Using a library of radioimmunoassays against essential sequences of human
progastrin and
procholecystokinin, we have examined the occurrence of
gastrin,
cholecystokinin, and their precursors in bronchogenic
adenocarcinomas, large-cell, small-cell, and
squamous-cell carcinomas (n = 17).
Progastrin and some of its bioactive (i.e., alpha-carboxyamidated) products were present in all
tumors, irrespective of histological classification. The concentration of
progastrin varied from 0.2 to 21.9 pmol/g tissue;
glycine-extended intermediates constituted less than 0.1 to 0.5 pmol/g; and bioactive, carboxyamidated
gastrin ranged from less than 0.1 to 6.1 pmol/g. Chromatography showed that the bioactive
gastrins were exclusively
gastrin-17 peptides, half of which were
tyrosine O-sulfated. Neither
procholecystokinin nor its processing products were found in the
tumor extracts. Six samples of nonneoplastic human lung tissue contained traces of
progastrin (range, less than 0.1-0.8 pmol/g), but neither bioactive
gastrins nor any
cholecystokinin. The results show that the
gastrin gene is expressed in all classes of
bronchogenic carcinomas. Due to incomplete posttranslational processing measurement of
progastrin may be necessary to detect such expression.