Src family kinases and their role in hematological malignancies

New sights of immunometabolism and agent progress in colitis associated colorectal cancer

Colitis associated colorectal cancer is a disease with a high incidence and complex course that develops from chronic inflammation and deteriorates after various immune responses and inflammation-induced attacks. Colitis associated colorectal cancer has the characteristics of both immune diseases and cancer, and the similarity of treatment models contributes to the similar treatment dilemma. Immunometabolism contributes to the basis of life and is the core of many immune diseases. Manipulating metabolic signal transduction can be an effective way to control the immune process, which is expected to become a new target for colitis associated colorectal cancer therapy. Immune cells participate in the whole process of colitis associated colorectal cancer development by transforming their functional condition via changing their metabolic ways, such as glucose, lipid, and amino acid metabolism. The same immune and metabolic processes may play different roles in inflammation, dysplasia, and carcinoma, so anti-inflammation agents, immunomodulators, and agents targeting special metabolism should be used in combination to prevent and inhibit the development of colitis associated colorectal cancer.

Intracellular angiopoietin-1 promotes TKI-resistance via activation of JAK/STAT5 pathway in chronic myeloid leukemia

Drug resistance from BCR-ABL tyrosine kinase inhibitors (TKIs) and other chemotherapeutics results in treatment failure and disease progression in chronic myeloid leukemia (CML). However, the mechanism is still uncertain. In this study, we investigated the role of angiopoietin-1 (ANG-1) as a potential prognostic factor for drug resistance in CML. Both intracellular and secretory ANG-1 (iANG-1 and sANG-1) were overexpressed in multidrug-resistant CML samples. The IC₅₀ value was higher in primary CD34⁺ CD38^- cells with more ANG-1. Silencing ANG-1significantly sensitized three TKI-resistant CML cell lines to imatinib (IM) while recombinant human ANG-1 failed to retain cell survival in vitro. This indicated the important role of iANG-1 as opposed to sANG-1 in CML drug resistance. Moreover, a similar effect was observed in xenograft mice models bearing ANG-1-silenced CML cells. Subsequently, pathway analysis and protein validation experiments showed activation of the JAK/STAT pathway and augmentation of STAT5a phosphorylation in ANG-1 restored CML cells. Upstream Src phosphorylation, which plays a crucial role in CML drug resistance, was also upregulated as a key event in iANG-1-related JAK/STAT pathway activation. In conclusion, our study elucidated a new BCR-ABL independent molecular mechanism induced by intracytoplasmic ANG-1 overexpression as a potential strategy for overcoming CML resistance.

ATP-site inhibitors induce unique conformations of the acute myeloid leukemia-associated Src-family kinase, Fgr

The Src-family kinase Fgr is expressed primarily in myeloid hematopoietic cells and contributes to myeloid leukemia. Here, we present X-ray crystal structures of Fgr bound to the ATP-site inhibitors A-419259 and TL02-59, which show promise as anti-leukemic agents. A-419259 induces a closed Fgr conformation, with the SH3 and SH2 domains engaging the SH2-kinase linker and C-terminal tail, respectively. In the Fgr:A-419259 complex, the activation loop of one monomer inserts into the active site of the other, providing a snapshot of trans-autophosphorylation. By contrast, TL02-59 binding induced SH2 domain displacement from the C-terminal tail and SH3 domain release from the linker. Solution studies using HDX MS were consistent with the crystal structures, with A-419259 reducing and TL02-59 enhancing solvent exposure of the SH3 domain. These structures demonstrate that allosteric connections between the kinase and regulatory domains of Src-family kinases are regulated by the ligand bound to the active site.

Exosome as a target for cancer treatment

Exosomes are small vesicles covered by a lipid bilayer, ranging in size from 50 nm to 90 nm, secreted by different cell types in the body under normal and pathological conditions. They are surrounded by cell-segregated membrane complexes and play a role in the pathological and physiological environments of target cells by transfer of different molecules such as microRNA (miRNA). Exosomes have been detected in many body fluids, such as in the amniotic fluid, urine, breast milk, blood, saliva, ascites, semen, and bile. They include proteins, lipids, and nucleic acids such as DNA, RNA, and miRNA, which have many functions in target cells under pathological and physiological conditions. They participate in pathological processes such as tumor growth and survival, autoimmunity, neurodegenerative disorders, infectious diseases, inflammation conditions, and others. Biomarkers in exosomes isolated from body fluids have allowed for a more precise and consistent diagnostic method than previous approaches. Exosomes can be used in a variety of intracellular functions, and with advances in molecular techniques they can be used in the treatment and diagnosis of many diseases, including cancer. These vesicles play a significant role in various stages of cancer. Tumor-derived exosomes have an important role in tumor growth, survival, and metastasis. In contrast, the use of stem cells in cancer treatment is a relatively new scientific area. We hope to address targeted use of miRNA-carrying exosomes in cancer therapy in this review paper.

Serum levels of FAK and some of its effectors in adult AML: correlation with prognostic factors and survival

Focal adhesion kinase (FAK), human myofibrillogenesis regulator-1 (MR-1), ephrin receptor type A4 (EphA4), proto-oncogene tyrosine kinase Src (Src), and protein kinase C (PKC) are important markers in proliferation, survival, and migration in some cancers. However, the significance of each is still unclear in different malignancies, including acute myeloid leukemia (AML). Therefore, this study was conducted to investigate their serum levels in Egyptian adult de novo AML patients (n = 70) against healthy volunteers (n = 20). We managed to study the correlation between each pair and to investigate their association with diagnosis, prognosis, and survival. Serum levels were analyzed using enzyme-linked immunosorbent assay (ELISA). We found that FAK, MR-1, Src, and PKC serum levels were significantly higher in AML patients compared to control (p < 0.0001), and this was associated with significantly lower EphA4 level (p < 0.0001). Interestingly, we also observed a significant negative correlation of FAK (p = 0.027), MR-1 (p = 0.003), Src (p = 0.038), and PKC (p = 0.03) with patients' overall survival (OS) while there was a positive significant correlation between EphA4 and OS (p = 0.007). In conclusion, this study suggests that FAK, MR-1, EphA4, Src, and PKC may be used as early diagnostic and prognostic markers with high sensitivity and specificity in AML patients and thus may be incorporated into the patients' early diagnostic and prognostic panels.

Protein Tyrosine Kinases: Their Roles and Their Targeting in Leukemia

Simple Summary

Protein phosphorylation is a key regulatory mechanism that controls a wide variety of cellular responses. This process is catalysed by the members of the protein kinase superfamily that are classified into two main families based on their ability to phosphorylate either tyrosine or serine and threonine residues in their substrates. Massive research efforts have been invested in dissecting the functions of tyrosine kinases, revealing their importance in the initiation and progression of human malignancies. Based on these investigations, numerous tyrosine kinase inhibitors have been included in clinical protocols and proved to be effective in targeted therapies for various haematological malignancies. In this review, we provide insights into the role of tyrosine kinases in leukaemia and discuss their targeting for therapeutic purposes with the currently available inhibitory compounds.

Abstract

Protein kinases constitute a large group of enzymes catalysing protein phosphorylation and controlling multiple signalling events. The human protein kinase superfamily consists of 518 members and represents a complicated system with intricate internal and external interactions. Protein kinases are classified into two main families based on the ability to phosphorylate either tyrosine or serine and threonine residues. Among the 90 tyrosine kinase genes, 58 are receptor types classified into 20 groups and 32 are of the nonreceptor types distributed into 10 groups. Tyrosine kinases execute their biological functions by controlling a variety of cellular responses, such as cell division, metabolism, migration, cell–cell and cell matrix adhesion, cell survival and apoptosis. Over the last 30 years, a major focus of research has been directed towards cancer-associated tyrosine kinases owing to their critical contributions to the development and aggressiveness of human malignancies through the pathological effects on cell behaviour. Leukaemia represents a heterogeneous group of haematological malignancies, characterised by an uncontrolled proliferation of undifferentiated hematopoietic cells or leukaemia blasts, mostly derived from bone marrow. They are usually classified as chronic or acute, depending on the rates of their progression, as well as myeloid or lymphoblastic, according to the type of blood cells involved. Overall, these malignancies are relatively common amongst both children and adults. In malignant haematopoiesis, multiple tyrosine kinases of both receptor and nonreceptor types, including AXL receptor tyrosine kinase (AXL), Discoidin domain receptor 1 (DDR1), Vascular endothelial growth factor receptor (VEGFR), Fibroblast growth factor receptor (FGFR), Mesenchymal–epithelial transition factor (MET), proto-oncogene c-Src (SRC), Spleen tyrosine kinase (SYK) and pro-oncogenic Abelson tyrosine-protein kinase 1 (ABL1) mutants, are implicated in the pathogenesis and drug resistance of practically all types of leukaemia. The role of ABL1 kinase mutants and their therapeutic inhibitors have been extensively analysed in scientific literature, and therefore, in this review, we provide insights into the impact and mechanism of action of other tyrosine kinases involved in the development and progression of human leukaemia and discuss the currently available and emerging treatment options based on targeting these molecules.

The (Patho)Biology of SRC Kinase in Platelets and Megakaryocytes

Proto-oncogene tyrosine-protein kinase SRC (SRC), as other members of the SRC family kinases (SFK), plays an important role in regulating signal transduction by different cell surface receptors after changes in the cellular environment. Here, we reviewed the role of SRC in platelets and megakaryocytes (MK). In platelets, inactive closed SRC is coupled to the β subunit of integrin α_IIbβ₃ while upon fibrinogen binding during platelet activation, α_IIbβ₃-mediated outside-in signaling is initiated by activation of SRC. Active open SRC now further stimulates many downstream effectors via tyrosine phosphorylation of enzymes, adaptors, and especially cytoskeletal components. Functional platelet studies using SRC knockout mice or broad spectrum SFK inhibitors pointed out that SRC mediates their spreading on fibrinogen. On the other hand, an activating pathological SRC missense variant E527K in humans that causes bleeding inhibits collagen-induced platelet activation while stimulating platelet spreading. The role of SRC in megakaryopoiesis is much less studied. SRC knockout mice have a normal platelet count though studies with SFK inhibitors point out that SRC could interfere with MK polyploidization and proplatelet formation but these inhibitors are not specific. Patients with the SRC E527K variant have thrombocytopenia due to hyperactive SRC that inhibits proplatelet formation after increased spreading of MK on fibrinogen and enhanced formation of podosomes. Studies in humans have contributed significantly to our understanding of SRC signaling in platelets and MK.

Targeting N-myristoylation for therapy of B-cell lymphomas

Myristoylation, the N-terminal modification of proteins with the fatty acid myristate, is critical for membrane targeting and cell signaling. Because cancer cells often have increased N-myristoyltransferase (NMT) expression, NMTs were proposed as anti-cancer targets. To systematically investigate this, we performed robotic cancer cell line screens and discovered a marked sensitivity of hematological cancer cell lines, including B-cell lymphomas, to the potent pan-NMT inhibitor PCLX-001. PCLX-001 treatment impacts the global myristoylation of lymphoma cell proteins and inhibits early B-cell receptor (BCR) signaling events critical for survival. In addition to abrogating myristoylation of Src family kinases, PCLX-001 also promotes their degradation and, unexpectedly, that of numerous non-myristoylated BCR effectors including c-Myc, NFκB and P-ERK, leading to cancer cell death in vitro and in xenograft models. Because some treated lymphoma patients experience relapse and die, targeting B-cell lymphomas with a NMT inhibitor potentially provides an additional much needed treatment option for lymphoma.

The E3 ubiquitin ligase TRIM7 suppressed hepatocellular carcinoma progression by directly targeting Src protein

Aberrant Src kinase activity is known to be involved in a variety of human malignancies, whereas the regulatory mechanism of Src has not been completely clarified. Here, we demonstrated that tripartite motif containing 7 (TRIM7) directly interacted with Src, induced Lys48-linked polyubiquitination of Src and reduced the abundance of Src protein in hepatocellular carcinoma (HCC) cells. We further identified TRIM7 as a tumor suppressor in HCC cells through its negative modulation of the Src-mTORC1-S6K1 axis in vivo and in vitro in several HCC models. Moreover, we verified the dysregulated expression of TRIM7 in clinical liver cancer tissues and its negative correlation with Src protein in clinical HCC specimens. Overall, we demonstrated that TRIM7 suppressed HCC progression through its direct negative regulation of Src and modulation of the Src-mTORC1-S6K1 axis; thus, we provided a novel insight into the development of HCC and defined a promising therapeutic strategy for cancers with overactive Src by modulating TRIM7.

Targeting the complexity of Src signalling in the tumour microenvironment of pancreatic cancer: from mechanism to therapy

Pancreatic cancer, a disease with extremely poor prognosis, has been notoriously resistant to virtually all forms of treatment. The dynamic crosstalk that occurs between tumour cells and the surrounding stroma, frequently mediated by intricate Src/FAK signalling, is increasingly recognised as a key player in pancreatic tumourigenesis, disease progression and therapeutic resistance. These important cues are fundamental for defining the invasive potential of pancreatic tumours, and several components of the Src and downstream effector signalling have been proposed as potent anticancer therapeutic targets. Consequently, numerous agents that block this complex network are being extensively investigated as potential antiinvasive and antimetastatic therapeutic agents for this disease. In this review, we will discuss the latest evidence of Src signalling in PDAC progression, fibrotic response and resistance to therapy. We will examine future opportunities for the development and implementation of more effective combination regimens, targeting key components of the oncogenic Src signalling axis, and in the context of a precision medicine-guided approach.

Targeting Tyrosine Kinases in Acute Myeloid Leukemia: Why, Who and How?

Acute myeloid leukemia (AML) is a myeloid malignancy carrying a heterogeneous molecular panel of mutations participating in the blockade of differentiation and the increased proliferation of myeloid hematopoietic stem and progenitor cells. The historical "3 + 7" treatment (cytarabine and daunorubicin) is currently challenged by new therapeutic strategies, including drugs depending on the molecular landscape of AML. This panel of mutations makes it possible to combine some of these new treatments with conventional chemotherapy. For example, the FLT3 receptor is overexpressed or mutated in 80% or 30% of AML, respectively. Such anomalies have led to the development of targeted therapies using tyrosine kinase inhibitors (TKIs). In this review, we document the history of TKI targeting, FLT3 and several other tyrosine kinases involved in dysregulated signaling pathways.

Amelioration of amyloid β-FcγRIIb neurotoxicity and tau pathologies by targeting LYN

SRC-family kinases (SFKs) have been implicated in Alzheimer's disease (AD), but their mode of action was scarcely understood. Here, we show that LYN plays an essential role in amyloid β (Aβ)-triggered neurotoxicity and tau hyperphosphorylation by phosphorylating Fcγ receptor IIb2 (FcγRIIb2). We found that enzyme activity of LYN was increased in the brain of AD patients and was promoted in neuronal cells exposed to Aβ 1-42 (Aβ_1-42). Knockdown of LYN expression inhibited Aβ_1-42-induced neuronal cell death. Of note, LYN interacted with FcγRIIb2 upon exposure to Aβ_1-42 and phosphorylated FcγRIIb2 at Tyr273 within immunoreceptor tyrosine-based inhibitory motif in neuronal cells. With the use of the structure-based drug design, we isolated KICG2576, an ATP-competitive inhibitor of LYN. Determination of cocrystal structure illustrated that KICG2576 bound to the cleft in the LYN kinase domain and inhibited LYN with a half-maximal inhibitory concentration value of 0.15 μM. KICG2576 inhibited Aβ- or FcγRIIb2-induced cell death, and this effect was better than pyrazolopyrimidine 1, a widely used inhibitor of SFK. Upon exposure to Aβ, KICG2576 blocked the phosphorylation of FcγRIIb2 and translocation of phosphatidylinositol 3,4,5-trisphosphate 5-phosphatase 2, a binding protein to the phosphorylated FcγRIIb2, to the plasma membrane, resulting in the inhibition of tau hyperphosphorylation, the downstream event of Aβ_1-42-FcγRIIb2 binding. Furthermore, intracerebroventricular injection of KICG2576 into mice ameliorated Aβ-induced memory impairment. These results suggest that LYN plays a crucial role in Aβ_1-42-mediated neurotoxicity and tau pathology, providing a therapeutic potential of LYN in AD.-Gwon, Y., Kim, S.-H., Kim, H. T., Kam, T.-I., Park, J., Lim, B., Cha, H., Chang, H.-J., Hong, Y. R., Jung, Y.-K. Amelioration of amyloid β-FcγRIIb neurotoxicity and tau pathologies by targeting LYN.

The Src family kinase Fgr is a transforming oncoprotein that functions independently of SH3-SH2 domain regulation

Fgr is a member of the Src family of nonreceptor tyrosine kinases, which are overexpressed and constitutively active in many human cancers. Fgr expression is restricted to myeloid hematopoietic cells and is markedly increased in a subset of bone marrow samples from patients with acute myeloid leukemia (AML). Here, we investigated the oncogenic potential of Fgr using Rat-2 fibroblasts that do not express the kinase. Expression of either wild-type or regulatory tail-mutant constructs of Fgr promoted cellular transformation (inferred from colony formation in soft agar), which was accompanied by phosphorylation of the Fgr activation loop, suggesting that the kinase domain of Fgr functions independently of regulation by its noncatalytic SH3-SH2 region. Unlike other family members, recombinant Fgr was not activated by SH3-SH2 domain ligands. However, hydrogen-deuterium exchange mass spectrometry data suggested that the regulatory SH3 and SH2 domains packed against the back of the kinase domain in a Src-like manner. Sequence alignment showed that the activation loop of Fgr was distinct from that of all other Src family members, with proline rather than alanine at the +2 position relative to the activation loop tyrosine. Substitution of the activation loop of Fgr with the sequence from Src partially inhibited kinase activity and suppressed colony formation. Last, Fgr expression enhanced the sensitivity of human myeloid progenitor cells to the cytokine GM-CSF. Because its kinase domain is not sensitive to SH3-SH2–mediated control, simple overexpression of Fgr without mutation may contribute to oncogenic transformation in AML and other blood cancers.

Role of Non Receptor Tyrosine Kinases in Hematological Malignances and its Targeting by Natural Products

Tyrosine kinases belong to a family of enzymes that mediate the movement of the phosphate group to tyrosine residues of target protein, thus transmitting signals from the cell surface to cytoplasmic proteins and the nucleus to regulate physiological processes. Non-receptor tyrosine kinases (NRTK) are a sub-group of tyrosine kinases, which can relay intracellular signals originating from extracellular receptor. NRTKs can regulate a huge array of cellular functions such as cell survival, division/propagation and adhesion, gene expression, immune response, etc. NRTKs exhibit considerable variability in their structural make up, having a shared kinase domain and commonly possessing many other domains such as SH2, SH3 which are protein-protein interacting domains. Recent studies show that NRTKs are mutated in several hematological malignancies, including lymphomas, leukemias and myelomas, leading to aberrant activation. It can be due to point mutations which are intragenic changes or by fusion of genes leading to chromosome translocation. Mutations that lead to constitutive kinase activity result in the formation of oncogenes, such as Abl, Fes, Src, etc. Therefore, specific kinase inhibitors have been sought after to target mutated kinases. A number of compounds have since been discovered, which have shown to inhibit the activity of NRTKs, which are remarkably well tolerated. This review covers the role of various NRTKs in the development of hematological cancers, including their deregulation, genetic alterations, aberrant activation and associated mutations. In addition, it also looks at the recent advances in the development of novel natural compounds that can target NRTKs and perhaps in combination with other forms of therapy can show great promise for the treatment of hematological malignancies.

Csk-homologous kinase (Chk) is an efficient inhibitor of Src-family kinases but a poor catalyst of phosphorylation of their C-terminal regulatory tyrosine

Background

C-terminal Src kinase (Csk) and Csk-homologous kinase (Chk) are the major endogenous inhibitors of Src-family kinases (SFKs). They employ two mechanisms to inhibit SFKs. First, they phosphorylate the C-terminal tail tyrosine which stabilizes SFKs in a closed inactive conformation by engaging the SH2 domain in cis. Second, they employ a non-catalytic inhibitory mechanism involving direct binding of Csk and Chk to the active forms of SFKs that is independent of phosphorylation of their C-terminal tail. Csk and Chk are co-expressed in many cell types. Contributions of the two mechanisms towards the inhibitory activity of Csk and Chk are not fully clear. Furthermore, the determinants in Csk and Chk governing their inhibition of SFKs by the non-catalytic inhibitory mechanism are yet to be defined.

Methods

We determined the contributions of the two mechanisms towards the inhibitory activity of Csk and Chk both in vitro and in transduced colorectal cancer cells. Specifically, we assayed the catalytic activities of Csk and Chk in phosphorylating a specific peptide substrate and a recombinant SFK member Src. We employed surface plasmon resonance spectroscopy to measure the kinetic parameters of binding of Csk, Chk and their mutants to a constitutively active mutant of the SFK member Hck. Finally, we determined the effects of expression of recombinant Chk on anchorage-independent growth and SFK catalytic activity in Chk-deficient colorectal cancer cells.

Results

Our results revealed Csk as a robust enzyme catalysing phosphorylation of the C-terminal tail tyrosine of SFKs but a weak non-catalytic inhibitor of SFKs. In contrast, Chk is a poor catalyst of SFK tail phosphorylation but binds SFKs with high affinity, enabling it to efficiently inhibit SFKs with the non-catalytic inhibitory mechanism both in vitro and in transduced colorectal cancer cells. Further analyses mapped some of the determinants governing this non-catalytic inhibitory mechanism of Chk to its kinase domain.

Conclusions

SFKs are activated by different upstream signals to adopt multiple active conformations in cells. SFKs adopting these conformations can effectively be constrained by the two complementary inhibitory mechanisms of Csk and Chk. Furthermore, the lack of this non-catalytic inhibitory mechanism accounts for SFK overactivation in the Chk-deficient colorectal cancer cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-017-0186-x) contains supplementary material, which is available to authorized users.

FAK-Src-paxillin system expression and disease outcome in human neuroblastoma

BACKGROUND

Neuroblastoma (NB) often presents with metastatic disease and poor survival. The need for new prognostic markers remains invaluable. The FAK-Src-Paxillin protein system is associated with aggressive phenotype in adult malignancies but is largely unexplored in pediatric NB.

OBJECTIVE

To assess FAK-Src-Paxillin protein expression in human NB cell lines and clinical cytology material and to delineate its association with survival.

DESIGN/METHODS

Western blot and immunohistochemistry were applied for FAK-Src-Paxillin expression in NB cell lines and 23 human cytology specimens, respectively. Protein expression in human clinical samples was correlated with clinicopathological parameters, MYCN amplification and survival.

RESULTS

FAK, Src and Paxillin proteins are expressed in human NB cells lines, and can be detected in clinical cytology specimens from NB patients, (59%, 32% and 33% respectively). Simultaneous FAK-Src-Paxillin expression was noted in 30% of NB patients. Children with concomitant positivity FAK, Src, and Paxillin tumors, as well as MYCN amplification, had increased mortality compared to those without.

CONCLUSIONS

FAK-Src-Paxillin system is a marker of unfavorable prognosis for human NB patients but also a promising therapeutic target.

A Pyrazolo[3,4-d]pyrimidine Compound Reduces Cell Viability and Induces Apoptosis in Different Hematological Malignancies

Molecular targeted therapies are based upon drugs acting on tumors by interfering with specific targets involved in growth and spread of cancer. Many targeted therapies were approved by Food and Drug Administration as standard treatment, others were introduced into preclinical or clinical studies on hematological malignancies (HMs). The development of drug-resistance in some HMs and the lack of effective treatments in other ones emphasized the need for searching new molecular targets and therapeutic agents. The aim of this study was to evaluate the effects of 4c pyrazolo[3,4-d]pyrimidine compound, a Src inhibitor, on lymphoid and myeloid neoplasms. Here, we demonstrated its ability to reduce cell viability, induce apoptosis and cell cycle arrest in lymphoid cell lines such as Jurkat, SKMM1, Derl-2/7, and myeloid cell lines, such as Jurl-MK1. Moreover, we reported a high expression of a Src kinase, Fyn, in these cell lines compared to healthy subjects. This study was a starting point to investigate 4c pyrazolo[3,4-d]pyrimidine compound as a drug for HMs and Src kinases as its potential molecular targets.