phosphatidylinositol-5-phosphate and Carcinoma

Inositol-derived metabolites (e.g., phosphoinositides and inositol polyphosphates) are key second messengers that are essential for controlling a wide range of cellular events. Inositol polyphosphate multikinase (IPMK) exhibits complex catalytic activities that eventually yield water-soluble inositol polyphosphates (e.g., IP4 and IP5) and lipid-bound phosphatidylinositol 3,4,5-trisphosphate. A series of recent studies have suggested that IPMK may be a multifunctional regulator in the nucleus of mammalian cells. In this review, we highlight the novel modes of action of IPMK in transcriptional and epigenetic regulation, and discuss its roles in physiology and disease.

Topics: Animals; Carcinoma; Cell Nucleus; Epigenesis, Genetic; Epithelial Cells; Humans; Intestinal Neoplasms; Mutation; Phosphatidylinositol 3-Kinases; Phosphatidylinositol Phosphates; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction; Transcription, Genetic

Previously, we have shown that the phosphoinositide metabolizing enzymes PIKfyve (phosphoinositide 5-kinase, FYVE finger containing) and MTMR3 (myotubularin-related protein 3), together with their lipid product PtdIns5P, are important for migration of normal human fibroblasts. As these proteins are a kinase and a phosphatase respectively, and thereby considered druggable, we wanted to test their involvement in cancer cell migration and invasion. First, we showed that PIKfyve and MTMR3 are expressed in most cancer cells. Next, we demonstrated that depletion of PIKfyve or MTMR3 resulted in decreased velocity in three different cancer cell lines by using new software for cell tracking. Inhibition of the enzymatic activity of PIKfyve by the inhibitor YM201636 also led to a strong reduction in cell velocity. Mechanistically, we show that PIKfyve and MTMR3 regulate the activation of the Rho family GTPase Rac1. Further experiments also implicated PtdIns5P in the activation of Rac1. The results suggest a model for the activation of Rac1 in cell migration where PIKfyve and MTMR3 produce PtdIns5P on cellular membranes which may then serve to recruit effectors to activate Rac1. Finally, in an invasion assay, we demonstrate that both PIKfyve and MTMR3 are implicated in invasive behaviour of cancer cells. Thus PIKfyve and MTMR3 could represent novel therapeutic targets in metastatic cancer.

Topics: Carcinoma; Cell Line; Cell Line, Tumor; Cell Movement; Cell Polarity; Computational Biology; Databases, Genetic; Enzyme Activation; Enzyme Inhibitors; Expert Systems; Gene Expression Regulation, Neoplastic; Humans; Neoplasm Invasiveness; Neoplasm Proteins; Phosphatidylinositol 3-Kinases; Phosphatidylinositol Phosphates; Phosphoinositide-3 Kinase Inhibitors; Protein Tyrosine Phosphatases, Non-Receptor; rac1 GTP-Binding Protein; RNA Interference; Sarcoma; Software