Abstract PR-5: GATA2 is required for oncogene-driven non-small cell lung cancer.
Authors: Kumar Madhu S. 
Published: June 2012

Non-small cell lung cancer (NSCLC) is the most diagnosed and lethal histological type of cancer worldwide. Among NSCLC patients, the most frequently mutated oncogenes are KRAS and EGFR, constituting 40 percent of patients. Thus, there is a need to develop therapies to target these tumors. We performed a RNA interference screen for factors required in KRAS mutant cells and found mutant cells depend on the transcription factor GATA2. Analysis of 26 NSCLC lines revealed GATA2 loss specifically reduces KRAS mutant cell viability. We explored these effects in NSCLC cells mutant for KRAS or EGFR. GATA2 knockdown reduces the viability of NSCLC cells with activating mutations in either KRAS or EGFR, with wild type NSCLC cells growing comparably well. Furthermore, injection of mutant NSCLC cells depleted for GATA2 failed to form tumors, while wild type tumors were unaffected by GATA2 loss. This suggests GATA2 is required specifically in oncogene-driven NSCLC.

To determine the effect of GATA2 on gene expression, we performed transcript profiling of mutant cells with and without GATA2 loss. In response to GATA2 loss in NSCLC cells, we observed suppression of the proteasome. GATA2 loss inhibited activity of the proteasome and restoration of proteasome activity rescued growth in response to GATA2 depletion. Furthermore, GATA2 loss suppressed IL-1 and NF-κB signaling in mutant NSCLC cells. Restoring IL-1 signaling reestablished both NF-κB activity and growth in response to GATA2 knockdown. We further explored GATA2 genome occupancy and gene expression through GATA2 ChIP-seq in NSCLC cells. In mutant NSCLC cells, GATA2 occupancy was enriched in Rho signaling pathway components. Further, we found GATA2 loss suppressed Rho signaling and activation of Rho signaling rescued viability in response to GATA2 loss. Analyzing the DNA motifs from our GATA2 ChIP of mutant NSCLC cells, we observed enrichment of the STAT5 response element. We subsequently isolated a GATA2-STAT5 complex in mutant NSCLC cells; importantly, this complex occupies Rho pathway target genes. Overall, our ChIP-seq suggests GATA2, via STAT5 binding, is recruited to Rho pathway target genes to control Rho signaling.

To examine GATA2 loss in an autochthonous model of NSCLC, we combined conditional Gata2 with oncogenic Kras to generate compound mutant animals. Gata2 deletion suppressed tumor growth compared to wild type animals. We further tested the role for GATA2 in tumor maintenance via systemic deletion of Gata2 in established Kras-mutant lung tumors, which caused complete regression of established lesions. Beyond this, we combined bortezomib, an inhibitor of the proteasome, and fasudil, an inhibitor of Rho signaling, to see if suppression of GATA2-regulated pathways recapitulates GATA2 loss in the Kras lung tumor model. Treatment of Kras mutant mice with these compounds caused a near-complete clearance of tumors. These studies suggest GATA2 is necessary in the Kras mutant tumor model and combined inhibition of GATA2-controlled pathways suppresses lung tumor growth.

Taken together, these findings suggest GATA2 is required for the survival of oncogene-mutant NSCLC cells. Moreover, these results suggest the functional pleiotropy of GATA2, not a traditional druggable target, presents a network of druggable pathways for therapeutic exploitation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr PR-5.