The serine/threonine kinase Pim-2 is a transcriptionally regulated apoptotic inhibitor

Regnase-1 D141N mutation induces CD4+ T cell-mediated lung granuloma formation via upregulation of Pim2

Regnase-1 is an RNase that plays a critical role in negatively regulating immune responses by destabilizing inflammatory messenger RNAs (mRNAs). Dysfunction of Regnase-1 can be a major cause of various inflammatory diseases with tissue injury and immune cell infiltration into organs. This study focuses on the role of the RNase activity of Regnase-1 in developing inflammatory diseases. We have constructed mice with a single point mutation at the catalytic center of the Regnase-1 RNase domain, which lacks endonuclease activity. D141N mutant mice demonstrated systemic inflammation, immune cell infiltration into various organs, and progressive development of lung granuloma. CD4+ T cells, mainly affected by this mutation, upregulated the mTORC1 pathway and facilitated the autoimmune trait in the D141N mutation. Moreover, serine/threonine kinase Pim2 contributed to lung inflammation in this mutation. Inhibition of Pim2 kinase activity ameliorated granulomatous inflammation, immune cell infiltration, and proliferation in the lungs. Additionally, Pim2 inhibition reduced the expression of adhesion molecules on CD4+ T cells, suggesting a role for Pim2 in facilitating leukocyte adhesion and migration to inflamed tissues. Our findings provide new insights into the role of Regnase-1 RNase activity in controlling immune functions and underscore the therapeutic relevance of targeting Pim2 to modulate abnormal immune responses.

4-1BB-encoding CAR causes cell death via sequestration of the ubiquitin-modifying enzyme A20

CD28 and 4-1BB costimulatory endodomains included in chimeric antigen receptor (CAR) molecules play a critical role in promoting sustained antitumor activity of CAR-T cells. However, the molecular events associated with the ectopic and constitutive display of either CD28 or 4-1BB in CAR-T cells have been only partially explored. In the current study, we demonstrated that 4-1BB incorporated within the CAR leads to cell cluster formation and cell death in the forms of both apoptosis and necroptosis in the absence of CAR tonic signaling. Mechanistic studies illustrate that 4-1BB sequesters A20 to the cell membrane in a TRAF-dependent manner causing A20 functional deficiency that in turn leads to NF-κB hyperactivity, cell aggregation via ICAM-1 overexpression, and cell death including necroptosis via RIPK1/RIPK3/MLKL pathway. Genetic modulations obtained by either overexpressing A20 or releasing A20 from 4-1BB by deleting the TRAF-binding motifs of 4-1BB rescue cell cluster formation and cell death and enhance the antitumor ability of 4-1BB-costimulated CAR-T cells.

Th2 cell extracellular vesicles promote eosinophil survival through the cytokine cargo IL-3 and prolong airway eosinophilia

Background

Extracellular vesicles (EVs) mediate intercellular communication during immune responses. EVs are abundant in respiratory biofluids, and the composition of EVs in the lung changes during inflammation.

Objective

We aimed to quantify the contribution of T cells to airway EVs in allergic lung inflammation and ascertain their function during a type 2 inflammatory response.

Methods

Genetic membrane tagging was combined with single vesicle flow cytometry to quantify T cell EVs in the airways of mice challenged with ovalbumin or house dust mite. EVs were purified from T helper type 2 (Th2) cell cultures and their functions on eosinophils assessed by flow cytometry and RNA sequencing. Th2 cell EVs were instilled into the lungs of mice to determine effects on lung eosinophilia. Finally, the function of an EV protein cargo was tested using inhibitors and blocking antibodies.

Results

T cell EVs are increased in the airways of mice with induced allergic inflammation. EVs secreted by Th2 cells inhibit apoptosis and induce activating pathways in eosinophils in vitro. This effect depends on re-stimulation through the T cell receptor. Th2 cell EVs prolong eosinophilia in vivo during allergic airway inflammation. Th2 cell EVs carry a potent form of the cytokine IL-3 on their surfaces, which inhibits apoptosis by activating Jak1/2-dependent pro-survival programs in eosinophils.

Conclusion

Th2 cell EVs promote eosinophil survival and prolong eosinophilia during allergic airway inflammation. This function depends on the EV cargo IL-3, supporting a role for EVs as vehicles of cytokine-based communication in lung inflammation.

Key Messages

T cells secrete extracellular vesicles in the airway during allergic lung inflammation.Th2 cell extracellular vesicles inhibit eosinophil apoptosis and prolong airway eosinophilia during allergic lung inflammation.IL-3 carried on Th2 cell EVs is a functional cargo, supporting a role for cytokine-carrying EVs as drivers of type 2 inflammation.

Capsule summary

This study supports that T cell extracellular vesicles may be important drivers of eosinophilic inflammation through the cytokine cargo IL-3, offering new insights into pro-inflammatory signaling in the allergic lung of patients with asthma.

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

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

Cardiac differentiation is modulated by anti-apoptotic signals in murine embryonic stem cells

BACKGROUND

Embryonic stem cells (ESCs) serve as a crucial ex vivo model, representing epiblast cells derived from the inner cell mass of blastocyst-stage embryos. ESCs exhibit a unique combination of self-renewal potency, unlimited proliferation, and pluripotency. The latter is evident by the ability of the isolated cells to differentiate spontaneously into multiple cell lineages, representing the three primary embryonic germ layers. Multiple regulatory networks guide ESCs, directing their self-renewal and lineage-specific differentiation. Apoptosis, or programmed cell death, emerges as a key event involved in sculpting and forming various organs and structures ensuring proper embryonic development. However, the molecular mechanisms underlying the dynamic interplay between differentiation and apoptosis remain poorly understood.

AIM

To investigate the regulatory impact of apoptosis on the early differentiation of ESCs into cardiac cells, using mouse ESC (mESC) models - mESC-B-cell lymphoma 2 (BCL-2), mESC-PIM-2, and mESC-metallothionein-1 (MET-1) - which overexpress the anti-apoptotic genes Bcl-2, Pim-2, and Met-1, respectively.

METHODS

mESC-T2 (wild-type), mESC-BCL-2, mESC-PIM-2, and mESC-MET-1 have been used to assess the effect of potentiated apoptotic signals on cardiac differentiation. The hanging drop method was adopted to generate embryoid bodies (EBs) and induce terminal differentiation of mESCs. The size of the generated EBs was measured in each condition compared to the wild type. At the functional level, the percentage of cardiac differentiation was measured by calculating the number of beating cardiomyocytes in the manipulated mESCs compared to the control. At the molecular level, quantitative reverse transcription-polymerase chain reaction was used to assess the mRNA expression of three cardiac markers: Troponin T, GATA4, and NKX2.5. Additionally, troponin T protein expression was evaluated through immunofluorescence and western blot assays.

RESULTS

Our findings showed that the upregulation of Bcl-2, Pim-2, and Met-1 genes led to a reduction in the size of the EBs derived from the manipulated mESCs, in comparison with their wild-type counterpart. Additionally, a decrease in the count of beating cardiomyocytes among differentiated cells was observed. Furthermore, the mRNA expression of three cardiac markers - troponin T, GATA4, and NKX2.5 - was diminished in mESCs overexpressing the three anti-apoptotic genes compared to the control cell line. Moreover, the overexpression of the anti-apoptotic genes resulted in a reduction in troponin T protein expression.

CONCLUSION

Our findings revealed that the upregulation of Bcl-2, Pim-2, and Met-1 genes altered cardiac differentiation, providing insight into the intricate interplay between apoptosis and ESC fate determination.

Identification and assessment of new PIM2 inhibitors for treating hematologic cancers: A combined approach of energy-based virtual screening and machine learning evaluation

PIM2, part of the PIM kinase family along with PIM1 and PIM3, is often overexpressed in hematologic cancers, fueling tumor growth. Despite its significance, there are no approved drugs targeting it. In response to this challenge, we devised a thorough virtual screening workflow for discovering novel PIM2 inhibitors. Our process includes molecular docking and diverse scoring methods like molecular mechanics generalized born surface area, XGBOOST, and DeepDock to rank potential inhibitors by binding affinities and interaction potential. Ten compounds were selected and subjected to an adequate evaluation of their biological activity. Compound 2 emerged as the most potent inhibitor with an IC50 of approximately 135.7 nM. It also displayed significant activity against various hematological cancers, including acute myeloid leukemia, mantle cell lymphoma, and anaplastic large cell lymphoma (ALCL). Molecular dynamics simulations elucidated the binding mode of compound 2 with PIM2, offering insights for drug development. These results highlight the reliability and efficacy of our virtual screening workflow, promising new drugs for hematologic cancers, notably ALCL.

S100A8/A9 predicts response to PIM kinase and PD-1/PD-L1 inhibition in triple-negative breast cancer mouse models

BACKGROUND

Understanding why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well remains a challenge. This study aims to understand the potential underlying mechanisms distinguishing early-stage TNBC tumors that respond to clinical intervention from non-responders, as well as to identify clinically viable therapeutic strategies, specifically for TNBC patients who may not benefit from existing therapies.

METHODS

We conducted retrospective bioinformatics analysis of historical gene expression datasets to identify a group of genes whose expression levels in early-stage tumors predict poor clinical outcomes in TNBC. In vitro small-molecule screening, genetic manipulation, and drug treatment in syngeneic mouse models of TNBC were utilized to investigate potential therapeutic strategies and elucidate mechanisms of drug action.

RESULTS

Our bioinformatics analysis reveals a robust association between increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors and subsequent disease progression in TNBC. A targeted small-molecule screen identifies PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Notably, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC.

CONCLUSIONS

Our data propose S100A8/A9 as a potential predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC. This work encourages the development of S100A8/A9-based liquid biopsy tests for treatment guidance.

S100A8/A9 predicts triple-negative breast cancer response to PIM kinase and PD-1/PD-L1 inhibition

It remains elusive why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well. Our retrospective analysis of historical gene expression datasets reveals that increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors is robustly associated with subsequent disease progression in TNBC. Although it has recently gained recognition as a potential anticancer target, S100A8/A9 has not been integrated into clinical study designs evaluating molecularly targeted therapies. Our small molecule screen has identified PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Furthermore, combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Importantly, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC. Thus, our data suggest that S100A8/A9 could be a predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC and encourage the development of S100A8/A9-based liquid biopsy tests.

Metabolic protein kinase signalling in neuroblastoma

BACKGROUND

Neuroblastoma is a paediatric malignancy of incredibly complex aetiology. Oncogenic protein kinase signalling in neuroblastoma has conventionally focussed on transduction through the well-characterised PI3K/Akt and MAPK pathways, in which the latter has been implicated in treatment resistance. The discovery of the receptor tyrosine kinase ALK as a target of genetic alterations in cases of familial and sporadic neuroblastoma, was a breakthrough in the understanding of the complex genetic heterogeneity of neuroblastoma. However, despite progress in the development of small-molecule inhibitors of ALK, treatment resistance frequently arises and appears to be a feature of the disease. Moreover, since the identification of ALK, several additional protein kinases, including the PIM and Aurora kinases, have emerged not only as drivers of the disease phenotype, but also as promising druggable targets. This is particularly the case for Aurora-A, given its intimate engagement with MYCN, a driver oncogene of aggressive neuroblastoma previously considered 'undruggable.'

SCOPE OF REVIEW

Aided by significant advances in structural biology and a broader understanding of the mechanisms of protein kinase function and regulation, we comprehensively outline the role of protein kinase signalling, emphasising ALK, PIM and Aurora in neuroblastoma, their respective metabolic outputs, and broader implications for targeted therapies.

MAJOR CONCLUSIONS

Despite massively divergent regulatory mechanisms, ALK, PIM and Aurora kinases all obtain significant roles in cellular glycolytic and mitochondrial metabolism and neuroblastoma progression, and in several instances are implicated in treatment resistance. While metabolism of neuroblastoma tends to display hallmarks of the glycolytic "Warburg effect," aggressive, in particular MYCN-amplified tumours, retain functional mitochondrial metabolism, allowing for survival and proliferation under nutrient stress. Future strategies employing specific kinase inhibitors as part of the treatment regimen should consider combinatorial attempts at interfering with tumour metabolism, either through metabolic pathway inhibitors, or by dietary means, with a view to abolish metabolic flexibility that endows cancerous cells with a survival advantage.

Pim Kinases: Important Regulators of Cardiovascular Disease

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

Forecasting of potential anti-inflammatory targets of some immunomodulatory plants and their constituents using in vitro, molecular docking and network pharmacology-based analysis

Most synthetic immunomodulatory medications are extremely expensive, have many disadvantages and suffer from a lot of side effects. So that, introducing immunomodulatory reagents from natural sources will have great impact on drug discovery. Therefore, this study aimed to comprehend the mechanism of the immunomodulatory activity of some natural plants via network pharmacology together with molecular docking and in vitro testing. Apigenin, luteolin, diallyl trisulfide, silibinin and allicin had the highest percentage of C-T interactions while, AKT1, CASP3, PTGS2, NOS3, TP53 and MMP9 were found to be the most enriched genes. Moreover, the most enriched pathways were pathways in cancer, fluid shear stress and atherosclerosis, relaxin signaling pathway, IL-17 signaling pathway and FoxO signaling pathway. Additionally, Curcuma longa, Allium sativum, Oleu europea, Salvia officinalis, Glycyrrhiza glabra and Silybum marianum had the highest number of P-C-T-P interactions. Furthermore, molecular docking analysis of the top hit compounds against the most enriched genes revealed that silibinin had the most stabilized interactions with AKT1, CASP3 and TP53, whereas luteolin and apigenin exhibited the most stabilized interactions with AKT1, PTGS2 and TP53. In vitro anti-inflammatory and cytotoxicity testing of the highest scoring plants exhibited equivalent outcomes to those of piroxicam.

RIPK2: a promising target for cancer treatment

As an essential mediator of inflammation and innate immunity, the receptor-interacting serine/threonine-protein kinase-2 (RIPK2) is responsible for transducing signaling downstream of the intracellular peptidoglycan sensors nucleotide oligomerization domain (NOD)-like receptors 1 and 2 (NOD1/2), which will further activate nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways, leading to the transcription activation of pro-inflammatory cytokines and productive inflammatory response. Thus, the NOD2-RIPK2 signaling pathway has attracted extensive attention due to its significant role in numerous autoimmune diseases, making pharmacologic RIPK2 inhibition a promising strategy, but little is known about its role outside the immune system. Recently, RIPK2 has been related to tumorigenesis and malignant progression for which there is an urgent need for targeted therapies. Herein, we would like to evaluate the feasibility of RIPK2 being the anti-tumor drug target and summarize the research progress of RIPK2 inhibitors. More importantly, following the above contents, we will analyze the possibility of applying small molecule RIPK2 inhibitors to anti-tumor therapy.

Final step of B-cell differentiation into plasmablasts; the right time to activate plasma cell PIM2 kinase

The differentiation of B cells into antibody-secreting plasma cells is a complex process that involves extensive changes in morphology, lifespan, and cellular metabolism to support the high rates of antibody production. During the final stage of differentiation, B cells undergo significant expansion of their endoplasmic reticulum and mitochondria, which induces cellular stress and may lead to cell death in absence of effective inhibition of the apoptotic pathway. These changes are tightly regulated at transcriptional and epigenetic levels, as well as at post-translational level, with protein modifications playing a critical role in the process of cellular modification and adaptation. Our recent research has highlighted the pivotal role of the serine/threonine kinase PIM2 in B cell differentiation, from commitment stage to plasmablast and maintenance of expression in mature plasma cells. PIM2 has been shown to promote cell cycle progression during the final stage of differentiation and to inhibit Caspase 3 activation, raising the threshold for apoptosis. In this review, we examine the key molecular mechanisms controlled by PIM2 that contribute to plasma cell development and maintenance.

An XBP1s-PIM-2 positive feedback loop controls IL-15-mediated survival of natural killer cells

Spliced X-box-binding protein 1 (XBP1s) is an essential transcription factor downstream of interleukin-15 (IL-15) and AKT signaling, which controls cell survival and effector functions of human natural killer (NK) cells. However, the precise mechanisms, especially the downstream targets of XBP1s, remain unknown. In this study, by using XBP1 conditional knockout mice, we found that XBP1s is critical for IL-15-mediated NK cell survival but not proliferation in vitro and in vivo. Mechanistically, XBP1s regulates homeostatic NK cell survival by targeting PIM-2, a critical anti-apoptotic gene, which in turn stabilizes XBP1s protein by phosphorylating it at Thr⁵⁸. In addition, XBP1s enhances the effector functions and antitumor immunity of NK cells by recruiting T-bet to the promoter region of Ifng. Collectively, our findings identify a previously unknown mechanism by which IL-15-XBP1s signaling regulates the survival and effector functions of NK cells.

When Just One Phosphate Is One Too Many: The Multifaceted Interplay between Myc and Kinases

Myc transcription factors are key regulators of many cellular processes, with Myc target genes crucially implicated in the management of cell proliferation and stem pluripotency, energy metabolism, protein synthesis, angiogenesis, DNA damage response, and apoptosis. Given the wide involvement of Myc in cellular dynamics, it is not surprising that its overexpression is frequently associated with cancer. Noteworthy, in cancer cells where high Myc levels are maintained, the overexpression of Myc-associated kinases is often observed and required to foster tumour cells' proliferation. A mutual interplay exists between Myc and kinases: the latter, which are Myc transcriptional targets, phosphorylate Myc, allowing its transcriptional activity, highlighting a clear regulatory loop. At the protein level, Myc activity and turnover is also tightly regulated by kinases, with a finely tuned balance between translation and rapid protein degradation. In this perspective, we focus on the cross-regulation of Myc and its associated protein kinases underlying similar and redundant mechanisms of regulation at different levels, from transcriptional to post-translational events. Furthermore, a review of the indirect effects of known kinase inhibitors on Myc provides an opportunity to identify alternative and combined therapeutic approaches for cancer treatment.

Oncogenic PKA signaling increases c-MYC protein expression through multiple targetable mechanisms

Genetic alterations that activate protein kinase A (PKA) are found in many tumor types. Yet, their downstream oncogenic signaling mechanisms are poorly understood. We used global phosphoproteomics and kinase activity profiling to map conserved signaling outputs driven by a range of genetic changes that activate PKA in human cancer. Two signaling networks were identified downstream of PKA: RAS/MAPK components and an Aurora Kinase A (AURKA)/glycogen synthase kinase (GSK3) sub-network with activity toward MYC oncoproteins. Findings were validated in two PKA-dependent cancer models: a novel, patient-derived fibrolamellar carcinoma (FLC) line that expresses a DNAJ-PKAc fusion and a PKA-addicted melanoma model with a mutant type I PKA regulatory subunit. We identify PKA signals that can influence both de novo translation and stability of the proto-oncogene c-MYC. However, the primary mechanism of PKA effects on MYC in our cell models was translation and could be blocked with the eIF4A inhibitor zotatifin. This compound dramatically reduced c-MYC expression and inhibited FLC cell line growth in vitro. Thus, targeting PKA effects on translation is a potential treatment strategy for FLC and other PKA-driven cancers.

MYC and therapy resistance in cancer: risks and opportunities

The MYC transcription factor, encoded by the c-MYC proto-oncogene, is activated by growth-promoting signals, and is a key regulator of biosynthetic and metabolic pathways driving cell growth and proliferation. These same processes are deregulated in MYC-driven tumors, where they become critical for cancer cell proliferation and survival. As other oncogenic insults, overexpressed MYC induces a series of cellular stresses (metabolic, oxidative, replicative, etc.) collectively known as oncogenic stress, which impact not only on tumor progression, but also on the response to therapy, with profound, multifaceted consequences on clinical outcome. On one hand, recent evidence uncovered a widespread role for MYC in therapy resistance in multiple cancer types, with either standard chemotherapeutic or targeted regimens. Reciprocally, oncogenic MYC imparts a series of molecular and metabolic dependencies to cells, thus giving rise to cancer-specific vulnerabilities that may be exploited to obtain synthetic-lethal interactions with novel anticancer drugs. Here we will review the current knowledge on the links between MYC and therapeutic responses, and will discuss possible strategies to overcome resistance through new, targeted interventions.

Targeting PIM2 by JP11646 results in significant antitumor effects in solid tumors

Proviral integration of Moloney virus 2 (PIM2) is a pro-survival factor of cancer cells and a possible therapeutic target in hematological malignancies. However, the attempts at inhibiting PIM2 have yielded underwhelming results in early clinical trials on hematological malignancies. Recently, a novel pan-PIM inhibitor, JP11646, was developed. The present study examined the utility of targeting PIM2 in multiple solid cancers and investigated the antitumor efficacy and the mechanisms of action of JP11646. When PIM2 expression was compared between normal and cancer tissues in publicly available datasets, PIM2 was found to be overexpressed in several types of solid cancers. PIM2 ectopic overexpression promoted tumor growth in in vivo xenograft breast cancer mouse models. The pan-PIM inhibitor, JP11646, suppressed in vitro cancer cell proliferation in a concentration-dependent manner in multiple types of cancers; a similar result was observed with siRNA-mediated PIM2 knockdown, as well as an increased in cell apoptosis. By contrast, another pan-PIM inhibitor, AZD1208, suppressed the expression of downstream PIM2 targets, but not PIM2 protein expression, corresponding to no apoptosis induction. As a mechanism of PIM2 protein degradation, it was found that the proteasome inhibitor, bortezomib, reversed the apoptosis induced by JP11646, suggesting that PIM2 degradation by JP11646 is proteasome-dependent. JP11646 exhibited significant anticancer efficacy with minimal toxicities at the examined doses and schedules in multiple in vivo mice xenograft solid cancer models. On the whole, the present study demonstrates that PIM2 promotes cancer progression in solid tumors. JP11646 induces apoptosis at least partly by PIM2 protein degradation and suppresses cancer cell proliferation in vitro and in vivo. JP11646 may thus be a possible treatment strategy for multiple types of solid cancers.

The Role of PIM Kinases in Pediatric Solid Tumors

PIM kinases have been identified as potential therapeutic targets in several malignancies. Here, we provide an in-depth review of PIM kinases, including their structure, expression, activity, regulation, and role in pediatric carcinogenesis. Also included is a brief summary of the currently available pharmaceutical agents targeting PIM kinases and existing clinical trials.

Distinct resistance mechanisms arise to allosteric vs. ATP-competitive AKT inhibitors

The AKT kinases have emerged as promising therapeutic targets in oncology and both allosteric and ATP-competitive AKT inhibitors have entered clinical investigation. However, long-term efficacy of such inhibitors will likely be challenged by the development of resistance. We have established prostate cancer models of acquired resistance to the allosteric inhibitor MK-2206 or the ATP-competitive inhibitor ipatasertib following prolonged exposure. While alterations in AKT are associated with acquired resistance to MK-2206, ipatasertib resistance is driven by rewired compensatory activity of parallel signaling pathways. Importantly, MK-2206 resistance can be overcome by treatment with ipatasertib, while ipatasertib resistance can be reversed by co-treatment with inhibitors of pathways including PIM signaling. These findings demonstrate that distinct resistance mechanisms arise to the two classes of AKT inhibitors and that combination approaches may reverse resistance to ATP-competitive inhibition.

How resistance to different classes of AKT inhibitors can emerge is unclear. Here, the authors show that resistance to allosteric inhibitors is mainly due to mutation of AKT1 while the ATP competitive resistance is driven by activation of PIM kinases in prostate cancer models.

Proviral Integration of Moloney Virus-2 (PIM-2) Expression Level as a Prognostic Marker in Patients with Acute Myeloid Leukemia

Purpose

This study aimed to assess PIM-2 gene expression level as a prognostic marker in AML patients and to correlate the results with their clinical outcome.

Patients and Methods

This study was conducted on 50 de novo younger AML patients (median age 44). Quantitative real-time polymerase chain reaction (QRT-PCR) was used to assess the expression level of the PIM-2 gene. The transcription level of the target gene (PIM-2) was normalized to that of the reference gene (GAPDH). Twenty control samples were withdrawn from 20 age- and sex-matched individuals for the analysis of the results using the 2^−ΔΔCT method. On day 28 following induction chemotherapy, patients’ bone marrow (BM) was examined for evaluation of their remission status.

Results

PIM-2 gene expression was higher among AML patients who did not achieve complete remission (CR); also, it was higher in patients in the intermediate and poor cytogenetic risk groups. A significant positive correlation was found between PIM-2 level and BM blasts on day 28. In AML patients, PIM-2 has been discovered to be an independent predictive factor for achieving CR following standard induction treatment. Receiver operating characteristic curve (ROC) and area under the curve (AUC) were performed for PIM-2 level at diagnosis to evaluate its role in achieving remission after induction. It was found that PIM-2 at cutoff ≤1.6 had an AUC (0.903) with a sensitivity (90.48%) and specificity (86.21%), P <0.001.

Conclusion

Overexpression of the PIM-2 gene is associated with induction failure and low CR.

Effects of berberine on leukemia with a focus on its molecular targets

Leukemia is a common cancer among both women and men worldwide. Besides the fact that finding new treatment methods may enhance the life quality of patients, there are several problems that we face today in treating leukemia patients, such as drugs side effects and acquired resistance to chemotherapeutic drugs. Berberine is a bioactive alkaloid found in herbal plants (e.g. Rhizoma coptidis and Cortex phellodendri) and exerts several beneficial functions, including anti-tumor activities. Furthermore, berberine exerts antiproliferative and anti-inflammatory effects. Up to now, some studies have investigated the roles of berberine in different types of leukemia, including acute myeloid leukemia and chronic lymphocytic leukemia. In this review, a detailed description of berberine roles in leukemia is provided. We discuss how berberine involves different molecular targets (e.g. interleukins and cyclins) and signaling pathways (e.g. mTOR and PI3K) to exert its anti-tumor functions and how berberine is effective in leukemia treatment when combined with other therapeutic drugs.

Synergistic PIM kinase and proteasome inhibition as a therapeutic strategy for MYC-overexpressing triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the breast cancer subtype with the poorest clinical outcome. The PIM family of kinases has emerged as a factor that is both overexpressed in TNBC and associated with poor outcomes. Preclinical data suggest that TNBC with an elevated MYC expression is sensitive to PIM inhibition. However, clinical observations indicate that the efficacy of PIM inhibitors as single agents may be limited, suggesting the need for combination therapies. Our screening effort identifies PIM and the 20S proteasome inhibition as the most synergistic combination. PIM inhibitors, when combined with proteasome inhibitors, induce significant antitumor effects, including abnormal accumulation of poly-ubiquitinated proteins, increased proteotoxic stress, and the inability of NRF1 to counter loss in proteasome activity. Thus, the identified combination could represent a rational combination therapy against MYC-overexpressing TNBC that is readily translatable to clinical investigations.

Pivotal role of PIM2 kinase in plasmablast generation and plasma cell survival, opening new treatment options in myeloma

The differentiation of B cells into plasmablasts (PBs) and then plasma cells (PCs) is associated with extensive cell reprogramming and new cell functions. By using specific inhibition strategies (including a novel morpholino RNA antisense approach), we found that early, sustained upregulation of the proviral integrations of Moloney virus 2 (PIM2) kinase is a pivotal event during human B cell in vitro differentiation and then continues in mature normal and malignant PCs in the bone marrow. In particular, PIM2 sustained the G1/S transition by acting on CDC25A and p27Kip1 and hindering caspase 3-driven apoptosis through BAD phosphorylation and cytoplasmic stabilization of p21Cip1. In PCs, interleukin-6 triggered PIM2 expression, resulting in anti-apoptotic effects on which malignant PCs were particularly dependent. In multiple myeloma, pan-PIM and MCL1 inhibitors displayed synergistic activity. Our results highlight a cell-autonomous function that links kinase activity to the PBs' newly acquired secretion ability and the adaptability observed in both normal and malignant PCs, and finally should prompt the reconsideration of PIM2 as a therapeutic target in multiple myeloma.

Engineered Fully Human Single-Chain Monoclonal Antibodies to PIM2 Kinase

Proviral integration site of Moloney virus-2 (PIM2) is overexpressed in multiple human cancer cells and high level is related to poor prognosis; thus, PIM2 kinase is a rational target of anti-cancer therapeutics. Several chemical inhibitors targeting PIMs/PIM2 or their downstream signaling molecules have been developed for treatment of different cancers. However, their off-target toxicity is common in clinical trials, so they could not be advanced to official approval for clinical application. Here, we produced human single-chain antibody fragments (HuscFvs) to PIM2 by using phage display library, which was constructed in a way that a portion of phages in the library carried HuscFvs against human own proteins on their surface with the respective antibody genes in the phage genome. Bacterial derived-recombinant PIM2 (rPIM2) was used as an antigenic bait to fish out the rPIM2-bound phages from the library. Three E. coli clones transfected with the HuscFv genes derived from the rPIM2-bound phages expressed HuscFvs that bound also to native PIM2 from cancer cells. The HuscFvs presumptively interact with the PIM2 at the ATP binding pocket and kinase active loop. They were as effective as small chemical drug inhibitor (AZD1208, which is an ATP competitive inhibitor of all PIM isoforms for ex vivo use) in inhibiting PIM kinase activity. The HuscFvs should be engineered into a cell-penetrating format and tested further towards clinical application as a novel and safe pan-anti-cancer therapeutics.

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

BACKGROUND

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

SCOPE OF REVIEW

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

MAJOR CONCLUSIONS

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

GENERAL SIGNIFICANCE

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

Multifaceted control of mRNA translation machinery in cancer

The mRNA translation machinery is tightly regulated through several, at times overlapping, mechanisms that modulate its efficiency and accuracy. Due to their fast rate of growth and metabolism, cancer cells require an excessive amount of mRNA translation and protein synthesis. However, unfavorable conditions, such as hypoxia, amino acid starvation, and oxidative stress, which are abundant in cancer, as well as many anti-cancer treatments inhibit mRNA translation. Cancer cells adapt to the various internal and environmental stresses by employing specialised transcript-specific translation to survive and gain a proliferative advantage. We will highlight the major signaling pathways and mechanisms of translation that regulate the global or mRNA-specific translation in response to the intra- or extra-cellular signals and stresses that are key components in the process of tumourigenesis.

Novel Pan-Pim Kinase Inhibitors With Imidazopyridazine and Thiazolidinedione Structure Exert Potent Antitumor Activities

Pim kinases are overexpressed in various types of hematological malignancies and solid carcinomas, and promote cell proliferation and survival. Here in this study, we investigated the preclinical profile of novel pan-Pim kinase inhibitors with imidazopyridazine and thiazolidinedione structure. Imidazopyridazine-thiazolidinediones inhibited activities of Pim kinases with IC₅₀ values of tens to hundreds nanomolar. With YPC-21440 and/or YPC-21817, which exhibited especially high inhibitory activities against Pim kinases, we investigated in vitro and in vivo activities of imidazopyridazine-thiazolidinediones. In silico analysis of binding mode of YPC-21440 and Pim kinases revealed that it directly bound to ATP-binding pockets of Pim kinases. In the kinase panel tested, YPC-21440 and YPC-21817 were highly specific to Pim kinases. These compounds exerted antiproliferative activities against various cancer cell lines derived from hematological malignancies and solid carcinomas. Furthermore, they suppressed phosphorylation of Pim kinase substrates, arrested cell cycle at the G1 phase, and induced apoptosis in cultured cancer cells. In tumor xenograft models, YPC-21440 methanesulfonate and YPC-21817 methanesulfonate exerted antitumor activities. Furthermore, pharmacodynamic analysis with a xenograft model suggested that YPC-21817 methanesulfonate inhibited Pim kinases in tumors. In conclusion, our data revealed that imidazopyridazine-thiazolidinediones are novel Pim kinases inhibitors, effective on various types of cancer cell lines both in vitro and in vivo.

Emerging Roles for AKT Isoform Preference in Cancer Progression Pathways

The phosphoinositol-3 kinase (PI3K)-AKT pathway is one of the most mutated in human cancers, predominantly associated with the loss of the signaling antagonist, PTEN, and to lesser extents, with gain-of-function mutations in PIK3CA (encoding PI3K-p110α) and AKT1. In addition, most oncogenic driver pathways activate PI3K/AKT signaling. Nonetheless, drugs targeting PI3K or AKT have fared poorly against solid tumors in clinical trials as monotherapies, yet some have shown efficacy when combined with inhibitors of other oncogenic drivers, such as receptor tyrosine kinases or nuclear hormone receptors. There is growing evidence that AKT isoforms, AKT1, AKT2, and AKT3, have different, often distinct roles in either promoting or suppressing specific parameters of oncogenic progression, yet few if any isoform-preferred substrates have been characterized. This review will describe recent data showing that the differential activation of AKT isoforms is mediated by complex interplays between PTEN, PI3K isoforms and upstream tyrosine kinases, and that the efficacy of PI3K/AKT inhibitors will likely depend on the successful targeting of specific AKT isoforms and their preferred pathways.

Co-Targeting PIM Kinase and PI3K/mTOR in NSCLC

Simple Summary

PIM kinases interact with major oncogenic players, including the PI3K/Akt pathway, and provide an escape mechanism leading to drug resistance. This study examined PIM kinase expression in NSCLC and the potential of PIM1 as a prognostic marker. The effect on cell signaling of novel preclinical PI3K/mTOR/PIM kinase inhibitor IBL-301 was compared to PI3K/mTOR inhibition in vitro and ex vivo. PI3K-mTOR inhibitor sensitive (H1975P) and resistant (H1975GR) cells were compared for altered IL6/STAT3 pathway expression and sensitivity to IBL-301. All three PIM kinases are expressed in NSCLC and PIM1 is a marker of poor prognosis. IBL-301 inhibited c-Myc, the PI3K-Akt and JAK/STAT pathways in vitro and in NSCLC tumor tissue explants. IBL-301 also inhibited secreted pro-inflammatory cytokine MCP-1. PIM kinases were activated in H1975GR cells which were more sensitive to IBL-301 than H1975P cells. A miRNA signature of PI3K-mTOR resistance was validated. Co-targeting PIM kinase and PI3K-mTOR warrants further clinical investigation.

Abstract

PIM kinases are constitutively active proto-oncogenic serine/threonine kinases that play a role in cell cycle progression, metabolism, inflammation and drug resistance. PIM kinases interact with and stabilize p53, c-Myc and parallel signaling pathway PI3K/Akt. This study evaluated PIM kinase expression in NSCLC and in response to PI3K/mTOR inhibition. It investigated a novel preclinical PI3K/mTOR/PIM inhibitor (IBL-301) in vitro and in patient-derived NSCLC tumor tissues. Western blot analysis confirmed PIM1, PIM2 and PIM3 are expressed in NSCLC cell lines and PIM1 is a marker of poor prognosis in patients with NSCLC. IBL-301 decreased PIM1, c-Myc, pBAD and p4EBP1 (Thr37/46) and peIF4B (S406) protein levels in-vitro and MAP kinase, PI3K-Akt and JAK/STAT pathways in tumor tissue explants. IBL-301 significantly decreased secreted pro-inflammatory cytokine MCP-1. Altered mRNA expression, including activated PIM kinase and c-Myc, was identified in Apitolisib resistant cells (H1975GR) by an IL-6/STAT3 pathway array and validated by Western blot. H1975GR cells were more sensitive to IBL-301 than parent cells. A miRNA array identified a dysregulated miRNA signature of PI3K/mTOR drug resistance consisting of regulators of PIM kinase and c-Myc (miR17-5p, miR19b-3p, miR20a-5p, miR15b-5p, miR203a, miR-206). Our data provides a rationale for co-targeting PIM kinase and PI3K-mTOR to improve therapeutic response in NSCLC.

Protein kinase PIM2: A simple PIM family kinase with complex functions in cancer metabolism and therapeutics

PIM2 (proviral integration site for Moloney murine leukemia virus 2) kinase plays an important role as an oncogene in multiple cancers, such as leukemia, liver, lung, myeloma, prostate and breast cancers. PIM2 is largely expressed in both leukemia and solid tumors, and it promotes the transcriptional activation of genes involved in cell survival, cell proliferation, and cell-cycle progression. Many tumorigenic signaling molecules have been identified as substrates for PIM2 kinase, and a variety of inhibitors have been developed for its kinase activity, including SMI-4a, SMI-16a, SGI-1776, JP11646 and DHPCC-9. Here, we summarize the signaling pathways involved in PIM2 kinase regulation and PIM2 mechanisms in various neoplastic diseases. We also discuss the current status and future perspectives for the development of PIM2 kinase inhibitors to combat human cancer, and PIM2 will become a therapeutic target in cancers in the future.

In Vitro Investigation of the Cytotoxic Activity of Emodin 35 Derivative on Multiple Myeloma Cell Lines

Background

Bortezomib is used for treating multiple myeloma (MM); however, it has considerable adverse effects. Emodin has been reported to exhibit inhibitory effects on MM cell lines. We investigated the efficacy of emodin 35 (E35), an emodin derivative, using U266 and MM1s cell lines in treating MM and the efficacy of combining bortezomib and E35.

Methods

MTT assays were used to observe the effects of E35 on MM cell growth. The effects on cellular apoptosis were then observed using Annexin V/propidium iodide (PI) staining assay. The expression of apoptosis-related genes, including the caspase family, was examined. The efficacy of combining bortezomib and E35 was investigated by examining the expression of the Akt/mTOR/4EBP1 signaling pathway-related proteins.

Results

We report that E35 inhibited the growth of U266 and MM1s cells by inducing cellular apoptosis. Moreover, E35 downregulated the expression of apoptosis-related genes and suppressed the phosphorylation of Akt/mTOR/4EBP1 signaling pathway-related genes, thus exhibiting synergistic effects with bortezomib. All observed effects were dose-dependent.

Conclusion

The results showed that E35 exhibited cytotoxic effects in MM cell lines in protein levels. Thus, E35, particularly in combination with bortezomib, may be considered as a promising treatment for MM; however, this requires further investigation in vivo.

Carbazole Derivatives as Kinase-Targeting Inhibitors for Cancer Treatment

Protein Kinases (PKs) are a heterogeneous family of enzymes that modulate several biological pathways, including cell division, cytoskeletal rearrangement, differentiation and apoptosis. In particular, due to their crucial role during human tumorigenesis and cancer progression, PKs are ideal targets for the design and development of effective and low toxic chemotherapeutics and represent the second group of drug targets after G-protein-coupled receptors. Nowadays, several compounds have been claimed to be PKs inhibitors, and some of them, such as imatinib, erlotinib and gefitinib, have already been approved for clinical use, whereas more than 30 others are in various phases of clinical trials. Among them, some natural or synthetic carbazole-based molecules represent promising PKs inhibitors due to their capability to interfere with PK activity by different mechanisms of action including the ability to act as DNA intercalating agents, interfere with the activity of enzymes involved in DNA duplication, such as topoisomerases and telomerases, and inhibit other proteins such as cyclindependent kinases or antagonize estrogen receptors. Thus, carbazoles can be considered a promising this class of compounds to be adopted in targeted therapy of different types of cancer.

Targeting PIM Kinases to Overcome Therapeutic Resistance in Cancer

Cancer progression and the onset of therapeutic resistance are often the results of uncontrolled activation of survival kinases. The proviral integration for the Moloney murine leukemia virus (PIM) kinases are oncogenic serine/threonine kinases that regulate tumorigenesis by phosphorylating a wide range of substrates that control cellular metabolism, proliferation, and survival. Because of their broad impact on cellular processes that facilitate progression and metastasis in many cancer types, it has become clear that the activation of PIM kinases is a significant driver of resistance to various types of anticancer therapies. As a result, efforts to target PIM kinases for anticancer therapy have intensified in recent years. Clinical and preclinical studies indicate that pharmacologic inhibition of PIM has the potential to significantly improve the efficacy of standard and targeted therapies. This review focuses on the signaling pathways through which PIM kinases promote cancer progression and resistance to therapy, as well as highlights biological contexts and promising strategies to exploit PIM as a therapeutic target in cancer.

PIM2 promotes hepatocellular carcinoma tumorigenesis and progression through activating NF-κB signaling pathway

Inflammatory factors and activation of oncogenes both played critical roles in the development and progression of human hepatocellular carcinoma (HCC). However, the interplay between these two has not been well studied. In this study, we found that regulated by TNFα, Pim-2 proto-oncogene, serine/threonine kinase (PIM2) was highly expressed in HCC and correlated with poor prognosis (P = 0.007) as well as tumor recurrence (P = 0.014). Functional studies showed that PIM2 could enhance abilities of cell proliferation, cell motility, angiogenesis, chemo-resistance, and in vivo tumorigenicity and HCC metastasis. Mechanistic studies revealed that PIM2 could activate NF-κB signaling pathway through upregulating phosphorylation level of RIPK2. Interestingly, TNFα treatment could induce the expression of PIM2, and overexpression of PIM2 could in turn upregulate the expression of TNFα in HCC cells. More importantly, we found the expression level of PIM2 increased with the progression of liver cirrhosis, and PIM kinase inhibitor AZD1208 treatment could effectively attenuate HCC cells’ tumorigenic ability both in vitro and in vivo. Collectively, our study revealed the interaction between an inflammatory factor and a proto-oncogene that contributed to tumorigenesis and progression of HCC, and PIM kinase inhibition may serve as a therapeutic target in the treatment of HCC.

Small molecule H89 renders the phosphorylation of S6K1 and AKT resistant to mTOR inhibitors

The mammalian target of rapamycin (mTOR) is an evolutionarily conserved Ser/Thr kinase that comprises two complexes, termed mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). mTORC1 phosphorylates S6K1 at Thr 389, whereas mTORC2 phosphorylates AKT at Ser 473 to promote cell growth. As the mTOR name implies it is the target of natural product called rapamycin, a clinically approved drug used to treat human disease. Short-term rapamycin treatment inhibits the kinase activity of mTORC1 but not mTORC2. However, the ATP-competitive catalytic mTOR inhibitor Torin1 was identified to inhibit the kinase activity of both mTORC1 and mTORC2. Here, we report that H89 (N-(2-(4-bromocinnamylamino) ethyl)-5-isoquinolinesulfonamide), a well-characterized ATP-mimetic kinase inhibitor, renders the phosphorylation of S6K1 and AKT resistant to mTOR inhibitors across multiple cell lines. Moreover, H89 prevented the dephosphorylation of AKT and S6K1 under nutrient depleted conditions. PKA and other known H89-targeted kinases do not alter the phosphorylation status of S6K1 and AKT. Pharmacological inhibition of some phosphatases also enhanced S6K1 and AKT phosphorylation. These findings suggest a new target for H89 by which it sustains the phosphorylation status of S6K1 and AKT, resulting in mTOR signaling.

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.

Functional interplay between NF-κB-inducing kinase and c-Abl kinases limits response to Aurora inhibitors in multiple myeloma

Considering that Aurora kinase inhibitors are currently under clinical investigation in hematologic cancers, the identification of molecular events that limit the response to such agents is essential for enhancing clinical outcomes. Here, we discover a NF-κB-inducing kinase (NIK)-c-Abl-STAT3 signaling-centered feedback loop that restrains the efficacy of Aurora inhibitors in multiple myeloma. Mechanistically, we demonstrate that Aurora inhibition promotes NIK protein stabilization via downregulation of its negative regulator TRAF2. Accumulated NIK converts c-Abl tyrosine kinase from a nuclear proapoptotic into a cytoplasmic antiapoptotic effector by inducing its phosphorylation at Thr735, Tyr245 and Tyr412 residues, and, by entering into a trimeric complex formation with c-Abl and STAT3, increases both the transcriptional activity of STAT3 and expression of the antiapoptotic STAT3 target genes PIM1 and PIM2. This consequently promotes cell survival and limits the response to Aurora inhibition. The functional disruption of any of the components of the trimer NIK-c-Abl-STAT3 or the PIM survival kinases consistently enhances the responsiveness of myeloma cells to Aurora inhibitors. Importantly, concurrent inhibition of NIK or c-Abl disrupts Aurora inhibitor-induced feedback activation of STAT3 and sensitizes myeloma cells to Aurora inhibitors, implicating a combined inhibition of Aurora and NIK or c-Abl kinases as potential therapies for multiple myeloma. Accordingly, pharmacological inhibition of c-Abl together with Aurora resulted in substantial cell death and tumor regression in vivo The findings reveal an important functional interaction between NIK, Abl and Aurora kinases, and identify the NIK, c-Abl and PIM survival kinases as potential pharmacological targets for improving the efficacy of Aurora inhibitors in myeloma.

The pan-PIM inhibitor INCB053914 displays potent synergy in combination with ruxolitinib in models of MPN

Aberrant JAK2 tyrosine kinase signaling drives the development of Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. However, JAK2 kinase inhibitors have failed to significantly reduce allele burden in MPN patients, underscoring the need for improved therapeutic strategies. Members of the PIM family of serine/threonine kinases promote cellular proliferation by regulating a variety of cellular processes, including protein synthesis and the balance of signaling that regulates apoptosis. Overexpression of PIM family members is oncogenic, exemplified by their ability to induce lymphomas in collaboration with c-Myc. Thus, PIM kinases are potential therapeutic targets for several malignancies such as solid tumors and blood cancers. We and others have shown that PIM inhibitors augment the efficacy of JAK2 inhibitors by using in vitro models of MPNs. Here we report that the recently developed pan-PIM inhibitor INCB053914 augments the efficacy of the US Food and Drug Administration-approved JAK1/2 inhibitor ruxolitinib in both in vitro and in vivo MPN models. INCB053914 synergizes with ruxolitinib to inhibit cell growth in JAK2-driven MPN models and induce apoptosis. Significantly, low nanomolar INCB053914 enhances the efficacy of ruxolitinib to inhibit the neoplastic growth of primary MPN patient cells, and INCB053914 antagonizes ruxolitinib persistent myeloproliferation in vivo. These findings support the notion that INCB053914, which is currently in clinical trials in patients with advanced hematologic malignancies, in combination with ruxolitinib may be effective in MPN patients, and they support the clinical testing of this combination in MPN patients.

TRAF3 regulates the oncogenic proteins Pim2 and c-Myc to restrain survival in normal and malignant B cells

TRAF3 is a versatile intracellular adapter protein with multiple context-specific roles. Uniquely in B cells, TRAF3 deficiency enhances survival and increases the risk of transformation, as loss of TRAF3 is observed in several types of B cell cancers. Here, we report a new mechanism for TRAF3 in the restraint of B cell survival. We found that TRAF3 deficiency was associated with induction of the pro-survival kinase Pim2 in mouse primary B cells and human malignant B cell lines. The increase in Pim2 was independent of NF-κB2 activation but was ameliorated with inhibition of STAT3 expression or function. TRAF3 deficiency also led to a Pim2-dependent increase in c-Myc protein levels and was associated with reduced c-Myc ubiquitination. TRAF3-deficient primary B cells were less sensitive to cell death induced by the Pim inhibitors SGI-1776 and TP-3654. Interestingly, human malignant B cell lines with low expression of TRAF3 were more sensitive to Pim inhibition-induced cell death. Combination treatment of TRAF3-deficient B cells and B cell tumor lines with c-Myc inhibitors enhanced their sensitivity to Pim inhibition, suggesting a possible therapeutic strategy. TRAF3 thus suppresses a Pim2-mediated B cell survival axis, which can be a potential target for treatment of B cell malignancies.

The first-in-human study of the pan-PIM kinase inhibitor PIM447 in patients with relapsed and/or refractory multiple myeloma

PIM447, a novel pan-PIM inhibitor, has shown preclinical activity in multiple myeloma (MM). In the multicenter, open-label, first-in-human study, patients with relapsed and/or refractory MM were enrolled to determine the maximum-tolerated dose (MTD) or recommended dose (RD), safety, pharmacokinetics, and preliminary anti-myeloma activity of PIM447. PIM447 was administered in escalating oral doses of 70-700 mg once daily (q.d.) for 28-day continuous cycles. Seventy-nine patients with a median of four prior therapies were enrolled. Seventy-seven patients (97.5%) had an adverse event (AE) suspected as treatment related, with treatment-related grade 3/4 AEs being mostly hematologic. Eleven dose-limiting toxicities occurred, and an MTD of 500 mg q.d. and an RD of 300 mg q.d. were established. The main reason for discontinuation was disease progression in 54 patients (68.4%). In the entire study population, a disease control rate of 72.2%, a clinical benefit rate of 25.3%, and an overall response rate of 8.9% were observed per modified International Myeloma Working Group criteria. Median progression-free survival at the RD was 10.9 months. PIM447 was well tolerated and demonstrated single-agent antitumor activity in relapsed/refractory MM patients, providing proof of principle for Pim (Proviral Insertions of Moloney Murine leukemia virus) kinase inhibition as a novel therapeutic approach in MM.

At the intersection of DNA damage and immune responses

DNA damage occurs on exposure to genotoxic agents and during physiological DNA transactions. DNA double-strand breaks (DSBs) are particularly dangerous lesions that activate DNA damage response (DDR) kinases, leading to initiation of a canonical DDR (cDDR). This response includes activation of cell cycle checkpoints and engagement of pathways that repair the DNA DSBs to maintain genomic integrity. In adaptive immune cells, programmed DNA DSBs are generated at precise genomic locations during the assembly and diversification of lymphocyte antigen receptor genes. In innate immune cells, the production of genotoxic agents, such as reactive nitrogen molecules, in response to pathogens can also cause genomic DNA DSBs. These DSBs in adaptive and innate immune cells activate the cDDR. However, recent studies have demonstrated that they also activate non-canonical DDRs (ncDDRs) that regulate cell type-specific processes that are important for innate and adaptive immune responses. Here, we review these ncDDRs and discuss how they integrate with other signals during immune system development and function.

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).

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.

Proviral insertion in murine lymphomas 2 promotes stomach cancer progression by regulating apoptosis via reactive oxygen species-triggered endoplasmic reticulum stress

Gastric cancer is one of the most fatal cancers worldwide. The incidence and death rates are still increasing for gastric cancer. Increasing studies have shown that proviral insertion in murine lymphomas 2 (PIM2) functions as critical regulator of multiple cancers. However, it remains unknown whether and how PIM2 regulates gastric cancer progression. In this study, PIM2 was increased in the gastric cancer tissues of patients. Patients with high PIM2 expression levels had significantly shorter survival than those with low PIM2 expression. PIM2 knockdown reduced proliferation, migration and invasion in vitro by up-regulating E-cadherin, and down-regulating N-cadherin and Vimentin. Knockdown of PIM2 induced apoptosis in gastric cancer cells, which was regulated by endoplasmic reticulum (ER) stress, as evidenced by the increased expression levels of Activating transcription factor (ATF) 6, ATF4, X-box- binding protein-1 (XBP-1) and C/EBP homologous protein (CHOP). In addition, our data showed that PIM2 silence induced reactive oxygen species (ROS) production, leading to the activation of c-Jun N-terminal kinase (JNK). Importantly, we found that PIM2 knockdown-induced apoptosis and ER stress could be abolished by reducing reactive oxygen species (ROS) generation. In vivo, PIM2 knockdown showed a significant reduction in SGC-7901 xenograft tumor size. In summary, our findings provided experimental evidence that PIM2 might function as an important oncogene in gastric cancer, which supplied promising target for developing new therapeutic strategy in gastric cancer.

Signaling Pathways Involved in the Regulation of mRNA Translation

Translation is a key step in the regulation of gene expression and one of the most energy-consuming processes in the cell. In response to various stimuli, multiple signaling pathways converge on the translational machinery to regulate its function. To date, the roles of phosphoinositide 3-kinase (PI3K)/AKT and the mitogen-activated protein kinase (MAPK) pathways in the regulation of translation are among the best understood. Both pathways engage the mechanistic target of rapamycin (mTOR) to regulate a variety of components of the translational machinery. While these pathways regulate protein synthesis in homeostasis, their dysregulation results in aberrant translation leading to human diseases, including diabetes, neurological disorders, and cancer. Here we review the roles of the PI3K/AKT and MAPK pathways in the regulation of mRNA translation. We also highlight additional signaling mechanisms that have recently emerged as regulators of the translational apparatus.

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.

Control of translational activation by PIM kinase in activated B-cell diffuse large B-cell lymphoma confers sensitivity to inhibition by PIM447

The PIM family kinases promote growth and survival of tumor cells and are expressed in a wide variety of human cancers. Their potential as therapeutic targets, however, is complicated by overlapping activities with multiple other pathways and remains poorly defined in most clinical scenarios. Here we explore activity of the new pan-PIM inhibitor PIM447 in a variety of lymphoid-derived tumors. We find strong activity in cell lines derived from the activated B-cell subtype of diffuse large B-cell lymphoma (ABC-DLBCL). Sensitive lines show lost activation of the mTORC1 signaling complex and subsequent lost activation of cap-dependent protein translation. In addition, we characterize recurrent PIM1 protein-coding mutations found in DLBCL clinical samples and find most preserve the wild-type protein's ability to protect cells from apoptosis but do not bypass activity of PIM447. Pan-PIM inhibition therefore may have an important role to play in the therapy of selected ABC-DLBCL cases.