HSPG2 and breast cancer: It has been suggested that PC accumulation in BC is caused by an unbalance between a high activity of the enzyme choline kinase in the anabolic pathway [73, 82, 83] and the activity of the enzymes phospholipases A2 (PLA2), phospholipase C (PLC) and phospholipase D (PLD) in the catabolic pathway [73, 84–87].