A ¹⁹F-NMR approach using reporter molecule pairs to assess β-galactosidase in human xenograft tumors in vivo

Gene therapy has emerged as a promising strategy for treatment of various diseases. However, widespread implementation is hampered by difficulties in assessing the success of transfection in the target tissue and the longevity of gene expression. Thus, there is increasing interest in the development of non-invasive in vivo reporter techniques to assay gene expression. We recently demonstrated the ability to detect β-galactosidase activity in stably transfected human prostate tumor xenografts in mice in vivo using ¹⁹F NMR. We now extend the studies to human MCF7 breast cancer cells growing as xenografts in nude mice. Moreover, by using two spectrally resolved reporters (o-fluoro-p-nitrophenyl-β-D-galactopyranoside and an isomer), two tumors could be interrogated simultaneously revealing lacZ transgene activity in a stably transfected tumor versus no activity in a wild-type tumor. Most significantly, hydrolytic activity observed by ¹⁹F NMR corresponded to differential activity in lacZ-expressing tumors.