Gliomas constantly overexpress the receptor subtype SST2 for the inhibitory peptide somatostatin. Since somatostatin or metabolically stable agonists like octreotide have an antiproliferative and antisecretory potential for the treatment of SST2-expressing tumors, we evaluated the molecular integrity of SST2 in gliomas on the DNA, mRNA and protein levels. Sequencing of about 1800 bases from the SST2 gene in nine gliomas and five control samples revealed no mutations, but polymorphisms were detected in the 5'-region irrespective of the malignancy of the sample. Gliomas and the human glioma cell line U343 expressed mRNA for the receptor splice variant SST2A with a size of about 4.2 kb. A novel antibody generated against an extracellular part of the SST2 amino acid sequence strongly reacted with an 75-kDa protein in membranes from glioma or meningioma cells and-much weaker-normal rat astrocytes. The receptor could be immunostained on the surface of intact glioma cells or (weaker) astrocytes at the light and electron microscopic level. These results show that the somatostatin receptor SST2 is non-mutated in gliomas and has similar molecular properties as in non-malignant cells.
Copyright 1999 Elsevier Science B.V.