Merbs S L, Sidransky D
Wilmer Ophthalmological Institute, Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
Invest Ophthalmol Vis Sci. 1999 Mar;40(3):779-83.
To define more clearly the role of the tumor suppressor gene p16 in uveal melanoma by determining the relative contribution of all known mechanisms of p16 inactivation in this tumor.
A comprehensive genetic analysis of the p16 gene was performed in 33 primary sporadic ciliochoroidal and choroidal melanomas. Fourteen highly polymorphic microsatellite markers surrounding the p16 locus on chromosome 9p21 were used for the microsatellite analysis. Sequence analysis of the p16 gene was performed on those tumors with 9p21 loss of heterozygosity. To investigate methylation as an alternative mechanism of inactivation of p16, methylation-specific polymerase chain reaction was performed on all tumor DNA samples.
Loss of heterozygosity (LOH) was found in 8 of 33 (24%) uveal melanomas. No evidence of a second region of LOH that did not include the p16 locus was found. Four cases had hemizygous losses including markers both distal and proximal to p16. Homozygous deletion of the p16 gene was detected in the 4 remaining cases by microsatellite analysis. Sequence analysis revealed no p16 mutations in the tumors with hemizygous loss of p16. Methylation of the 5' CpG island of p16 was found in one tumor with 9p21 LOH and in another without LOH.
p16 inactivation by HD or methylation occurs in 27% of uveal melanomas, representing the most common molecular genetic alteration identified thus far in uveal melanoma.
通过确定肿瘤抑制基因p16失活的所有已知机制在葡萄膜黑色素瘤中的相对作用，更清晰地界定p16在葡萄膜黑色素瘤中的作用。
对33例原发性散发性睫状体脉络膜和脉络膜黑色素瘤进行p16基因的综合遗传分析。使用位于9号染色体p21上p16基因座周围的14个高度多态性微卫星标记进行微卫星分析。对那些出现9p21杂合性缺失的肿瘤进行p16基因的序列分析。为了研究甲基化作为p16失活的另一种机制，对所有肿瘤DNA样本进行甲基化特异性聚合酶链反应。
在33例（24%）葡萄膜黑色素瘤中发现8例杂合性缺失（LOH）。未发现不包括p16基因座的第二个杂合性缺失区域的证据。4例有半合子缺失，包括p16远端和近端的标记。通过微卫星分析在其余4例中检测到p16基因的纯合缺失。序列分析显示，在p16半合子缺失的肿瘤中未发现p16突变。在1例出现9p21杂合性缺失的肿瘤和另1例未出现杂合性缺失的肿瘤中发现p16的5'CpG岛甲基化。
27%的葡萄膜黑色素瘤发生通过纯合缺失或甲基化导致的p16失活，这是迄今为止在葡萄膜黑色素瘤中鉴定出的最常见的分子遗传学改变。
