Expressions of Somatostatin Receptor Subtypes (SSTR-1, 2, 3, 4 and 5) in Neuroblastic Tumors; Special Reference to Clinicopathological Correlations with International Neuroblastoma Pathology Classification and Outcomes

Somatostatin receptor (SSTR) expressions in neuroblastomas (NBs) have been confirmed employing various methods. High SSTR-2 expression was suggested to be a favorable prognostic marker, though little is known about the relationships between the expressions of SSTR subtypes, other than SSTR-2, and prognosis. We investigated the expressions of all five known SSTR subtypes in 63 neuroblastic tumors (NTs), employing immunohistochemistry, and also conducted quantitative real-time RT-PCR in 37 of these tumors. We evaluated correlations between the expressions of SSTR subtypes and prognosis, based on the International Neuroblastoma Pathology Classification and patient outcomes. More than 90% of cases expressed, at a minimum, SSTR-1 and/or 2. Ganglioneuromas and ganglioneuroblastomas expressed more than two SSTR subtypes. Among NBs, the favorable histology group showed higher SSTR subtype expressions than the unfavorable histology group. The same tendency was observed when surviving and deceased cases were compared, though SSTR-2 expression was well preserved in some of the deceased cases. In conclusion, NTs highly expressed SSTR-1 and/or 2, and expressions of SSTR generally indicate a good prognosis. However, even those in the unfavorable histology group with NBs expressing SSTR are good candidates for molecular targeting therapy using somatostatin analogues.