An assessment of the CDKN2A variant Ala148Thr as a nevus/melanoma susceptibility allele

Melanocytic nevi are the most potent risk factors for melanoma yet identified. Variation in the nevus phenotype within a population is predominantly genetically determined. Genes that determine nevus expression may therefore act as low penetrance melanoma susceptibility genes. Rare germline mutations in CDKN2A predispose to melanoma and appear to be nevogenic, although the correlation between nevus phenotype and mutation status is poor. It is plausible that more common CDKN2A variants may influence both melanoma susceptibility and nevus susceptibility. Ala148Thr is a G to A missense polymorphism of CDKN2A, which is found in 4%-6% of the general population. We have investigated the role of Ala148Thr as a low penetrance melanoma or nevus susceptibility allele in two separate groups of individuals. The first was a sample of 488 adults recruited from 179 families of patients with the atypical nevus phenotype and/or a family history of melanoma, and the second was a population-based sample of 599 women. Similar prevalences of Ala148Thr (4.9% and 5.2%) were found in both samples but significant variation in the prevalence of the polymorphism was seen across geographic areas within England. There was no association between Ala148Thr status and nevus number or history of melanoma, and therefore the results did not support the hypothesis that the Ala148Thr variant is a low penetrance melanoma or nevus susceptibility allele. A significant protective role of Ala148Thr on the number of atypical nevi was observed in the family sample (mean of 1 atypical nevus in those with the allele and 3.5 nevi in those without, p = 0.02). After allowing for potential confounders this was not evident in the population-based sample.     

Longitudinal assessment of the nevus phenotype in a melanoma kindred

Phenotypic characteristics of members of a melanoma prone kindred with a V126D CDKN2A gene mutation were monitored over approximately 15 y. Thirty-eight previously studied subjects were recruited. Participants underwent a complete skin examination by the same dermatologist who examined them initially. The size and location of all nevi were recorded on a body map diagram. Total nevus number (TNN) and total nevus density (TND) were determined. CDKN2A sequencing verified 13 mutation carriers and 16 non-carriers. Nine participants were spouse controls without a history of melanoma and did not carry a CDKN2A mutation. Mutation carriers demonstrated a greater mean TNN and TND at initial and follow-up examinations compared with non-carriers and continued to develop nevi rather than show nevus regression seen in non-carriers and spouse controls. Non-carriers showed an intermediate nevus phenotype between mutation carriers and spouse controls. Four of the 13 mutation carriers and one non-carrier have developed invasive melanoma. Over a 15-y interval, TNN and TND were increased in mutation carriers compared with non-carriers and spouse controls. Continued accumulation of nevi in mutation carriers supports a nevogenic role for this CDKN2A mutation. An intermediate nevus phenotype in non-carrier family members suggests the presence of additional modifier genes.     

The relationship between the epidermal growth factor (EGF) 5'UTR variant A61G and melanoma/nevus susceptibility

The inheritance of a G allele in position 61 in the 5'UTR of the epidermal growth factor (EGF) gene has been reported to increase melanoma susceptibility, a finding we have investigated in this study. The most potent phenotypic risk factor for melanoma is the atypical mole syndrome (AMS) phenotype. Our hypothesis is that the AMS is genetically determined and that nevus genes are also low penetrance melanoma susceptibility genes. We report that the G allele frequencies were the same in 697 healthy women and 380 melanoma cases (OR 0.97, 95% CI 0.8-1.2 p=0.76). We therefore found no evidence that this polymorphism is a melanoma susceptibility gene. Furthermore, we found no evidence that the polymorphism controls the nevus phenotype (nevus number, number atypical nevi or AMS phenotype). We did find some evidence that the G allele may be associated with decreased tumor Breslow thickness (OR 0.5, 95% CI 0.3-0.9) for the A/A genotype versus A/G and G/G combined in tumors of thickness >3.5 vs < or =3.5 mm and may therefore act as a predictor of survival, although this finding is not in accord with the original report. This is the second study to find no association between EGF +61 and melanoma susceptibility.     

Decreased gene expression responsible for post-ultraviolet DNA repair synthesis in aging: a possible mechanism of age-related reduction in DNA repair capacity

A reduction in the post-ultraviolet (UV) DNA repair capacity is associated with aging. To clarify the mechanism of this change, we examined the DNA repair capacity of skin fibroblasts from healthy donors of different ages by the two methods: host cell reactivation (HCR) assay and ELISA of cyclobutane pyrimidine dimers and pyrimidine-pyrimidone (6-4) photoproducts. In HCR assay, cells from elderly donors exhibited significant declines in the ability to restore transfected reporter DNA damaged by UV light. In contrast, the ability to remove DNA damage declined little with age in ELISA. These results imply that the age-sensitive step took place after the damage excision in nucleotide excision repair (NER). The mRNA expression of DNA repair synthesis-related genes (DNA polymerase delta, replication factor C, and proliferating cell nuclear antigen) were markedly decreased in the cells from multiple elderly subjects compared with those from young subjects. Further, the protein level of DNA polymerase delta1, a catalytic subunit of the pivotal factor in repair synthesis, correlated with the mRNA level. These findings suggest that the reduced post-UV DNA repair capacity in aging results from an impairment in the latter step of NER by the decreased expression of factors in repair synthesis.     

Epithelioid blue nevus: a rare variant of blue nevus not always associated with the Carney complex

Epithelioid blue nevus is a rare variant of blue nevus that has been recently described in patients with Carney complex. Some of the patients with Carney complex have multiple epithelioid blue nevi and a familial history of similar lesions is often recorded. Epithelioid blue nevus consists of an intradermal melanocytic nevus composed of polygonal epithelioid cells laden with melanin. Neoplastic cells show no maturation at the base of the lesion and, in contrast with the usual stromal changes in blue nevi, epithelioid blue nevus exhibits no fibrosis of the dermis. We have studied three cases of epithelioid blue nevus in three patients with no evidence of Carney complex. The lesions were solitary and there was no family history of similar lesions. Therefore, epithelioid blue nevus is a distinctive variant of blue nevus that may also appear as a sporadic lesion and is not always associated with Carney complex.     

Alterations of DNA repair in melanoma cell lines resistant to cisplatin, fotemustine, or etoposide

Resistance to chemotherapy is a common phenomenon in malignant melanoma. In order to assess the role of altered DNA repair in chemoresistant melanoma, we investigated different DNA repair pathways in one parental human melanoma line (MeWo) and in sublines of MeWo selected in vitro for drug resistance against four commonly used drugs (cisplatin, fotemustine, etoposide, and vindesine). Host cell reactivation assays with the plasmid pRSVcat were used to assess processing of different DNA lesions. With ultraviolet-irradiated plasmids, no significant differences were found, indicating a normal (nucleotide excision) repair of DNA photoproducts. With singlet oxygen-treated plasmid, the fotemustine- and cisplatin-resistant lines exhibited a significantly increased (base excision) repair of oxidative DNA damage. With fotemustine-treated plasmid, the fotemustine-resistant subline did not exhibit an increased repair of directly fotemustine-induced DNA damage. Similar results were obtained with cisplatin-induced DNA crosslinks in the cisplatin-resistant line. The fotemustine- and etoposide-resistant sublines have been shown to exhibit a reduced expression of genes involved in DNA mismatch repair. We used a "host cell microsatellite stability assay" with the plasmid pZCA29 and found a 2.0-fold to 2.5-fold increase of microsatellite frameshift mutations (p < or = 0.002) in the two resistant sublines. This indicates microsatellite instability, the hallmark of an impaired DNA mismatch repair. The increased repair of oxidative DNA damage might mediate an increased chemoresistance through an improved repair of drug-induced DNA damage. In contrast, a reduced DNA mismatch repair might confer resistance by preventing futile degradation of newly synthesized DNA opposite alkylation damage, or by an inability to detect such damage and subsequent inability to undergo DNA-damage-induced apoptosis.     

Molecular analysis of DNA polymerase eta gene in Japanese patients diagnosed as xeroderma pigmentosum variant type

POLH mutations were identified in 16 Japanese patients, who were diagnosed, both clinically and at a cellular level, as being of the xeroderma pigmentosum variant type (XPV). While all the patients developed skin cancer with an average onset of the cancer at 45 years, in non-XP Japanese the onset was at over 70 years. All the cell strains from the patients were normal or slightly hypersensitive to UV and most of these showed enhanced UV sensitivity when the post-UV colony formation was performed in the presence of caffeine. Immunoprecipitation analysis with two kinds of anti-POLH protein antibodies revealed that cells from 13 patients did not show the 83 kDa POLH band and that cells from one patient had a faint 83 kDa band. All of these 14 cell strains, without a POLH band or with a weak POLH band, had mutations in the POLH gene. The IP analysis of the POLH protein revealed a very useful method for screening the patients suspected of XPV. Seven mutations in the POLH gene including three novel mutations were identified. Among the mutations detected, 11 alleles out of 28 (39%) were G490T mutations.     

Concordant loss of heterozygosity of DNA repair gene, hOGG1, in melanoma in situ and atypical melanocytic hyperplasia

Background:  One major risk factor for cutaneous melanoma is chronic sun-exposure and oxidative stress. Among various oxidative DNA damages, 8-oxoquanine is the most abundant and is potentially mutagenic if not sufficiently repaired. The human 8-oxoquanine DNA glycosylase 1 ( hOGG1 ) gene specifically repairs 8-oxoguanine, and this gene shows frequent loss of heterozygosity (LOH) in human tumors. In this study, we investigate whether hOGG1 LOH occurs in melanoma in situ (MIS) and adjacent atypical melanocytic hyperplasia (AMH).
Methods:  Twelve skin biopsies with MIS and adjacent AMH were included. DNA samples derived from manual microdissection of tissues were subjected to polymerase chain reaction amplification using three fluorescent-labeled microsatellite makers, followed by fragment analysis.
Results:  Five of 12 cases were informative for both telomeric (3S1297) and centromeric (3S1289 or 3S1300) markers, bordering the hOGG1 locus. Among them, four (80%) MIS and three (60%) AMH showed hOGG1 LOH at both markers.
Conclusions:  These results shows that LOH at hOGG1 gene is associated with MIS and AMH and suggest that the hOGG1 gene may play a role in melanocytic tumor progression.     

Recurrence of melanoma in the scar after excised Spitz nevus in a 17-year-old child

Melanoma in childhood is rare and its diagnosis is more difficult than in adults, as it often presents histologic features overlapping with the Spitz nevus. The authors report the case of a 17-year old boy who was first diagnosed with Spitz nevus, however, the final diagnosis made after the excision of the tumor arising in the scar was changed to melanoma. The case in this present study emphasizes the importance of the differential diagnosis of skin tumors in young patients.     

Schwannomatosis. An unusual variant of neurofibromatosis or a distinct clinical entity?

Multiple schwannomas have frequently been seen in patients with neurofibromatosis. Recently, the association of multiple cutaneous schwannomas, central nervous system tumors, and various neurologic deficits has been described in Japanese patients as a condition called schwannomatosis. We describe the first non-Japanese cases of schwannomatosis and compare and contrast this unusual condition with the well-known variants of neurofibromatosis. We conclude that the features of schwannomatosis are distinct and define a condition that does not fit into the current classification scheme of neurofibromatosis. The occurrence of multiple cutaneous schwannomas in the absence of cardinal features of neurofibromatosis may indicate the presence of central nervous system tumors or various neurologic deficits.     

'To repair or not to repair - no longer a question': repair of mitochondrial DNA shielding against age and cancer

Abstract: The role of mitochondria in energy production and apoptosis is well known. The role of mitochondria and particularly the role of the mitochondria's own genome, mitochondrial (mt) DNA, in the process of ageing were postulated decades ago. However, this was discussed, debated and more or less disposed of. Recent data from elegant mouse models now confirm that mutations of mtDNA do indeed play a central and pivotal role in the ageing process. Newer reports also indicate a possible role of mtDNA mutations in the carcinogenesis of several organs. But is damaged mtDNA repaired, or is it simply degraded and discarded? This question appears to be answered now. According to recent data, mitochondria possess functional repair mechanisms such as base excision repair, double‐strand break repair and mismatch repair, yet nucleotide excision repair has so far not been detected.