Targeting the FOXO1/KLF6 axis regulates EGFR signaling and treatment response
Jaya Sangodkar, … , Analisa DiFeo, Goutham Narla
Jaya Sangodkar, … , Analisa DiFeo, Goutham Narla
Published July 2, 2012; First published June 1, 2012
Citation Information: J Clin Invest. 2012;122(7):2637-2651. https://doi.org/10.1172/JCI62058.
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Research Article Oncology

Targeting the FOXO1/KLF6 axis regulates EGFR signaling and treatment response

Abstract

EGFR activation is both a key molecular driver of disease progression and the target of a broad class of molecular agents designed to treat advanced cancer. Nevertheless, resistance develops through several mechanisms, including activation of AKT signaling. Though much is known about the specific molecular lesions conferring resistance to anti-EGFR–based therapies, additional molecular characterization of the downstream mediators of EGFR signaling may lead to the development of new classes of targeted molecular therapies to treat resistant disease. We identified a transcriptional network involving the tumor suppressors Krüppel-like factor 6 (KLF6) and forkhead box O1 (FOXO1) that negatively regulates activated EGFR signaling in both cell culture and in vivo models. Furthermore, the use of the FDA-approved drug trifluoperazine hydrochloride (TFP), which has been shown to inhibit FOXO1 nuclear export, restored sensitivity to AKT-driven erlotinib resistance through modulation of the KLF6/FOXO1 signaling cascade in both cell culture and xenograft models of lung adenocarcinoma. Combined, these findings define a novel transcriptional network regulating oncogenic EGFR signaling and identify a class of FDA-approved drugs as capable of restoring chemosensitivity to anti-EGFR–based therapy for the treatment of metastatic lung adenocarcinoma.

Authors

Jaya Sangodkar, Neil S. Dhawan, Heather Melville, Varan J. Singh, Eric Yuan, Huma Rana, Sudeh Izadmehr, Caroline Farrington, Sahar Mazhar, Suzanna Katz, Tara Albano, Pearlann Arnovitz, Rachel Okrent, Michael Ohlmeyer, Matthew Galsky, David Burstein, David Zhang, Katerina Politi, Analisa DiFeo, Goutham Narla

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Figure 8

TFP and erlotinib administered in combination decrease tumorigenicity in a xenograft model of lung adenocarcinoma.

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TFP and erlotinib administered in combination decrease tumorigenicity in...
(A) Growth curves of xenograft tumors generated by injection of 5 × 106 H1650 lung adenocarcinoma cells into the right posterior flank of nude mice. Following an initial growth period of 21 days, group tumor volume (n = 14) averaged 200 mm3 prior to treatment. Tumor measurements were made 48 hours after each injection. Data indicate growth curves with DMSO (vehicle control), erlotinib (25 mg/kg), TFP (10 mg/kg), and a combination of TFP and erlotinib. Asterisks represent significance compared with DMSO. (B) qRT-PCR for KLF6 mRNA expression from previously described tumors homogenized after the H1650-injected nude mice were sacrificed 24 hours after final treatment. (C) Western blot analysis of KLF6 expression in homogenized tumor samples (described above). Lysate homogenates from treated and untreated tumors were run and probed in parallel (n = 5) and results normalized to GAPDH. (D) Representative images (original magnification, ×10) of xenograft tumor histology paraffin sections subjected to TUNEL for detection of apoptosis. (E) Cells positive for TUNEL were quantified with NIS-Elements and normalized to nuclear counterstaining by propidium iodide. Quantification is shown for each treatment group. (F) Paraffin histology sections subjected to immunohistochemistry for PCNA. Representative images are shown (original magnification, ×40). (G) Positive nuclear staining, colocalizing with nuclear counterstain hematoxylin, quantified with ImageJ software. Data are shown in box-and-whisker plots for each treatment group. *P < 0.05, **P < 0.01, ***P < 0.001.