Insulin-like growth factors I and II are autocrine factors in stimulating proteoglycan synthesis, a marker of differentiated chondrocytes, acting through their respective receptors on a clonal human chondrosarcoma-derived chondrocyte cell line, HCS-2/8

Endocrinology. 1997 Oct;138(10):4390-400. doi: 10.1210/endo.138.10.5265.


Both insulin-like growth factor (IGF)-I and IGF-II increased the synthesis of cartilage-type, large proteoglycan in a human chondrosarcoma-derived chondrocyte cell line, HCS-2/8. In contrast to the stimulatory effects of IGFs on costal chondrocytes of the young rabbit, the stimulatory effect of IGF-II on proteoglycan synthesis in HCS-2/8 cells was more potent than that of IGF-I. IGF-II, but not IGF-I, increased calcium influx into HCS-2/8 cells, and there was a close relation between the stimulation of proteoglycan synthesis and the calcium influx. [125I]IGF-I bound to HCS-2/8 cells, and this binding was competitively inhibited by low concentrations of unlabeled IGF-I, higher concentrations of IGF-II, and much higher concentrations of insulin. [125I]IGF-II also bound to the cells, and its binding was competitively inhibited by IGF-II and slightly inhibited by higher concentrations of IGF-I and much higher concentrations of insulin. When radioligand-receptor complexes were separated by SDS-PAGE and subjected to autoradiography, two major bands at 260 and 130 kDa were observed, which correspond to the IGF type II receptor (IGF-IIR) and the alpha subunit of the IGF type I receptor (IGF-IR), indicating the presence of both receptors. When confluent cultures of HCS-2/8 cells were maintained in serum-free medium, proteoglycan synthesis did not decrease unless the medium was repeatedly replaced. Conditioned medium of HCS-2/8 cells stimulated the HCS-2/8 cells to synthesize proteoglycans. RIA revealed that the cells produced both IGF-II and IGF-I. Transcripts of messenger RNAs of both IGF-I and IGF-II and both IGF-IR and IGF-IIR also were detectable by Northern analysis. Both anti-IGF-IR antibody and anti-IGF-II antibody inhibited proteoglycan synthesis. Mannose-6-phosphate, which is known to bind to IGF-IIR, stimulated proteoglycan synthesis, potentiated IGF-II-stimulated proteoglycan synthesis, and enhanced the binding affinity for IGF-II but not for IGF-I. Even in the presence of anti-IGF-IR antibody, IGF-II and mannose-6-phosphate stimulated proteoglycan synthesis in the cells. [Leu27]IGF-II, an IGF-II analogue with high affinity only for IGF-IIR, strongly stimulated proteoglycan synthesis in HCS-2/8 cells but [Arg54, Arg55]IGF-II, which binds to only IGF-IR, also stimulated proteoglycan synthesis in the cells. These findings indicate that IGF-I and IGF-II act as autocrine differentiation factors for this chondrocytic permanent cell line, HCS-2/8, mainly via respective receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Antibodies / pharmacology
  • Blotting, Northern
  • Bone Neoplasms / chemistry
  • Bone Neoplasms / metabolism*
  • Bone Neoplasms / pathology
  • Calcium / metabolism
  • Cartilage / chemistry
  • Cartilage / cytology
  • Cartilage / metabolism
  • Cell Differentiation
  • Cells, Cultured
  • Chondrosarcoma / chemistry
  • Chondrosarcoma / metabolism*
  • Chondrosarcoma / pathology
  • Culture Media, Conditioned / pharmacology
  • Electrophoresis, Polyacrylamide Gel
  • Gene Expression Regulation
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Insulin-Like Growth Factor I / metabolism
  • Insulin-Like Growth Factor I / pharmacology
  • Insulin-Like Growth Factor I / physiology*
  • Insulin-Like Growth Factor II / metabolism
  • Insulin-Like Growth Factor II / pharmacology
  • Insulin-Like Growth Factor II / physiology*
  • Iodine Radioisotopes
  • Male
  • Mannosephosphates / pharmacology
  • Protein Binding
  • Proteoglycans / biosynthesis*
  • RNA, Messenger / analysis
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rabbits
  • Receptor, IGF Type 1 / analysis
  • Receptor, IGF Type 1 / genetics
  • Receptor, IGF Type 1 / physiology*
  • Receptor, IGF Type 2 / analysis
  • Receptor, IGF Type 2 / genetics
  • Receptor, IGF Type 2 / physiology*
  • Tumor Cells, Cultured


  • Antibodies
  • Culture Media, Conditioned
  • Iodine Radioisotopes
  • Mannosephosphates
  • Proteoglycans
  • RNA, Messenger
  • Receptor, IGF Type 2
  • mannose-6-phosphate
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II
  • Receptor, IGF Type 1
  • Calcium