Clinical Significance of Somatostatin Receptor (SSTR) 2 in Meningioma

Abstract

Somatostatin receptor (SSTR) 2, widely expressed in meningioma, is a G-protein-coupled receptor and can be activated by somatostatin or its synthetic analogs. SSTR2 is therefore extensively studied as a marker and target for the diagnosis and treatment of meningioma. Accumulating studies have revealed the crucial clinical significance of SSTR2 in meningioma. Summarizing the progress of these studies is urgently needed as it may not only provide novel and better management for patients with meningioma but also indicate the direction of future research. Pertinent literature is reviewed to summarize the recent collective knowledge and understanding of SSTR2's clinical significance in meningioma in this review. SSTR2 offers novel ideas and approaches in the diagnosis, treatment, and prognostic prediction for meningioma, but more and further studies are required.

Keywords: SSTR2; diagnosis; meningioma; prognosis; somatostatin; somatostatin analogs; treatment.

FIGURE 1

The diagnosis process and application scenarios of meningioma with the utilization of SSTR2.

FIGURE 2

The direct and indirect antitumor mechanisms of the somatostatin analogs in meningioma. Somatostatin analogs exert their direct antitumor effects by binding to SSTR2, which leads to the activation of SHP1 and SHP2. SHP2 can further activate SHP1. SHP1 mediates antiproliferative action through inhibiting the PI3K/Akt pathway and induces cell cycle arrest through down-regulating cyclin D1 while up-regulating p27/Kip 1. Suppressing secretion of VEGF and GH/IGF-1 and activating the immune system are involved in indirect antitumor mechanisms of somatostatin analogs. Abbreviations: Akt, protein kinase B; GH, growth hormone; insulin-like growth factor-1 (IGF-1); PI3K, phosphatidylinositol 3-kinase; SHP1, SH2-containing phosphatase-1; SHP2, SH2-containing phosphatase-2; SSTR, somatostatin receptor; and VEGF, vascular endothelial growth factor.

FIGURE 3

Kaplan–Meier curves of overall survival and progression-free survival of the reported effects (101) of SSTR-related radiation therapy. (A) Overall survival. (B) Progression-free survival.