4-Epidoxycycline: an alternative to doxycycline to control gene expression in conditional mouse models

Biochem Biophys Res Commun. 2004 Oct 22;323(3):979-86. doi: 10.1016/j.bbrc.2004.08.187.


Since the pioneering work by Gossen and Bujard in 1992 demonstrating the usefulness of the Escherichia coli derived tet resistance operon for regulating gene expression a large collection of doxycycline-controlled transgenic mice has been established. Gene switching in eukaryotic tissue culture cells or mice requires administration of tetracycline, anhydrotetracycline or doxycycline to efficiently inactivate the transactivator protein tTA (TET-OFF system) or alternatively to activate the reverse transactivator protein rtTA (TET-ON system). However, the antibiotic activity of doxycycline can create an imbalance of the intestinal flora, resulting in diarrhoea and in a smaller number of animals in colitis. Previous studies reported that 4-epidoxycycline (4-ED), a hepatic metabolite of doxycycline, does not function as an antibiotic in mice. This gave us the idea that 4-ED might be useful for controlling gene expression in mice without the unwanted antibiotic side effect. To study the applicability of 4-ED for control of gene expression we used cell lines expressing the oncogene HER2 under control of tTA (TET-OFF) as well as rtTA (TET-ON). 4-ED and doxycycline were similarly efficient in switching on or -off HER2 expression. In vivo we used a conditional mouse model that allows switching off HER2 in tumor tissue. We show that (i) doxycycline, 7.5mg/ml in drinking water (used as a positive control), (ii) 4-ED, 7.5mg/ml in drinking water, (iii) 4-ED, 10mg/kg body weight, s.c., and (iv) anhydrotetracycline, 10mg/kg, s.c. (used as a second positive control), were similarly efficient. Using mice with tumor volumes of 1.6cm(3) all four schedules led to a tumor remission of more than 95% within 7 days. In conclusion, 4-ED is similarly efficient as doxycycline to control gene expression in vitro and in mice. Since 4-ED lacks the antibiotic activity of doxycycline it may help to avoid adverse side effects and selection of resistant bacteria.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Administration, Oral
  • Animals
  • Antineoplastic Agents / administration & dosage
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / metabolism*
  • Cell Line, Tumor
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Doxycycline / administration & dosage*
  • Gene Expression Regulation, Neoplastic / drug effects*
  • Male
  • Mice
  • Mice, Nude
  • Mice, Transgenic
  • NIH 3T3 Cells
  • Rats
  • Receptor, ErbB-2 / metabolism*
  • Stereoisomerism
  • Tetracyclines / administration & dosage
  • Treatment Outcome


  • Antineoplastic Agents
  • Tetracyclines
  • 4-epianhydrotetracycline
  • Receptor, ErbB-2
  • Doxycycline