TRISOMY 12 IN CHRONIC LYMPHOID LEUKEMIAS - A METAPHASE AND INTERPHASECYTOGENETIC ANALYSIS

Trisomy 12 has been shown to be one of the most common chromosome abno rmalities in chronic lymphoid leukemias of B-cell origin, and some stu dies suggested that it predicts poor overall survival. We have prospec tively studied 42 patients with B-cell chronic lymphocytic leukemia (B -CLL) and three patients with B-prolymphocytic leukemia (B-PLL) for th e incidence of trisomy 12 and other chromosome 12 aberrations applying fluorescence in situ hybridization (ISH) and conventional G-banding a nalysis. Dual-color hybridization experiments using centromere-12-spec ific DNA probes were performed for interphase cytogenetics. A subset o f patients (n = 11) was analyzed using a DNA library for painting of c hromosome 12. The incidence of trisomy/partial trisomy 12 was 18% (814 5 patients; 6142 with B-CLL and 2/3 with B-PLL) by fluorescence ISH, a nd 11% (5145 patients; 4142 with B-CLL including one patient with part ial trisomy 12q13-qter, and 113 with B-PLL) on G-banding analysis. Fou r patients with trisomy 12 were detected by ISH alone. One of these pa tients only had 4.5% interphase cells with three fluorescence signals indicating the presence of a small subclone with trisomy 12. On G-band ing analysis, three of the four patients had a normal karyotype, and o ne patient had no analyzable metaphases. In conclusion, fluorescence I SH to interphase nuclei is a sensitive method for detecting trisomy 12 in patients with chronic lymphoid leukemias.