Tet-Off cell lines are host cell lines that greatly simplify the task of setting up a tetracycline-inducible gene expression system that is activated by removing doxycycline (Dox) from the culture medium. Tet-On 3G cell lines, which are our highest-performing pre-made cell lines for this system, are located on a separate page. Tet-On 3G cell lines are activated by removing Dox from the culture medium.