High prevalence of the G101W germline mutation in theCDKN2A(P16ink4a) gene in 62 Italian malignant melanoma families

High- and intermediate-risk susceptibility variants in melanoma families from the Mediterranean area: A multicentre cohort from the MelaNostrum Consortium

BACKGROUND

Most of large epidemiological studies on melanoma susceptibility have been conducted on fair skinned individuals (US, Australia and Northern Europe), while Southern European populations, characterized by high UV exposure and dark-skinned individuals, are underrepresented.

OBJECTIVES

We report a comprehensive pooled analysis of established high- and intermediate-penetrance genetic variants and clinical characteristics of Mediterranean melanoma families from the MelaNostrum Consortium.

METHODS

Pooled epidemiological, clinical and genetic (CDKN2A, CDK4, ACD, BAP1, POT1, TERT, and TERF2IP and MC1R genes) retrospective data of melanoma families, collected within the MelaNostrum Consortium in Greece, Italy and Spain, were analysed. Univariate methods and multivariate logistic regression models were used to evaluate the association of variants with characteristics of families and of affected and unaffected family members. Subgroup analysis was performed for each country.

RESULTS

We included 839 families (1365 affected members and 2123 unaffected individuals). Pathogenic/likely pathogenic CDKN2A variants were identified in 13.8% of families. The strongest predictors of melanoma were ≥2 multiple primary melanoma cases (OR 8.1; 95% CI 3.3-19.7), >3 affected members (OR 2.6; 95% CI 1.3-5.2) and occurrence of pancreatic cancer (OR 4.8; 95% CI 2.4-9.4) in the family (AUC 0.76, 95% CI 0.71-0.82). We observed low frequency variants in POT1 (3.8%), TERF2IP (2.5%), ACD (0.8%) and BAP1 (0.3%). MC1R common variants (≥2 variants and ≥2 RHC variants) were associated with melanoma risk (OR 1.4; 95% CI 1.0-2.0 and OR 4.3; 95% CI 1.2-14.6, respectively).

CONCLUSIONS

Variants in known high-penetrance genes explain nearly 20% of melanoma familial aggregation in Mediterranean areas. CDKN2A melanoma predictors were identified with potential clinical relevance for cancer risk assessment.

Predictors of germline status for hereditary melanoma: 5 years of multi-gene panel testing within the Italian Melanoma Intergroup

BACKGROUND

The incidence of cutaneous melanoma is increasing in Italy, in parallel with the implementation of gene panels. Therefore, a revision of national genetic assessment criteria for hereditary melanoma may be needed. The aim of this study was to identify predictors of susceptibility variants in the largest prospective cohort of Italian high-risk melanoma cases studied to date.

MATERIALS AND METHODS

From 25 Italian centers, we recruited 1044 family members and germline sequenced 940 cutaneous melanoma index cases through a shared gene panel, which included the following genes: CDKN2A, CDK4, BAP1, POT1, ACD, TERF2IP, MITF and ATM. We assessed detection rate according to familial status, region of origin, number of melanomas and presence and type of non-melanoma tumors.

RESULTS

The overall detection rate was 9.47% (5.53% analyzing CDKN2A alone), ranging from 5.14% in sporadic multiple melanoma cases (spoMPM) with two cutaneous melanomas to 13.9% in familial cases with at least three affected members. Three or more cutaneous melanomas in spoMPM cases, pancreatic cancer and region of origin predicted germline status [odds ratio (OR) = 3.23, 3.15, 2.43, P < 0.05]. Conversely, age > 60 years was a negative independent predictor (OR = 0.13, P = 0.008), and was the age category with the lowest detection rate, especially for CDKN2A. Detection rate was 19% when cutaneous melanoma and pancreatic cancer clustered together.

CONCLUSIONS

Gene panel doubled the detection rate given by CDKN2A alone. National genetic testing criteria may need a revision, especially regarding age cut-off (60) in the absence of strong family history, pancreatic cancer and/or a high number of cutaneous melanomas.

Melanoma in children and adolescents: analysis of susceptibility genes in 123 Italian patients

BACKGROUND

A polygenic inheritance involving high, medium and low penetrance genes has been suggested for melanoma susceptibility in adults, but genetic information is scarce for paediatric patients.

OBJECTIVE

We aim to analyse the major high and intermediate melanoma risk genes, CDKN2A, CDK4, POT1, MITF and MC1R, in a large multicentre cohort of Italian children and adolescents in order to explore the genetic context of paediatric melanoma and to reveal potential differences in heritability between children and adolescents.

METHODS

One-hundred-twenty-three patients (<21 years) from nine Italian centres were analysed for the CDKN2A, CDK4, POT1, MITF, and MC1R melanoma predisposing genes. The rate of gene variants was compared between sporadic, familial and multiple melanoma patients and between children and adolescents, and their association with clinico-pathological characteristics was evaluated.

RESULTS

Most patients carried MC1R variants (67%), while CDKN2A pathogenic variants were found in 9% of the cases, the MITF E318K in 2% of patients and none carried CDK4 or the POT1 S270N pathogenic variant. Sporadic melanoma patients significantly differed from familial and multiple cases for the young age at diagnosis, infrequent red hair colour, low number of nevi, low frequency of CDKN2A pathogenic variants and of the MC1R R160W variant. Melanoma in children (≤12 years) had more frequently spitzoid histotype, were located on the head/neck and upper limbs and had higher Breslow thickness. The MC1R V92M variant was more common in children than in adolescents. CDKN2A common polymorphisms and MC1R variants were associated with a high number of nevi.

CONCLUSION

Our results confirm the scarce involvement of the major high-risk susceptibility genes in paediatric melanoma and suggest the implication of MC1R gene variants especially in the children population.

The identification of patient-specific mutations reveals dual pathway activation in most patients with melanoma and activated receptor tyrosine kinases in BRAF/NRAS wild-type melanomas

BACKGROUND

Increasing knowledge of cancer genomes has triggered the development of specific targeted inhibitors, thus providing a valuable therapeutic pool.

METHODS

In this report, the authors analyze the presence of targetable alterations in 136 tumor samples from 92 patients with melanoma using a comprehensive approach based on targeted DNA sequencing and supported by RNA and protein analysis. Three topics of high clinical relevance are addressed: the identification of rare, activating alterations; the detection of patient-specific, co-occurring single nucleotide variants (SNVs) and copy number variations (CNVs) in parallel pathways; and the presence of cancer-relevant germline mutations.

RESULTS

The analysis of patient-matched blood and tumor samples was done with a custom-designed gene panel that was enriched for genes from clinically targetable pathways. To detect alterations with high therapeutic relevance for patients with unknown driver mutations, genes that are untypical for melanoma also were included. Among all patients, CNVs were identified in one-third of samples and contained amplifications of druggable kinases, such as CDK4, ERBB2, and KIT. Considering SNVs and CNVs, 60% of patients with metastases exhibited co-occurring activations of at least 2 pathways, thus providing a rationale for individualized combination therapies. Unexpectedly, 9% of patients carry potentially protumorigenic germline mutations frequently affecting receptor tyrosine kinases. Remarkably two-thirds of BRAF/NRAS wild-type melanomas harbor activating mutations or CNVs in receptor tyrosine kinases.

CONCLUSIONS

The results indicate that the integrated analysis of SNVs, CNVs, and germline mutations reveals new druggable targets for combination tumor therapy.

CDKN2A germline mutations are not associated with poor survival in an Italian cohort of melanoma patients

BACKGROUND

Cyclin dependent kinase inhibitor 2A gene (CDKN2A) germline mutations have recently been associated with poor survival in patients with melanoma. Despite the high mutation rate in our cohort (up to 10% in patients with apparently sporadic melanoma), information on the impact of CDKN2A on survival in this cohort is lacking.

OBJECTIVE

To investigate whether poor survival associated with CDKN2A germline mutations was confirmed in a high mutation-prevalence cohort of Italian patients with melanoma undergoing a mutation-based follow-up.

METHODS

A total of 1239 patients with cutaneous melanoma were tested for CDKN2A mutational status and then assigned to a follow-up scheme according not only to family history but also to CDKN2A mutational status, as follow-up intervals were more frequent for CDKN2A germline mutation-positive (MUT⁺) patients. From this cohort, we selected 106 MUT⁺ patients (with familial melanoma or apparently sporadic melanoma) and 199 CDKN2A germline mutation-negative (MUT^-) patients with sporadic melanoma who were matched by age and sex and had a similar tumor stage distribution.

RESULTS

We found no difference in overall survival (hazard ratio, 0.85; 95% confidence interval, 0.48-1.52; P = .592,) or melanoma-specific survival (hazard ratio, 0.86; 95% confidence interval, 0.38-1.95; P = .718,) between MUT⁺ and MUT^- patients. MUT⁺ patients were more likely to develop multiple melanomas and to undergo surgical excision of dysplastic nevi than were MUT^- patients.

LIMITATIONS

Retrospective study.

CONCLUSION

CDKN2A mutations were not associated with survival in our cohort.

Characterization of melanoma susceptibility genes in high-risk patients from Central Italy

Genetic susceptibility to cutaneous melanoma has been investigated in Italian high-risk melanoma patients from different geographical regions. CDKN2A, CDK4, and MC1R genes have been screened in most studies, MITF and POT1 were screened in only one study, and none analyzed the TERT promoter. We carried out a mutational analysis of CDKN2A, CDK4 exon 2, POT1 p.S270N, MITF exon 10, MC1R, and the TERT promoter in 106 high-risk patients with familial melanoma (FM) and sporadic multiple primary melanoma (spMPM) from Central Italy and evaluated mutations according to the clinicopathological characteristics of patients and lesions. In FM, CDKN2A mutations were detected in 8.3% of the families, including one undescribed exon 1β mutation (p.T31M), and their prevalence increased with the number of affected relatives within the family. MC1R variants were identified in 65% of the patients and the TERT rs2853669 promoter polymorphism was identified in 58% of the patients. A novel synonymous mutation detected in MITF exon 10 (c.861A>G, p.E287E), although predicted as a splice site mutation by computational tools, could not functionally be confirmed to alter splicing. For spMPM, 3% carried CDKN2A mutations, 79% carried MC1R variants, and 47% carried the TERT rs2853669 promoter polymorphism. MC1R variants were associated with fair skin type and light hair color both in FM and in spMPM, and with a reduction of age at diagnosis in FM patients. Mutations in CDK4 exon 2 and the POT1 p.S270N mutation were not detected. A low frequency of CDKN2A mutations and a high prevalence of MC1R variants characterize high-risk melanoma patients from Central Italy.

Genetic counselling and high-penetrance susceptibility gene analysis reveal the novel CDKN2A p.D84V (c.251A>T) mutation in melanoma-prone families from Italy

Genetic susceptibility to primary cutaneous melanoma (PCM) may account for up to 12% of PCMs, presenting as the familial atypical mole/multiple melanoma syndrome (FAMMM), an autosomal dominant condition with incomplete penetrance and variable expressivity, characterized by PCM in at least two relatives and/or more than one PCMs in the same patient. To identify individuals at high genetic risk of PCM, from 1 January 2012 to 31 December 2015, we offered genetic counselling and molecular analysis of the two high-penetrance FAMMM susceptibility genes, cyclin-dependent kinase inhibitor 2A (CDKN2A) and cyclin-dependent kinase 4 (CDK4), to 92 consecutive, unrelated patients with FAMMM. Age at diagnosis and number of PCMs were obtained from medical records; the number of PCMs and affected relatives were recorded for each family. The diagnostic work-up consisted of genetic counselling and cascade genetic testing in patients and further extension to relatives of those identified as mutation carriers. All exons and exon/intron boundaries of CDKN2A and CDK4 genes were screened by direct bidirectional sequencing. We identified CDKN2A mutations in 19 of the 92 unrelated patients (20.6%) and in 14 additional, clinically healthy relatives. Eleven of these latter subsequently underwent excision of dysplastic nevi, but none developed PCM during a median follow-up of 37.3 months. In three patients from unrelated families, the novel CDKN2A p.D84V (c.251A>T) mutation was observed, associated with PCM in each pedigree. Genetic screening of FAMMM patients and their relatives can contribute towards specific primary and secondary prevention programmes for individuals at high genetic risk of PCM. The novel CDKN2A p.D84V (c.251A>T) mutation adds to the known mutations associated with FAMMM.

Absence of germline CDKN2A mutation in Sicilian patients with familial malignant melanoma: Could it be a population-specific genetic signature?

Germline CDKN2A mutations have been described in 25% to 40% of melanoma families from several countries. Sicilian population is genetically different from the people of Europe and Northern Italy because of its historical background, therefore familial melanoma could be due to genes different from high-penetrance CDKN2A gene. Four hundred patients with cutaneous melanoma were observed in a 6-years period at the Plastic Surgery Unit of the University of Palermo. Forty-eight patients have met the criteria of the Italian Society of Human Genetics (SIGU) for the diagnosis of familial melanoma and were screened for CDKN2A and CDK4 mutations. Mutation testing revealed that none of the families carried mutations in CDK4 and only one patient harboured the rare CDKN2A p.R87W mutation. Unlike other studies, we have not found high mutation rate of CDKN2A in patients affected by familial melanoma or multiple melanoma. This difference could be attributed to different factors, including the genetic heterogeneity of the Sicilian population. It is likely that, as in the Australian people, the inheritance of familial melanoma in this island of the Mediterranean Sea is due to intermediate/low-penetrance susceptibility genes, which, together with environmental factors (as latitude and sun exposure), could determine the occurrence of melanoma.

Genetic susceptibility to cutaneous melanoma in southern Switzerland: role of CDKN2A, MC1R and MITF

BACKGROUND

Nearly 10% of all cases of cutaneous melanoma (CM) occur in patients with a personal or family history of the disease.

OBJECTIVES

To obtain information about genetic predisposition to CM in Ticino, the southern region of Switzerland, a zone with moderate-to-high CM incidence.

METHODS

We identified germline mutations in highly CM-associated genes (CDKN2A and CDK4) and low/medium-penetrance variants (MC1R and MITF) in patients with multiple primary CMs or individuals with one or more CM and a positive family history for CM or pancreatic cancer among first- or second-degree relatives. Healthy blood donors (n = 146) were included as a control group.

RESULTS

From July 2010 to July 2012, 57 patients (41 pedigrees) were included. Twenty-six were melanoma-prone families (with at least two cases) and 15 had multiple CMs. Pancreatic cancer was found in six families. The CDKN2A mutation p.V126D was identified in seven patients (four families) with a founder effect, whereas CDKN2A A148T was detected in seven cases (five families) and seven healthy donors (odds ratio 2·76, 95% confidence interval 0·83-9·20). At least one MC1R melanoma-associated polymorphism was detected in 32 patients (78%) and 97 healthy donors (66%), with more than one polymorphism in 12 patients (29%) and 25 healthy donors (17%). The MITF variant p.E318K was identified in four patients from three additional pedigrees (7%) and one healthy control (0·7%).

CONCLUSIONS

Inclusion criteria for the Ticino population for genetic assessment should follow the rule of two (two affected individuals in a family or a patient with multiple CMs), as we detected a CDKN2A mutation in almost 10% of our pedigrees (four of 41), MITF p.E318K in 7% (three of 41) and a higher number of MC1R variants than in the control population.

Multiple primary melanomas (MPMs) and criteria for genetic assessment: MultiMEL, a multicenter study of the Italian Melanoma Intergroup

BACKGROUND

Multiple primary melanoma (MPM), in concert with a positive family history, is a predictor of cyclin-dependent kinase (CDK) inhibitor 2A (CDKN2A) germline mutations. A rule regarding the presence of either 2 or 3 or more cancer events (melanoma and pancreatic cancer) in low or high melanoma incidence populations, respectively, has been established to select patients for genetic referral.

OBJECTIVE

We sought to determine the CDKN2A/CDK4/microphthalmia-associated transcription factor mutation rate among Italian patients with MPM to appropriately direct genetic counseling regardless of family history.

METHODS

In all, 587 patients with MPM and an equal number with single primary melanomas and control subjects were consecutively enrolled at the participating centers and tested for CDKN2A, CDK4, and microphthalmia-associated transcription factor.

RESULTS

CDKN2A germline mutations were found in 19% of patients with MPM versus 4.4% of patients with single primary melanoma. In familial MPM cases the mutation rate varied from 36.6% to 58.8%, whereas in sporadic MPM cases it varied from 8.2% to 17.6% in patients with 2 and 3 or more melanomas, respectively. The microphthalmia-associated transcription factor E318K mutation accounted for 3% of MPM cases altogether.

LIMITATIONS

The study was hospital based, not population based. Rare novel susceptibility genes were not tested.

CONCLUSION

Italian patients who developed 2 melanomas, even in situ, should be referred for genetic counseling even in the absence of family history.

Epidemiological and genetic factors underlying melanoma development in Italy

Among human cancers, melanoma remains one of the malignancies with an ever-growing incidence in white populations. Recent advances in biological and immunological therapeutic approaches as well as increased efforts for secondary prevention are contributing to improve the survival rates. It is likely that a significant fall in mortality rates for melanoma will be achieved by further increase of the early detection through a more accurate selection of the higher-risk individuals (i.e., carriers of predisposing genetic alterations). A similar scenario occurs in Italy. In the present review, we have considered data on incidence, survival and mortality rates of melanoma in Italian population, including evaluation of the main risk factors and genetic mutations underlying disease susceptibility.

CDKN2A unclassified variants in familial malignant melanoma: combining functional and computational approaches for their assessment

CDKN2A codes for two oncosuppressors by alternative splicing of two first exons: p16INK4a and p14ARF. Germline mutations are found in about 40% of melanoma-prone families, and most of them are missense mutations mainly affecting p16INK4a. A growing number of p16INK4a variants of uncertain significance (VUS) are being identified but, unless their pathogenic role can be demonstrated, they cannot be used for identification of carriers at risk. Predicting the effect of these VUS by either a "standard" in silico approach, or functional tests alone, is rather difficult. Here, we report a protocol for the assessment of any p16INK4a VUS, which combines experimental and computational tools in an integrated approach. We analyzed p16INK4a VUS from melanoma patients as well as variants derived through permutation of conserved p16INK4a amino acids. Variants were expressed in a p16INK4a-null cell line (U2-OS) and tested for their ability to block proliferation. In parallel, these VUS underwent in silico prediction analysis and molecular dynamics simulations. Evaluation of in silico and functional data disclosed a high agreement for 15/16 missense mutations, suggesting that this approach could represent a pilot study for the definition of a protocol applicable to VUS in general, involved in other diseases, as well.

High- and low-penetrance cutaneous melanoma susceptibility genes

The aim of this review is to report the current understanding of the molecular genetics of melanoma predisposition. To date, two high-penetrance melanoma susceptibility genes, cyclin-dependent kinas inhibitor (CDKN)2A on chromosome 9p21 and cyclin-dependent kinase (CDK4) on 12q13, have been identified. Germline inactivating mutations of the CDKN2A gene are the most common cause of inherited susceptibility to melanoma. Worldwide, a few families have been found to harbor CDK4 mutations. However, predisposing alterations to familial melanoma are still unknown in a large proportion of kindreds. Other melanoma susceptibility loci have been mapped through genome-wide linkage analysis, although the putative causal genes at these loci have yet to be identified. Much ongoing research is being focused on the identification of low-penetrance melanoma susceptibility genes that confer a lower melanoma risk with more frequent variations. Specific variants of the MC1R gene have been demonstrated to confer an increase in melanoma risk. In addition, conflicting data are available on other potential low-penetrance genes encoding proteins involved in pigmentation, cell growth and differentiation, DNA repair or detoxifying of metabolites.

Familial melanoma: clinical factors associated with germline CDKN2A mutations according to the number of patients affected by melanoma in a family

BACKGROUND

Features associated with an increased frequency of cyclin-dependent kinase inhibitor 2A (CDKN2A) mutations have been identified in families with 3 or more patients with cutaneous melanoma (CM). However, in families with 2 patients with CM, which represent the majority of familial melanoma, these factors have been rarely studied.

OBJECTIVE

We investigated association of 3 clinical features with the presence of a CDKN2A mutation in a family by extent of CM family clustering (2 vs ≥3 patients with CM among first-degree relatives in a family).

METHODS

We included 483 French families that comprised 387 families with 2 patients with CM (F2 families) and 96 families with 3 or more patients with CM (F3+ families). Three clinical factors were examined individually and in a joint analysis: median age at diagnosis younger than 50 years, and 1 or more patient in a family with multiple primary melanoma or with pancreatic cancer.

RESULTS

The frequency of CDKN2A mutations was higher in F3+ families (32%) than in F2 families (13%). Although early age at melanoma diagnosis and occurrence of multiple primary melanoma in 1 or more patient were significantly associated with the risk of a CDKN2A mutation in F2 families, early age at melanoma diagnosis and occurrence of pancreatic cancer in a family were significantly associated with CDKN2A mutations in F3+ families.

LIMITATIONS

The study was not population based.

CONCLUSIONS

This study shows that factors associated with CDKN2A mutations differ by extent of CM family clustering. It indicates that, in France, families with 2 patients with CM are eligible for genetic testing especially when there is an early age at CM diagnosis and/or 1 or more patients with multiple primary melanoma.

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.

Risk factors of familial pancreatic cancer in Japan: current smoking and recent onset of diabetes

OBJECTIVES

In western countries, 7% to 10% of patients with pancreatic cancer (PC) have a familial predisposition to their disease. The aim of this study was to determine the familial susceptibility to PC in Japan.

METHODS

Five hundred seventy-seven patients with PC and 577 age- and gender-matched controls were analyzed for cancer history in their first-degree relative(s) (FDRs) and demographic factors.

RESULTS

The patients with PC were more likely to have an FDR with PC (6.9%) than the controls (2.9%; odds ratio [OR], 2.5; P = 0.02). Three patients (0.5%), but none of the controls, had a family history of PC in multiple FDRs. Smoking, especially current smoking (OR, 1.5; P = 0.005), and diabetes mellitus (OR: 1.7, P = 0.001) were also associated with PC. The odds increased up to 10-fold if the patients were positive for these 3 factors. The patients with familial PC were more likely to be current smokers (40%) and to have diabetes mellitus (32.5%) than the sporadic cases (30.1% and 20.1%; OR, 1.6 and 1.9).

CONCLUSIONS

A family history of PC is a risk of PC in Japan (6.9%) as is a personal history of diabetes and smoking. It is prudent to inform the kindred of patients with familiar PC of the risk of smoking and to follow carefully if they develop diabetes.

Clinical and histologic characteristics of malignant melanoma in families with a germline mutation in CDKN2A

BACKGROUND

About 10% of cutaneous malignant melanomas (CMM) occur in individuals with a family history of melanoma. In 20% to 40% of melanoma families germline mutations in CDKN2A are detected. Knowledge of the clinicohistologic characteristics of melanomas and patients from these families is important for optimization of management strategies, and may shed more light on the complex interplay of genetic and environmental factors in the pathogenesis of melanoma.

OBJECTIVE

We sought to investigate the clinical and histologic characteristics of CMM in CDKN2A-mutated families.

METHODS

Clinical and histologic characteristics of 182 patients with 429 CMM from families with a founder mutation in CDKN2A (p16-Leiden mutation) were compared with 7512 patients with 7842 CMM from a population-based cancer registry.

RESULTS

Patients with p16-Leiden had their first melanoma 15.3 years younger than control patients. The 5-year cumulative incidence of second primary CMM was 23.4% for patients with p16-Leiden compared with 2.3% for control patients. The risk of a second melanoma was twice as high for patients with p16-Leiden who had their first melanoma before age 40 years, compared with older patients with p16-Leiden. Unlike control patients, there was no body site concordance of the first and second melanoma in patients with p16-Leiden and multiple primary melanomas. Patients with p16-Leiden had significantly more superficial spreading, and less nodular and lentiginous melanomas.

LIMITATIONS

Ascertainment of patients with p16-Leiden was family based. The study was performed in families with a founder mutation, the p16-Leiden mutation.

CONCLUSION

Our findings are consistent with a pathogenic pathway of melanoma development from nevi, starting early and ongoing throughout life, and not related to chronic sun exposure.

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.

Genomic rearrangements of the CDKN2A locus are infrequent in Italian malignant melanoma families without evidence of CDKN2A/CDK4 point mutations

Predisposition to familial cutaneous malignant melanoma has been associated with mutations in the CDKN2A and CDK4 genes. However, only a small subgroup of melanoma pedigrees harbour CDKN2A or CDK4 germline mutations. It is possible that other types of CDKN2A rearrangements, not detectable by routine PCR-based approaches, are involved in a fraction of melanoma cases negative for point sequence changes. In order to gain insights on the possible role of CDKN2A large deletions or duplications in melanoma susceptibility in the Italian population, we screened a series of 124 cutaneous malignant melanoma families referred to five national medical/cancer genetics centres. All probands were negative for point mutations in CDKN2A and CDK4. All samples were tested by MLPA (multiplex ligation-dependent probe amplification), and the results were confirmed by real-time quantitative PCR in a subset of 53 cases. No genomic rearrangements were detected in this series, one of the largest so far investigated. These data suggest that large deletions/duplications in the CDKN2A locus are infrequently involved in the development of familial melanoma in the Italian population. Based on these results, routine search for these rearrangements in CDKN2A- and CDK4-mutation negative melanoma families is not warranted, although it would be reasonable to pursue it in selected cases with very strong family history and/or showing linkage to 9p21.

Clinical genetic testing for familial melanoma in Italy: a cooperative study

BACKGROUND

The Italian Society of Human Genetics' (SIGU) recommendations on genetic counseling and testing for hereditary melanoma state that clinical genetic testing can be offered to Italian melanoma families with at least two affected members.

OBJECTIVE

In the framework of a cooperative study, we sought to establish the frequency of cyclin-dependent kinase inhibitor 2A mutations in melanoma families that underwent clinical genetic counseling and testing in accordance with the SIGU recommendations at 9 centers in different Italian regions.

METHODS

Cyclin-dependent kinase inhibitor 2A testing was conducted by direct sequencing and multiplex ligation-dependent probe amplification analysis in melanoma families with at least two affected members.

RESULTS

A total of 33% (68/204) of the families harbored cyclin-dependent kinase inhibitor 2A mutations. In the 145 families with two affected members the mutation frequency was 25%. Three novel mutations, L94P, A86T, and c.407dupG, were identified among the cases and not in 200 controls.

LIMITATIONS

We were unable to perform separate analyses for individual centers, as in some cases the number of families was too small.

CONCLUSIONS

The availability of clinical genetic testing for melanoma to families with just two affected members in the same branch is justified in Italy in terms of the likelihood of identifying a mutation.

p16INK4a-induced senescence is disabled by melanoma-associated mutations

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

A comparison of CDKN2A mutation detection within the Melanoma Genetics Consortium (GenoMEL)

CDKN2A is the major melanoma susceptibility gene so far identified, but only 40% of three or more case families have identified mutations. A comparison of mutation detection rates was carried out by "blind" exchange of samples across GenoMEL, the Melanoma Genetics Consortium, to establish the false negative detection rates. Denaturing high performance liquid chromatography (DHPLC) screening results from 451 samples were compared to screening data from nine research groups in which the initial mutation screen had been done predominantly by sequencing. Three samples with mutations identified at the local centres were not detected by the DHPLC screen. No additional mutations were detected by DHPLC. Mutation detection across groups within GenoMEL is carried out to a consistently high standard. The relatively low rate of CDKN2A mutation detection is not due to failure to detect mutations and implies the existence of other high penetrance melanoma susceptibility genes.

Management of familial melanoma

Relatives of patients with melanoma are at increased risk of melanoma. We review the evidence that this risk may be attributed both to shared susceptibility genes (both high-penetrance and lower-penetrance genes) and shared environment. The most frequent high-penetrance susceptibility gene is CDKN2A, and environmental effects on the risk to gene carriers are evident in that CDKN2A penetrance is higher in CDKN2A-mutation-positive families living in Australia than those in Europe. We review the approaches to managing melanoma families, in which the likelihood of there being detectable CDKN2A mutations is positively correlated with the number of cases of melanoma in the family. Within families, risk that an individual carries a germline mutation can be estimated by pedigree analysis for autosomal dominant genes with incomplete penetrance. Prevention advice to families relates to moderation of sun exposure and self-examination of naevi, although there are few supportive data.

CDKN2A-positive breast cancers in young women from Poland

PURPOSE

To investigate the contribution of CDKN2A A148T common variant to early-onset breast cancer in Poland, and to establish the characteristic features of these cancers.

EXPERIMENTAL DESIGN

We studied 3,069 women diagnosed with breast cancer under the age of 51 and 3,493 population controls. CDKN2A variant were detected using RFLP-PCR and confirmed by genomic sequencing. Clinical and pathological features of CDKN2A-positive cases and CDKN2A-negative cases were compared.

RESULTS

A148T variant was identified in 157 of 3,069 women with breast cancer (5.1%). Overall, the odds ratio for early-onset breast cancer, given a CDKN2A variant was 1.4 (95% CI 1.075-1.725; P = 0.012). Breast tumors in women with the CDKN2A variant were more commonly intraductal cancers (DCIS) with micro-invasion (14.8% vs. 8.5%; P = 0.035). Carriers and non-carriers were similar with respect to tumor size, laterality, multicentricity, nodal status, family history and estrogen-receptor status.

CONCLUSION

The CDKN2A A148T variant seems to contribute to early-onset breast cancer in Poland. Breast tumors which arise in carriers of A148T variant appear to be similar to those of breast cancers in the population at large.

Factors predicting the occurrence of germline mutations in candidate genes among patients with cutaneous malignant melanoma from South Italy

Clinical predictors for germline mutations of candidate genes in large clinic based population of patients with cutaneous malignant melanoma (CMM) are widely awaited. Using denaturing high-performance liquid chromatography (DHPLC) analysis and DNA sequencing, 557 consecutively-collected CMM patients originating from South Italy were screened for CDKN2A germline mutations; subsets of them were screened for mutations in the BRAF and BRCA2 genes. Seven CDKN2A mutations were detected in 14 (2.5%) CMM patients. Relative risk of carrying a CDKN2A mutation for CMM patients was demonstrated to significantly increase with the presence of familial recurrence of melanoma (risk ratio (RR)=6.31; p=0.0009), multiple primary melanomas (RR=3.43; p=0.0014), and early onset age (RR=4.56; p=0.0026). All CDKN2A mutations were observed in non-Sardinian patients (14/441; 3.2%), whereas BRAF and BRCA2 genes were found mutated in Sardinian patients (3/116; 2.6%). Such indicators of the presence of CDKN2A mutations will be useful in counselling patients about undergoing genetic testing. Our findings strongly suggest that mutation rates of candidate cancer genes may deeply vary among CMM patients from different geographical areas.

Promoter SNPs in G1/S checkpoint regulators and their impact on the susceptibility to childhood leukemia

Mutations leading to the alteration of cell-cycle checkpoint functions are a common feature of most cancers. Because of the highly regulated nature of the cell cycle, it seems likely that variation in gene dosage of key components due to functional regulatory polymorphisms could play an important role in cancer development. Here we provide evidence of the involvement of promoter single-nucleotide polymorphisms (pSNPs) in the cyclin-dependent–kinase inhibitor genes CDKN2A, CDKN2B, CDKN1A, and CDKN1B in the etiology of childhood pre-B acute lymphoblastic leukemia (ALL). A case-control study, conducted in 240 patients with pre-B ALL and 277 healthy controls, combined with a family-based analysis using 135 parental trios, all of French-Canadian origin, were used to evaluate single-site genotypic as well as multilocus haplotypic associations for a total of 10 pSNPs. Using both study designs, we showed evidence of association between variants CDKN2A −222A, CDKN2B −593A, and CDKN1B −1608A, and an increased risk of ALL. These findings suggest that variable expression levels of cell-cycle inhibitor genes CDKN2A, CDKN2B, and CDKN1B due to regulatory polymorphisms could indeed influence the risk of childhood pre-B ALL and contribute to carcinogenesis.

Impact of E27X, a novel CDKN2A germ line mutation, on p16 and p14ARF expression in Italian melanoma families displaying pancreatic cancer and neuroblastoma

Mutations in the CDKN2A gene underlie melanoma susceptibility in as many as 50% of melanoma kindreds in selected populations, and several CDKN2A founder mutations have been described. Inherited mutations in CDKN2A have been found to be associated with other, non-melanoma cancers including pancreatic cancer (PC) and neural system tumors (NST). Here we report a novel germline mutation in exon 1 of the CDKN2A gene, E27X, which we first detected in melanoma patients living in or originally from a small geographic area bordering Liguria in north-western Italy. A subset of melanoma kindreds positive for this mutation displayed PC and neuroblastoma. E27X generates a premature stop codon, leading to dramatically reduced protein levels of p16 and leaving p14ARF unaltered. As PC and NSTs have been postulated to be preferentially associated with CDKN2A mutations located in exon 2 and/or affecting p14ARF alone, the position of E27X in exon 1alpha provides interesting insights towards clarifying the mechanisms by which the CDKN2A/ARF locus is involved in cancer predisposition.

Population-based prevalence of CDKN2A mutations in Utah melanoma families

Cyclin-dependent kinase inhibitor 2A (CDKN2A or p16) is the major melanoma predisposition gene. In order to evaluate the candidacy for genetic testing of CDKN2A mutations among melanoma prone families, it is important to identify characteristics that predict a high likelihood of carrying a CDKN2A mutation. We primarily used a unique Utah genealogical resource to identify independent melanoma prone families whom we tested for mutations in CDKN2A, cyclin-dependent kinase 4, and alternate reading frame. We sampled 60 families which met the inclusion criteria of two or more affected first-degree relatives. We found four different pathogenic CDKN2A mutations in five families, mutations of uncertain significance in two families, and known polymorphisms in three families. One of the mutations of uncertain significance, 5' untranslated region -25C>T, has not been previously described. Among our population-based set of Utah families, the prevalence of CDKN2A mutations was 8.2% (4/49); the overall prevalence when physician-referred pedigrees were also considered was between 8.3% (5/60) and 10% (6/60). Having four or more first- or second-degree relatives with melanoma, or a family member with > or =3 primary melanomas, correlated strongly with carrying a CDKN2A mutation. We observed a significantly elevated rate of pancreatic cancer in one of four families with a deleterious CDKN2A mutation.

Role of the CDKN2A Locus in Patients With Multiple Primary Melanomas

Purpose

We have studied a consecutive case series of patients with multiple primary melanoma (MPM) for the involvement of the melanoma susceptibility loci CDKN2A and CDK4.

Patients and Methods

One hundred four MPM patients (81 patients with two primary melanomas, 14 with three, five with four, one with five, two with six, and one with seven) were included.

Results

Seven different CDKN2A germline mutations were identified in 17 patients (16.3%). In total, we identified 15 CDKN2A exon 2, one exon 1α missense mutation, and one exon 1β frameshift mutation. The age of onset was significantly lower and the number of primary melanomas higher in patients with mutations. CDKN2A mutations were more frequent in patients with familial history of melanoma (35.5%) compared with patients without (8.2%), with a relative risk (RR) of 4.32 (95% CI, 1.76 to 10.64; P = .001), and in patients with more than two melanomas (39.1%) compared with patients with only two melanomas (10%) with an RR of 3.29 (95% CI, 1.7 to 6.3; P = .002). The A148T polymorphism was more frequent in patients with MPMs than in the control population (P = .05). A variant of uncertain significance, A127S, was also detected in one patient. No CDK4 mutations were identified, suggesting that it has a low impact in susceptibility to MPM.

Conclusion

MPM patients are good candidates for CDKN2A mutational screening. These patients and some of their siblings should be included in a program of specific follow-up with total body photography and digital dermoscopy, which will result in the early detection of melanoma in this subset of high-risk patients and improve phenotypic characterization.

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.

Inverse correlation between p16INK4A expression and NF-kappaB activation in melanoma progression

Expression of p16INK4A, the product of the melanoma susceptibility gene CDKN2A, has been shown to decrease in correlation with tumor progression. P16INK4A is a key regulator of cell-cycle function, and likely interacts with a variety of targets alongside cyclin-dependent kinases (CDKs). One such target is nuclear factor KB (NF-kappaB), a pleiotropic transcription factor that plays a crucial role in apoptosis, oncogenesis and cell cycle control. NF-kappaB p65 has been shown to be activated in melanoma cell lines but few studies decribe its expression in the tissue. In the present study we focused on synchronous expression of p16INK4A and NF-kappaB p65 and their functional activation in melanoma cell lines and biopsy tissue. Activation of NF-kappaB p65, as observed by electrophoretic mobility shift assay in cell lines, was correlated with expression and cellular localization of the active and inactive forms of its inhibitor, IkappaB-alpha. In melanocytic lesions, p16INK4A and NF-kappaB p65 expression were inversely correlated with levels of the nuclear component of NF-kappaB p65 increasing from nevi to primary melanomas and metastases.

Screening for pancreatic neoplasia in high-risk individuals: an EUS-based approach

BACKGROUND & AIMS

Relatives of patients with pancreatic cancer and persons with certain inherited syndromes are at increased risk for developing pancreatic cancer. We prospectively evaluated the feasibility of screening for pancreatic neoplasia in high-risk individuals.

METHODS

Individuals from familial pancreatic cancer kindreds and a patient with Peutz-Jeghers syndrome underwent screening endoscopic ultrasound (EUS). If the EUS was abnormal, EUS-guided fine-needle aspiration, endoscopic retrograde cholangiopancreatography (ERCP), and spiral computed tomography (CT) were performed. Patients with abnormalities suggesting neoplasia had surgery.

RESULTS

Thirty-eight patients were studied; 31 (mean age, 58 yr; 42% men) from kindreds with > or =3 affected with pancreatic cancer; 6 from kindreds with 2 affected relatives, 1 was a patient with Peutz-Jeghers syndrome. None had symptoms referable to the pancreas or suggestive of malignancy. Six pancreatic masses were found by EUS: 1 invasive ductal adenocarcinoma, 1 benign intraductal papillary mucinous neoplasm, 2 serous cystadenomas, and 2 nonneoplastic masses. Hence, the diagnostic yield for detecting clinically significant pancreatic neoplasms was 5.3% (2 of 38). The 1 patient with pancreatic cancer was treated and still is alive and disease-free >5 years after surgery. EUS changes similar to those associated with chronic pancreatitis were found, which were more common in patients with a history of regular alcohol intake (P = 0.02), but also occurred in patients who did not consume alcohol. Screening also led to a new diagnosis and treatment of symptomatic upper-gastrointestinal conditions in 18.4% of patients.

CONCLUSIONS

EUS-based screening of asymptomatic high-risk individuals can detect prevalent resectable pancreatic neoplasia but false-positive diagnoses also occur.

Clinical germline genetic testing for melanoma

Clinical genetic testing for mutations in CDKN2A (cyclin-dependent kinase inhibitor 2A), a melanoma susceptibility gene, is now available. The International Melanoma Genetics Consortium advocates that genetic testing for CDKN2A should be done only as part of a research protocol. Experience with genetic testing for other cancer-susceptibility genes indicates that CDKN2A testing has enormous potential for the prevention and detection of a deadly disease. However, clinicians need to understand the benefits and shortcomings of clinical CDKN2A testing so that it can be used advantageously. Here, we examine whether CDKN2A meets the recommendations of the American Society of Clinical Oncology (ASCO) for cancer-susceptibility genetic testing. Although genetic testing for hereditary melanoma should, whenever possible, occur within research protocols, it might be successfully done outside of research protocols if attention is paid to selection, education, and counselling needs of patients; valid test interpretation; and the changing of medical management in appropriate individuals.

INK4/ARF germline alterations in pancreatic cancer patients

BACKGROUND

Roughly 40% of germinal mutations in melanoma families (MF) affect p16(INK4a) and p14(ARF). We investigated the association between INK4/ARF alterations and the occurrence of pancreatic cancer in MF and in sporadic pancreatic cancer (SPC) patients.

PATIENTS AND METHODS

Forty-nine MF, 66 SPC cases and 54 controls were enrolled. The INK4/ARF locus was screened.

RESULTS

As compared with the general population, the risk of pancreatic cancer (PC) was increased 9.4-fold [95% confidence interval (CI) 2.7-33.4] and 2.2-fold (95% CI 0.8-5.7) in G101W-positive and -negative MF, respectively, while mean ages at onset were 61 and 77 years, respectively. A 1.7 (95% CI 1.06-2.79) increased risk of cancer at any site was observed among first-degree relatives of SPC cases as compared with controls. The G101W founder mutation was detected in 4% of SPC cases but the rate increased to 13% when tumor clustering in either branch of families was taken into account. One G101W-positive PC patient with a melanoma in a first-degree relative harbored a germline deletion of the second allele, including exon 1B.

CONCLUSIONS

The presence of a deletion including exon 1B in two PC patients points to the involvement of p14(ARF) in the development of PC and may suggest that the increased risk of PC in MF is caused by impairment of both loci.

Expression and localization of mutant p16 proteins in melanocytic lesions from familial melanoma patients

Little is known about the correlation between the loss of p16 expression and tumor progression in familial melanoma; no systematic study has been conducted on p16 expression in melanocytic tumors from patients carrying germline CDKN2A mutations. We analyzed 98 early primary lesions from familial patients, previously tested for germline CDKN2A status, by quantitative immunohistochemistry using 3 p16 antibodies. We found that p16 expression was inversely correlated with tumor progression and was significantly lower in melanomas, including in situ lesions, than in nevi. Of other features analyzed, tumor thickness showed the most significant correlation with p16 levels. Lesions from mutation-negative patients displayed combined nuclear and cytoplasmic staining. However, some mutation-positive lesions (ie, G101W, 113insR, M53I, R24P, and 33ins24), including benign nevi, showed nuclear mislocalization, confirming previous studies suggesting that subcellular distribution indicates functional impairment of p16.

BRAF gene is somatically mutated but does not make a major contribution to malignant melanoma susceptibility: the Italian Melanoma Intergroup Study

PURPOSE

Ocogenic activation of the BRAF gene has been demonstrated to be involved in the pathogenesis of malignant melanoma (MM). In this study, we investigated the contribution of BRAF to melanoma susceptibility, also making a comparison with frequency of CDKN2A germline mutations in MM patients from different areas in Italy.

PATIENTS AND METHODS

sing a combination of denaturing high-performance liquid chromatography analysis and automated sequencing on genomic DNA from peripheral blood or tumor tissue samples, 569 MM patients (211 from northern Italy and 358 from southern Italy) were screened for BRAF mutations.

RESULTS

Three BRAF germline sequence variants (M116R, V599E, and G608H) were identified in four (0.7%) of 569 MM patients. The most common BRAF mutation, V599E, was detected in one germline DNA sample only; M116R and G608H were newly described mutations. A high frequency (59%) of BRAF mutations was instead observed in tumor samples from patients also undergoing germline DNA analysis; at the somatic level, substitution of valine 599 was found to account for the majority (88%) of BRAF mutations. We then estimated the germline mutation rates in BRAF and CDKN2A among 358 consecutively collected patient samples originating in southern Italy; a low (2.5%) or very low (0.29%) prevalence of CDKN2A and BRAF mutations, respectively, was detected.

CONCLUSION

utation analysis of either blood DNA from a large collection of MM patients or matched MM tissues from a subset of such patients revealed that BRAF is somatically mutated and does not play a major role in melanoma susceptibility. The present study further suggests that patient origin may account for different mutation rates in candidate genes.

The latent membrane protein 1 of Epstein-Barr virus and loss of the INK4a locus: paradoxes resolve to cooperation in carcinogenesis in vivo

Nasopharyngeal carcinoma (NPC) is the most tightly Epstein-Barr virus (EBV)-associated tumour. The EBV oncoprotein latent membrane protein 1 (LMP1) is frequently expressed in NPC tumours and may play a role in the genesis of the disease. NPC tumours often exhibit loss of expression (by deletion or methylation) of the INK4a locus, which encodes the tumour suppressor genes p16INK4a and p14ARF. To investigate the contribution of LMP1 and INK4a loss to tumourigenesis, skin chemical carcinogenesis was conducted using PyLMP1 and INK4a null mice. Surprisingly, INK4a null mice developed significantly fewer papillomas than wild-type mice, nevertheless, the papillomas that did develop grew faster and converted more rapidly to carcinoma than controls. This indicates that while loss of the INK4a locus plays an important role in the later stages of tumourigenesis, initially its loss inhibits papilloma formation. Conversely, LMP1 promoted papilloma formation but paradoxically inhibited papilloma growth. Using cross-breeds, it was found that LMP1 cooperates with loss of the INK4a locus during epithelial tumourigenesis. The expression of LMP1 overcame the inhibition of papilloma formation observed in INK4a null mice, whilst the loss of the INK4a locus counteracted the inhibition of papilloma growth rate found in PyLMP1 mice. This suggests that LMP1 mediates the inhibition of papilloma growth via one or both of the INK4a locus products. Intriguingly, mice heterozygous for INK4a loss showed lesion growth rates intermediate between wild-type and null, demonstrative of haploinsufficiency. We propose that LMP1 acts at the early stages in carcinogenesis to promote the development of benign tumours and that early reduction of INK4a locus expression allows these lesions to expand in size. In addition, loss of the INK4a locus accelerates the development of a more aggressive lesion. Conversely, complete loss of the INK4a locus in an otherwise normal cell might inhibit lesion formation.

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.

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.

Genetics and pancreatic disease

The recognition that variations in the DNA sequence of key genes predispose individuals to acute pancreatitis, chronic pancreatitis, and pancreatic cancer represents one of the greatest breakthroughs in pancreas research. This review highlights recent progress in understanding mutations in the cationic trypsinogen gene, the pancreatic secretory trypsin inhibitor gene, and the cystic fibrosis transmembrane conductance regulator gene with respect to pancreatitis. It also notes progress in the use of microarray technology, classification of chronic pancreatitis, and predisposition to pancreatic cancer.