14-3-3 Proteins play important roles in a wide range of vital regulatory processes, including signal transduction, apoptosis, cell cycle progression and DNA replication. In mammalian cells, 7 14-3-3 isoforms (␤, ␥, ⑀, , , and ) have been identified and each of these seems to have distinct tissue localizations and isoform-specific functions. Previous studies have shown that 14-3-3 protein levels are higher in human lung cancers as compared to normal tissues. It is unclear, however, which of the 14-3-3 isoform(s) are overexpressed in these cancers. In our study, the levels of all seven 14-3-3 isoforms were examined by RT-PCR and Western blotting. We show that the message for only two isoforms, 14-3-3⑀ and , could be detected in normal tissues. In lung cancer biopsies, however, four isoforms, 14-3-3␤, ␥, , and , in addition to 14-3-3⑀ and , were present in abundance. The expression frequency of 14-3-3␤, ␥, and isoforms was 11, 10, 13 and 8 of the 14 biopsies examined, respectively. The data from immunohistochemical staining and Western blotting were consistent with the RT-PCR results. Given the prevalence of elevated 14-3-3 expression in human lung cancers we propose that these proteins may be involved in lung cancer tumorigenesis and that specific 14-3-3 proteins may be useful as markers for lung cancer diagnosis and targets for therapy.

Summary In Arabidopsis thaliana, the amino acid sequences of membrane-associated acyl-CoA-binding proteins ACBP1 and ACBP2 are highly-conserved. We have previously shown that in developing seeds, ACBP1 accumulates in the cotyledonary cells of embryos and ACBP1 was proposed to be involved in lipid transfer. We show here by immunolocalization using ACBP2-specific antibodies, that ACBP2 is also expressed in the embryos at various stages of seed development in Arabidopsis.Phenotypic analyses of acbp1 and acbp2 single mutants revealed that knockout of either ACBP1 or ACBP2 alone did not affect their life cycle since both single mutants exhibited normal growth and development similar to wild type. However, the acbp1acbp2 double mutant was embryo lethal and was also defective in callus induction.On lipid and acyl-CoA profiling analyses, siliques but not leaves of the acbp1 mutant were shown to accumulate galactolipid monogalactosyldiacylglycerol (MGDG) and 18:0-CoA but the levels of most polyunsaturated species of phospholipids such as phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS) had declined.Since recombinant ACBP1 and ACBP2 bind unsaturated PC and acyl-CoA esters in vitro, we propose that ACBP1 and ACBP2 are essential in lipid transfer during early embryogenesis in Arabidopsis.

Auroras (A and B) are oncogenic serine/threonine kinases that play key roles in the mitotic phase of the eukaryotic cell cycle. Analysis of the Leukemia Lymphoma Molecular Profiling Project (LLMPP) database indicates Aurora over-expression correlates with poor prognosis. A tissue microarray (TMA) composed of 20 paired mantle cell lymphoma (MCL) patients demonstrated >75% of patients had high levels Aurora expression. Aurora A and B were also found elevated in 13 aggressive B-NHL cell lines. MLN8237, an Aurora inhibitor induced G2/M arrest with polyploidy and abrogated Aurora A and histone-H3 phosphorylation. MLN8237 inhibited aggressive B-NHL cell proliferation at an IC50 of 10-50 nM and induced apoptosis in a dose- and time-dependent manner. Low dose combinations of MLN8237 + docetaxel enhanced apoptosis by ∼3-4-fold in cell culture compared to single agents respectively. A mouse xenograft model of MCL demonstrated that MLN8237 (10 or 30 mg/kg) or docetaxel (10 mg/kg) alone had modest anti-tumor activity. However, MLN8237 plus docetaxel demonstrated a statistically significant tumor growth inhibition and enhanced survival compared to single agent therapy. Together, our results suggest that MLN8237 plus docetaxel may represent a novel therapeutic strategy that could be evaluated in early phase trials in relapsed/refractory aggressive B-cell NHL.

The 14-3-3 proteins have a wide range of ligands and are involved in a variety of biological pathways. Importantly, 14-3-3 proteins are known to be overexpressed in some human lung cancers, suggesting that they may play a role in tumorigenesis. Here we examined 14-3-3 expression in several lung cancer-derived cell lines and found that four of the seven 14-3-3 isoforms, beta, epsilon, theta and zeta, were highly expressed in both lung cancer cell lines and normal lung fibroblasts. Two isoforms, sigma and gamma, were present only at very low levels. Immunoprecipitation data showed 14-3-3zeta could bind to CDC25C in irradiated A549 cells, and suppression of 14-3-3zeta in A549 cells with antisense resulted in a decrease in CDC25C localization in cytoplasm and CDC2 phosphorylation on Tyr15. As a consequence, CDC2 activity remained elevated which resulted in release from radiation-induced G(2)/M-phase arrest. Moreover, 16% 14-3-3zeta antisense-transfected cells underwent apoptosis when exposed to 10 Gy ionizing radiation. These data indicate that 14-3-3zeta is involved in G(2) checkpoint activation and that inhibition of 14-3-3 may be a useful approach to sensitize human lung cancers to ionizing radiation.

Bile acids, principally deoxycholic acid (DCA), have been implicated in the promotion of colon tumorigenesis in both animals and humans. Increasing evidence suggests that bile acids may exert their tumor promoting activity by modulating intracellular signaling and altering gene expression. In this study we have investigated the effect of bile acids on the tumor suppressor p53 using the human colon tumor cell line HCT116, which retains the wild-type p53 gene and functional p53 signaling in response to DNA damage. We found that exposure of the cells to elevated concentrations of DCA suppressed accumulation of p53 protein as well as p53 transactivation and impaired the p53 response of the cells to DNA damaging agents, such as ionizing radiation. Neither ursodeoxycholic acid, a putative chemopreventive agent, nor cholic acid, which is biologically inert, had any effect on p53 protein level and transactivation activity. Further examination revealed that instead of inhibition, DCA induced p53 mRNA in a dose-dependent manner, indicating that the inhibitory effect of DCA on p53 protein is mediated by a post-transcriptional mechanism. Both lactacystin, a specific inhibitor of the 26S proteasome, and leptomycin B, a specific inhibitor of the nuclear export protein CRM1, could block the effect that DCA had on p53 protein levels, suggesting that DCA suppressed p53 by stimulating the process of proteasome-mediated degradation of p53. Significantly, blocking extracellular signal-regulated kinase (ERK) signaling, but not protein kinase C (PKC), blunted suppression by DCA of p53 protein levels and transactivation activity, suggesting that DCA suppressed p53, in part, by stimulating the ERK signaling pathway. Both ERK and PKC signaling have been previously demonstrated to be stimulated by DCA. These results suggest a novel signaling mechanism of bile acids that may play an important role in colon tumor promotion mediated by bile acids.

Oncogenic conversion of the RET (rearranged during transfection) tyrosine kinase is associated with several cancers. A fragment-based chemical screen lead to the identification of a novel RET inhibitor, Pz-1. Modeling and kinetic analysis identified Pz-1 as a Type-II tyrosine kinase inhibitor, able to bind the DFG-out conformation of the kinase. Importantly, from a single-agent polypharmacology standpoint, Pz-1 was shown active on VEGFR2, which can block blood supply required for RET-stimulated growth. In cell based assays, 1.0 nM of Pz-1 strongly inhibited phosphorylation of all tested RET oncoproteins. At 1.0 mg/kg/day per os, Pz-1 abrogated formation of tumors induced by RET-mutant fibroblasts and blocked phosphorylation of both RET and VEGFR2 in tumor tissue. Pz-1 featured no detectable toxicity up to 100.0 mg/kg, which indicated a large therapeutic window. This study validates the effectiveness and usefulness of a medicinal chemistry polypharmacology approach to obtain an inhibitor capable of targeting multiple oncogenic pathways

Purpose Aurora A and B are oncogenic serine/threonine kinases that regulate mitosis. Over-expression of Auroras promotes resistance to microtubule targeted agents. We investigated mechanistic synergy by inhibiting the mitotic spindle apparatus in the presence of MLN8237 [M], an Aurora A inhibitor with either vincristine [MV] or docetaxel [MD] in aggressive B-NHL. The addition of rituximab [R] to MV or MD was evaluated for synthetic lethality. Experimental Design Aggressive B-NHL cell subtypes were evaluated in vitro and in vivo for target modulation and anti-NHL activity with single agents, doublets and triplets by analyzing cell proliferation, apoptosis, tumor growth, survival and mechanisms of response/relapse by gene expression profiling with protein validation. Results MV is synergistic while MD is additive for cell proliferation inhibition in B-NHL cell culture models. Addition of R to MV is superior to MD but both significantly induce apoptosis compared to doublet therapy. Mouse xenograft models of mantle cell lymphoma showed modest single agent activity for M, R, D and V with tumor growth inhibition (TGI) of ~10–15%. Of the doublets, MV caused tumor regression, while TGI was observed with MD (~55–60%) and MR (~25–50%) respectively. Although MV caused tumor regression, mice relapsed 20 days after stopping therapy. In contrast, MVR was curative, while MDR led to TGI of ~85%. PCNA, Aurora B, cyclin B1, cyclin D1 and Bcl-2 proteins of harvested tumors confirmed response and resistance to therapy. Conclusions Addition of R to MV is a novel therapeutic strategy for aggressive B-NHL and warrants clinical trial evaluation.

The 14-3-3 proteins are a family of highly conserved proteins that participate in a wide variety of cellular processes. Mounting evidence suggests that 14-3-3 proteins have a role in human cancers, however their role in tumorigenesis is unclear. Here we report that over-expression of 14-3-3 gamma protein in human lung cancer cell line H322 results in abnormal DNA replication and polyploidization. Cells that overexpress 14-3-3 gamma are resistant to microtubule inhibitors and can reenter the cell cycle in the absence of mitosis suggesting that elevated levels of 14-3-3 gamma may enable cells to bypass the mitotic checkpoint. Taken together, our data indicate that 14-3-3gamma may contribute to tumorigenesis by promoting genomic instability.