Huangqi Guizhi Wuwu Decoction attenuates Podocyte cytoskeletal protein damage in IgA nephropathy rats by regulating AT1R/Nephrin/c-Abl pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Huangqi Guizhi Wuwu Decoction(HQGZWWD) is a Traditional Chinese Medicine formula from Synopsis of Golden Chamber used to treat blood arthralgia. According to the principle that the same treatment can be used for different diseases, HQGZWWD has proven effective for IgA nephropathy (IgAN) associated with spleen and kidney yang deficiency. AIM OF THE STUDY: In this study, we investigated the mechanism by which HQGZWWD alleviates proteinuria and protects renal function in rats with IgAN by regulating the AT1R/Nephrin/c-Abl pathway. METHODS: Rats were randomly divided into six groups: control, IgAN model, IgAN model treated with low-dose HQGZWWD, IgAN model treated with medium-dose HQGZWWD, IgAN model treated with high-dose HQGZWWD, and IgAN model treated with valsartan. IgAN was induced using bovine γ-globulin. We evaluated the mediating effects of HQGZWWD on podocyte cytoskeletal proteins, the AT1R/Nephrin/c-Abl pathway, upstream tumor necrosis factor-α (TNF-α), and TNF-α receptor-1 (TNFR1). RESULTS: The IgAN rats displayed proteinuria, IgA deposition in the mesangial region, and podocyte cytoskeletal protein damage. The expression of TNF-α, TNFR1, AT1R, and c-Abl was increased in the IgAN rat kidney, whereas the expression of nephrin, podocin, ACTN4, and phosphorylated nephrin (p-nephrin) was reduced. HQGZWWD treatment significantly alleviated podocyte cytoskeletal protein damage in the IgAN rats, upregulated the expression of nephrin, podocin, and ACTN4, and the colocalized expression of F-actin and nephrin. This study demonstrates that HQGZWWD attenuates podocyte cytoskeletal protein damage by regulating the AT1R-nephrin- c-Abl pathway, upregulating the expression of p-nephrin, and downregulating the expression of AT1R and c-Abl. CONCLUSIONS: These results indicate that HQGZWWD attenuates podocyte cytoskeletal protein damage in IgAN rats by regulating the AT1R/Nephrin/c-Abl pathway, providing a potential therapeutic approach for IgAN.

Betulin, a Newly Characterized Compound in Acacia auriculiformis Bark, Is a Multi-Target Protein Kinase Inhibitor.

The purpose of this work is to investigate the protein kinase inhibitory activity of constituents from Acacia auriculiformis stem bark. Column chromatography and NMR spectroscopy were used to purify and characterize betulin from an ethyl acetate soluble fraction of acacia bark. Betulin, a known inducer of apoptosis, was screened against a panel of 16 disease-related protein kinases. Betulin was shown to inhibit Abelson murine leukemia viral oncogene homolog 1 (ABL1) kinase, casein kinase 1ε (CK1ε), glycogen synthase kinase 3α/ß (GSK-3 α/ß), Janus kinase 3 (JAK3), NIMA Related Kinase 6 (NEK6), and vascular endothelial growth factor receptor 2 kinase (VEGFR2) with activities in the micromolar range for each. The effect of betulin on the cell viability of doxorubicin-resistant K562R chronic myelogenous leukemia cells was then verified to investigate its putative use as an anti-cancer compound. Betulin was shown to modulate the mitogen-activated protein (MAP) kinase pathway, with activity similar to that of imatinib mesylate, a known ABL1 kinase inhibitor. The interaction of betulin and ABL1 was studied by molecular docking, revealing an interaction of the inhibitor with the ABL1 ATP binding pocket. Together, these data demonstrate that betulin is a multi-target inhibitor of protein kinases, an activity that can contribute to the anticancer properties of the natural compound and to potential treatments for leukemia.

DNA damage accumulates and responses are engaged in human ALS brain and spinal motor neurons and DNA repair is activatable in iPSC-derived motor neurons with SOD1 mutations.

DNA damage is implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). However, relationships between DNA damage accumulation, DNA damage response (DDR), and upper and lower motor neuron vulnerability in human ALS are unclear; furthermore, it is unknown whether epigenetic silencing of DNA repair pathways contributes to ALS pathogenesis. We tested the hypotheses that DNA damage accumulates in ALS motor neurons along with diminished DDR, and that DNA repair genes undergo hypermethylation. Human postmortem CNS tissue was obtained from ALS cases (N = 34) and age-matched controls without neurologic disease (N = 15). Compared to age-matched controls, abasic sites accumulated in genomic DNA of ALS motor cortex and laser capture microdissection-acquired spinal motor neurons but not in motor neuron mitochondrial DNA. By immunohistochemistry, DNA damage accumulated significantly in upper and lower motor neurons in ALS cases as single-stranded DNA and 8-hydroxy-deoxyguanosine (OHdG) compared to age-matched controls. Significant DDR was engaged in ALS motor neurons as evidenced by accumulation of c-Abl, nuclear BRCA1, and ATM activation. DNA damage and DDR were present in motor neurons at pre-attritional stages and throughout the somatodendritic attritional stages of neurodegeneration. Motor neurons with DNA damage were also positive for activated p53 and cleaved caspase-3. Gene-specific promoter DNA methylation pyrosequencing identified the DNA repair genes Ogg1, Apex1, Pnkp and Aptx as hypomethylated in ALS. In human induced-pluripotent stem cell (iPSC)-derived motor neurons with familial ALS SOD1 mutations, DNA repair capacity was similar to isogenic control motor neurons. Our results show that vulnerable neurons in human ALS accumulate DNA damage, and contrary to our hypothesis, strongly activate and mobilize response effectors and DNA repair genes. This DDR in ALS motor neurons involves recruitment of c-Abl and BRCA1 to the nucleus in vivo, and repair of DNA double-strand breaks in human ALS motor neurons with SOD1 mutations in cell culture.

Levo-tetrahydropalmatine Attenuates Neuron Apoptosis Induced by Cerebral Ischemia-Reperfusion Injury: Involvement of c-Abl Activation.

Ischemic stroke is one of the most dangerous acute diseases which causes death or deformity. Apoptosis has been shown to play an important role in the development and pathogenesis of cerebral ischemia-reperfusion injury (I/R injury), but the related mechanism is unclear. Levo-tetrahydropalmatine (L-THP), a bioactive ingredient extracted from the Chinese herb Corydalis, can penetrate the blood-brain barrier and exert various pharmacological effects on neural tissues. The present study examined the neuroprotective effect of L-THP on neuronal apoptosis induced by cerebral I/R injury. Results showed that pretreatment with L-THP (12.5, 25, and 50 mg/kg) improved neurological outcomes and reduced infarct volume and cerebral edema in comparison with the brains of the middle cerebral artery occlusion (MCAO) group. These findings provided evidence for the neuroprotective effects of L-THP against cerebral I/R injury. Furthermore, administration of L-THP enhanced the expression of Bcl-2 and attenuated the content of Bax, cleaved caspase-3, and PARP. L-THP could improve the reduction of NeuN-positive cells induced by I/R injury. These results suggested that L-THP could inhibit neuroapoptosis in cerebral ischemic rats. c-Abl was discovered as the critical protein responsible for neurocyte apoptosis; however, few data have been published on the relation between ischemic stroke and the expression of c-Abl. We found that both c-Abl expression and neuronal apoptosis were significantly increased in the MCAO group, while pretreatment with L-THP could ameliorate this effect. Therefore, we deduced that reduced c-Abl overexpression may play a role in the anti-apoptosis effect of L-THP after cerebral I/R injury. Thus, L-THP may provide a potential therapeutic approach for the treatment of ischemic stroke. Graphical Abstract ᅟ.

Simple and Sensitive Method for Determination of Protein Kinase Activity Based on Surface Charge Change of Peptide-Modified Gold Nanoparticles As Substrates.

Protein tyrosine kinases play a pivotal role in intracellular signal transduction pathways and oncogenic transformation. It is necessary to develop a simple, cost-effective, and sensitive kinase assay for study of protein kinases and discovery of kinase-target drugs. In this paper, we present a simple and sensitive method for homogeneous detection of protein kinase activity and screening of inhibitor by measuring surface charge change on the peptide-modified gold nanoparticles (GNPs) as kinase substrates. In this assay, Abl (Abelson murine leukemia viral oncogene) kinase was used as a model. In the presence of Abl kinase and ATP, the surface negative charge on GNPs significantly increases due to phosphorylation of the peptide-modified GNPs. The surface charge on the peptide-modified GNPs was measured by zeta potential analyzer. Under the optimum conditions, the zeta potential on the peptide-modified GNPs was linearly dependent on Abl kinase concentration, the linear range was from 1 to 40 nM and the detection limit was 1 nM. This method was used to evaluate the inhibition efficiency of inhibitors, and the obtained IC50 values were well in agreement with the results reported in the references. Furthermore, this method was successfully applied to determine Abl kinase activity in the cell lysates. Compared to current methods, this new method shows simplicity, short analysis time, high sensitivity, and will become a promising platform for kinase-related fundamental research and inhibitor screening.

Investigation of New Therapeutic Targets in Undifferentiated Endometrial Sarcoma.

BACKGROUND: Undifferentiated endometrial sarcoma (UES) is a very rare subtype of uterine sarcoma, which has no consensus on the treatment. We investigated the expression of potential new therapeutic targets in UES to improve its aggressive clinical course and poor survival outcome. METHODS: The immunohistochemical expressions of vascular endothelial growth factor (VEGF), c-KIT, c-ABL, platelet derived growth factor receptor (PDGFR), protein kinase B (AKT1), mammalian target of rapamycin, epidermal growth factor receptor (EGFR), human epidermal growth factor receptor (HER2), Wilms tumor (WT1), aromatase inhibitor (CYP19A1), and histone deacetylase (HDAC) series in 10 UES patients were assessed using tissue microarrays. RESULTS: Strongly positive immunoreactivities were observed for VEGF, AKT1, and HDAC2/7 in 8 (80.0%) tumors; for CYP19A1 and HDAC6 in 9 (90%) tumors; and for HDAC1/4/8 in 10 (100%) tumors. Strong expression of CYP19A1 and HDAC6 was associated with distant recurrence (p = 0.030, both), and expression of WT1 indicated a more advanced stage (p = 0.033). UES treated with adjuvant therapy showed better disease-free and overall survivals (both 0 vs. 33.3%, p = 0.003). CONCLUSION: VEGF, AKT1, CYP19A1, and the HDAC1/2/4/6/7/8 series show an especially high frequency of strong immunoreactivity in UES and can be considered potential therapeutic targets.

Differential and opposing effects of imatinib on LPS- and ventilator-induced lung injury.

Endothelial dysfunction underlies the pathophysiology of vascular disorders such as acute lung injury (ALI) syndromes. Recent work has identified the Abl family kinases (c-Abl and Arg) as important regulators of endothelial cell (EC) barrier function and suggests that their inhibition by currently available pharmaceutical agents such as imatinib may be EC protective. Here we describe novel and differential effects of imatinib in regulating lung pathophysiology in two clinically relevant experimental models of ALI. Imatinib attenuates endotoxin (LPS)-induced vascular leak and lung inflammation in mice but exacerbates these features in a mouse model of ventilator-induced lung injury (VILI). We next explored these discrepant observations in vitro through investigation of the roles for Abl kinases in cultured lung EC. Imatinib attenuates LPS-induced lung EC permeability, restores VE-cadherin junctions, and reduces inflammation by suppressing VCAM-1 expression and inflammatory cytokine (IL-8 and IL-6) secretion. Conversely, in EC exposed to pathological 18% cyclic stretch (CS) (in vitro model of VILI), imatinib decreases VE-cadherin expression, disrupts cell-cell junctions, and increases IL-8 levels. Downregulation of c-Abl expression with siRNA attenuates LPS-induced VCAM-1 expression, whereas specific reduction of Arg reduces VE-cadherin expression in 18% CS-challenged ECs to mimic the imatinib effects. In summary, imatinib exhibits pulmonary barrier-protective and anti-inflammatory effects in LPS-injured mice and lung EC; however, imatinib exacerbates VILI as well as dysfunction in 18% CS-EC. These findings identify the Abl family kinases as important modulators of EC function and potential therapeutic targets in lung injury syndromes.

Vitamin E dietary supplementation improves neurological symptoms and decreases c-Abl/p73 activation in Niemann-Pick C mice.

Niemann-Pick C (NPC) disease is a fatal neurodegenerative disorder characterized by the accumulation of free cholesterol in lysosomes. We have previously reported that oxidative stress is the main upstream stimulus activating the proapoptotic c-Abl/p73 pathway in NPC neurons. We have also observed accumulation of vitamin E in NPC lysosomes, which could lead to a potential decrease of its bioavailability. Our aim was to determine if dietary vitamin E supplementation could improve NPC disease in mice. NPC mice received an alpha-tocopherol (α-TOH) supplemented diet and neurological symptoms, survival, Purkinje cell loss, α-TOH and nitrotyrosine levels, astrogliosis, and the c-Abl/p73 pathway functions were evaluated. In addition, the effect of α-TOH on the c-Abl/p73 pathway was evaluated in an in vitro NPC neuron model. The α-TOH rich diet delayed loss of weight, improved coordination and locomotor function and increased the survival of NPC mice. We found increased Purkinje neurons and α-TOH levels and reduced astrogliosis, nitrotyrosine and phosphorylated p73 in cerebellum. A decrease of c-Abl/p73 activation was also observed in the in vitro NPC neurons treated with α-TOH. In conclusion, our results show that vitamin E can delay neurodegeneration in NPC mice and suggest that its supplementation in the diet could be useful for the treatment of NPC patients.

Discovery of N-(3-((7H-purin-6-yl)thio)-4-hydroxynaphthalen-1-yl)-sulfonamide derivatives as novel protein kinase and angiogenesis inhibitors for the treatment of cancer: Synthesis and biological evaluation. Part III.

A novel series of N-(3-((7H-purin-6-yl)thio)-4-hydroxynaphthalen-1-yl)-sulfonamides were designed and synthesized. Biological characterization revealed that several compounds exerted enhanced anti-proliferative activity against human umbilical vein endothelial cells (HUVECs) and several cancer cell lines and high specific protein kinase and angiogenesis inhibitory activities. Compared with our previously synthesized compounds, the substitution of sulfonamide structure for amide fragment played an essential role for the advance of inhibitory activities. In addition, the replacement of 1H-1,2,4-triazole ring by 7H-purine did not result in obvious decrease of inhibition efficacy, indicating that the sulfonamide structure contributes even more to the inhibition efficacy than the 1H-1,2,4-triazole ring. Among these compounds, compound 9n demonstrated comparable in vitro antiangiogenic activities to pazopanib in both HUVEC tube formation assay and the rat thoracic aorta rings (TARs) test. Meanwhile, compound 9n was identified to inhibit Akt1 (IC50=1.73 µM) and Abl tyrosine kinase (IC50=1.53 µM) effectively.

c-ABL tyrosine kinase modulates p53-dependent p21 induction and ensuing cell fate decision in response to DNA damage.

The c-ABL non-receptor tyrosine kinase and the p53 tumor suppressor protein are pivotal modulators of cellular responses to DNA damage. However, a comprehensive understanding of the role of c-ABL kinase in p53-dependent transcription of p21(CIP1/WAF1) and ensuing cell fate decision is still obscure. Here, we demonstrate that c-ABL tyrosine kinase regulates p53-dependent induction of p21. As a result, it modulates cell fate decision by p53 in response to DNA damage differently according to the extent of DNA damage. When human cancer cells were treated with DNA damaging agent, adriamycin (0.08 µg/ml), p21 was induced following p53 induction. Owing largely to p21, a substantial fraction of cells treated with adriamycin were blocked at the G2 phase of the cell cycle and most cells eventually became senescent. When these cells were simultaneously treated with a c-ABL kinase inhibitor, STI571, or a c-ABL-specific siRNA along with adriamycin, the p53-dependent p21 induction was dramatically diminished, even though p53 is substantially induced. Accordingly, G2-arrest, and cellular senescence largely dependent on p21 were substantially abrogated. On the contrary, when cells were treated with a relatively high dose of adriamycin (0.4 µg/ml) cells became apoptotic, and the simultaneous presence of a c-ABL kinase inhibitor STI571 augmented the extent of apoptosis. We speculate this is due to abrogation of p53-dependent p21 induction, which leads to elimination of anti-apoptotic function of p21. In summary, c-ABL appears to promote senescence or inhibit apoptosis, depending on the extent of DNA damage. These findings suggest that the combined use of ABL kinase inhibitor and DNA damaging drug in chemotherapy against tumors retaining wild type p53 should be carefully designed.

Levels of target activation predict antifibrotic responses to tyrosine kinase inhibitors.

OBJECTIVES: To assess whether the discrepancy between the strong antifibrotic effects of tyrosine kinase inhibitors (TKIs) in animal models and the inconsistent results in clinical studies might be related to the activation levels of drug targets. METHODS: Skin sections of bleomycin, TSK1, Fra-2 transgenic mice, SSc patients and controls were analysed by histology and immunohistochemistry. Subgroups of mice were treated with the TKIs nilotinib or imatinib. Differences in the activation levels of the TKI targets p-PDGFRß (platelet derived growth factor ß) and p-c-abl were assessed. RESULTS: In bleomycin and TSK1 mice, expression of activated p-PDGFRß (platelet derived growth factor receptor ß) and p-c-abl was ubiquitous with strong upregulation compared with controls. Treatment with TKIs resulted in successful target inhibition and consequently reduced dermal fibrosis. In the Fra-2 model, the activation levels of p-PDGFRß and p-c-abl were much lower than in the bleomycin and the TSK1 models. Accordingly, nilotinib did not prevent dermal fibrosis and target inhibition was unsuccessful. Notably, in skin biopsies of SSc patients, the mean activation levels of TKI targets were only moderate and in the majority of patients resembled those of the non-responsive Fra-2 model. CONCLUSIONS: Animal models for proof-of-concept studies should be selected based on a similar activation level and expression pattern of drug targets as in human SSc.

Evaluating the predictivity of virtual screening for ABL kinase inhibitors to hinder drug resistance.

Virtual screening methods are now widely used in early stages of drug discovery, aiming to rank potential inhibitors. However, any practical ligand set (of active or inactive compounds) chosen for deriving new virtual screening approaches cannot fully represent all relevant chemical space for potential new compounds. In this study, we have taken a retrospective approach to evaluate virtual screening methods for the leukemia target kinase ABL1 and its drug-resistant mutant ABL1-T315I. 'Dual active' inhibitors against both targets were grouped together with inactive ligands chosen from different decoy sets and tested with virtual screening approaches with and without explicit use of target structures (docking). We show how various scoring functions and choice of inactive ligand sets influence overall and early enrichment of the libraries. Although ligand-based methods, for example principal component analyses of chemical properties, can distinguish some decoy sets from active compounds, the addition of target structural information via docking improves enrichment, and explicit consideration of multiple target conformations (i.e. types I and II) achieves best enrichment of active versus inactive ligands, even without assuming knowledge of the binding mode. We believe that this study can be extended to other therapeutically important kinases in prospective virtual screening studies.

Tyrosine-phosphorylated galectin-3 protein is resistant to prostate-specific antigen (PSA) cleavage.

Galectin-3 is a chimeric carbohydrate-binding protein, which interacts with cell surface carbohydrate-containing molecules and extracellular matrix glycoproteins and has been implicated in various biological processes such as cell growth, angiogenesis, motility, and metastasis. It is expressed in a wide range of tumor cells and is associated with tumor progression. The functions of galectin-3 are dependent on its localization and post-translational modifications such as cleavage and phosphorylation. Recently, we showed that galectin-3 Tyr-107 is phosphorylated by c-Abl; concomitantly, it was also shown that galectin-3 can be cleaved at this site by prostate-specific antigen (PSA), a chymotrypsin-like serine protease, after Tyr-107, resulting in loss of galectin-3 multivalency while preserving its carbohydrate binding activity. Galectin-3 is largely a monomer in solution but may form a homodimer by self-association through its carbohydrate recognition domain, whereas, in the presence of a ligand, galectin-3 polymerizes up to pentamers utilizing its N-terminal domain. Oligomerization is a unique feature of secreted galectin-3, which allows its function by forming ordered galectin-glycan structures, i.e. lattices, on the cell surface or through direct engagement of specific cell surface glycoconjugates by traditional ligand-receptor binding. We questioned whether Tyr-107 phosphorylation by c-Abl affects galectin-3 cleavage by PSA. The data suggest a role for galectin-3 in prostate cells associated with increased activity of c-Abl kinase and loss of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) activity. In addition, the ratio of phosphorylated/dephosphorylated galectin-3 might be used as a complementary value to that of PSA for prognosis of prostate cancer and a novel therapeutic target for the treatment of prostate cancer.

Exploration of (S)-3-aminopyrrolidine as a potentially interesting scaffold for discovery of novel Abl and PI3K dual inhibitors.

Based on the literature-reported compensatory effect of PI3K on Abl inhibition and the improved preclinical effect of drug combination of Abl and PI3K inhibitors, a series of compounds bearing novel scaffold of (S)-3-aminopyrrolidine was identified as Abl and PI3K dual inhibitors through support vector machine screening tool, which were subsequently synthesized and tested. Most compounds demonstrated promising cytoxicity against a CML leukemia cell-line K562 and moderate inhibition against Abl and PI3K kinases. These compounds induced no apoptosis in K562 cell-line, suggesting that their cytotoxic activities are unlikely duo to other known anti-CML mechanisms. Molecular docking study further showed that the compound 5k could bind with both Abl and PI3K, but the weaker binding with Abl compared to Imatinib is consistent with its low kinase inhibitory rates. These plus literature-reported evidences suggest that the promising cytotoxic effect of our novel compounds might be due to the collective effect of Abl and PI3K inhibition.

The tyrosine kinase c-Abl promotes proliferation and is expressed in atypical teratoid and malignant rhabdoid tumors.

BACKGROUND: Atypical teratoid/rhaboid tumors (AT/RTs) and extracranial malignant rhabdoid tumors are highly malignant neoplasms with a dismal prognosis. These tumors predominantly affect infants and targeted, adjuvant treatment approaches would be highly desirable. METHODS: In the current study, the authors investigated the expression and functional role of tyrosine kinases in 2 malignant rhabdoid tumor cell lines (A204 and G401) and in a series of 5 AT/RTs and 18 malignant rhabdoid tumors (13 rhabdoid tumors of the kidney and 5 extrarenal rhabdoid tumors). RESULTS: Both cell lines consistently expressed the tyrosine kinase c-Abl, which promoted proliferation as assessed by small interfering RNA knockdown. Blockage of c-Abl using the tyrosine kinase inhibitor imatinib resulted in reduced cellular growth in both cell lines. Furthermore, c-Abl was expressed in all rhabdoid tumors, whereas expression of platelet-derived growth factor receptor subtypes alpha and beta was infrequent and c-Kit expression was absent. CONCLUSIONS: The current data pointed toward a role for c-Abl in the biology of malignant rhabdoid tumors and provided a rationale for the investigation of tyrosine kinase inhibitors that target c-Abl for the treatment of these aggressive tumors.

Binding or bending: distinction of allosteric Abl kinase agonists from antagonists by an NMR-based conformational assay.

Allosteric inhibitors of Bcr-Abl have emerged as a novel therapeutic option for the treatment of CML. Using fragment-based screening, a search for novel Abl inhibitors that bind to the myristate pocket was carried out. Here we show that not all myristate ligands are functional inhibitors, but that the conformational state of C-terminal helix_I is a structural determinant for functional activity. We present an NMR-based conformational assay to monitor the conformation of this crucial helix_I and show that myristate ligands that bend helix_I are functional antagonists, whereas ligands that bind to the myristate pocket but do not induce this conformational change are kinase agonists. Activation of c-Abl by allosteric agonists has been confirmed in a biochemical assay.

Bosutinib: a dual SRC/ABL kinase inhibitor for the treatment of chronic myeloid leukemia.

The tyrosine kinase inhibitor imatinib mesylate (IM) set new standards in the treatment of chronic myeloid leukemia (CML). However, emergence of resistance to IM became a major therapeutic challenge. Bosutinib (SKI-606), a 7-alkoxy-3-quinolinecarbonitrile, functions as a dual inhibitor of SRC and ABL kinases, and preclinical studies demonstrated a high antiproliferative activity in human and murine CML cell lines. In ongoing Phase I/II clinical trials, bosutinib yielded promising results revealing high clinical efficacy, good tolerability and reduced toxicity in IM-resistant or -intolerant CML patients. In this article, we provide an overview on the mechanism of action, and the preclinical and currently available clinical data for bosutinib. Owing to its favorable toxicity profile and its high antileukemic activity, bosutinib is a promising novel treatment option for patients with CML. A recently initiated, randomized open-label Phase III clinical study will clarify its role in first-line therapy of Philadelphia chromosome-positive chronic-phase CML.

C-kit inhibition by imatinib mesylate attenuates progenitor cell expansion and inhibits liver tumor formation in mice.

BACKGROUND & AIMS: Numerous studies have linked the proliferation of liver progenitor cells (LPCs) during chronic liver disease to the risk for development of hepatocellular carcinoma. Thus, selective inhibition of LPC growth during preneoplastic injury may prevent or delay the onset of liver cancer. Rats carrying a germ-line mutation in c-kit have an impaired LPC response to liver injury. Therefore, we hypothesized that the c-kit inhibitor imatinib mesylate (IM) would suppress LPC growth and, therefore, may exert antitumorigenic effects in the liver. METHODS: Expression of IM target proteins was examined in chronically injured rodent and human livers. The effect of IM was examined in vitro using LPC lines and in vivo in mice fed a choline-deficient, ethionine-supplemented (CDE) diet. Livers were examined following short-term (up to 1 month) or long-term (up to 14 months) feeding of CDE diet and drug treatments. RESULTS: C-kit was significantly up-regulated in chronic injury and expressed by LPCs. IM was antiproliferative to LPC lines, and knockdown of c-kit reduced this response. IM treatment inhibited the LPCs response and early fibrogenesis induced by a short-term CDE diet. On the longer term, IM treatment reduced the extent of fibrosis and significantly inhibited tumor formation. CONCLUSIONS: Tyrosine kinase inhibitors, such as IM, may be suited for the prevention of hepatocellular carcinoma in the setting of chronic liver injury via antiproliferative effects on c-kit-expressing LPCs.

RNAi screen reveals an Abl kinase-dependent host cell pathway involved in Pseudomonas aeruginosa internalization.

Internalization of the pathogenic bacterium Pseudomonas aeruginosa by non-phagocytic cells is promoted by rearrangements of the actin cytoskeleton, but the host pathways usurped by this bacterium are not clearly understood. We used RNAi-mediated gene inactivation of approximately 80 genes known to regulate the actin cytoskeleton in Drosophila S2 cells to identify host molecules essential for entry of P. aeruginosa. This work revealed Abl tyrosine kinase, the adaptor protein Crk, the small GTPases Rac1 and Cdc42, and p21-activated kinase as components of a host signaling pathway that leads to internalization of P. aeruginosa. Using a variety of complementary approaches, we validated the role of this pathway in mammalian cells. Remarkably, ExoS and ExoT, type III secreted toxins of P. aeruginosa, target this pathway by interfering with GTPase function and, in the case of ExoT, by abrogating P. aeruginosa-induced Abl-dependent Crk phosphorylation. Altogether, this work reveals that P. aeruginosa utilizes the Abl pathway for entering host cells and reveals unexpected complexity by which the P. aeruginosa type III secretion system modulates this internalization pathway. Our results furthermore demonstrate the applicability of using RNAi screens to identify host signaling cascades usurped by microbial pathogens that may be potential targets for novel therapies directed against treatment of antibiotic-resistant infections.

Screening of drugs that suppress Ste11 MAPKKK activation in yeast identified a c-Abl tyrosine kinase inhibitor.

The yeast MAPKKK Ste11 activates three MAP kinase pathways, including pheromone signaling, osmosensing, and pseudohyphal/invasive growth pathways. We identified two chemical compounds, BTB03006 and GK03225, that suppress growth defects induced by Ste11 activation in diploid yeast cells. BTB03006, but not GK03225, was found to suppress growth defects induced by both alpha-factor and Ste4 G(beta) overexpression in the pheromone signaling pathway, suggesting that GK03225 is an osmosensing pathway-specific inhibitor. We also performed genome-wide suppressor analysis for Ste11 activation, using a yeast deletion strains collection, and identified PBS2 and HOG1, and several genes associated with chaperone functions, which represent potential target proteins of the drugs screened from Ste11 activation. GK03225 possesses an Iressa-like quinazoline ring structure, and its chemical analog, 11N-078, suppresses c-Abl human tyrosine kinase activity. These results suggest that drug screening in yeast can identify human tyrosine kinase inhibitors and other drugs for human diseases.