Family Protein Tyrosine Kinases Research Articles

Abstract LB-288: A highly selective small molecule CSF-1R inhibitor demonstrates strong immunomodulatory activity in syngeneic models

Abstract Introduction: CSF-1R is the receptor for Colony-Stimulating Factor 1 (CSF-1), which belongs to the type III protein tyrosine kinase family. CSF-1R signaling is critical for macrophage/myeloid-derived suppressing cells (MDSC) recruitment, proliferation, and survival. Inhibition of CSF-1R leads to the reduction and repolarization of macrophages and MDSCs in tumor microenvironment, offering potential combinatory synergy with immune-oncology checkpoint antibodies for the treatment of multiple cancers. By using state-of-art computational structure analysis and medicinal chemistry design, we have discovered a novel, highly selective, and potent small molecule CSF-1R inhibitor, ABSK-021. Method: ABSK-021 was evaluated in biochemical ADP-Glo assay and Cell-Titer Glo assay for its inhibition on CSF-1R enzymatic activity and cellular proliferation. Its selectivity against other receptor tyrosine kinases was analyzed by ELISA, cellular proliferation, and KinomeScan assays. The pharmacokinetics (PK) profile of ABSK-021 was characterized in four species of animals (mouse, rat, dog, monkey). Efficacy studies were conducted in two syngeneic models, and flow cytometry analysis was performed in tumor-bearing mice after short term dosing. Its preliminary toxicity profile was also generated by several classical safety assays. Results: ABSK-021 has potent biochemical and cellular activities against CSF-1R (IC50<30 nM), resulting in strong inhibition of CSF-1R phosphorylation and the proliferation of bone-marrow derived macrophage at low nM concentration. ABSK-021 has over 40-fold selectivity against KIT/FLT3/PDGFR-alpha/VEGFR2, which are in the same tyrosine kinase family with CSF-1R. KinomeScan also revealed its excellent selectivity against other receptor tyrosine kinases. In vivo PK study demonstrated high exposure and superior DMPK profile of ABSK-021 in mouse, rat, dog, and monkey. Efficacy studies showed that ABSK-021 strongly enhanced anti-tumor efficacy of anti-PD-1 antibody in syngeneic models. Reduction of tumor-associated macrophage and MDSC after ABSK-021 dosing was confirmed by flow cytometry analysis. Safety studies showed that ABSK-021 has no inhibition on CYP family members, hERG, and other 43 safety targets in CEREP's SafetyScreen panel (IC50>10 μM). Conclusion: ABSK-021, presented here by Abbisko Therapeutics, is a highly potent, selective, and oral-available small molecule CSF-1R inhibitor. Its superior profile supports fast-track preclinical development. Citation Format: Shuqun Yang, Baowei Zhao, Mingming Zhang, Yuan Zhao, Xin Chen, Lei Zhang, Hongping Yu, Zhui Chen, Yaochang Xu. A highly selective small molecule CSF-1R inhibitor demonstrates strong immunomodulatory activity in syngeneic models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-288.

Biphasic regulation of tumorigenesis by PTK7 expression level in esophageal squamous cell carcinoma

Protein tyrosine kinase 7 (PTK7), also known as colon carcinoma kinase 4 (CCK-4), is a member of the catalytically defective receptor protein tyrosine kinase family and is upregulated in various cancers, where it is known to act as either an oncoprotein or a tumor suppressor. To understand the contrasting roles of PTK7 in tumorigenesis, we analyzed the tumorigenic characteristics of esophageal squamous cell carcinoma (ESCC) cells with low levels of endogenous PTK7 expression (TE-5 and TE-14 cells) and high levels of expression (TE-6 and TE-10 cells) after transfections with a PTK7 expression vector. PTK7 overexpression increased the proliferation of TE-5 and TE-14 cells but decreased the proliferation of TE-6 and TE-10 cells. In the ESCC cells, proliferation, migration, and invasion were initially increased and then decreased according to PTK7 expression levels, which were mirrored by initial increases and then decreases in the tyrosine phosphorylation of cellular proteins and phosphorylation of Src, Akt, and ERK. In ESCC patients included in The Cancer Genome Atlas database, those with higher PTK7 mRNA levels had a longer overall survival and lower relative risk than those with lower PTK7 mRNA levels. These results demonstrate that PTK7 biphasically regulates tumorigenesis in ESCC.

The Role of Neuropilin-1-FYN Interaction in Odontoblast Differentiation of Dental Pulp Stem Cells.

Abnormal odontoblast differentiation of dental pulp stem cells (DPSCs) caused by inflammation is closely related to the development of dental caries. Neuropilin-1 (NRP1) is one of the members of neuropilin family. It can combine with disparate ligands involved in regulating cell differentiation. FYN belongs to the protein-tyrosine kinase family, which has been implicated in the control of cell growth, and the effect can be further strengthened by inflammatory factors. In our studies, we verified that NRP1 can form complexes with FYN and have the correlation changes in odontoblast differentiation of DPSCs. Therefore, we surmise that in the progress of dental caries, NRP1 interacts with FYN, by expanding inflammation and inhibition of odontoblast differentiation of DPSCs through nuclear factor kappa B (NF-κB) signaling pathway. In this subject, we first investigated the expression and interaction of NRP1 and FYN in DPSCs. And then, we researched the effect of this complex controlling downstream signal pathway in normal or inflammation stimulated DPSCs. Finally, we analyzed the relationship between this role and odontoblast differentiation of DPSCs. This research will provide the molecular mechanism of inflammation factors of dental caries through activating NF-κB signal regulating odontoblast differentiation in DPSCs for finding new potential drug targets for the clinical treatment of dental caries.

Mechanistic Insights into Regulation of JAK2 Tyrosine Kinase.

JAK2 is a member of the Janus kinase (JAKs) family of non-receptor protein tyrosine kinases, which includes JAK1–3 and TYK2. JAKs serve as the cytoplasmic signaling components of cytokine receptors and are activated through cytokine-mediated trans-phosphorylation, which leads to receptor phosphorylation and recruitment and phosphorylation of signal transducer and activator of transcription (STAT) proteins. JAKs are unique among tyrosine kinases in that they possess a pseudokinase domain, which is just upstream of the C-terminal tyrosine kinase domain. A wealth of biochemical and clinical data have established that the pseudokinase domain of JAKs is crucial for maintaining a low basal (absence of cytokine) level of tyrosine kinase activity. In particular, gain-of-function mutations in the JAK genes, most frequently, V617F in the pseudokinase domain of JAK2, have been mapped in patients with blood disorders, including myeloproliferative neoplasms and leukemias. Recent structural and biochemical studies have begun to decipher the molecular mechanisms that maintain the basal, low-activity state of JAKs and that, via mutation, lead to constitutive activity and disease. This review will examine these mechanisms and describe how this knowledge could potentially inform drug development efforts aimed at obtaining a mutant (V617F)-selective inhibitor of JAK2.

The Value of FAK and SLUG Expression in Patients with Breast Carcinoma and Relation of Their Expression to Clinicopathological and Prognostic Parameters

Background: Although there is marked improvement in breast carcinoma (BC) management, it is still the leading cause of cancer death in middle-aged and old females, which leads to emergence of many studies about recent prognostic biomarkers that aimed to discover new therapeutic targets for BC. Focal adhesion kinase (FAK) is a member of protein tyrosine kinase (PTK) family. Slug is a member of the Snail family that is a C2H2-type zinc-finger transcription factor and plays an essential role in Epithelialmesenchymal transition [EMT] process activation in cancer. Our study aimed: To evaluate FAK and SLUG expressions in BC, to correlate their expressions with differentiation, invasiveness, metastatic potential of such type of cancer in addition to correlation with recurrence free and overall survival rates of female patients with breast cancer. Methods: We have assessed FAK and SLUG expressions in sections from 50 paraffin blocks of breast carcinoma using immunohistochemistry. We analysed correlations between their levels of expressions, clinic-pathological and prognostic criteria of our BC patients. Results: FAK and SLUG positive expression in breast carcinoma was related to positive expression in breast carcinoma was significantly correlated with aggressive molecular subtypes as HER2 amplified and triple negative subtypes, presence of lymph node metastases, high KI67 index, presence of distant metastasis (p<0.001 for all of them), negative ER & PR (p= 0.08), The expression of both markers was significantly positively correlated with each other (p<0.001). FAK and SLUG positive expression in breast carcinoma was associated with shortened recurrence free and overall survival rates (p<0.00). Conclusion: FAK and SLUG are markers of poor prognosis of breast carcinoma patients.

Src family kinase tyrosine phosphorylates Toll-like receptor 4 to dissociate MyD88 and Mal/Tirap, suppressing LPS-induced inflammatory responses

Src family kinases (SFKs) are a family of protein tyrosine kinases containing nine members: Src, Lyn, Fgr, Hck, Lck, Fyn, Blk, Yes, and Ylk. Although SFK activation is a major immediate signaling event in LPS/Toll-like receptor 4 (TLR4) signaling, its precise role has remained elusive due to various contradictory results obtained from a certain SFK member-deficient mice or cells. The observed inconsistencies may be due to the compensation or redundancy by other SFKs upon a SFK deficiency. The chemical rescuing approach was suggested to induce temporal and precise SFK activation in living cells, thereby limiting the chance of cellular adaption to a SFK-deficient condition.Using the rescuing approach, we demonstrate that restoring SFK activity not only induces tyrosine phosphorylation of TLR4, but also inhibits LPS-induced NFκB and JNK1/2 activation and consequently suppresses LPS-induced cytokine production. TLR4 normally recruits TIR domain-containing adaptors in response to LPS, however, temporally restored SFK activation disrupts the LPS-induced association of MyD88 and Mal/Tirap with TLR4. Additionally, using kinase-dead SFK-Lyn (Y397/508F) and constitutively active SFK-Lyn (Y508F), we found that the kinase-dead SFK inhibits TLR4 tyrosine phosphorylation with reduced binding affinity to TLR4, while the kinase-active SFK strongly binds to TLR4 and promotes TLR4 tyrosine phosphorylation, suggesting that SFK kinase activity is required for TLR4 tyrosine phosphorylation and TLR4-SFK interaction.Together, our results demonstrate that SFK activation induces TLR4 tyrosine phosphorylation, consequently dissociating MyD88 and Mal/Tirap from TLR4 and inhibiting LPS-induced inflammatory responses, suggesting a negative feedback loop regulated by SFK-induced tyrosine phosphorylation in TLR4.

Dibutyltin depressed immune functions via NF-κB, and JAK/STAT signaling pathways in zebrafish (Danio rerio).

Dibutyltin (DBT) is the degradation products of TBT, which is generally considered higher toxicity than TBT in the immune system. In order to learn more about the mechanisms of immune-toxic of DBT, we exposed zebrafish (Danio rerio) to 0, 1, 10 and 100 ng/L DBT for 8 weeks. At the end of the experiment, we determined the immune parameters and immune-related genes. The results showed that with an increase in TBT dose, lysozyme activities and IgM, C3, C4 content in intestine, skin and spleen were all significantly inhibited by the DBT exposure. Fish exposed to 10 ng/L and 100 ng/L showed significantly lower lysozyme activities and IgM, C3, C4 content than those of the control group. Zebrafish exposed to 10 ng/L and 100 ng/L DBT, the mRNA transcript levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), interferon γ2 (INFγ2), nuclear factor-κB p65 (NF-kB p65), inhibitor protein-κBα (IκBα), IκB kinases β (IKKβ), Janus family of protein tyrosine kinases (JAKs) and the signal transducers and activators of transcription proteins (STATs) all increased with the DBT levels in the intestine and spleen. Those parameters showed significantly higher values in 10 ng/L and 100 ng/L than those of fish in the control group. However, no significant difference was found in IκB kinases α (IKKα) and IκB kinase γ (IKKγ) mRNA levels in the intestine and spleen. These data imply that DBT might be via suppression on IKKβ/IkBa/NF-kBp65 and JAK/STAT signaling pathways to regulate the immunity of zebrafish.

Activated proline-rich tyrosine kinase 2 regulates meiotic spindle assembly in the mouse oocyte.

Proline-rich tyrosine kinase 2 (PYK2), a member of the protein tyrosine kinase family, plays an important role in various cellular processes. PYK2 can be phosphorylated on tyrosine 402 by diverse stimuli at the cell surface, and recent studies have shown that this activated form of PYK2 is enriched in oocytes and required for fertilization. However, the subcellular localization and functions of activated PYK2 in oocytes remain elusive. In this study, we demonstrate that the localization of p-PYK2 undergoes dynamic changes during in vitro maturation of mouse oocytes. The signal of p-PYK2 is initially dispersed in the cytoplasm, but begins to decorate organized microtubules after the germinal vesicle breakdown and localizes to spindle poles at metaphase. Our data further show that p-PYK2 colocalizes with γ-tubulin from the germinal vesicle stage through the end of meiosis in mouse oocytes. Nocodazole treatment and washout experiments confirm that p-PYK2 associates with the oocyte spindle and spindle poles. Moreover, pharmacological inhibition of PYK2 activity dramatically alters the morphology of the bipolar spindle and prevents oocyte maturation. Together, these data suggest that activated PYK2 may function as a component of the microtubule organizing center to regulate spindle assembly during the meiotic process of mouse oocytes.

Knockdown of Serine Threonine Tyrosine Kinase 1 (STYK1) Inhibits the Migration and Tumorigenesis in Glioma Cells.

Pediatric glioma is a devastating brain tumor. Serine threonine tyrosine kinase 1 (STYK1) is a member of the protein tyrosine kinase family and plays a significant role in the formation of several malignant tumors. However, the expression pattern and role of STYK1 in glioma are not yet clear. The aim of this study was to investigate the role and molecular mechanism of STYK1 in glioma. The results showed that STYK1 was highly expressed in glioma cell lines. We also found that knockdown of STYK1 inhibited cell proliferation, migration, and invasion in vitro as well as tumorigenesis in vivo. Furthermore, knockdown of STYK1 significantly decreased the expression levels of phosphorylation of PI3K and Akt in glioma cells. Taken together, our data suggest that STYK1 plays an important role in the development and progression of glioma. Therefore, STYK1 may represent a novel therapeutic target for the treatment of glioma.

Abstract 2377: The AML linked Src family kinase Fgr is uncoupled from SH2 and SH3 domain regulation and drives oncogenic transformation

Abstract Fgr is a member of the Src family of non-receptor protein-tyrosine kinases, which are over-expressed and constitutively active in many human cancers. Fgr expression is restricted to myeloid hematopoietic cells and strongly upregulated in a subset of primary human AML bone marrow samples, suggesting that Fgr kinase activity may contribute to AML pathogenesis. To investigate the oncogenic potential of Fgr, we expressed the wild-type kinase in Rat-2 fibroblasts and scored transformation in soft-agar colony-forming assays. Remarkably, Fgr expression resulted in strong transforming activity, suggesting that over-expression of the kinase is sufficient to overcome regulatory control by its SH2 and SH3 domains. To test this idea, we mutated the negative regulatory tail tyrosine of Fgr. Phosphorylation of the homologous tyrosines in c-Src, Hck and other Src-family members by the regulatory kinase Csk causes intramolecular engagement of the SH2 domain to suppress kinase activity. Substitution of the Fgr tail tyrosine with phenylalanine did not further enhance the transforming or kinase activity of Fgr in Rat-2 cells, suggesting that its kinase domain is uncoupled from regulation by its non-catalytic SH3-SH2 region. To explore the regulatory mechanism further, we expressed near-full-length Fgr in insect cells, purified it to homogeneity, and confirmed that it was singly phosphorylated on its negative regulatory tail (and not the activation loop). Hydrogen-deuterium exchange mass spectrometry demonstrated that the SH3 and SH2 domains are protected from deuterium uptake as observed previously for recombinant, downregulated Hck, suggesting that they are packed against the back of the kinase domain. We then tested recombinant Fgr for sensitivity to activation in vitro using peptide ligands for the SH3 and SH2 domains, as well as a peptide that engages both domains simultaneously. Fgr kinase activity was unaffected by these peptides, providing further evidence that the kinase domain is not allosterically coupled to SH3 and SH2 control. In contrast, Hck and c-Src were both stimulated by these peptides, consistent with a domain displacement mechanism of activation described previously. Control experiments using surface plasmon resonance spectroscopy confirmed that the SH3 and SH2 domains of both Hck and Fgr bind to each of the peptide ligands with similar kinetics and affinity. Taken together, our data show that Fgr is a unique Src family member in that its kinase domain is not subject to regulatory domain control despite evidence for intramolecular interactions with the SH3 and SH2 domains. As a consequence, simple over-expression of Fgr is sufficient to induce transformation of rodent fibroblasts, unlike Hck or other Src family members. By extension, over-expression of Fgr may contribute to AML development and selective targeting of its kinase activity may be of therapeutic benefit. Citation Format: Kexin Shen, Heather R. Dorman, Haibin Shi, Ravi K. Patel, Jamie A. Moroco, John R. Engen, Thomas E. Smithgall. The AML linked Src family kinase Fgr is uncoupled from SH2 and SH3 domain regulation and drives oncogenic transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2377. doi:10.1158/1538-7445.AM2017-2377

Protein S drives oral squamous cell carcinoma tumorigenicity through regulation of AXL.

The TAM family of proto-oncogenic receptor protein tyrosine kinases, comprising of TYRO3, AXL, and MERTK, is implicated in many human cancers. Their activation leads to cancer cell proliferation, enhanced migration, invasion, and drug resistance; however how TAMs are activated in cancers is less understood. We previously showed that Protein S (PROS1) is a ligand of the TAM receptors. Here we identify PROS1 as a mediator of Oral Squamous Cell Carcinoma (OSCC) in proliferation, cell survival and migration. We demonstrate that excess PROS1 induces OSCC proliferation and migration. Conversely, blocking endogenous PROS1 expression using shRNA significantly inhibits cell proliferation and migration in culture. This inhibition was rescued by the addition of purified PROS1. Moreover, PROS1 knockdown reduced anchorage-independent growth in-vitro, reduced tumor xenograft growth in nude mice and altered their differentiation profile. Mechanistically, we identify the downregulation of AXL transcripts and protein following PROS1 knockdown. Re-introducing PROS1 rescues AXL expression both at the protein and transcriptional levels. The anti-proliferative effect of the AXL inhibitor R428 was significantly reduced following PROS1 inhibition, indicating the functional significance of PROS1-mediated regulation of AXL in OSCC. Taken together, we identify PROS1 as a driver of OSCC tumor growth and a modulator of AXL expression. Our results point to PROS1 as a potential novel anti-cancer therapeutic target.

MA17.10 YES1 Kinase is a New Therapeutic Target in Non-small Cell Lung Cancer

Next-generation sequencing techniques have allowed the discovery of driver mutations in non-small cell lung cancer (NSCLC) that can be translated into advances in cancer diagnosis and treatment. However, specific oncogenic alterations are still unknown in a high proportion of NSCLC patients that therefore cannot benefit from targeted therapies. The challenge is to identify new genetic alterations that allow the use of molecular-targeted therapies. In previous studies from our group (Aramburu et al. BMC Genomics 2015), the analysis of tumor molecular profiles from patients with NSCLC allowed us to identify the DNA copy number amplification of YES1 kinase (v-YES-1 Yamaguchi sarcoma viral oncogene homolog 1) as a prognostic marker in lung cancer. YES1 kinase is member of the Src family of non-receptor protein tyrosine kinases that are involved in the regulation of cell growth, apoptosis, cell-cell adhesion, cytoskeleton remodeling, and differentiation. The aim of this project is to evaluate if YES1 is a driver gene in NSCLC, and if targeting its activation may be a potential new therapeutic strategy. We first evaluated the prognostic role of YES1 protein expression in two independent series of 76 and 234 NSCLC patients, respectively. In both series, the multivariate analysis revealed that high YES1 expression is an independent poor prognostic factor for overall survival (CUN series HR: 3.416 [0.933-12.508]; MD Anderson series HR: 1.570 [1.032-2.391]). We next evaluated the effect of YES1 knockdown in 5 NSCLC cell lines with YES1 amplification and overexpression, and in 3 cell lines without YES1 amplification and with low protein expression. YES1 downregulation by two specific siRNAs decreased proliferation and cell survival only in those cells overexpressing YES1. Congruently, YES1 inhibition led to apoptosis only in those cells. Consistent with these results, constitutive overexpression of YES1 in cells with low YES1 expression significantly enhanced cell proliferation. We next evaluated the effect of the multi-target Src kinase inhibitor dasatinib on the proliferation of NSCLC cell lines with high (8 cell lines) or low (4 cell lines) YES1 expression. Dasatinib dramatically inhibited proliferation in high YES1-expressing cell lines, whereas low YES1 cell lines were more resistant to dasatinib treatment (GI50s were four orders of magnitude higher in resistant cells). In conclusion, our results indicate that YES1 is a promising therapeutic target in NSCLC. Furthermore, amplification and high expression of YES1 may define a subset of patients who may potentially benefit from dasatinib treatment.

TAM receptor signaling in development.

TYRO3, AXL and MERTK comprise the TAM family of receptor protein tyrosine kinases. Activated by their ligands, protein S (PROS1) and growth-arrest-specific 6 (GAS6), they mediate numerous cellular functions throughout development and adulthood. Expressed by a myriad of cell types and tissues, they have been implicated in homeostatic regulation of the immune, nervous, vascular, bone and reproductive systems. The loss-of-function of TAM signaling in adult tissues culminates in the destruction of tissue homeostasis and diseased states, while TAM gain-of-function in various tumors promotes cancer phenotypes. Combinatorial ligand-receptor interactions may elicit different molecular and cellular responses. Many of the TAM regulatory functions are essentially developmental, taking place both during embryogenesis and postnatally. This review highlights current knowledge on the role of TAM receptors and their ligands during these developmental processes in the immune, nervous, vascular and reproductive systems.

EphA3 promotes malignant transformation of colorectal epithelial cells by upregulating oncogenic pathways

Ephrin Type-A Receptor 3 (EphA3) belongs to the ephrin receptor subfamily of the protein tyrosine kinase family, and plays an important role in embryogenesis and neurogenesis. This study aimed to investigate the role of EphA3 in promoting malignant transformation of colorectal epithelial cells, and explore underlying molecular mechanisms. Colorectal cancer tissue specimens from 68 patients were analyzed for EphA3 expression. EphA3 expression levels were manipulated in rat colon epithelial cell lines. We found that EphA3 expression level in tumor tissues was associated with patient age (P = 0.015), tumor differentiation (P = 0.001), and lymph node metastasis (P = 0.039). Overexpression of EphA3 and its constitutively active mutants promoted colony formation, migration and invasion, and tumorigenicity of colon epithelial cells in nude mice. The cDNA and lncRNA microarray profiling data revealed that differentially expressed genes and lncRNAs in EphA3 or mutant-transfected cells were associated with cell proliferation, invasion and angiogenesis. Our findings reveal the mechanisms underlying the oncogenic activities of EphA3 in colorectal cells, which could provide novel targets for the prevention, early diagnosis, and treatment of colorectal cancer.

Catalytically defective receptor protein tyrosine kinase PTK7 enhances invasive phenotype by inducing MMP-9 through activation of AP-1 and NF-κB in esophageal squamous cell carcinoma cells.

Protein tyrosine kinase 7 (PTK7), a member of the catalytically defective receptor protein tyrosine kinase family, is upregulated in various cancers including esophageal squamous cell carcinoma (ESCC). Here, we have explored the molecular mechanism of PTK7-dependent invasiveness in ESCC cells. PTK7 knockdown reduced gelatin degradation and MMP-9 secretion in cultures of ESCC TE-10 cells, and showed reduced levels of MMP9 mRNA using real-time RT-PCR and luciferase reporter assays. PTK7 knockdown decreased not only phosphorylation of NF-κB, IκB, ERK, and JNK, but also nuclear localization of NF-κB and AP-1 consisting of c-Fos and c-Jun. Activation of AP-1 and NF-κB requires PTK7-mediated activation of tyrosine kinases, including Src. In addition, NF-κB activation by PTK7 involves the PI3K/Akt signaling pathway. PTK7-mediated upregulation of MMP9 was also observed in other ESCC cell lines and in three-dimensional cultures of TE-10 cells. Moreover, MMP-9 expression positively correlated with PTK7 expression in ESCC tumor tissue. These findings demonstrate that PTK7 upregulates MMP9 through activation of AP-1 and NF-κB and, thus increases invasive properties of ESCC cells.

Canonical and Non-canonical Reelin Signaling.

Reelin is a large secreted glycoprotein that is essential for correct neuronal positioning during neurodevelopment and is important for synaptic plasticity in the mature brain. Moreover, Reelin is expressed in many extraneuronal tissues; yet the roles of peripheral Reelin are largely unknown. In the brain, many of Reelin’s functions are mediated by a molecular signaling cascade that involves two lipoprotein receptors, apolipoprotein E receptor-2 (Apoer2) and very low density-lipoprotein receptor (Vldlr), the neuronal phosphoprotein Disabled-1 (Dab1), and members of the Src family of protein tyrosine kinases as crucial elements. This core signaling pathway in turn modulates the activity of adaptor proteins and downstream protein kinase cascades, many of which target the neuronal cytoskeleton. However, additional Reelin-binding receptors have been postulated or described, either as coreceptors that are essential for the activation of the “canonical” Reelin signaling cascade involving Apoer2/Vldlr and Dab1, or as receptors that activate alternative or additional signaling pathways. Here we will give an overview of canonical and alternative Reelin signaling pathways, molecular mechanisms involved, and their potential physiological roles in the context of different biological settings.

Tofacitinib in ulcerative colitis.

Cytokines orchestrate immune and inflammatory responses involved in the pathogenesis of ulcerative colitis (UC). Protein kinases are essential for signal transduction in eukaryotic cells. Janus kinases (JAKs) are a family of protein tyrosine kinases that play a pivotal role in cytokine receptor signaling. Indeed, a major subgroup of cytokines use Type I and II cytokine receptors which signal via the activation of JAKs. Tofacitinib is an oral JAK inhibitor that has been studied in autoimmune pathologies, including UC and rheumatoid arthritis with good overall efficacy and acceptable safety profile. This literature review was performed with the goal of summarizing the knowledge on JAK inhibitors in UC treatment.

Identification of Potential Off-Targets of Chemotherapeutic Agent Sorafenib: A Molecular Docking Approach

B-Raf is a multi- drug target serine/threonine protein kinase, involved in the transduction of mitogenic signals from the cell membrane to the nucleus. Mutated B-Raf causes overactive downstream signaling via MEK and ERK, leading to excessive cell proliferation and survival, independent of growth factors causing cancers such as Pancreatic carcinoma. A novel bi-aryl urea- Sorafenib, is a potent inhibitor of Raf-1 that has been approved for the treatment of a number of cancers including pancreatic cancer. The present investigation was designed to identify the potential off-targets of Sorafenib which could be responsible for its reported undesirable side effects. Molecular docking was used to test the efficacy of structural analogs of Sorafenib against B-Raf using FlexX and it was found that the analog with CID:10151557 had a high potency with minimum number of clashes, low lipophilic score and high match score, similar to Sorafenib. To identify the potential off-target/s of Sorafenib, macromolecular surface similarity detection software MEDIT SA MED-SuMo was used and the results obtained were validated through literature. The possible off-targets obtained belonged to the family of protein tyrosine kinases i.e. VEGFR-2, VEGFR-3, platelet-derived growth factor receptor beta, Flt-3, and c-KIT, each of which were docked with Sorafenib. Based on high docking scores and similarity with B-Raf for its binding site interacting residues, it was concluded that Vascular endothelial growth factor tyrosine kinase receptor (VEGFR) is a potential off-target of anti-cancer chemotherapeutic agent Sorafenib.

Identification of Potential Off-Targets of Chemotherapeutic Agent Sorafenib: A Molecular Docking Approach

B-Raf is a multi- drug target serine/threonine protein kinase, involved in the transduction of mitogenic signals from the cell membrane to the nucleus. Mutated B-Raf causes overactive downstream signaling via MEK and ERK, leading to excessive cell proliferation and survival, independent of growth factors causing cancers such as Pancreatic carcinoma. A novel bi-aryl urea- Sorafenib, is a potent inhibitor of Raf-1 that has been approved for the treatment of a number of cancers including pancreatic cancer. The present investigation was designed to identify the potential off-targets of Sorafenib which could be responsible for its reported undesirable side effects. Molecular docking was used to test the efficacy of structural analogs of Sorafenib against B-Raf using FlexX and it was found that the analog with CID:10151557 had a high potency with minimum number of clashes, low lipophilic score and high match score, similar to Sorafenib. To identify the potential off-target/s of Sorafenib, macromolecular surface similarity detection software MEDIT SA MED-SuMo was used and the results obtained were validated through literature. The possible off-targets obtained belonged to the family of protein tyrosine kinases i.e. VEGFR-2, VEGFR-3, platelet-derived growth factor receptor beta, Flt-3, and c-KIT, each of which were docked with Sorafenib. Based on high docking scores and similarity with B-Raf for its binding site interacting residues, it was concluded that Vascular endothelial growth factor tyrosine kinase receptor (VEGFR) is a potential off-target of anti-cancer chemotherapeutic agent Sorafenib.

Development of REDX05194, a Novel, Potent and Selective Inhibitor of Bruton's Tyrosine Kinase (BTK) As a Potential Treatment for B-Cell Malignancies

The B-cell receptor (BCR) signaling pathway is required for the survival, activation, proliferation and differentiation of B-cells. Bruton's Tyrosine Kinase (BTK) is a member of the Tec protein tyrosine kinase family that has emerged as an attractive target for the treatment of B-cell malignancies due to the critical role it plays in BCR signaling. Redx Oncology has developed novel differentiated small molecule inhibitors of BTK, combining current best-in-class potency with distinct selectivity profiles, which are suitable for oral once daily dosing. Here we present REDX05194, the result of a successful lead optimization of our proprietary BTK inhibitor series.REDX05194 is a highly selective, covalent BTK inhibitor displaying subnanomolar binding affinity for BTK (0.39 nM) and nanomolar potency towards BTK in a biochemical assay (3.67 nM). In cell proliferation assays, REDX05194 showed significant in vitro potency against ABC-DLBCL cell lines inhibiting the growth of both TMD-8 (0.89 nM) and OCI-Ly10 (1.36 nM) cells. Analysis of BCR signaling in several lymphoma cell lines, including cell lines of ABC-DLBCL, MCL and FL origin, revealed that treatment with REDX05194 inhibits BTK autophosphorylation and downstream activation of PLCγ2. In human PBMCs, REDX05194 inhibited anti-IgM stimulated upregulation of the CD69 activation marker in CD19 positive B-cells. In addition, using a fluorescent probe that binds to BTK, occupancy of BTK in PBMCs has been demonstrated in response to increasing concentrations of REDX05194.To assess selectivity, 456 kinases were screened at 1 μM, confirming that REDX05194 does not significantly inhibit other kinases involved in BCR signaling (e.g. Syk, Lyn). Furthermore, REDX05194 was shown to have high selectivity versus structurally related cysteine-containing kinases such as ITK in binding assays, and EGFR as demonstrated in both binding and cellular assays. REDX05194 also has a favorable in vitro safety profile and drug-like properties, displaying an improved CYP profile and solubility compared to competitor compounds.REDX05194 demonstrated in vivo efficacy in a mouse collagen-induced arthritis (CIA) model. At 10 mg/kg and 30 mg/kg QD, REDX05194 significantly improved all clinical readouts, including disease severity, compared to the vehicle group. Histological data showed that approximately 1/3 of the mice had no or minimal pannus infiltration and no bone resorption, or had bone resorption restricted to small areas. These findings demonstrate potential clinical efficacy and a dose response.In conclusion, REDX05194 is a highly selective and potent BTK inhibitor with proven efficacy in several lymphoma cell lines and human PBMCs and in vivo efficacy demonstrated in a mouse CIA model. DisclosuresNo relevant conflicts of interest to declare.