Expression of the human T-cell-specific tyrosine kinase YT16 (lck) message in leukemic T-cell lines

To evaluate the role of the human T-cell-specific tyrosine kinase lck (YT16), we measured the levels of lck expression in thymocytes, peripheral T-cells, and leukemia T-cell lines which are arrested at different stages of thymic differentiation. The results indicate that higher levels of the lck message can be found in total thymocytes and T-cells arrested at Stage III (thymocytes that have rearranged their alpha, beta, and gamma chain T-cell receptor genes). A 20-fold lower level of these transcripts, however, can be found in cells derived from Stage I cells (thymocytes with germline alpha, beta, and gamma genes), 4 times less messages in Stage II cells (thymocytes with rearranged gamma and beta chain genes, but with germline alpha chain genes), and a 4-fold lower amount of RNA in Stage IV cells (mature lymphocytes). Culture of these cells with a variety of inducing reagents indicated that leukemia cell lines of only Stages I and II can be induced to increase their levels of YT16 expression by the addition of tetradecanoyl phorbol-13-acetate. These results suggest that there may be a developmental regulation of these tyrosine kinase messages during T-cell ontogeny. The high level of these transcripts in more mature T-cell leukemia lines suggests that they may primarily play a role in the proliferative controls of these cells.