Somatostatin receptors and their subtypes in human tumors and in peritumoral vessels

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Published on Monday, 15 April 2019

Abstract

Somatostatin receptors are expressed by a large variety of human tumors. In vitro receptor autoradiographic studies have shown that these tumors can express more than one somatostatin receptor subtype. Whereas the majority of tumors bind octreotide with high affinity, some, i.e., prostate tumors, bind octreotide with low affinity only.

The discovery of five somatostatin receptor subtypes, sst1-5, by gene cloning has increased our understanding of somatostatin receptor structure and function.

Using in situ hybridization techniques, we found that various human tumors, identified as somatostatin receptor-positive in binding studies, expressed sst2 mRNA in the majority of cases, whereas sst1 and sst3 were less frequent. Often, all three sst were expressed simultaneously.

In another recent in situ hybridization study, primary prostate cancers were shown to preferentially express sst1, rather than sst2 or sst3. Moreover, a high incidence of sst5 was found in growth hormone (GH)-producing pituitary adenomas and, to a lesser extent, in active pituitary adenomas; gastroenteropancreatic (GEP) tumors showed all possible combinations, but with a predominance of sst2.

Overall, the presence of sst2 mRNA and/or sst5 generally correlated with the presence of octreotide-binding sites, but with exceptions.

These results indicate the highly variable abundance of sst mRNAs in individual somatostatin receptor-containing tumors.

Somatostatin receptors were not only found in tumoural tissue, but also in the peritumoral vascular system.

This was particularly well studied in colorectal carcinomas, where the peritumoral veins were shown to express in all cases a high density of somatostatin receptors, probably of the sst2 type, binding octreotide with high affinity. Therefore, the host peritumoral vascular system may be a possible target of somatostatin action in tumor development.

Somatostatin may act locally on tumor growth through two different mechanisms dependent on local somatostatin receptor expression: through direct action on tumor cells or through action on peritumoral vessels, which may alter the hemodynamics of the tumoral blood circulation.

 

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See also:

- Official Web Site: The Di Bella Method;

- Somatostatin in oncology, the overlooked evidences - In vitro, review and in vivo publications;

- The Di Bella Method (A Fixed Part - Somatostatin, Octreotide, Sandostatin LAR, analogues and/or derivatives);

- The Synergism of Somatostatin, Melatonin, Vitamins Prolactin and Estrogen Inhibitors Increased Survival, Objective Response and Performance Status In 297 Cases of Breast Cancer;

- Complete objective response, stable for 5 years, with the Di Bella Method, of multiple-metastatic carcinoma of the breast;

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonin, retinoids, vitamin D3, and low doses of cyclophosphamide in 20 cases of breast cancer: a preliminary report;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 122 cases of breast cancer;

- Complete objective response to biological therapy of plurifocal breast carcinoma;

- Recurrent Glioblastoma Multiforme (grade IV – WHO 2007): a case of complete objective response achieved by means of the concomitant administration of Somatostatin and Octreotide – Retinoids – Vitamin E – Vitamin D3 – Vitamin C – Melatonin – D2 R agonists (Di Bella Method – DBM) associated with Temozolomide;

- The Di Bella Method DBM improved survival objective response and performance status in a retrospective observational clinical study on 23 tumours of the head and neck;

- Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in advanced non-small-cell lung cancer patients with low performance status;

- Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in chemotherapy-pretreated patients with advanced lung adenocarcinoma and low performance status;

- Observations on the Report of a case of pulmonary adenocarcinoma with lymph node, hepatic and osseus metastasis;

- Neuroblastoma: Complete objective response to biological treatment;

- Cyclophosphamide plus Somatostatin, Bromocriptin, Retinoids, Melatonin and ACTH in the Treatment of Low-grade Non-Hodgkin’s Lymphomas at Advanced Stage: Results of a Phase II Trial;

- Relapse of High-Grade Non-Hodgkin’s Lymphoma After Autologous Stem Cell Transplantation: A Case Successfully Treated With Cyclophosphamide Plus Somatostatin, Bromocriptine, Melatonin, Retinoids, and ACTH;

- Low-grade Non-Hodgkin Lymphoma at Advanced Stage: A Case Successfully Treated With Cyclophosphamide Plus Somatostatin, Bromocriptine, Retinoids, and Melatonin;

- The Di Bella Method (DBM) improved survival, objective response and performance status in a retrospective observational clinical study on 55 cases of Lymphomas;

- Large B-cells Non-Hodgkin's Lymphoma, Stage IV-AE: a Case Report;

- Non-Hodgkin's Lymphoma, Stage III-B-E: a Case Report;

- Oesophageal squamocellular carcinoma: a complete and objective response;

- Pancreatic Adenocarcinoma: clinical records on 17 patients treated with Di Bella's Method;

- The Di Bella Method Increases by the 30% the survival rate for Pancreas tumors and for this reason should be proposed as first line therapy for this type of cancer;

- The Di Bella Method (DBM) in the treatment of prostate cancer: a preliminary retrospective study of 16 patients and a review of the literature.