Synthesis and evaluation of novel inhibitors of Pim-1 and Pim-2 protein kinases

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.

Synthesis, biological evaluation and in silico studies of 5-(3-methoxybenzylidene)thiazolidine-2,4-dione analogues as PTP1B inhibitors

PTP1B (protein tyrosine phosphatase 1B) dephosphorylates the insulin receptor substrate and thus acts as a negative regulator of the insulin and leptin signalling pathway. Recently, it has been considered as a new therapeutic target of intervention for the treatment of type2 diabetes. A series of aryl/alkylsulfonyloxy-5-(3-methoxybenzylidene)thiazolidine-2,4-dione derivatives were synthesized, screened in vitro for their PTP1B inhibitory activity and in vivo for anti-hyperglycaemic activity. Docking results further helped in understanding the nature of interactions governing the binding mode of ligands inside the active site of PTP1B. Among the synthesized compounds, 13 and 16 were found to be potent PTP1B inhibitors having IC₅₀ of 7.31 and 8.73μM respectively. Significant lowering of blood glucose level was observed in some of the synthesized compounds in in vivo study.

Upregulation of PIM2 by Underexpression of MicroRNA-135-5p Improves Survival Rates of Skin Allografts by Suppressing Apoptosis of Fibroblast Cells

BACKGROUND It has been reported that miR-135-5p is involved with many diseases. In this study, we aimed at define the relationship between miR-135-5p level and burn patient survival after skin transplantation. MATERIAL AND METHODS Expression of miR-135-5p and PIM2 was measured using real-time PCR and Western blot analysis in the skin samples collected from burn patients who received skin graft or in the fibroblast cells transfected with miR-135-5p mimics or inhibitors. The regulatory association between miR-135-5p and PIM2 was verified using bioinformatics analysis and luciferase assay. RESULTS The expression level of miR-135-5p was determined in 60 tissue samples divided into 2 groups based on the presence of rejection (long survival n=30, and short survival n=30). We found that miR-135-5p was substantially downregulated in the long survival group. We then searched the miRNA database online with the "seed sequence" located within the 3'-UTR of the target gene, and then validated PIM2 to be the direct gene via luciferase reporter assay system. We also established the negative regulatory relationship between miR-135-5p and PIM2 via studying the relative luciferase activity. We also conducted real-time PCR and Western blot analysis to study the mRNA and protein expression level of PIM2 among different groups (long survival n=30, short survival n=30) or cells treated with scramble control, miR-135-5p mimics, PIM2 siRNA, and miR-135-5p inhibitors, indicating the negative regulatory relationship between MiR-135-5p and PIM2. We also conducted experiments to investigate the influence of miR-135-5p and PIM2 on viability and apoptosis of cells. The results showed miR-135-5p reduced the viability of cells, while PIM2 negatively interfered with the viability of cells, and miR-135-5p inhibited apoptosis and PIM2 suppressed apoptosis. CONCLUSIONS MiR-135-5p is involved with the prognosis of burn patients after skin transplantation. PIM2 is a virtual target of miR-135-5p, and there is a negative regulatory relationship between miR-135-5p and PIM2. MiR-135-5p and PIM2 interfered with the viability and apoptosis in cells.

(5Z)-3-(2-Oxopropyl)-5-(3,4,5-trimethoxybenzylidene)-1,3-thiazolidine-2,4-dione

In the crystal of the title molecule, C16H17NO6S, there are three sets of intermolecular C—H...O hydrogen bonds, as well as two sets of intermolecular C—H...π(ring) interactions. In addition, the thiazolidene rings participate in offset π–π stacking interactions [centroid–centroid distance = 3.685 (1) Å]. These generate small channels running parallel to theaaxis with approximate cross-sections of 3.7 × 8.1 Å.

Investigation of 5-(3-Trifluoromethylbenzylidene)thiazolidine-2,4-dione as a Matrix for Analyses of Biogenic Monoamine Transmitters Using MALDI-MS

In order to discover new matrices suitable for the analyses of low molecular-weight compounds using positive-ion mode matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (MS), 5-(3-trifluoromethylbenzylidene)thiazolidine-2,4-dione (3-CF3-BTD) was synthesized, and its effectiveness was compared with that when commercially available α-cyano-4-hydroxycinnamic acid was used. 3-CF3-BTD was sufficiently sensitive to analyze neurotransmitters, i.e., dopamine, serotonin, histamine, and epinephrine, in amounts of several picomoles. Similar to vacuum MALDI experiments, atmospheric-pressure MALDI-MS measurements using 3-CF3-BTD as a matrix also detected dopamine.

Synthesis of novel 5-arylidenethiazolidinones with apoptotic properties via a three component reaction using piperidine as a bifunctional reagent

The synthesis of a new library of 5-arylidenethiazolidinone compounds using an efficient three component reaction with thiazolidine-2,4-dione, piperidine and appropriate aldehydes is reported. This reaction is excellently high yielding, tolerant towards a variety of aldehydes and provides access to these compounds in a single step (in comparison to low yielding multistep syntheses reported in the literature). Once the reaction is complete, the desired product precipitates out of the reaction mixture and is isolated by filtration and purified by washing and recrystallization. These compounds revealed anti-proliferative activities against human breast cancer cells (MCF7 and MDA). Phenotypic profiling established the most active compound 17i (EC50 = 4.52 μM) as an apoptotic agent. A novel chemical proteomics approach identified β-actin-like protein 2, γ-enolase and macrophage migration inhibitory factor (MMIF) as putative cellular binding partners of 17i.

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.

Identification of N-(4-((1R,3S,5S)-3-Amino-5-methylcyclohexyl)pyridin-3-yl)-6-(2,6-difluorophenyl)-5-fluoropicolinamide (PIM447), a Potent and Selective Proviral Insertion Site of Moloney Murine Leukemia (PIM) 1, 2, and 3 Kinase Inhibitor in Clinical Trials for Hematological Malignancies

Pan proviral insertion site of Moloney murine leukemia (PIM) 1, 2, and 3 kinase inhibitors have recently begun to be tested in humans to assess whether pan PIM kinase inhibition may provide benefit to cancer patients. Herein, the synthesis, in vitro activity, in vivo activity in an acute myeloid leukemia xenograft model, and preclinical profile of the potent and selective pan PIM kinase inhibitor compound 8 (PIM447) are described. Starting from the reported aminopiperidyl pan PIM kinase inhibitor compound 3, a strategy to improve the microsomal stability was pursued resulting in the identification of potent aminocyclohexyl pan PIM inhibitors with high metabolic stability. From this aminocyclohexyl series, compound 8 entered the clinic in 2012 in multiple myeloma patients and is currently in several phase 1 trials of cancer patients with hematological malignancies.

Combination of Pim kinase inhibitors and Bcl-2 antagonists in chronic lymphocytic leukemia cells

The Pim proteins are Ser/Thr kinases over-expressed in several hematological malignancies such as chronic lymphocytic leukemia (CLL) and some solid cancers like prostate cancer. Several small molecules have been developed to inhibit these kinases. In prostate cancer cell lines, the Pim kinase inhibitor SMI-4a and the Bcl-2 antagonist ABT-737 resulted in synergistic cytotoxicity. Akin to prostate cancer cells, CLL lymphocytes over-express Pim and Bcl-2 proteins. It was hypothesized that similar cytotoxic interaction should be observed in CLL. This study evaluated the in vitro cytotoxic effect of three Pim kinase inhibitors (AZD1208, SGI-1776 and SMI-4a) combined with Bcl-2 antagonists (ABT-737 or ABT-199) in malignant CLL lymphocytes. Data indicated Pim kinase inhibitors in combination with ABT-737 or ABT-199 resulted mostly in additive cytotoxicity with a few synergistic responses; however, the extent of synergism was less robust than that observed previously in prostate cancer cell lines treated with SMI-4a and ABT-737.

Synthetic Development of New 3-(4-Arylmethylamino)butyl-5-arylidene-rhodanines under Microwave Irradiation and Their Effects on Tumor Cell Lines and against Protein Kinases

A new route to 3-(4-arylmethylamino)butyl-5-arylidene-2-thioxo-1,3-thiazolidine-4-one 9 was developed in six steps from commercial 1,4-diaminobutane 1 as starting material. The key step of this multi-step synthesis involved a solution phase “one-pot two-steps” approach assisted by microwave dielectric from N-(arylmethyl)butane-1,4-diamine hydrochloride 6a–f (as source of the first point diversity) and commercial bis-(carboxymethyl)-trithiocarbonate reagent 7 for construction of the rhodanine platform. This platform was immediately functionalized by Knoevenagel condensation under microwave irradiation with a series of aromatic aldehydes 3 as second point of diversity. These new compounds were prepared in moderate to good yields and the fourteen synthetic products 9a–n have been obtained with a Z-geometry about their exocyclic double bond. These new 5-arylidene rhodanines derivatives 9a–n were tested for their kinase inhibitory potencies against four protein kinases: Human cyclin-dependent kinase 5-p25, HsCDK5-p25; porcine Glycogen Synthase Kinase-3, GSK-3α/β; porcine Casein Kinase 1, SsCK1 and human HsHaspin. They have also been evaluated for their in vitro inhibition of cell proliferation (HuH7 D12, Caco 2, MDA-MB 231, HCT 116, PC3, NCI-H727, HaCat and fibroblasts). Among of all these compounds, 9j presented selective micromolar inhibition activity on SsCK1 and 9i exhibited antitumor activities in the HuH7 D12, MDA-MBD231 cell lines.

Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions

We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups.

Design, synthesis and biological evaluation of novel C3-functionalized oxindoles as potential Pim-1 kinase inhibitors

A novel series of C3-functionalized oxindoles, 3-(2-oxo-4-phenylbut-3-en-1-ylidene) indolin-2-ones as potential Pim-1 kinase inhibitors, were designed, synthesized and investigated for inhibition of human cancer-cell proliferation.

The discovery of novel 3-(pyrazin-2-yl)-1H-indazoles as potent pan-Pim kinase inhibitors

The three Pim kinases are a small family of serine/threonine kinases regulating several signaling pathways that are fundamental to tumorigenesis. As such, the Pim kinases are a very attractive target for pharmacological inhibition in cancer therapy. Herein, we describe our efforts toward the development of a potent, pan-Pim inhibitor. The synthesis and hit-to-lead SAR development from a 3-(pyrazin-2-yl)-1H-indazole derived hit 2 to the identification of a series of potent, pan-Pim inhibitors such as 13o are described.

Cell-permeable dual inhibitors of protein kinases CK2 and PIM-1: structural features and pharmacological potential

It has been proposed that dual inhibitors of protein kinases CK2 and PIM-1 are tools particularly valuable to induce apoptosis of cancer cells, a property, however, implying cell permeability, which is lacking in the case of selective CK2/PIM-1 inhibitors developed so far. To fill this gap, we have derivatized the scaffold of the promiscuous CK2 inhibitor TBI with a deoxyribose moiety, generating TDB, a selective, cell-permeable inhibitor of CK2 and PIM-1. Here, we shed light on the structural features underlying the potency and narrow selectivity of TDB by exploiting a number of TDB analogs and by solving the 3D structure of the TDB/CK2 complex at 1.25 Å resolution, one of the highest reported so far for this kinase. We also show that the cytotoxic efficacy of TDB is almost entirely due to apoptosis, is accompanied by parallel inhibition of cellular CK2 and PIM-1, and is superior to both those observed combining individual inhibitors of CK2 and PIM-1 and by treating cells with the CK2 inhibitor CX4945. These data, in conjunction with the observations that cancer cells are more susceptible than non-cancer cells to TDB and that such a sensitivity is maintained in a multi-drug resistance background, highlight the pharmacological potential of this compound.

Pathophysiological roles of Pim-3 kinase in pancreatic cancer development and progression

Pim-3 is a member of the provirus integration site for Moloney murine leukemia virus (Pim) family proteins that exhibit serine/threonine kinase activity. Similar to the other Pim kinases (Pim-1 and Pim-2), Pim-3 is involved in many cellular processes, including cell proliferation, survival, and protein synthesis. Although Pim-3 is expressed in normal vital organs, it is overexpressed particularly in tumor tissues of endoderm-derived organs, including the liver, pancreas, and colon. Silencing of Pim-3 expression can retard in vitro cell proliferation of hepatocellular, pancreatic, and colon carcinoma cell lines by promoting cell apoptosis. Pim-3 lacks the regulatory domains similarly as Pim-1 and Pim-2 lack, and therefore, Pim-3 can exhibit its kinase activity once it is expressed. Pim-3 expression is regulated at transcriptional and post-transcriptional levels by transcription factors (e.g., Ets-1) and post-translational modifiers (e.g., translationally-controlled tumor protein), respectively. Pim-3 could promote growth and angiogenesis of human pancreatic cancer cells in vivo in an orthotopic nude mouse model. Furthermore, a Pim-3 kinase inhibitor inhibited cell proliferation when human pancreatic cancer cells were injected into nude mice, without inducing any major adverse effects. Thus, Pim-3 kinase may serve as a novel molecular target for developing targeting drugs against pancreatic and other types of cancer.

A small-molecule inhibitor of PIM kinases as a potential treatment for urothelial carcinomas

The proto-oncogene proviral integration site for moloney murine leukemia virus (PIM) kinases (PIM-1, PIM-2, and PIM-3) are serine/threonine kinases that are involved in a number of signaling pathways important to cancer cells. PIM kinases act in downstream effector functions as inhibitors of apoptosis and as positive regulators of G₁-S phase progression through the cell cycle. PIM kinases are upregulated in multiple cancer indications, including lymphoma, leukemia, multiple myeloma, and prostate, gastric, and head and neck cancers. Overexpression of one or more PIM family members in patient tumors frequently correlates with poor prognosis. The aim of this investigation was to evaluate PIM expression in low- and high-grade urothelial carcinoma and to assess the role PIM function in disease progression and their potential to serve as molecular targets for therapy. One hundred thirty-seven cases of urothelial carcinoma were included in this study of surgical biopsy and resection specimens. High levels of expression of all three PIM family members were observed in both noninvasive and invasive urothelial carcinomas. The second-generation PIM inhibitor, TP-3654, displays submicromolar activity in pharmacodynamic biomarker modulation, cell proliferation studies, and colony formation assays using the UM-UC-3 bladder cancer cell line. TP-3654 displays favorable human ether-à-go-go-related gene and cytochrome P450 inhibition profiles compared with the first-generation PIM inhibitor, SGI-1776, and exhibits oral bioavailability. In vivo xenograft studies using a bladder cancer cell line show that PIM kinase inhibition can reduce tumor growth, suggesting that PIM kinase inhibitors may be active in human urothelial carcinomas.

The Pim-1 protein kinase is an important regulator of MET receptor tyrosine kinase levels and signaling

MET, the receptor for hepatocyte growth factor (HGF), plays an important role in signaling normal and tumor cell migration and invasion. Here, we describe a previously unrecognized mechanism that promotes MET expression in multiple tumor cell types. The levels of the Pim-1 protein kinase show a positive correlation with the levels of MET protein in human tumor cell lines and patient-derived tumor materials. Using small interfering RNA (siRNA), Pim knockout mice, small-molecule inhibitors, and overexpression of Pim-1, we confirmed this correlation and found that Pim-1 kinase activity regulates HGF-induced tumor cell migration, invasion, and cell scattering. The novel biochemical mechanism for these effects involves the ability of Pim-1 to control the translation of MET by regulating the phosphorylation of eukaryotic initiation factor 4B (eIF4B) on S406. This targeted phosphorylation is required for the binding of eIF4B to the eIF3 translation initiation complex. Importantly, Pim-1 action was validated by the evaluation of patient blood and bone marrow from a phase I clinical trial of a Pim kinase inhibitor, AZD1208. These results suggest that Pim inhibitors may have an important role in the treatment of patients where MET is driving tumor biology.

Rational approaches, design strategies, structure activity relationship and mechanistic insights for anticancer hybrids

A Hybrid drug which comprises the incorporation of two drug pharmacophores in one single molecule are basically designed to interact with multiple targets or to amplify its effect through action on another bio target as one single molecule or to counterbalance the known side effects associated with the other hybrid part(.) The present review article offers a detailed account of the design strategies employed for the synthesis of anticancer agents via molecular hybridization techniques. Over the years, the researchers have employed this technique to discover some promising chemical architectures displaying significant anticancer profiles. Molecular hybridization as a tool has been particularly utilized for targeting tubulin protein as exemplified through the number of research papers. The microtubule inhibitors such as taxol, colchicine, chalcones, combretasatin, phenstatins and vinca alkaloids have been utilized as one of the functionality of the hybrids and promising results have been obtained in most of the cases with some of the tubulin based hybrids exhibiting anticancer activity at nanomolar level. Linkage with steroids as biological carrier vector for anticancer drugs and the inclusion of pyrrolo [2,1-c] [1,4]benzodiazepines (PBDs), a family of DNA interactive antitumor antibiotics derived from Streptomyces species in hybrid structure based drug design has also emerged as a potential strategy. Various heteroaryl based hybrids in particular isatin and coumarins have also been designed and reported to posses' remarkable inhibitory potential. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the hybrids.

Expanding the scope of human DNA polymerase λ and β inhibitors

The exact biological functions of individual DNA polymerases still await clarification, and therefore appropriate reagents to probe their respective functions are required. In the present study, we report the development of a highly potent series of human DNA polymerase λ and β (pol λ and β) inhibitors based on the rhodanine scaffold. Both enzymes are involved in DNA repair and are thus considered as future drug targets. We expanded the chemical diversity of the small-molecule inhibitors arising from a high content screening and designed and synthesized 30 novel analogues. By biochemical evaluation, we discovered 23 highly active compounds against pol λ. Importantly, 10 of these small-molecules selectively inhibited pol λ and not the homologous pol β. We discovered 14 small-molecules that target pol β and found out that they are more potent than known inhibitors. We also investigated whether the discovered compounds sensitize cancer cells toward DNA-damaging reagents. Thus, we cotreated human colorectal cancer cells (Caco-2) with the small-molecule inhibitors and hydrogen peroxide or the approved drug temozolomide. Interestingly, the tested compounds sensitized Caco-2 cells to both genotoxic agents in a DNA repair pathway-dependent manner.

Thiazolidinone-peptide hybrids as dengue virus protease inhibitors with antiviral activity in cell culture

The protease of dengue virus is a promising target for antiviral drug discovery. We here report a new generation of peptide-hybrid inhibitors of dengue protease that incorporate N-substituted 5-arylidenethiazolidinone heterocycles (rhodanines and thiazolidinediones) as N-terminal capping groups of the peptide moiety. The compounds were extensively characterized with respect to inhibition of various proteases, inhibition mechanisms, membrane permeability, antiviral activity, and cytotoxicity in cell culture. A sulfur/oxygen exchange in position 2 of the capping heterocycle (thiazolidinedione-capped vs rhodanine-capped peptide hybrids) has a significant effect on these properties and activities. The most promising in vitro affinities were observed for thiazolidinedione-based peptide hybrids containing hydrophobic groups with Ki values between 1.5 and 1.8 μM and competitive inhibition mechanisms. Rhodanine-capped peptide hybrids with hydrophobic substituents have, in correlation with their membrane permeability, a more pronounced antiviral activity in cell culture than the thiazolidinediones.

Small molecule inhibitors of PIM1 kinase: July 2009 to February 2013 patent update

INTRODUCTION

The proviral insertion in murine (PIM) lymphoma proteins for which three isoforms, PIM1, PIM2 and PIM3 have been identified, belonging to the family of serine/threonine kinases has emerged recently as an important therapeutic target for the development of selective inhibitors as the new drugs for treating hematological malignancies and solid tumors. The small molecules developed by academia and the pharmaceutical industry have steadily increased in the last few years. Several drug discovery groups focus on treating disorders, such as cancer mediated by PIM kinase, have provided preclinical evidence suggesting that PIM inhibitor provides anti-apoptotic activity, inhibit cell survival and cell proliferation.

AREAS COVERED

This article discloses recent reviews on research and advances published in the patent literature and scientific publications from July 2009 to February 2013, highlighting discoveries on PIM1 kinase.

EXPERT OPINION

Several PIM1 kinase small molecule inhibitors are now at the pre-clinical research stage, development and testing. Though nearly 40 patents emerged in the last 3 years, greater efforts towards additional designs and medicinal chemistry continues for developing clinically efficacious PIM1 inhibitors, due to the significance of the target for cancer and the potential for novel and diverse inhibitors as drug candidates.

Discovery of pyrazolo[1,5-a]pyrimidine-based Pim inhibitors: a template-based approach

The synthesis and hit-to-lead SAR development from a pyrazolo[1,5-a]pyrimidine-derived hit 5 to the identification of a series of potent, pan-Pim inhibitors such as 11j are described.

The over-expression of Pim-2 promote the tumorigenesis of prostatic carcinoma through phosphorylating eIF4B

BACKGROUND

Cell experiments have found Pim-2 may take part in the tumorigenesis of prostatic carcinoma (PCA). More direct evidences are needed, and the detailed anti-apoptotic mechanism of Pim-2 in PCA cells is still unknown.

METHODS

Pim-2 expression levels were compared between benign prostatic hyperplasia (BPH) tissues and PCA tissues using real time PCR and Western blot, respectively. Then Pim-2 expression levels were detected in PCA cell lines DU-145 and LNCaP, as well as in nontumorous prostatic epithelial cell lines RWPE-1 and PNT1a, using real time PCR and Western blot, respectively. The co-expression of Pim-2 and eukaryotic initiation factor 4B (eIF4B) was examined by immunofluorescence cytochemistry using laser scanning confocal microscope. Finally, Pim-2 SiRNA was transfected into DU-145 cells and Pim-2 was transfected into RWPE-1 cells, and the level of Pim-2 and phosphorylated eukaryotic initiation factor 4B (p-eIF4B) were detected, as well as the apoptosis rate.

RESULTS

The Pim-2 mRNA and protein level were significantly higher in PCA tissues than those in BPH tissues. The Pim-2 mRNA and protein level in DU-145 and LNCaP cells were significantly higher than those in RWPE-1 and PNT1a cells. Pim-2 and eIF4B could co-express in DU-145 cells. Pim-2 level determined the phosphorylation level of eIF4B and the apoptosis rate of prostatic cells. The higher Pim-2 expressed, the more eIF4B phosphorylated, then the less cell got apoptosis, and vice versa.

CONCLUSION

Pim-2 was over-expressed in PCA cell lines and tissues. It may inhibit the apoptosis of PCA cells through phosphorylating eIF4B, thus promote the tumorigenesis of PCA.

A combination strategy to inhibit Pim-1: synergism between noncompetitive and ATP-competitive inhibitors

Pim-1 is a serine/threonine kinase critically involved in the initiation and progression of various types of cancer, especially leukemia, lymphomas and solid tumors such as prostate, pancreas and colon, and is considered a potential drug target against these malignancies. In an effort to discover new potent Pim-1 inhibitors, a previously identified ATP-competitive indolyl-pyrrolone scaffold was expanded to derive structure-activity relationship data. A virtual screening campaign was also performed, which led to the discovery of additional ATP-competitive inhibitors as well as a series of 2-aminothiazole derivatives, which are noncompetitive with respect to both ATP and peptide substrate. This mechanism of action, which resembles allosteric inhibition, has not previously been characterized for Pim-1. Notably, further evaluation of the 2-aminothiazoles indicated a synergistic inhibitory effect in enzymatic assays when tested in combination with ATP-competitive inhibitors. A synergistic effect in the inhibition of cell proliferation by ATP-competitive and ATP-noncompetitive compounds was also observed in prostate cancer cell lines (PC3), where all Pim-1 inhibitors tested in showed synergism with the known anticancer agent, paclitaxel. These results further establish Pim-1 as a target in cancer therapy, and highlight the potential of these agents for use as adjuvant agents in the treatment of cancer diseases in which Pim-1 is associated with chemotherapeutic resistance.

Elevation of receptor tyrosine kinases by small molecule AKT inhibitors in prostate cancer is mediated by Pim-1

The PI3K/AKT pathway is hyperactivated in prostate cancer but its effective therapeutic targeting has proven difficult. In particular, the antitumor activity of AKT inhibitors is attenuated by upregulation of receptor tyrosine kinases (RTK) through an uncharacterized feedback mechanism. In this report, we show that RNA interference-mediated silencing or pharmacologic inhibition of Pim-1 activity curtails AKT inhibitor-induced upregulation of RTKs in prostate cancer cells. Although Pim kinases have been implicated in cap-dependent translational control, we find that in the context of AKT inhibition, the expression of RTKs is controlled by Pim-1 in a cap-independent manner by controlling internal ribosome entry. Combination of Pim and AKT inhibitors resulted in synergistic inhibition of prostate tumor growth in vitro and in vivo. Together, our results show that Pim-1 mediates resistance to AKT inhibition and suggest its targeting to improve the efficacy of AKT inhibitors in anticancer therapy.

The PIM family of serine/threonine kinases in cancer

The proviral insertion site in Moloney murine leukemia virus, or PIM proteins, are a family of serine/threonine kinases composed of three different isoforms (PIM1, PIM2, and PIM3) that are highly evolutionarily conserved. These proteins are regulated primarily by transcription and stability through pathways that are controlled by Janus kinase/Signal transducer and activator of transcription, JAK/STAT, transcription factors. The PIM family proteins have been found to be overexpressed in hematological malignancies and solid tumors, and their roles in these tumors were confirmed in mouse tumor models. Furthermore, the PIM family proteins have been implicated in the regulation of apoptosis, metabolism, cell cycle, and homing and migration, which has led to the postulation of these proteins as interesting targets for anticancer drug discovery. In the present work, we review the importance of PIM kinases in tumor growth and as drug targets.

LY294002 enhances expression of proteins encoded by recombinant replication-defective adenoviruses via mTOR- and non-mTOR-dependent mechanisms

Adenovirus-based drugs are efficient when combined with other anticancer treatments. Here we show that treatment with LY294002 and LY303511 upregulates expression of recombinant proteins encoded by replication-defective adenoviruses, including expression of therapeutically valuable combination of herpes simplex virus thymidine kinase controlled by human telomerase reverse transcriptase promoter (Ad-hTERT-HSVtk). In line with this, treatment with LY294002 synergized with Ad-hTERT-HSVtk infection in the presence of gancyclovir prodrug on Calu-I lung cancer cell death. The effect of LY294002 and LY303511 on adenovirus-delivered transgene expression was demonstrated in 4 human lung cancer cell lines. LY294002-induced upregulation of adenovirally delivered transgene is mediated in part by direct inhibition of mTOR protein kinase in mTORC2 signaling complex thus suggesting that anticancer drugs targeting mTOR will also enhance expression of transgenes delivered with adenoviral vectors. As both LY294002 and LY303511 are candidate prototypic anticancer drugs, and many mTOR inhibitors for cancer treatment are under development, our results have important implication for development of future therapeutic strategies with adenoviral gene delivery.

Structure-based discovery of cellular-active allosteric inhibitors of FAK

In order to develop potent and selective focal adhesion kinase (FAK) inhibitors, synthetic studies on pyrazolo[4,3-c][2,1]benzothiazines targeted for the FAK allosteric site were carried out. Based on the X-ray structural analysis of the co-crystal of the lead compound, 8-(4-ethylphenyl)-5-methyl-1,5-dihydropyrazolo[4,3-c][2,1]benzothiazine 4,4-dioxide 1 with FAK, we designed and prepared 1,5-dimethyl-1,5-dihydropyrazolo[4,3-c][2,1]benzothiazin derivatives which selectively inhibited kinase activity of FAK without affecting seven other kinases. The optimized compound, N-(4-tert-butylbenzyl)-1,5-dimethyl-1,5-dihydropyrazolo[4,3-c][2,1]benzothiazin-8-amine 4,4-dioxide 30 possessed significant FAK kinase inhibitory activities both in cell-free (IC50=0.64μM) and in cellular assays (IC50=7.1μM). These results clearly demonstrated a potential of FAK allosteric inhibitors as antitumor agents.

T-18, a stemonamide synthetic intermediate inhibits Pim kinase activity and induces cell apoptosis, acting as a potent anticancer drug

Pim-3 kinase has been shown to be aberrantly expressed in premalignant and malignant lesions of endoderm-derived organs such as the liver, pancreas, colon and stomach. Pim-3 kinase inactivates the Bad protein, a proapoptotic molecule, and improves the expression of Bcl-xL, an antiapoptotic molecule, to promote cell proliferation. Thus, blocking Pim-3 kinase activity may be a new strategy for the treatment of pancreatic cancer. In this study, we screened low molecular compounds and observed that the stemonamide synthetic intermediate, T-18, potently inhibited Pim kinase activity. Moreover, T-18 inhibited the proliferation of human pancreatic, as well as that of hepatocellular and colon cancer cells in vitro. It also induced the apoptosis of human pancreatic carcinoma cells in vitro by decreasing the levels of phospho-Ser112-Bad; the levels of Pim-3 kinase and total Bad protein were not altered. Furthermore, T-18 inhibited the growth of human pancreatic cancer cells in nude mice without apparent adverse effects when the tumor was palpable. These observations indicate that stemonamide synthetic intermediates may be novel drugs for the treatment of gastrointestinal cancers, particularly pancreatic cancer.

Inhibition of Pim2-prolonged skin allograft survival through the apoptosis regulation pathway

Recently, apoptosis has been considered to be an important regulator for allograft survival. The serine/threonine kinase Pim2 has been implicated in many apoptotic pathways. In a previous study, we found that pim2 was highly expressed in CD4(+) T cells in an allograft model. Here, we further investigated the effects of Pim2 on allograft survival and the underlying mechanisms associated with apoptosis. The results showed that pim2 was overexpressed in grafts and spleens, particularly in spleen CD4(+) T cells when acute allorejection occurred, and correlated positively with the extent of rejection. In T cells from the spleens of naive BALB/c mice treated with 5 µM 4a (a specific inhibitor of Pim2) for 24 h, the apoptosis rate increased and the phosphorylation of BAD was decreased. Furthermore, adoptive transfer of CD4(+) T cells treated with 4a in vitro to allografted severe combined immunodeficiency (SCID) mice effectively prolonged allograft survival from 19.5±1.7 days to 31±2.3 days. Moreover, the results demonstrated that the CD4(+)CD25(-) effector T-cell subset was the predominate expresser of the pim2 gene as compared with the CD4(+)CD25(+) regulatory T (Treg) cell subset. Alloantigen-induced CD4(+)CD25(+) T cells displayed less Foxp3 expression and a low suppression of apoptosis compared with effector CD4(+)CD25(-) T cells treated with 4a. Collectively, these data revealed that Pim2 facilitated allograft rejection primarily by modulating the apoptosis of effector T cells and the function of Treg cells. These data suggested that Pim2 may be an important target for in vivo anti-rejection therapies and for the ex vivo expansion of CD4(+)CD25(+) T cells.

Pim kinases in cancer: diagnostic, prognostic and treatment opportunities

PIM proteins belong to a family of ser/thr kinases composed of 3 members, PIM1, PIM2 and PIM3, with greatly overlapping functions. PIM kinases are mainly responsible for cell cycle regulation, antiapoptotic activity and the homing and migration of receptor tyrosine kinases mediated via the JAK/STAT pathway. PIM kinases have been found to be upregulated in many hematological malignancies and solid tumors. Although these kinases have been described as weak oncogenes, they are heavily targeted for anticancer drug discovery. The present review summarizes the discoveries made to date regarding PIM kinases as driving oncogenes in the process of tumorigenesis and their validation as drug targets.

Phosphorylation of the androgen receptor by PIM1 in hormone refractory prostate cancer

Integration of cellular signaling pathways with androgen receptor (AR) signaling can be achieved through phosphorylation of AR by cellular kinases. However, the kinases responsible for phosphorylating the androgen receptor at numerous sites and the functional consequences of AR phosphorylation are only partially understood. Bioinformatic analysis revealed AR serine 213 (S213) as a putative substrate for PIM1, a kinase overexpressed in prostate cancer. Therefore, phosphorylation of AR serine 213 by PIM1 was examined using a phosphorylation site-specific antibody. Wild type PIM1, but not catalytically inactive PIM1, specifically phosphorylated AR but not an AR serine to alanine mutant (S213A). In vitro kinase assays confirmed that PIM1 can phosphorylate AR S213 in a ligand independent manner and cell type specific phosphorylation was observed in prostate cancer cell lines. Upon PIM1 overexpression AR phosphorylation was observed in the absence of hormone and was further increased in the presence of hormone in LNCaP, LNCaP-abl, and VCaP cells. Moreover, phosphorylation of AR was reduced in the presence of PIM kinase inhibitors. An examination of AR mediated transcription showed that reporter gene activity was reduced in the presence of PIM1 and wild type AR, but not S213A mutant AR. Androgen mediated transcription of endogenous PSA, Nkx3.1, and IGFBP5 was also decreased in the presence of PIM1 whereas IL6, cyclin A1, and caveolin 2 were increased. Immunohistochemical analysis of prostate cancer tissue microarrays showed significant P-AR S213 expression that was associated with hormone refractory prostate cancers, likely identifying cells with catalytically active PIM1. In addition, prostate cancers expressing a high level of P-AR S213 were twice as likely to be from biochemically recurrent cancers. Thus, AR phosphorylation by PIM1 at S213 impacts gene transcription and is highly prevalent in aggressive prostate cancer.

A Solvent-Free Protocol for the Green Synthesis of 5-Arylidene-2,4-thiazolidinediones Using Ethylenediamine Diacetate as Catalyst

A simple and efficient synthesis of 5-arylidene-2,4-thiazolidinediones by the Knoevenagel condensation of aromatic aldehydes with 2,4-thiazolidinedione catalyzed by ethylenediamine diacetate under solvent-free conditions is described. The major advantages of this method are simple experimental and work-up procedures, solvent-free reaction conditions, small amount of catalyst, short reaction time, high yields, and utilization of an inexpensive and reusable catalyst.