Alteration of the CDKN2A (alias p16) tumor suppressor gene,
located on 9p21,
occurs frequently in familial and sporadic melanomas. Beside
CDKN2A, other genes
(e.g., CDKN2B, and ARF/p14(ARF), long considered distinct from
CDKN2A) on this
locus are often deleted or mutated in a large number of tumors
including glioma,
bladder cancer, and lung cancer. The aim of this study was to
evaluate the
deletion pattern of the 9p21 locus on a cell-by-cell basis in a
large number of
melanoma samples using fluorescence in situ hybridization
(FISH). In an analysis
of 81 primary lesions targeting the 9p21 region and chromosome 9
centromere, high
frequency of 9p21 loss (84%) was found. Deletion of 9p21 was
present in both
early- and late-stage melanomas with similar frequencies. Extra
9p21 copies were
rarely seen; they were always associated with polysomy 9 and
were observed only
in advanced stage melanomas (6 tumors). This FISH study
strengthens the
hypothesis that the loss of 9p21 occurs frequently in primary
melanoma, that the
deletion is present in early and late stages of the disease with
similar
frequency, and that it affects a large extent of the locus.
