Retinoblastoma cells lack receptors.
Researchers seeking to uncover the biochemical defect behind retinoblastoma, a hereditary cancer of the eye, have found that retinoblastoma tumor cells lack a class of chemical receptors involved in inhibiting growth. The exact function of the so-called transforming growth factor-beta 1 (TGF-beta 1) receptors, first characterized in 1985, is still not well understood. Scientists suspect, howevcer, that the receptors--located on the surface of some cells--are important in regulating cell proliferation. In some cases they appear to protect against the effects of cancer-causing genes, or oncogenes.
As reporte in the April 8 SCIENCE, researchers at the Weizmann Institute of Science in Rehovot, Israel, The White-head Institute for Biomedical Research in Cambridge, Mass., and the University of Massachusetts Medical School in Worcester tested the responses of retinoblastoma tumor cells and normal retinal cells to various growth-inhibiting factors. When the tumor cells proved insensitive to the growth inhibitor TGF-beta 1, they tested the cells for TGF-beta 1 receptors. None was found.
"Loss of TGF-beta 1 receptors, which is a rare event even among tumor cells, may represent one mechansm through which these cells escape from negative control and form retinoblastoma," the researchers report.
Scientists discovered years ago that retinoblastoma involves the failure of a particular gene, the RB gene, to function properly. Little is known about the protein normally coded for by the RB gene, although it is blieved to act directly on DNA. It is possible, the new report concludes, that the RB protein might directly affect the expression of TGF-beta 1 receptors. Alternatively, it might interact with the receptors in a way that affects receptor structure and function, allowing cell proliferation and tumor formation.
"Righ now we can't really draw a link," says Sela Cheifetz, a Whitehead Institute researcher and coauthor of the report. "The apparent lack of TGF-beta receptors may not be the direct cause of the these cells being tumorogenic, but rather might be a consequence." More research needs to be done, she says, to find out exactly what the RB gene product is and its role in cell growth.
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|Title Annotation:||transforming growth factor-beta 1 receptors|
|Date:||Apr 23, 1988|
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