INDEPENDENT CLONES OF TRISOMY-12 AND RETINOBLASTOMA GENE DELETION IN JAPANESE B-CELL CHRONIC LYMPHOCYTIC-LEUKEMIA, DETECTED BY FLUORESCENCEIN-SITU HYBRIDIZATION

Trisomy 12 and a deletion of chromosome 13 are the most common chromos ome abnormalities in patients with B cell chronic lymphocytic leukemia (B-CLL). We determined the frequencies of these abnormalities in Japa nese B-CLL patients by FISH in interphase nuclei. Specimens from 42 pa tients were analyzed using both DNA probes specific to the centromeric region of chromosome 12 and the retinoblastoma (RE) gene. Among 42 pa tients, eight had trisomy 12 and 12 had the RE gene deletion. We found aberrations of trisomy 12 and the RE gene deletion in a totally diffe rent group of patients. This suggested that the trisomy 12 and the RE gene deletion occur in different clones and the presence of which in t he same patient may be rare. Furthermore, the frequency of trisomy 12 (19%) found in Japanese B-CLL was lower than that in Western countries (30-35%). On the contrary, the frequency of the RE gene deletion (28. 6%) was almost the same as in European B-CLL (30-35%). These results w ill be helpful in understanding the leukemogenesis of B-CLL.