Inhibition Of Src Kinase Activity Research Articles

Abstract B020: Development of novel Src-targeting strategies to block bladder cancer invasive progression

Abstract Background: Treatment of muscle-invasive bladder cancer remains challenging and, BCG, one of the few treatments that prevents progression of high-risk non-muscle invasive tumors to invasive metastatic disease, is difficult to obtain. Thus, development of new treatment approaches to block progression to muscle invasive disease is essential. We find that TRIM29 (tripartite motif containing 29, also known as ATDC), drives bladder cancer invasive progression through modulation of focal adhesions containing FAK and c-Src (Src). Despite this, literature has reported conflicting effects of Src knockdown and Src kinase inhibition on migration, perhaps due to separable pro- and anti-invasive functions of Src in bladder cancer. Hypothesis: Src drives bladder cancer invasive progression specifically through its tyrosine kinase activity within focal adhesions. Methods: We used 2D live cell migration assays and 3D spheroid invasion assays to test dasatinib, highly specific, novel conformation inhibitors of Src, a novel Src PROTAC, and siRNA against Src on bladder cancer migration and invasion. Results: Dasatinib and our novel conformation-specific inhibitors inhibited Src kinase activity and both siRNA and the novel PROTAC reduced total Src expression in vitro. Neither dasatinib, conformation inhibitors, siRNA, nor the PROTAC impacted bladder cancer cell viability in UM-UC5, UM-UC9 or UM-UC14 cell lines. Interestingly, we found that inhibiting Src’s kinase activity with either dasatinib or conformation-specific inhibitors abrogated bladder cancer migration. Conclusion: These results point to the selective importance of Src in regulating bladder cancer migration and invasion. They also suggest that novel Src targeting agents have potential clinical utility in the prevention of bladder cancer invasive progression. Citation Format: Nicole A. Jerome, Yin Wang, Marian L. Henderson, Luke Broses, Kathleen C. Day, Mark L. Day, Matthew B. Soellner, Phillip L. Palmbos. Development of novel Src-targeting strategies to block bladder cancer invasive progression [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr B020.

Tyrosine phosphorylation-mediated YAP1-TFAP2A interactions coordinate transcription and trastuzumab resistance in HER2+ breast cancer

Trastuzumab resistance in HER2+ breast cancer (BC) is the major reason leading to poor prognosis of BC patients. Oncogenic gene overexpression or aberrant activation of tyrosine kinase SRC is identified to be the key modulator of trastuzumab response. However, the detailed regulatory mechanisms underlying SRC activation-associated trastuzumab resistance remain poorly understood. In the present study, we discover that SRC-mediated YAP1 tyrosine phosphorylation facilitates its interaction with transcription factor AP-2 alpha (activating enhancer binding protein 2 alpha, TFAP2A), which in turn promotes YAP1/TEAD-TFAP2A (YTT) complex-associated transcriptional outputs, thereby conferring trastuzumab resistance in HER2+ BC. Inhibition of SRC kinase activity or disruption of YTT complex sensitizes cells to trastuzumab treatment in vitro and in vivo. Additionally, we also identify YTT complex co-occupies the regulatory regions of a series of genes related to trastuzumab resistance and directly regulates their transcriptions, including EGFR, HER2, H19 and CTGF. Moreover, YTT-mediated transcriptional regulation is coordinated by SRC kinase activity. Taken together, our study reveals that SRC-mediated YTT complex formation and transcriptions are responsible for multiple mechanisms associated with trastuzumab resistance. Therefore, targeting HER2 signaling in combination with the inhibition of YTT-associated transcriptional outputs could serve as the treatment strategy to overcome trastuzumab resistance caused by SRC activation.

Retraction: Developing and Testing Methylated Nano-Structured Dipeptides that Inhibit Src Kinase Activity <em>In Vitro</em> for Anti-Cancer Applications

Retraction: Developing and Testing Methylated Nano-Structured Dipeptides that Inhibit Src Kinase Activity <em>In Vitro</em> for Anti-Cancer Applications

An Ethanol Extract of Perilla frutescens Leaves Suppresses Adrenergic Agonist-Induced Metastatic Ability of Cancer Cells by Inhibiting Src-Mediated EMT.

Previous studies have indicated that the adrenergic receptor signaling pathway plays a fundamental role in chronic stress-induced cancer metastasis. In this study, we investigated whether an ethanol extract of Perilla frutescens leaves (EPF) traditionally used to treat stress-related symptoms by moving Qi could regulate the adrenergic agonist-induced metastatic ability of cancer cells. Our results show that adrenergic agonists including norepinephrine (NE), epinephrine (E), and isoproterenol (ISO) increased migration and invasion of MDA-MB-231 human breast cancer cells and Hep3B human hepatocellular carcinoma cells. However, such increases were completely abrogated by EPF treatment. E/NE induced downregulation of E-cadherin and upregulation of N-cadherin, Snail, and Slug. Such effects were clearly reversed by pretreatment with EPF, suggesting that the antimetastatic activity of EPF could be related to epithelial-mesenchymal transition (EMT) regulation. EPF suppressed E/NE-stimulated Src phosphorylation. Inhibition of Src kinase activity with dasatinib completely suppressed the E/NE-induced EMT process. Transfecting MDA-MB-231 cells with constitutively activated Src (SrcY527F) diminished the antimigration effect of EPF. Taken together, our results demonstrate that EPF can suppress the adrenergic agonist-promoted metastatic ability of cancer cells by inhibiting Src-mediated EMT. This study provides basic evidence supporting the probable use of EPF to prevent metastasis in cancer patients, especially those under chronic stress.

Regulation, targets and functions of CHK.

Src family kinases (SFKs) play pivotal roles in multiple signaling pathways (Yeatman, 2004). SFK activity is inhibited by phosphorylation at its C-terminal tyrosine, by CSK (C-terminal Src kinase) and CHK (CSK-homologous kinase). CHK expression is restricted to normal hematopoietic cells, brain, and colon tissues. Downregulation of CHK in brain and colon tumors contributes to tumorigenicity in these tissues. CHK does not phosphorylate Src efficiently, however, in contrast to CSK, CHK inhibits Src kinase activity allosterically. Although the functions of CHK are still largely unknown, potential substrates of CHK including β-synuclein, α-tubulin, α-spectrin, 14-3-3, and Hsp90 have been identified. CHK is regulated epigenetically via promoter methylation. As the unknown roles of CHK are beginning to be revealed, current knowledge of regulation, molecular targets and functions of CHK is summarized, and important topics for future CHK research are discussed.

Developing and Testing Methylated Nano-Structured Dipeptides that Inhibit Src Kinase Activity In Vitro for Anti-Cancer Applications.

Here, with the aim of developing a novel anti-cancer treatment, seven dipeptides were designed that contained methylated tryptophan and/or methylated arginine and were produced using Fmoc solid-phase peptide synthesis. Overexpression of the Src tyrosine kinase enzyme has been implicated in the development of different cancers. Dipeptides containing unnatural amino acids such as methylated arginine (RCH3), dimethylated arginine (R(CH3)2), and/or methylated tryptophan (WCH3) residues have earlier been shown to inhibit Src kinase. In this study, three such dipeptides, W-RCH3, WCH3-RCH3, and W-R(CH3)2, were tested using acellular assays and were found to have IC50 values (the concentration at which 50% inhibition occurs) of 510 nM, 916 nM, and 1 µM, respectively. These values were comparable to those obtained for cyclic penta- to nano-W-R peptides ([W-R]5-[W-R]9) synthesized in previous studies. However, the unmethylated versions of the dipeptides did not show any inhibitory activity against Src kinase. All of these dipeptides (50 µM) did not show any cytotoxicity after incubation up to 72 h with three different cancer cell lines, including leukemia (CCRF-CEM), breast adenocarcinoma (MDA-MB-231), and ovarian adenocarcinoma (SK-OV-3) cell lines, indicating the limited permeability of the peptides through the cell membrane. Therefore, further study is needed to improve the permeability of these peptides for anticancer applications, such as by using a peptide carrier or additional peptide functionalization. In summary, this study provides a protocol to synthesize and test peptides that inhibit Src kinase activity, and thus possess promising anticancer ability, as demonstrated using acellular and cellular assays.

319 (PB099) - Screening of NXP900 and dasatinib across 121 cancer cell lines identifies differences in their antiproliferative activity profiles

Background: We have recently reported that NXP900 (a.k.a. eCF506) binds and locks SRC tyrosine kinase in its ‘closed’ inactive conformation, being classified as a Type I1/2A inhibitor. This conformation-selective binding mode results in the inhibition of both SRC enzymatic activity and SRC-FAK complex formation, confers superior activity towards SRC-family kinases (SFK) and a high selectivity profile over the rest of the kinome [1,2]. This contrasts with the binding mode of dasatinib, which inhibits SRC kinase activity in its ‘open’ conformation (Type I), thus enhancing its capacity to bind to FAK.

Androgen receptor variant-7 regulation by tenascin-c induced src activation

BackgroundBone metastatic prostate cancer does not completely respond to androgen-targeted therapy and generally evolves into lethal castration resistant prostate cancer (CRPC). Expression of AR-V7- a constitutively active, ligand independent splice variant of AR is one of the critical resistant mechanisms regulating metastatic CRPC. TNC is an extracellular matrix glycoprotein, crucial for prostate cancer progression, and associated with prostate cancer bone metastases. In this study, we investigated the mechanisms that regulate AR-V7 expression in prostate cancer cells interacting with osteogenic microenvironment including TNC.MethodsProstate cancer/preosteoblast heterotypical organoids were evaluated via immunofluorescence imaging and gene expression analysis using RT-qPCR to assess cellular compartmentalization, TNC localization, and to investigate regulation of AR-V7 in prostate cancer cells by preosteoblasts and hormone or antiandrogen action. Prostate cancer cells cultured on TNC were assessed using RT-qPCR, Western blotting, cycloheximide chase assay, and immunofluorescence imaging to evaluate (1) regulation of AR-V7, and (2) signaling pathways activated by TNC. Identified signaling pathway induced by TNC was targeted using siRNA and a small molecular inhibitor to investigate the role of TNC-induced signaling activation in regulation of AR-V7. Both AR-V7- and TNC-induced signaling effectors were targeted using siRNA, and TNC expression assessed to evaluate potential feedback regulation.ResultsUtilizing heterotypical organoids, we show that TNC is an integral component of prostate cancer interaction with preosteoblasts. Interaction with preosteoblasts upregulated both TNC and AR-V7 expression in prostate cancer cells which was suppressed by testosterone but elevated by antiandrogen enzalutamide. Interestingly, the results demonstrate that TNC-induced Src activation regulated AR-V7 expression, post-translational stability, and nuclear localization in prostate cancer cells. Treatment with TNC neutralizing antibody, Src knockdown, and inhibition of Src kinase activity repressed AR-V7 transcript and protein. Reciprocally, both activated Src and AR-V7 were observed to upregulate autocrine TNC gene expression in prostate cancer cells.ConclusionOverall, the findings reveal that prostate cancer cell interactions with the cellular and ECM components in the osteogenic microenvironment plays critical role in regulating AR-V7 associated with metastatic CRPC.9BxMEZaJbqgytBg6QvviEaVideo

SRC Kinase-Mediated Tyrosine Phosphorylation of TUBB3 Regulates Its Stability and Mitotic Spindle Dynamics in Prostate Cancer Cells.

Tubulin is an integral part of the cytoskeleton and plays a pivotal role in cellular signaling, maintenance, and division. β-tubulin is also the molecular target for taxane compounds such as docetaxel (DTX) and cabazitaxel (CTX), both first-line treatments for several solid cancers. Increased expression of Class III β-tubulin (TUBB3), a primarily neural isoform of β-tubulin, correlates with taxane resistance and poor prognosis. Although tyrosine kinase c-Src has been implicated to phosphorylate β-tubulins during both hematopoietic and neural differentiation, the mechanisms by which Src modulates tubulins functions are still poorly understood. Here, we report, for the first time, that TUBB3 is phosphorylated at Tyrosine 340 (Y340) by c-SRC in prostate cancer cells. We also showed that Y340 phosphorylation regulates TUBB3 protein stability and subcellular localization. Furthermore, we demonstrated that inhibition of SRC kinase activity compromises spindle stability in mitotic cells, at least partly due to the lack of TUBB3 Y340 phosphorylation. Given the importance of TUBB3 as a clinical biomarker of poor prognosis and drug resistance, characterization of TUBB3 posttranslational regulation could potentially serve as new biomarkers for disease recurrence and/or treatment failure.

Src acts as the target of matrine to inhibit the proliferation of cancer cells by regulating phosphorylation signaling pathways

Studies have shown that matrine has antitumor activity against many types of cancers. However, the direct target in cancer cells of its anticancer effect has not been identified. The purpose of this study was to find the molecular target of matrine to inhibit the proliferation of cancer cells and explore its mechanism of action. Herein we showed that matrine inhibited the proliferation of cancer in vitro and in vivo. Pull-down assay with matrine-amino coupling resins and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) identified Src as the target of matrine. Cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) provided solid evidences that matrine directly bound to Src. Bioinformatics prediction and pull-down experiment demonstrated that Src kinase domain was required for its interaction with matrine and Ala392 in the kinase domain participated in matrine–Src interaction. Intriguingly, matrine was proven to inhibit Src kinase activity in a non-ATP-competitive manner by blocking the autophosphorylation of Tyr419 in Src kinase domain. Matrine down-regulated the phosphorylation levels of MAPK/ERK, JAK2/STAT3, and PI3K/Akt signaling pathways via targeting Src. Collectively, matrine targeted Src, inhibited its kinase activity, and down-regulated its downstream MAPK/ERK, JAK2/STAT3, and PI3K/Akt phosphorylation signaling pathways to inhibit the proliferation of cancer cells.

Development of 2′-aminospiro [pyrano[3,2–c]quinoline]-3′-carbonitrile derivatives as non-ATP competitive Src kinase inhibitors that suppress breast cancer cell migration and proliferation

Src kinase activity controls diverse cellular functions, including cell growth, migration, adhesion, and survival. It is de-regulated in several cancers, including breast cancer, where it is highly expressed and phosphorylated. Thus, targeting Src by a small molecule is a feasible strategy for managing different breast cancer types. Several Src kinase inhibitors are available, including the FDA-approved drug (dasatinib). However, they are primarily ATP-competitive inhibitors that have been reported to lack specificity towards Src. We have a long-time interest in discovering protein kinase inhibitors that are non-competitive for ATP. In this project, three groups of 2′-aminospiro[pyrano[3,2–c]quinoline]-3′-carbonitrile derivatives were designed and synthesized, hypothesizing that small molecules with a spiro scaffold appended to a pyrano[3,2–c]quinoline analog could act as non-ATP competitive Src kinase inhibitors. 3b, 3c, and 3d inhibited Src kinase activity with IC50s of 4.9, 5.9, and 0.9 μM, respectively. At the same time, they did not impact the MDM2/p53 interaction in HEK293 cells, which has been reported to be affected by some spirocyclic compounds. 25 µM of 3b, 3c, or 3d did not inhibit the kinase activity of ERK2, JNK1, or p38-alpha in an in-vitro kinase assay. Steady-state kinetic studies for the effect of 3d on the ability of recombinant Src to phosphorylate its substrate (Srctide) revealed a non-ATP competitive inhibition mechanism. 1.6 µM of 3d was enough to diminish Src, Fak, and paxillin phosphorylation in the breast cancer cell lines MDA-MB-231 and MCF7. In the NCI screening, 3d induced broad tumor cytotoxicity for the NCI-60 cell lines, including all the breast cancer cell lines. The potency of 3b, 3c, and 3d to inhibit migration, proliferation, and colony formation of MDA-MB-231 and proliferation of MCF7 cells correlates with their potency to suppress Src kinase activity in the same cell line. Noticeably, the cell growth suppression and apoptosis induction in the tested cell lines can be attributed to the ability of the new derivatives to suppress the ERK and Akt survival pathways downstream of Src.

Src-Yap1 signaling axis controls the trophectoderm and epiblast lineage differentiation in mouse embryonic stem cells

The tyrosine kinase Src is highly expressed in embryonic stem cells (ESCs) and ESC-differentiated cells, however, its functional role remains obscured. Here, we constitutivelyexpressed Src in mouse ESCs and found these cells retained comparable levels of the core pluripotent factors, such as Oct4 and Sox2, while promoted the expression of epiblast lineage markers and restrained trophoblast lineage markers compared to the control ESCs. Knockdown of Src in mouse ESCs showed the opposite effect. Directly differentiation of these ESCs to epiblast and trophoblast lineage cells revealed that Src activation dramatically accelerated the production of epiblast-like cells and inhibited the induction of trophoblast-like cells in vitro. Mechanistically, we found Src activation enhanced the Yap1-Tead interaction and their transcriptional output in mouse ESCs through specially upregulating Yap1 tyrosine phosphorylation. Subsequently, we found that overexpression of Yap1 in mouse ESCs phenocopied the differentiation patterns of Src overexpressing cells in vitro. Moreover, inhibition of Src kinase activity by Dasatinib or Yap1/Tead-mediated transcription with Verteporfin reversed the differentiation patterns of Src overexpressing ESCs. Taken together, our results unravel a novel Src-Yap1 regulatory axis during mouse ESC differentiation to trophectoderm and epiblast lineage cells in vitro.

Abstract 4017: Biochemical and biophysical characterization of a covalent inhibitor of Src kinase

Abstract Background: c-Src was among the first oncogenes discovered. It encodes a non-receptor tyrosine kinase that regulates many cancer-related cellular processes including mitogenesis, angiogenesis, adhesion, invasion, migration, and survival. Src activity drives malignant phenotypes in hematologic and solid cancers including breast, prostate, lung, colorectal, and pancreatic cancer. However, no specific Src-directed targeted therapies are in clinical use. Various Src inhibitors such as dasatinib, bosutinib and others have been tested in human trials, but with variable outcomes including dose-limiting toxicity, which is due to the multi-targeted nature of these compounds, which also hit Src, SFKs, BCR-ABL, c-KIT, PDGFR, c-FMS, EPHA2 and others. Improved selective Src inhibitors may overcome these challenges to enable Src-directed therapies. Engineering selectivity into Src inhibitors is challenging because of the high degree of sequence homology between Src family members and other receptor tyrosine kinases. The selective, covalent Src inhibitor DGY-06-116, which targets a relatively unusual targetable cysteine near the active site in the p loop, was recently reported. Here, we further characterize DGY-06-116. Methods: We characterized the inhibitory activity DGY-06-116 using an enzymatic assay and surface plasmon resonance (SPR). We also determined the co-crystal structure of DGY-06-116 bound to Src. Results: DGY-06-116 showed a substantial improvement over both SM171 and bosutinib for inhibition of Src kinase activity: SM1-71 (IC50, 26.6 nM); bosutinib (IC50, 9.5 nM); DGY-06-116 (IC50, 2.59 nM). Determination of kinact using SPR showed a value of 5.7 x 10-7 (s-1) for DGY-06-116, slower than FDA-approved neratinib (2 x 10-3 s-1) and afatinib (1 x 10-3 s-1). A 2.15 Å resolution co-crystal structure of DGY-06-116 bound to Src (PDB ID: 6E6E) showed a covalent bond with Cys-280 and bending of the p-loop relative to other Src-inhibitor structures. Conclusions: DGY-06-116 demonstrates a slow inactivation rate that likely reflects the need for repositioning of the p-loop for a covalent bond to occur. Src inhibitors based on DGY-06-116 may benefit from optimization of p-loop, inhibitor interactions. Citation Format: Deepak Gurbani, Kenneth Westover, Asim Bera. Biochemical and biophysical characterization of a covalent inhibitor of Src kinase [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4017.

Src mediates β-adrenergic receptor induced YAP tyrosine phosphorylation.

The Hippo pathway is a newly identified pathway and evolutionarily conserved from flies to humans mainly regulating cell proliferation. Transcriptional co-activator Yes-associated protein (YAP) functions as a major downstream effector and key node of the Hippo pathway. Phosphorylation of YAP is critical to regulate YAP activity and its corresponding functions. β-adrenergic receptor (β-AR), a typical G protein coupled receptor (GPCR), mediates proliferation in various cell types and regulates multiple physical and pathological processes. However, the role of β-AR in regulating YAP remains elusive. Here, we report that β-AR can obviously stimulate YAP tyrosine phosphorylation. The mechanism is that β-AR stimulation results in tyrosine kinase Src activation and Src phosphorylates YAP tyrosine at Y357. Further studies demonstrate that inhibition of Src kinase activity can obviously alleviate β-AR induced YAP tyrosine phosphorylation and cell proliferation. We conclude that β-AR can induce YAP tyrosine phosphorylation and also establish the Src/YAP pathway as a critical signaling branch downstream of GPCR.

Studies on Substituted Thienopyridine Carbonitriles as Src Inhibitors Using a Comprehensive In Silico Method

To explore the structural requirements and inhibitory mechanism of Src inhibitors, the comparative molecular field analysis, comparative molecular similarity indices analysis and three-dimensional quantitative structure-activity relationship and molecular docking of 45 substituted thienopyridine carbonitriles as tyrosine kinase pp60src inhibitors was conducted. Three three-dimensional quantitative structure-activity relationship models showed high predictabilities with cross-validated correlation coefficient and predictive correlation coefficient values of 0.793 and 0.887 for comparative molecular field analysis and 0.624 and 0.793 for comparative molecular similarity indices analysis, respectively. Docking results indicated that 4 compounds with high inhibitory activity penetrated into the active pocket of tyrosine kinase pp60src and formed stable hydrogen bonds with the binding pocket of tyrosine kinase pp60src. Leu273, Lys295, Thr338, Asp348, and Ser345 of tyrosine kinase pp60src are important residues. The results could be of great value in designing novel substituted thienopyridine carbonitriles with more potent Src kinase inhibitory activity.

MTNR1B loss promotes chordoma recurrence by abrogating melatonin-mediated β-catenin signaling repression.

Chordoma is an extremely rare malignant bone tumor with a high rate of relapse. While cancer stem cells (CSCs) are closely associated with tumor recurrence, which depend on its capacity to self-renew and induce chemo-/radioresistance, whether and how CSCs participate in chordoma recurrence remains unclear. The current study found that tumor cells in recurrent chordoma displayed more dedifferentiated CSC-like properties than those in corresponding primary tumor tissues. Meanwhile, MTNR1B deletion along with melatonin receptor 1B (MTNR1B) down-regulation was observed in recurrent chordoma. Further investigation revealed that activation of Gαi2 by MTNR1B upon melatonin stimulation could inhibit SRC kinase activity via recruiting CSK and SRC, increasing SRC Y530 phosphorylation, and decreasing SRC Y419 phosphorylation. This subsequently suppressed β-catenin signaling and stemness via decreasing β-catenin p-Y86/Y333/Y654. However, MTNR1B loss in chordoma mediated increased CSC properties, chemoresistance, and tumor progression by releasing melatonin's repression of β-catenin signaling. Clinically, MTNR1B deletion was found to correlate with patients' survival. Together, our study establishes a novel convergence between melatonin and β-catenin signaling pathways and reveals the significance of this cross talk in chordoma recurrence. Besides, we propose that MTNR1B is a potential biomarker for prediction of chordoma prognosis and selection of treatment options, and chordoma patients might benefit from targeting MTNR1B/Gαi2/SRC/β-catenin axis.

Amino alkynylisoquinoline and alkynylnaphthyridine compounds potently inhibit acute myeloid leukemia proliferation in mice.

BackgroundAcute myeloid leukemia (AML) remains one of the most lethal, rarely cured cancers, despite decades of active development of AML therapeutics. Currently, the 5-year survival of AML patients is about 30% and for elderly patients, the rate drops to <10%. About 30% of AML patients harbor an activating mutation in the tyrosine kinase domain (TKD) of Fms-Like Tyrosine kinase 3 (FLT3) or a FLT3 internal tandem duplication (FLT3-ITD). Inhibitors of FLT3, such as Rydapt that was recently approved by the FDA, have shown good initial response but patients often relapse due to secondary mutations in the FLT3 TKD, like D835Y and F691 L mutations.MethodsAlkynyl aminoisoquinoline and naphthyridine compounds were synthesized via Sonogashira coupling. The compounds were evaluated for their in vitro and in vivo effects on leukemia growth.FindingsThe compounds inhibited FLT3 kinase activity at low nanomolar concentrations. The lead compound, HSN431, also inhibited Src kinase activity. The compounds potently inhibited the viability of MV4–11 and MOLM-14 AML cells with IC50 values <1 nM. Furthermore, the viability of drug-resistant AML cells harboring the D835Y and F691 L mutations were potently inhibited. In vivo efficacy studies in mice demonstrated that the compounds could drastically reduce AML proliferation in mice.InterpretationCompounds that inhibit FLT3 and downstream targets like Src (for example HSN431) are good leads for development as anti-AML agents.FundPurdue University, Purdue Institute for Drug Discovery (PIDD), Purdue University Center for Cancer Research, Elks Foundation and NIH P30 CA023168.

Russian Experience of Bosutinib Use in Chronic Myeloid Leukemia Patients in Routine Clinical Practice

Background. The treatment of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKI) have diminished death probability and have changed the disease course. Achievement of complete cytogenetic response (CCyR) and major molecular response (MMR) are serve as warranties for freedom of progression and death from CML. There are many of CML patients are needed to change of initial TKI therapy with choice of the most efficient and safe drug for continuous life-long therapy to reach the optimal results of CML treatment. The newest of registered TKI drug in Russia is Bosutinib which has dual BCR-ABL and SRC kinase inhibitory activity and had showed good tolerability and efficacy in case of other TKIs resistance or intolerance.Aim. To analyze of own Bosutinib experience in patients with chronic myeloid leukemia with other TKIs resistance or intolerance and to make comparison with clinical trial results.Materials and methods. Clinical trials results from peer-reviewed journals. Outpatients charts of 51 patients (25 male and 26 females) with CML. Disease phase at the moment of Bosutinib therapy initiation was as follows: chronic - 37; acceleration - 8, blastic - 6. Bosutinib was used in the next lines of TKI therapy: second - 10; third - 18; fourth - 23. The indications for Bosutinib therapy were: intolerance to previous TKI - 21; resistance to previous TKI - 30.Results. Median of therapy duration was 6 months (1-50 months). The adverse events and tolerability of Bosutinib were similar with clinical trials data. The treatment was withdrawn by the adverse event only in 5 (10%) patients. The rates of the responses in the whole group of patients were as follows: CHR - 88%, stable in 76%; CCyR - 39%, stable in 37%, MMR - 31% and was 25% at the last follow-up. The Bosutinib efficacy in real life settings was slightly higher than clinical trials data. The factors influencing treatment responses were: disease phase, cause of switching to Bosutinib, line of therapy and presence and kind of BCR-ABL mutations, Therapy was continued in 22 (43%) patients, most them achieved stable optimal treatment response (CCyR and MMR).Conclusions. Bosutinib is a real alternative to other tyrosine kinase inhibitors and has its own mechanism of action and adverse events profile. The use of Bosutinib in real life clinical practice settings showed its efficacy and tolerability and could serve as base for recommendation to apply Bosutinib in hematology practice in Russia. DisclosuresNo relevant conflicts of interest to declare.

Src Kinases Regulate Glutamatergic Input to Hypothalamic Presympathetic Neurons and Sympathetic Outflow in Hypertension.

The elevated sympathetic outflow associated with hypertension is maintained by increased N-methyl-d-aspartate receptor (NMDAR) activity in the paraventricular nucleus (PVN) of the hypothalamus. Synaptic NMDAR activity is tightly regulated by protein kinases, including the Src family of tyrosine kinases. We determined whether Src kinases play a role in increased NMDAR activity of PVN neurons projecting to the rostral ventrolateral medulla and in elevated sympathetic vasomotor tone in spontaneously hypertensive rats (SHRs). The Src protein level in the PVN was significantly greater in SHRs than in normotensive Wistar-Kyoto (WKY) rats and was not significantly altered by lowering blood pressure with celiac ganglionectomy in SHRs. Inhibition of Src kinase activity with 4-amino-5-(4-chlorophenyl)-7-(dimethylethyl)pyrazolo[3,4-d]pyrimidine (PP2) completely normalized the higher amplitudes of evoked NMDAR-mediated excitatory postsynaptic currents and puff NMDA-elicited currents of rostral ventrolateral medulla-projecting PVN neurons in SHRs. PP2 treatment also attenuated the higher frequency of NMDAR-mediated miniature excitatory postsynaptic currents of these neurons in SHRs. However, PP2 had no effect on NMDAR-excitatory postsynaptic currents or miniature excitatory postsynaptic currents of rostral ventrolateral medulla-projecting PVN neurons in WKY rats. NMDAR activity increased by an Src-activating peptide was blocked by PP2 but not by inhibition of casein kinase 2. In addition, microinjection of PP2 into the PVN not only decreased lumbar sympathetic nerve discharges and blood pressure but also eliminated the inhibitory effect of the NMDAR antagonist on sympathetic nerve activity and blood pressure in SHRs. Collectively, our findings suggest that increased Src kinase activity potentiates presynaptic and postsynaptic NMDAR activity in the PVN and sympathetic vasomotor tone in hypertension.

Regulation of N-Formyl Peptide Receptor Signaling and Trafficking by Arrestin-Src Kinase Interaction.

Arrestins were originally described as proteins recruited to ligand-activated, phosphorylated G protein-coupled receptors (GPCRs) to attenuate G protein-mediated signaling. It was later revealed that arrestins also mediate GPCR internalization and recruit a number of signaling proteins including, but not limited to, Src family kinases, ERK1/2, and JNK3. GPCR-arrestin binding and trafficking control the spatial and temporal activity of these multi-protein complexes. In previous reports, we concluded that N-formyl peptide receptor (FPR)-mediated apoptosis, which occurs upon receptor stimulation in the absence of arrestins, is associated with FPR accumulation in perinuclear recycling endosomes. Under these conditions, inhibition of Src kinase and ERK1/2 prevented FPR-mediated apoptosis. To better understand the role of Src kinase in this process, in the current study we employed a previously described arrestin-2 (arr2) mutant deficient in Src kinase binding (arr2-P91G/P121E). Unlike wild type arrestin, arr2-P91G/P121E did not inhibit FPR-mediated apoptosis, suggesting that Src binding to arrestin-2 prevents apoptotic signaling. However, in cells expressing this mutant, FPR-mediated apoptosis was still blocked by inhibition of Src kinase activity, suggesting that activation of Src independent of arrestin-2 binding is involved in FPR-mediated apoptosis. Finally, while Src kinase inhibition prevented FPR-mediated-apoptosis in the presence of arr2-P91G/P121E, it did not prevent FPR-arr2-P91G/P121E accumulation in the perinuclear recycling endosome. On the contrary, inhibition of Src kinase activity mediated the accumulation of activated FPR-wild type arrestin-2 in recycling endosomes without initiating FPR-mediated apoptosis. Based on these observations, we conclude that Src kinase has two independent roles following FPR activation that regulate both FPR-arrestin-2 signaling and trafficking.