Acquired resistance to EGFR tyrosine kinase inhibitors in cancer cells is mediated by loss of IGF-binding proteins.
Although some cancers are initially sensitive to EGFR tyrosine kinase inhibitors (TKIs), resistance invariably develops. We investigated mechanisms of acquired resistance to the EGFR TKI gefitinib by generating gefitinib-resistant (GR) A431 squamous cancer cells. In GR cells, gefitinib reduced phosphorylation of EGFR, ErbB-3, and Erk but not Akt. These cells also showed hyperphosphorylation of the IGFI receptor (IGFIR) and constitutive association of IRS-1 with PI3K. Inhibition of IGFIR signaling disrupted the association of IRS-1 with PI3K and restored the ability of gefitinib to downregulate PI3K/Akt signaling and to inhibit GR cell growth. Gene expression analyses revealed that GR cells exhibited markedly reduced IGF-binding protein 3 (IGFBP-3) and IGFBP-4 RNA. Addition of recombinant IGFBP-3 restored the ability of gefitinib to downregulate PI3K/Akt signaling and to inhibit cell growth. Finally, gefitinib treatment of mice with A431 xenografts in combination with an IGFIR-specific monoclonal antibody prevented tumor recurrence, whereas each drug given alone was unable to do so. These data suggest that loss of expression of IGFBPs in tumor cells treated with EGFR TKIs derepresses IGFIR signaling, which in turn mediates resistance to EGFR antagonists. Moreover, combined therapeutic inhibition of EGFR and IGFIR may abrogate this acquired mechanism of drug resistance and is thus worthy of prospective clinical investigation.
Guix
Marta
M
Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6307, USA.
Faber
Anthony C
AC
Wang
Shizhen Emily
SE
Olivares
Maria Graciela
MG
Song
Youngchul
Y
Qu
Sherman
S
Rinehart
Cammie
C
Seidel
Brenda
B
Yee
Douglas
D
Arteaga
Carlos L
CL
Engelman
Jeffrey A
JA
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000037:antagonists & inhibitors*; D005260:Female; D000077156:Gefitinib; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics / Q000378:metabolism; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D007335:Insulin-Like Growth Factor II / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology / Q000627:therapeutic use; D020893:Receptor, ErbB-3 / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
D048868:Adaptor Proteins, Signal Transducing; D066246:ErbB Receptors; D000077156:Gefitinib; D055504:Insulin Receptor Substrate Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines; D020893:Receptor, ErbB-3; D017526:Receptor, IGF Type 1; C526292:IRS1 protein, human; C526295:Irs1 protein, mouse