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Somatostatin receptors and somatostatin content in medullary thyroid carcinomas
J C Reubi1, J A Chayvialle, B Franc
1Sandoz Research Institute Berne, Switzerland.
Abstract:
Human medullary thyroid carcinomas from 19 patients were analyzed for their content in somatostatin (SRIF) receptors using receptor autoradiography with a SRIF-28 analogue and the SRIF octapeptide [Tyr3]-SMS 201-995 as iodinated radioligands. Four out of 19 cases were SRIF receptor positive with the SRIF octapeptide radioligand. These cases as well as four additional tumors were also positive with the SRIF-28 radioligand 125I-[Leu8, D-Trp22, Tyr25]-SRIF-28. High affinity binding sites pharmacologically specific for bioactive SRIF analogues, specifically located on tumor tissue, were identified. In some cases the SRIF receptors were distributed in a non-homogeneous pattern, with labelling occurring preferentially in highly differentiated tumor regions. Numerous cases were shown to have a high tumoral SRIF content measured by radioimmunoassay or immunohistochemical technique. However, there was no correlation between SRIF receptor status and tumor levels of endogenous SRIF. No correlation was seen between the clinical outcome or the survival of the patients and their tumoral SRIF receptor content. Whereas some medullary thyroid carcinomas seem to be a target for SRIF, the SRIF function in these tumors remains unclear. SRIF receptors in a group of medullary thyroid carcinomas may be useful morphological marker of these tumors and of potential interest for their in vivo localization.
Insights
Medullary thyroid carcinomas were analyzed for somatostatin (SRIF) receptors. Some tumors showed SRIF receptors, potentially useful for in vivo localization, but their function remains unclear.
Area of Science:
- Endocrinology
- Oncology
- Molecular Biology
Background:
- Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor.
- Somatostatin (SRIF) is a peptide hormone with various physiological roles.
- SRIF receptors are implicated in the regulation of cell growth and function.
Purpose of the Study:
- To investigate the presence and characteristics of somatostatin receptors in human medullary thyroid carcinomas.
- To explore the potential correlation between SRIF receptor status, endogenous SRIF levels, and clinical outcomes.
- To assess the utility of SRIF receptors as a potential marker for MTC.
Main Methods:
- Receptor autoradiography using iodinated SRIF analogues (SRIF-28 and octapeptide [Tyr3]-SMS 201-995).
- Radioimmunoassay and immunohistochemistry for measuring tumoral SRIF content.
- Analysis of patient data for clinical outcome and survival.
Main Results:
- SRIF receptors were detected in 4 out of 19 MTC cases using the octapeptide radioligand and in 8 cases using the SRIF-28 radioligand.
- High-affinity, pharmacologically specific SRIF binding sites were identified on tumor tissue.
- SRIF receptor distribution was non-homogeneous in some tumors, correlating with differentiated regions.
- No correlation was found between SRIF receptor status and endogenous SRIF levels, clinical outcome, or patient survival.
Conclusions:
- Some medullary thyroid carcinomas express somatostatin receptors, suggesting they may be a target for SRIF.
- The precise function of SRIF in MTC remains undetermined.
- SRIF receptors could serve as a morphological marker for MTC and potentially aid in in vivo tumor localization.