Proapoptotic BH3-only BCL-2 family protein BIM connects death signaling from epidermal growth factor receptor inhibition to the mitochondrion.
A subset of lung cancers expresses mutant forms of epidermal growth factor receptor (EGFR) that are constitutively activated. Cancers bearing activated EGFR can be effectively targeted with EGFR inhibitors such as erlotinib. However, the death-signaling pathways engaged after EGFR inhibition are poorly understood. Here, we show that death after inhibition of EGFR uses the mitochondrial, or intrinsic, pathway of cell death controlled by the BCL-2 family of proteins. BCL-2 inhibits cell death induced by erlotinib, but BCL-2-protected cells are thus rendered BCL-2-dependent and sensitive to the BCL-2 antagonist ABT-737. BH3 profiling reveals that mitochondrial BCL-2 is primed by death signals after EGFR inhibition in these cells. As this result implies, key death-signaling proteins of the BCL-2 family, including BIM, were found to be up-regulated after erlotinib treatment and intercepted by overexpressed BCL-2. BIM is induced by lung cancer cell lines that are sensitive to erlotinib but not by those resistant. Reduction of BIM by siRNA induces resistance to erlotinib. We show that EGFR activity is inhibited by erlotinib in H1650, a lung cancer cell line that bears a sensitizing EGFR mutation, but that H1650 is not killed. We identify the block in apoptosis in this cell line, and show that a novel form of erlotinib resistance is present, a block in BIM up-regulation downstream of EGFR inhibition. This finding has clear implications for overcoming resistance to erlotinib. Resistance to EGFR inhibition can be modulated by alterations in the intrinsic apoptotic pathway controlled by the BCL-2 family of proteins.
Deng
Jing
J
Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Shimamura
Takeshi
T
Perera
Samanthi
S
Carlson
Nicole E
NE
Cai
Dongpo
D
Shapiro
Geoffrey I
GI
Wong
Kwok-Kin
KK
Letai
Anthony
A
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics*; D000072224:Bcl-2-Like Protein 11; D002289:Carcinoma, Non-Small-Cell Lung; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D000069347:Erlotinib Hydrochloride; D020869:Gene Expression Profiling; D006801:Humans; D008175:Lung Neoplasms; D008565:Membrane Proteins / Q000235:genetics*; D008928:Mitochondria / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011799:Quinazolines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D011799:Quinazolines; D034741:RNA, Small Interfering; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D053453:Caspase 9