Imatinib Inhibits GH Secretion From Somatotropinomas

Area of Science:

• Endocrinology
• Oncology
• Molecular Biology

Background:

• Imatinib, a tyrosine kinase inhibitor, is known to cause growth failure in children with chronic myeloid leukemia, likely by affecting the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis.
• Pituitary adenomas, particularly somatotropinomas, are tumors that secrete excess GH.

Purpose of the Study:

• To investigate the expression of imatinib targets in pituitary adenomas.
• To determine the effect of imatinib on GH secretion in somatotropinoma cells and a rat GH3 cell line.

Main Methods:

• Immunohistochemistry and immunoblotting were used to analyze imatinib target expression (c-kit, VEGF, PDGFR-α/β) in 157 pituitary adenomas and normal pituitary tissue.
• Primary cultures of human somatotropinomas and the rat GH3 cell line were treated with imatinib to assess effects on GH secretion, cell viability, and apoptosis.
• Receptor tyrosine kinase arrays were employed to identify signaling pathways affected by imatinib.

Main Results:

• Somatotropinomas exhibited significantly higher expression of c-kit and platelet-derived growth factor receptor-β (PDGFR-β) compared to normal pituitary tissue.
• Imatinib treatment led to significant inhibition of GH secretion in both human somatotropinoma cultures and the GH3 cell line, without impacting cell viability or apoptosis.
• Receptor tyrosine kinase array analysis indicated that imatinib inhibits GH signaling through the PDGFR-β pathway.

Conclusions:

• Imatinib effectively inhibits GH secretion in somatotropinoma cells, independent of cell viability and apoptosis.
• These findings suggest that imatinib could serve as a valuable adjunctive therapy for managing GH-secreting pituitary adenomas.