Acquired resistance to EGFR tyrosine kinase inhibitors in cancer cells is mediated by loss of IGF-binding proteins
Marta Guix, … , Carlos L. Arteaga, Jeffrey A. Engelman
Marta Guix, … , Carlos L. Arteaga, Jeffrey A. Engelman
Published June 20, 2008
Citation Information: J Clin Invest. 2008;118(7):2609-2619. https://doi.org/10.1172/JCI34588.
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Research Article

Acquired resistance to EGFR tyrosine kinase inhibitors in cancer cells is mediated by loss of IGF-binding proteins

Abstract

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.

Authors

Marta Guix, Anthony C. Faber, Shizhen Emily Wang, Maria Graciela Olivares, Youngchul Song, Sherman Qu, Cammie Rinehart, Brenda Seidel, Douglas Yee, Carlos L. Arteaga, Jeffrey A. Engelman

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Figure 1

A431 GR cells maintain PI3K/Akt signaling in the presence of gefitinib and remain sensitive to PI3K inhibitors.

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A431 GR cells maintain PI3K/Akt signaling in the presence of gefitinib a...
(A) Parental and A431 GR cells were grown for 72 hours in 0.5% FBS containing medium with or without gefitinib at the indicated μM concentrations. Cell number was determined in a Coulter Counter. Each data point represents the mean ± SD of 3 wells. (B) Parental and A431 GR cells were grown in Matrigel in the absence or presence of gefitinib (1 μM). Pictures were taken after 10 days. Original magnification, ×10. (C) Parental and A431 GR cells were treated for 6 hours in growth medium containing 1 μM gefitinib. Whole-cell lysates were prepared and probed in immunoblots with the indicated antibodies. (D) Parental and GR cells were treated with control, gefitinib (3 μM), or erlotinib (3 μM), and the extracts were probed with the indicated antibodies. (E) Cell growth assays were performed as in A. Cells were treated with the indicated drugs and concentrations. (Gef, gefitinib; Erlot, erlotinib; LY, LY294002). Student’s t test was used for statistical comparisons. Error bars represent SD.