Original article 185 CDKN2A and CDK4 variants in Latvian melanoma patients: analysis of a clinic-based population Dace Pjanova a , Ludmila Engele b , Juliette A. Randerson-Moor d , Mark Harland d , D. Timothy Bishop d , Julia A. Newton Bishop d , Claire Taylor e , Tadeusz Debniak f , Jan Lubinski f , Regina Kleina c and Olita Heisele a 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. Melanoma Res 17:185–191  c 2007 Lippincott Williams & Wilkins. Melanoma Research 2007, 17:185–191 Keywords: CDKN2A, CDK4, germline, melanoma, mutation, polymorphism a Latvian Biomedical Research and Study Centre, b Latvian Oncological Center, c Department of Pathological Anatomy, Riga Stradins University, Riga, Latvia, d Genetic Epidemiology Division, e Mutation Detection Facility, Cancer Research UK Clinical Centre, St. James’s University Hospital, Leeds, UK and f Department of Genetics and Pathology, International Hereditary Cancer Center, Szczecin, Poland Correspondence to Dace Pjanova, MSc, Latvian Biomedical Research and Study Centre, Ratsupites str.1, Riga LV-1067, Latvia Tel: +371 7808215; fax: 371 7442407; e-mail: dace@biomed.lu.lv Received 27 July 2006 Accepted 23 November 2006 Introduction Hereditary predisposition to cutaneous malignant mela- noma has been recognized since the 19th century [1]. To date, two high penetrance melanoma susceptibility loci have been identified [2,3]. One locus is CDKN2A, on chromosome band 9p21, coding for two tumour suppres- sor proteins p16INK4a and p14ARF. The p16INK4a protein is transcribed by CDKN2A exons 1a, 2, and 3, whereas p14ARF is transcribed from an alternative first exon (1b) but utilises the same second and third exons in a different reading frame. Both of these proteins are involved in cell-cycle regulation (reviewed in [4]). Germline mutations of CDKN2A have been recorded with varying frequencies in melanoma families worldwide, and the majority of mutations have been observed in CDKN2A exons 1a and 2, affecting the p16INK4a transcript [5]. Moreover, evidence exists both for and against poly- morphisms in CDKN2A acting as low penetrance genes. Two common 3 0 untranslated region polymorphisms, 500 C/G (c.*29C > G) and 540 C/T (c.*69C > T), have been described in association with melanoma [6] or melanoma progression [7], but there was no association in another study [8]. The third most common CDKN2A polymor- phism is the Ala to Thr substitution at codon 148, Ala148Thr (c.442G > A). This variant has also been reported to be both associated [9,10] and not associated with an increased risk of melanoma [11], although in different populations. The presence of a small number of reported deletions or mutations that specifically affect p14ARF rather than p14ARF and p16 [12–14], indicates that mutations affecting this protein only also act independently as rare, high penetrance melanoma susceptibility genes. The other known melanoma susceptibility gene is CDK4, on chromosome band 12q14. CDK4 encodes 0960-8931  c 2007 Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.