Pancreatic ductal adenocarcinoma (PDA) is among the most lethal human cancers, in part because it is insensitive to many chemotherapeutic drugs. Studying a mouse model of PDA that is refractory to the clinically used drug gemcitabine, we found that the tumors in this model were poorly perfused and poorly vascularized, properties that are shared with human PDA. We tested whether the delivery and efficacy of gemcitabine in the mice could be improved by coadministration of IPI-926, a drug that depletes tumor-associated stromal tissue by inhibiting the † To whom correspondence should be addressed. david.tuveson@cancer.org.uk.

The advent of molecularly targeted drug discovery has facilitated the identification of a new generation of anti-mitotic therapies that target proteins with specific functions in mitosis. The exquisite selectivity for mitosis and the distinct ways in which these new agents interfere with mitosis provides the potential to not only overcome certain limitations of current tubulin-targeted anti-mitotic drugs, but to expand the scope of clinical efficacy that those drugs have established. The development of these new anti-mitotic drugs as targeted therapies faces significant challenges; nevertheless, these potential therapies also serve as unique tools to dissect the molecular mechanisms of the mitotic-checkpoint response.

Akt kinases 1, 2, and 3 are important regulators of cell survival and have been shown to be constitutively active in a variety of human tumors. GSK690693 is a novel ATP-competitive, low-nanomolar pan-Akt kinase inhibitor. It is selective for the Akt isoforms versus the majority of kinases in other families; however, it does inhibit additional members of the AGC kinase family. It causes dose-dependent reductions in the phosphorylation state of multiple proteins downstream of Akt, including GSK3B, PRAS40, and Forkhead. GSK690693 inhibited proliferation and induced apoptosis in a subset of tumor cells with potency consistent with intracellular inhibition of Akt kinase activity. In immune-compromised mice implanted with human BT474 breast carcinoma xenografts, a single i.p. administration of GSK690693 inhibited GSK3B phosphorylation in a dose-and time-dependent manner. After a single dose of GSK690693, >3 Mmol/L drug concentration in BT474 tumor xenografts correlated with a sustained decrease in GSK3B phosphorylation. Consistent with the role of Akt in insulin signaling, treatment with GSK690693 resulted in acute and transient increases in blood glucose level. Daily administration of GSK690693 produced significant antitumor activity in mice bearing established human SKOV-3 ovarian, LNCaP prostate, and BT474 and HCC-1954 breast carcinoma xenografts. Immunohistochemical analysis of tumor xenografts after repeat dosing with GSK690693 showed reductions in phosphorylated Akt substrates in vivo. These results support further evaluation of GSK690693 as an anticancer agent.

BackgroundColon cancer has been classically described by clinicopathologic features that permit the prediction of outcome only after surgical resection and staging.MethodsWe performed an unsupervised analysis of microarray data from 326 colon cancers to identify the first principal component (PC1) of the most variable set of genes. PC1 deciphered two primary, intrinsic molecular subtypes of colon cancer that predicted disease progression and recurrence.ResultsHere we report that the most dominant pattern of intrinsic gene expression in colon cancer (PC1) was tightly correlated (Pearson R = 0.92, P < 10-135) with the EMT signature-- both in gene identity and directionality. In a global micro-RNA screen, we further identified the most anti-correlated microRNA with PC1 as MiR200, known to regulate EMT.ConclusionsThese data demonstrate that the biology underpinning the native, molecular classification of human colon cancer--previously thought to be highly heterogeneous-- was clarified through the lens of comprehensive transcriptome analysis.

Centromere-associated protein-E (CENP-E) is a kinetochore-associated mitotic kinesin that is thought to function as the key receptor responsible for mitotic checkpoint signal transduction after interaction with spindle microtubules. We have identified GSK923295, an allosteric inhibitor of CENP-E kinesin motor ATPase activity, and mapped the inhibitor binding site to a region similar to that bound by loop-5 inhibitors of the kinesin KSP/Eg5. Unlike these KSP inhibitors, which block release of ADP and destabilize motor-microtubule interaction, GSK923295 inhibited release of inorganic phosphate and stabilized CENP-E motor domain interaction with microtubules. Inhibition of CENP-E motor activity in cultured cells and tumor xenografts caused failure of metaphase chromosome alignment and induced mitotic arrest, indicating that tight binding of CENP-E to microtubules is insufficient to satisfy the mitotic checkpoint. Consistent with genetic studies in mice suggesting that decreased CENP-E function can have a tumor-suppressive effect, inhibition of CENP-E induced tumor cell apoptosis and tumor regression.entromere-associated protein-E (CENP-E; kinesin-7) is a kinetochore-associated kinesin motor protein with an essential and exclusive role in metaphase chromosome alignment and satisfaction of the mitotic checkpoint (1). CENP-E is a likely candidate to integrate the mechanics of kinetochore-microtubule interaction with the mitotic checkpoint signaling machinery responsible for restraining cell-cycle progression into anaphase. CENP-E is a large dimeric protein consisting of an N-terminal kinesin motor domain tethered to a globular C-terminal domain through an extended coiled-coil rod domain (2, 3). The C-terminal, noncatalytic region of CENP-E is not only sufficient to specify localization to kinetochores, but it also mediates interaction of CENP-E with the serine/threonine kinase BubR1, a key effector of mitotic checkpoint signaling that forms complexes with the checkpoint proteins Cdc20, Bub3, and Mad2 to inhibit the ubiquitin ligase activity of the anaphase promoting complex APC/C CDC20 (4-7). The combined interaction of CENP-E with microtubules and a key regulator of APC/C CDC20 has led to the hypothesis that CENP-E functions as the key kinetochore microtubule receptor responsible for silencing mitotic checkpoint signal transduction after capture of spindle microtubules. This hypothesis was further strengthened by the finding that CENP-E could stimulate the kinase activity of BubR1 in a microtubule-sensitive manner (8, 9). In vitro, the addition of CENP-E to BubR1 resulted in a stimulation of BubR1 kinase activity. The addition of microtubules suppressed this stimulatory activity, an effect thought to be mediated by the CENP-E kinesin motor domain. Although the importance of CENP-E interaction with BubR1 and the role of BubR1-mediated phosphorylation in mitotic checkpoint function remain unclear, CENP-E remains a prominent candidate to play a key role in mitotic checkpoint signal transduction.Depletion of CENP-E from ...