thesis
The role of somatostatin receptors in breast and pancreatic cancer
- Publication date
- 28 September 1994
- Publisher
- Somatostatin, a hormone which has an inhibitory influence on several physiological
processes, is a small peptide consisting of 14 amino-acids, and was first isolated from the
hypothalamus of the rat. Soon after, somatostatin was found in numerous other organs, such
as the brain, stomach, intestines, pancreas, thyroid, thymus and bronchi, from which it could
be extracted. Natural somatostatin has a very short half-life and can only be administered
intravenously. The development of several longacting analogues of somatostatin facilitated
diagnostic procedures and therapy involving somatostatin and its receptors.
One of the first and best known effects of the hormone somatostatin is inhibition of the
release of growth hormone by the pituitary gland. Other, mainly inhibitory effects of
somatostatin have been described recently, including a direct inhibitory effect on the growth
of tumour cells. Somatostatin receptors (SS-R's), present on tumour and pituitary celis,
mediate this inhibitory effect as well as release of growth hormone. The analogue octreotide,
used in this study, binds to SS-R's on normal and tumour cells. Autoradiography, using '251_
Tyr-octreotide, was utilized to localize receptors for somatostatin in vitro. These receptors
were found in several neuroendocrine tumours, as well as in breast carcinomas and islet cell
tumours of the pancreas.
The aim of this study was to assess the possibility of visualizing SS-R's in vivo, using
octreotide labelled with radioactive "'Indium and diethylene-triaminopentaacetic acid (DTPA)
as a carrier (octreoscan).