Growth factors and carcinoid tumours

Area of Science:

• Endocrinology
• Oncology
• Molecular Biology

Background:

• Carcinoid tumors are neuroendocrine neoplasms.
• The role of growth factors in carcinoid tumor development is not fully understood.

Purpose of the Study:

• To investigate the presence and role of growth factors and their receptors in human midgut carcinoids and Mastomys gastric carcinoids.
• To explore the potential autocrine and paracrine mechanisms driving carcinoid tumor growth and associated neuronotrophic effects.

Main Methods:

• Immunocytochemistry and radioimmunoassay were used to detect insulin-like growth factor-I (IGF-I) in human midgut carcinoids.
• Northern analysis and immunocytochemistry were employed to assess transforming growth factor-alpha (TGF-alpha) and epidermal growth factor (EGF) receptors.
• Co-culture systems were utilized to evaluate neuronotrophic factor secretion by carcinoid tumor cells.
• Gastric carcinoid development in Mastomys was studied under conditions of hypergastrinemia induced by histamine2-receptor blockade.

Main Results:

• Human midgut carcinoid tumors express and produce IGF-I, with detectable IGF-I receptors enhancing DNA synthesis in cultured cells, suggesting autocrine stimulation.
• Expression of TGF-alpha and EGF receptors was observed in midgut carcinoids, indicating TGF-alpha's potential role in autocrine modulation.
• Carcinoid tumor cells secreted a potent neuronotrophic factor, potentially mediated by IGF-I and TGF-alpha, or an unidentified factor.
• Gastric carcinoids in Mastomys exhibited rapid development during hypergastrinemia, implying gastrin as a critical growth factor.

Conclusions:

• IGF-I and TGF-alpha may act as autocrine growth stimulators for human midgut carcinoids.
• Carcinoid tumors can secrete factors that support neuronal growth, with IGF-I and TGF-alpha being potential contributors.
• Gastrin is essential for the rapid growth of gastric carcinoids in the Mastomys model.