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 1

Activated EGFR signaling regulates KLF6 transcription in lung adenocarcinoma.

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Activated EGFR signaling regulates KLF6 transcription in lung adenocarci...
(A) Patient-derived lung adenocarcinoma tumor samples with matched normal tissue adjacent to the retrieved tumor were evaluated for KLF6 mRNA expression by qRT-PCR using validated WT KLF6-specific primers and normalized to 3 independent housekeeping genes (GAPDH, actin, and 18S transcripts). Data are presented as fold change in KLF6 mRNA expression compared with the matched normal tissue for each sample pair. (B) Homogenized protein lysates from both tumor and normal samples were probed with a polyclonal KLF6 antibody and quantitated via densitometry. (C) Confirmation of human-derived transgenic EGFRL858R tetracycline-inducible expression in mouse lung tissue samples compared with WT littermates on a doxycycline-supplemented diet. Expression of human cDNA EGFRL858R expression was assessed using qRT-PCR with hEGFR-specific primers (n = 4). (D) Western blot of EGFRL858R tumor and WT littermate protein lysates confirming EGFR expression using a monoclonal EGFRL858R antibody. KLF6 protein expression normalized to tubulin is also shown. (E) qRT-PCR for KLF6 mRNA expression in L858R mouse lung tissue samples compared with WT littermates using mouse-specific KLF6 primers. (F) qRT-PCR for KLF6 mRNA expression in L858R mouse tumor samples after treatment with erlotinib compared with vehicle-treated control mice. Whiskers represent the range of expression, and the horizontal lines show the median. (G) Western blot for KLF6 and cleaved caspase-3 normalized to mouse tubulin for L858R mice tumor samples after treatment with erlotinib compared with vehicle. *P < 0.05, **P < 0.01, ***P < 0.001.