Use of regulators and inhibitors of Pim-1, a serine/threonine kinase, for tumour therapy (review)

FDA-approved drugs as PIM-1 kinase inhibitors: A drug repurposed approach for cancer therapy

PIM-1 kinase, a member of the Serine/Threonine kinase family, has emerged as a promising therapeutic target in various cancers due to its role in promoting tumor growth and resistance to conventional therapies. In this study, we employed a structure-based approach to screen 3800 FDA-approved drugs to discover potential inhibitors of PIM-1. After an initial selection of 50 candidates based on high docking scores, four drugs, stanozolol, alfaxalone, rifaximin, and telmisartan, were identified as strong PIM-1 binders, interacting with key residues in the ATP-binding pocket of the kinase. To assess the stability of these interactions, we conducted all-atom molecular dynamic simulations, confirming favorable dynamics. Experimental validation via a kinase inhibition assay on recombinant PIM-1 showed that rifaximin significantly inhibited PIM-1 activity, with an IC50 of ∼26 μM. Fluorescence binding assays further demonstrated a strong binding affinity for rifaximin, with a binding constant, corroborated by isothermal titration calorimetry studies. Our findings suggest that rifaximin may serve as a potential repurposed drug for targeting PIM-1 in cancer treatment. However, further validations are required in a clinical setting before the final therapeutic implications.

3D chromatin architecture, BRD4, and Mediator have distinct roles in regulating genome-wide transcriptional bursting and gene network

Discontinuous transcription is evolutionarily conserved and a fundamental feature of gene regulation; yet, the exact mechanisms underlying transcriptional bursting are unresolved. Analyses of bursting transcriptome-wide have focused on the role of cis-regulatory elements, but other factors that regulate this process remain elusive. We applied mathematical modeling to single-cell RNA sequencing data to infer bursting dynamics transcriptome-wide under multiple conditions to identify possible molecular mechanisms. We found that Mediator complex subunit 26 (MED26) primarily regulates frequency, MYC regulates burst size, while cohesin and Bromodomain-containing protein 4 (BRD4) can modulate both. Despite comparable effects on RNA levels among these perturbations, acute depletion of MED26 had the most profound impact on the entire gene regulatory network, acting downstream of chromatin spatial architecture and without affecting TATA box-binding protein (TBP) recruitment. These results indicate that later steps in the initiation of transcriptional bursts are primary nodes for integrating gene networks in single cells.

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.

PIM Kinase Inhibitors as Novel Promising Therapeutic Scaffolds in Cancer Therapy

Cancer involves the uncontrolled, abnormal growth of cells and affects other tissues. Kinase has an impact on proliferating the cells and causing cancer. For the purpose of treating cancer, PIM kinase is a potential target. The pro-viral Integration site for moloney murine leukaemia virus (PIM) kinases is responsible for the tumorigenesis, by phosphorylating the proteins that control the cell cycle and cell proliferation. PIM-1, PIM-2, and PIM-3 are the three distinct isoforms of PIM kinases. The JAK/STAT pathway is essential for controlling how PIM genes are expressed. PIM kinase is also linked withPI3K/AKT/mTOR pathway in various types of cancers. The overexpression of PIM kinase will cause cancer. Currently, there are significant efforts being made in medication design and development to target its inhibition. A few small chemical inhibitors (E.g., SGI-1776, AZD1208, LGH447) that specifically target the PIM proteins' adenosine triphosphate (ATP)-binding domain have been identified. PIM kinase antagonists have a remarkable effect on different types of cancer. Despite conducting clinical trials on SGI-1776, the first PIM inhibitory agent, was prematurely withdrawn, making it unable to generate concept evidence. On the other hand, in recent years, it has aided in hastening the identification of multiple new PIM inhibitors. Cyanopyridines and Pyrazolo[1,5-a]pyrimidinecan act as potent PIM kinase inhibitors for cancer therapy. We explore the involvement of oncogenic transcription factor c-Mycandmi-RNA in relation to PIM kinase. In this article, we highlight the oncogenic effects, and structural insights into PIM kinase inhibitors for the treatment of cancer.

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.

Discovery of PIM-1 kinase inhibitors based on the 2,5-disubstituted 1,3,4-oxadiazole scaffold against prostate cancer: Design, synthesis, in vitro and in vivo cytotoxicity investigation

PIM-1 kinases play an established role in prostate cancer development and progression. This research work tackles the design and synthesis of new PIM-1 kinase targeting 2,5-disubstituted-1,3,4-oxadiazoles 10a-g&11a-f, and investigation thereof as potential anti-cancer agents through in vitro cytotoxicity assay followed by in vivo studies along with exploration of this chemotype's plausible mechanism of action. In vitro cytotoxicity experiments have disclosed 10f as the most potent derivative against PC-3 cells (IC₅₀ = 16 nM) compared to the reference drug Staurosporine (IC₅₀ = 0.36 μM), also eliciting good cytotoxicity against HepG2 and MCF-7 cells (IC₅₀ = 0.13 and 5.37 μM, respectively). Investigating PIM-1 kinase inhibitory activity of compound 10f revealed an IC₅₀ of 17 nM paralleled to that of Staurosporine (IC₅₀ = 16.7 nM). Furthermore, compound 10f displayed an antioxidant activity eliciting a DPPH inhibition ratio of 94% as compared to Trolox (96%). Further investigation demonstrated that 10f induced apoptosis in treated PC-3 cells by 43.2-fold (19.44%) compared to 0.45% in control. 10f also disrupted the PC-3 cell cycle by increasing the cell population at the PreG1-phase by 19.29-fold while decreasing the G2/M-phase by 0.56-fold compared to control. Moreover, 10f affected a downregulation of JAK2, STAT3 and Bcl-2 and upregulation of caspases 3, 8 and 9 levels that activated the caspase-dependent apoptosis. Finally, in vivo 10f-treatment caused a significant increase in tumor inhibition by 64.2% compared to 44.5% in Staurosporine treatment of the PC-3 xenograft mouse model. Additionally, it improved the hematological, biochemical parameters, and histopathological examinations compared to control untreated animals. Finally, docking of 10f with the ATP-binding site of PIM-1 kinase demonstrated good recognition of and effective binding to the active site. In conclusion, compound 10f represents a promising lead compound that merits further future optimization for controlling prostate cancer.

New Quinoxaline Derivatives as Dual Pim-1/2 Kinase Inhibitors: Design, Synthesis and Biological Evaluation

Proviral integration site for Moloney murine leukemia virus (Pim)-1/2 kinase overexpression has been identified in a variety of hematologic (e.g., multiple myeloma or acute myeloid leukemia (AML)) and solid (e.g., colorectal carcinoma) tumors, playing a key role in cancer progression, metastasis, and drug resistance, and is linked to poor prognosis. These kinases are thus considered interesting targets in oncology. We report herein the design, synthesis, structure–activity relationships (SAR) and in vitro evaluations of new quinoxaline derivatives, acting as dual Pim1/2 inhibitors. Two lead compounds (5c and 5e) were then identified, as potent submicromolar Pim-1 and Pim-2 inhibitors. These molecules were also able to inhibit the growth of the two human cell lines, MV4-11 (AML) and HCT-116 (colorectal carcinoma), expressing high endogenous levels of Pim-1/2 kinases.

Molecular Recognition and Self-Organization in Life Phenomena Studied by a Statistical Mechanics of Molecular Liquids, the RISM/3D-RISM Theory

There are two molecular processes that are essential for living bodies to maintain their life: the molecular recognition, and the self-organization or self-assembly. Binding of a substrate by an enzyme is an example of the molecular recognition, while the protein folding is a good example of the self-organization process. The two processes are further governed by the other two physicochemical processes: solvation and the structural fluctuation. In the present article, the studies concerning the two molecular processes carried out by Hirata and his coworkers, based on the statistical mechanics of molecular liquids or the RISM/3D-RISM theory, are reviewed.

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.

Resveratrol suppresses gastric cancer cell proliferation and survival through inhibition of PIM-1 kinase activity

The proviral integration site for Moloney murine leukemia virus (PIM) family of serine/threonine-specific kinases consist of three isoforms, that regulate proliferation, apoptosis, metabolism, invasion, and metastasis of cancer cells. Among these, abnormally elevated kinase activity of PIM-1 contributes to the progression of gastric cancer and predicts poor prognosis and a low survival rate in gastric cancer patients. In the present study, we found that resveratrol, one of the representative chemopreventive and anticarcinogenic phytochemicals, directly binds to PIM-1 and thereby inhibits its catalytic activity in human gastric cancer SNU-601 cells. This resulted in suppression of phosphorylation of the proapoptotic Bad, a known substrate of PIM-1. Resveratrol, by inactivating PIM-1, also inhibited anchorage-independent growth and proliferation of SNU-601 cells. To understand the molecular interaction between resveratrol and PIM-1, we conducted docking simulation and found that resveratrol directly binds to the PIM-1 at the ATP-binding pocket. In conclusion, the proapototic and anti-proliferative effects of resveratrol in gastric cancer cells are likely to be mediated through suppression of PIM-1 kinase activity, which may represent a novel mechanism underlying its chemopreventive and anticarcinogenic actions.

A new method for estimating the relative binding free energy, derived from a free energy variational principle for the Pim-1-kinase-ligand and FKBP-ligand systems

In this study, a new method is proposed for calculating the relative binding free energy between a ligand and a protein, derived from a free energy variational principle (FEVP). To address the shortcomings of the method used in our previous study, we incorporate the dynamical fluctuation of a ligand in the FEVP calculation. The present modified method is applied to the Pim-1-kinase-ligand system and also to the FKBP-ligand system as a comparison with our previous work. Any inhibitor of Pim-1 kinase is expected to function as an anti-cancer drug. Some improvements are observed in the results compared to the previous study. The present work also shows comparable or better results than approaches using a standard technique of binding free energy calculations, such as the LIE and the MM-PB/SA methods. The possibility of applying the present method in the drug discovery process is also discussed.

Targeting Pim Kinases and DAPK3 to Control Hypertension

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

Structure-based design of novel quinoxaline-2-carboxylic acids and analogues as Pim-1 inhibitors

We identified a new series of quinoxaline-2-carboxylic acid derivatives, targeting the human proviral integration site for Moloney murine leukemia virus-1 (HsPim-1) kinase. Seventeen analogues were synthesized providing useful insight into structure-activity relationships studied. Docking studies realized in the ATP pocket of HsPim-1 are consistent with an unclassical binding mode of these inhibitors. The lead compound 1 was able to block HsPim-1 enzymatic activity at nanomolar concentrations (IC₅₀ of 74 nM), with a good selectivity profile against a panel of mammalian protein kinases. In vitro studies on the human chronic myeloid leukemia cell line KU812 showed an antitumor activity at micromolar concentrations. As a result, compound 1 represents a promising lead for the design of novel anticancer targeted therapies.

Pre-operative neutrophil count and neutrophil-lymphocyte count ratio (NLCR) in predicting the histological grade of paediatric brain tumours: a preliminary study

INTRODUCTION

The neutrophil-lymphocyte count ratio (NLCR) is an established prognostic marker for renal, lung and colorectal carcinomas and has been suggested to be predictive of histological grade and outcome in adult intracranial tumours. The purpose of this study was to determine whether a correlation of the pre-operative neutrophil count (NC) and NLCR with the final histological grade exists in paediatric intracranial tumours.

METHODS

A retrospective analysis was undertaken at a single centre. Patients less than 18 years old at the time of surgery who underwent tumour-related procedures from 2006 to 2015 were included. Patients with recurrent tumours, previous bone marrow transplant and metastases were excluded. Pre-operative full blood counts (FBC), collected before the diagnosis of intracranial pathology and before administration of steroids, were matched with histological diagnosis for each patient. Post-operative FBC was also recorded, together with survival data where applicable.

RESULTS

A total of 116 patients (74 male, 42 female; mean age, 8 ± 0.9 years) with a diagnosis of primary intracranial tumours had pre-operative FBC that could be matched to final histological grade. Pre-operative NC and NLCR were higher with increasing grade of tumour: grade 1 (NC 4.29 10⁹/l, NLCR 2.26), grade 2 (NC 4.59 10⁹/l, NLCR 2.38), grade 3 (NC 5.67 10⁹/l, NLCR 2.72) and grade 4 (NC 6.59 10⁹/l, NLCR 3.31). Patients with WHO grade 1 and 2 tumours pooled together had a lower NC (4.37 95% CI ± 0.67 10⁹/l) compared to WHO grade 3 and 4 patients (6.41 95% CI ± 0.99 10⁹/l, p = 0.0013). The NLCR was lower in grade 1 and 2 tumours (2.29 ± 0.59) (compared to grade 3 and 4 tumours; 3.20 ± 0.76) but this did not reach significance (p = 0.069). The subgroup of patients with pilocytic astrocytoma had a significantly lower NC when compared to patients with high-grade tumours (p = 0.005). Medulloblastoma and supratentorial PNET subgroups had significantly higher NC compared to the low-grade group (p = 0.033, p = 0.002). Post-operative NC was significantly higher in the high-grade tumours (p = 0.034), but no difference was observed for NLCR (p = 0.28).

CONCLUSIONS

No evidence exists to support the correlation of pre-operative NC or NLCR to histological diagnosis in paediatric intracranial tumours. Our results indicate that a higher pre-operative NC/NLCR correlates with a higher histological grade of tumour. This suggests that immunological mechanisms may be involved in the pathogenesis of paediatric brain tumours, and a further prospective study is required to substantiate and expand these findings.

Loss of PIM1 correlates with progression and prognosis of salivary adenoid cystic carcinoma (SACC)

Background

Increasing evidence indicates that PIM1 is a potential prognostic marker and target for cancer treatment but its precise mechanisms of action remain to be determined in salivary adenoid cystic carcinoma (SACC). This study aims to decipher the prognostic and mechanistic role of PIM1 in progression of SACC cells and tumor tissues.

Methods

A SACC cell line (ACC-M) was transfected with shRNA plasmids targeting the PIM1 gene. The expression levels of PIM1, RUNX3 and p21 were measured by quantitative real-time PCR and western blot. Subcellular translocalization of RUNX3 and p21 proteins was assessed using immunofluorescence, and cell cycle phase was quantified using flow cytometry. A total of 97 SACC patients were retrospectively analyzed by clinicopathologic characteristics and survival outcomes.

Results

After down-regulation of PIM1 in ACC-M cells, RUNX3 and p21 proteins were translocated from cytoplasm to nucleus, with a decrease of p21 expression and increase of G0/G1 phase cells. PIM1 and RUNX3 levels show a distinct covariance. PIM1 is associated with T-status, lymph node involvement, nerve invasion, and distant metastasis in SACC tissues. Patients with low PIM1 level had a better outcome than those with higher PIM1 level.

Conclusions

PIM1 is multifunctional in ACC-M cells and it serves as a neoteric therapeutic target and potential prognostic marker for SACC patients.

A Systematic Analysis of the Binding Affinity between the Pim-1 Kinase and Its Inhibitors Based on the MM/3D-RISM/KH Method

A systematic study of the binding affinities of 16 lead compounds targeting the Pim-1 kinase based on the 3D-RISM/KH theory and MD simulations is reported. The results show a correlation coefficient R = 0.69 between the theoretical and experimental values of the binding free energy. This demonstrates that the method is applicable to the problem of compound screening and lead optimization, for which relative values of the free energy among the compounds have significance. We elucidate the contribution of the ligand fragments to the binding free energy. Our results indicate that the interactions between the residues and the triazolo[4,3-b]pyridazine scaffold as well as the phenyl ring of the ligand molecule make significant contributions to stabilization of the complex. Using the 3D-RISM/KH theory, we further analyze the probability distribution of a ligand fragment around the protein-ligand complex in which the substituent around the phenyl ring is removed from the ligand. The results demonstrate that the 3D-RISM/KH theory is capable of predicting the position of substitution on a ligand that has a higher affinity to a target protein.

The role of PIM1/PIM2 kinases in tumors of the male reproductive system

The PIM family of serine/threonine kinases has three highly conserved isoforms (PIM1, PIM2 and PIM3). PIM proteins are regulated through transcription and stability by JAK/STAT pathways and are overexpressed in hematological malignancies and solid tumors. The PIM kinases possess weak oncogenic abilities, but enhance other genes or chemical carcinogens to induce tumors. We generated conditional transgenic mice that overexpress PIM1 or PIM2 in male reproductive organs and analyzed their contribution to tumorigenesis. We found an increase in alterations of sexual organs and hyperplasia in the transgenic mice correlating with inflammation. We also found that PIM1/2 are overexpressed in a subset of human male germ cells and prostate tumors correlating with inflammatory features and stem cell markers. Our data suggest that PIM1/2 kinase overexpression is a common feature of male reproductive organs tumors, which provoke tissue alterations and a large inflammatory response that may act synergistically during the process of tumorigenesis. There is also a correlation with markers of cancer stem cells, which may contribute to the therapy resistance found in tumors overexpressing PIM kinases.

MicroRNA-33a-mediated downregulation of Pim-3 kinase expression renders human pancreatic cancer cells sensitivity to gemcitabine

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers, with less than 5% of patients surviving 5 years beyond diagnosis. Systemic therapies, particularly gemcitabine, have a modest clinical benefit, but chemoresistance limits their efficacy. Here, we demonstrate that plasma miR-33a levels positively correlated with miR-33a levels in tumor tissues of patients with PDAC and are a good prognostic indicator of overall survival. Overexpression of miR-33a inhibited tumor cell proliferation and increased the chemosensitivity to gemcitabine both in vitro and in vivo. Moreover, miR-33a targets Pim-3 directly in PDAC. Pim-3 expression was a prognostic indicator related to poor survival in pancreatic cancer patients. Plasma miR-33a levels were significantly lower in pancreatic cancer patients with high Pim-3 protein expression than in healthy controls. Furthermore, overexpression of miR-33a in pancreatic cancer cell lines suppressed Pim-3 expression, leading to downregulation of the AKT/Gsk-3β/β-catenin pathway. Overall, these results indicate that miR-33a functions as a tumor suppressor that downregulates Pim-3 kinase expression to inhibit both pancreatic tumor growth and gemcitabine resistance via the AKT/β-catenin pathway. Hence, detection of plasma miR-33a may be a simple and convenient method of predicting therapeutic responses.

Pim-1 kinase as cancer drug target: An update

Proviral integration site for Moloney murine leukemia virus-1 (Pim-1) is a serine/threonine kinase that regulates multiple cellular functions such as cell cycle, cell survival, drug resistance. Aberrant elevation of Pim-1 kinase is associated with numerous types of cancer. Two distinct isoforms of Pim-1 (Pim-1S and Pim-1L) show distinct cellular functions. Pim-1S predominately localizes to the nucleus and Pim-1L localizes to plasma membrane for drug resistance. Recent studies show that mitochondrial Pim-1 maintains mitochondrial integrity. Pim-1 is emerging as a cancer drug target, particularly in prostate cancer. Recently the potent new functions of Pim-1 in immunotherapy, senescence bypass, metastasis and epigenetic dynamics have been found. The aim of the present updated review is to provide brief information regarding networks of Pim-1 kinase and focus on its recent advances as a novel drug target.