Abstract P2-02-01: Inhibition of creatine kinase metabolism represses invasion and sensitizes estrogen-receptor negative breast cancer cells to standard chemotherapies

Abstract

Abstract Dysregulated tumor cell metabolism is a hallmark of cancer progression and therapeutic resistance. In a screen for Hypoxia-Inducible Factor (HIF)-dependent genes regulating metabolism, we identified creatine kinase, brain isoform (CKB) as down-regulated in HIF-1 knockout mammary tumor cells. CKB is a member of a family of cytosolic and mitochondrial creatine kinases (CKs) that reversibly catalyze the transfer of a high-energy phosphoryl group from ATP to creatine, generating local stores of phosphocreatine in the forward reaction, and re-generating ATP in the reverse reaction. Creatine kinases are up-regulated in a variety of solid tumors, including breast cancers. CK activity is inhibited by cyclocreatine (cCr), a creatine kinase substrate that represses the CK-dependent generation of ATP from phosphocreatine >170-fold. Knockdown of CKB in tumor cells derived from the polyoma middle T (PyMT) transgenic model of metastatic breast cancer did not impair cell proliferation or wound healing, but potently suppressed invasion in vitro, suggesting utility for treating stage IV disease. When female FVB/Nj mice were injected with wild type PyMT cells in a tail vein assay and then treated with cCr, lung metastasis was repressed to the same extent as CKB gene knockdown. These data were validated using a variety of human estrogen receptor (ER)-negative breast cancer cell lines. CKB loss- and gain-of-function models were created and effects on cell proliferation, survival, wound healing and ATP production were compared to cCr treatment. Overall, whereas deletion of CKB had no effect on cell proliferation or survival in either adherent or suspension conditions, either deletion of CKB or cCr therapy potently reduced intracellular ATP levels, which was associated with reduced invasive potential. In contrast, over-expression of CKB enhanced chemotaxis to EGF and invasion towards serum. Whereas cCr monotherapy is generally cytostatic, combination with either doxorubicin or paclitaxel is synergistic to kill tumor cells. Together, these data suggest that inhibition of CK activity may be effective in treating stage IV breast cancer patients with established metastatic disease. We are currently exploring the cell signaling and cell survival pathways that are altered by CKB gene deletion or cCr treatment to understand how the creatine kinase arm of metabolism promotes tumor progression, metastasis and response to conventional chemotherapies. Citation Format: Barch HP, Krutilina R, Brooks DL, Parke D, Seagroves TN. Inhibition of creatine kinase metabolism represses invasion and sensitizes estrogen-receptor negative breast cancer cells to standard chemotherapies [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-02-01.