Northern blot and RNAse protection assays previously failed to detect
bombesin-like peptide (BLP) receptors in normal human lung tissue, but
by RT/PCR cultured human bronchial epithelial (HBE) cells expressed a
ll three BLP receptor subtypes, predominantly neuromedin B (NMB) recep
tor. By RT/PCR, we found expression of all three BLP receptor subtypes
by human lung tissue and confirmed NMB receptor expression in six out
of six HBE samples. However, transformed HBE BEAS B2B cells expressed
only gastrin-releasing peptide (GRP) receptors; saturable, high-affin
ity (K-d = 3.5 nM) specific [I-125]GRP binding confirmed functional GR
P receptor, with M(r) = 75 kDa and immunologic cross-reactivity with G
RP receptor from human small-cell lung carcinoma (SCLC) NCI-H345 cells
. Altered regulation of BLP receptors may accompany transformation of
normal lung cells to cancer.