ANALYSIS OF SOMATOSTATIN RECEPTOR SUBTYPE MESSENGER-RNA EXPRESSION INHUMAN BREAST-CANCER

Somatostatin is a widely distributed inhibitory peptide with growth-in hibitory effects in several human tumours, including breast cancer, ra ising the possibility that it may have therapeutic potential. The effe cts of somatostatin are mediated via a family of cell-surface receptor s that differ in their tissue distribution, pharmacological properties and intracellular response mediators, suggesting that they mediate di fferent functions of the peptide. We have analysed the expression of s omatostatin receptor subtype (SSTR1-5) mRNA in normal and malignant br east tissue. Receptor expression was analysed by reverse transcription -polymerase chain reaction (RT-PCR) using receptor subtype-specific pr imers and by in situ hybridization (ISH) with riboprobes synthesized b y in vitro transcription of cloned PCR products. A total of 51 breast carcinomas, 36 samples of matched normal tissue, two axillary node met astases and eight normal/benign breast tissue samples were analysed. S STR2 expression was ubiquitous in both normal and malignant breast tis sue. Expression of SSTR5 was detected in approximately one-third of tu mour and normal tissue, but fewer than 13% of all tissues expressed SS TR1, 3 and 4. These data suggest that SSTR2 gene expression is ubiquit ous in breast cancer. Although this is unlikely to have diagnostic or prognostic significance, SSTR2-specific somatostatin analogues may hav e therapeutic potential in breast cancer.