1. The Effects of Retinoic Acid on the Insulin-like Growth Factor Axis in Primary Tissue Culture from Hyperparathyroidism
- Author
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Jeffrey M P Holly, Malcolm H. Wheeler, J. R. Farndon, Teresa Lai, C. Wong, and Claire E. Stewart
- Subjects
Adult ,medicine.medical_specialty ,medicine.medical_treatment ,Retinoic acid ,Tretinoin ,Retinoic acid receptor beta ,Receptor, IGF Type 2 ,Insulin-like growth factor-binding protein ,Insulin-like growth factor ,chemistry.chemical_compound ,Insulin-Like Growth Factor II ,Somatomedins ,Internal medicine ,Humans ,Medicine ,Insulin-Like Growth Factor I ,Vitamin A ,Receptor ,Cells, Cultured ,Aged ,Aged, 80 and over ,biology ,business.industry ,Hyperparathyroidism ,Middle Aged ,Insulin-Like Growth Factor Binding Proteins ,Retinoic acid receptor ,Endocrinology ,chemistry ,Cell culture ,biology.protein ,Female ,Surgery ,business ,medicine.drug - Abstract
Background The importance of the IGF system in HPT has been previously demonstrated. Additionally, the role of vitamin A in HPT has been reported. Retinoic acid (RA), a derivative of vitamin A, is a ligand for the IGF II receptor (IGF2R). We have evaluated the interactions of RA with the IGF system in a primary parathyroid cell culture model. Materials and Methods Primary cell cultures were prepared from nine patients. Following adhesion, the cells were transferred to serum-free medium and dosed once with growth factors ± RA for 96 hours. Proliferation was assessed by measuring tritiated thymidine incorporation. Results Compared with the control group (100%), both IGF I and II increased DNA synthesis significantly. Retinoic acid significantly reduced the basal DNA synthesis to 82.2% ± 4.2% compared with control (P < 0.05). Retinoic acid ×10−5 M completely abrogated the proliferative actions of IGF II (70.2% ± 9.7%, P < 0.05) but had no significant effect on the IGF I response (P > 0.05). To evaluate the role of IGF2R or IGFBPs in mediating the actions of RA, the IGF II analogs [Leu27]IGF II (10–20-fold reduced IGF I receptor affinity) and des(1–6) IGF II (lower IGFBP binding affinity) were used. The IGF II inhibitory effect of RA was enhanced in the presence of analogs [Leu27]IGF II (P = 0.052) but not with des(1–6)IGF II (P > 0.05), compared with wild-type IGF II. Conclusions These data implicate a novel antiproliferative role for RA in enhancing the pericellular clearance of IGF II via the IGF2R preventing ligand activation of the IGF I receptor. This may have broader implications for RA effects in other tumors.
- Published
- 2006
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