Somatostatin and vasoactive intestinal peptide receptors in human mesenchymal tumors: in vitro identification

Somatostatin and vasoactive intestinal peptide (VIP) have been shown to be of diagnostic and therapeutic interest in several types of human epithelial tumors expressing the respective receptor. The present study evaluates the presence of somatostatin and VIP receptors in 64 primary or metastatic human mesenchymal tumors. In vitro receptor autoradiography on cryostat sections was performed using 125I-labeled [Tyr3]-octreotide as well as 125I-labeled [Leu8,D-Trp22,Try25]-somatostatin-28 as radioligands for somatostatin receptors and 125I-labeled VIP as radioligand for VIP receptors. Somatostatin receptors were identified in bone and vascular/perivascular tumors (3 of 3 osteosarcomas, 1 of 1 giant cell tumor, 2 of 2 angiosarcomas, and 4 of 4 hemangiopericytomas), in 2 of 2 synovial sarcomas, in 2 of 5 histiocytomas, and in several muscle cell tumors (1 of 2 leiomyomas, 2 of 4 leiomyosarcomas, and 3 of 5 rhabdomyosarcomas) but were absent in 4 liposarcomas, 3 mesotheliomas, 3 chondrosarcomas, 10 Ewing sarcomas, 11 schwannomas, and 5 Wilms' tumors. VIP receptors were identified in 3 of 3 differentiated liposarcomas, 2 of 2 angiosarcomas, 4 of 4 hemangiopericytomas, 2 of 2 synovial sarcomas, 3 of 3 mesotheliomas, 5 of 5 Wilms tumors, as well as in 2 of 5 histiocytomas, 1 of 2 leiomyomas, 2 of 4 leiomyosarcomas, 3 of 3 intermediately differentiated rhabdomyosarcomas, and 1 of 3 osteosarcomas but not in chondrosarcomas, Ewing sarcomas, schwannomas, or undifferentiated rhabdomyosarcomas. The receptors were located on neoplastic cells. The somatostatin receptors were of high affinity and of high specificity for biologically active somatostatin analogues with high affinity for somatostatin-14 and somatostatin-28 as well as for octreotide, thus representing the sst2 subtype; in a few cases of tumors having somatostatin receptors with low affinity for octreotide, in situ hybridization techniques identified preferentially sst1 mRNA. These data suggest that human mesenchymal tumors may be targets for somatostatin and/or VIP receptor in vivo imaging; they may also be potential targets for somatostatin or VIP analogue therapy.