrence (P < 0.001). These results are consistent with reported genetic heterogeneity in melanoma inheritance and suggest that other familial factors, such as pigmentation, skin type, and sun exposure habits, may play an important role in the familial clustering of melanoma.