Distribution and functional significance of somatostatin receptors in malignant melanoma

Malignant melanoma is a neuroendocrine tumor that contains somatostatin rec eptors (SSTRs), Adjuvant therapy for melanoma is limited. Because melanomas arise from neural crest cells, we sought to evaluate the distribution of S STR subtypes found in these tumors and their functional significance by ima ging with In-111-pentetreotide scintigraph (OctreoScan). Octreotide binds w ith greatest affinity to SSTR? and SSTR5. Studying the expression of SSTRs in melanoma may demonstrate a potential role for octreotide in the treatmen t of melanoma, A series of 23 melanomas from 17 patients who underwent rese ction of regional or distant metastases were evaluated for the presence of SSTRs by the reverse transcriptase-polymerase chain reaction (RT-PCR) using primers specific for SSTR1 through SSTR5, Identity of RT-PCR products was confirmed by Southern blot analysis, Sixteen patients underwent preoperativ e OctreoScan, SSTR1 aas expressed in 96% of tumors, SSTR2 in 83%, SSTR3 in 61%, SSTR4 in 57%, and SSTR5 in 9%. OctreoScan imaged 63% of tumors, There was no correlation between SSTR subtype expression and OctreoScan result. M ost of the melanomas expressed mRNA for SSTR1 and SSTR2, with approximately half expressing SSTR3 and SSTR4. The SSTR mRNA for SSTR2 appears to be tra nscribed into functional protein that binds In-111-pentetreotide in more th an half of these patients. Although OctreoScan has limited sensitivity for localizing melanomas, tumors that can be imaged by OctreoScan mar be amenab le to adjuvant therapy with octreotide or targeted therapy with high-energy radioisotope-labeled octreotide, These studies clearly define melanoma as a neuroendocrine turner, which may open new avenues for tumor control.