Hypoxia Regulates Choline Kinase Expression through Hypoxia-Inducible Factor-1α Signaling in a Human Prostate Cancer Model

Abstract

The intensity of the total choline (tCho) signal in spectroscopic images of tumors is spatially heterogeneous. The likewise heterogeneous physiologic tumor microenvironment may contribute to this heterogeneity. We therefore investigated the relationship between hypoxia, choline metabolites, and choline kinase (Chk) in a human prostate cancer model. Human PC-3 prostate cancer cells were engineered to express enhanced green fluorescent protein (EGFP) under hypoxic conditions. These PC-3-5HRE-EGFP cells were characterized in culture and as tumors transplanted in mice using 1 H magnetic resonance spectroscopy (MRS) and MRS imaging (MRSI) combined with EGFP fluorescence microscopy and imaging. Hypoxic EGFP-fluorescing tumor regions colocalized with regions of high tCho in combined MRSI and optical imaging studies. Cellular phosphocholine (PC) and tCho concentrations as well as Chk expression levels significantly increased following exposure of PC-3 cells to hypoxia. A putative promoter region located 5 ¶ of the translation start site of the human chk-a gene was cloned and luciferase (Luc)-based reporter vector constructs were generated. Luc reporter assays provided evidence that some of the putative hypoxia response elements (HRE) within this putative chk-a promoter region functioned in vitro. Chromatin immunoprecipitation assays using an antibody against hypoxia-inducible factor (HIF)-1A showed that HIF-1 can directly bind this region of the endogenous chk-a promoter in hypoxic PC-3-5HRE-EGFP cells. These data suggest that HIF-1 activation of HREs within the putative chk-a promoter region can increase Chk-A expression within hypoxic environments, consequently increasing cellular PC and tCho levels within these environments. [Cancer Res 2008;68(1):172-80]

A functional siRNA screen identifies genes modulating angiotensin II-mediated EGFR transactivation

“…Homozygous knockout of CHKA in mice results in embryonic lethality at the blastocyst stage (Wu et al, 2008), whereas upregulation of CHKA activity, or increased abundance of choline/PCho is commonly observed in cancer (Glunde et al, 2008;Hernando et al, 2009;Miyake and Parsons, 2012). CHKA is required for growth-factor-induced cellular proliferation in primary human mammary epithelial cells (Ramírez de Molina et al, 2004).…”

Choline phosphorylation and regulation of transcription of choline kinase α in hypoxia

“…In the promoter region upstream of human choline kinase ␣ (hChK ␣ ), six previously identifi ed HRE sites relative to +1 translation start site ( 19 ) were confi rmed as HRE1 ( Ϫ 1723); HRE2 ( Ϫ 1460); HRE3 ( Ϫ 1027); HRE4 ( Ϫ 880); HRE5 ( Ϫ 851); and HRE6 ( Ϫ 825) ( Fig. 5 ).…”

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

“…As both FASN (Yang et al, 2002) and ChoK (Ramírez de Molina et al, 2002) are regulated by MEK-ERK1/2 and PI3K, ChoK could be involved in PC reduction following inhibition of these pathways. Furthermore, regulation of ChoK expression by hypoxia through HIF-1a has been reported (Glunde et al, 2008). This could be the mechanism underlying the MRS-detected decrease in choline-containing metabolites following inhibition of HIF-1a by genetic (Griffiths et al, 2002) or pharmacological (PX-478) approaches (Jordan et al, 2005).…”