Controlled gene expression with a reverse tetracycline-regulated retroviral vector (RTRV) system.

A retroviral vector was constructed with an autoregulatory cassette to allow expression of the gene of interest in response to oral administration of doxycycline (Dox) in vivo. The cassette contains all the components of the reverse tetracycline-regulated (rtTA) system, a drug selectable marker with the internal ribosome entry site and the gene of interest (GFP). FACS analyses showed an induction of GFP-fluorescence of two orders of magnitude in retrovirus-infected 208F cells dependent on the amount of Dox in the medium. Furthermore, oral administration of Dox resulted in GFP expression in transplanted 208F cells in the peritoneal cavity of nude mice. Thus this reverse tetracycline-regulated retroviral vector (RTRV) system simplifies the delivery of controllable genes to cultured and implanted cells. It is hoped that this approach may pave the way to controlled gene expression during a particular window of time in gene therapy applications.