Production of immunoreactive calcitonin and some other tumor markers by established human carcinoma cell lines.

Out of seven human carcinoma cell lines (M7609, CCK-81, FCC-1, RPMI#4788, QGP-1, HLC-1, and KNS-62), 4 cell lines were found to produce immunoreactive calcitonin (ICT), a potential tumor marker for various malignancies. During a 7-day culture, 1.4 X 10(5) QGP-1, RPMI#4788, HLC-1, and KNS-62 cells secreted 7,000 pg, 500 pg, 400 pg, and 400 pg of ICT in the medium, respectively. The production of ICT by QGP-1 cells was increased by addition of pentagastrin or calcium gluconate. Three different components of ICT (peak I, molecular weight greater than 40,000; peak II, 14,000-18,000; peak III, 3,400) were detected by gel filtration of the QGP-1 spent medium. In a competitive inhibition-type radioimmunoassay of serial dilutions of each ICT component, peak III component showed very similar immunoreactivity to synthetic calcitonin. However, the other two components gave clearly different immunoreactivities from the peak III component and showed very similar immunoreactivities to each other. All the cell lines were further screened for synthesis of 7 other tumor markers, carcinoembryonic antigen, nonspecific cross-reacting antigen, CA19-9, tissue polypeptide antigen, alpha-fetoprotein, beta 2-microglobulin and ferritin. Every cell line produced 2 to 6 markers concomitantly, and various combinations of positive markers were found among the cell lines.