Abstract
Sierra A. Colavito1, James T. Platt2, Matthew A. Held3, Zongzhi Liu2, Ryan Sokup1 and David F. Stern4,5
1 Department of Biology, University of Wisconsin-La Crosse, La Crosse, WI, USA
2 Department of Internal Medicine and Yale Cancer Center, Yale School of Medicine, New Haven, CT, USA
3 Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH, USA
4 Department of Pathology, Yale School of Medicine, New Haven, CT, USA
5 Yale Cancer Center, New Haven, CT, USA
Correspondence to:
Sierra A. Colavito, | email: | scolavito@uwlax.edu |
Keywords: epithelial-mesenchymal transition; triple-negative breast cancer; targeted drug combination screen; claudin-low breast cancer; CHK1
Received: June 25, 2019 Accepted: July 05, 2019 Published: August 06, 2019
ABSTRACT
Mesenchymal stem-like (MSL) breast cancers are enriched for cells with tumor reconstituting and mesenchymal characteristics. These cancers are often triple-negative and have a poor prognosis. Few effective targeted treatment options exist for patients with these cancers, and even when targeted therapies exist, resistance often arises and tumors recur, due in part to drug-tolerant persisting tumor cells with self-renewal capability. Effective treatment strategies will combine agents that target the bulk-tumor and reconstituting cells. In order to identify such a combination therapy, we conducted an inhibitor screen using 40 targeted agents at three different doses in all pairwise combinations. Checkpoint Kinase 1 (CHK1) inhibitors were identified as potent inhibitors of MSL breast cancers. When combined with a pro-apoptotic agent/B Cell Lymphoma 2 (BCL2) inhibitor, the effectiveness of the combination regimen was super-additive compared to either treatment alone and was selective for MSL cancers. Treatment of MSL breast cancer cells results in DNA damage, cell-cycle defects characterized by a prolonged S-phase, increased apoptosis and decreased colony forming abilities compared to untreated cells. These data suggest that a combination of a CHK1 and BCL2 inhibitor could be an effective treatment for patients with MSL breast cancer. Several other effective drug combinations were also identified.