We have utilized hypomorphic suppression of the ATR checkpoint kinase to promote replication fork collapse into DSBs selectively in oncogene-expressing cells and those lacking the p53 tumor suppressor gene. Understanding the process of replication fork collapse is helpful in determining the ideal genetic contexts in which such therapies should be applied. Towards this objective, we have recently demonstrated that the AURKA-PLK1 pathway and the SUMO-targeted E3 ubiquitin ligase RNF4 are required for fork collapse and DSB formation when ATR is inhibited. In this grant proposal, we will 1) dissect the regulatory interrelationships between AURKA-PLK1, RNF4 and ATR in replication fork stability, 2) characterize the ubiquitination events mediated by the AURKA-PLK1 pathway and RNF4 that drive the disengagement of replication factors from the fork, and 3) determine if the amplification of AURKA activity and replisome sumoylation in human breast cancers promotes sensitivity to ATR/CHK1 inhibitors in cultured cells and orthotopically transplanted tumors in mice. These studies will advance our understanding of the causes of replication fork collapse upon ATR/CHK1 inhibition and investigate the prognostic value of amplified AURKA-PLK1 activity and replisome sumoylation in responsiveness to ATR/CHK1 inhibitor treatments.

Public Health Relevance

Although DNA-damaging chemo- and radio-therapies are the most common standard of care treatments for cancer, their effectiveness is substantially limited by off-target toxicity to normal tissues. We have found that incomplete inhibition of the ATR checkpoint kinase to levels that are tolerable in most normal tissues is selectively toxic to a broad spectrum of cancers through DSB generation. In this proposal, we address the molecular mechanism governing this process, and test the effectiveness of ATR-inhibitor-based therapies against transplanted human breast cancers that genetically may be particularly sensitive to this treatment.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA189743-01A1
Application #
8887710
Study Section
Cancer Etiology Study Section (CE)
Program Officer
Pelroy, Richard
Project Start
2015-04-01
Project End
2020-03-31
Budget Start
2015-04-01
Budget End
2016-03-31
Support Year
1
Fiscal Year
2015
Total Cost
$397,683
Indirect Cost
$120,848
Name
University of Pennsylvania
Department
Biology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Shastri, Nishita; Tsai, Yu-Chen; Hile, Suzanne et al. (2018) Genome-wide Identification of Structure-Forming Repeats as Principal Sites of Fork Collapse upon ATR Inhibition. Mol Cell 72:222-238.e11
Kim, Hyoung; George, Erin; Ragland, Ryan et al. (2017) Targeting the ATR/CHK1 Axis with PARP Inhibition Results in Tumor Regression in BRCA-Mutant Ovarian Cancer Models. Clin Cancer Res 23:3097-3108
George, Erin; Kim, Hyoung; Krepler, Clemens et al. (2017) A patient-derived-xenograft platform to study BRCA-deficient ovarian cancers. JCI Insight 2:e89760