Analysis of insulin-like growth factor I gene expression in malignancy: evidence for a paracrine role in human breast cancer

Mol Endocrinol. 1989 Mar;3(3):509-17. doi: 10.1210/mend-3-3-509.


Insulin-like growth factor I (IGF-I) activity has been reported to be produced by several human cancers. Identification of RNAs transcribed from the IGF-I gene has been complicated by the detection of multiple hybridizing bands on Northern analysis. To determine if any of these RNAs are transcribed from the IGF-I gene, we have used a sensitive and specific ribonuclease (RNAse) protection assay for IGF-I. We have also studied the breast cancer tissue expression of IGF-I using in situ hybridization histochemistry. We have found no IGF-I mRNA in breast (zero of 11) or colon cancer (zero of 9) cell lines; both of these tumors have been previously reported to express IGF-I mRNA. However, three of three neuroepithelioma and one of two Ewing's sarcoma cell lines express IGF-I mRNA; therefore, in these tumors IGF-I may be an autocrine growth factor. In contrast to breast cancer cell lines, RNA extracted from breast tissues has easily detectable IGF-I mRNA. In situ hybridizations show that IGF-I mRNA is expressed in the stromal cells, and not by normal or malignant epithelial cells. These findings suggest that although IGF-I is not produced by breast epithelial cells it may function as either a paracrine stimulator of epithelial cells or an autocrine stimulator of stromal cells.

MeSH terms

  • Blotting, Northern
  • Breast / metabolism
  • Breast Neoplasms / genetics*
  • Hormones, Ectopic / genetics
  • Humans
  • Insulin-Like Growth Factor I / biosynthesis
  • Insulin-Like Growth Factor I / genetics*
  • Platelet-Derived Growth Factor / biosynthesis
  • RNA, Messenger / genetics
  • Somatomedins / genetics*
  • Tumor Cells, Cultured


  • Hormones, Ectopic
  • Platelet-Derived Growth Factor
  • RNA, Messenger
  • Somatomedins
  • Insulin-Like Growth Factor I