Somatostatin and Somatostatin Receptors in Tumour Biology

Abstract

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

Keywords: Somatostatin: somatostatin receptors; signaling; tumours.

Figure 1

Schematic illustration showing multiple factors involved in tumor progression and treatment failure. Figure was created with BioRender.com.

Figure 2

Schematic illustration showing somatostatin receptor-mediated signaling pathways. Figure was created with BioRender.com.

Figure 3

Schematic representation showing direct and indirect effect of somatostatin associated with inhibition of cell proliferation. Figure was created with BioRender.com.

Figure 4

Schematic illustration displaying the process of sprouting angiogenesis and inhibitory role of SST in blood vessels. Figure was created with BioRender.com.

Figure 5

Different types of tumors that metastasize to the brain. Figure was created with BioRender.com.

Figure 6

Schematic illustration depicting possible site of ovarian tumor in body. Figure was created with BioRender.com.