In vitro and in vivo characterization of a benzofuran derivative, a potential anticancer agent, as a novel Aurora B kinase inhibitor.

Aurora B is a serine/threonine kinase that has a key role in mitosis and is overexpressed in cancer cells. Aberrations in Aurora B are highly correlated with tumorigenesis and cancer development, so many studies have focused on the development of Aurora B kinase inhibitors. Based on one of our previous high-throughput screening studies, we identified lead compound S6, a small-molecule benzofuran derivative that binds Aurora B and inhibits its kinase activity in vitro. S6 also displayed high selectivity for Aurora B inhibition. The cytotoxicity of S6 was assessed against a panel of 21 cancer cell lines. The cervical cancer cell line HeLa, liver cancer cell line HepG2 and colon cancer cell line SW620 were the most sensitive to S6 treatment. We found that S6 decreased the proliferation and colony formation of these three cell lines and elevated their percentages of cells in the G2/M phase of the cell cycle. S6 also inhibited phospho-histone H3 on Ser 10, a natural biomarker of endogenous Aurora B activity. The growth suppression of liver cancer QGY-7401 xenograft tumors was observed in nude mice after S6 administration, and this effect was accompanied by the in vivo inhibition of phospho-histone H3 (Ser 10). Taken together, we conclude that targeting Aurora B with compound S6 may be a novel strategy for cancer treatment, and additional studies are warranted.

Optimized protein kinase Cθ (PKCθ) inhibitors reveal only modest anti-inflammatory efficacy in a rodent model of arthritis.

We previously demonstrated that selective inhibition of protein kinase Cθ (PKCθ) with triazinone 1 resulted in dose-dependent reduction of paw swelling in a mouse model of arthritis.1,2 However, a high concentration was required for efficacy, thus providing only a minimal safety window. Herein we describe a strategy to deliver safer compounds based on the hypothesis that optimization of potency in concert with good oral pharmacokinetic (PK) properties would enable in vivo efficacy at reduced exposures, resulting in an improved safety window. Ultimately, transformation of 1 yielded analogues that demonstrated excellent potency and PK properties and fully inhibited IL-2 production in an acute model. In spite of good exposure, twice-a-day treatment with 17l in the glucose-6-phosphate isomerase chronic in vivo mouse model of arthritis yielded only moderate efficacy. On the basis of the exposure achieved, we conclude that PKCθ inhibition alone is insufficient for complete efficacy in this rodent arthritis model.

Discovery of selective and orally bioavailable protein kinase Cθ (PKCθ) inhibitors from a fragment hit.

Protein kinase Cθ (PKCθ) regulates a key step in the activation of T cells. On the basis of its mechanism of action, inhibition of this kinase is hypothesized to serve as an effective therapy for autoimmune diseases such as rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and psoriasis. Herein, the discovery of a small molecule PKCθ inhibitor is described, starting from a fragment hit 1 and advancing to compound 41 through the use of structure-based drug design. Compound 41 demonstrates excellent in vitro activity, good oral pharmacokinetics, and efficacy in both an acute in vivo mechanistic model and a chronic in vivo disease model but suffers from tolerability issues upon chronic dosing.

A thienopyrimidine derivative induces growth inhibition and apoptosis in human cancer cell lines via inhibiting Aurora B kinase activity.

Aurora kinases play a key role in the regulation of mitosis and have been regarded as promising targets of cancer therapy. In this paper we describe a thienopyrimidine derivative (S7), a novel potent ATP-competitive hit inhibitor of Aurora B kinase screened through a HTS system, with the IC50 141.12 nM in the biochemical kinase activity assay. Human tumor cells treated with S7 showed dose-dependent inhibition of auto-phosphorylation of Aurora B on Thr232 and another widely-used marker specific for Aurora B kinase, the phosphorylation of Histone H3 (Ser 10), demonstrating endogenous Aurora B kinase activity were inhibited at cellular level. Moreover, S7 treatment induced proliferation inhibition, colony formation inhibition and apoptosis of human tumor cell lines in a dose- and time-dependent manner.

S39, a novel Aurora B kinase inhibitor, shows potent antineoplastic activity in human Hela cervical cancer cell line.

Aurora kinases, frequently detected to be over-expressing in human tumors, regulate many essential events during mitosis progression and have been regarded as potentially important targets for cancer therapy. S39 is a novel potent inhibitor of Aurora B kinase with the IC50 90.07 nM in the biochemical assay in an ATP competitive manner. S39 treatment on human tumor cells can inhibit the phosphorylation of Histone H3 (Ser10), a direct downstream substrate of Aurora B kinase, indicating S39 inhibits endogenous Aurora B kinase activity in cell-based level. Furthermore, S39 treatment blocks cell proliferation, inhibits colony formation and induces apoptosis in a wide range of human tumor cell lines. These results indicate that S39 is a potential lead compound to be an Aurora B inhibitor.

The dietary flavonoid luteolin inhibits Aurora B kinase activity and blocks proliferation of cancer cells.

In human, Aurora B is a chromosomal passenger protein that induces phosphorylation of histone and involves in spindle checkpoint and cytokinesis. Aberrant expression of Aurora B has been shown to correlate with genetic instability and carcinogenesis. In the past, Aurora B has been validated as a drug target by several studies. Here we report that the dietary flavonoid luteolin could inhibit recombinant Aurora B in radiometric activity assay (IC(50)=0.357 µM) and bind to Aurora B with a high affinity (K(D)=5.85 µM) measured by Biacore 3000. Dose-dependent down-regulation of phosphorylation on Ser10 of histone H3 was also observed in cancer cell lines after 24-h treatment, indicating that endogenous Aurora B activity was inhibited by luteolin. Furthermore, we evaluated the effects of luteolin on the survival of a panel of 23 cell lines, and found that luteolin blocked growth of HeLa cells and SW620 cells in an 8-day cell proliferation assay as well as in colony formation assay. Thus, we identified Aurora B as a novel direct target of luteolin, and our results demonstrated that targeting Aurora B by natural products may be a feasible strategy to develop low toxic anticancer agents.

Identification and characterization of human LYPD6, a new member of the Ly-6 superfamily.

The Ly-6 protein superfamily is usually identified as a group of proteins with a LU protein domain. LU domain is about 80 amino acids long and characterized by a conserved pattern of 10 cysteine residues. Here we report the cloning and characterization of a novel human LU domain containing gene, LYPD6, isolated from human testis cDNA library, and mapped to 2q23.1-23.2 by searching the UCSC genomic database. The LYPD6 cDNA sequence of 3,501 base pairs contains an open reading frame encoding 171 amino acids. Subcellular localization of LYPD6 demonstrated that the protein was localized in the cytoplasm when overexpressed in COS-7 cells. RT-PCR analysis showed that LYPD6 was widely expressed in human tissues and the expression levels in brain and heart were relatively high. Furthermore, the subsequent analysis based on reporter gene assays suggested that overexpression of LYPD6 in HEK 293T cells was able to suppress the transcriptional activities of AP1.

3-Hydroxyflavone inhibits endogenous Aurora B and induces growth inhibition of cancer cell line.

The Aurora kinases play a critical role in mitosis and have been suggested as promising targets for cancer therapy due to their frequent overexpression in a variety of tumors. Compared with established inhibitors of cell division such as the anti-tubulins, novel agents target mitotic enzymes and show similar efficacy but with fewer side effects. Several small-molecule inhibitors of Aurora kinases have been developed as anticancer agents, some of which have progressed to early clinical evaluation. Here we identified 3-hydroxyflavone as a novel Aurora B inhibitor through high throughput screening. 3-Hydroxyflavone showed potent inhibition to Aurora B with the IC(50) on a nanomolar basis in the enzyme-based kinase activity assay. In the cell-based western blotting analysis, 3-hydroxyflavone dramatically decreased the phosphorylation level of Histone H3 on the site of serine 10, demonstrating the potent endogenous Aurora B activity inhibition in cell level. The followed cell image analysis provided the consist result. To make it clear whether 3-hydroxyflavone inhibited Aurora B by direct binding or not, SPR analysis was carried out to measure the affinity of interaction between Aurora B protein and 3-hydroxyflavone and the result proved the binding with high affinity. Usually Aurora activity suppression induced cancer cell proliferation inhibition. Colony formation and cell viability with/without treatment of 3-hydroxyflavone were measured using CCK-8. The growth suppression under 3-hydroxyflavone present and the growth recovery after being released gave strong evidence that presence of 3-hydroxyflavone efficiently inhibited the fast growth of cancer cells.

Cloning and characterization of a human LYPD7, a new member of the Ly-6 superfamily.

Members of the Ly-6 (Lymphocyte Antigen 6) protein family share one or several repeat units of the LU domain that is defined by a distinct disulfide bonding pattern between 8 or 10 cysteine residues. Here we report the cloning and characterization of a novel human LU domain-containing gene, LYPD7 (LY6/PLAUR domain containing 7), isolated from human testis cDNA library, and mapped to 2q22.3-23.3 by searching the UCSC genomic database. The LYPD7 cDNA sequence consists of 1,600 nucleotides and contains an open reading frame of 624 bp, encoding a putative protein of 207 amino acid residues. RT-PCR analysis showed that LYPD7 was especially highly expressed in testis, lung, stomach, and prostate. Subcellular localization of LYPD7 demonstrated that the protein was localized in the cytoplasm when overexpressed in Hela cells. Furthermore, the subsequent analysis based on reporter gene assays suggested that overexpression of LYPD7 in HEK 293T cells was able to activate the transcriptional activities of AP1 (PMA).

Cloning and characterization of a human GDPD domain-containing protein GDPD5.

Glycerophosphodiester phosphodiesterase (GDPD) catalyzes the hydrolysis of deacylated glycerophospholipids to glycerol phosphate and alcohol. GDPD5 has been reported in Mus musculus and Gallus gallus, but not in Homo sapiens. Here we report the cloning and characterization of a novel human GDPD domain-containing gene, GDPD5, isolated from human testis cDNA library, and mapped to 11q13.4-13.5 by searching the UCSC genomic database. The GDPD5 cDNA sequence of 3442 base pairs contains an open reading frame encoding 605 amino acids. The GDPD5 gene consists of 17 exons and encodes a putative protein with six transmembrane regions and a GDPD motif. Subcellular localization of GDPD5 demonstrated that the protein was localized in the cytoplasm when overexpressed in COS-7 cells. RT-PCR analysis showed that GDPD5 was widely expressed in human tissues and the expression levels in kidney and prostate were relatively low.

Identification of a novel human zinc finger gene, ZNF438, with transcription inhibition activity.

There were many different families of zinc finger proteins that contained multiple cysteine and/or histidine residues and used zinc to stabilize their folds. The classical C2H2 zinc finger proteins were the founding members of this superfamily and were among the most abundant proteins in eukaryotic genomes. C2H2 proteins typically contained several C2H2 fingers that made tandem contacts along the DNA. Here we reported a novel C2H2 type zinc finger gene, ZNF438, which encoded 828 amino acids that formed five zinc finger domains. Bioinformatics analysis revealed that the ZNF438 was mapped to human chromosome 10p11.2 and shared 62% identity with rat and mouse homologues. RT-PCR analysis indicated that it was ubiquitously expressed in 18 human adult tissues. With immunofluorescence assay, it was shown that the exogenous Flag-tagged ZNF438 was located in nucleus of COS-7 cells. To further explore the function of ZNF438, we examined the transcriptional activity of ZNF438 protein by transfecting recombinant pM-ZNF438 into mammalian cells. The subsequent analysis based on the duel luciferase assay system showed that ZNF438 was a transcriptional repressor.

Septin1, a new interaction partner for human serine/threonine kinase aurora-B.

Several families of kinases work together to ensure the rate and precision of mitosis. Aurora-B is an important serine/threonine kinase required for chromosome segregation and cytokinesis. Identification of Aurora-B substrates will help to enhance our understanding of the molecular mechanism of mitosis. Through a yeast two-hybrid screen, we found a novel partner of Aurora-B, Septin1, belonging to a conserved family of GTPase proteins that localize to the cleavage furrow and are involved in cytokinesis. We confirmed this interaction using Co-immunoprecipitation experiments in mammalian cells and GST-pull-down analysis in vitro. Moreover, Aurora-B can phosphorylate Septin1 in vitro. We identified that Ser248, Ser307, and Ser315 are the main phosphorylation sites in Septin1. These two proteins partially co-localize to the midbody during cytokinesis. So, it is possible that Septin1's role in the regulation of cytokinesis is related to its phosphorylation by Aurora-B. Unlike previous reports that Septins function in cytokinesis and localize to the cleavage furrow, we found that Septin1 localizes to the spindle pole throughout mitosis, indicating that Septin1 may function in chromosome segregation as well.