Detection of somatostatin receptor subtype 2 (SSTR2) in established tumors and tumor cell lines: evidence for SSTR2 heterogeneity

Abstract

The somatostatin receptor subtype 2 (SSTR2) was detected in a wide range of human and rat tumors using in vitro receptor binding ([125I]MK-678), receptor gene expression analysis, and immunoblotting techniques.

The highest receptor concentrations were observed in the rat AR42J pancreatic and human small cell lung cancer (SCLC) cell lines, NCI-H69 and NCI-H345, with much lower levels detected in breast, prostate, melanoma, and hepatic tumors.

Several human pancreas tumors were devoid of SSTR2.

For all tumors showing detectable [125I]MK-678 binding, SSTR2 receptor mRNA was expressed.

Furthermore, a mRNA transcript corresponding to a truncated isoform of SSTR2 was detected at low levels in the human SCLC NCI-H69 cell line, and likely represents a human homologue of rodent SSTR2B.

Immunoblotting analysis using the SSTR2-specific antibody, 2e3, detected multiple immunoreactive protein species, including a predominant 150-kDa molecule, which could be blocked by the SSTR2-derived 2e3 peptide.

Somatostatin (SRIF) peptides with high SSTR2 affinity and antiproliferative properties were potent inhibitors of [125I]MK-678 binding to several tumor types, suggesting that they may exert antitumor effects via the SSTR2 receptor.

 

 

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See also:

- Somatostatin in oncology, the overlooked evidences;

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- 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;

- Oesophageal squamocellular carcinoma: a complete and objective response;

- 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;

- Evaluation of the safety and efficacy of the first-line treatment with somatostatin combined with melatonisn, 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.