Genetic disruption of KEAP1/CUL3 E3 ubiquitin ligase complex components is a key mechanism of NF-kappaB pathway activation in lung cancer.

Abstract

INTRODUCTION:

Inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta (IKBKB) (IKK-β/IKK-2), which activates NF-κB, is a substrate of the KEAP1-CUL3-RBX1 E3-ubiquitin ligase complex, implicating this complex in NF-κB pathway regulation. We investigated complex component gene disruption as a novel genetic mechanism of NF-κB activation in non-small cell lung cancer.

METHODS:

A total of 644 tumor- and 90 cell-line genomes were analyzed for gene dosage status of the individual complex components and IKBKB. Gene expression of these genes and NF-κB target genes were analyzed in 48 tumors. IKBKB protein levels were assessed in tumors with and without complex or IKBKB genetic disruption. Complex component knockdown was performed to assess effects of the E3-ligase complex on IKBKB and NF-κB levels, and phenotypic importance of IKBKB expression was measured by pharmacological inhibition.

RESULTS:

We observed strikingly frequent genetic disruption (42%) and aberrant expression (63%) of the E3-ligase complex and IKBKB in the samples examined. Although both adenocarcinomas and squamous cell carcinomas showed complex disruption, the patterns of gene disruption differed. IKBKB levels were elevated with complex disruption, knockdown of complex components increased activated forms of IKBKB and NF-κB proteins, and IKBKB inhibition detriments cell viability, highlighting the biological significance of complex disruption. NF-κB target genes were overexpressed in samples with complex disruption, further demonstrating the effect of complex disruption on NF-κB activity.

CONCLUSIONS:

Gene dosage alteration is a prominent mechanism that disrupts each component of the KEAP1-CUL3-RBX1 complex and its NF-κB stimulating substrate, IKBKB. Herein, we show that, multiple component disruption of this complex represents a novel mechanism of NF-κB activation in non-small cell lung cancer.

• Authors: Kelsie L Thu, Larissa A Pikor, Raj Chari, Ian M Wilson, Calum E Macaulay, John C English, Ming-Sound Tsao, Adi F Gazdar, Stephen Lam, Wan L Lam, William W Lockwood
• Journal: Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer (J Thorac Oncol) Vol. 6 Issue 9 Pg. 1521-9 (Sep 2011) ISSN: 1556-1380 [Electronic] United States
• PMID: 21795997 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers, Tumor
• CUL3 protein, human
• Carrier Proteins
• Cullin Proteins
• Intracellular Signaling Peptides and Proteins
• KEAP1 protein, human
• Kelch-Like ECH-Associated Protein 1
• NF-kappa B
• RBX1 protein, human
• RNA, Messenger
• RNA, Small Interfering
• I-kappa B Kinase
• IKBKB protein, human

Topics

• Adenocarcinoma (genetics, metabolism, pathology)
• Biomarkers, Tumor (genetics)
• Blotting, Western
• Carcinoma, Squamous Cell (genetics, metabolism, pathology)
• Carrier Proteins (antagonists & inhibitors, genetics, metabolism)
• Cullin Proteins (antagonists & inhibitors, genetics, metabolism)
• Gene Dosage
• Gene Expression Profiling
• Humans
• I-kappa B Kinase (antagonists & inhibitors, genetics, metabolism)
• Intracellular Signaling Peptides and Proteins (antagonists & inhibitors, genetics, metabolism)
• Kelch-Like ECH-Associated Protein 1
• Lung Neoplasms (genetics, metabolism, pathology)
• NF-kappa B (antagonists & inhibitors, genetics, metabolism)
• Neoplasm Staging
• Oligonucleotide Array Sequence Analysis
• Prognosis
• RNA, Messenger (genetics)
• RNA, Small Interfering (genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Survival Rate
• Tumor Cells, Cultured