TAK-960, a novel, orally available, selective inhibitor of polo-like kinase 1, shows broad-spectrum preclinical antitumor activity in multiple dosing regimens.

Polo-like kinase 1 (PLK1) is a serine/threonine protein kinase involved in key processes during mitosis. Human PLK1 has been shown to be overexpressed in various human cancers, and elevated levels of PLK1 have been associated with poor prognosis, making it an attractive target for anticancer therapy. TAK-960 [4-[(9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino]-2-fluoro-5-methoxy-N-(1-methylpiperidin-4-yl) benzamide] is a novel, investigational, orally bioavailable, potent, and selective PLK1 inhibitor that has shown activity in several tumor cell lines, including those that express multidrug-resistant protein 1 (MDR1). Consistent with PLK1 inhibition, TAK-960 treatment caused accumulation of G(2)-M cells, aberrant polo mitosis morphology, and increased phosphorylation of histone H3 (pHH3) in vitro and in vivo. TAK-960 inhibited proliferation of multiple cancer cell lines, with mean EC(50) values ranging from 8.4 to 46.9 nmol/L, but not in nondividing normal cells (EC(50) >1,000 nmol/L). The mutation status of TP53 or KRAS and MDR1 expression did not correlate with the potency of TAK-960 in the cell lines tested. In animal models, oral administration of TAK-960 increased pHH3 in a dose-dependent manner and significantly inhibited the growth of HT-29 colorectal cancer xenografts. Treatment with once daily TAK-960 exhibited significant efficacy against multiple tumor xenografts, including an adriamycin/paclitaxel-resistant xenograft model and a disseminated leukemia model. TAK-960 has entered clinical evaluation in patients with advanced cancers.

The Formin family protein, formin homolog overexpressed in spleen, interacts with the insulin-responsive aminopeptidase and profilin IIa.

Insulin stimulates translocation of glucose transporter isoform type 4 (GLUT4) and the insulin-responsive aminopeptidase (IRAP) from an intracellular storage pool to the plasma membrane in muscle and fat cells. A role for the cytoskeleton in insulin action has been postulated, and the insulin signaling pathway has been well investigated; however, the molecular mechanism by which GLUT4/IRAP-containing vesicles move from an interior location to the cell surface in response to insulin is incompletely understood. Here, we have screened for IRAP-binding proteins using a yeast two-hybrid system and have found that the C-terminal domain of FHOS (formin homolog overexpressed in spleen) interacts with the N-terminal cytoplasmic domain of IRAP. FHOS is a member of the Formin/Diaphanous family of proteins that is expressed most abundantly in skeletal muscle. In addition, there are two novel types of FHOS transcripts generated by alternative mRNA splicing. FHOS78 has a 78-bp insertion and it is expressed mainly in skeletal muscle where it may be the most abundant isoform in humans. The ubiquitously expressed FHOS24 has a 24-bp insertion encoding an in-frame stop codon that results in a truncated polypeptide. It is known that some formin family proteins interact with the actin-binding profilin proteins. Both FHOS and FHOS78 bound to profilin IIa via their formin homology 1 domains, but neither bound profilin I or IIb. Overexpression of FHOS and FHOS78 resulted in enhanced insulin-stimulated glucose uptake in L6 cells to similar levels. However, overexpression of FHOS24, lacking the IRAP-binding domain, did not affect insulin-stimulated glucose uptake. These findings suggest that FHOS mediates an interaction between GLUT4/IRAP-containing vesicles and the cytoskeleton and may participate in exocytosis and/or retention of this membrane compartment.

3-Morpholinosydnonimine hydrochloride induces p53-dependent apoptosis in murine primary neural cells: a critical role for p21(ras)-MAPK-p19(ARF) pathway.

In some neurological disorders, excessive nitric oxide (NO, nitrogen monoxide) produced by inducible and/or neuronal nitric oxide synthases (iNOS and nNOS) is able to combine with superoxide (O(minus sign)(2)) to form peroxynitrite (ONOO(minus sign)), which can then induce p53-dependent neural apoptosis. In the present study, experiments using p53 knock-out mice primary neural cells revealed that 3-morpholinosydnonimine hydrochloride (SIN-1), a peroxynitrite donor, triggered apoptosis, while p53-transcriptional activity was effectively suppressed in the absence of p53 molecules. This shows that SIN-1 was able to induce p53-dependent apoptosis in murine primary neural cells. The mechanism responsible for the SIN-1-induced accumulation of p53 molecules was then analyzed. Western blot analysis indicated that p53 accumulation caused by SIN-1 did not require p53 phosphorylation, whereas SIN-1 treatment triggered MAP kinase (MAPK) phosphorylation and pretreatment with the MAP kinase kinase (MEK) inhibitor U0126 inhibited p53 accumulation. Pretreatment of the neural cells with lovastatin, an inhibitor of p21(ras) signaling, greatly inhibited the accumulation of p53 induced by SIN-1. Northern blot and immunofluorescence analyses revealed that primary neural cells treated with SIN-1 had increased levels of p19 alternate reading frame (p19(ARF)) mRNA and protein, which is induced by MAPK and stabilizes the p53 protein. Our findings clearly show that the p21(ras)-MAPK-p19(ARF) pathway has an essential role in p53-dependent apoptosis triggered by peroxynitrite in neural cells.