Abstract
Somatostatin is a widely distributed inhibitory peptide with growth-inhibitory effects in several human tumours, including breast cancer, raising the possibility that it may have therapeutic potential. The effects of somatostatin are mediated via a family of cell-surface receptors that differ in their tissue distribution, pharmacological properties and intracellular response mediators, suggesting that they mediate different functions of the peptide. We have analysed the expression of somatostatin receptor subtype (SSTR1-5) mRNA in normal and malignant breast tissue. Receptor expression was analysed by reverse transcription-polymerase chain reaction (RT-PCR) using receptor subtype-specific primers and by in situ hybridization (ISH) with riboprobes synthesized by in vitro transcription of cloned PCR products. A total of 51 breast carcinomas, 36 samples of matched normal tissue, two axillary node metastases and eight normal/benign breast tissue samples were analysed. SSTR2 expression was ubiquitous in both normal and malignant breast tissue. Expression of SSTR5 was detected in approximately one-third of tumour and normal tissue, but fewer than 13% of all tissues expressed SSTR1, 3 and 4. These data suggest that SSTR2 gene expression is ubiquitous in breast cancer. Although this is unlikely to have diagnostic or prognostic significance, SSTR2-specific somatostatin analogues may have therapeutic potential in breast cancer.
Highlights
Amplifiable cDNA, as determined by the ability to amplify actin, was obtained from 51 primary breast cancers, 36 samples of matched normal breast tissue, two axillary node metastases and eight samples of benign breast tissue
Histology Most tumours were invasive ductal carcinomas (86%), 10% were of special histological type and 4% were pure ductal carcinoma in situ (DCIS)
The apparent lower sensitivity of reverse transcription-polymerase chain reaction (RT-PCR) compared with in situ hybridization (ISH) probably results from the relative paucity of epithelial cells in normal breast tissue compared with tumour
Summary
Tissue collectionFresh tissue samples were obtained from patients undergoing surgery for breast disease. Total cellular RNA was isolated from frozen tissue by phenol-guanidinium extraction (Chomczynski and Sacchi, 1987) using a commercially available kit (RNazol B, Biogenesis). All RNA samples were, treated with RNAase-free DNAase before reverse transcription. Total RNA was incubated for I h at 37°C in a 50-,ul reaction containing 40 mM Tris-HCl, pH 7.9, 10 mm sodium chloride, 6 mm magnesium chloride, 10 mm calcium chloride, 25 units RNAase-free RQ1 DNAase and 40 units RNAase inhibitor (all reagents from Promega). Following digestion of DNA, DNAasefree RNA was extracted with phenol-chloroform, precipitated with 100% ethanol and 2.5 M sodium acetate (pH 4) at -20°C overnight and taken up in 50 jil of DEPC-treated, RNAase-free water. The final concentration of DNA-free RNA was determined by absorbance at 260X (1 OD = 40 jig ml-') and solutions were stored at -80°C
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
