A. Imdahl et al., EXPRESSION OF GASTRIN, GASTRIN CCK-B AND GASTRIN/CCK-C RECEPTORS IN HUMAN COLORECTAL CARCINOMAS/, Journal of cancer research and clinical oncology, 121(11), 1995, pp. 661-666
To investigate further the presence of an autocrine proliferative loop
involving gastrin in colorectal carcinomas and to clarify the recepto
r responsible, 102 human colorectal carcinomas and 10 hepatic metastas
es were investigated for the expression of the genes encoding gastrin,
the gastrin/CCK-B receptor and the gastrin/CCK-C receptor. Levels of
RNA expression were assayed by RNase protection assay. In addition, ga
strin/CCK receptors on crude membranes of tumour tissue were assayed b
y radioligand binding. High-affinity,gastrin/CCK-B receptors were not
detected in any of the carcinomas investigated, whereas in 36% low-aff
inity binding was observed, consistent with the expression of the gast
rin/CCK-C receptor. RNase protection assay detected the RNA for the ga
strin/CCK-B receptor in 11% of the carcinomas investigated, whereas th
e RNA for the gastrin/CCK-C receptor was demonstrated in 75% and the R
NA for gastrin in 86% of the carcinomas investigated. These results co
nfirm the recent demonstration of progastrin fragments in colorectal c
arcinomas. One possible explanation for progastrin expression is that
such progastrin fragments may participate in an autocrine proliferativ
e loop. The receptor involved in this loop is more likely to be the lo
w-affinity gastrin/CCK-C receptor rather than the gastrin/CCK-B recept
or, which is rarely expressed in colorectal carcinomas.