Genetic Disruption of KEAP1/CUL3 E3 Ubiquitin Ligase Complex Components is a Key Mechanism of NF-KappaB Pathway Activation in Lung Cancer Kelsie L. Thu, BSc, Larissa A. Pikor, BSc, Raj Chari, PhD, Ian M. Wilson, PhD, Calum E. MacAulay, PhD, John C. English, MD, Ming- Sound Tsao, MD, Adi F. Gazdar, MD, Stephen Lam, MD, Wan L. Lam, PhD, William W. Lockwood, PhD Journal of Thoracic Oncology Volume 6, Issue 9, Pages 1521-1529 (September 2011) DOI: 10.1097/JTO.0b013e3182289479 Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions
FIGURE 1 The KEAP1 Cullin-3 E3-ubiquitin ligase complex and its roles in maintaining cellular levels of NRF2 and IKBKB. A, When complex components are intact, KEAP1 facilitates binding of NRF2 or IKBKB, which promotes their ubiquitination. This complex prevents accumulation of IKBKB and subsequent NF-κB activation. B, Disruption of any complex component compromises function leading to stabilization and accumulation of IKBKB and aberrant activation of NF-κB. Journal of Thoracic Oncology 2011 6, 1521-1529DOI: (10.1097/JTO.0b013e3182289479) Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions
FIGURE 2 Frequent disruption of the KEAP1 E3-ligase complex components and IKBKB in non-small cell lung cancer (NSCLC). A, Summary of DNA copy number and gene expression alterations in NSCLC tumors. B, Copy number analysis of 261 lung tumors revealed frequent loss of KEAP1, RBX1, and CUL3 and frequent gain of IKBKB. Vertical columns indicate individual tumor samples, and only samples with ≥1 alterations are shown. C, Messenger RNA (mRNA) expression profiles for 48 lung tumors revealed frequent underexpression of complex components and overexpression of IKBKB. Expression was considered altered if tumor/matched nonmalignant tissue was changed more than twofold. D, KEAP1, CUL3, and IKBKB exhibit statistically significant differences in copy number alteration patterns between adenocarcinoma (AC) and squamous cell carcinoma (SCC) (Fisher's exact test, p < 0.01). Journal of Thoracic Oncology 2011 6, 1521-1529DOI: (10.1097/JTO.0b013e3182289479) Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions
FIGURE 3 IKBKB protein expression in non-small cell lung cancer (NSCLC). A, Western blot depicting IKBKB protein expression in eight cell lines with varying degrees of genetic disruption to KEAP1 E3-ligase complex components and/or IKBKB (as determined from copy number profiles of 90 NSCLC cell lines). Nonmalignant human bronchial epithelial (NHBE) lung line provides a baseline for IKBKB expression. The number of disrupted genes for each line is indicated above the cell line. B, qPCR assessment of mRNA expression levels for KEAP1, RBX1, and CUL3 after siRNA-mediated knockdown relative to a nontargeting control (siNTC). Error bars represent the standard error in relative expression across all biological replicates. C, Western blot depicting the effects of transient siRNA knockdown of KEAP1, RBX1, and CUL3, on total and phospho-IKBKB and NF-κB protein levels. Journal of Thoracic Oncology 2011 6, 1521-1529DOI: (10.1097/JTO.0b013e3182289479) Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions
FIGURE 4 Activation of NF-κB targets in tumors with aberrant expression of KEAP1 E3-ligase complex components and/or IKBKB. A–D, Box and whisker plots demonstrating four examples of NF-κB target genes (BCL2L11, CXCL13, MMP9, and TRAF1) that are significantly up-regulated in tumors with underexpression of KEAP1, RBX1, and/or CUL3 or overexpression of IKBKB, relative to matched nonmalignant lung tissues (Wilcoxon sign rank test, p ≤ 0.001). Copy number status of the NF-κB target gene loci was determined in these tumors to ensure that overexpression was not due to dosage changes of the target genes. Journal of Thoracic Oncology 2011 6, 1521-1529DOI: (10.1097/JTO.0b013e3182289479) Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions
FIGURE 5 Pharmacological inhibition of IKBKB in non-small cell lung cancer (NSCLC) cells. Alamar blue cell viability assays were performed to measure the effect of IKBKB inhibition by a cell permeable, competitive ATP inhibitor, IKK-2 inhibitor IV on five NSCLC cell lines. H2122, H23, H3255, and HCC95 harbored genetic alterations to either IKBKB or one or more of the KEAP1 E3-ligase complex components, whereas H1650 was not altered at the DNA level. Journal of Thoracic Oncology 2011 6, 1521-1529DOI: (10.1097/JTO.0b013e3182289479) Copyright © 2011 International Association for the Study of Lung Cancer Terms and Conditions