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Summary 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.

Summary Somatostatin analogues may be useful novel agents in the systemic treatment of advanced colorectal cancer, as somatostatin inhibits proliferation in a wide variety of cell types. Here, we report the expression profiles of somatostatin receptor mRNAs in 32 pairs of malignant and normal colonic epithelia. Receptor subtype 2 (hSSTR2) mRNA was detected throughout nearly 90% of both malignant and normal tissue by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Subtype 5 (hSSTR5) mRNA was detected in 46% and 45% of tumour and mucosal samples respectively, but in 75% (9/12) of early-stage tumours (tubulovillous adenomas, Dukes' A and B) compared with 31% (5/16) of late-stage tumours (Dukes' C and 'D' tumours), 0.05>P>0.025 (X2 with Yates' correction). There was also reduced expression of hSSTR5 in samples of metastatic tumour (11%, 1/9) compared with all tumour samples (56%, 18/32) 0.025>P>0.01 (X2 with Yates' correction). Other hSSTRs (1, 3 and 4) were expressed infrequently. Thus, hSSTR2 expression is retained after malignant transformation in colonic epithelium and, although it may potentially be a target for antiproliferative therapy, its ubiquitous expression militates against this. hSSTR5 warrants investigation as a tumour suppressor.

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Exogenous growth hormone has different actions depending on the method of administration. However, the effects of different modes of administration of the placental variant of growth hormone on growth, body composition and glucose metabolism have not been investigated. In this study, we examined the effect of pulsatile vs. continuous administration of recombinant variant of growth hormone in a normal mouse model. Female C57BL/6J mice were randomized to receive vehicle or variant of growth hormone (2 or 5 mg/kg per day) by daily subcutaneous injection (pulsatile) or osmotic pump for 6 days. Pulsatile treatment with 2 and 5 mg/kg per day significantly increased body weight. There was also an increase in liver, kidney and spleen weight via pulsatile treatment, whereas continuous treatment did not affect body weight or organ size. Pulsatile treatment with 5 mg/kg per day significantly increased fasting plasma insulin concentration, whereas with continuous treatment, fasting insulin concentration was not significantly different from the vehicle-treated control. However, a dose-dependent increase in fasting insulin concentration and decrease in insulin sensitivity, as assessed by HOMA, was observed with both modes of treatment. At 5 mg/kg per day, hepatic growth hormone receptor expression was increased compared to vehicle-treated animals, by both modes of administration. Pulsatile variant of growth hormone did not alter the plasma insulin-like growth factor-1 concentration, whereas a slight decrease was observed with continuous variant of growth hormone treatment. Neither pulsatile nor continuous treatment affected hepatic insulin-like growth factor-1 mRNA expression. Our findings suggest that pulsatile variant of growth hormone treatment was more effective in stimulating growth but caused marked hyperinsulinemia in mice.