Je. Taylor et al., DETECTION OF SOMATOSTATIN RECEPTOR SUBTYPE-2 (SSTR2) IN ESTABLISHED TUMORS AND TUMOR-CELL LINES - EVIDENCE FOR SSTR2 HETEROGENEITY, Peptides, 15(7), 1994, pp. 1229-1236
The somatostatin receptor subtype 2 (SSTR2) was detected in a wide ran
ge of human and rat tumors using in vitro receptor binding ([I-125]MK-
678), receptor gene expression analysis, and immunoblotting techniques
. The highest receptor concentrations were observed in the rat AR42J p
ancreatic and human small cell lung cancer (SCLC) cell lines, NCI-H69
and NCI-H345, with much lower levels detected in breast, prostate, mel
anoma, and hepatic tumors. Several human pancreas tumors were devoid o
f SSTR2. For all tumors showing detectable [I-125]MK-678 binding, SSTR
2 receptor mRNA was expressed. Furthermore, a mRNA transcript correspo
nding to a truncated isoform of SSTR2 was detected at low levels in th
e human SCLC NCI-H69 cell line, and likely represents a human homologu
e of rodent SSTR2B. Immunoblotting analysis using the SSTR2-specific a
ntibody, 2e3, detected multiple immunoreactive protein species, includ
ing a predominant 150-kDa molecule, which could be blocked by the SSTR
2-derived 2e3 peptide. Somatostatin (SRIF) peptides with high SSTR2 af
finity and antiproliferative properties were potent inhibitors of [I-1
25]MK-678 binding to several tumor types, suggesting that they may exe
rt antitumor effects via the SSTR2 receptor.