EXPRESSION OF THE TCL1 GENE AT 14Q32 IN B-CELL MALIGNANCIES BUT NOT IN ADULT T-CELL LEUKEMIA

The TCL1 gene was recently cloned as a candidate target within the 14q 32.1 breakpoint cluster region observed in T-cell malignancies. We exa mined the TCL1 gene expression in 21 patients with adult T-cell leukem ia (ATL) and 5 cell Lines, because ATL is reported to have frequent ch romosome 14 band (q32 aberrations, However, 20 of the ATL patients and all 5 cell lines lacked any TCL1 expression on northern blot analysis , and TCL1 transcripts were only very faintly detected in the remainin g one patient, Expansion of our analysis to include other types of hem atopoietic malignancies revealed strong expression of the TCL1 gene in almost all tumor cells of B-cell lineage except myelomas. However no TCL1 signals were encountered in cells of T-cell or myeloid lineages. In normal human tissues TCL1 was found to be expressed in the spleen. lymph nodes and B-lymphocytes of peripheral blood. These results indic ate that TCL1 is not a major target gene for ATL, but that it may play a role in B-cell differentiation and proliferation.