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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Int-2, an autocrine and/or ultra-short-range effector in transgenic mammary tissue transplants.

BACKGROUND: Previous studies have shown associations between overexpression of int-2 messenger RNA (mRNA) and murine mammary tumors and between amplification of the int-2 genomic locus and human breast cancers. The Int-2 protein (fibroblast growth factor 3) is a member of the heparin-binding growth factor family of proteins. The export of these growth factors from cells may depend on the presence of amino terminal sequences containing hydrophobic signal peptides. Although Int-2 has a putative signal sequence, it is not known whether or how this protein is secreted from cells. PURPOSE: Assuming that the Int-2 protein is secreted from mammary epithelial cells in a basolateral direction so that it is available to affect adjacent cells, we investigated whether it acts in a paracrine manner, exerting its effect externally on adjacent cells, or in an autocrine manner, exerting its effect internally within the same cell. METHODS: Using in situ hybridization with 35S-labeled RNA antisense probes that specifically detect mRNA coding for the Int-2 protein, we determined the cell-specific localization of int-2 mRNA expression in the mammary gland of transgenic FVB/N mice overexpressing int-2 mRNA. Then we transplanted pieces of mammary epithelial tissue expressing int-2 mRNA into the mammary fat-pad of wild-type, syngeneic animals. The mammary glands of host animals were examined as whole-mounts and as histologic sections 2-6 months after transplantation. In situ hybridization was used to confirm which cells continued to express int-2 mRNA following transplantation. RESULTS: Int-2 mRNA expression in transgenic mice was localized to the mammary epithelial cells. Transplants expressing int-2 mRNA were similar to wild-type transplants in that they had no observable effect on either the growth or the morphology of host mammary epithelium. Abnormal growth occurred only in transplanted tissue expressing int-2 mRNA but not in adjacent host mammary epithelium. CONCLUSION: Given the limitations of our experimental system and the limited information available to date on the secretion of Int-2 protein, these results suggest that, although the Int-2 protein contains a putative signal peptide, it may act primarily as an autocrine or as an ultra-short-range paracrine growth factor in mammary epithelium.[1]

References

  1. Int-2, an autocrine and/or ultra-short-range effector in transgenic mammary tissue transplants. Ornitz, D.M., Cardiff, R.D., Kuo, A., Leder, P. J. Natl. Cancer Inst. (1992) [Pubmed]
 
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