EXPRESSION OF SOMATOSTATIN RECEPTOR SUBTYPES IN HUMAN BRAIN-TUMORS

Expression of mRNA for the 5 somatostatin receptors (sst(1-5)) was cha racterized by Northern blot and RT-PCR analysis in 20 meningioma and 9 glioma samples. sst(1) mRNA was detectable by Northern blots of poly- A(+) RNA in meningiomas but not gliomas. In contrast, sst(2) mRNA was readily detected by Northern blots of total RNA as a major 2.3 kb tran script and 2 minor 4.3 kb and 8 kb transcripts in all meningiomas and 6 out of 9 gliomas. Quantitation of the 2.3 kb sst(2) mRNA showed that 15 out of 20 tumors expressed 1.3- to 33-fold higher levels than cont rol normal human brain. Mean sst(2) mRNA for the 20 meningioma samples was 978% that of normal brain. Three gliomas showed 7- to 14-fold hig her sst(2) mRNA than normal brain whereas the remaining samples displa yed very low or undetectable levels. Immunocytochemistry of meningioma and glioma samples, with a sst(2)-specific antibody revealed immunore activity in tumor cells and peritumoral tissue, with prominent express ion in blood vessels, mRNA for sst(3,4,5) could not be detected by Nor thern blots in any of the tumors. RT-PCR analysis of meningiomas and g liomas revealed the following percent of tumors positive for a given s st mRNA: sst(1) (86%), sst(2) (100%), sst(3) (60%), sst(4) (58%), and sst(5) (67%); 85% of tumors expressed 3 of the 5 subtypes. No correlat ion was found between the pattern of expression of sst mRNA and tumor type, location, and histology for either the meningiomas or gliomas. O ur results show that meningiomas and gliomas are all positive for at l east one sst subtype, the majority expressing multiple subtypes. sst(2 ) is the most abundant isoform with a rich expression in both tumor an d peritumoral tissue especially blood vessels. (C) 1998 Wiley-Liss, In c.