Germline mutations of the CDKN2A and CDK4 genes explain a significant proportion of familial melanoma. To date, there have been few published estimations of the prevalence of such mutations in sporadic melanoma patients. In this study, we investigated CDKN2A and CDK4 exon 2 for germline mutations in 125 consecutive cutaneous malignant melanoma patients recruited through the Latvian Oncological Center, using amplicon melting analysis and sequencing. No disease-related CDKN2A germline mutations were identified in any of the melanoma patients analysed but the previously described CDK4 mutation, Arg24His, was found in one patient with a family history of melanoma. CDKN2A polymorphisms were studied as putative low penetrance susceptibility genes. The proportion of cases with polymorphisms in this Latvian melanoma population was Ala148Thr (c.442G>A) (6%), 500 C/G (c.*29C>G) (18%), and 540 C/T (c.*69C>T) (20%); however, only the frequency of the Ala148Thr polymorphism was higher in melanoma patients than in 203 controls (6 versus 1%, P=0.03). Ala148Thr has also been reported in association with melanoma in a Polish series but not in an English series. We therefore examined the Ala148Thr carrier's haplotype in 10 Latvian and 39 Polish samples. No significant difference was seen between these populations and the predominant haplotype observed in English samples, giving no indication that the discrepancy could be explained by population differences in linkage disequilibrium. In summary, our results show that germline mutations at the CDKN2A locus are rare in sporadic melanoma in Latvia. The study does, however, provide some additional evidence for a role for the CDKN2A polymorphism Ala148Thr as a low penetrance susceptibility gene. The detected CDK4 exon 2 mutation was found in only the seventh family identified worldwide with a germline CDK4 mutation.

Malignant melanomas usually have an unfavourable prognosis and poor response to chemotherapy. Deregulation of cell proliferation, programmed cell death and intercellular interactions are among several important mechanisms that might lead to malignant transformation of melanocytes and melanoma progression. The S100A1, S100B, Bcl-2 and CD44 antigens have all been described as being involved in different processes of melanoma progression. The expression of these antigens, as well as the rate of cell proliferation, was analyzed retrospectively in melanocytic tumours from 126 patients (32 males and 94 females, age ranging from 11 to 91 years). The series included benign (45 intradermal, 27 compound and eight displastic naevi) and malignant (39 primary and 14 metastatic) melanocytic tumours. The proliferating rate assessed by Ki-67 staining was lower in naevi than in melanomas, with a correlation coefficient of r = 0814. There was no overlap for rate of proliferation between benign and malignant tumours. The expression of S100A1 was low in benign melanocytic tumours and increased in malignant melanomas (r = 0.61). In contrast, a higher percentage of S100B antigen-positive cells were observed in benign melanocytic lesions than in melanomas (Pearson correlation coefficient, 0.627). In addition, positive immunostaining for S100B antigen in malignant melanomas corresponded with the areas with increased proliferating rate. The expression of Bcl-2 was lower in melanomas than in benign melanocytic tumours (r = -0.53). Bcl-2-negative areas within melanomas had an increased proliferating rate. The expression of CD44 showed a large variation both in benign and malignant melanocytic tumours. CD44 antigen expression was higher in melanomas with known metastases than in those without metastases, but this difference was not statistically significant.

The clinical behaviour of melanoma is often unpredictable using clinical and histological criteria. Tumour cell markers related to cell cycle regulation, apoptosis, cell-cell interactions and cell proliferation might improve the possibility of predicting the clinical course of melanoma. The aim of the present study was to refine prognostic criteria by an immunocytochemical investigation of CD44, CD40, bcl-2 antigens and cell proliferation in tumour cells aspirated from metastases of malignant melanoma. CD40 is a cell surface receptor shown to be expressed by lymphomas as well as carcinomas, and is thought to play a central role in the process of tumour progression. CD44 is a transmembrane glycoprotein, which is involved in growth signal transmission of importance in the binding of tumour cells to endothelium, cell migration and enhancement of cell motility, which makes it of interest to study in relation to the metastasizing capacity of tumours. The bcl-2 protein is active in the process of programmed cell death (apoptosis) as an antiapoptotic agent and its expression may reflect tumour progression. Mean/median percentages of tumour cell positivity were 8.5/3.0 for CD40, 76.1/86.3 for CD44 and 7.4/3.3 for bcl-2. A significant correlation was observed between expression of apoptosis-associated bcl-2 antigen and overall survival (r = 0.33). The CD44 positive cell fraction was higher in patients with short overall survival than those with long survival but this difference was not statistically significant. The expression of CD40 did not correlate with overall survival. The mean/median proliferation fraction assessed by MIB-1 monoclonal antibody was 25.8/23.9 and showed a significant correlation with survival after diagnosis of melanoma metastasis (r = 0.32). Lack of bcl-2 expression and a high proportion of tumour cells expressing Ki-67 antigen are predictors of poor prognosis that are independent of the traditionally accepted Breslow's thickness of the primary melanomas.

Triploidy in cancer is associated with poor prognosis but its origins remain unclear. Here, we attempted to differentiate between random chromosomal and whole genome origins of cancer triploidy. malignant and 5 benign tumour cohorts (2928 karyotypes) extracted from the Mitelman Database, comparing the triploid fraction was observed in all malignant tumour types, being especially high in seminoma. For all tumour types, X XXY, correlated strongly with near-diploidy, and did not correlate with near component with a doubled X especially notable in colon adenoma. Principal Component Analysis revealed a non random correlation structure shaping the X tumour types. We suggest that doubling of the maternal genome followed by pedogamic fusion with a paternal genome (a possible mimic of the fertilization aberration, 69, XXY digyny) associated with meiotic reprogramming may be responsible for the observed rearrangements of genome complements leading to cancer triploidy. The relatively frequent loss of the Y-

Triploidy in cancer is associated with poor prognosis, but its origins remain unclear. Here, we attempted to differentiate between random chromosomal and whole-genome origins of cancer triploidy. In silico meta-analysis was performed on 15 male malignant and five benign tumor cohorts (2928 karyotypes) extracted from the Mitelman Database, comparing their ploidy and combinations of sex chromosomes. A distinct near-triploid fraction was observed in all malignant tumor types, and was especially high in seminoma. For all tumor types, X-chromosome doubling, predominantly observed as XXY, correlated strongly with the near-triploid state (r ≈ 0.9, p < 0.001), negatively correlated with near-diploidy, and did not correlate with near-tetraploidy. A smaller near-triploid component with a doubled X-chromosome was also present in three of the five benign tumor types, especially notable in colon adenoma. Principal component analysis revealed a non-random correlation structure shaping the X-chromosome disomy distribution across all tumor types. We suggest that doubling of the maternal genome followed by pedogamic fusion with a paternal genome (a possible mimic of the fertilization aberration, 69, XXY digyny) associated with meiotic reprogramming may be responsible for the observed rearrangements of genome complements leading to cancer triploidy. The relatively frequent loss of the Y-chromosome results as a secondary factor from chromosome instability.