Choline kinase: an important target for cancer.

Choline kinase (ChoK) is a cytosolic enzyme present in various tissues, which catalyzes the phosphorylation of choline to form phosphorylcholine (PCho) in the presence of ATP and magnesium. ChoK is important for the generation of two major membrane phospholipids, phosphatidylcholine (PC) and sphingomyelin (SM) and subsequently for the cell division. ChoK plays a vital role in cell signaling pathways and regulation of cell growth along with PCho involved in malignant transformation through ras oncogenes in different cancers such as breast, lung, colon, prostate, neuroblastoma, hepatic lymphomas, meningiomas and diverse murine tumours. The Ras effectors serine/threonine kinase (Raf-1), the Ral-GDP dissociation stimulator (Ral-GDS) and the phosphatidylinositol 3-kinase (PI3K) are involved in the activation of ChoK during tumorigenesis. ChoK gene induction seems to be associated with certain cell stress or cell defense. Nowadays, RNAi appear to be one of the most promising routes in the cancer therapy. The anticancer potential of both stable expression of siRNAs and their high sequence specificity by RNAi mediated suppression of oncogenic ras in human pancreatic carcinoma, human melanomas and ovarian cancer has been observed. It has an important role in sequence specific post-transcriptional gene silencing mechanism. Presently, the crystal structure of Caenorhabditis elegans choline kinase A-2 (ChoKA-2) is available, which may be useful for comparative modeling of human ChoK and further modeling studies. The present review aims at the general overview of importance, expression, structure, progress in molecular modeling, active site analysis and inhibitors of ChoK. It also highlights the recent role of ChoK in various types of Ras-dependent and Ras-independent carcinogenesis.