The Bcr-Abl tyrosine kinase oncogene causes chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). We describe a novel selective inhibitor ...of Bcr-Abl, AMN107 (IC
50 < 30 nM), which is significantly more potent than imatinib, and active against a number of imatinib-resistant Bcr-Abl mutants. Crystallographic analysis of Abl-AMN107 complexes provides a structural explanation for the differential activity of AMN107 and imatinib against imatinib-resistant Bcr-Abl. Consistent with its in vitro and pharmacokinetic profile, AMN107 prolonged survival of mice injected with Bcr-Abl-transformed hematopoietic cell lines or primary marrow cells, and prolonged survival in imatinib-resistant CML mouse models. AMN107 is a promising new inhibitor for the therapy of CML and Ph+ ALL.
This study investigates spatial patterns in glacier characteristics and area changes at decadal scales in the eastern Himalaya – Nepal (Arun and Tamor basins), India (Teesta basin in Sikkim) and ...parts of China and Bhutan – based on various satellite imagery: Corona KH4 imagery, Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Advanced Spaceborne Thermal Emission Radiometer (ASTER), QuickBird (QB) and WorldView-2 (WV2). We compare and contrast glacier surface area changes over the period of 1962–2000/2006 and their dependency on glacier topography (elevation, slope, aspect, percent debris cover) and climate (solar radiation, precipitation) on the eastern side of the topographic barrier (Sikkim) versus the western side (Nepal). Glacier mapping from 2000 Landsat ASTER yielded 1463 ± 88 km2 total glacierized area, of which 569 ± 34 km2 was located in Sikkim and 488 ± 29 km2 in eastern Nepal. Supraglacial debris covered 11% of the total glacierized area, and supraglacial lakes covered about 5.8% of the debris-covered glacier area alone. Glacier area loss (1962 to 2000) was 0.50 ± 0.2% yr−1, with little difference between Nepal (0.53 ± 0.2% yr−1) and Sikkim (0.44 ± 0.2% yr−1. Glacier area change was controlled mostly by glacier area, elevation, altitudinal range and, to a smaller extent, slope and aspect. In the Kanchenjunga–Sikkim area, we estimated a glacier area loss of 0.23 ± 0.08% yr−1 from 1962 to 2006 based on high-resolution imagery. On a glacier-by-glacier basis, clean glaciers exhibit more area loss on average from 1962 to 2006 (34%) compared to debris-covered glaciers (22%). Glaciers in this region of the Himalaya are shrinking at similar rates to those reported for the last decades in other parts of the Himalaya, but individual glacier rates of change vary across the study area with respect to local topography, percent debris cover or glacier elevations.
The efficacy and side-effects of drugs do not just reflect the biochemical and pharmacodynamic properties of the parent compound, but often comprise of cooperative effects between the properties of ...the parent and active metabolites. Metabolites of imatinib, nilotinib and midostaurin have been synthesised and evaluated in assays to compare their properties as protein kinase inhibitors with the parent drugs. The
-desmethyl-metabolite of imatinib is substantially less active than imatinib as a BCR-ABL1 kinase inhibitor, thus providing an explanation as to why patients producing high levels of this metabolite show a relatively low response rate in chronic myeloid leukaemia (CML) treatment. The hydroxymethylphenyl and
-oxide metabolites of imatinib and nilotinib are only weakly active as BCR-ABL1 inhibitors and are unlikely to play a role in the efficacy of either drug in CML. The 3-(
)-HO-metabolite of midostaurin shows appreciable accumulation following chronic drug administration and, in addition to mutant forms of FLT3, potently inhibits the PDPK1 and VEGFR2 kinases (IC
values <100 nM), suggesting that it might contribute to drug efficacy in acute myeloid leukaemia patients. The case studies discussed here provide further examples of how the synthesis and characterisation of metabolites can make important contributions to understanding the clinical efficacy of drugs.
The millions of protein sequences generated by genomics are expected to transform protein engineering and personalized medicine. To achieve these goals, tools for predicting outcomes of amino acid ...changes must be improved. Currently, advances are hampered by insufficient experimental data about nonconserved amino acid positions. Since the property "nonconserved" is identified using a sequence alignment, we designed experiments to recapitulate that context: Mutagenesis and functional characterization was carried out in 15 LacI/GalR homologs (rows) at 12 nonconserved positions (columns). Multiple substitutions were made at each position, to reveal how various amino acids of a nonconserved column were tolerated in each protein row. Results showed that amino acid preferences of nonconserved positions were highly context-dependent, had few correlations with physico-chemical similarities, and were not predictable from their occurrence in natural LacI/GalR sequences. Further, unlike the "toggle switch" behaviors of conserved positions, substitutions at nonconserved positions could be rank-ordered to show a "rheostatic", progressive effect on function that spanned several orders of magnitude. Comparisons to various sequence analyses suggested that conserved and strongly co-evolving positions act as functional toggles, whereas other important, nonconserved positions serve as rheostats for modifying protein function. Both the presence of rheostat positions and the sequence analysis strategy appear to be generalizable to other protein families and should be considered when engineering protein modifications or predicting the impact of protein polymorphisms.
Imatinib, a Bcr-Abl tyrosine kinase inhibitor, is a highly effective therapy for patients with chronic myelogenous leukemia (CML). Despite durable responses in most chronic phase patients, relapses ...have been observed and are much more prevalent in patients with advanced disease. The most common mechanism of acquired imatinib resistance has been traced to Bcr-Abl kinase domain mutations with decreased imatinib sensitivity. Thus, alternate Bcr-Abl kinase inhibitors that have activity against imatinib-resistant mutants would be useful for patients who relapse on imatinib therapy. Two such Bcr-Abl inhibitors are currently being evaluated in clinical trials: the improved potency, selective Abl inhibitor AMN107 and the highly potent dual Src/Abl inhibitor BMS-354825. In the current article, we compared imatinib, AMN107, and BMS-354825 in cellular and biochemical assays against a panel of 16 kinase domain mutants representing >90% of clinical isolates. We report that AMN107 and BMS-354825 are 20-fold and 325-fold more potent than imatinib against cells expressing wild-type Bcr-Abl and that similar improvements are maintained for all imatinib-resistant mutants tested, with the exception of T315I. Thus, both inhibitors hold promise for treating imatinib-refractory CML.
Hepatocellular carcinoma (HCC) is the most common hepatic malignancy and the third leading cause of cancer related deaths. Previous studies have implicated bile acids in pathogenesis of HCC, but the ...mechanisms are not known. We investigated the mechanisms of HCC tumor promotion by bile acids the diethylnitrosamine (DEN)-initiation-cholic acid (CA)-induced tumor promotion protocol in mice. The data show that 0.2% CA treatment resulted in threefold increase in number and size of DEN-induced liver tumors. All tumors observed in DEN-treated mice were well-differentiated HCCs. The HCCs observed in DEN-treated CA-fed mice exhibited extensive CD3-, CD20-, and CD45-positive inflammatory cell aggregates. Microarray-based global gene expression studies combined with Ingenuity Pathway Analysis revealed significant activation of NF-κB and Nanog in the DEN-treated 0.2% CA-fed livers. Further studies showed significantly higher TNF-α and IL-1β mRNA, a marked increase in total and phosphorylated-p65 and phosphorylated IκBα (degradation form) in livers of DEN-treated 0.2% CA-fed mice. Treatment of primary mouse hepatocytes with various bile acids showed significant induction of stemness genes including Nanog, KLF4, Sox2, and Oct4. Quantification of total and 20 specific bile acids in liver, and serum revealed a tumor-associated bile acid signature. Finally, quantification of total serum bile acids in normal, cirrhotic, and HCC human samples revealed increased bile acids in serum of cirrhotic and HCC patients. Taken together, these data indicate that bile acids are mechanistically involved pathogenesis of HCC and may promote HCC formation via activation of inflammatory signaling.
Abstract
Overdose of acetaminophen (APAP) is the major cause of acute liver failure (ALF) in the Western world with very limited treatment options. Previous studies from our groups and others have ...shown that timely activation of liver regeneration is a critical determinant of transplant-free survival of APAP-induced ALF patients. Here, we report that hepatocyte-specific deletion of Yes-associated protein (Yap), the downstream mediator of the Hippo Kinase signaling pathway results in faster recovery from APAP-induced acute liver injury. Initial studies performed with male C57BL/6J mice showed a rapid activation of Yap and its target genes within first 24 h after APAP administration. Treatment of hepatocyte-specific Yap knockout (Yap-KO) mice with 300 mg/kg APAP resulted in equal initial liver injury but a significantly accelerated recovery in Yap-KO mice. The recovery was accompanied by significantly rapid hepatocyte proliferation supported by faster activation of Wnt/β-catenin pathway. Furthermore, Yap-KO mice had significantly earlier and higher pro-regenerative inflammatory response following APAP overdose. Global gene expression analysis indicated that Yap-KO mice had a robust activation of transcription factors involved in response to endoplasmic reticulum stress (XBP1) and maintaining hepatocyte differentiation (HNF4α). In conclusion, these data indicate that inhibition of Yap in hepatocytes results in rapid recovery from APAP overdose due to an earlier activation of liver regeneration.
Heterogeneous semiconductor photoredox catalysis (SCPC), particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can ...either (i) interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii) interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C-N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.
Imatinib, nilotinib and dasatinib are protein kinase inhibitors which target the tyrosine kinase activity of the Breakpoint Cluster Region-Abelson kinase (BCR-ABL) and are used to treat chronic ...myelogenous leukemia. Recently, using a chemical proteomics approach another tyrosine kinase, the collagen receptor Discoidin Domain Receptor1 (DDR1) has also been identified as a potential target of these compounds. To further investigate the interaction of imatinib, nilotinib and dasatinib with DDR1 kinase we cloned and expressed human DDR1 and developed biochemical and cellular functional assays to assess their activity against DDR1 and the related receptor tyrosine kinase Discoidin Domain Receptor2 (DDR2). Our studies demonstrate that all 3 compounds are potent inhibitors of the kinase activity of both DDR1 and DDR2. In order to investigate the question of selectivity among DDR1, DDR2 and other tyrosine kinases we have aligned DDR1 and DDR2 protein sequences to other closely related members of the receptor tyrosine kinase family such as Muscle Specific Kinase (MUSK), insulin receptor (INSR), Abelson kinase (c-ABL), and the stem cell factor receptor (c-KIT) and have built homology models for the DDR1 and DDR2 kinase domains. In spite of high similarity among these kinases we show that there are differences within the ATP–phosphate binding loop (P-loop), which could be exploited to obtain kinase selective compounds. Furthermore, the potent DDR1 and DDR2 inhibitory activity of imatinib, nilotinib and dasatinib may have therapeutic implications in a number of inflammatory, fibrotic and neoplastic diseases.
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