c-Abl is required for development and optimal cell proliferation in the context of p53 deficiency

Styrylquinazoline derivatives as ABL inhibitors selective for different DFG orientations

Among tyrosine kinase inhibitors, quinazoline-based compounds represent a large and well-known group of multi-target agents. Our previous studies have shown interesting kinases inhibition activity for a series of 4-aminostyrylquinazolines based on the CP-31398 scaffold. Here, we synthesised a new series of styrylquinazolines with a thioaryl moiety in the C4 position and evaluated in detail their biological activity. Our results showed high inhibition potential against non-receptor tyrosine kinases for several compounds. Molecular docking studies showed differential binding to the DFG conformational states of ABL kinase for two derivatives. The compounds showed sub-micromolar activity against leukaemia. Finally, in-depth cellular studies revealed the full landscape of the mechanism of action of the most active compounds. We conclude that S4-substituted styrylquinazolines can be considered as a promising scaffold for the development of multi-kinase inhibitors targeting a desired binding mode to kinases as effective anticancer drugs.

N-acylhydrazone derivative modulates cell cycle regulators promoting mitosis arrest and apoptosis in estrogen positive MCF-7 breast cancer cells

Breast cancer is the leading cause of cancer death among women worldwide. About 75% of all diagnosed cases are hormone-positive, which are treated with hormone therapy. However, many patients are refractory or become resistant to the drugs used in therapeutic protocols. In this scenario, it is essential to identify new substances with pharmacological potential against breast cancer. VEGFR2 inhibitors are considered promising antitumor agents not only due to their antiangiogenic activity but also by inhibiting the proliferation of tumor cells. Thus, the present study aimed to evaluate the effects of N-acylhydrazone derivative LASSBio-2029 on the proliferative behavior of MCF-7 cells. We observed a promising antitumor potential of this substance due to its ability to modulate critical cell cycle regulators including mitotic kinases (CDK1, AURKA, AURKB, and PLK1) and CDK inhibitor (CDKN1A). Increased frequencies of abnormal mitosis and apoptotic cells were observed in response to treatment. A molecular docking analysis predicts that LASSBio-2029 could bind to the proto-oncoprotein ABL1, which participates in cell cycle control, interacting with other controller proteins and regulating centrosome-associated tubulins. Finally, we created a gene signature with the downregulated genes, whose reduced expression is associated with a higher relapse-free survival probability in breast cancer patients.

Roles for c-Abl in postoperative neurodegeneration

The nonreceptor tyrosine kinase c-Abl is inactive under normal conditions. Upon activation, c-Abl regulates signaling pathways related to cytoskeletal reorganization. It plays a vital role in modulating cell protrusion, cell migration, morphogenesis, adhesion, endocytosis and phagocytosis. A large number of studies have also found that abnormally activated c-Abl plays an important role in a variety of pathologies, including various inflammatory diseases and neurodegenerative diseases. c-Abl also plays a crucial role in neurodevelopment and neurodegenerative diseases, mainly through mechanisms such as neuroinflammation, oxidative stress (OS), and Tau protein phosphorylation. Inhibiting expression or activity of this kinase has certain neuroprotective and anti-inflammatory effects and can also improve cognition and behavior. Blockers of this kinase may have good preventive and treatment effects on neurodegenerative diseases. Cognitive dysfunction after anesthesia is also closely related to the abovementioned mechanisms. We infer that alterations in the expression and activity of c-Abl may underlie postoperative cognitive dysfunction (POCD). This article summarizes the current understanding and research progress on the mechanisms by which c-Abl may be related to postoperative neurodegeneration.

Advances in small molecule therapy for treating metastatic thyroid cancer

INTRODUCTION

Multi kinase inhibitors (MKIs) are new drugs, which show activity against receptors of different growth factors leading to the inhibition of tumor cells growth and proliferation. This review summarizes a 10-year experience with the use of MKIs in thyroid cancer (TC). It focuses not only on sorafenib, lenvatinib, vandetanib and cabozantinib, already approved in TC, but also presents an overview of the results of different trials with distinct MKIs so far carried out in TC. Areas covered: Published results of phase I, II and III studies and other reports evaluated the efficacy of different targeted drugs in TC. Expert opinion: Despite numerous clinical trials with distinct MKIs, only four of them unequivocally demonstrated a beneficial effect on progression free survival in radioiodine refractory differentiated or medullary TC. In contrast to other solid tumors, we are still lacking in convincing evidences of their impact on overall survival. We still do not have any strong proof fulfilling evidence-based medicine criteria, when to start MKIs and which drug to use. The questions whether we really have to wait for disease progression in patients with a large tumor burden and/or aggressive types TC or when to stop MKIs treatment remain open.

Identification of informative genes and pathways using an improved penalized support vector machine with a weighting scheme

Incorporation of pathway knowledge into microarray analysis has brought better biological interpretation of the analysis outcome. However, most pathway data are manually curated without specific biological context. Non-informative genes could be included when the pathway data is used for analysis of context specific data like cancer microarray data. Therefore, efficient identification of informative genes is inevitable. Embedded methods like penalized classifiers have been used for microarray analysis due to their embedded gene selection. This paper proposes an improved penalized support vector machine with absolute t-test weighting scheme to identify informative genes and pathways. Experiments are done on four microarray data sets. The results are compared with previous methods using 10-fold cross validation in terms of accuracy, sensitivity, specificity and F-score. Our method shows consistent improvement over the previous methods and biological validation has been done to elucidate the relation of the selected genes and pathway with the phenotype under study.

Role of ABL family kinases in cancer: from leukaemia to solid tumours

The Abelson (ABL) family of nonreceptor tyrosine kinases, ABL1 and ABL2, transduces diverse extracellular signals to protein networks that control proliferation, survival, migration and invasion. ABL1 was first identified as an oncogene required for the development of leukaemias initiated by retroviruses or chromosome translocations. The demonstration that small-molecule ABL kinase inhibitors could effectively treat chronic myeloid leukaemia opened the door to the era of targeted cancer therapies. Recent reports have uncovered roles for ABL kinases in solid tumours. Enhanced ABL expression and activation in some solid tumours, together with altered cell polarity, invasion or growth induced by activated ABL kinases, suggest that drugs targeting these kinases may be useful for treating selected solid tumours.

c-Abl promotes osteoblast expansion by differentially regulating canonical and non-canonical BMP pathways and p16INK4a expression

Defects in stem cell renewal or progenitor cell expansion underlie ageing-related diseases such as osteoporosis. Yet much remains unclear about the mechanisms regulating progenitor expansion. Here we show that the tyrosine kinase c-Abl plays an important role in osteoprogenitor expansion. c-Abl interacts with and phosphorylates BMPRIA and the phosphorylation differentially influences the interaction of BMPRIA with BMPRII and the Tab1-Tak1 complex, leading to uneven activation of Smad1/5/8 and Erk1/2, the canonical and non-canonical BMP pathways that direct the expression of p16(INK4a). c-Abl deficiency shunts BMP signalling from Smad1/5/8 to Erk1/2, leading to p16(INK4a) upregulation and osteoblast senescence. Mouse genetic studies revealed that p16(INK4a) controls mesenchymal stem cell maintenance and osteoblast expansion and mediates the effects of c-Abl deficiency on osteoblast expansion and bone formation. These findings identify c-Abl as a regulator of BMP signalling pathways and uncover a role for c-Abl in p16(INK4a) expression and osteoprogenitor expansion.

A phase II study of imatinib in patients with advanced anaplastic thyroid cancer

BACKGROUND

Currently, there is no standard treatment for metastatic anaplastic thyroid cancer (ATC). DNA microarray analysis has shown platelet-dervived growth factor receptor (PDGFR) overexpression in ATC relative to well-differentiated thyroid cancer. In p53-mutated/deficient ATC cell lines, cABL is overexpressed, and selective inhibition of cABL results in a cytostatic effect. Imatinib inhibits tyrosine kinase activity of Bcr-ABL and PDGF. We hypothesize that patients with ATC that over-expresses PDGF receptors or cABL will respond to imatinib.

METHODS

Patients with histologically confirmed ATC who had measurable disease and whose disease expressed PDGF receptors by immunohistochemistry were eligible for study. Imatinib was administered at 400 mg orally twice daily without drug holiday. Response to treatment was assessed every 8 weeks. Patients with complete response, partial responses, or stable disease were treated until disease progression. The study was terminated early due to poor accrual.

RESULTS

From February 2004 to May 2007, 11 patients were enrolled and were started on imatinib. At baseline, 4/11 had locoregional disease, 5/11 had distant metastases, and 2/11 had both. Nine of 11 had prior chemoradiation, and 7/11 had thyroidectomy. Eight of 11 were evaluable for response; 4 were excluded for lack of follow-up with radiologic evaluation. The overall response rates at 8 weeks were complete response 0/8, partial response 2/8, and stable disease 4/8. The median time to follow-up was 26 months (ranges 23-30 months). The rate of 6-month progression-free survival was 36% (95% confidence interval, 9%-65%). The rate of 6-month overall survival was 45% (95% confidence interval, 16%-70%). The most common grade 3 toxicity was edema in 25%; other grade 3 toxicities included fatigue and hyponatremia (12.5% each). There were no grade 4 toxicities or treatment related deaths.

CONCLUSIONS

Imatinib appears to have activity in advanced ATC and is well tolerated. Due to difficulty of accruing patients with a rare malignancy at a single institution, further investigation of imatinib in ATC may be warranted in a multi-institutional setting.

MitoInteractome: mitochondrial protein interactome database, and its application in 'aging network' analysis

Background

Mitochondria play a vital role in the energy production and apoptotic process of eukaryotic cells. Proteins in the mitochondria are encoded by nuclear and mitochondrial genes. Owing to a large increase in the number of identified mitochondrial protein sequences and completed mitochondrial genomes, it has become necessary to provide a web-based database of mitochondrial protein information.

Results

We present 'MitoInteractome', a consolidated web-based portal containing a wealth of information on predicted protein-protein interactions, physico-chemical properties, polymorphism, and diseases related to the mitochondrial proteome. MitoInteractome contains 6,549 protein sequences which were extracted from the following databases: SwissProt, MitoP, MitoProteome, HPRD and Gene Ontology database. The first general mitochondrial interactome has been constructed based on the concept of 'homologous interaction' using PSIMAP (Protein Structural Interactome MAP) and PEIMAP (Protein Experimental Interactome MAP). Using the above mentioned methods, protein-protein interactions were predicted for 74 species. The mitochondrial protein interaction data of humans was used to construct a network for the aging process. Analysis of the 'aging network' gave us vital insights into the interactions among proteins that influence the aging process.

Conclusion

MitoInteractome is a comprehensive database that would (1) aid in increasing our understanding of the molecular functions and interaction networks of mitochondrial proteins, (2) help in identifying new target proteins for experimental research using predicted protein-protein interaction information, and (3) help in identifying biomarkers for diagnosis and new molecular targets for drug development related to mitochondria. MitoInteractome is available at http://mitointeractome.kobic.kr/.

The effects of c-Abl mutation on developing B cell differentiation and survival

c-Abl is a widely expressed Src family protein tyrosine kinase that is activated by chromosomal translocation in certain human leukemias. While shown in various experimental systems to regulate cell division and stress responses, its biological functions remain poorly understood. Although expressed at similar levels throughout B cell development, we found that the fraction of phosphorylated, active c-Abl peaks at the pro-B stage. We went on to perform a detailed analysis of B cell development in c-Abl-deficient mice. We confirmed a striking but variable decrease in pro- and pre-B cell numbers, a decrease in pre-B cell growth and an increase in pre-B cell apoptosis. This phenotype was not rescued by transgenic expression of a functional IgHC transgene and only partially rescued by the anti-apoptosis gene Bcl-x. Unlike their wild-type counterparts, c-Abl-deficient pre-B cells show a defect in Ca(2+) flux upon cross-linking of CD19, a co-receptor known to be involved in pre-B cell receptor signaling and failed to express CD25 on the cell surface. Despite these pre-B cell-signaling defects, selection for in-frame heavy-chain rearrangements was intact in the mutant mice. Remarkably, we were able to rescue the proliferative defect by culturing cells in vitro with large amounts of rIL-7. We conclude that c-Abl is required for normal B cell differentiation and survival.

Molecular-genetic insights in paediatric T-cell acute lymphoblastic leukaemia

Paediatric T-cell acute lymphoblastic leukaemia (T-ALL) is an aggressive malignancy of thymocytes that accounts for about 15% of ALL cases and for which treatment outcome remains inferior compared to B-lineage acute leukaemias. In T-ALL, leukemic transformation of maturating thymocytes is caused by a multistep pathogenesis involving numerous genetic abnormalities that drive normal T-cells into uncontrolled cell growth and clonal expansion. This review provides an overview of the current knowledge on onco- and tumor suppressor genes in T-ALL and suggests a classification of these genetic defects into type A and type B abnormalities. Type A abnormalities may delineate distinct molecular-cytogenetic T-ALL subgroups, whereas type B abnormalities are found in all major T-ALL subgroups and synergize with these type A mutations during T-cell pathogenesis.

Genetic studies of bone diseases: evidence for involvement of DNA damage response proteins in bone remodeling

Bone remodeling is carried out by bone marrow mesenchymal stem cell derived osteoblasts, which form the bones, and hematopoeitic stem cell derived osteoclasts, which absorb the bones. Their actions are coordinated in two ways: osteoblasts and their precursors synthesize and secrete cytokines such as RANKL and M-CSF to regulate osteoclastogenesis; bone resorption releases matrix associated TGF-β and BMPs to stimulate bone formation at the same sites. Recent studies on transgenic mouse models revealed that several proteins involved in the DNA damage response play important roles in bone remodeling. DNA damage response is triggered by double stranded DNA breaks, single stranded DNA breaks as well as other types of lesions, which recruit and activate Ser/Thr kinases such as Atm to the damaged sites, where Atm activates p53 to promote apoptosis, cell cycle arrest, and DNA repair. Atm also activates c-Abl, a non-receptor tyrosine kinase, to promote apoptosis. Studies from our and other laboratories have shown that c-Abl and Atm positively regulate osteoblast differentiation and bone formation and mice deficient for either of them show osteoporosis, whereas p53 negatively regulates osteoblast proliferation/differentiation and bone formation and the knockout mouse shows osteosclerosis. These three proteins have osteoblast autonomous effect without directly affecting osteoclast differentiation or resorption activity. Furthermore, they appear to regulate osteoblast differentiation through controlling the expression of osterix, an osteoblast specific transcription factor essential for osteoblast differentiation. These results establish a functional link between osteoblast differentiation and DNA damage response.

Recent advances in the treatment of salivary gland cancers: emphasis on molecular targeted therapy

Salivary gland cancers include tumors of different histologic characteristics and biological behavior. Radical surgery, followed or not by radiation therapy, represents the main treatment approach for this disease. The role of systemic chemotherapy is less clearly defined since trials of single-agent chemotherapy have consistently shown low response rates. Polychemotherapy is likely to induce a higher response rate, but does not improve survival. The determination of the molecular abnormalities underlying the different subtypes of salivary gland cancers might lead to more active targeted therapies. C-kit is overexpressed in a wide percentage of salivary gland carcinomas, but clinical trials with single-agent imatinib have been negative. ErbB1 and ErbB2 are also frequently overexpressed in salivary gland cancers and this has provided the rationale for clinical trials with trastuzumab, cetuximab, gefitinib, lapatinib. Finally, new pathways, such as vascular endothelial growth factor, might be worth targeting and clinical trials with anti-angiogenic agents are ongoing.

New molecular targeted therapies in thyroid cancer

Carcinoma of the thyroid gland is the most common malignancy of the endocrine system. Differentiated tumors are often curable with surgical resection and radioactive iodine. A small percentage of such patients, however, do not undergo remission and need new therapeutic approaches. Both anaplastic and medullary thyroid carcinomas exhibit aggressive behavior and are usually resistant to current therapeutic modalities. Thyroid carcinoma represents a fascinating model and a particularly promising paradigm for targeted therapy because some of the key oncogenic events are activating mutations of genes coding for tyrosine kinases, and these occur early in cancer development. A prototype is the RET proto-oncogene, a receptor tyrosine kinase, which is a key regulator of development and a 'hotspot' for oncogenic mutations. Mutations in the RET proto-oncogene have been identified as causative for papillary carcinoma and familial medullary thyroid carcinoma, making it an attractive target for selective inhibition in these subtypes. ZD 6474 has shown promising activity in preclinical models against RET kinase, and its contemporary inhibition of vascular endothelial growth factor and epidermal growth factor pathways renders it a very attractive drug for clinical trials in thyroid cancer. Activating point mutation of B-RAF can occur early in the development of papillary carcinoma. Moreover, papillary carcinomas with these mutations have more aggressive properties and are diagnosed more often at an advanced stage. Clinical evaluation of B-RAF-targeting drugs is undergoing and trials in thyroid cancer are planned. Agents that restore radioiodine uptake, such as histone deacetylase inhibitors and retinoids, represent another exciting field in new drug development in thyroid cancer.

p53 functions as a negative regulator of osteoblastogenesis, osteoblast-dependent osteoclastogenesis, and bone remodeling

p53 is a well known tumor suppressor. We show that p53 also regulates osteoblast differentiation, bone formation, and osteoblast-dependent osteoclast differentiation. Indeed, p53(-/-) mice display a high bone mass phenotype, and p53(-/-) osteoblasts show accelerated differentiation, secondary to an increase in expression of the osteoblast differentiation factor osterix, as a result. Reporter assays indicate that p53 represses osterix transcription by the minimal promoter in a DNA-binding-independent manner. In addition, p53(-/-) osteoblasts have an enhanced ability to favor osteoclast differentiation, in association with an increase in expression of macrophage-colony stimulating factor, which is under the control of osterix. Furthermore, inactivating p53 is sufficient to rescue the osteoblast differentiation defects observed in mice lacking c-Abl, a p53-interacting protein. Thus, these results identify p53 as a novel regulator of osteoblast differentiation, osteoblast-dependent osteoclastogenesis, and bone remodeling.

C-Abl as a modulator of p53

P53 is renowned as a cellular tumor suppressor poised to instigate remedial responses to various stress insults that threaten DNA integrity. P53 levels and activities are kept under tight regulation involving a complex network of activators and inhibitors, which determine the type and extent of p53 growth inhibitory signaling. Within this complexity, the p53-Mdm2 negative auto-regulatory loop serves as a major route through which intra- and extra-cellular stress signals are channeled to appropriate p53 responses. Mdm2 inhibits p53 transcriptional activities and through its E3 ligase activity promotes p53 proteasomal degradation either within the nucleus or following nuclear export. Upon exposure to stress signals these actions of Mdm2 have to be moderated, or even interrupted, in order to allow sufficient p53 to accumulate in an active form. Multiple mechanisms involving a variety of factors have been demonstrated to mediate this interruption. C-Abl is a critical factor that under physiological conditions is required for the maximal and efficient accumulation of active p53 in response to DNA damage. C-Abl protects p53 by antagonizing the inhibitory effect of Mdm2, an action that requires a direct interplay between c-Abl and Mdm2. In addition, c-Abl protects p53 from other inhibitors of p53, such as the HPV-E6/E6AP complex, that inhibits and degrades p53 in HPV-infected cells. Surprisingly, the oncogenic form of c-Abl, the Bcr-Abl fusion protein in CML cells, also promotes the accumulation of wt p53. However, in contrast to the activation of p53 by c-Abl, its oncogenic form, Bcr-Abl, counteracts the growth inhibitory activities of p53 by modulating the p53-Mdm2 loop. Thus, it appears that by modulating the p53-Mdm2 loop, c-Abl and its oncogenic forms critically determine the type and extent of the cellular response to DNA damage.

Loss of c-abl facilitates anchorage-independent growth of p53- and RB- deficient primary mouse embryonic fibroblasts

The c-abl tyrosine kinase is the proto-oncogene of the v-abl oncogene of the Abelson murine leukemia virus. Although mutational variants of c-Abl can exhibit gain of function and can produce a transformed phenotype, the function of c-Abl in transformation remained unclear. Here, we report that the loss of c-abl facilitates transformation. c-abl-knockout mouse embryonic fibroblasts (MEFs) immortalized by SV40 T antigen acquired anchorage-independent growth, and by constructing mutational variants of T antigen we showed that binding of large T antigen to p53 and RB was necessary to induce anchorage-independent growth. Although c-abl/p53 double-knockout MEFs did not undergo anchorage-independent growth, those expressing human papilloma virus 16 E7, which mainly inactivates RB, did. Our results show that the loss of c-abl facilitates anchorage-independent growth in the context of p53 and RB deficiency, and suggest that loss of function of c-abl facilitates some types of transformation.

Atm and c-Abl cooperate in the response to genotoxic stress during nervous system development

The c-Abl proto-oncogene is a target of the ATM kinase after DNA double strand breaks, although the physiological significance of these signaling events is not clear. Therefore, to delineate the roles of c-Abl and Atm during mouse development we generated mice with combinations of c-Abl and Atm mutant alleles. We found that dual inactivation of Atm and c-Abl usually resulted in midgestational lethality. However, mice with three mutant alleles, c-Abl(-/-)Atm(+/-) or c-Abl(+/-)Atm(-/-), were viable but predisposed to neuro-developmental abnormalities after genotoxic insult. Thus, these genetic data link Atm and c-Abl signaling and underscore a significant interrelationship between the two during neural development.

Gleevec inhibits beta-amyloid production but not Notch cleavage

Amyloid-beta (Abeta) peptides, consisting mainly of 40 and 42 aa (Abeta40 and Abeta42, respectively), are metabolites of the amyloid precursor protein and are believed to be major pathological determinants of Alzheimer's disease. The proteolytic cleavages that form the Abeta N and C termini are catalyzed by beta-secretase and gamma-secretase, respectively. Here we demonstrate that gamma-secretase generation of Abeta in an N2a cell-free system is ATP dependent. In addition, the Abl kinase inhibitor imatinib mesylate (Gleevec, or STI571), which targets the ATP-binding site of Abl and several other tyrosine kinases, potently reduces Abeta production in the N2a cell-free system and in intact N2a cells. Both STI571 and a related compound, inhibitor 2, also reduce Abeta production in rat primary neuronal cultures and in vivo in guinea pig brain. STI571 does not inhibit the gamma-secretase-catalyzed S3 cleavage of Notch-1. Furthermore, production of Abeta and its inhibition by STI571 were demonstrated to occur to similar extents in both Abl-/- and WT mouse fibroblasts, indicating that the effect of STI571 on Abeta production does not involve Abl kinase. The efficacy of STI571 in reducing Abeta without affecting Notch-1 cleavage may prove useful as a basis for developing novel therapies for Alzheimer's disease.

p53 activation results in rapid dephosphorylation of the eIF4E-binding protein 4E-BP1, inhibition of ribosomal protein S6 kinase and inhibition of translation initiation

p53 is an important regulator of cell cycle progression and apoptosis, and inactivation of p53 is associated with tumorigenesis. Although p53 exerts many of its effects through regulation of transcription, this protein is also found in association with ribosomes and several mRNAs have been identified that are translationally controlled in a p53-dependent manner. We have utilized murine erythroleukemic cells that express a temperature-sensitive p53 protein to determine whether p53 also functions at the level of translation. The data presented here demonstrate that p53 causes a rapid decrease in translation initiation. Analysis of several potential mechanisms for regulating protein synthesis shows that p53 has selective effects on the phosphorylation of the eIF4E-binding protein, 4E-BP1, and the activity of the p70 ribosomal protein S6 kinase. These data provide evidence that modulation of translational activity constitutes a further mechanism by which the growth inhibitory effects of p53 may be mediated.

Tyrosine kinase oncogenes in normal hematopoiesis and hematological disease

Tyrosine kinase oncogenes are formed as a result of mutations that induce constitutive kinase activity. Many of these tyrosine kinase oncogenes that are derived from genes, such as c-Abl, c-Fes, Flt3, c-Fms, c-Kit and PDGFRbeta, that are normally involved in the regulation of hematopoiesis or hematopoietic cell function. Despite differences in structure, normal function, and subcellular location, many of the tyrosine kinase oncogenes signal through the same pathways, and typically enhance proliferation and prolong viability. They represent excellent potential drug targets, and it is likely that additional mutations will be identified in other kinases, their immediate downstream targets, or in proteins regulating their function.