Expression of cytokeratin 19 mRNA in human lung cancer cell lines

The present study was designed to clarify the mechanism by which some lung cancer cell lines can produce cytokeratin 19 (CK19) fragment and others can not. We hypothesized that some lung cancer cell lines which cannot release CK19 express an incomplete sequence of CK19 mRNA. Expression of mRNA was ev aluated by RT-PCR using several primer pairs for CK19, CK19 in the culture supernatant was measured by an immuno radiometric assay. CK19 protein synth esis was evaluated by Western immunoblot and immunohistochemistry. Among 16 lung cancer cell lines, 7 released significant amounts of CK19 in the supe rnatant. In some cell lines, expression of CK19 mRNA was observed only in s ome combinations of primers, suggesting that incomplete mRNA was expressed. 3'-RACE analysis detected amplified products of a shorter size compared wi th normal amplified products in cell lines which expressed incomplete CK19 mRNA, suggesting that 3'-ends of mRNA for CK19 were deleted. Results of Wes tern immunoblot and immuno-histochemical staining using anti-human CK19 mon oclonal antibody completely correlated with the results on CK19 levels in c ulture supernatants as well as with complete expression of mRNA. We conclud e that levels of CK19 closely relate to the expression of complete mRNA for CK 19. (C) 1999 Wiley-Liss, Inc.