Abstract 1432: Understanding the roles of Choline kinase-α in lipid metabolism of breast cancer cells

Abstract Phosphatidylcholine (PtdCho) has important roles in membrane structure and cell signaling. Increased levels of choline kinase (Chk)-α, the enzyme that converts choline to phosphocholine (PC) in the PtdCho biosynthesis, and PC are consistently observed in aggressive cancers including breast cancer [1-3]. Understanding the roles of Chk-α in cancer can result in new therapies. We previously showed that the Chk-α protein, but not PC was essential for cell survival of two triple negative breast cancer cell lines, MDA-MB-231 and SUM149. A Chk-α inhibitor, V-11-0711 (Vertex Pharmaceuticals (Europe) Ltd), reduced the function of Chk-α by binding to the active site and inhibiting the catalytic activity but did not affect Chk-α protein levels. Here we have investigated lipid metabolism in these breast cancer cells and identified PtdCho as an important factor in breast cancer cell survival. Immunoblot analysis showed a slight increase of Chk-α protein after 48 h treatment with V-11-0711 in MDA-MB-231 cells. In SUM149 cells, Chk-α protein level did not change after V-11-0711 treatment. There was no significant reduction of % cell number in MDA-MB-231 cells treated with up to 10µM V-11-0711 compared with vehicle control (0.1% DMSO). In SUM149, 0.1µM V-11-0711 treatment did not affect % cell number, but 1µM V-11-0711 treatment significantly reduced % cell number. 1H NMR spectroscopy of the lipid-soluble phase showed that fatty acid and PtdE levels did not change significantly after V-11-0711 treatment in both cell lines. PtdCho levels decreased slightly in MDA-MB-231, which was not significant. In SUM149 PtdCho levels decreased dose dependently and significantly following treatment with 1µM V-11-0711. We previously showed that significant reduction of PC under these conditions did not markedly affect proliferation of breast cancer cells if Chk-α protein levels were not reduced. Our results here show that cells can survive if PtdCho levels are not reduced significantly even if PC levels are low. The two cell lines we used showed different effects against V-11-0711. MDA-MB-231 cells were more resistant to V-11-0711 and showed no significant reduction of PtdCho levels. This may be partly due to different homeostatic regulation of related enzymes such as Chk-α in these cells that increased Chk-α protein level slightly after treatment. Taken together, these data demonstrate that reduction of PC has little affect on the proliferation of breast cancer cells as long as Chk-α protein levels and PtdCho levels are not reduced. Chk-α protein and PtdCho, but not PC, may be essential in cancer cell proliferation. These data support the development of strategies that destabilize or downregulate Chk-α protein and PtdCho. [1] Aboagye E et al, Cancer Res, 59, 80 (1999); [2] Ackerstaff E et al, Cancer Res, 61, 3599 (2001); [3] Ramirez de M et al, Oncogene, 21,4317 (2002). This work was supported by NIH R01 CA73850 and P50 CA103175. Citation Format: Noriko Mori, Flonné Wildes, Kristine Glunde, Zaver M. Bhujwalla. Understanding the roles of Choline kinase-α in lipid metabolism of breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1432. doi:10.1158/1538-7445.AM2014-1432