Figure 7. In Vivo Correlation of BIM/Bim Expression and Mutant EGFR Activity (A and B) Lung tumor-bearing mice that express a tetracycline-inducible L858R mutant (EGFRL858R) (A) or an exon 19 deletion mutant (EGFRΔL747–S752) (B) were treated with a single dose of either vehicle control or 50 mg/kg erlotinib intraperitoneally. After 13 h, animals were sacrificed and lungs were harvested. Whole lung lysates (for EGFRL858R) or tumor nodule lysates (for EGFRΔL747–S752) were probed by immunoblotting using the indicated antibodies. C+/L+, CCSP-rtTA/tet-o-EGFRL858R bitransgenic mouse; C+/Del+, CCSP-rtTA/tet-o-EGFRΔL747-S752 bitransgenic mouse; pEGFR Y1092, EGFR phosphorylated at a tyrosine residue at position 1092). (C) Lungs from nontransgenic mice and lacking tumors were treated with placebo or erlotinib in the same manner and analyzed for BIM and EGFR expression status. C−/L−, nontransgenic mouse. (D) Nude mice bearing PC-9 xenografts were treated with either vehicle control or 25 mg/kg erlotinib intraperitoneally every 12 h × 2 doses. The xenografts were dissected 24 h after the first injection, and tumor lysates were probed by immunoblotting using the indicated antibodies.