Changes in choline metabolism as potential biomarkers of phospholipase Cγ1 inhibition in human prostate cancer cells

Abstract

Phosphoinositide-specific phospholipase Cγ1 (PLCγ1) is activated downstream of many receptor tyrosine kinases to promote cell motility. Inhibition of this protein is being explored as a therapeutic strategy for blocking cancer cell invasion and metastasis. The clinical development of such cytostatic therapies requires the implementation of pharmacodynamic biomarkers of target modulation. In this study, we use magnetic resonance spectroscopy to explore metabolic biomarkers of PLCγ1 down-regulation in PC3LN3 prostate cancer cells. We show that inhibition of PLCγ1 via an inducible short hairpin RNA system causes a reduction in phosphocholine levels by up to 50% relative to the control as detected by 1 H and 31 P magnetic resonance spectroscopy analyses. This correlated with a rounded-up morphology and reduced cell migration. Interestingly, the fall in phosphocholine levels was not recorded in cells with constitutive PLCγ1 knockdown where the rounded-up phenotype was no longer apparent. This study reveals alterations in metabolism that accompany the cellular effects of PLCγ1 knockdown and highlights phosphocholine as a potential pharmacodynamic biomarker for monitoring the action of inhibitors targeting

Inhibition of phosphatidylcholine-specific phospholipase C results in loss of mesenchymal traits in metastatic breast cancer cells

“…In fact, a PC-PLC-mediated DAG release from PtdCho may contribute to a long-lasting activation of protein kinase C (PKC), a family of isoenzymes involved in different functions, including regulation of BC cell morphology, motility, and invasiveness [49]. A decrease in the DAG pool as a result of PC-PLC inhibition could therefore lead to reduced cell motility due to partial PKC deactivation and subsequent cytoskeletal rearrangements at the cell-leading edge, similarly to the effects of DAG depletion detected in cancer cells exposed to PI-PLC-γ inhibitors [50]. …”

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

“…More recently, inhibition of phosphoinositide-specific PLCg1, an enzyme involved in cell invasion and motility, with inducible shRNA, was associated with a fall in PC that was concomitant with reduced cell adhesion and migration. Interestingly, the effect on PC was not observed in cells with a stable knockdown of PLCg1, in which adhesion defects had been by-passed, suggesting that the change in PC is likely to reflect the phenotypic consequences induced by PLCg1 inhibition (Beloueche-Babari et al, 2009).…”

Histone Deacetylase Inhibition Increases Levels of Choline Kinase α and Phosphocholine Facilitating Noninvasive Imaging in Human Cancers

“…For example, inhibitors of HSP90 (23,24), phospholipase Cg1 (25), mitogen-activated protein kinase (26), or phosphoinositide 3-kinase (27,28) have all been shown to alter choline phospholipid metabolism in human cancer cells. In the case of the HDAC inhibitor LAQ824, in vitro and in vivo MRS showed increased phosphocholine (PC) levels both in human colon cancer cells and tumors posttreatment (29).…”