Expression of receptor tyrosine kinase HTK (hepatoma transmembrane kinase)and HTK ligand by human leukemia-lymphoma cell lines

HTK (hepatoma transmembrane kinase) is a receptor tyrosine kinase belonging to the EPH subfamily of tyrosine kinases. Binding of its ligand (HTKL) res ults in tyrosine phosphorylation of HTK. In the present study, we analyzed the possible involvement of this ligand-receptor signalling system in hemat opoiesis by examining the expression of both HTK and HTKL in a large and co mprehensive panel of 70 continuous human leukemia-lymphoma. cell lines. HTK and HTKL mRNA expression were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). HTK mRNA was detected in 68/70 cell lines; 58/70 cell Lines were positive for HTKL mRNA expression; consequently, co-express ion of both receptor and ligand was demonstrated in the majority of cell li nes. Collectively, the wide-spread expression suggests a role for this liga nd-receptor pair in hematopoietic development and/or function. Investigatio n of the details of signal transduction pathway that is activated by the HT K tyrosine kinase will help to define the exact biological function of the HTK-HTKL system.