EXPRESSION OF C-TERMINAL SRC KINASE IN HUMAN COLORECTAL-CANCER CELL-LINES

C-terminal src kinase (CSK) is a cytoplasmic protein which decreases a ctivities of the Src family protein-tyrosine kinases. We produced a po lyclonal antibody specific for CSK and analyzed the expression of CSK by immunoblotting in two human colorectal normal cell lines and eighte en cancer cell lines. CSK was detected in both the two normal and all the eighteen cancer cell lines. The expression of CSK obtained from hu man colorectal cancer cell lines was greater than that from human colo rectal normal cell lines in most cases. The elevated expression of CSK in human colorectal cancer cell lines appeared to correspond to the e levated p60(c-src) (c-Src) and p62(c-yes) (c-Yes) protein-tyrosine kin ase activities found in other studies. Thus, CSK may not have an anti- oncogenic role to play through the negative regulation of Src family k inases in colorectal carcinogenesis.