S-Gal, a novel 1H MRI reporter for beta-galactosidase

Magn Reson Med. 2010 Jul;64(1):65-71. doi: 10.1002/mrm.22400.


Reporter genes and associated enzyme activity are becoming increasingly significant for research in vivo. The lacZ gene and beta-galactosidase (beta-gal) expression have long been exploited as reporters of biologic manipulation at the molecular level, and a noninvasive detection strategy based on proton MRI is particularly attractive. 3,4-Cyclohexenoesculetin beta-D-galactopyranoside (S-Gal) is a commercial histologic stain, which forms a black precipitate in the presence of beta-gal and ferric ions, suggesting potential detectability by MRI. Generation of the precipitate is now shown to cause strong T(2)* relaxation, revealing beta-gal activity. A series of tests with the enzyme in vitro and with tumor cells shows that this approach can be used as an assay for beta-gal activity. Proof of principle is shown in human breast tumor xenografts in mice. Upon direct injection of a mixture of 3,4-cyclohexenoesculetin beta-D-galactopyranoside and ferric ammonium citrate, intense contrast was observed immediately in MCF7-lacZ tumors, but not in wild-type tumors. 3,4-Cyclohexenoesculetin beta-D-galactopyranoside activation in combination with ferric ions introduces a novel approach for assaying enzyme activity by MRI in vivo.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Blotting, Western
  • Breast Neoplasms / diagnosis*
  • Breast Neoplasms / diagnostic imaging
  • Cell Line, Tumor
  • Contrast Media* / chemistry
  • Female
  • Galactosides / chemistry*
  • Genes, Reporter*
  • Humans
  • Magnetic Resonance Imaging*
  • Mice
  • Molecular Structure
  • Radiography
  • Umbelliferones / chemistry*
  • beta-Galactosidase / chemistry*


  • Contrast Media
  • Galactosides
  • Umbelliferones
  • cyclohexenoesculetin-beta-galactoside
  • beta-Galactosidase