Absence of somatostatin receptor expression in vivo is correlated to di- or tetraploid 1p36-deleted neuroblastomas

Differentiated expression of somatostatin receptor subtypes in experimental models and clinical neuroblastoma

BACKGROUND

Neuroblastoma (NB) is a solid tumor of childhood originating from the adrenal medulla or sympathetic nervous system. Somatostatin (SS) is an important regulator of neural and neuroendocrine function, its actions being mediated through five specific membrane receptors. The aim of this study was to investigate the expression of the different somatostatin receptors (SSTRs) in NB tumor cells that may form targets for future therapeutic development.

PROCEDURE

Tumor specimens from 11 children with stage II-IV disease were collected before and/or after chemotherapy. Experimental tumors derived from five human NB cell lines were grown subcutaneously in nude mice. Expression of SSRTs, the neuroendocrine marker chromogranin A (CgA) and SS was detected by immunohistochemistry using specific antibodies.

RESULTS

SSTR2 was detected in 90%, SSTR5 in 79%, SSTR1 in 74%, SSTR3 in 68% whereas SSTR4 was expressed in 21% of the clinical tumors. The experimental tumors expressed SSTRs in a high but variable frequency. All clinical tumors showed immunoreactivity for CgA but not for SS.

CONCLUSION

The frequent expression of SSTRs indicates that treatment with unlabeled or radiolabeled SS analogs should be further explored in NB.

Indium-111–Pentetreotide Scintigraphy and Somatostatin Receptor Subtype 2 Expression: New Prognostic Factors for Malignant Well-Differentiated Endocrine Tumors

Purpose

Well-differentiated metastatic endocrine carcinomas are difficult to manage because of variable disease outcome. New prognostic factors are required. These tumors overexpress somatostatin receptors (sst), implying the use of somatostatin analogs for tumor localization by somatostatin receptor scintigraphy using indium-111–pentetreotide (111In-pentetreotide) and for medical treatment. The aim of the present study was to evaluate the correlation between 111In-pentetreotide scintigraphy, sst receptor expression, and prognosis.

Patients and Methods

Between 1994 and 2002, 48 consecutive patients with well-differentiated endocrine carcinomas and a negative 111In-pentetreotide scintigraphy were retrospectively paired according to sex, age, and tumor localization with 50 patients with well-differentiated endocrine carcinomas and a positive tracer uptake at 111In-pentetreotide scintigraphy. Overall survival and expression of sst1 to sst5 receptors by immunohistochemistry were assessed.

Results

The lack of tracer uptake at the 111In-pentetreotide scintigraphy seemed to be a poor prognostic factor (P = .007) for overall survival by Kaplan-Meier test and in multivariate analysis; age and absence of clinical secretory syndrome also seemed to be poor prognostic factors. The tracer uptake (positive 111In-pentetreotide scintigraphy) correlated with the tumor expression of somatostatin receptor sst2 (P < .001) but not with that of sst1, sst3, sst4, or sst5. In a bivariate analysis, lack of sst2 expression also significantly correlated with poor prognosis.

Conclusion

We demonstrate the prognostic value of 111In-pentetreotide scintigraphy in well-differentiated malignant endocrine tumors. In these tumors, sst2 somatostatin receptor expression correlates with both tracer uptake and a better prognosis.

Galanin and galanin receptors in human cancers

The increasing interest in peptides and peptide receptors in cancer is based on the possibility of receptor targeting, because peptide receptors are often expressed in different human tumors. The neuropeptide galanin has also been suggested to be involved in the development of neuroendocrine tumors based on the development of estrogen-induced tumors in estrogen-sensitive rats. This study summarizes our current knowledge on the expression of galanin peptide and galanin receptors in different human neuroendocrine tumors. The expression of both, peptide and corresponding receptor, seems to be a common feature of human gliomas, pheochromocytomas, pituitary and neuroblastic tumors. The co-expression of galanin and its receptors supports a role for galanin in tumor cell pathology via autocrine/paracrine mechanisms.

Role of gastrointestinal hormones in the proliferation of normal and neoplastic tissues

Gastrointestinal (GI) hormones are chemical messengers that regulate the physiological functions of the intestine and pancreas, including secretion, motility, absorption, and digestion. In addition to these well-defined physiological effects, GI hormones can stimulate proliferation of the nonneoplastic intestinal mucosa and pancreas. Furthermore, in an analogous fashion to breast and prostate cancer, certain GI cancers possess receptors for GI hormones; growth can be altered by administration of these hormones or by blocking their respective receptors. The GI hormones that affect proliferation, either stimulatory or inhibitory, include gastrin, cholecystokinin, gastrin-releasing peptide, neurotensin, peptide YY, glucagon-like peptide-2, and somatostatin. The effects of these peptides on normal and neoplastic GI tissues will be described. Also, future perspectives and potential therapeutic implications will be discussed.