Pim-1 Ligand-bound Structures Reveal the Mechanism of Serine/Threonine Kinase Inhibition by LY294002

PI3 kinase inhibitor PI828 uncouples aminergic GPCRs and Ca2+ mobilization irrespectively of its primary target

The phosphoinositide 3-kinase (PI3K) is involved in regulation of multiple intracellular processes. Although the inhibitory analysis is generally employed for validating a physiological role of PI3K, increasing body of evidence suggests that PI3K inhibitors can exhibit PI3K-unrelated activity as well. Here we studied Ca2+ signaling initiated by aminergic agonists in a variety of different cells and analyzed effects of the PI3K inhibitor PI828 on cell responsiveness. It turned out that PI828 inhibited Ca2+ transients elicited by acetylcholine (ACh), histamine, and serotonin, but did not affect Ca2+ responses to norepinephrine and ATP. Another PI3K inhibitor wortmannin negligibly affected Ca2+ signaling initiated by any one of the tested agonists. Using the genetically encoded PIP3 sensor PH(Akt)-Venus, we confirmed that both PI828 and wortmannin effectively inhibited PI3K and ascertained that this kinase negligibly contributed to ACh transduction. These findings suggested that PI828 inhibited Ca2+ responses to aminergic agonists tested, involving an unknown cellular mechanism unrelated to the PI3K inhibition. Complementary physiological experiments provided evidence that PI828 could inhibit Ca2+ signals induced by certain agonists, by acting extracellularly, presumably, through their surface receptors. For the muscarinic M3 receptor, this possibility was verified with molecular docking and molecular dynamics. As demonstrated with these tools, wortmannin could be bound in the extracellular vestibule at the muscarinic M3 receptor but this did not preclude binding of ACh to the M3 receptor followed by its activation. In contrast, PI828 could sterically block the passage of ACh into the allosteric site, preventing activation of the muscarinic M3 receptor.

A review on structure-function mechanism and signaling pathway of serine/threonine protein PIM kinases as a therapeutic target

The proviral integration for the Moloney murine leukemia virus (PIM) kinases, belonging to serine/threonine kinase family, have been found to be overexpressed in various types of cancers, such as prostate, breast, colon, endometrial, gastric, and pancreatic cancer. The three isoforms PIM kinases i.e., PIM1, PIM2, and PIM3 share a high degree of sequence and structural similarity and phosphorylate substrates controlling tumorigenic phenotypes like proliferation and cell survival. Targeting short-lived PIM kinases presents an intriguing strategy as in vivo knock-down studies result in non-lethal phenotypes, indicating that clinical inhibition of PIM might have fewer adverse effects. The ATP binding site (hinge region) possesses distinctive attributes, which led to the development of novel small molecule scaffolds that target either one or all three PIM isoforms. Machine learning and structure-based approaches have been at the forefront of developing novel and effective chemical therapeutics against PIM in preclinical and clinical settings, and none have yet received approval for cancer treatment. The stability of PIM isoforms is maintained by PIM kinase activity, which leads to resistance against PIM inhibitors and chemotherapy; thus, to overcome such effects, PIM proteolysis targeting chimeras (PROTACs) are now being developed that specifically degrade PIM proteins. In this review, we recapitulate an overview of the oncogenic functions of PIM kinases, their structure, function, and crucial signaling network in different types of cancer, and the potential of pharmacological small-molecule inhibitors. Further, our comprehensive review also provides valuable insights for developing novel antitumor drugs that specifically target PIM kinases in the future. In conclusion, we provide insights into the benefits of degrading PIM kinases as opposed to blocking their catalytic activity to address the oncogenic potential of PIM kinases.

Role of PIM Kinase Inhibitor in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative disorder, is the most prevalent form of senile dementia, causing progressive deterioration of cognition, behavior, and rational skills. Neuropathologically, AD is characterized by two hallmark proteinaceous aggregates: amyloid beta (Aβ) plaques and neurofibrillary tangles (NFTs) formed of hyperphosphorylated tau. A significant study has been done to understand how Aβ and/or tau accumulation can alter signaling pathways that affect neuronal function. A conserved protein kinase known as the mammalian target of rapamycin (mTOR) is essential for maintaining the proper balance between protein synthesis and degradation. Overwhelming evidence shows mTOR signaling's primary role in age-dependent cognitive decline and the pathogenesis of AD. Postmortem human AD brains consistently show an upregulation of mTOR signaling. Confocal microscopy findings demonstrated a direct connection between mTOR and intraneuronal Aβ42 through molecular processes of PRAS40 phosphorylation. By attaching to the mTORC1 complex, PRAS40 inhibits the activity of mTOR. Furthermore, inhibiting PRAS40 phosphorylation can stop the Aβ-mediated increase in mTOR activity, indicating that the accumulation of Aβ may aid in PRAS40 phosphorylation. Physiologically, PRAS40 is phosphorylated by PIM1 which is a serine/threonine kinase of proto-oncogene PIM kinase family. Pharmacological inhibition of PIM1 activity prevents the Aβ-induced mTOR hyperactivity in vivo by blocking PRAS40 phosphorylation and restores cognitive impairments by enhancing proteasome function. Recently identified small-molecule PIM1 inhibitors have been developed as potential therapeutic to reduce AD-neuropathology. This comprehensive study aims to address the activity of PIM1 inhibitor that has been tested for the treatment of AD, in addition to the pharmacological and structural aspects of PIM1.

Synthesis, kinase inhibition and anti-leukemic activities of diversely substituted indolopyrazolocarbazoles

Pyrazole analogues of the staurosporine aglycone K252c, in which the lactam ring was replaced by a pyrazole moiety, were synthesized. In this series, one or the other nitrogen atoms of the indolocarbazole scaffold was substituted by aminoalkyl chains, aiming at improving protein kinase inhibition as well as cellular potency toward acute myeloid leukemia (AML) cell lines. Compound 19a, substituted at the N12-position by a 3-(methylamino)propyl group, showed high cellular activity in the low micromolar range toward three AML cell lines (MOLM-13, OCI-AML3 and MV4-11) with selectivity over non-cancerous cells (NRK, H9c2). 19a is also a highly potent inhibitor of the three Pim kinase isoforms, Pim-3 being the most inhibited with an IC50 value in the nanomolar range. A selectivity screening toward a panel of 50 protein kinases showed that 19a also potently inhibited PRK2 and to a lower extent AMPK, MARK3, GSK3β and JAK3. Our results enhance the understanding of the structural characteristics of indolopyrazolocarbazoles essential for potent protein kinase inhibition with therapeutic potential against AML.

Synthesis of novel bioactive pyrido[2,3-d]pyrimidine derivatives with potent cytotoxicity through apoptosis as PIM-1 kinase inhibitors

Direct synthesis and cytotoxicity activity of new series of pyrido[2,3-d]pyrimidine was described. Nicotinamide 2 was synthesized via cyclization of N-cyclohexyl derivative with cyanoacetamide. The o-aminonicotinonitrile 2 was subjected to acylation or thio acylation process followed by intramolecular heterocyclization to afford the desired pyrido[2,3-d]pyrimidine (3-10) and pyrido triazine 11. Compounds 4 and 11 exhibited remarkable cytotoxicity against MCF-7 cells with IC50 values of 0.57 μM and 1.31 μM and IC50 values of 1.13 μM and 0.99 μM against HepG2 cells. Interestingly, compounds 4 and 10 had potent PIM-1 kinase inhibition with IC50 values of 11.4 and 17.2 nM, respectively, with inhibition of 97.8% and 94.6% compared to staurosporine (IC50 = 16.7 nM, with 95.6% inhibition). Moreover, compound 4 significantly activated apoptosis in MCF-7 cells, increasing the cell apoptosis by 58.29-fold by having 36.14% total apoptosis in treated cells compared to 0.62% for control. Moreover, it arrested the cell cycle at the G1 phase. PIM-1 kinase inhibition was virtually elucidated by the molecular docking study, highlighting binding interactions of the lead compound 4 towards the PIM-1 protein. Accordingly, compound 4 was validated as a promising PIM-1 targeted chemotherapeutic agent to treat breast cancer.

Design, synthesis and cytotoxic evaluation of novel bis-thiazole derivatives as preferential Pim1 kinase inhibitors with in vivo and in silico study

Bis-thiazole derivatives were synthesised conforming to the Pim1 pharmacophore model following Hantzsch condensation. Pim1 has a major role in regulating the G1/S phase which upon inhibition the cell cycle stops at its early stages. Derivatives 3b and 8b showed the best Pim1 IC₅₀ 0.32 and 0.24 µM, respectively relative to staurosporine IC₅₀ 0.36 µM. Further confirmation of 3b and 8b Pim1 inhibition was implemented by hindering the T47D cell cycle at G0/G1 and S phases where 3b showed 66.5% cells accumulation at G0/G1 phase while 8b demonstrated 26.5% cells accumulation at the S phase compared to 53.9% and 14.9% of a control group for both phases, respectively. Additional in vivo cytotoxic evaluation of 3b and 8b revealed strong antitumor activity with up-regulation of caspase-3 and down-regulation of VEGF and TNF α immune expression with concomitant elevation of malondialdehyde levels in case of 8b.

Pim Kinases: Important Regulators of Cardiovascular Disease

Pim Kinases; Pim-1, Pim-2, and Pim-3, are a family of constitutively active serine/threonine kinases, widely associated with cell survival, proliferation, and migration. Historically considered to be functionally redundant, independent roles for the individual isoforms have been described. Whilst most established for their role in cancer progression, there is increasing evidence for wider pathological roles of Pim kinases within the context of cardiovascular disease, including inflammation, thrombosis, and cardiac injury. The Pim kinase isoforms have widespread expression in cardiovascular tissues, including the heart, coronary artery, aorta, and blood, and have been demonstrated to be upregulated in several co-morbidities/risk factors for cardiovascular disease. Pim kinase inhibition may thus be a desirable therapeutic for a multi-targeted approach to treat cardiovascular disease and some of the associated risk factors. In this review, we discuss what is known about Pim kinase expression and activity in cells of the cardiovascular system, identify areas where the role of Pim kinase has yet to be fully explored and characterised and review the suitability of targeting Pim kinase for the prevention and treatment of cardiovascular events in high-risk individuals.

Phosphoproteomics Profiling Defines a Target Landscape of the Basophilic Protein Kinases AKT, S6K, and RSK in Skeletal Myotubes

Phosphorylation-dependent signal transduction plays an important role in regulating the functions and fate of skeletal muscle cells. Central players in the phospho-signaling network are the protein kinases AKT, S6K, and RSK as part of the PI3K-AKT-mTOR-S6K and RAF-MEK-ERK-RSK pathways. However, despite their functional importance, knowledge about their specific targets is incomplete because these kinases share the same basophilic substrate motif RxRxxp[ST]. To address this, we performed a multifaceted quantitative phosphoproteomics study of skeletal myotubes following kinase inhibition. Our data corroborate a cross talk between AKT and RAF, a negative feedback loop of RSK on ERK, and a putative connection between RSK and PI3K signaling. Altogether, we report a kinase target landscape containing 49 so far unknown target sites. AKT, S6K, and RSK phosphorylate numerous proteins involved in muscle development, integrity, and functions, and signaling converges on factors that are central for the skeletal muscle cytoskeleton. Whereas AKT controls insulin signaling and impinges on GTPase signaling, nuclear signaling is characteristic for RSK. Our data further support a role of RSK in glucose metabolism. Shared targets have functions in RNA maturation, stability, and translation, which suggests that these basophilic kinases establish an intricate signaling network to orchestrate and regulate processes involved in translation.

Duplicate genes as sources for rapid adaptive evolution of sperm under environmental pollution in tree sparrow

Environmental pollution can result in poor sperm quality either directly or indirectly in birds. However, adaptive and compensatory sperm morphology changes and motility improvements have rapidly evolved in tree sparrows (Passer montanus) inhabiting polluted areas over the past 65 years. To identify the genetic underpinnings of the rapidly evolving sperm phenotype, we carried out population genomics and transcriptomics on tree sparrow populations in the two differently polluted places. We identified a gene encoding the serine/threonine protein kinase PIM1, which may drive rapid phenotypic evolution of sperm. An unprecedented and remarkable expansion of the PIM gene family, caused by tandem and segmental duplication of PIM1, was subsequently observed in the tree sparrow genome. Most PIM1 duplicates showed a testis-specific expression pattern, suggesting that their functions are related to male reproduction. Furthermore, the elevated expression level of PIM1 was consistent with our earlier findings of longer and faster swimming sperm in polluted sites, indicating an important role for duplicated PIM1 in facilitating the rapid evolution of sperm. Our results suggest that duplicated PIM1 provides sources of genetic variation that may enable the rapid evolution of sperm under environmental heavy metal pollution. The findings of this study indicated that duplicated genes can be targets of selection and predominant sources for rapid adaptation to environmental change and shed light on sperm evolution under pollution stress.

Recent Research Advances in Small-Molecule Pan-PIM Inhibitors

PIM kinase is consequently emerging as a promising target for cancer therapeutics and immunomodulation. PIM kinases are overexpressed in a variety of hematological malignancies and solid tumors, and their inhibition has become a strong therapeutic interest. Currently, some pan-PIM kinase inhibitors are being developed under different phases of clinical trials. Based on the different scaffold structures, they can be classified into various subclasses. The X-ray structure of the kinase complex outlines the rationale of hit compound confirmation in the early stage. Structure–activity relationships allow us to rationally explore chemical space and further optimize multiple physicochemical and biological properties. This review focuses on the discovery and development of small-molecule pan-PIM kinase inhibitors in the current research, and hopes to provide guidance for future exploration of the inhibitors.

Targeting Echinococcus multilocularis PIM kinase for improving anti-parasitic chemotherapy

BACKGROUND

The potentially lethal zoonosis alveolar echinococcosis (AE) is caused by the metacestode larval stage of the tapeworm Echinococcus multilocularis. Current AE treatment options are limited and rely on surgery as well as on chemotherapy involving benzimidazoles (BZ). BZ treatment, however, is mostly parasitostatic only, must be given for prolonged time periods, and is associated with adverse side effects. Novel treatment options are thus urgently needed.

METHODOLOGY/PRINCIPAL FINDINGS

By applying a broad range of kinase inhibitors to E. multilocularis stem cell cultures we identified the proto-oncogene PIM kinase as a promising target for anti-AE chemotherapy. The gene encoding the respective E. multilocularis ortholog, EmPim, was characterized and in situ hybridization assays indicated its expression in parasite stem cells. By yeast two-hybrid assays we demonstrate interaction of EmPim with E. multilocularis CDC25, indicating an involvement of EmPim in parasite cell cycle regulation. Small molecule compounds SGI-1776 and CX-6258, originally found to effectively inhibit human PIM kinases, exhibited detrimental effects on in vitro cultured parasite metacestode vesicles and prevented the formation of mature vesicles from parasite stem cell cultures. To improve compound specificity for EmPim, we applied a high throughput in silico modelling approach, leading to the identification of compound Z196138710. When applied to in vitro cultured metacestode vesicles and parasite cell cultures, Z196138710 proved equally detrimental as SGI-1776 and CX-6258 but displayed significantly reduced toxicity towards human HEK293T and HepG2 cells.

CONCLUSIONS/SIGNIFICANCE

Repurposing of kinase inhibitors initially designed to affect mammalian kinases for helminth disease treatment is often hampered by adverse side effects of respective compounds on human cells. Here we demonstrate the utility of high throughput in silico approaches to design small molecule compounds of higher specificity for parasite cells. We propose EmPim as a promising target for respective approaches towards AE treatment.

PIM1/STAT3 axis: a potential co-targeted therapeutic approach in triple-negative breast cancer

Triple-negative breast cancer lacks an expression of ER, PR, and Her-2, has a poor prognosis, and there are no target therapies available. Therapeutic options to treat TNBC are limited and urgently needed. Strong evidence indicates that molecular signaling pathways have a significant function to regulate biological mechanisms and their abnormal expression endows with the development of cancer. PIM kinase is overexpressed in various human cancers including TNBC which is regulated by various signaling pathways that are crucial for cancer cell proliferation and survival and also make PIM kinase as an attractive drug target. One of the targets of the STAT3 signaling pathway is PIM1 that plays a key role in tumor progression and transformation. In this review, we accumulate the current scenario of the PIM-STAT3 axis that provides insights into the PIM1 and STAT3 inhibitors which can be developed as potential co-inhibitors as prospective anticancer agents.

Strategies for Improving Photodynamic Therapy Through Pharmacological Modulation of the Immediate Early Stress Response

Photodynamic therapy (PDT) is a minimally to noninvasive treatment modality that has emerged as a promising alternative to conventional cancer treatments. PDT induces hyperoxidative stress and disrupts cellular homeostasis in photosensitized cancer cells, resulting in cell death and ultimately removal of the tumor. However, various survival pathways can be activated in sublethally afflicted cancer cells following PDT. The acute stress response is one of the known survival pathways in PDT, which is activated by reactive oxygen species and signals via ASK-1 (directly) or via TNFR (indirectly). The acute stress response can activate various other survival pathways that may entail antioxidant, pro-inflammatory, angiogenic, and proteotoxic stress responses that culminate in the cancer cell's ability to cope with redox stress and oxidative damage. This review provides an overview of the immediate early stress response in the context of PDT, mechanisms of activation by PDT, and molecular intervention strategies aimed at inhibiting survival signaling and improving PDT outcome.

Macrocyclization as a Source of Desired Polypharmacology. Discovery of Triple PI3K/mTOR/PIM Inhibitors

The PI3K/AKT/mTOR and PIM kinase pathways contribute to the development of several hallmarks of cancer. Cotargeting of these pathways has exhibited promising synergistic therapeutic effects in liquid and solid tumor types. To identify molecules with combined activities, we cross-screened our collection of PI3K/(±mTOR) macrocycles (MCXs) and identified the MCX thieno[3,2-d]pyrimidine derivative 2 as a moderate dual PI3K/PIM-1 inhibitor. We report the medicinal chemistry exploration and biological characterization of a series of thieno[3,2-d]pyrimidine MCXs, which led to the discovery of IBL-302 (31), a potent, selective, and orally bioavailable triple PI3K/mTOR/PIM inhibitor. IBL-302, currently in late preclinical development (AUM302), has recently demonstrated efficacy in neuroblastoma and breast cancer xenografts. Additionally, during the course of our experiments, we observed that macrocyclization was essential to obtain the desired multitarget profile. As a matter of example, the open precursors 35-37 were inactive against PIM whereas MCX 28 displayed low nanomolar activity.

PIM1 Inhibition Affects Glioblastoma Stem Cell Behavior and Kills Glioblastoma Stem-like Cells

Despite comprehensive therapy and extensive research, glioblastoma (GBM) still represents the most aggressive brain tumor in adults. Glioma stem cells (GSCs) are thought to play a major role in tumor progression and resistance of GBM cells to radiochemotherapy. The PIM1 kinase has become a focus in cancer research. We have previously demonstrated that PIM1 is involved in survival of GBM cells and in GBM growth in a mouse model. However, little is known about the importance of PIM1 in cancer stem cells. Here, we report on the role of PIM1 in GBM stem cell behavior and killing. PIM1 inhibition negatively regulates the protein expression of the stem cell markers CD133 and Nestin in GBM cells (LN-18, U-87 MG). In contrast, CD44 and the astrocytic differentiation marker GFAP were up-regulated. Furthermore, PIM1 expression was increased in neurospheres as a model of GBM stem-like cells. Treatment of neurospheres with PIM1 inhibitors (TCS PIM1-1, Quercetagetin, and LY294002) diminished the cell viability associated with reduced DNA synthesis rate, increased caspase 3 activity, decreased PCNA protein expression, and reduced neurosphere formation. Our results indicate that PIM1 affects the glioblastoma stem cell behavior, and its inhibition kills glioblastoma stem-like cells, pointing to PIM1 targeting as a potential anti-glioblastoma therapy.

Therapeutic targeting of PIM KINASE signaling in cancer therapy: Structural and clinical prospects

BACKGROUND

PIM kinases are well-studied drug targets for cancer, belonging to Serine/Threonine kinases family. They are the downstream target of various signaling pathways, and their up/down-regulation affects various physiological processes. PIM family comprises three isoforms, namely, PIM-1, PIM-2, and PIM-3, on alternative initiation of translation and they have different levels of expression in different types of cancers. Its structure shows a unique ATP-binding site in the hinge region which makes it unique among other kinases.

SCOPE OF REVIEW

PIM kinases are widely reported in hematological malignancies along with prostate and breast cancers. Currently, many drugs are used as inhibitors of PIM kinases. In this review, we highlighted the physiological significance of PIM kinases in the context of disease progression and therapeutic targeting. We comprehensively reviewed the PIM kinases in terms of their expression and regulation of different physiological roles. We further predicted functional partners of PIM kinases to elucidate their role in the cellular physiology of different cancer and mapped their interaction network.

MAJOR CONCLUSIONS

A deeper mechanistic insight into the PIM signaling involved in regulating different cellular processes, including transcription, apoptosis, cell cycle regulation, cell proliferation, cell migration and senescence, is provided. Furthermore, structural features of PIM have been dissected to understand the mechanism of inhibition and subsequent implication of designed inhibitors towards therapeutic management of prostate, breast and other cancers.

GENERAL SIGNIFICANCE

Being a potential drug target for cancer therapy, available drugs and PIM inhibitors at different stages of clinical trials are discussed in detail.

Druggable binding sites in the multicomponent assemblies that characterise DNA double-strand-break repair through non-homologous end joining

Non-homologous end joining (NHEJ) is one of the two principal damage repair pathways for DNA double-strand breaks in cells. In this review, we give a brief overview of the system including a discussion of the effects of deregulation of NHEJ components in carcinogenesis and resistance to cancer therapy. We then discuss the relevance of targeting NHEJ components pharmacologically as a potential cancer therapy and review previous approaches to orthosteric regulation of NHEJ factors. Given the limited success of previous investigations to develop inhibitors against individual components, we give a brief discussion of the recent advances in computational and structural biology that allow us to explore different targets, with a particular focus on modulating protein-protein interaction interfaces. We illustrate this discussion with three examples showcasing some current approaches to developing protein-protein interaction inhibitors to modulate the assembly of NHEJ multiprotein complexes in space and time.

Structure-Based Virtual Screening and De Novo Design of PIM1 Inhibitors with Anticancer Activity from Natural Products

BACKGROUND

the proviral insertion site of Moloney murine leukemia (PIM) 1 kinase has served as a therapeutic target for various human cancers due to the enhancement of cell proliferation and the inhibition of apoptosis.

METHODS

to identify effective PIM1 kinase inhibitors, structure-based virtual screening of natural products of plant origin and de novo design were carried out using the protein-ligand binding free energy function improved by introducing an adequate dehydration energy term.

RESULTS

as a consequence of subsequent enzyme inhibition assays, four classes of PIM1 kinase inhibitors were discovered, with the biochemical potency ranging from low-micromolar to sub-micromolar levels. The results of extensive docking simulations showed that the inhibitory activity stemmed from the formation of multiple hydrogen bonds in combination with hydrophobic interactions in the ATP-binding site. Optimization of the biochemical potency by chemical modifications of the 2-benzylidenebenzofuran-3(2H)-one scaffold led to the discovery of several nanomolar inhibitors with antiproliferative activities against human breast cancer cell lines.

CONCLUSIONS

these new PIM1 kinase inhibitors are anticipated to serve as a new starting point for the development of anticancer medicine.

Discovery of SARxxxx92, a pan-PIM kinase inhibitor, efficacious in a KG1 tumor model

N-substituted azaindoles were discovered as potent pan-PIM inhibitors. Lead optimization, guided by structure and focused on physico-chemical properties allowed us to solve inherent hERG and permeability liabilities, and provided compound 27, which subsequently impacted KG-1 tumor growth in a mouse model.

Airborne Particulate Matter (PM10) Inhibits Apoptosis through PI3K/AKT/FoxO3a Pathway in Lung Epithelial Cells: The Role of a Second Oxidant Stimulus

Outdoor particulate matter (PM₁₀) exposure is carcinogenic to humans. The cellular mechanism by which PM₁₀ is associated specifically with lung cancer includes oxidative stress and damage to proteins, lipids, and DNA in the absence of apoptosis, suggesting that PM₁₀ induces cellular survival. We aimed to evaluate the PI3K/AKT/FoxO3a pathway as a mechanism of cell survival in lung epithelial A549 cells exposed to PM₁₀ that were subsequently challenged with hydrogen peroxide (H₂O₂). Our results showed that pre-exposure to PM₁₀ followed by H₂O₂, as a second oxidant stimulus increased the phosphorylation rate of pAKT^Ser473, pAKT^Thr308, and pFoxO3a^Ser253 2.5-fold, 1.8-fold, and 1.2-fold, respectively. Levels of catalase and p27^kip1, which are targets of the PIK3/AKT/FoxO3a pathway, decreased 38.1% and 62.7%, respectively. None of these changes had an influence on apoptosis; however, the inhibition of PI3K using the LY294002 compound revealed that the PI3K/AKT/FoxO3a pathway was involved in apoptosis evasion. We conclude that nontoxic PM₁₀ exposure predisposes lung epithelial cell cultures to evade apoptosis through the PI3K/AKT/FoxO3a pathway when cells are treated with a second oxidant stimulus.

Identification of Target Associations for Polypharmacology from Analysis of Crystallographic Ligands of the Protein Data Bank

The design of a chemical entity that potently and selectively binds to a biological target of therapeutic relevance has dominated the scene of drug discovery so far. However, recent findings suggest that multitarget ligands may be endowed with superior efficacy and be less prone to drug resistance. The Protein Data Bank (PDB) provides experimentally validated structural information about targets and bound ligands. Therefore, it represents a valuable source of information to help identifying active sites, understanding pharmacophore requirements, designing novel ligands, and inferring structure-activity relationships. In this study, we performed a large-scale analysis of the PDB by integrating different ligand-based and structure-based approaches, with the aim of identifying promising target associations for polypharmacology based on reported crystal structure information. First, the 2D and 3D similarity profiles of the crystallographic ligands were evaluated using different ligand-based methods. Then, activity data of pairs of similar ligands binding to different targets were inspected by comparing structural information with bioactivity annotations reported in the ChEMBL, BindingDB, BindingMOAD, and PDBbind databases. Afterward, extensive docking screenings of ligands in the identified cross-targets were made in order to validate and refine the ligand-based results. Finally, the therapeutic relevance of the identified target combinations for polypharmacology was evaluated from comparison with information on therapeutic targets reported in the Therapeutic Target Database (TTD). The results led to the identification of several target associations with high therapeutic potential for polypharmacology.

Current perspectives on targeting PIM kinases to overcome mechanisms of drug resistance and immune evasion in cancer

PIM kinases are a class of serine/threonine kinases that play a role in several of the hallmarks of cancer including cell cycle progression, metabolism, inflammation and immune evasion. Their constitutively active nature and unique catalytic structure has led them to be an attractive anticancer target through the use of small molecule inhibitors. This review highlights the enhanced activity of PIM kinases in cancer that can be driven by hypoxia in the tumour microenvironment and the important role that aberrant PIM kinase activity plays in resistance mechanisms to chemotherapy, radiotherapy, anti-angiogenic therapies and targeted therapies. We highlight an interaction of PIM kinases with numerous major oncogenic players, including but not limited to, stabilisation of p53, synergism with c-Myc, and notable parallel signalling with PI3K/Akt. We provide a comprehensive overview of PIM kinase's role as an escape mechanism to targeted therapies including PI3K/mTOR inhibitors, MET inhibitors, anti-HER2/EGFR treatments and the immunosuppressant rapamycin, providing a rationale for co-targeting treatment strategies for a more durable patient response. The current status of PIM kinase inhibitors and their use as a combination therapy with other targeted agents, in addition to the development of novel multi-molecularly targeted single therapeutic agents containing a PIM kinase targeting moiety are discussed.

Signaling and Function of Interleukin-2 in T Lymphocytes

The discovery of interleukin-2 (IL-2) changed the molecular understanding of how the immune system is controlled. IL-2 is a pleiotropic cytokine, and dissecting the signaling pathways that allow IL-2 to control the differentiation and homeostasis of both pro- and anti-inflammatory T cells is fundamental to determining the molecular details of immune regulation. The IL-2 receptor couples to JAK tyrosine kinases and activates the STAT5 transcription factors. However, IL-2 does much more than control transcriptional programs; it is a key regulator of T cell metabolic programs. The development of global phosphoproteomic approaches has expanded the understanding of IL-2 signaling further, revealing the diversity of phosphoproteins that may be influenced by IL-2 in T cells. However, it is increasingly clear that within each T cell subset, IL-2 will signal within a framework of other signal transduction networks that together will shape the transcriptional and metabolic programs that determine T cell fate.

The role of dorsal root ganglia PIM1 in peripheral nerve injury-induced neuropathic pain

Neuropathic pain induced by peripheral nerve injury is a complex and chronic state that is accompanied by poor quality of life. However, whether PIM1 (proviral integration site 1) contributes to the development of nociceptive hypersensitivity induced by nerve injury remains unknown. The present study was designed to investigate the effects of PIM1 on spinal nerve ligation (SNL) induced pain hypersensitivity. Here, we found that PIM1 positive neurons in the dorsal root ganglion (DRG) were colocalized with nociceptive neuronal markers CGRP, IB4 and substance P and were upregulated after SNL surgery. Knockdown PIM1 in the DRG by AAV5-shPIM1 alleviated SNL-induced pain hypersensitivity. In neuroblastoma cells (neuro-2a), PIM1 regulated the expression of CXCR4 phosphorylated at ser339 (pCXCR4) as well as the CXCL12/CXCR4 pathway. In the DRG tissues, we found that PIM1 was co-expressed with CXCR4, and knockdown of PIM1 attenuated pCXCR4 (ser339) protein expression but had little effect on total CXCR4 protein expression after SNL surgery. These findings suggest that PIM1 contributes to nerve injury-induced nociceptive hypersensitivity. Based on these findings and the characteristics of PIM1, we speculate that PIM1 might be a viable therapeutic target for the treatment of neuropathic pain in the near future.

A review on PIM kinases in tumors

The Proviral Integration site for Moloney murine leukemia virus (PIM) kinases is serine/threonine kinases that promote growth and survival in multiple cell types, implicated in the pathogenesis of various diseases. Over expression of Pim-1 experimentally leads to tumor formation in mice, whereas there is no observable phenotype concerning the complete knockout of the protein. When it is over expressed it may lead to cancer development by three major ways; by inhibiting apoptosis, by promoting cell proliferation and also through promoting genomic instability. Expression in normal tissues is nearly undetectable. Recent improvements in the development of novel inhibitors of PIMs have been reviewed. Significant progress in the design of PIMs inhibitors, in which it displays selectivity versus other kinases, has been achieved within the last years. However, the development of isoform-selective PIM inhibitors is still an open task. As Pim-1 possesses oncogenic functions and is over expressed in various kinds of cancer diseases, its inhibition provides a new option in cancer therapy. A PubMed literature search was performed to review the currently available data on Pim-1 expression, regulation, and targets; its implication in different types of cancer and its impact on prognosis is described. Consequently, designing new inhibitors of PIMs is now a very active area of research in academic and industrial laboratories.

Discovery of N-substituted 7-azaindoles as Pan-PIM kinases inhibitors - Lead optimization - Part III

N-substituted azaindoles were discovered as promising pan-PIM inhibitors. Lead optimization is described en route toward the identification of a clinical candidate. Modulation of physico-chemical properties allowed to solve inherent hERG and permeability liabilities. Compound 17 showed tumor growth inhibition in a KG1 tumor-bearing mouse model.

Single-Molecule Protein Phosphorylation and Dephosphorylation by Nanopore Enzymology

Reversible protein phosphorylation plays a crucial and ubiquitous role in the control of almost all cellular processes. The interplay of protein kinases and phosphatases acting in opposition ensures tight dynamic control of protein phosphorylation states within the cell. Previously, engineered α-hemolysin pores bearing kinase substrate peptides have been developed as single-molecule stochastic sensors for protein kinases. Here, we have used these pores to observe, label-free, the phosphorylation and dephosphorylation of a single substrate molecule. Further, we investigated the effect of Mg²⁺ and Mn²⁺ upon substrate and product binding and found that Mn²⁺ relaxes active-site specificity toward nucleotides and enhances product binding. In doing so, we demonstrate the power and versatility of nanopore enzymology to scrutinize a critical post-translational modification.

AZD1208, a Pan-Pim Kinase Inhibitor, Has Anti-Growth Effect on 93T449 Human Liposarcoma Cells via Control of the Expression and Phosphorylation of Pim-3, mTOR, 4EBP-1, S6, STAT-3 and AMPK

Overexpression of Pim kinases has an oncogenic/pro-survival role in many hematological and solid cancers. AZD1208 is a pan-Pim kinase inhibitor that has anti-cancer and anti-adipogenic actions. Here, we investigated the effects of AZD1208 on the growth of 93T449 cells, a differentiated human liposarcoma cell line. At 20 µM, AZD1208 was cytotoxic (cytostatic) but not apoptotic, reducing cell survival without DNA fragmentation, caspase activation or increasing cells in the sub G1 phase; known apoptotic parameters. Notably, AZD1208 reduced phosphorylation of signal transducer and activator of transcription-3 (STAT-3) in 93T449 cells. STAT-3 inhibition by AG490, a JAK2/STAT-3 inhibitor similarly reduced cell survival. AZD1208 down-regulated phosphorylation of mammalian target of rapamycin (mTOR) and ribosomal S6 while up-regulated eukaryotic initiation factor-2α (eIF-2α). In addition, AZD1208 induced a LKB-1-independent AMPK activation, which was crucial for its cytostatic effect, as knock-down of AMPK greatly blocked AZD1208s ability to reduce cell survival. AZD1208 had no effect on expression of two members of Pim kinase family (Pim-1 and Pim-3) but inhibited phosphorylation of 4EBP-1, a downstream effector of Pim kinases. Importantly, a central role for Pim-3 in the actions of AZD1208 was confirmed by knock-down, which not only reduced 93T449 cell survival but also led to the inhibition of 4EBP-1, mTOR, eIF-2α and STAT-3, along with the activation of AMPK. In summary, this is the first report demonstrating that AZD1208 inhibits growth of liposarcoma cells and that this activity is mediated through Pim-3 kinase, STAT-3, mTOR, S6 and AMPK expression and phosphorylation pathways.

PI3K Orchestrates T Follicular Helper Cell Differentiation in a Context Dependent Manner: Implications for Autoimmunity

T follicular helper (Tfh) cells are a specialized population of CD4⁺ T cells that provide help to B cells for the formation and maintenance germinal centers, and the production of high affinity class-switched antibodies, long-lived plasma cells, and memory B cells. As such, Tfh cells are essential for the generation of successful long-term humoral immunity and memory responses to vaccination and infection. Conversely, overproduction of Tfh cells has been associated with the generation of autoantibodies and autoimmunity. Data from gene-targeted mice, pharmacological inhibitors, as well as studies of human and mice expressing activating mutants have revealed that PI3Kδ is a key regulator of Tfh cell differentiation, acting downstream of ICOS to facilitate inactivation of FOXO1, repression of Klf2 and induction of Bcl6. Nonetheless, here we show that after acute LCMV infection, WT and activated-PI3Kδ mice (Pik3cd^E1020K/+) show comparable ratios of Tfh:Th1 viral specific CD4⁺ T cells, despite higher polyclonal Tfh cells in Pik3cd^E1020K/+ mice. Thus, the idea that PI3K activity primarily drives Tfh cell differentiation may be an oversimplification and PI3K-mediated pathways are likely to integrate multiple signals to promote distinct effector T cell lineages. The consequences of dysregulated Tfh cell generation will be discussed in the context of the human primary immunodeficiency “Activated PI3K-delta Syndrome” (APDS), also known as “p110 delta-activating mutation causing senescent T cells, lymphadenopathy and immunodeficiency” (PASLI). Overall, these data underscore a major role for PI3K signaling in the orchestration of T lymphocyte responses.

Targeting Pim Kinases and DAPK3 to Control Hypertension

Sustained vascular smooth muscle hypercontractility promotes hypertension and cardiovascular disease. The etiology of hypercontractility is not completely understood. New therapeutic targets remain vitally important for drug discovery. Here we report that Pim kinases, in combination with DAPK3, regulate contractility and control hypertension. Using a co-crystal structure of lead molecule (HS38) in complex with DAPK3, a dual Pim/DAPK3 inhibitor (HS56) and selective DAPK3 inhibitors (HS94 and HS148) were developed to provide mechanistic insight into the polypharmacology of hypertension. In vitro and ex vivo studies indicated that Pim kinases directly phosphorylate smooth muscle targets and that Pim/DAPK3 inhibition, unlike selective DAPK3 inhibition, significantly reduces contractility. In vivo, HS56 decreased blood pressure in spontaneously hypertensive mice in a dose-dependent manner without affecting heart rate. These findings suggest including Pim kinase inhibition within a multi-target engagement strategy for hypertension management. HS56 represents a significant step in the development of molecularly targeted antihypertensive medications.

Large-scale computational drug repositioning to find treatments for rare diseases

Rare, or orphan, diseases are conditions afflicting a small subset of people in a population. Although these disorders collectively pose significant health care problems, drug companies require government incentives to develop drugs for rare diseases due to extremely limited individual markets. Computer-aided drug repositioning, i.e., finding new indications for existing drugs, is a cheaper and faster alternative to traditional drug discovery offering a promising venue for orphan drug research. Structure-based matching of drug-binding pockets is among the most promising computational techniques to inform drug repositioning. In order to find new targets for known drugs ultimately leading to drug repositioning, we recently developed eMatchSite, a new computer program to compare drug-binding sites. In this study, eMatchSite is combined with virtual screening to systematically explore opportunities to reposition known drugs to proteins associated with rare diseases. The effectiveness of this integrated approach is demonstrated for a kinase inhibitor, which is a confirmed candidate for repositioning to synapsin Ia. The resulting dataset comprises 31,142 putative drug-target complexes linked to 980 orphan diseases. The modeling accuracy is evaluated against the structural data recently released for tyrosine-protein kinase HCK. To illustrate how potential therapeutics for rare diseases can be identified, we discuss a possibility to repurpose a steroidal aromatase inhibitor to treat Niemann-Pick disease type C. Overall, the exhaustive exploration of the drug repositioning space exposes new opportunities to combat orphan diseases with existing drugs. DrugBank/Orphanet repositioning data are freely available to research community at https://osf.io/qdjup/.

Theoretical Analysis of Activity Cliffs among Benzofuranone-Class Pim1 Inhibitors Using the Fragment Molecular Orbital Method with Molecular Mechanics Poisson-Boltzmann Surface Area (FMO+MM-PBSA) Approach

Significant activity changes due to small structural changes (i.e., activity cliffs) of serine/threonine kinase Pim1 inhibitors were studied theoretically using the fragment molecular orbital method with molecular mechanics Poisson-Boltzmann surface area (FMO+MM-PBSA) approach. This methodology enables quantum-chemical calculations for large biomolecules with solvation. In the course of drug discovery targeting Pim1, six benzofuranone-class inhibitors were found to differ only in the position of the indole-ring nitrogen atom. By comparing the various qualities of complex structures based on X-ray, classical molecular mechanics (MM)-optimized, and quantum/molecular mechanics (QM/MM)-optimized structures, we found that the QM/MM-optimized structures provided the best correlation (R² = 0.85) between pIC₅₀ and the calculated FMO+MM-PBSA binding energy. Combining the classical solvation energy with the QM binding energy was important to increase the correlation. In addition, decomposition of the interaction energy into various physicochemical components by pair interaction energy decomposition analysis suggested that CH-π and electrostatic interactions mainly caused the activity differences.

5-Ene-4-thiazolidinones - An efficient tool in medicinal chemistry

The presented review is an attempt to summarize a huge volume of data on 5-ene-4-thiazolidinones being a widely studied class of small molecules used in modern organic and medicinal chemistry. The manuscript covers approaches to the synthesis of 5-ene-4-thiazolidinone derivatives: modification of the C5 position of the basic core; synthesis of the target compounds in the one-pot or multistage reactions or transformation of other related heterocycles. The most prominent pharmacological profiles of 5-ene derivatives of different 4-thiazolidinone subtypes belonging to hit-, lead-compounds, drug-candidates and drugs as well as the most studied targets have been discussed. Currently target compounds (especially 5-en-rhodanines) are assigned as frequent hitters or pan-assay interference compounds (PAINS) within high-throughput screening campaigns. Nevertheless, the crucial impact of the presence/nature of C5 substituent (namely 5-ene) on the pharmacological effects of 5-ene-4-thiazolidinones was confirmed by the numerous listed findings from the original articles. The main directions for active 5-ene-4-thiazolidinones optimization have been shown: i) complication of the fragment in the C5 position; ii) introduction of the substituents in the N3 position (especially fragments with carboxylic group or its derivatives); iii) annealing in complex heterocyclic systems; iv) combination with other pharmacologically attractive fragments within hybrid pharmacophore approach. Moreover, the utilization of 5-ene-4-thiazolidinones in the synthesis of complex compounds with potent pharmacological application is described. The chemical transformations cover mainly the reactions which involve the exocyclic double bond in C5 position of the main core and correspond to the abovementioned direction of the 5-ene-4-thiazolidinone modification.

Structural analysis of PIM1 kinase complexes with ATP-competitive inhibitors

PIM1 is an oncogenic kinase overexpressed in a number of cancers where it correlates with poor prognosis. Several studies demonstrated that inhibition of PIM1 activity is an attractive strategy in fighting overexpressing cancers, while distinct structural features of ATP binding pocket make PIM1 an inviting target for the design of selective inhibitors. To facilitate development of specific PIM1 inhibitors, in this study we report three crystal structures of ATP-competitive inhibitors at the ATP binding pocket of PIM1. Two of the reported structures (CX-4945 and Ro-3306) explain the off-target effect on PIM1 of respectively casein kinase 2 and cyclin-dependent kinase 1 dedicated inhibitors. In turn, the structure with CX-6258 demonstrates a binding mode of a potent, selective inhibitor of PIM1, PIM2, PIM3 and Flt-3 kinases. The consequences of our findings for future inhibitor development are discussed.

Discovery of N-substituted 7-azaindoles as PIM1 kinase inhibitors - Part I

Novel N-substituted azaindoles have been discovered as PIM1 inhibitors. X-ray structures have played a significant role in orienting the chemistry effort in the initial phase of hit confirmation. Disclosure of an unconventional binding mode for 1 and 2, as demonstrated by X-ray crystallography, is presented and was an important factor in selecting and advancing a lead series.

Discovery of N-substituted 7-azaindoles as Pan-PIM kinase inhibitors - Lead series identification - Part II

N-Substituted azaindoles have been discovered as pan-PIM kinase inhibitors. Initial SAR, early ADME and PK/PD data of a series of compounds is described and led to the identification of promising pan-PIM inhibitors which validated our interest in the 7-azaindole scaffold and led us to pursue the identification of a clinical candidate.

Molecular analyses on Neospora caninum-triggered NETosis in the caprine system

Neospora caninum is an obligate intracellular protozoan parasite causing serious reproductive disorders in large and small ruminants worldwide. Polymorphonuclear neutrophils (PMN) react against multiple invading pathogens through different mechanisms including the release of neutrophil extracellular traps (NETs). Here, in vitro interactions of caprine PMN and N. caninum tachyzoites were studied. Scanning electron microscopic- and immunofluorescence-analyses demonstrated that caprine PMN undergo NETosis upon contact with tachyzoites of N. caninum, extruding filaments that entrap parasites. Detailed co-localization studies of N. caninum tachyzoite-induced NETs revealed the presence of PMN-derived DNA being decorated with histones (H1, H2A/H2B, H3,H4) and neutrophil elastase (NE) corroborating the molecular characteristics of classical mammalian NETs. As a new result for parasite-induced NETosis, we identified pentraxin and cathepsin B in N. caninum-triggered NETs. Nonetheless, functional inhibition assays revealed that during caprine NET formation triggered by N. caninum different molecular signaling pathways are induced, when compared to other apicomplexan parasites or host species. As such, N. caninum-induced NETosis appears to be influenced by MPO but independent of NADPH oxidase, SOCE, ERK1/2 and p38 MAPK activities. Furthermore, the inhibition of PMN autophagy via blockage of the PI3K-mediated signaling pathway failed to influence tachyzoite-induced NETosis. Since N. caninum-tachyzoites induced caprine NETosis, this effector mechanism should be considered as an early host immune response during acute caprine neosporosis.

In vitro evaluation of dihydropyridine-3-carbonitriles as potential cytotoxic agents through PIM-1 protein kinase inhibition

PIM-1 protein kinase inhibitor belongs to a novel class of serine/threonine kinases. As PIM-1 is overexpressed in cancer cells and possesses oncogenic functions, its inhibition provides a new option in cancer therapy. In this study, in vitro inhibitory effects of seven analogues of 1, 2-dihydropyridine-3-carbonitrile derivatives Ia-c, IIa-d on the activity of recombinant PIM-1 were evaluated using dimethylthiazol diphenyltetrazolium bromide (MTT) assay. The PIM-1 protein kinase inhibitory potencies and the cytotoxicity effects of tested compounds were respectively as follows: Ic > IIa > Ia > IIb > Ib > IId > IIc and IIb > IIa > Ia > IIc > Ic > Ib > IId, respectively. The compound Ic with methylthio imidazole substituent at C-3 position and benzodioxole substituent at C-6 position of 2-imino-1, 2-dihydropyridine-3- carbonitrile structure showed the strongest PIM-1 inhibitory effect (IC₅₀ = 111.01 nM), while the compound IIc with methythio imidazole substituent at C-3 position and benzodioxole substituent at C-6 position of 2-oxo-1, 2-dihydropyridine-3- carbonitrile structure exhibited the least inhibition activity (IC₅₀ = 433.71 nM). The docking results showed that all tested compounds localized appropriately in the middle of binding cavity after docking procedure, demonstrating suitable interactions between ligands and protein. This study demonstrated that the PIM-1 inhibitory potencies of newly synthesized compounds were in submicromolar concentrations (IC₅₀ < 150 nM) while they exhibited low cytotoxicity on HT-29 cell line (IC₅₀> 130 μM). Altogether, our data indicated that compounds Ic, IIa, Ia could be considered as new potent non-toxic PIM-1 inhibitors which could be used in combination with routine anti-proliferative drugs.

Design and Synthesis of Potent and Selective PIM Kinase Inhibitors by Targeting Unique Structure of ATP-Binding Pocket

In the development of kinase inhibitors, one of the major concerns is selectivity. An effective strategy to achieve high selectivity is to utilize structural differences among kinases to inform inhibitor design. Here, we set out to improve the PIM (proviral integration site for Moloney murine leukemia virus) kinase-inhibitory selectivity of our previously reported 7-azaindole derivative 2, which has promising ADMET properties, by targeting a unique bulge in the ATP-binding pocket. 6-Substituted 7-azaindoles, especially the 6-chlorinated derivatives, proved to be potent and selective PIM kinase inhibitors and appear to be promising lead compounds for future drug discovery.

Thiazolidine derivatives as potent and selective inhibitors of the PIM kinase family

The PIM family of serine/threonine kinases have become an attractive target for anti-cancer drug development, particularly for certain hematological malignancies. Here, we describe the discovery of a series of inhibitors of the PIM kinase family using a high throughput screening strategy. Through a combination of molecular modeling and optimization studies, the intrinsic potencies and molecular properties of this series of compounds was significantly improved. An excellent pan-PIM isoform inhibition profile was observed across the series, while optimized examples show good selectivity over other kinases. Two PIM-expressing leukemic cancer cell lines, MV4-11 and K562, were employed to evaluate the in vitro anti-proliferative effects of selected inhibitors. Encouraging activities were observed for many examples, with the best example (44) giving an IC₅₀ of 0.75μM against the K562 cell line. These data provide a promising starting point for further development of this series as a new cancer therapy through PIM kinase inhibition.

Isorhamnetin protects against cardiac hypertrophy through blocking PI3K-AKT pathway

Isorhamnetin, a flavonoid compound extracted from the Chinese herb Hippophae rhamnoides L., is well known for its anti-inflammatory, anti-oxidative, anti-adipogenic, anti-proliferative, and anti-tumor activities. However, the role of isorhamnetin in cardiac hypertrophy has not been reported. The aims of the present study were to find whether isorhamnetin could alleviate cardiac hypertrophy and to define the underlying molecular mechanisms. Here, we investigated the effects of isorhamnetin (100 mg/kg/day) on cardiac hypertrophy induced by aortic banding in mice. Cardiac hypertrophy was evaluated by echocardiographic, hemodynamic, pathological, and molecular analyses. Our data demonstrated that isorhamnetin could inhibit cardiac hypertrophy and fibrosis 8 weeks after aortic banding. The results further revealed that the effect of isorhamnetin on cardiac hypertrophy was mediated by blocking the activation of phosphatidylinositol 3-kinase-AKT signaling pathway. In vitro studies performed in neonatal rat cardiomyocytes confirmed that isorhamnetin could attenuate cardiomyocyte hypertrophy induced by angiotensin II, which was associated with phosphatidylinositol 3-kinase-AKT signaling pathway. In conclusion, these data indicate for the first time that isorhamnetin has protective potential for targeting cardiac hypertrophy by blocking the phosphatidylinositol 3-kinase-AKT signaling pathway. Thus, our study suggests that isorhamnetin may represent a potential therapeutic strategy for the treatment of cardiac hypertrophy and heart failure.

CREB regulates TNF-α-induced GM-CSF secretion via p38 MAPK in human lung fibroblasts

BACKGROUND

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that mediates eosinophilic differentiation, migration and survival, causing respiratory tract inflammation. GM-CSF is also known to be secreted from respiratory tract structural cells. However, the mechanisms of GM-CSF secretion have not been well established.

METHODS

Human fetal lung fibroblasts and human primary asthmatic lung fibroblasts were used for the study of tumor necrosis factor alpha (TNF-α)-induced GM-CSF secretion. GM-CSF secretion and mRNA expression were measured by enzyme-linked immunosorbent assay and quantitative real-time reverse transcription polymerase chain reaction, respectively. Knockdown of cAMP response element-binding protein (CREB) in fibroblasts was carried out by using specific small interfering RNAs of CREB.

RESULTS

Among respiratory tract structural cells, pulmonary fibroblasts exhibited increased GM-CSF secretion and mRNA expression after stimulation with TNF-α in a concentration-dependent manner. Moreover, a p38 mitogen-activated protein kinase (MAPK) inhibitor controlled TNF-α-induced GM-CSF secretion, and roflumilast and rolipram, inhibitors of phosphodiesterase-4, suppressed TNF-α-induced GM-CSF secretion. Consistent with this, forskolin also completely blocked GM-CSF secretion, and similar results were observed in response to cAMP treatment, suggesting that cAMP signaling suppressed TNF-α-induced GM-CSF secretion in human lung fibroblasts. Furthermore, CREB was phosphorylated through p38 MAPK but not cAMP signaling after TNF-α stimulation, and GM-CSF secretion was inhibited by CREB knockdown. Finally, these effects were also demonstrated in human primary lung fibroblasts in a patient with asthma.

CONCLUSIONS

CREB signaled independent of cAMP signaling and was phosphorylated by p38 MAPK following TNF-α stimulation, playing a critical role in GM-CSF secretion in human lung fibroblasts.

Pim1 inhibition as a novel therapeutic strategy for Alzheimer's disease

Background

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder worldwide. Clinically, AD is characterized by impairments of memory and cognitive functions. Accumulation of amyloid-β (Aβ) and neurofibrillary tangles are the prominent neuropathologies in patients with AD. Strong evidence indicates that an imbalance between production and degradation of key proteins contributes to the pathogenesis of AD. The mammalian target of rapamycin (mTOR) plays a key role in maintaining protein homeostasis as it regulates both protein synthesis and degradation. A key regulator of mTOR activity is the proline-rich AKT substrate 40 kDa (PRAS40), which directly binds to mTOR and reduces its activity. Notably, AD patients have elevated levels of phosphorylated PRAS40, which correlate with Aβ and tau pathologies as well as cognitive deficits. Physiologically, PRAS40 phosphorylation is regulated by Pim1, a protein kinase of the protoconcogene family. Here, we tested the effects of a selective Pim1 inhibitor (Pim1i), on spatial reference and working memory and AD-like pathology in 3xTg-AD mice.

Results

We have identified a Pim1i that crosses the blood brain barrier and reduces PRAS40 phosphorylation. Pim1i-treated 3xTg-AD mice performed significantly better than their vehicle treated counterparts as well as non-transgenic mice. Additionally, 3xTg-AD Pim1i-treated mice showed a reduction in soluble and insoluble Aβ₄₀ and Aβ₄₂ levels, as well as a 45.2 % reduction in Aβ₄₂ plaques within the hippocampus. Furthermore, phosphorylated tau immunoreactivity was reduced in the hippocampus of Pim1i–treated 3xTg-AD mice by 38 %. Mechanistically, these changes were linked to a significant increase in proteasome activity.

Conclusion

These results suggest that reductions in phosphorylated PRAS40 levels via Pim1 inhibition reduce Aβ and Tau pathology and rescue cognitive deficits by increasing proteasome function. Given that Pim1 inhibitors are already being tested in ongoing human clinical trials for cancer, the results presented here may open a new venue of drug discovery for AD by developing more Pim1 inhibitors.

Identification of quinones as novel PIM1 kinase inhibitors

PIM1 is a proto-oncogene encoding the serine/threonine PIM1 kinase. PIM1 kinase plays important roles in regulating aspects of cell cycle progression, apoptosis resistance, and has been implicated in the development of such malignancies as prostate cancer and acute myeloid leukemia among others. Knockout of PIM1 kinase in mice has been shown to be non-lethal without any obvious phenotypic changes, making it an attractive therapeutic target. Our investigation of anthraquinones as kinase inhibitors revealed a series of quinone analogs showing high selectivity for inhibition of the PIM kinases. Molecular modeling studies were used to identify key interactions and binding poses of these compounds within the PIM1 binding pocket. Compounds 1, 4, 7 and 9 inhibited the growth of DU-145 prostate cancer cell lines with a potency of 8.21μM, 4.06μM, 3.21μM and 2.02μM.

The PIM1 kinase promotes prostate cancer cell migration and adhesion via multiple signalling pathways

The ability of cells to migrate and form metastases is one of the fatal hallmarks of cancer that can be conquered only with better understanding of the molecules and regulatory mechanisms involved. The oncogenic PIM kinases have been shown to support cancer cell survival and motility, but the PIM-regulated pathways stimulating cell migration and invasion are less well characterized than those affecting cell survival. Here we have identified the glycogen synthase kinase 3β (GSK3B) and the forkhead box P3 (FOXP3) transcription factor as direct PIM targets, whose tumour-suppressive effects in prostate cancer cells are inhibited by PIM-induced phosphorylation, resulting in increased cell migration. Targeting GSK3B is also essential for the observed PIM-enhanced expression of the prostaglandin-endoperoxide synthase 2 (PTGS2), which is an important regulator of both cell migration and adhesion. Accordingly, selective inhibition of PIM activity not only reduces cell migration, but also affects integrin-mediated cell adhesion. Taken together, these data provide novel mechanistic insights on how and why patients with metastatic prostate cancer may benefit from therapies targeting PIM kinases, and how such approaches may also be applicable to inflammatory conditions.