The Bcr-Abl tyrosine kinase inhibitor imatinib and promising new agents against Philadelphia chromosome-positive leukemias

Molecular biology of the novel anticancer medications: a focus on kinases inhibitors, biologics and CAR T-cell therapy

INTRODUCTION

Cancer treatment underwent significant changes in the last few years with the introduction of novel treatments targeting the immune system.

OBJECTIVES

The objective of this review is to discuss novel anticancer drugs including kinase inhibitors, biologics and cellular therapy with CAR-T cells.

METHODS

Most recent research articles were extracted from PubMed using keywords such as "kinases inhibitors", "CAR-T cell therapy".

RESULTS AND DISCUSSION

The number of kinase inhibitors is significantly increasing due to their demonstrated effectiveness in combination with biologics. CAR-T represented a major breakthrough in the field. Also, it focused on their mechanisms of action and the rational of their use either alone or in combination in relation to their modes of action.

Breaking paradigms: Long non-coding RNAs forming gene fusions with potential implications in cancer

Long non-coding RNAs (lncRNAs) are non-coding RNAs longer than 200 nucleotides with dynamic regulatory functions. They interact with a wide range of molecules such as DNA, RNA, and proteins to modulate diverse cellular functions through several mechanisms and, if deregulated, they can lead to cancer development and progression. Recently, it has been described that lncRNAs are susceptible to form gene fusions with mRNAs or other lncRNAs, breaking the paradigm of gene fusions consisting mainly of protein-coding genes. However, their biological significance in the tumor phenotype is still uncertain. Therefore, their recent identification opens a new line of research to study their biological role in tumorigenesis, and their potential as biomarkers with clinical relevance or as therapeutic targets. The present study aimed to review the lncRNA fusions identified so far and to know which of them have been associated with a potential function. We address the current challenges to deepen their study as well as the reasons why they represent a future therapeutic window in cancer.

Anti-breast cancer-induced cardiomyopathy: Mechanisms and future directions

With the progression of tumor treatment, the 5-year survival rate of breast cancer is close to 90%. Cardiovascular toxicity caused by chemotherapy has become a vital factor affecting the survival of patients with breast cancer. Anthracyclines, such as doxorubicin, are still some of the most effective chemotherapeutic agents, but their resulting cardiotoxicity is generally considered to be progressive and irreversible. In addition to anthracyclines, platinum- and alkyl-based antitumor drugs also demonstrate certain cardiotoxic effects. Targeted drugs have always been considered a relatively safe option. However, in recent years, some random clinical trials have observed the occurrence of subclinical cardiotoxicity in targeted antitumor drug users, which may be related to the effects of targeted drugs on the angiotensin converting enzyme, angiotensin receptor and β receptor. The use of angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and beta-blockers may prevent clinical cardiotoxicity. This article reviews the toxicity and mechanisms of current clinical anti-breast cancer drugs and proposes strategies for preventing cardiovascular toxicity to provide recommendations for the clinical prevention and treatment of chemotherapy-related cardiomyopathy.

Emerging Targeted Therapeutic Strategies to Overcome Imatinib Resistance of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common malignant mesenchymal neoplasms of the gastrointestinal tract. The gold standard for the diagnosis of GISTs is morphologic analysis with an immunohistochemical evaluation plus genomic profiling to assess the mutational status of lesions. The majority of GISTs are driven by gain-of-function mutations in the proto-oncogene c-KIT encoding the tyrosine kinase receptor (TKR) known as KIT and in the platelet-derived growth factor-alpha receptor (PDGFRA) genes. Approved therapeutics are orally available as tyrosine kinase inhibitors (TKIs) targeting KIT and/or PDGFRA oncogenic activation. Among these, imatinib has changed the management of patients with unresectable or metastatic GISTs, improving their survival time and delaying disease progression. Nevertheless, the majority of patients with GISTs experience disease progression after 2-3 years of imatinib therapy due to the development of secondary KIT mutations. Today, based on the identification of new driving oncogenic mutations, targeted therapy and precision medicine are regarded as the new frontiers for GISTs. This article reviews the most important mutations in GISTs and highlights their importance in the current understanding and treatment options of GISTs, with an emphasis on the most recent clinical trials.

Ketoconazole Reverses Imatinib Resistance in Human Chronic Myelogenous Leukemia K562 Cells

Chronic myeloid leukemia (CML) is a hematologic disorder characterized by the oncogene BCR-ABL1, which encodes an oncoprotein with tyrosine kinase activity. Imatinib, a BCR-ABL1 tyrosine kinase inhibitor, performs exceptionally well with minimal toxicity in CML chemotherapy. According to clinical trials, however, 20–30% of CML patients develop resistance to imatinib. Although the best studied resistance mechanisms are BCR-ABL1-dependent, P-glycoprotein (P-gp, a drug efflux transporter) may also contribute significantly. This study aimed to establish an imatinib-resistant human CML cell line, evaluate the role of P-gp in drug resistance, and assess the capacity of ketoconazole to reverse resistance by inhibiting P-gp. The following parameters were determined in both cell lines: cell viability (as the IC50) after exposure to imatinib and imatinib + ketoconazole, P-gp expression (by Western blot and immunofluorescence), the intracellular accumulation of a P-gp substrate (doxorubicin) by flow cytometry, and the percentage of apoptosis (by the Annexin method). In the highly resistant CML cell line obtained, P-gp was overexpressed, and the level of intracellular doxorubicin was low, representing high P-gp activity. Imatinib plus a non-toxic concentration of ketoconazole (10 μM) overcame drug resistance, inhibited P-gp overexpression and its efflux function, increased the intracellular accumulation of doxorubicin, and favored greater apoptosis of CML cells. P-gp contributes substantially to imatinib resistance in CML cells. Ketoconazole reversed CML cell resistance to imatinib by targeting P-gp-related pathways. The repurposing of ketoconazole for CML treatment will likely help patients resistant to imatinib.

A Path-Based Analysis of Infected Cell Line and COVID-19 Patient Transcriptome Reveals Novel Potential Targets and Drugs Against SARS-CoV-2

Most transcriptomic studies of SARS-CoV-2 infection have focused on differentially expressed genes, which do not necessarily reveal the genes mediating the transcriptomic changes. In contrast, exploiting curated biological network, our PathExt tool identifies central genes from the differentially active paths mediating global transcriptomic response. Here we apply PathExt to multiple cell line infection models of SARS-CoV-2 and other viruses, as well as to COVID-19 patient-derived PBMCs. The central genes mediating SARS-CoV-2 response in cell lines were uniquely enriched for ATP metabolic process, G1/S transition, leukocyte activation and migration. In contrast, PBMC response reveals dysregulated cell-cycle processes. In PBMC, the most frequently central genes are associated with COVID-19 severity. Importantly, relative to differential genes, PathExt-identified genes show greater concordance with several benchmark anti-COVID-19 target gene sets. We propose six novel anti-SARS-CoV-2 targets ADCY2, ADSL, OCRL, TIAM1, PBK, and BUB1, and potential drugs targeting these genes, such as Bemcentinib, Phthalocyanine, and Conivaptan.

Computational Design of Novel Allosteric Inhibitors for Plasmodium falciparum DegP

The serine protease, DegP exhibits proteolytic and chaperone activities, essential for cellular protein quality control and normal cell development in eukaryotes. The P. falciparum DegP is essential for the parasite survival and required to combat the oscillating thermal stress conditions during the infection, protein quality checks and protein homeostasis in the extra-cytoplasmic compartments, thereby establishing it as a potential target for drug development against malaria. Previous studies have shown that diisopropyl fluorophosphate (DFP) and the peptide SPMFKGV inhibit E. coli DegP protease activity. To identify novel potential inhibitors specific to PfDegP allosteric and the catalytic binding sites, we performed a high throughput in silico screening using Malaria Box, Pathogen Box, Maybridge library, ChEMBL library and the library of FDA approved compounds. The screening helped identify five best binders that showed high affinity to PfDegP allosteric (T0873, T2823, T2801, RJC02337, CD00811) and the catalytic binding site (T0078L, T1524, T2328, BTB11534 and 552691). Further, molecular dynamics simulation analysis revealed RJC02337, BTB11534 as the best hits forming a stable complex. WaterMap and electrostatic complementarity were used to evaluate the novel bio-isosteric chemotypes of RJC02337, that led to the identification of 231 chemotypes that exhibited better binding affinity. Further analysis of the top 5 chemotypes, based on better binding affinity, revealed that the addition of electron donors like nitrogen and sulphur to the side chains of butanoate group are more favoured than the backbone of butanoate group. In a nutshell, the present study helps identify novel, potent and Plasmodium specific inhibitors, using high throughput in silico screening and bio-isosteric replacement, which may be experimentally validated.

NGS-guided precision oncology in metastatic breast and gynecological cancer: first experiences at the CCC Munich LMU

Purpose

Comprehensive genomic profiling identifying actionable molecular alterations aims to enable personalized treatment for cancer patients. The purpose of this analysis was to retrospectively assess the impact of personalized recommendations made by a multidisciplinary tumor board (MTB) on the outcome of patients with breast or gynecological cancers, who had progressed under standard treatment. Here, first experiences of our Comprehensive Cancer Center Molecular Tumor Board are reported.

Methods

All patients were part of a prospective local registry. 95 patients diagnosed with metastatic breast cancer or gynecological malignancies underwent extended molecular profiling. From May 2017 through March 2019, the MTB reviewed all clinical cases considering tumor profile and evaluated molecular alterations regarding further diagnostic and therapeutic recommendations.

Results

95 patients with metastatic breast or gynecological cancers were discussed in the MTB (68% breast cancer, 20% ovarian cancer, 5% cervical cancer, 3% endometrial cancer and 4% others). Genes with highest mutation rate were PIK3CA and ERBB2. Overall, 34 patients (36%) received a biomarker-based targeted therapy recommendation. Therapeutic recommendations were implemented in nine cases; four patients experienced clinical benefit with a partial response or disease stabilization lasting over 4 months.

Conclusion

In the setting of a multidisciplinary molecular tumor board, a small but clinically meaningful group of breast and gynecological cancer patients benefits from comprehensive genomic profiling. Broad and successful implementation of precision medicine is complicated by patient referral at late stage disease and limited access to targeted agents and early clinical trials.

Trial registration number

284-10 (03.05.2018).

c-Abl Inhibition Activates TFEB and Promotes Cellular Clearance in a Lysosomal Disorder

The transcription factor EB (TFEB) has emerged as a master regulator of lysosomal biogenesis, exocytosis, and autophagy, promoting the clearance of substrates stored in cells. c-Abl is a tyrosine kinase that participates in cellular signaling in physiological and pathophysiological conditions. In this study, we explored the connection between c-Abl and TFEB. Here, we show that under pharmacological and genetic c-Abl inhibition, TFEB translocates into the nucleus promoting the expression of its target genes independently of its well-known regulator, mammalian target of rapamycin complex 1. Active c-Abl induces TFEB phosphorylation on tyrosine and the inhibition of this kinase promotes lysosomal biogenesis, autophagy, and exocytosis. c-Abl inhibition in Niemann-Pick type C (NPC) models, a neurodegenerative disease characterized by cholesterol accumulation in lysosomes, promotes a cholesterol-lowering effect in a TFEB-dependent manner. Thus, c-Abl is a TFEB regulator that mediates its tyrosine phosphorylation, and the inhibition of c-Abl activates TFEB promoting cholesterol clearance in NPC models.

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c-Abl is a TFEB regulator that mediates its tyr phosphorylation

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c-Abl inhibition promotes TFEB activity independently of mTORC1

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c-Abl inhibition reduces cholesterol accumulation in NPC1 models

Dominant Nucleolus in the Progenitor Cell Using Human Bone Marrow Erythroid and Granulocytic Cell Lineages as a Model. A Morphological and Cytochemical Note

Progenitor cells of the human erythroid and granulocytic cell lineages are characterized by the presence of several nucleoli. One of these nucleoli is larger and possesses more fibrillar centres than others. Such nucleolus is apparently dominant in respect of both size and main nucleolar function such as nucleolar-ribosomal RNA transcription. Such nucleolus is also visible in specimens using conventional visualization procedures, in contrast to smaller nucleoli. In the terminal differentiation nucleated stages of the erythroid and granulocytic development, dominant nucleoli apparently disappeared, since these cells mostly contained very small nucleoli of a similar size with one fibrillar centre. Thus, the easily visible dominant nucleoli appear to be useful markers of the progenitor cell state, such as proliferation, and differentiation potential.

Kinase-targeted cancer therapies: progress, challenges and future directions

The human genome encodes 538 protein kinases that transfer a γ-phosphate group from ATP to serine, threonine, or tyrosine residues. Many of these kinases are associated with human cancer initiation and progression. The recent development of small-molecule kinase inhibitors for the treatment of diverse types of cancer has proven successful in clinical therapy. Significantly, protein kinases are the second most targeted group of drug targets, after the G-protein-coupled receptors. Since the development of the first protein kinase inhibitor, in the early 1980s, 37 kinase inhibitors have received FDA approval for treatment of malignancies such as breast and lung cancer. Furthermore, about 150 kinase-targeted drugs are in clinical phase trials, and many kinase-specific inhibitors are in the preclinical stage of drug development. Nevertheless, many factors confound the clinical efficacy of these molecules. Specific tumor genetics, tumor microenvironment, drug resistance, and pharmacogenomics determine how useful a compound will be in the treatment of a given cancer. This review provides an overview of kinase-targeted drug discovery and development in relation to oncology and highlights the challenges and future potential for kinase-targeted cancer therapies.

Synergistic Induction of Apoptosis by Quercetin and Curcumin in Chronic Myeloid Leukemia (K562) Cells

Chronic myeloid leukemia is a major hematopoietic malignancy characterized by expansion of myeloid cells. In this study, we have investigated whether quercetin, curcumin and their combination induce apoptosis and inhibit growth of K562 cells. We have observed that quercetin and curcumin combination induced apoptosis accompanied by increased ROS and decreased GSH levels as well as loss of mitochondrial membrane potential. Our mRNA and protein expression results suggested that cytochrome c was released from mitochondria causing PARP and caspase-9 cleavages, the hallmarks of mitochondrial apoptotic pathway. We believe that triggering of apoptosis is mostly via mitochondrial pathway and ROS generation may induce impairment of mitochondrial membrane potential. The use of quercetin and curcumin combination potentiates individual apoptotic effects of the polyphenols and reduces their effective dose thereby preventing potential toxic effects on normal cells. Additional preclinical studies and clinical trials are certainly required to further validate their usefulness as potent anticancer agents.

A High-Throughput Method for Measuring Drug Residence Time Using the Transcreener ADP Assay

Analysis of drug-target residence times during drug development can result in improved efficacy, increased therapeutic window, and reduced side effects. Residence time can be estimated as the reciprocal of the dissociation rate ( k_off) of an inhibitor from its target. The traditional methods for measuring k_off require synthesis of labeled ligands or low-throughput label-free methods. To provide an alternative that is better suited to an automated high-throughput screening (HTS) environment, we adapted a classic "jump dilution" catalytic assay method for determination of k_off values for kinase inhibitor drugs. We used the Transcreener ADP² Kinase assay as a universal, homogenous method to monitor the recovery of kinase activity as the drugs dissociated from preformed inhibitor-kinase complexes. We measured residence times for several drugs that bind the epidermal growth factor receptor (EGFR), ABL1, and Aurora kinases and found that the rank ordering of inhibitor k_off values correlated with literature values determined using ligand binding assays. Moreover, very similar results were obtained using the Transcreener assay with fluorescence polarization (FP), fluorescence intensity (FI), and time-resolved Förster resonance energy transfer (TR-FRET) detection modes. This HTS-compatible, generic assay method should facilitate the use of residence time as a parameter for compound prioritization and optimization early in kinase drug discovery programs.

Excess cerebral TNF causing glutamate excitotoxicity rationalizes treatment of neurodegenerative diseases and neurogenic pain by anti-TNF agents

The basic mechanism of the major neurodegenerative diseases, including neurogenic pain, needs to be agreed upon before rational treatments can be determined, but this knowledge is still in a state of flux. Most have agreed for decades that these disease states, both infectious and non-infectious, share arguments incriminating excitotoxicity induced by excessive extracellular cerebral glutamate. Excess cerebral levels of tumor necrosis factor (TNF) are also documented in the same group of disease states. However, no agreement exists on overarching mechanism for the harmful effects of excess TNF, nor, indeed how extracellular cerebral glutamate reaches toxic levels in these conditions. Here, we link the two, collecting and arguing the evidence that, across the range of neurodegenerative diseases, excessive TNF harms the central nervous system largely through causing extracellular glutamate to accumulate to levels high enough to inhibit synaptic activity or kill neurons and therefore their associated synapses as well. TNF can be predicted from the broader literature to cause this glutamate accumulation not only by increasing glutamate production by enhancing glutaminase, but in addition simultaneously reducing glutamate clearance by inhibiting re-uptake proteins. We also discuss the effects of a TNF receptor biological fusion protein (etanercept) and the indirect anti-TNF agents dithio-thalidomides, nilotinab, and cannabinoids on these neurological conditions. The therapeutic effects of 6-diazo-5-oxo-norleucine, ceptriaxone, and riluzole, agents unrelated to TNF but which either inhibit glutaminase or enhance re-uptake proteins, but do not do both, as would anti-TNF agents, are also discussed in this context. By pointing to excess extracellular glutamate as the target, these arguments greatly strengthen the case, put now for many years, to test appropriately delivered ant-TNF agents to treat neurodegenerative diseases in randomly controlled trials.

Novel roles of Src in cancer cell epithelial-to-mesenchymal transition, vascular permeability, microinvasion and metastasis

The Src-family kinases (SFKs), an intracellularly located group of non-receptor tyrosine kinases are involved in oncogenesis. The importance of SFKs has been implicated in the promotion of tumor cell motility, proliferation, inhibition of apoptosis, invasion and metastasis. Recent evidences indicate that specific effects of SFKs on epithelial-to-mesenchymal transition (EMT) as well as on endothelial and stromal cells in the tumor microenvironment can have profound effects on tumor microinvasion and metastasis. Although, having been studied extensively, these novel features of SFKs may contribute to greater understanding of benefits from Src inhibition in various types of cancers. Here we review the novel role of SFKs, particularly c-Src in mediating EMT, modulation of tumor endothelial-barrier, transendothelial migration (microinvasion) and metastasis of cancer cells, and discuss the utility of Src inhibitors in vascular normalization and cancer therapy.

Growth-factor-driven rescue to receptor tyrosine kinase (RTK) inhibitors through Akt and Erk phosphorylation in pediatric low grade astrocytoma and ependymoma

Up to now, several clinical studies have been started investigating the relevance of receptor tyrosine kinase (RTK) inhibitors upon progression free survival in various pediatric brain tumors. However, single targeted kinase inhibition failed, possibly due to tumor resistance mechanisms. The present study will extend our previous observations that vascular endothelial growth factor receptor (VEGFR)-2, platelet derived growth factor receptor (PDGFR)β, Src, the epidermal growth factor receptor (ErbB) family, and hepatocyte growth factor receptor (HGFR/cMet) are potentially drugable targets in pediatric low grade astrocytoma and ependymoma with investigations concerning growth-factor-driven rescue. This was investigated in pediatric low grade astrocytoma and ependymoma cell lines treated with receptor tyrosine kinase (RTK) inhibitors e.g. sorafenib, dasatinib, canertinib and crizotinib. Flow cytometry analyses showed high percentage of cells expressing VEGFR-1, fibroblast growth factor receptor (FGFR)-1, ErbB1/EGFR, HGFR and recepteur d’origine nantais (RON) (respectively 52-77%, 34-51%, 63-90%, 83-98%, 65-95%). Their respective inhibitors induced decrease of cell viability, measured with WST-1 cell viability assays. At least this was partially due to increased apoptotic levels measured by Annexin V/Propidium Iodide apoptosis assays. EGF, HGF and FGF, which are normally expressed in brain (tumor) tissue, showed to be effective rescue inducing growth factors resulting in increased cell survival especially during treatment with dasatinib (complete rescue) or sorafenib (partial rescue). Growth-factor-driven rescue was less prominent when canertinib or crizotinib were used. Rescue was underscored by significantly activating downstream Akt and/or Erk phosphorylation and increased tumor cell migration. Combination treatment showed to be able to overcome the growth-factor-driven rescue. In conclusion, our study highlights the extensive importance of environmentally present growth factors in developing tumor escape towards RTK inhibitors in pediatric low grade astrocytoma and ependymoma. It is of great interest to anticipate upon these results for the design of new therapeutic trials with RTK inhibitors in these pediatric brain tumors.

Bcr-Abl tyrosine kinase inhibitors: a patent review

INTRODUCTION

Breakpoint cluster region Abelson (Bcr-Abl) tyrosine kinase (TK) is a constitutively activated cytoplasmic TK and is the underlying cause of chronic myeloid leukemia (CML). To date, imatinib represents the frontline treatment for CML therapy. The development of resistance has prompted the search for novel Bcr-Abl inhibitors.

AREAS COVERED

This review presents a short overview of drugs already approved for CML therapy and of the compounds that are in clinical trials. The body of the article deals with Bcr-Abl inhibitors patented since 2008, focusing on their chemical features.

EXPERT OPINION

The search for Bcr-Abl inhibitors is very active. We believe that a number of patented compounds could enter clinical trials and some could be approved for CML therapy in the next few years. Overall, Bcr-Abl inhibitors constitute a very appealing research field that can be expected to expand further.

γ-H2AX as a biomarker for DNA double-strand breaks in ecotoxicology

The visualisation of DNA damage response proteins enables the indirect measurement of DNA damage. Soon after the occurrence of a DNA double-strand break (DSB), the formation of γ-H2AX histone variants is to be expected. This review is focused on the potential use of the γ-H2AX foci assay in assessing the genotoxicity of environmental contaminants including cytostatic pharmaceuticals, since standard methods may not be sensitive enough to detect the damaging effect of low environmental concentrations of such drugs. These compounds are constantly released into the environment, potentially representing a threat to water quality, aquatic organisms, and, ultimately, human health. Our review of the literature revealed that this method could be used in the biomonitoring and risk assessment of aquatic systems affected by wastewater from the production, usage, and disposal of cytostatic pharmaceuticals.

A BCR/ABL-hIL-2 DNA vaccine enhances the immune responses in BALB/c mice

The use of a DNA vaccine encoding the BCR/ABL fusion gene is thought to be a promising approach for patients with chronic myeloid leukemia (CML) to eradicate minimal residual disease after treatment with chemotherapy or targeted therapy. In this study, our strategy employs genetic technology to create a DNA vaccine encoding the BCR/ABL fusion and human interleukin-2 (hIL-2) genes. The successfully constructed plasmids BCR/ABL-pIRES-hIL-2, BCR/ABL-pIRES, and pIRES-hIL-2 were delivered intramuscularly to BALB/c mice at 14-day intervals for three cycles. The transcription and expression of the BCR/ABL and hIL-2 genes were found in the injected muscle tissues. The interferon-γ (IFN-γ) serum levels were increased, and the splenic CD4⁺/CD8⁺ T cell ratio was significantly decreased in the BCR/ABL-pIRES-hIL-2-injected mice. Furthermore, specific antibodies against K562 cells could be detected by indirect immunofluorescence. These results indicate that a DNA vaccine containing BCR/ABL and hIL-2 together may elicit increased in vivo humoral and cellular immune responses in BALB/c mice.

Imatinib mesilate-induced phosphatidylinositol 3-kinase signalling and improved survival in insulin-producing cells: role of Src homology 2-containing inositol 5'-phosphatase interaction with c-Abl

AIMS/HYPOTHESIS

It is not clear how small tyrosine kinase inhibitors, such as imatinib mesilate, protect against diabetes and beta cell death. The aim of this study was to determine whether imatinib, as compared with the non-cAbl-inhibitor sunitinib, affects pro-survival signalling events in the phosphatidylinositol 3-kinase (PI3K) pathway.

METHODS

Human EndoC-βH1 cells, murine beta TC-6 cells and human pancreatic islets were used for immunoblot analysis of insulin receptor substrate (IRS)-1, Akt and extracellular signal-regulated kinase (ERK) phosphorylation. Phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] plasma membrane concentrations were assessed in EndoC-βH1 and MIN6 cells using evanescent wave microscopy. Src homology 2-containing inositol 5'-phosphatase 2 (SHIP2) tyrosine phosphorylation and phosphatase and tensin homologue deleted on chromosome 10 (PTEN) serine phosphorylation, as well as c-Abl co-localisation with SHIP2, were studied in HEK293 and EndoC-βH1 cells by immunoprecipitation and immunoblot analysis. Gene expression was assessed using RT-PCR. Cell viability was measured using vital staining.

RESULTS

Imatinib stimulated ERK(thr202/tyr204) phosphorylation in a c-Abl-dependent manner. Imatinib, but not sunitinib, also stimulated IRS-1(tyr612), Akt(ser473) and Akt(thr308) phosphorylation. This effect was paralleled by oscillatory bursts in plasma membrane PI(3,4,5)P3 levels. Wortmannin induced a decrease in PI(3,4,5)P3 levels, which was slower in imatinib-treated cells than in control cells, indicating an effect on PI(3,4,5)P3-degrading enzymes. In line with this, imatinib decreased the phosphorylation of SHIP2 but not of PTEN. c-Abl co-immunoprecipitated with SHIP2 and its binding to SHIP2 was largely reduced by imatinib but not by sunitinib. Imatinib increased total β-catenin levels and cell viability, whereas sunitinib exerted negative effects on cell viability.

CONCLUSIONS/INTERPRETATION

Imatinib inhibition of c-Abl in beta cells decreases SHIP2 activity, which results in enhanced signalling downstream of PI3 kinase.

Phosphatidylinositol-3-kinase α catalytic subunit gene somatic mutations in bronchopulmonary neuroendocrine tumours

Bronchopulmonary neuroendocrine tumours (BP-NETs) comprise a large spectrum of tumours including typical carcinoids (TCs), atypical carcinoids (ACs), large-cell neuroendocrine carcinomas (LCNECs) and small-cell lung carcinomas (SCLCs) that exhibit considerably different biological aggressiveness and clinical behaviours. The phosphatidylinositol-3-kinase α catalytic subunit (PIK3CA) gene is known to be involved in the pathogenesis of several types of human cancers through gene amplification, deletions or somatic missense mutations within the helical and catalytic domains. However, the PIK3CA gene status in BP-NETs has yet to be explored. This study aimed to investigate the PIK3CA gene status in a large series of BP-NETs by direct gene sequencing and to analyse its correlation with the main clinicopathological parameters. To the best of our knowledge, we demonstrated for the first time a high frequency of somatic missense mutations (23.2%) in the PIK3CA gene in a series of 190 BP-NETs, including 75 TCs, 23 ACs, 17 LCNECs and 75 SCLCs. The frequency of the PIK3CA gene mutation in the kinase domain was higher (17.9%) than that in the helical domain (5.3%). When the mutational status of the PIK3CA gene was compared with the main clinical and pathological characteristics of the BP-NET patients, we found a significant association between PIK3CA gene mutations and BP-NET histology (p=0.011). Interestingly, the frequency of PIK3CA gene mutations increased with the biological aggressiveness of all BP-NETs, except LCNECs. In conclusion, our results suggest that PIK3CA gene mutations may play a key role in tumourigenesis and aggressiveness of BP-NETs. The PIK3CA gene may represent a favourable candidate for an effective therapeutic strategy in the treatment of patients with BP-NETs.

ABL kinase domain mutations in patients with chronic myeloid leukemia in Jordan

Mutations of the BCR-ABL tyrosine kinase domain constitute a major cause of resistance to tyrosine kinase inhibitors in patients with chronic myelogenous leukemia (CML). In this study, we analyzed peripheral blood samples from 185 Jordanian CML patients for ABL mutations, who were on imatinib for a minimum of 6 months regardless of their disease status and over a period of 5 years. Mutations were detected by nested RT-polymerase chain reaction, followed by direct sequencing of the ABL kinase domain. Twelve different point mutations were detected 25 times in 21 patients. The resultant mutations were as follows: four patients have T315I, three of each of the following: L248V, F317L, and G250E, two of each of the following: H396R, M244V, and T277A, and one of each of the following: F311I, M318T, Q252H, F359A, F359I, and Y326H. After patient follow-up, the mutation had disappeared in 12 patients; 3 patients died; 3 patients were not retested; and 3 patients had persistent mutation. The finding of our study is in line with what has been described in the literature. Detecting ABL mutations in chronic phase may lead to positive outcome by modifying treatment.

Does the small tyrosine kinase inhibitor Imatinib mesylate counteract diabetes by affecting pancreatic islet amyloidosis and fibrosis?

INTRODUCTION

The small tyrosine kinase inhibitor Imatinib Mesylate (Gleevec) protects against diabetes, but it is not known how.

AREAS COVERED

It has been suggested that islet amyloid and fibrotic deposits promote beta-cell failure and death, leading to Type-2 diabetes. As Imatinib is known to possess anti-fibrotic/amyloid properties, in for example systemic sclerosis and mouse models for Alzheimer's disease, the present review will discuss the possibility that Imatinib acts, at least in part, by ameliorating islet hyalinization and its consequences in the pathogenesis of Type-2 diabetes.

EXPERT OPINION

A better understanding of how Imatinib counteracts Type-2 diabetes will possibly help to clarify the pathogenic role of islet amyloid and fibrosis, and hopefully lead to improved treatment of the disease.

Phase II study of single-agent bosutinib, a Src/Abl tyrosine kinase inhibitor, in patients with locally advanced or metastatic breast cancer pretreated with chemotherapy

BACKGROUND

This phase II study evaluated single-agent bosutinib in pretreated patients with locally advanced or metastatic breast cancer.

PATIENTS AND METHODS

Patients received oral bosutinib 400 mg/day. The primary end point was the progression-free survival (PFS) rate at 16 weeks. Secondary end points included objective response rate, clinical benefit rate, 2-year overall survival rate, safety, and changes in levels of bone resorption/formation biomarkers.

RESULTS

Seventy-three patients were enrolled and treated. Median time from diagnosis of metastatic disease to initiation of bosutinib treatment was 24.5 months. For the intent-to-treat population, the PFS rate at 16 weeks was 39.6%. Unexpectedly, all responding patients (n = 4) were hormone receptor positive. The clinical benefit rate was 27.4%. The 2-year overall survival rate was 26.4%. The main toxic effects were diarrhea (66%), nausea (55%), and vomiting (47%). Grade 3-4 laboratory aminotransferase elevations occurred in 14 (19%) patients. Myelosuppression was minimal. No consistent changes in the levels of bone resorption/formation biomarkers were seen.

CONCLUSIONS

Bosutinib showed promising efficacy in prolonging time to progression in chemotherapy-pretreated patients with locally advanced or metastatic breast cancer. Bosutinib was generally well tolerated, with a safety profile different from that of the Src/Abl tyrosine kinase inhibitor dasatinib in a similar patient population.

Effects of Imatinib Mesylate (Gleevec) on human islet NF-kappaB activation and chemokine production in vitro

Purpose

Imatinib Mesylate (Gleevec) is a drug that potently counteracts diabetes both in humans and in animal models for human diabetes. We have previously reported that this compound in human pancreatic islets stimulates NF-κB signaling and islet cell survival. The aim of this study was to investigate control of NF-κB post-translational modifications exerted by Imatinib and whether any such effects are associated with altered islet gene expression and chemokine production in vitro.

Procedures

Human islets were either left untreated or treated with Imatinib for different timepoints. IκB-α and NF-κB p65 phosphorylation and methylation were assessed by immunoblot analysis. Islet gene expression was assessed using a commercial Pathway Finder microarray kit and RT-PCR. Islet chemokine production was determined by flow cytometric bead array analysis.

Findings

Human islet IκB-α and Ser276-p65 phosphorylation were increased by a 20 minute Imatinib exposure. Methylation of p65 at position Lys221 was increased after 60 min of Imatinib exposure and persisted for 3 hours. Microarray analysis of islets exposed to Imatinib for 4 hours revealed increased expression of the inflammatory genes IL-4R, TCF5, DR5, I-TRAF, I-CAM, HSP27 and IL-8. The islet release of IL-8 was augmented in islets cultured over night in the presence of Imatinib. Following 30 hours of Imatinib exposure, the cytokine-induced IκB-α and STAT1 phosphorylation was abolished and diminished, respectively. The cytokine-induced release of the chemokines MIG and IP10 was lower in islets exposed to Imatinib for 30 hours.

Conclusion

Imatinib by itself promotes a modest activation of NF-κB. However, a prolonged exposure of human islets to Imatinib is associated with a dampened response to cytokines. It is possible that Imatinib induces NF-κB preconditioning of islet cells leading to lowered cytokine sensitivity and a mitigated islet inflammation.

Real-time fluorescent resonance energy transfer analysis to monitor drug resistance in chronic myelogenous leukemia

Despite the initial effectiveness of oncogene-directed cancer therapeutics, acquired drug resistance remains the ultimate "Achilles' heel" for long-term durable remission in cancer patients. Acquisition of drug resistance is not more evident elsewhere than in the use of tyrosine kinase inhibitors, imatinib and dasatinib, for patients with chronic myelogenous leukemia. Hence, even though imatinib initially produces remission in the chronic phase, ultimately these therapeutics fail via the emergence of drug resistance, in which chronic myelogenous leukemia could inevitably progress to a terminal blast phase culminating in fatal outcome. Technically, it is challenging to predict the onset of drug resistance in a small number of oncogene-transformed cells, making the decision of when and how to employ second-generation tyrosine kinase inhibitors, or employ novel compounds that would be of benefit in treating drug-resistant Bcr-Abl mutants mainly retrospective. Here, we characterize a rapid and sensitive real-time fluorescent resonance energy transfer-based assay that is able to detect the in vivo activity of Bcr-Abl and its inhibition by small molecule compounds. Due to its real-time and in vivo nature, such an approach has the potential to monitor a drug-resistant phenotype, as well as to identify pharmaceutical agents that inhibit drug-resistant Bcr-Abl oncoproteins in vivo.

Blockade of the ERK or PI3K-Akt signaling pathway enhances the cytotoxicity of histone deacetylase inhibitors in tumor cells resistant to gefitinib or imatinib

Deregulated activation of protein tyrosine kinases, such as the epidermal growth factor receptor (EGFR) and Abl, is associated with human cancers including non-small cell lung cancer (NSCLC) and chronic myeloid leukemia (CML). Although inhibitors of such activated kinases have proved to be of therapeutic benefit in individuals with NSCLC or CML, some patients manifest intrinsic or acquired resistance to these drugs. We now show that, whereas blockade of either the extracellular signal-regulated kinase (ERK) pathway or the phosphatidylinositol 3-kinase (PI3K)-Akt pathway alone induced only a low level of cell death, it markedly sensitized NSCLC or CML cells to the induction of apoptosis by histone deacetylase (HDAC) inhibitors. Such enhanced cell death induced by the respective drug combinations was apparent even in NSCLC or CML cells exhibiting resistance to EGFR or Abl tyrosine kinase inhibitors, respectively. Co-administration of a cytostatic signaling pathway inhibitor may contribute to the development of safer anticancer strategies by lowering the required dose of cytotoxic HDAC inhibitors for a variety of cancers.

Potential utility of small tyrosine kinase inhibitors in the treatment of diabetes

Altered tyrosine kinase signalling has been implicated in several diseases, paving the way for the development of small-molecule TKIs (tyrosine kinase inhibitors). TKIs such as imatinib, sunitinib and dasatinib are clinically used for treating chronic myeloid leukaemia, gastrointestinal stromal tumours and other malignancies. In addition to their use as anti-cancer agents, increasing evidence points towards an anti-diabetic effect of these TKIs. Imatinib and other TKIs counteract diabetes not only in non-obese diabetic mice, but also in streptozotocin diabetic mice, db/db mice, high-fat-treated rats and humans with T2D (Type 2 diabetes). Although the mechanisms of protection need to be investigated further, the effects of imatinib and other TKIs in human T2D and the rapidly growing findings from animal models of T1D (Type 1 diabetes) and T2D are encouraging and give hope to improved treatment of human diabetes. In the present article, we review the anti-diabetic effects of TKIs which appear to involve both protection against beta-cell death and improved insulin sensitivity. Considering the relatively mild side effects of TKIs, we hypothesize that TKIs could be used to treat new-onset T1D, prevent T1D in individuals at high risk of developing the disease, treat the late stages of T2D and improve the outcome of islet transplantation.

Peptide biosensors for the electrochemical measurement of protein kinase activity

The kinase activities are elucidated using the novel redox-active cosubstrate adenosine 5'-[gamma-ferrocene] triphosphate (Fc-ATP), which enables the kinase-catalyzed transfer of a redox active gamma-phosphate-Fc to a hydroxyamino acid. In this report, a versatile electrochemical biosensor is developed for monitoring the activity and inhibition of a serine/threonine kinase, casein kinase 2 (CK2), and protein tyrosine kinases, Abl1-T315I and HER2, in buffered solutions and in cell lysates. The method is based on the labeling of a specific phosphorylation event with Fc, followed by electrochemical detection. The electrochemical response obtained from the "ferrocenylated" peptides enables monitoring the activity of the kinase and its substrate, as well as the inhibition of small molecule inhibitors on protein phosphorylation. Kinetic information was extracted from the electrochemical measurements for the determination of K(m) and V(m) values, which were in agreement with those previously reported. Kinase reactions were also performed in the presence of well-defined inhibitors of CK2, 4,5,6,7-tetrabromo-2-azabenzimidazole, 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole, and E-3-(2,3,4,5-tetrabromophenyl)acrylic acid as well as the nonspecific kinase inhibitors, staurosporine and N-benzoylstaurosporine. On the basis of the dependency of the Fc signal on inhibitor concentration, K(i) of the inhibitors was estimated, which were also in agreement with the literature values. The performance of the biosensor was optimized including the kinase reaction, incubation with Fc-ATP, and the small molecule inhibitors. Peptide modified electrochemical biosensors are promising candidates for cost-effective in vitro kinase activity and inhibitor screening assays.

Apoptosis and autophagy: BIM as a mediator of tumour cell death in response to oncogene-targeted therapeutics

The BCL-2 homology domain 3 (BH3)-only protein, B-cell lymphoma 2 interacting mediator of cell death (BIM) is a potent pro-apoptotic protein belonging to the B-cell lymphoma 2 protein family. In recent years, advances in basic biology have provided a clearer picture of how BIM kills cells and how BIM expression and activity are repressed by growth factor signalling pathways, especially the extracellular signal-regulated kinase 1/2 and protein kinase B pathways. In tumour cells these oncogene-regulated pathways are used to counter the effects of BIM, thereby promoting tumour cell survival. In parallel, a new generation of targeted therapeutics has been developed, which show remarkable specificity and efficacy in tumour cells that are addicted to particular oncogenes. It is now apparent that the expression and activation of BIM is a common response to these new therapeutics. Indeed, BIM has emerged from this marriage of basic and applied biology as an important mediator of tumour cell death in response to such drugs. The induction of BIM alone may not be sufficient for significant tumour cell death, as BIM is more likely to act in concert with other BH3-only proteins, or other death pathways, when new targeted therapeutics are used in combination with traditional chemotherapy agents. Here we discuss recent advances in understanding BIM regulation and review the role of BIM as a mediator of tumour cell death in response to novel oncogene-targeted therapeutics.

Chronic myeloid leukemia therapy: focus on second-generation tyrosine kinase inhibitors

BACKGROUND

Chronic myeloid leukemia, the most common adult leukemia, is characterized by the Ph+ chromosome produced by the fusion of the BCR gene from chromosome 22 and the ABL gene from chromosome 9. Inhibition of the deleterious effects of this potent oncogene by the tyrosine kinase inhibitor (TKI) imatinib has revolutionized care of this disease, but intolerance and resistance does occur.

METHODS

The authors have reviewed both the preclinical and the clinical data concerning second-generation TKIs intended to circumvent or ameliorate issues with imatinib intolerance or resistance.

RESULTS

Two second-generation TKIs, dasatinib and nilotinib, are currently approved by the US Food and Drug Administration. Both have shown significant clinical activity in patients with chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL) who are resistant or intolerant to imatinib or other therapies.

CONCLUSIONS

The TKIs are a superb example of an effective targeted approach for a malignant disease. As more clinical data become available and additional novel agents are developed, specific therapy and dosing strategies for individuals with CML will depend on the status of their disease, the anticipated side effects, and concurrent drug therapy.

Protein kinase inhibitors emodin and dichloro-ribofuranosylbenzimidazole modulate the cellular accumulation and cytotoxicity of cisplatin in a schedule-dependent manner

PURPOSE

Protein kinase inhibitors (PKI) have become prominent agents in cancer therapeutics. However, the specificity for target kinase inhibition can be poor and unwanted effects can emerge in combination regimens. The PKI emodin, for instance, can produce mixed results when combined with cisplatin, and we have sought a biochemical pharmacologic explanation for the negative cytotoxic effects.

METHODS

Human ovarian A2780 tumor cells were exposed to the PKI emodin or dichloro-ribofuranosylbenzimidazole (DRB) with cisplatin using several schedules, and cytotoxicity determined by a growth inhibition assay. Intracellular platinum levels and DNA adducts were estimated by flameless atomic absorption spectrophotometry.

RESULTS

When A2780 cells were exposed first to emodin or DRB and then to cisplatin alone, the cytotoxic effects of cisplatin were significantly enhanced, whereas simultaneous exposure did not enhance the cytotoxicity, but instead inhibited it in the case of DRB. The increase in activity of cisplatin in the sequenced schedule was not due to increases in intracellular levels of cisplatin or DNA adducts, whereas the cytotoxic inhibition was related to a significant fall in both intracellular platinum levels and DNA adducts, which were ascribed to inhibition in cisplatin uptake. Knockdown of hCtr1 (the human copper transporter 1) by siRNA abrogated this inhibition in cisplatin uptake.

CONCLUSION

The results demonstrate that co-exposure of tumor cells to emodin or DRB with cisplatin inhibits platinum drug uptake by impacting the hCtr1 transporter and, thereby, reduce the cytotoxicity of cisplatin. Based on our findings, scheduling of the PKI and the cytotoxic agent should be a major consideration in the clinical design of combination regimens.

Targeting autophagy potentiates tyrosine kinase inhibitor-induced cell death in Philadelphia chromosome-positive cells, including primary CML stem cells

Imatinib mesylate (IM), a potent inhibitor of the BCR/ABL tyrosine kinase, has become standard first-line therapy for patients with chronic myeloid leukemia (CML), but the frequency of resistance increases in advancing stages of disease. Elimination of BCR/ABL-dependent intracellular signals triggers apoptosis, but it is unclear whether this activates additional cell survival and/or death pathways. We have shown here that IM induces autophagy in CML blast crisis cell lines, CML primary cells, and p210BCR/ABL-expressing myeloid precursor cells. IM-induced autophagy did not involve c-Abl or Bcl-2 activity but was associated with ER stress and was suppressed by depletion of intracellular Ca2+, suggesting it is mechanistically nonoverlapping with IM-induced apoptosis. We further demonstrated that suppression of autophagy using either pharmacological inhibitors or RNA interference of essential autophagy genes enhanced cell death induced by IM in cell lines and primary CML cells. Critically, the combination of a tyrosine kinase inhibitor (TKI), i.e., IM, nilotinib, or dasatinib, with inhibitors of autophagy resulted in near complete elimination of phenotypically and functionally defined CML stem cells. Together, these findings suggest that autophagy inhibitors may enhance the therapeutic effects of TKIs in the treatment of CML.

Modulation of reactive oxygen species by antioxidants in chronic myeloid leukemia cells enhances imatinib sensitivity through survivin downregulation

Survivin, a member of the inhibitor of apoptosis protein family and a target for new drugs, is modulated by reactive oxygen species in several types of neoplasms including leukemias. The aim of this study is to find mechanisms to enhance sensitivity to imatinib in imatinib-responsive cells. In this study, we demonstrated through fluorescein isothiocyanate-labeled annexin V for apoptotic cells detection and western blotting that by inhibiting catalase activity, imatinib apoptosis induction was significantly enhanced (P<0.05) through diminishing survivin expression in K562 cells. These findings might be of clinical relevance and might help improve the chemotherapeutic use of imatinib mesylate.