FIG. 5.
Sustained EGFR signaling partially rescues melanoma survival following extinction of H-RASV12G. (A) R545 cells expressing Ereg or empty vector were injected subcutaneously into SCID mice provided with doxycycline in the drinking water. After 14 days, doxycycline was removed (time zero), and tumors were harvested and weighed at successive time points. Mean tumor mass is represented. Four tumors were analyzed per time point. (B and C) Northern blot analysis of regressing melanomas for expression of Ereg (the bands corresponding to endogenous [endo] and retroviral [retro] Ereg are indicated) (B) and EGFR and Eps8 (C). Ethidium bromide (EtBr)-stained gels were used as loading controls. (D) TUNEL staining (arrows) of apoptotic cells at 72 h following doxycycline withdrawal in control (vector) and Ereg-expressing tumors. (E) Measurement of the apoptotic and mitotic indices of during tumor regression. The apoptosis and mitosis rates per high-power field (HPF) are shown.