Fine mapping of chromosome 3 in uveal melanoma: identification of a minimal region of deletion on chromosomal arm 3p25.1-p25.2.

To identify minimal common areas of allelic loss on chromosome 3, we have mapped both arms of the chromosome in 21 uveal melanomas that did not show monosomy 3 in our previous allelotype study. DNA was isolated from microdissected paraffin sections and amplified by PCR. In an initial screening, 14 microsatellite markers on chromosomal arm 3p and 13 on chromosomal arm 3q were used. Loss of heterozygosity for at least one marker was found in 9 of 21 tumors (43%) on 3p and 8 of 21 tumors (38%) on 3q. The initial analysis defined two common regions of allelic loss on 3p, a 7.3-Mb region between markers D3S1263 and D3S3510 spanning 3p25.3-24.3 and a larger region between markers D3S1578 and D3S1284. The two common regions of allelic loss were further mapped with an additional 14 microsatellite markers. A 1.4-Mb minimal region of allelic loss was identified between microsatellite markers D3S3610 and D3S1554 on 3p25.1-3p25.2. A total of 10 tumors had allelic loss in this region; 2 of these tumors had corresponding putative homozygous deletions. These homozygous deletions may further narrow the region of interest to 0.1 Mb. This 1.4-Mb minimum region of deletion includes several genes that might be involved in the carcinogenesis of uveal melanoma as well as other important tumor types.