S-Gal®, a novel1H MRI reporter for β-galactosidase

Weina Cui, Li Liu, Vikram D. Kodibagkar, Ralph P. Mason

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Reporter genes and associated enzyme activity are becoming increasingly significant for research in vivo. The lacZ gene and β-galactosidase (β-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 β-D-galactopyranoside (S-Gal®) is a commercial histologic stain, which forms a black precipitate in the presence of β-gal and ferric ions, suggesting potential detectability by MRI. Generation of the precipitate is now shown to cause strong T2* relaxation, revealing β-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 β-gal activity. Proof of principle is shown in human breast tumor xenografts in mice. Upon direct injection of a mixture of 3,4-cyclohexenoesculetin β-D-galactopyranoside and ferric ammonium citrate, intense contrast was observed immediately in MCF7-lacZ tumors, but not in wild-type tumors. 3,4-Cyclohexenoesculetin β-D-galactopyranoside activation in combination with ferric ions introduces a novel approach for assaying enzyme activity by MRI in vivo.

Original languageEnglish (US)
Pages (from-to)65-71
Number of pages7
JournalMagnetic Resonance in Medicine
Issue number1
StatePublished - Jul 2010
Externally publishedYes


  • Ferric ammonium citrate
  • MCF7 breast tumor
  • Reporter gene
  • S-Gal®
  • lacZ
  • β-galactosidase

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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