The expression of somatostatin receptors 3, 4 and 5 in laryngeal pathology

Abstract

Conventional chemotherapy has no role to play in the curative treatment of laryngeal carcinoma, yet the mortality rate from advanced disease has improved little over the last 20 years. Somatostatin is a naturally occurring peptide, which exerts anti-proliferative and anti-angiogenic effects via 5 membrane-bound receptor subtypes (SSTRs 1-5). We have previously studied the expression of SSTRs 1 and 2 and demonstrated loss of SSTR2 in laryngeal carcinoma. This study was therefore undertaken to study the expression of the remaining SSTR subtypes in laryngeal pathology. The expression of SSTRs 3, 4 and 5 was studied in benign (Reinke's oedema), pre-malignant and malignant laryngeal specimens using immunohistochemistry. There was very little expression of SSTR3, with low to moderate levels detected in just 1/6 (17%) benign and pre-malignant specimens and 3/12 (25%) malignant laryngeal tumours. A variable degree of SSTR4 expression was detected across the three groups, with low to moderate levels in 3/6 (50%) benign specimens, compared to only 1/6 (17%) pre-malignant specimens but 8/12 (67%) malignant laryngeal tumours. The majority of all specimens, however, demonstrated moderate to high levels of expression of SSTR5. This receptor was detected in 4/6 (67%) benign, all pre-malignant (100%) and 10/12 (83%) malignant cases. All the laryngeal carcinomas studied expressed either SSTR4 or SSTR5, with 60% expressing both, but very few expressing SSTR3. Somatostatin receptors warrant further investigation to determine whether they have a therapeutic role in carcinoma of the larynx.