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Identification of lymphoid cell lines bearing receptors for somatostatin
H Nakamura1, T Koike, K Hiruma
1Second Department of Internal Medicine, Chiba University School of Medicine, Japan.
Abstract:
The MT-2, derived from an adult T-cell leukaemia (ATL) cell, the Molt-4F, a human T-cell line, and the Isk, an EB virus-transformed B-cell line, were found to have high-affinity receptors for somatostatin, a cyclic tetradecapeptide that inhibits the release of substances such as growth hormone, TSH, glucagon, insulin, secretin, gastrin and cholecystokinin. The quantity of radioactivity bound varied linearly with the number of cells, and was displaced by non-radioactive somatostatin in a concentration-dependent manner. Specific binding of 125I-somatostatin was time- and temperature-dependent and at 22 degrees reached equilibrium within 120 min. Scatchard analysis demonstrated one class of specific-binding sites on MT-2 cells, Isk cells and Molt-4F cells that had respective densities and dissociation constants of 109 pM and 0.64 nM, 102 pM and 1.1 nM, and 5.8 pM and 0.22 nM.
Insights
Researchers found high-affinity somatostatin receptors on leukemia and B-cell lines. These receptors, crucial for hormone regulation, showed specific binding characteristics in MT-2, Isk, and Molt-4F cells.
Area of Science:
- Endocrinology
- Cell Biology
- Oncology
Background:
- Somatostatin is a cyclic tetradecapeptide hormone regulating various physiological processes.
- It inhibits the release of growth hormone, TSH, glucagon, insulin, secretin, gastrin, and cholecystokinin.
- The presence and characteristics of somatostatin receptors on specific cancer cell lines are not fully elucidated.
Purpose of the Study:
- To investigate the presence and binding characteristics of somatostatin receptors on human T-cell leukemia (MT-2, Molt-4F) and EBV-transformed B-cell (Isk) lines.
- To quantify receptor density and affinity using radioligand binding assays.
Main Methods:
- Radioligand binding assays using 125I-somatostatin.
- Incubation of cell lines (MT-2, Molt-4F, Isk) with labeled somatostatin.
- Displacement assays with non-radioactive somatostatin.
- Scatchard analysis to determine receptor density and dissociation constants.
Main Results:
- MT-2, Molt-4F, and Isk cells exhibit high-affinity somatostatin receptors.
- Specific binding was concentration-dependent, time-dependent, and temperature-dependent, reaching equilibrium within 120 minutes at 22°C.
- Scatchard analysis revealed a single class of specific binding sites on each cell line with varying densities and dissociation constants.
Conclusions:
- Human T-cell leukemia and B-cell lines possess specific, high-affinity somatostatin receptors.
- These findings suggest potential therapeutic targets for hormone-related conditions or cancers expressing these receptors.