Alterations in CDKN2A locus as potential indicator of melanoma predisposition in relatives of non-familial melanoma cases.
OBJECTIVE
To examine constitutional alterations of CDKN2A/p16INK4A locus as a potential indicator of melanoma predisposition among the first-degree relatives of patients with malignant melanoma.


METHODS
The study included eight families with a single member affected with melanoma. Members of the families were screened for allelic cosegregation with 9p21 region polymorphic markers IFNA, D9S126, and D9S104. The patient's tumors were screened for loss of heterozygosity (LOH) with the same markers, as well as for single strand conformational polymorphism (SSCP) variability of CDKN2A. In suspect cases, constitutional DNA was examined by SSCP and direct sequencing.


RESULTS
LOH was detected in four cases, and SSCP indicated variability in at least one CDKN2A exon in these tumor samples. In three of four LOH cases, the remaining allele cosegregated within the family, which was interpreted as a preliminary indicator of potential genetic predisposition. In one of these three families, we found constitutional CDKN2A mutations in the patient and one of the relatives. In the second family, only the patient had the constitutionally altered gene, whereas no constitutional CDKN2A alterations were detected in the third family. All significant mutations were different and had not been reported before.


CONCLUSIONS
We detected one case of melanoma predisposition among unaffected family members, which corresponded to statistical expectations for such a small number of screened families. Since constitutional mutations of CDKN2A exons have limited incidence, our stepwise approach seemed to be more informative and more affordable than straightforward CDKN2A sequencing of all subjects.
Levanat
Sonja
S
Division of Molecular Medicine, Ruder Bosković Institute, Bijenicka 54, 10000 Zagreb, Croatia. levanat@rudjer.irb.hr
Situm
Mirna
M
Crnić
Ivana
I
Marasović
Dujomir
D
Puizina-Ivić
Neira
N
Pokupcić
Nikola
N
Musani
Vesna
V
Komar
Arijana
A
Kubat
Milovan
M
Furac
Ivana
I
Karija-Vlahović
Monika
M
Krizanac
Simun
S
D000483:Alleles; D001483:Base Sequence; D001707:Biopsy, Needle; D017523:Croatia; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D019942:Genes, p16; D020022:Genetic Predisposition to Disease; D005820:Genetic Testing; D006801:Humans; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D008969:Molecular Sequence Data; D010375:Pedigree; D010865:Pilot Projects; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology
D004273:DNA, Neoplasm