RNA Interference–Mediated Choline Kinase Suppression in Breast Cancer Cells Induces Differentiation and Reduces Proliferation

Abstract

Choline kinase is overexpressed in breast cancer cells and activated by oncogenes and mitogenic signals, making it a potential target for cancer therapy. Here, we have examined, for the first time, the effects of RNA interference (RNAi)-mediated down-regulation of choline kinase in nonmalignant and malignant human breast epithelial cell lines using magnetic resonance spectroscopy (MRS) as well as molecular analyses of proliferation and differentiation markers. RNAi knockdown of choline kinase reduced proliferation, as detected by proliferating cell nuclear antigen and Ki-67 expression, and promoted differentiation, as detected by cytosolic lipid droplet formation and expression of galectin-3. The functional importance of RNAi-mediated choline kinase down-regulation on choline phospholipid metabolism was confirmed by the significant reduction of phosphocholine detected by MRS. These results strongly support the targeting of choline kinase in breast cancer cells with RNAi and show the potential ability of noninvasive MRS to detect and evaluate future treatments incorporating such strategies. (Cancer Res 2005; 65(23): 11034-43)

Metabolic assessment of the action of targeted cancer therapeutics using magnetic resonance spectroscopy

“…Ex vivo 31 P-and 1 H-MRS analyses of MN58b-treated tumour extracts showed a significant reduction in PC when compared with controls, confirming that the decreases in PMEs and tCho observed in vivo were because of a decrease in PC . In agreement with these findings, inhibition of ChoK using RNA interference in human breast cancer cells was also associated with an MRS-detectable decrease in PC (Glunde et al, 2005). These studies highlight the role of PC, tCho and PMEs as potential noninvasive biomarkers for ChoK inhibition.…”

“…Various studies have focused on ChoK expression/activity as a major regulator of cellular PC, and its link to tumourigenesis (Ramirez de Molina et al, 2004;Glunde et al, 2005). Hence, the role of ChoK in the MRS-detectable changes in PC after treatment with targeted drugs was investigated.…”

Exploiting tumor metabolism for non-invasive imaging of the therapeutic activity of molecularly targeted anticancer agents

“…In line with these observations, RNA interference-mediated knockdown of ChoK in human breast cancer cells resulted in decreased cellular PC content. 69 Taken together these findings suggest that PC, total choline and PME could have potential as non-invasive metabolic imaging biomarkers for the action of drugs targeted at ChoK. FASN inhibition.…”

Selective inhibition of choline kinase simultaneously attenuates MAPK and PI3K/AKT signaling

“…In mammalian cells, there exist at least three isoforms of choline kinase-the mRNA splice variants choline kinase-a1 and choline kinase-a2, and choline kinase-b, which is encoded by a separate gene (Aoyama et al, 2002(Aoyama et al, , 2004. Inhibition of choline kinase-a and choline kinase-b mRNA expression in breast adenocarcinoma cells using choline kinase small interfering RNA (siRNA) reduces intracellular phosphocholine, which in turn decreases cellular proliferation and promotes differentiation (Glunde et al, 2005). Furthermore, transfection with choline kinase small hairpin RNA plasmids specific for choline kinase-a selectively reduces proliferation and increases apoptosis in breast adenocarcinoma cells, but not in normal human mammary epithelial cells (Banez-Coronel et al, 2008).…”