上皮性腫瘍細胞におけるc-kit及びkit ligandの発現

kit ligand (KL), which was identified as the ligand for the tyrosine kinase receptor encoded by the proto-oncogene c-kit, has recently been shown to play an important role in prolifera- tion of primitive hematopoietic progenitor cells. KL is found both on the cell surface and in solu- tion, and alternative splicing has yielded two types of KL mRNAs. RT-PCR and Northern blot anal- ysis were performed on human epithelial tumors to determine whether c-kit and KL were expressed there. The results are summarized as follows. 1. KL mRNA was expressed in a wide variety of tissues including the placenta, spleen, liver, lung, kidney, stomach, duodenum and colon. The ratio of the expression level of the two types of KL mRNAs was almost constant in all those tissues. 2. Four hepatocellular carcinoma cell lines and a hepatoblastoma cell line expressed detectable levels of KL, but did not express c-kit 3. Among five colon carcinoma cell lines, Colo320DM and DLD-1 expressed both c-kit and KL. The expression of KIT protein was also confirmed by flow cytometry. 4. In Colo320DM, neither amplification nor rearrangement of c-kit gene was found