The PIM family of serine/threonine kinases in cancer

Targeting cytokine- and therapy-induced PIM1 activation in preclinical models of T-cell acute lymphoblastic leukemia and lymphoma

T-cell acute lymphoblastic leukemia (T-ALL) and T-cell acute lymphoblastic lymphoma (T-LBL) are aggressive hematological malignancies that are currently treated with high-dose chemotherapy. Over the last several years, the search toward novel and less-toxic therapeutic strategies for T-ALL/T-LBL patients has largely focused on the identification of cell-intrinsic properties of the tumor cell. However, non-cell-autonomous activation of specific oncogenic pathways might also offer opportunities that could be exploited at the therapeutic level. In line with this, we here show that endogenous interleukin 7 (IL7) can increase the expression of the oncogenic kinase proviral integration site for Moloney-murine leukemia 1 (PIM1) in CD127+ T-ALL/T-LBL, thereby rendering these tumor cells sensitive to in vivo PIM inhibition. In addition, using different CD127+ T-ALL/T-LBL xenograft models, we also reveal that residual tumor cells, which remain present after short-term in vivo chemotherapy, display consistent upregulation of PIM1 as compared with bulk nontreated tumor cells. Notably, this effect was transient as increased PIM1 levels were not observed in reestablished disease after abrogation of the initial chemotherapy. Furthermore, we uncover that this phenomenon is, at least in part, mediated by the ability of glucocorticoids to cause transcriptional upregulation of IL7RA in T-ALL/T-LBL patient-derived xenograft (PDX) cells, ultimately resulting in non-cell-autonomous PIM1 upregulation by endogenous IL7. Finally, we confirm in vivo that chemotherapy in combination with a pan-PIM inhibitor can improve leukemia survival in a PDX model of CD127+ T-ALL. Altogether, our work reveals that IL7 and glucocorticoids coordinately drive aberrant activation of PIM1 and suggests that IL7-responsive CD127+ T-ALL and T-LBL patients could benefit from PIM inhibition during induction chemotherapy.

A review of the processed Polygonum multiflorum (Thunb.) for hepatoprotection: Clinical use, pharmacology and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum multiflorum (Thunb.) (PMT) is a member of Polygonaceae. Traditional Chinese medicine considers that the processed PMT can tonify liver, nourish blood and blacken hair. In recent years, the processed PMT and its active ingredients have significant therapeutic effects on nonalcoholic fatty liver disease, alcoholic fatty liver disease, viral hepatitis, liver fibrosis and liver cancer.

AIM OF THE STUDY

The main purpose of this review is to provide a critical appraisal of the existing knowledge on the clinical application, hepatoprotective pharmacology and hepatotoxicity, it provides a comprehensive evaluation of the liver function of the processed PMT.

MATERIALS AND METHODS

A detailed literature search was conducted using various online search engines, such as Pubmed, Google Scholar, Mendeley, Web of Science and China National Knowledge Infrastructure (CNKI) database. The main active components of the processed PMT and the important factors in the occurrence and development of liver diseases are used as key words to carry out detailed literature retrieval.

RESULTS

In animal and cell models, the processed PMT and active components can treat various liver diseases, such as fatty liver induced by high-fat diet, liver injury and fibrosis induced by drugs, viral transfected hepatitis, hepatocellular carcinoma, etc. They can protect liver by regulating lipid metabolism related enzymes, resisting insulin resistance, decreasing the expression of inflammatory cytokines, inhibiting the activation of hepatic stellate cells, reducing generation of extracellular matrix, promoting cancer cell apoptosis and controlling the growth of tumor cells, etc. However, improperly using of the processed PMT can cause liver injury, which is associated with the standardization of processing, the constitution of the patients, the characteristics of the disease, and the administration of dosage and time.

CONCLUSION

The processed PMT can treat various liver diseases via reasonably using, and the active compounds (2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, emodin, physcion, etc.) are promising candidate drugs for developing new liver protective agents. However, some components have a "toxic-effective" bidirectional effect, which should be used cautiously.

New cyanopyridine-based scaffold as PIM-1 inhibitors and apoptotic inducers: Synthesis and SARs study

Two novel series of 6-(4-benzamido-/4-phthalimido)-3-cyanopyridine derivatives were designed and synthesized as inhibitors of PIM-1 kinase. Based on cytotoxicity results via MTT assay against prostate carcinoma PC3, human hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7 cell lines, the most potent cytotoxic cyanopyridine hits, 6, 7, 8, 12 and 13 were 1.5-3.3 times more inhibitor of cell proliferation than the reference standard, 5-FU. Selectivity profile of the latter compounds on normal human cells (WI-38), was executed, indicating that they are highly selective (IC₅₀ > 145 μM) in their cytotoxic effect. The promising compounds were further evaluated as PIM-1 kinase inhibitors. These compounds elicited remarkable inhibition of PIM-1 kinase (76.43-53.33%). Extensive studies on apoptosis were conducted for these compounds; they enhanced caspase-3 and boosted the Bax/Bcl-2 ratio 27-folds in comparison to the control. Molecular docking study of the most potent compound, 13 in PIM-1 kinase active site was consistent with the in vitro activity. Finally, prediction of chemo-informatic properties released compound 13 as the most promising ligand.

Pim kinase inhibitors in cancer: medicinal chemistry insights into their activity and selectivity

The oncogenic Pim kinase proteins (Pim-1/2/3) regulate tumorigenesis through phosphorylating essential proteins that control cell cycle and proliferation. Pim kinase is a potential chemotherapeutic target in cancer and its inhibition is currently the focus of intensive drug design and development efforts. The distinctive presence of proline amino acids in the hinge region provides an opportunity to inhibit Pim kinase while conserving the physiological functions of other kinases and reducing the toxicity profiles of the inhibitors. Various Pim kinase inhibitors have been clinically evaluated for the treatment of hematological cancers, yet none has reached the clinic. In this review, we discuss the design and development of selective and potent Pim inhibitors with novel chemotypes focusing on structural features essential for high potency and selectivity.

Inhibition of PIM1 kinase attenuates bleomycin-induced pulmonary fibrosis in mice by modulating the ZEB1/E-cadherin pathway in alveolar epithelial cells

PIM1 is serine/threonine protein kinase that is involved in numerous biological processes. Pulmonary fibrosis (PF) is a chronic pathological result of the dysfunctional repair of lung injury without effective therapeutic treatments. In the current study, we investigated whether PIM1 inhibition would improve bleomycin (BLM)-induced pulmonary fibrosis. In a BLM-induced pulmonary fibrosis model, PIM1 was persistently upregulated in fibrotic lung tissues. Furthermore, PIM1 inhibition by the PIM1-specific inhibitor SMI-4a showed protective effects against BLM-induced mortality. Furthermore, SMI-4a suppressed hydroxyproline deposition and reversed epithelial-mesenchymal transition (EMT) formation, which was characterized by E-cadherin and α-SMA expression in vivo. More importantly, the ZEB1/E-cadherin pathway was found to be closely associated with BLM-induced pulmonary fibrosis. After the in vitro treatment of A549 cells, PIM1 regulated E-cadherin expression by dependently modulating the activity of the transcription factor ZEB1. These findings were verified in vivo after SMI-4a administration. Finally, an shPIM1-expressing adeno-associated virus was delivered via intratracheal injection to induce a long-term PIM1 deficiency in the alveolar epithelium. AAV-mediated PIM1 knockdown in the lung tissues alleviated BLM-induced pulmonary fibrosis, as indicated by collagen accumulation reduction, pulmonary histopathological mitigation and EMT reversion. These findings enhance our understanding of the roles of PIM1 in BLM-induced pulmonary fibrosis and suggest PIM1 inhibition as a potential therapeutic strategy in chronic pulmonary injuries.

Therapeutic Targeting of Signaling Pathways Related to Cancer Stemness

The theory of cancer stem cells (CSCs) proposes that the different cells within a tumor, as well as metastasis deriving from it, are originated from a single subpopulation of cells with self-renewal and differentiation capacities. These cancer stem cells are supposed to be critical for tumor expansion and metastasis, tumor relapse and resistance to conventional therapies, such as chemo- and radiotherapy. The acquisition of these abilities has been attributed to the activation of alternative pathways, for instance, WNT, NOTCH, SHH, PI3K, Hippo, or NF-κB pathways, that regulate detoxification mechanisms; increase the metabolic rate; induce resistance to apoptotic, autophagic, and senescence pathways; promote the overexpression of drug transporter proteins; and activate specific stem cell transcription factors. The elimination of CSCs is an important goal in cancer therapeutic approaches because it could decrease relapses and metastatic dissemination, which are main causes of mortality in oncology patients. In this work, we discuss the role of these signaling pathways in CSCs along with their therapeutic potential.

Virtual Screening and Design with Machine Intelligence Applied to Pim-1 Kinase Inhibitors

Ligand-based virtual screening of large compound collections, combined with fast bioactivity determination, facilitate the discovery of bioactive molecules with desired properties. Here, chemical similarity based machine learning and label-free differential scanning fluorimetry were used to rapidly identify new ligands of the anticancer target Pim-1 kinase. The three-dimensional crystal structure complex of human Pim-1 with ligand bound revealed an ATP-competitive binding mode. Generative de novo design with a recurrent neural network additionally suggested innovative molecular scaffolds. Results corroborate the validity of the chemical similarity principle for rapid ligand prototyping, suggesting the complementarity of similarity-based and generative computational approaches.

Fructose-1, 6-bisphosphatase 1 interacts with NF-κB p65 to regulate breast tumorigenesis via PIM2 induced phosphorylation

Rationale: Fructose-1, 6-bisphosphatase 1 (FBP1), a rate-limiting enzyme in gluconeogenesis, was recently shown to be a tumor suppressor and could mediate the activities of multiple transcriptional factors via its non-canonical functions. However, the underlying mechanism of posttranscriptional modification on the non-canonical functions of FBP1 remains elusive.

Methods: We employed immunoaffinity purification to identify binding partner(s) and used co-immunoprecipitation to verify their interactions. Kinase reaction was used to confirm PIM2 could phosphorylate FBP1. Overexpression or knockdown proteins were used to assess the role in modulating p65 protein stability. Mechanistic analysis was involved in protein degradation and polyubiquitination assays. Nude mice and PIM2-knockout mice was used to study protein functions in vitro and in vivo.

Results: Here, we identified Proviral Insertion in Murine Lymphomas 2 (PIM2) as a new binding partner of FBP1, which could phosphorylate FBP1 on Ser144. Surprisingly, phosphorylated FBP1 Ser144 abrogated its interaction with NF-κB p65, promoting its protein stability through the CHIP-mediated proteasome pathway. Furthermore, phosphorylation of FBP1 on Ser144 increased p65 regulated PD-L1 expression. As a result, phosphorylation of FBP1 on Ser144 promoted breast tumor growth in vitro and in vivo. Moreover, the levels of PIM2 and pSer144-FBP1 proteins were positively correlated with each other in human breast cancer and PIM2 knockout mice.

Conclusions: Our findings revealed that phosphorylation noncanonical FBP1 by PIM2 was a novel regulator of NF-κB pathway, and highlights PIM2 inhibitors as breast cancer therapeutics.

Structure-Based Optimization of 10-DEBC Derivatives as Potent and Selective Pim-1 Kinase Inhibitors

Pim-1 kinase has been widely regarded as an attractive target for anticancer drugs. Here, we reported our continued efforts in structure-based optimization of compound 10-DEBC, a previously identified micromolar Pim-1 inhibitor. Guided by the Site Identification by Ligand Competitive Saturation (SILCS) method, we quickly obtained a series of 10-DEBC derivatives with significantly improved activity and selectivity. In particular, compound 26 exhibited an IC₅₀ value of 0.9 nM, as well as 220- and 8-fold selectivity over Pim-2 and Pim-3 kinases, respectively.

A serine/threonine protein PIM kinase as a biomarker of cancer and a target for anti-tumor therapy

The PIM Kinases belong to the family of a proto-oncogene that essentially phosphorylates the serine/threonine residues of the target proteins. They are primarily categorized into three types PIM-1, PIM-2, PIM-3 which plays an indispensable regulatory role in signal transduction cascades, by promoting cell survival, proliferation, and drug resistance. These kinases are overexpressed in several solid as well as hematopoietic tumors which supports in vitro and in vivo malignant cell growth along with survival by regulating cell cycle and inhibiting apoptosis. They lack regulatory domain which makes them constitutively active once transcribed. PIM kinases usually appear to be important downstream effectors of oncoproteins which overexpresses and helps in mediating drug resistance to available agents, such as rapamycin. Structural studies of PIM kinases revealed that they have unique hinge regions where two Proline resides and makes ATP binding unique, by offering a target for an increasing number of potent PIM kinase inhibitors. Preclinical studies of those inhibitory compounds in various cancers indicate that these novel agents show promising activity and some of them currently being under examination. In this review, we have outlined PIM kinases molecular mechanism and signaling pathways along with matriculation in various cancer and list of inhibitors often used.

AlloMAPS: allosteric mutation analysis and polymorphism of signaling database

AlloMAPS database provides data on the causality and energetics of allosteric communication obtained with the structure-based statistical mechanical model of allostery (SBSMMA). The database contains data on allosteric signaling in three sets of proteins and protein chains: (i) 46 proteins with comprehensively annotated functional and allosteric sites; (ii) 1908 protein chains from PDBselect set of chains with low (<25%) sequence identity; (iii) 33 proteins with more than 50 known pathological SNPs in each molecule. In addition to energetics of allosteric signaling between known functional and regulatory sites, allosteric modulation caused by the binding to these sites, by SNPs, and by mutations designated by the user can be explored. Allosteric Signaling Maps (ASMs), which are produced via the exhaustive computational scanning for stabilizing and destabilizing mutations and for the modulation range caused by the sequence position are available for each protein/protein chain in the database. We propose to use this database for evaluating the effects of allosteric signaling in the search for latent regulatory sites and in the design of allosteric sites and effectors. The database is freely available at: http://allomaps.bii.a-star.edu.sg.

PIM-1 Is Overexpressed at a High Frequency in Circulating Tumor Cells from Metastatic Castration-Resistant Prostate Cancer Patients

PIM-1 is an oncogene involved in cell cycle progression, cell growth, cell survival and therapy resistance, activated in many types of cancer, and is now considered as a very promising target for cancer therapy. We report for the first time that PIM-1 is overexpressed in circulating tumor cells (CTCs) from metastatic castration-resistant prostate cancer patients (mCRPC). We first developed and validated a highly sensitive RT-qPCR assay for quantification of PIM-1 transcripts. We further applied this assay to study PIM-1 expression in EpCAM⁽⁺⁾ CTC fraction isolated from 64 peripheral blood samples of 50 mCRPC patients. CTC enumeration in all samples was performed using the FDA-cleared CellSearch^® system. PIM-1 overexpression was detected in 24/64 (37.5%) cases, while in 20/24 (83.3%) cases that were positive for PIM-1 expression, at least one CTC/7.5 mL PB was detected in the CellSearch^®. Our data indicate that PIM-1 overexpression is observed at high frequency in CTCs from mCRPC patients and this finding, in combination with androgen receptor splice variant 7 (AR-V7) expression in CTCs, suggest its potential role as a very promising target for cancer therapy. We strongly believe that PIM-1 overexpression in EpCAM⁽⁺⁾ CTC fraction merits to be further evaluated and validated as a non-invasive circulating tumor biomarker in a large and well-defined patient cohort with mCRPC.

Molecular docking-based classification and systematic QSAR analysis of indoles as Pim kinase inhibitors

Pim kinase enzyme has an essential role in the treatment of prostate, colon and acute myeloid leukaemia cancers. The indoles inhibitors were docked in the enzyme's active pocket in order to survey the inhibition mechanism and extract the ligands' conformations. The docking outcome shows that the active inhibitors have strong van der Waals interactions with residues of Ile185, Leu44, Leu120 and Leu174, hydrogen bonds with residues of Asp128, Arg122 and Glu171 and π-π interaction with the residue of Phe49. The sum of these interactions is ~80 kcal mol^-1 contributing ~90% of total binding free energies. Using docking-based molecular descriptors, the unsupervised and supervised classifications were successfully carried out with the accuracy of 0.82 and 0.95, respectively, to categorize the active/inactive Pim kinase inhibitors. The vigorous quantitative assessment was performed using different machine learning techniques. The constructed QSAR model [(r ² _cal, r ² _p, r ² _m and Q ² _LOO) > 0.80 and (SE _cal, SE_p and SE _LOO) < 0.22] indicates that the molecular descriptors of nN, RDF20v and E1v can describe both the inhibition activities and the inhibition mechanism. The adequate evaluations of the molecular docking, classifications and QSAR analysis show that the current approaches can be used as valuable tools to design more effective new Pim kinase inhibitors for cancer treatment.

RNA-Seq analysis reveals that spring viraemia of carp virus induces a broad spectrum of PIM kinases in zebrafish kidney that promote viral entry

PIM kinases are a family of serine/threonine protein kinases that potentiate the progression of the cell cycle and inhibit apoptosis. Because of this, they are considered to be proto-oncogenes, and they represent an interesting target for the development of anticancer drugs. In mammals, three PIM kinases exist (PIM-1, PIM-2 and PIM-3), and different inhibitors have been developed to block their activity. In addition to their involvement in cancer, some publications have reported that the PIM kinases have pro-viral activity, and different mechanisms where PIM kinases favour viral infections have been proposed. Zebrafish possess more than 300 Pim kinase members in their genome, and by using RNA-Seq analysis, we found a high number of Pim kinase genes that were significantly induced after infection with spring viraemia of carp virus (SVCV). Moreover, analysis of the miRNAs modulated by this infection revealed that some of them could be involved in the post-transcriptional regulation of Pim kinase abundance. To elucidate the potential role of the 16 overexpressed Pim kinases in the infectivity of SVCV, we used three different pan-PIM kinase inhibitors (SGI-1776, INCB053914 and AZD1208), and different experiments were conducted both in vitro and in vivo. We observed that the PIM kinase inhibitors had a protective effect against SVCV, indicating that, similar to what is observed in mammals, PIM kinases are beneficial for the virus in zebrafish. Moreover, zebrafish Pim kinases seem to facilitate viral entry into the host cells because when ZF4 cells were pre-incubated with the virus and then were treated with the inhibitors, the protective effect of the inhibitors was abrogated. Although more investigation is necessary, these results show that pan-PIM kinase inhibitors could serve as a useful treatment for preventing the spread of viral diseases.

PIM1 inhibitor synergizes the anti-tumor effect of osimertinib via STAT3 dephosphorylation in EGFR-mutant non-small cell lung cancer

Background

An increasing amount of evidence has demonstrated that combined or multiple targeted therapies could bring about more durable clinical outcomes, and it is known that epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) resistance is related to bypass activation. This study aims to explore a specific solution for third-generation EGFR-TKI resistance caused by bypass activation, and to examine the antitumor effects of the combination of a novel inhibitor CX-6258 HCl with osimertinib, along with its underlining mechanisms.

Methods

A bioinformatics analysis was performed to detect the relations between the provirus integration site for Moloney murine leukemia virus 1 (PIM1) expression and prognosis of lung cancer. The EGFR-mutated lung cancer cell lines were treated with the combination of CX-6258 HCl and osimertinib to analyze cell proliferation using the Cell Counting Kit-8, colony formation, and in vivo experiments. Cell migration was analyzed using wound healing and Transwell assays. The apoptosis level was detected using Annexin V-propidium iodide flow cytometry. The expression levels of EGFR and STAT3 were determined using Western blot analysis.

Results

High expression level of PIM1 was related to the poor prognosis of non-small cell lung cancer (NSCLC). The combined administration of osimertinib and CX-6258 HCl significantly inhibited cell proliferation and migration and effectively induced apoptosis in lung cancer cells. It was more efficient in suppressing EGFR activation and phosphorylation of STAT3 compared with osimertinib treatment alone. Furthermore, it showed a durable efficacy in a xenograft model.

Conclusions

This study showed that PIM1 is a poor prognostic factor for NSCLC. CX-6258 HCl is a potential molecular inhibitor to sensitize the antitumor effects of osimertinib through the inhibiting of the phosphorylation of STAT3 in NSCLC.

Preclinical evaluation of a novel triple-acting PIM/PI3K/mTOR inhibitor, IBL-302, in breast cancer

The proviral integration of Moloney virus (PIM) family of protein kinases are overexpressed in many haematological and solid tumours. PIM kinase expression is elevated in PI3K inhibitor-treated breast cancer samples, suggesting a major resistance pathway for PI3K inhibitors in breast cancer, potentially limiting their clinical utility. IBL-302 is a novel molecule that inhibits both PIM and PI3K/AKT/mTOR signalling. We thus evaluated the preclinical activity of IBL-302, in a range of breast cancer models. Our results demonstrate in vitro efficacy of IBL-302 in a range of breast cancer cell lines, including lines with acquired resistance to trastuzumab and lapatinib. IBL-302 demonstrated single-agent, anti-tumour efficacy in suppression of pAKT, pmTOR and pBAD in the SKBR-3, BT-474 and HCC-1954 HER2+/PIK3CA-mutated cell lines. We have also shown the in vivo single-agent efficacy of IBL-302 in the subcutaneous BT-474 and HCC-1954 xenograft model in BALB/c nude mice. The combination of trastuzumab and IBL-302 significantly increased the anti-proliferative effect in HER2+ breast cancer cell line, and matched trastuzumab-resistant line, relative to testing either drug alone. We thus believe that the novel PIM and PI3K/mTOR inhibitor, IBL-302, represents an exciting new potential treatment option for breast cancer, and that it should be considered for clinical investigation.

Proto-Oncogene Serine/Threonine Kinase PIM3 Promotes Cell Migration via Modulating Rho GTPase Signaling

The proto-oncogene serine/threonine-protein kinase PIM3 plays critical roles in cancer, and it has been extensively exploited as a drug target. Here, we investigated the quantitative changes in the cellular proteome and phosphoproteome in liver cancer cells overexpressing PIM3 to obtain a better understanding of the regulatory functions of PIM3 and the underlying molecular mechanisms. This work depicted the landscape of gene expression and protein phosphorylation potentially regulated by PIM3. A signaling network analysis showed that PIM3 may coordinate various cellular processes, for example, signal transduction, cell cycle, apoptosis, and so forth. Intriguingly, quantitative phosphoproteomics revealed that the PIM3 overexpression elevated the phosphorylation of multiple Rho GTPase modulators that target RhoA, a central modulator of cell movement. Further investigations confirmed that PIM3 activated RhoA to subsequently regulate cytoskeletal rearrangements and cell migration. Taken together, this study comprehensively mapped the proteome and phosphoproteome regulated by PIM3 and revealed its role in promoting liver cancer cell migration and invasion by modulating Rho GTPase signaling.

PIM kinase inhibition: co-targeted therapeutic approaches in prostate cancer

PIM kinases have been shown to play a role in prostate cancer development and progression, as well as in some of the hallmarks of cancer, especially proliferation and apoptosis. Their upregulation in prostate cancer has been correlated with decreased patient overall survival and therapy resistance. Initial efforts to inhibit PIM with monotherapies have been hampered by compensatory upregulation of other pathways and drug toxicity, and as such, it has been suggested that co-targeting PIM with other treatment approaches may permit lower doses and be a more viable option in the clinic. Here, we present the rationale and basis for co-targeting PIM with inhibitors of PI3K/mTOR/AKT, JAK/STAT, MYC, stemness, and RNA Polymerase I transcription, along with other therapies, including androgen deprivation, radiotherapy, chemotherapy, and immunotherapy. Such combined approaches could potentially be used as neoadjuvant therapies, limiting the development of resistance to treatments or sensitizing cells to other therapeutics. To determine which drugs should be combined with PIM inhibitors for each patient, it will be key to develop companion diagnostics that predict response to each co-targeted option, hopefully providing a personalized medicine pathway for subsets of prostate cancer patients in the future.

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.

Inhibition of PIM2 in liver cancer decreases tumor cell proliferation in vitro and in vivo primarily through the modulation of cell cycle progression

Liver cancer is the fourth leading cause of cancer-related mortality worldwide with limited therapeutic options. Thus, novel treatment strategies are urgently required. While the oncogenic kinase, proviral integration site for Moloney murine leukemia virus 2 (PIM2), has been shown to be overexpressed in liver cancer, little is known about the role of PIM2 in this tumor entity. In this study, we explored the functional relevance and therapeutic potential of PIM2 in liver cancer. Using PIM2-specific siRNAs, we examined the effects of PIM2 knockdown on proliferation (WST-1 assays and spheroid assays), 3D-colony formation and colony spread, apoptosis (flow cytometry and caspase 3/caspase 7 activity), as well as cell cycle progression (flow cytometry, RT-qPCR and western blot analysis) in the two liver cancer cell lines, HepG2 and Huh-7. In subcutaneous liver cancer xenografts, we assessed the effects of PIM2 knockdown on tumor growth via the systemic delivery of polyethylenimine (PEI)-complexed siRNA. The knockdown of PIM2 resulted in potent anti-proliferative effects in cells grown on plastic dishes, as well as in spheroids. This was due to G0/G1 cell cycle blockade and the subsequent downregulation of genes related to the S phase as well as the G2/M phase of the cell cycle, whereas the apoptotic rates remained unaltered. Furthermore, colony formation and colony spread were markedly inhibited by PIM2 knockdown. Notably, we found that HepG2 cells were more sensitive to PIM2 knockdown than the Huh-7 cells. In vivo, the therapeutic nanoparticle-mediated delivery of PIM2 siRNA led to profound anti-tumor effects in a liver cancer xenograft mouse model. On the whole, the findings of this study underscore the oncogenic role of PIM2 and emphasize the potential of targeted therapies based on the specific inhibition of PIM2 in liver cancer.

Downregulation of microRNA-124 prevents the development of acute liver failure through the upregulation of PIM-3

NEW FINDINGS

• What is the central question of this study? Does miR-124 affect cell proliferation and apoptosis in acute liver failure (ALF) mice? • What is the main finding and its importance? Inhibiting miR-124 targets PIM-3 and thus upregulates its expression, consequently inhibiting liver cell apoptosis and promoting cell proliferation, ultimately preventing the progression of ALF. This highlights a promising competitive new target for ALF treatment.

ABSTRACT

Acute liver failure (ALF) is a complicated syndrome frequently leading to dysfunction and failure of various organs. MicroRNAs (miRNAs) have played crucial roles in the development and progression of human diseases, including ALF. However, the potential role of miR-124 in ALF still remains elusive. Thus, we investigated the underlying mechanism by which miR-124 influences ALF in a mouse model of ALF. Initially, ALF mouse models were established using d-galactosamine and lipopolysaccharide. Then we detected the serum biochemical parameters of liver, and pathological characteristics and ultrastructure of liver tissues. Next, we determined miR-124 and PIM-3 expression in liver tissues and cells using RT-qPCR and western blot analysis. The interaction between miR-124 and PIM-3 was identified using the dual luciferase reporter gene assay. Subsequently, expression of miR-124 and PIM-3 in liver cells was altered to explore their effects on primary liver cell proliferation, the cell cycle and apoptosis. The results obtained showed that ALF mice exhibited a decreased cholinesterase level with increased levels of alanine aminotransferase, aspartate transaminase and total bilirubin as well as abundant liver cell apoptosis and necrosis. miR-124 was upregulated while PIM-3 was downregulated in ALF tissues and cells. Besides, the PIM-3 gene was a target of miR-124 and was inhibited by miR-124. Overexpression of miR-124 or silencing of PIM-3 reduced Bcl-2 expression but elevated tumour necrosis factor α expression, and resulted in a reduction in liver cell proliferation but an increase in cell apoptosis in ALF mice. Altogether, miR-124 functions as a disease-promoting miRNA with potential in stimulating ALF by targeting PIM-3.

The Oncogene PIM1 Contributes to Cellular Senescence by Phosphorylating Staphylococcal Nuclease Domain-Containing Protein 1 (SND1)

Background

The oncogene PIM1, encoding a constitutively active serine/threonine protein kinase, is involved in the regulation of cell proliferation, survival, differentiation, and apoptosis. There is a growing body of literature on the role of PIM1-mediated cellular senescence, but the precise mechanism remains unclear.

Material/Methods

Silver staining and LC–MS/MS analysis were performed to investigate the protein interacting with PIM1. Immunofluorescence, Co-IP, and Western blot assay were used to assess the interaction of PIM1 and SND1. EdU incorporation and CCK8 assay were used to detect cell proliferation and immunohistochemistry was used to detect the level of the indicated protein.

Results

We found that PIM1 can bind directly and phosphorylate SND1. In addition, decreased expression of SND1 leads to the upregulation of SASP. SND1 is involved in cellular senescence induced by PIM1.

Conclusions

We investigated the role of PIM1 in oncogene-induced normal cellular senescence. Our results promote further understanding of the mechanisms underlying OIS and suggest potential applications for preventing tumorigenesis.

Pim-3 alleviates lipopolysaccharide-stimulated AR42J pancreatic acinar cell injury via improving the inflammatory microenvironment

Acute pancreatitis (AP) is a common acute abdominal disease characterized by pancreatic aseptic inflammation, with ~20% of patients progressing to severe AP (SAP) with a high mortality rate. The aim of this study was to explore the protective effects of Pim-3 proto-oncogene, serine/threonine kinase (Pim-3) on rat pancreatic acinar AR4-2J cells damaged by lipopolysaccharide (LPS). The recombinant plasmid p-enhanced green fluorescent protein (pEGFP)-N2/Pim-3 was transiently transfected into AR42J cells and the AR42J cells were then treated with 2 µg/ml LPS. Subsequently, the proliferation of AR42J cells was detected using MTT assay. The cell cycle progression and apoptosis rate of the AR42J cells were examined using flow cytometry. AR42J cell migration was assessed using wound healing assays. Additionally, RT-semi quantitative PCR and western blot analyses were used to detect the mRNA and protein expression levels, respectively, of Pim-3, interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1 and Occludin in AR42J cells. The results revealed that proliferation of AR42J cells was significantly enhanced and cell apoptosis was markedly reduced in the pEGFP-N2/Pim-3 + LPS group. The proportion of AR42J cells in G1 phase in the pEGFP-N2/Pim-3 + LPS group was decreased, whereas the proportion of cells in the G2 and S phases was increased. The wound healing assays demonstrated that AR42J cell migration was significantly increased in the pEGFP-N2/Pim-3 + LPS group. Finally, the expression levels of IL-6, IL-1β, TNF-α and ICAM-1 were significantly decreased in the pEGFP-N2/Pim-3 + LPS group, whereas the expression of Occludin was significantly increased. The present study demonstrated that raised expression levels of Pim-3 can protect AR42J cells from LPS-induced injury by modifying the inflammatory microenvironment, suggesting that Pim-3 may be a potential target for AP or SAP therapy.

AhR Activation Leads to Massive Mobilization of Myeloid-Derived Suppressor Cells with Immunosuppressive Activity through Regulation of CXCR2 and MicroRNA miR-150-5p and miR-543-3p That Target Anti-Inflammatory Genes

The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an environmental contaminant, is a potent ligand for aryl hydrocarbon receptor (AhR). In the current study, we made an exciting observation that naive C57BL/6 mice that were exposed i.p. to TCDD showed massive mobilization of myeloid-derived suppressor cells (MDSCs) in the peritoneal cavity. These MDSCs were highly immunosuppressive and attenuated Con A-induced hepatitis upon adoptive transfer. TCDD administration in naive mice also led to induction of several chemokines and cytokines in the peritoneal cavity and serum (CCL2, CCL3, CCL4, CCL11, CXCL1, CXCL2, CXCL5, CXCL9, G-CSF, GM-CSF, VEGF, and M-CSF) and chemokine receptors on MDSCs (CCR1, CCR5, and CXCR2). Treatment with CXCR2 or AhR antagonist in mice led to marked reduction in TCDD-induced MDSCs. TCDD-induced MDSCs had high mitochondrial respiration and glycolytic rate and exhibited differential microRNA (miRNA) expression profile. Specifically, there was significant downregulation of miR-150-5p and miR-543-3p. These two miRNAs targeted and enhanced anti-inflammatory and MDSC-regulatory genes, including IL-10, PIM1, ARG2, STAT3, CCL11 and its receptors CCR3 and CCR5 as well as CXCR2. The role of miRs in MDSC activation was confirmed by transfection studies. Together, the current study demonstrates that activation of AhR in naive mice triggers robust mobilization of MDSCs through induction of chemokines and their receptors and MDSC activation through regulation of miRNA expression. AhR ligands include diverse compounds from environmental toxicants, such as TCDD, that are carcinogenic to dietary indoles that are anti-inflammatory. Our studies provide new insights on how such ligands may regulate health and disease through induction of MDSCs.

Phosphorylation of HSF1 by PIM2 Induces PD-L1 Expression and Promotes Tumor Growth in Breast Cancer

Heat shock transcription factor 1 (HSF1) is the master regulator of the proteotoxic stress response, which plays a key role in breast cancer tumorigenesis. However, the mechanisms underlying regulation of HSF1 protein stability are still unclear. Here, we show that HSF1 protein stability is regulated by PIM2-mediated phosphorylation of HSF1 at Thr120, which disrupts the binding of HSF1 to the E3 ubiquitin ligase FBXW7. In addition, HSF1 Thr120 phosphorylation promoted proteostasis and carboplatin-induced autophagy. Interestingly, HSF1 Thr120 phosphorylation induced HSF1 binding to the PD-L1 promoter and enhanced PD-L1 expression. Furthermore, HSF1 Thr120 phosphorylation promoted breast cancer tumorigenesis in vitro and in vivo. PIM2, pThr120-HSF1, and PD-L1 expression positively correlated with each other in breast cancer tissues. Collectively, these findings identify PIM2-mediated HSF1 phosphorylation at Thr120 as an essential mechanism that regulates breast tumor growth and potential therapeutic target for breast cancer. SIGNIFICANCE: These findings identify heat shock transcription factor 1 as a new substrate for PIM2 kinase and establish its role in breast tumor progression.

The serine-threonine kinase PIM3 is an aldosterone-regulated protein in the distal nephron

The mineralocorticoid hormone aldosterone plays a crucial role in the control of Na+ and K+ balance, blood volume, and arterial blood pressure, by acting in the aldosterone-sensitive distal nephron (ASDN) and stimulating a complex transcriptional, translational, and cellular program. Because the complexity of the aldosterone response is still not fully appreciated, we aimed at identifying new elements in this pathway. Here, we demonstrate that the expression of the proto-oncogene PIM3 (Proviral Integration Site of Moloney Murine Leukemia Virus 3), a serine/threonine kinase belonging to the calcium/calmodulin-regulated group of kinases, is stimulated by aldosterone in vitro (mCCDcl1 cells), ex vivo (mouse kidney slices), and in vivo in mice. Characterizing a germline Pim3-/- mouse model, we found that these mice have an upregulated Renin-Angiotensin-Aldosterone System (RAAS), with high circulating aldosterone and plasma renin activity levels on both standard or Na+ -deficient diet. Surprisingly, we did not observe any obvious salt-losing phenotype in Pim3 KO mice as shown by normal blood pressure, plasma and urinary electrolytes, as well as unchanged expression levels of the major Na+ transport proteins. These observations suggest that the potential effects of the loss of the Pim3 gene are physiologically compensated. Indeed, the 2 other family members of the PIM kinase family, PIM1 and PIM2 are upregulated in the kidney of Pim3-/- mice, and may therefore be involved in such compensation. In conclusion, our data demonstrate that the PIM3 kinase is a novel aldosterone-induced protein, but its precise role in aldosterone-dependent renal homeostasis remains to be determined.

Negative regulation of AMPKα1 by PIM2 promotes aerobic glycolysis and tumorigenesis in endometrial cancer

Endometrial cancer (EC) is one of the most common gynecologic malignancies. However, the molecular mechanisms underlying the development and progression of EC remain unclear. Here, we demonstrated that the protein proviral insertion in murine lymphomas 2 (PIM2) was necessary for maintaining EC tumorigenesis in vivo and in vitro, and could inhibit AMPKα1 kinase activity in EC cells. Specifically, we found that PIM2 bound to AMPKα1, and directly phosphorylated it on Thr467. Phosphorylation of AMPKα1 by PIM2 led to decreasing AMPKα1 kinase activity, which in turn promoted aerobic glycolysis and tumor growth. In addition, PIM2 expression positively correlated with AMPKα1 Thr467 phosphorylation in EC tissues. Further, treatment with a combination of the PIM2 inhibitor SMI-4a and the AMPKα1 activator AICAR could effectively inhibit tumor growth. Thus, our findings provide insight into the role of PIM2 and AMPKα1 in EC and suggest that combination targeting of these proteins may represent a new strategy for EC treatment.

In Vitro and In Vivo Anti-Breast Cancer Activities of Some Newly Synthesized 5-(thiophen-2-yl)thieno-[2,3-d]pyrimidin-4-one Candidates

In this study, some of new thiophenyl thienopyrimidinone derivatives 2–15 were prepared and tested as anti-cancer agents by using thiophenyl thieno[2,3-d]pyrimidinone derivative 2 as a starting material, which was prepared from cyclization of ethyl ester derivative 1 with formamide. Treatment of 2 with ethyl- chloroacetate gave thienopyrimidinone N-ethylacetate 3, which was reacted with hydrazine hydrate or anthranilic acid to afford acetohydrazide 4 and benzo[d][1,3]oxazin-4-one 5, respectively. Condensation of 4 with aromatic aldehydes or phenylisothiocyanate yielded Schiff base derivatives 6,7, and thiosemicarbazise 10, which were treated with 2-mercaptoacetic acid or chloroacetic acid to give the corresponding thiazolidinones 8, 9, and phenylimino-thiazolidinone 11, respectively. Treatment of 4 with ethylacetoacetate or acetic acid/acetic anhydride gave pyrazole 12 and acetyl acetohydrazide 13 derivatives, respectively. The latter compound 13 was reacted with ethyl cycno-acetate or malononitrile to give 14 and 15, respectively. In this work, we have studied the anti-cancer activity of the synthesized thienopyrimidinone derivatives against MCF-7 and MCF-10A cancer cells. Furthermore, in vivo experiments showed that the synthesized compounds significantly reduced tumor growth up to the 8^th day of treatment in comparison to control animal models. Additionally, the synthesized derivatives showed potential inhibitory effects against pim-1 kinase activities.

The presence of PIM3 increases hepatoblastoma tumorigenesis and tumor initiating cell phenotype and is associated with decreased patient survival

PURPOSE

Hepatoblastoma is the most common primary liver cancer of childhood and has few prognostic indicators. We have previously shown that Proviral Integration site for Moloney murine leukemia virus (PIM3) kinase decreased hepatoblastoma tumorigenicity. We sought to determine the effect of PIM3 overexpression on hepatoblastoma cells and whether expression of PIM3 correlated with patient/tumor characteristics or survival.

METHODS

The hepatoblastoma cell line, HuH6, and patient-derived xenograft, COA67, were utilized. Viability, proliferation, migration, sphere formation, and tumor growth in mice were assessed in PIM3-overexpressing cells. Immunohistochemistry was performed for PIM3 on patient samples. Correlation between stain score and clinical/pathologic characteristics was assessed.

RESULTS

PIM3 overexpression rescued the anti-proliferative effect observed with PIM3 knockdown. Sphere formation was increased in PIM3 overexpressing cells. Cells with PIM3 overexpression yielded larger tumors than those with empty vector. Seventy-four percent of samples expressed PIM3. There was no statistical difference in patient characteristics between subjects with strong versus weak PIM3 staining, but patients with strong PIM3 staining had decreased survival.

CONCLUSIONS

PIM3 expression plays a role in hepatoblastoma tumorigenesis. PIM3 was present in the majority of hepatoblastomas and higher PIM3 expression correlated with decreased survival. PIM3 warrants investigation as a therapeutic target and prognostic marker for hepatoblastoma.

PIM1-catalyzed CBX8 phosphorylation promotes the oncogene-induced senescence of human diploid fibroblast

The proto-oncogene PIM1 encodes Ser/Thr kinase and regulates cell growth, differentiation and apoptosis. However, more and more studies including ours have found that PIM1 can induce senescence in normal human diploid fibroblasts and behave as a tumor suppressor. But the relevant molecular mechanism of this process is not yet clear. It has been reported that Chromobox homolog 8 (CBX8) binds directly to INK4A as a transcriptional repressor, thereby suppressing stress-induced senescence. Here we report that PIM1 can phosphorylate CBX8 to promote its degradation, thereby up-regulating p16, during PIM1-induced cell senescence. Overexpression of CBX8 can inhibit PIM1-induced cell senescence. These data suggest that to promote CBX8 degradation may be an important molecular mechanism of PIM1-induced cell senescence.

High expression of PIM2 induces HSC proliferation in myelodysplastic syndromes via the IDH1/HIF1-α signaling pathway

PIM2 proto-oncogene, serine/threonine kinase (PIM2) is a serine/threonine protein kinase that is upregulated in different types of cancer and serves essential roles in the regulation of signal transduction cascades, which promote cell survival and cell proliferation. The present study demonstrated that PIM2 was highly expressed in CD34⁺ cells derived from the bone marrow of patients with myelodysplastic syndromes (MDS)/acute myeloid leukemia. The mRNA expression level of PIM2 was quantified in MDS cell lines and mRNA expression was significantly decreased compared with that in KG-1 cells. In vitro, downregulation of PIM2 by short interfering RNA (siRNA) inhibited cell proliferation and delayed G₀/G₁ cell cycle progression in the MDS cell line SKM-1. Western blotting revealed that cyclin dependent kinase 2 was markedly downregulated and cyclin dependent kinase inhibitor 1A was markedly upregulated following transfection with PIM2 siRNA. Cell Counting Kit-8 analysis demonstrated that cell proliferation of si-PIM2-transfected cells was significantly decreased compared with control cells. Reverse-transcription quantitative polymerase chain reaction and western blotting revealed that PIM2 expression was negatively correlated with isocitrate dehydrogenase [NADP(+)]1 cytosolic (IDH1) and positively correlated with hypoxia inducible factor 1 subunit α (HIF1A) in CD34⁺ MDS cells. Collectively, these results suggested that the expression of PIM2 induced increased expression of HIF1A by decreasing the expression of IDH1, resulting in increased CD34⁺ cell proliferation. Therefore, PIM2 may be a potential biomarker for the diagnosis of MDS and AML or a target for novel therapeutic agents.

Macrophages Infected by a Pathogen and a Non-pathogen Spotted Fever Group Rickettsia Reveal Differential Reprogramming Signatures Early in Infection

Despite their high degree of genomic similarity, different spotted fever group (SFG) Rickettsia are often associated with very different clinical presentations. For example, Rickettsia conorii causes Mediterranean spotted fever, a life-threatening disease for humans, whereas Rickettsia montanensis is associated with limited or no pathogenicity to humans. However, the molecular basis responsible for the different pathogenicity attributes are still not understood. Although killing microbes is a critical function of macrophages, the ability to survive and/or proliferate within phagocytic cells seems to be a phenotypic feature of several intracellular pathogens. We have previously shown that R. conorii and R. montanensis exhibit different intracellular fates within macrophage-like cells. By evaluating early macrophage responses upon insult with each of these rickettsial species, herein we demonstrate that infection with R. conorii results in a profound reprogramming of host gene expression profiles. Transcriptional programs generated upon infection with this pathogenic bacteria point toward a sophisticated ability to evade innate immune signals, by modulating the expression of several anti-inflammatory molecules. Moreover, R. conorii induce the expression of several pro-survival genes, which may result in the ability to prolong host cell survival, thus protecting its replicative niche. Remarkably, R. conorii-infection promoted a robust modulation of different transcription factors, suggesting that an early manipulation of the host gene expression machinery may be key to R. conorii proliferation in THP-1 macrophages. This work provides new insights into the early molecular processes hijacked by a pathogenic SFG Rickettsia to establish a replicative niche in macrophages, opening several avenues of research in host-rickettsiae interactions.

PIM kinase inhibitors: Structural and pharmacological perspectives

The PIM kinase, also known as serine/threonine kinase plays an important role in cancer biology and is found in three different isoforms namely PIM-1, PIM-2, and PIM-3. They are extensively distributed and are implicated in a variety of biological processes, including cell proliferation, cell differentiation, and apoptosis. They act as weak oncogene and whenever expressed in exacerbating forms are responsible for different types of human cancer. Recently, different isoforms of PIM kinase have been identified as a clinical biomarker and potential therapeutic target for personalized treatment of advanced cancer. The inhibition of PIM kinase has become a scientific interest and some inhibitors have been developed and/or are under different phases of clinical trials. Several medicinally privileged heterocyclic ring scaffolds such as pyrrole, pyrimidine, thiazolidine, benzofuran, indole, triazole, oxadiazole, and quinoline derivatives have been synthesized and evaluated for their PIM inhibitory activity. This review comprehensively focuses on pharmacological implications of PIM kinases in oncogenesis, structural insights of PIM inhibitors and their structure-activity relationships (SARs).

Discovery of novel triazolo[4,3-b]pyridazin-3-yl-quinoline derivatives as PIM inhibitors

PIM kinase family (PIM-1, PIM-2 and PIM-3) is an appealing target for the discovery and development of selective inhibitors, useful in various disease conditions in which these proteins are highly expressed, such as cancer. The significant effort put, in the recent years, towards the development of small molecules exhibiting inhibitory activity against this protein family has ended up with several molecules entering clinical trials. As part of our ongoing exploration for potential drug candidates that exhibit affinity towards this protein family, we have generated a novel chemical series of triazolo[4,3-b]pyridazine based tricycles by applying a scaffold hopping strategy over our previously reported potent pan-PIM inhibitor ETP-47453 (compound 2). The structure-activity relationship studies presented herein demonstrate a rather selective PIM-1/PIM-3 biochemical profile for this novel series of tricycles, although pan-PIM and PIM-1 inhibitors have also been identified. Selected examples show significant inhibition of the phosphorylation of BAD protein in a cell-based assay. Moreover, optimized and highly selective compounds, such as 42, did not show significant hERG inhibition at 20 μM concentration, and proved its antiproliferative activity and utility in combination with particular antitumoral agents in several tumor cell lines.

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.

Identification and targeting of novel CDK9 complexes in acute myeloid leukemia

Aberrant activation of mTOR signaling in acute myeloid leukemia (AML) results in a survival advantage that promotes the malignant phenotype. To improve our understanding of factors that contribute to mammalian target of rapamycin (mTOR) signaling activation and identify novel therapeutic targets, we searched for unique interactors of mTOR complexes through proteomics analyses. We identify cyclin dependent kinase 9 (CDK9) as a novel binding partner of the mTOR complex scaffold protein, mLST8. Our studies demonstrate that CDK9 is present in distinct mTOR-like (CTOR) complexes in the cytoplasm and nucleus. In the nucleus, CDK9 binds to RAPTOR and mLST8, forming CTORC1, to promote transcription of genes important for leukemogenesis. In the cytoplasm, CDK9 binds to RICTOR, SIN1, and mLST8, forming CTORC2, and controls messenger RNA (mRNA) translation through phosphorylation of LARP1 and rpS6. Pharmacological targeting of CTORC complexes results in suppression of growth of primitive human AML progenitors in vitro and elicits strong antileukemic responses in AML xenografts in vivo.

PIM1 kinase promotes cell proliferation, metastasis and tumor growth of lung adenocarcinoma by potentiating the c-MET signaling pathway

The proto-oncogene PIM1 plays essential roles in proliferation, survival, metastasis and drug resistance in hematopoietic and solid tumors. Although PIM1 has been shown to be associated with lymph node metastasis and poor prognosis in non-small cell lung cancer, its underlying molecular mechanisms in this context are still unclear. Here we show that PIM1 is frequently overexpressed in lung adenocarcinomas, and its expression level is associated with c-MET expression and poor clinical outcome. We further demonstrate that PIM1 may regulate c-MET expression via phosphorylation of eukaryotic translation initiation factor 4B (eIF4B) on S406. Depletion of PIM1 decreased cell proliferation, migration, invasion and colony formation in vitro, as well as reduced tumor growth in vivo. And these effects were partially abrogated by restoring of c-MET expression. Our study implicates a promising therapeutic approach in lung adenocarcinoma patients with PIM1 and c-MET overexpression.

Targeting PIM Kinases Affects Maintenance of CD133 Tumor Cell Population in Hepatoblastoma

Hepatoblastoma is the most common primary liver tumor in children, but treatment has not changed significantly in the past 20 years. We have previously demonstrated that Proviral Integration site for Moloney murine leukemia (PIM) kinases promote tumorigenesis in hepatoblastoma. Stem cell-like cancer cells (SCLCCs) are a subset of cells thought to be responsible for chemoresistance, metastasis, relapse, and recurrence. The aim of this study was to identify SCLCCs in hepatoblastoma and determine the role of PIM kinases in SCLCCs. Hepatoblastoma cells were separated into CD133-enriched and CD133-depleted populations and the frequency of SCLCCs was assessed. CD133 expression was determined in the presence or absence of the PIM inhibitor, AZD1208. The effects of AZD1208 on proliferation, apoptosis, and motility were assessed in vitro and the effect of AZD1208 on tumor growth was examined in vivo. We identified CD133 as a marker for SCLCCs in hepatoblastoma and showed that PIM kinases promote a SCLCC phenotype. PIM kinase inhibition with AZD1208 decreased proliferation, migration, and invasion and increased apoptosis in both SCLCCs and non-SCLCCs in a long-term passaged hepatoblastoma cell line and patient-derived xenograft. Additionally, tumor growth in mice implanted with hepatoblastoma SCLCCs was decreased with PIM inhibition such that 57% of the tumors regressed. These findings identify CD133 as a marker for SCLCCs in hepatoblastoma and provide evidence that inhibition of PIM kinases decreases stemness and tumorigenicity of SCLCCs in hepatoblastoma, making them potential therapeutic targets for the treatment of hepatoblastoma.

Inhibition of PIM1 blocks the autophagic flux to sensitize glioblastoma cells to ABT-737-induced apoptosis

Overcoming apoptosis resistance is one major issue in glioblastoma (GB) therapies. Accumulating evidence indicates that resistance to apoptosis in GB is mediated via upregulation of pro-survival BCL2-family members. The synthetic BH3-mimetic ABT-737 effectively targets BCL2, BCL2 like 1 and BCL2 like 2 but still barely affects cell survival which is presumably due to its inability to inhibit myeloid cell leukemia 1 (MCL1). The constitutively active serine/threonine kinase proviral integration site for moloney murine leukemia virus 1 (PIM1) was recently found to be overexpressed in GB patient samples and to maintain cell survival in these tumors. For different GB cell lines, Western Blot, mitochondrial fractionation, fluorescence microscopy, effector caspase assays, flow cytometry, and an adult organotypic brain slice transplantation model were used to investigate the putative PIM1/MCL1 signaling axis regarding potential synergistic effects with ABT-737. We demonstrate that combination of the PIM1 inhibitor SGI-1776 or the pan-PIM kinase inhibitor AZD1208 with ABT-737 strongly sensitizes GB cells to apoptosis. Unexpectedly, this effect was found to be MCL1-independent, but could be partially blocked by caspase 8 (CASP8) inhibition. Remarkably, the analysis of autophagy markers in combination with the observation of massive accumulation and hampered degradation of autophagosomes suggests a completely novel function of PIM1 as a late stage autophagy regulator, maintaining the autophagic flux at the level of autophagosome/lysosome fusion. Our data indicate that PIM1 inhibition and ABT-737 synergistically induce apoptosis in an MCL1-independent but CASP8-dependent manner in GB. They also identify PIM1 as a suitable target for overcoming apoptosis resistance in GB.

Pim1 promotes cell proliferation and regulates glycolysis via interaction with MYC in ovarian cancer

Background

Ovarian cancer (OC) is the leading cause of death among women with gynecologic malignancies. Recent studies have highlighted the role of Pim1, which belongs to a group of constitutively activated serine/threonine kinases, in cancer development. However, the effect of Pim1 in OC is largely unclear.

Methods

OC cell lines with Pim1 overexpression or knockdown were constructed with len-tivirus transduction. Cell Counting Kit-8, colony formation, glycolysis stress test and in vivo mice models were carried out to assess the effect of Pim1 on OC biological functions. Co-immunoprecipitation assay coupled with western blot were performed to explore the intrinsic mechanisms of Pim1 in OC. Bioinformatic analysis was then performed to evaluate the expression and prognostic value of Pim1.

Results

We present the first evidence that silencing or overexpressing Pim1 can suppress or promote, respectively, OC cell proliferation. Furthermore, we demonstrated that Pim1 can significantly enhance glycolysis in OC cells. In vivo experiments further confirmed that knockdown of Pim1 inhibits the growth of tumors derived from the SKOV3 cell line. To search for the underlying molecular mechanism, we examined the effect of Pim1 on MYC, a pivotal gene in glycolysis, and observed that Pim1-mediated phosphorylation of c-Myc activated the expression of glycolysis-associated key genes such as PGK1 and LDHA. Moreover, we found that the Pim1 inhibitor SMI4a induced chemosensitization to cisplatin. Clinically, Pim1 was also overexpressed in OC and correlated with poor overall survival by bioinformatics analysis.

Conclusion

Together, these results suggest that Pim1 contributes to proliferation and gly-colysis in OC via interaction with MYC and may serve as a potential target in the treatment of OC patients.

PIM2 survival kinase is upregulated in a p53-dependent manner in cells treated with camptothecin or co-treated with actinomycin D and nutlin-3a

The p53 protein is an inducer of apoptosis, acting as a transcriptional regulator of apoptotic genes. In a previous study, we found that actinomycin D and nutlin-3a (A + N) synergistically activate p53. To better understand the molecular consequences of this synergism, we incubated arrays of antibodies against apoptotic proteins with extracts of A549 cells in which p53 had been activated. We found that strong activation of p53, marked by serine 46 and 392 phosphorylation, was associated with inactivating phosphorylation of proapoptotic BAD protein on serine 136. Investigation of the source of this phosphorylation revealed that activation of p53 was associated with accumulation of PIM2, a survival kinase. The accumulation of PIM2 following treatment with A + N was suppressed in p53-knockdown cells. Others discovered that PIM2 was activated by cooperatively acting p53 molecules. Our results are consistent with this finding. Moreover, we found that in A549 cells, the treatment with A + N stimulated in p53-dependent fashion the expression of other high cooperativity p53 target genes, DRAXIN and H19. Activation of antiapoptotic H19 can mechanistically explain relatively low rate of apoptosis of A549 cells exposed to A + N. We conclude that PIM2, DRAXIN and H19 are efficiently stimulated by strongly activated p53 molecules, probably acting cooperatively.

PIM2-mediated phosphorylation of hexokinase 2 is critical for tumor growth and paclitaxel resistance in breast cancer

Hexokinase-II (HK2) is a key enzyme involved in glycolysis, which is required for breast cancer progression. However, the underlying post-translational mechanisms of HK2 activity are poorly understood. Here, we showed that Proviral Insertion in Murine Lymphomas 2 (PIM2) directly bound to HK2 and phosphorylated HK2 on Thr473. Biochemical analyses demonstrated that phosphorylated HK2 Thr473 promoted its protein stability through the chaperone-mediated autophagy (CMA) pathway, and the levels of PIM2 and pThr473-HK2 proteins were positively correlated with each other in human breast cancer. Furthermore, phosphorylation of HK2 on Thr473 increased HK2 enzyme activity and glycolysis, and enhanced glucose starvation-induced autophagy. As a result, phosphorylated HK2 Thr473 promoted breast cancer cell growth in vitro and in vivo. Interestingly, PIM2 kinase inhibitor SMI-4a could abrogate the effects of phosphorylated HK2 Thr473 on paclitaxel resistance in vitro and in vivo. Taken together, our findings indicated that PIM2 was a novel regulator of HK2, and suggested a new strategy to treat breast cancer.

Pan-Pim Kinase Inhibitor AZD1208 Suppresses Tumor Growth and Synergistically Interacts with Akt Inhibition in Gastric Cancer Cells

Purpose

Pim kinases are highly conserved serine/threonine kinases, and different expression patterns of each isoform (Pim-1, Pim-2, and Pim-3) have been observed in various types of human cancers, including gastric cancer. AZD1208 is a potent and selective inhibitor that affects all three isoforms of Pim. We investigated the effects of AZD1208 as a single agent and in combination with an Akt inhibitor in gastric cancer cells.

Materials and Methods

The antitumor activity of AZD1208 with/without an Akt inhibitor was evaluated in a large panel of gastric cancer cell lines through growth inhibition assays. The underlying mechanism was also examined by western blotting, immunofluorescence assay, and cell cycle analysis.

Results

AZD1208 treatment decreased gastric cancer cell proliferation rates and induced autophagy only in long-term culture systems. Light chain 3B (LC3B), a marker of autophagy, was increased in sensitive cells in a dose-dependent manner with AZD1208 treatment, which suggested that the growth inhibition effect of AZD1208 was achieved through autophagy, not apoptosis. Moreover, we found that cells damaged by Pim inhibition were repaired by activation of the DNA damage repair pathway, which promoted cell survival and led the cells to become resistant to AZD1208. We also confirmed that the combination of an Akt inhibitor with AZD1208 produced a highly synergistic effect in gastric cancer cell lines.

Conclusion

Treatment with AZD1208 alone induced considerable cell death through autophagy in gastric cancer cells. Moreover, the combination of AZD1208 with an Akt inhibitor showed synergistic antitumor effects through regulation of the DNA damage repair pathway.

PIM-2 protein kinase negatively regulates T cell responses in transplantation and tumor immunity

PIM kinase family members play a crucial role in promoting cell survival and proliferation via phosphorylation of their target substrates. In this study, we investigated the role of the PIM kinases with respect to T cell responses in transplantation and tumor immunity. We found that the PIM-2 isoform negatively regulated T cell responses to alloantigen, in contrast to the PIM-1 and PIM-3 isoforms, which acted as positive regulators. T cells deficient in PIM-2 demonstrated increased T cell differentiation toward Th1 subset, proliferation, and migration to target organs after allogeneic bone marrow transplantation, resulting in dramatically accelerated graft-versus-host disease (GVHD) severity. Restoration of PIM-2 expression markedly attenuated the pathogenicity of PIM-2-deficient T cells to induce GVHD. On the other hand, mice deficient in PIM-2 readily rejected syngeneic tumor, which was primarily dependent on CD8+ T cells. Furthermore, silencing PIM-2 in polyclonal or antigen-specific CD8+ T cells substantially enhanced their antitumor response in adoptive T cell immunotherapy. We conclude that PIM-2 kinase plays a prominent role in suppressing T cell responses, and provide a strong rationale to target PIM-2 for cancer immunotherapy.