The effect of the dual Src/Abl kinase inhibitor AZD0530 on Philadelphia positive leukaemia cell lines

Saracatinib prompts hemin-induced K562 erythroid differentiation but suppresses erythropoiesis of hematopoietic stem cells

Human myeloid leukemia cells (such as K562) could be used for the study of erythropoiesis, and mature erythroid markers and globins could be induced during leukemia cell differentiation; however, the pathways involved are different compared with those of hematopoietic stem cells (HSCs).We identified the differentially expressed genes (DEGs) of K562 cells and HSCs associated with stem cells and erythroid differentiation. Furthermore, we showed that hemin-induced differentiation of K562 cells could be induced by serum starvation or treatment with the tyrosine kinase inhibitor saracatinib. However, erythroid differentiation of HSCs was inhibited by the deprivation of the important serum component erythropoietin (EPO) or treatment with saracatinib. Finally, we found that the mRNA expression of K562 cells and HSCs was different during saracatinib-treated erythroid differentiation, and the DEGs of K562 cells and HSCs associated with tyrosine-protein kinase were identified.These findings elucidated the cellular phenomenon of saracatinib induction during erythroid differentiation of K562 cells and HSCs, and the potential mechanism is the different mRNA expression profile of tyrosine-protein kinase in K562 cells and HSCs.

Cellular thermal shift assay (CETSA) for determining the drug binding affinity using Ba/F3 clones stably expressing receptor pseudokinases

The majority of drug screening approaches are performed using recombinant proteins, however, drug binding to its target(s) in cells should be also assessed, especially for drugs aimed at modulating intracellular signaling pathways. As a result, the development of a cellular thermal shift assay (CETSA) has become an important tool for determining the binding affinity of drugs to their intracellular targets. Cell lines, such as Ba/F3, are an excellent model system to stably express and study a target protein when this protein is not endogenously expressed or only present at low levels. Together with CETSA, Ba/F3 clones allow study of the transforming properties of the protein in question, its downstream intracellular signaling activation pathways, as well as its drug binding kinetics. This chapter describes in detail the establishment of Ba/F3 clones stably expressing receptor pseudokinases, such as receptor tyrosine kinase-like orphan receptors (ROR1, ROR2) and protein tyrosine kinase 7 (PTK7), and the use thereof to evaluate binding of small molecule inhibitors to their intracellular (pseudo)kinase domain by CETSA.

A Pilot Study on Probing of Imatinib Induced Platelet Dysfunction in Patients with Chronic Myeloid Leukemia-Chronic Phase and Absence of Associated Bleeding Manifestation: Trying to Solve an Enigma

Imatinib, the first Tyrosine Kinase Inhibitor (TKI) used for the treatment of chronic myeloid leukaemia (CML) has revolutionized the management by inhibiting BCR-ABL tyrosine kinase. According to earlier reports there are concerns regarding the adverse effect of imatinib on haemostasis by causing platelet dysfunction. Here we studied platelet function using platelet aggregometry, in 19 CML chronic phase (CML-CP) patients on imatinib therapy, in complete haematologic response (CHR). The median duration of imatinib therapy before performing the test was 154 days. This study reveals that there are large inter-individual variations in platelet functions among imatinib treated patients and different levels of variability have been seen for different agonists. Most common aggregation abnormality (< 50% aggregation) was seen with low dose collagen (1 μg/ml) in 31.57% patients. Despite in-vitro platelet aggregation defects, none of the patients showed any bleeding symptoms. This enigma can possibly be explained by the fact that platelet specific agonists, epinephrine and collagen act in synergy for platelet aggregation compared against individual low dose agonists, supported by ex-vivo experiments in normal healthy control group (n = 5) (p value < 0.0004 for epinephrine, p value < 0.0001 for collagen). This experiment was also confirmed in a CML-CP patient. In future, more studies are needed to find out the exact mechanism of this inhibition.

Fundamental control of grade-specific colorectal cancer morphology by Src regulation of ezrin-centrosome engagement

The phenotypic spectrum of colorectal cancer (CRC) is remarkably diverse, with seemingly endless variations in cell shape, mitotic figures and multicellular configurations. Despite this morphological complexity, histological grading of collective phenotype patterns provides robust prognostic stratification in CRC. Although mechanistic understanding is incomplete, previous studies have shown that the cortical protein ezrin controls diversification of cell shape, mitotic figure geometry and multicellular architecture, in 3D organotypic CRC cultures. Because ezrin is a substrate of Src tyrosine kinase that is frequently overexpressed in CRC, we investigated Src regulation of ezrin and morphogenic growth in 3D CRC cultures. Here we show that Src perturbations disrupt CRC epithelial spatial organisation. Aberrant Src activity suppresses formation of the cortical ezrin cap that anchors interphase centrosomes. In CRC cells with a normal centrosome number, these events lead to mitotic spindle misorientation, perturbation of cell cleavage, abnormal epithelial stratification, apical membrane misalignment, multilumen formation and evolution of cribriform multicellular morphology, a feature of low-grade cancer. In isogenic CRC cells with centrosome amplification, aberrant Src signalling promotes multipolar mitotic spindle formation, pleomorphism and morphological features of high-grade cancer. Translational studies in archival human CRC revealed associations between Src intensity, multipolar mitotic spindle frequency and high-grade cancer morphology. Collectively, our study reveals Src regulation of CRC morphogenic growth via ezrin-centrosome engagement and uncovers combined perturbations underlying transition to high-grade CRC morphology. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Ponatinib promotes a G1 cell-cycle arrest of merlin/NF2-deficient human schwann cells

Neurofibromatosis type 2 (NF2) is a genetic syndrome that predisposes individuals to multiple benign tumors of the central and peripheral nervous systems, including vestibular schwannomas. Currently, there are no FDA approved drug therapies for NF2. Loss of function of merlin encoded by the NF2 tumor suppressor gene leads to activation of multiple mitogenic signaling cascades, including platelet-derived growth factor receptor (PDGFR) and SRC in Schwann cells. The goal of this study was to determine whether ponatinib, an FDA-approved ABL/SRC inhibitor, reduced proliferation and/or survival of merlin-deficient human Schwann cells (HSC). Merlin-deficient HSC had higher levels of phosphorylated PDGFRα/β, and SRC than merlin-expressing HSC. A similar phosphorylation pattern was observed in phospho-protein arrays of human vestibular schwannoma samples compared to normal HSC. Ponatinib reduced merlin-deficient HSC viability in a dose-dependent manner by decreasing phosphorylation of PDGFRα/β, AKT, p70S6K, MEK1/2, ERK1/2 and STAT3. These changes were associated with decreased cyclin D1 and increased p27^Kip1levels, leading to a G₁ cell-cycle arrest as assessed by Western blotting and flow cytometry. Ponatinib did not modulate ABL, SRC, focal adhesion kinase (FAK), or paxillin phosphorylation levels. These results suggest that ponatinib is a potential therapeutic agent for NF2-associated schwannomas and warrants further in vivo investigation.

Enhancing effect of β-elemene emulsion on chemotherapy with harringtonine, aclacinomycin, and Ara-c in treatment of refractory/relapsed acute myeloid leukemia

Objective: This study is to determine the curative effect of β-elemene emulsion on chemotherapy in the treatment of refractory/relapsed acute myeloid leukemia (AML).

Methods: In the β-elemene emulsion plus HAA chemotherapy (harringtonine, aclacinomycin, Ara-c group) group, 120 cases received β-elemene emulsion (400 mg) plus the HAA treatment. A 14-day treatment was a course of treatment, followed by an 8-14 day pause, and then the next course of treatment. The HAA treatment included Ara-C, 100 mg/m2, once every 12 h from day 1 to day 7; aclacinomycin, 20 mg/m2, from day 1 to day 7; and homoharringtonine, 4 mg/m2, from day 1 to day 7. The patients in the control HAA group received HAA treatment only. For both groups, effective antibiotics were given to patients when it was necessary.

Results: The total effective rate in the β-elemene emulsion plus HAA group was 80.8%. But the total effective rate in the HAA only group was 52.9%. These results suggest that the β-elemene emulsion plus HAA treatment has a much better curative effect in comparison with the HAA only treatment (P < 0.05). Furthermore, β-elemene emulsion has slightly adverse response, without causing blood and bone marrow depression.

Conclusion: β-elemene emulsion has a curative effect in treatment of refractory/relapsed AML in combination with harringtonine, aclacinomycin, and Ara-c.

Imatinib resistance: a review of alternative inhibitors in chronic myeloid leukemia

The development of point mutations in the BCR-ABL kinase domain is the main reason for imatinib resistance in chronic myeloid leukemia. Different detection methods are used in chronic myeloid leukemia monitoring, such as direct sequencing, denaturing high performance liquid chromatography and allele specific polymerase chain reaction. Mutation analysis has become mandatory during patient workup of chronic myeloid leukemia in order for the physician to choose the most suitable tyrosine kinase inhibitor. This article, a review of possible therapies used to overcome imatinib resistance, investigates the current position by searching the PubMed electronic database using the following keywords: imatinib, dasatinib, nilotinib, aurora kinase, SRC kinase, mutation, treatment, drugs and resistance. New tyrosine kinase inhibitors include BCR-ABL kinase selective inhibitors, dual ABL/SRC kinase inhibitors and aurora kinase inhibitors. Awareness of the spectrum of new drugs against mutations, in particular the T315I mutation, makes it possible to properly select the best therapy for each patient.

An update on dual Src/Abl inhibitors

c-Src and Bcr-Abl are two cytoplasmatic tyrosine kinases (TKs) involved in the development of malignancies. In particular, Bcr-Abl is the etiologic agent of chronic myeloid leukemia, where Src is also involved; the latter is hyperactivated in several solid tumors. Because of the structural homology between Src and Abl, several compounds originally synthesized as Src inhibitors have also been shown to be Abl inhibitors, useful in overcoming the onset of some types of chronic myeloid leukemia resistances, which frequently appear in the advanced phases of pathology. In recent years, the development of such compounds has been promoted by both excellent preclinical and clinical results, and by the theory that dual or multi-targeted inhibitors might be more effective than selective inhibitors. This review is an update on the most important dual inhibitors already in clinical trials and includes information regarding compounds that have appeared in the literature in recent years.

A HIF-regulated VHL-PTP1B-Src signaling axis identifies a therapeutic target in renal cell carcinoma

Metastatic renal cell carcinoma (RCC) is a molecularly heterogeneous disease that is intrinsically resistant to chemotherapy and radiotherapy. Although therapies targeted to the molecules vascular endothelial growth factor and mammalian target of rapamycin have shown clinical effectiveness, their effects are variable and short-lived, underscoring the need for improved treatment strategies for RCC. Here, we used quantitative phosphoproteomics and immunohistochemical profiling of 346 RCC specimens and determined that Src kinase signaling is elevated in RCC cells that retain wild-type von Hippel-Lindau (VHL) protein expression. RCC cell lines and xenografts with wild-type VHL exhibited sensitivity to the Src inhibitor dasatinib, in contrast to cell lines that lacked the VHL protein, which were resistant. Forced expression of hypoxia-inducible factor (HIF) in RCC cells with wild-type VHL diminished Src signaling output by repressing transcription of the Src activator protein tyrosine phosphatase 1B (PTP1B), conferring resistance to dasatinib. Our results suggest that a HIF-regulated VHL-PTP1B-Src signaling pathway determines the sensitivity of RCC to Src inhibitors and that stratification of RCC patients with antibody-based profiling may identify patients likely to respond to Src inhibitors in RCC clinical trials.

Novel dual Src/Abl inhibitors for hematologic and solid malignancies

IMPORTANCE OF THE FIELD

c-Src and Bcr-Abl are two non-receptor or cytoplasmic tyrosine kinases (TKs) that play important roles in the development of solid and hematological malignancies. Indeed, Src is overexpressed or hyperactivated in a variety of solid tumors, while Bcr-Abl is the causative agent of chronic myeloid leukemia (CML), where Src is also involved. The two enzymes share significant sequence homology and remarkable structural resemblance.

AREAS COVERED IN THIS REVIEW

ATP-competitive compounds originally developed as Src inhibitors, showed to be also potent Abl inhibitors. Dasatinib, the first dual Src/Abl inhibitor approved by the US FDA in 2006 for the treatment of imatinib-resistant CML, is currently being tested in several clinical trials for the treatment of different solid tumors. SKI-606 and AZD0530 are two other important dual Src/Abl inhibitors extensively tested in animal models and in clinical trials, but not entered into therapy yet.

WHAT THE READER WILL GAIN

In this review we will report the latest results regarding dasatinib, SKI-606 and AZD0530, but also the knowledge on new compounds that have appeared in the literature in the last few years, including AP24163, AP24534, XL228, DC2036. We will focus on the most recent clinical trials or on preclinical studies that are in progress on these small-molecule TK inhibitors that represent a targeted therapy with high potential against cancer.

TAKE HOME MESSAGE

Molecularly targeted therapies, including the inhibition of specific TKs hyperactivated or overexpressed in many human cancers, could be less toxic than the classical non-specific cytotoxic chemotherapeutic agents; they could offer important therapeutic effects, especially if used in association with other agents such as monoclonal antibodies.

Saracatinib Impairs Head and Neck Squamous Cell Carcinoma Invasion by Disrupting Invadopodia Function

Elevated Src kinase activity is linked to the progression of solid tumors, including head and neck squamous cell carcinoma (HNSCC). Src regulates HNSCC proliferation and tumor invasion, with the Src-targeted small molecule inhibitor saracatinib displaying potent anti-invasive effects in preclinical studies. However, the pro-invasive cellular mechanism(s) perturbed by saracatinib are unclear. The anti-proliferative and anti-invasive effects of saracatinib on HNSCC cell lines were therefore investigated in pre-clinical cell and mouse model systems. Saracatinib treatment inhibited growth, cell cycle progression and transwell Matrigel invasion in HNSCC cell lines. Dose-dependent decreases in Src activation and phosphorylation of the invasion-associated substrates focal adhesion kinase, p130 CAS and cortactin were also observed. While saracatinib did not significantly impact HNSCC tumor growth in a mouse orthotopic model of tongue squamous cell carcinoma, impaired perineural invasion and cervical lymph node metastasis was observed. Accordingly, saracatinib treatment displayed a dose-dependent inhibitory effect on invadopodia formation, extracellular matrix degradation and matrix metalloprotease 9 activation. These results suggest that inhibition of Src kinase by saracatinib impairs the pro-invasive activity of HNSCC by inhibiting Src substrate phosphorylation important for invadopodia formation and associated matrix metalloprotease activity.