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Mol Path 2001;54:121-124 doi:10.1136/mp.54.3.121

The IGF system in thyroid cancer: new concepts

  1. V Vella1,
  2. L Sciacca1,
  3. G Pandini2,
  4. R Mineo1,
  5. S Squatrito1,
  6. R Vigneri2,
  7. A Belfiore3
  1. 1Cattedra di Endocrinologia, Istituto di Medicina Interna, Malattie Endocrine e del Metabolismo, University of Catania, Ospedale Garibaldi, Catania, Italy
  2. 2IMO, Istituto Mediterraneo di Oncologia, Catania, Italy
  3. 3Cattedra di Endocrinologia e Malattie del Metabolismo, Dipartimento di Medicina Sperimentale eClinica, University of Catanzaro “Magna Graecia”, Policlinico Mater Domini,Catanzaro, Italy
  1. Dr Belfiore belfiore{at}unicz.it
  • Accepted 16 January 2001

Abstract

In recent years, the activation of the insulin-like growth factor (IGF) system in cancer has emerged as a key factor for tumour progression and resistance to apoptosis. Therefore, a variety of strategies have been developed to block the type I IGF receptor (IGF-I-R), which is thought to mediate the biological effects of both IGF-I and IGF-II. However, recent data suggest that the IGF signalling system is complex and that other receptors are involved. To unravel the complexity of the IGF system in thyroid cancer, IGF-I and IGF-II production, and the expression and function of their cognate receptors were studied. Both IGFs were found to be locally produced in thyroid cancer: IGF-I by stromal cells and IGF-II by malignant thyrocytes. Values were significantly higher in malignant tissue than in normal tissue. IGF-I-Rs were overexpressed in differentiated papillary carcinomas but not in poorly differentiated or undifferentiated tumours, whereas insulin receptors (IRs) were greatly overexpressed in all tumour hystotypes, with a trend for higher values in dedifferentiated tumours. As a consequence of IR overexpression, high amounts of IR/IGF-I-R hybrids (which bind IGF-I with high affinity) were present in all thyroid cancer histotypes. Because of recent evidence that isoform A of IR (IR-A) is a physiological receptor for IGF-II in fetal life, the relative abundance of IR-A in thyroid cancer was measured. Preliminary data indicate that overexpressed IRs mainly occur as IR-A in thyroid cancer. These data indicate that both IR/IGF-I-R hybrids and IR-A play an important role in the overactivation of the IGF system in thyroid cancer and in IGF-I mitogenic signalling in these tumours. J Clin Pathol: Mol Pathol

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