Oncogenic stress sensitizes murine cancers to hypomorphic suppression of ATR
David W. Schoppy, … , J. Alan Diehl, Eric J. Brown
David W. Schoppy, … , J. Alan Diehl, Eric J. Brown
Published December 1, 2011
Citation Information: J Clin Invest. 2012;122(1):241-252. https://doi.org/10.1172/JCI58928.
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Research Article

Oncogenic stress sensitizes murine cancers to hypomorphic suppression of ATR

Abstract

Oncogenic Ras and p53 loss-of-function mutations are common in many advanced sporadic malignancies and together predict a limited responsiveness to conventional chemotherapy. Notably, studies in cultured cells have indicated that each of these genetic alterations creates a selective sensitivity to ataxia telangiectasia and Rad3-related (ATR) pathway inhibition. Here, we describe a genetic system to conditionally reduce ATR expression to 10% of normal levels in adult mice to compare the impact of this suppression on normal tissues and cancers in vivo. Hypomorphic suppression of ATR minimally affected normal bone marrow and intestinal homeostasis, indicating that this level of ATR expression was sufficient for highly proliferative adult tissues. In contrast, hypomorphic ATR reduction potently inhibited the growth of both p53-deficient fibrosarcomas expressing H-rasG12V and acute myeloid leukemias (AMLs) driven by MLL-ENL and N-rasG12D. Notably, DNA damage increased in a greater-than-additive fashion upon combining ATR suppression with oncogenic stress (H-rasG12V, K-rasG12D, or c-Myc overexpression), indicating that this cooperative genome-destabilizing interaction may contribute to tumor selectivity in vivo. This toxic interaction between ATR suppression and oncogenic stress occurred without regard to p53 status. These studies define a level of ATR pathway inhibition in which the growth of malignancies harboring oncogenic mutations can be suppressed with minimal impact on normal tissue homeostasis, highlighting ATR inhibition as a promising therapeutic strategy.

Authors

David W. Schoppy, Ryan L. Ragland, Oren Gilad, Nishita Shastri, Ashley A. Peters, Matilde Murga, Oscar Fernandez-Capetillo, J. Alan Diehl, Eric J. Brown

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Figure 5

H-rasG12V-transformed p53+/+ fibrosarcomas that express low levels of p53R175H are also sensitive to hypomorphic ATR reduction.

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H-rasG12V-transformed p53+/+ fibrosarcomas that express low levels of p5...
(A) Quantification of correctly-spliced mouse (ATRfl) and human (ATRseckel) ATR transcript in p53+/+ATRfl/seckelCreERT2+ cell lines ectopically expressing p53R175H and H-rasG12V. Data represent mean ± SEM. (B) Measurement of p53R175H-expressing tumor growth following ATRfl deletion. Tamoxifen treatment was performed on days 1 through 5, as shown in Figure 4. Data represent mean ± SEM. (C) Quantification of γH2AX-positive cells in H-rasG12V–expressing tumors (B) following ATRfl deletion. Tumors were isolated 9–10 days after initial tamoxifen treatment and quantified for γH2AX-positive cells as described in Figure 4E. Data represent mean ± SEM.