The novel choline kinase inhibitor ICL-CCIC-0019 reprograms cellular metabolism and inhibits cancer cell growth

Choline kinases: Enzymatic activity, involvement in cancer and other diseases, inhibitors

One of the aspects of tumor metabolism that distinguish it from healthy tissue is the phosphorylation of choline by choline kinases, which initiates the synthesis of phosphatidylcholine. Presently, there is a lack of comprehensive reviews discussing the current understanding of the role of choline kinase in cancer processes, as well as studies on the anti-tumor properties of choline kinase inhibitors. To address these gaps, this review delves into the enzymatic and non-enzymatic properties of CHKα and CHKβ and explores their precise involvement in cancer processes, particularly cancer cell proliferation. Additionally, we discuss clinical aspects of choline kinases in various tumor types, including pancreatic ductal adenocarcinoma, ovarian cancer, lung adenocarcinoma, lymphoma, leukemia, hepatocellular carcinoma, colon adenocarcinoma, and breast cancer. We examine the potential of CHKα inhibitors as anti-tumor drugs, although they are not yet in the clinical trial phase. Finally, the paper also touches upon the significance of choline kinases in non-cancerous diseases.

Hypoxia Dependent Inhibition of Glioblastoma Cell Proliferation, Invasion, and Metabolism by the Choline-Kinase Inhibitor JAS239

Background: Elevated choline kinase alpha (ChoK) levels are observed in most solid tumors, including glioblastomas (GBM), and ChoK inhibitors have demonstrated limited efficacy in GBM models. Given that hypoxia is associated with resistance to GBM therapy, we hypothesized that tumor hypoxia could be responsible for the limited response. Therefore, we evaluated the effects of hypoxia on the function of JAS239, a potent ChoK inhibitor in four GBM cell lines. Methods: Rodent (F98 and 9L) and human (U-87 MG and U-251 MG) GBM cell lines were subjected to 72 h of hypoxic conditioning and treated with JAS239 for 24 h. NMR metabolomic measurements and analyses were performed to evaluate the signaling pathways involved. In addition, cell proliferation, cell cycle progression, and cell invasion parameters were measured in 2D cell monolayers as well as in 3D cell spheroids, with or without JAS239 treatment, in normoxic or hypoxic cells to assess the effect of hypoxia on JAS239 function. Results: Hypoxia and JAS239 treatment led to significant changes in the cellular metabolic pathways, specifically the phospholipid and glycolytic pathways, associated with a reduction in cell proliferation via induced cell cycle arrest. Interestingly, JAS239 also impaired GBM invasion. However, effects from JAS239 were variable depending on the cell line, reflecting the inherent heterogeneity of GBMs. Conclusions: Our findings indicate that JAS239 and hypoxia can deregulate cellular metabolism, inhibit cell proliferation, and alter cell invasion. These results may be useful for designing new therapeutic strategies based on ChoK inhibition, which can act on multiple pro-tumorigenic features.

Inhibition of glioblastoma cell proliferation and invasion by the choline-kinase inhibitor JAS239 varies with cell type and hypoxia

Background

Elevated choline kinase alpha (ChoK) is observed in most solid tumours including glioblastomas (GBM), yet until recently, inhibitors of ChoK have demonstrated limited efficacy in GBM models. Given that hypoxia is associated with GBM therapy resistance, we hypothesised that tumour hypoxia could be responsible for such limitations. We therefore evaluated in GBM cells, the effect of hypoxia on the function of JAS239, a potent ChoK inhibitor.

Methods

Rodent (F98 and 9L) and human (U-87 MG and U-251 MG) GBM cell lines were subjected to 72 hours of hypoxia conditioning and treated with JAS239 for 24 hours. NMR metabolomic measurements and analyses were performed to evaluate the signalling pathways involved. In addition, cell proliferation, cell cycle progression and cell invasion were measured in cell monolayers and 3D spheroids, with or without JAS239 treatment in normoxic or hypoxic cells to assess how hypoxia affects JAS239 function.

Results

Hypoxia and JAS239 treatment led to significant changes in the cellular metabolic pathways, specifically the phospholipid and glycolytic pathways associated with a reduction in cell proliferation via induced cell cycle arrest. Interestingly, JAS239 also impaired GBM invasion. However, JAS239 effects were variable depending on the cell line, reflecting the inherent heterogeneity observed in GBMs.

Conclusion

Our findings indicate that JAS239 and hypoxia can deregulate cellular metabolism, inhibit proliferation and alter cell invasion. These results may be useful for the design of new therapeutic strategies based on ChoK inhibition that can act on multiple pro-tumorigenic features.

Bench to Bedside Development of [18F]Fluoromethyl-(1,2-2H4)choline ([18F]D4-FCH)

Malignant transformation is characterised by aberrant phospholipid metabolism of cancers, associated with the upregulation of choline kinase alpha (CHKα). Due to the metabolic instability of choline radiotracers and the increasing use of late-imaging protocols, we developed a more stable choline radiotracer, [18F]fluoromethyl-[1,2-2H4]choline ([18F]D4-FCH). [18F]D4-FCH has improved protection against choline oxidase, the key choline catabolic enzyme, via a 1H/2D isotope effect, together with fluorine substitution. Due to the promising mechanistic and safety profiles of [18F]D4-FCH in vitro and preclinically, the radiotracer has transitioned to clinical development. [18F]D4-FCH is a safe positron emission tomography (PET) tracer, with a favourable radiation dosimetry profile for clinical imaging. [18F]D4-FCH PET/CT in lung and prostate cancers has shown highly heterogeneous intratumoral distribution and large lesion variability. Treatment with abiraterone or enzalutamide in metastatic castrate-resistant prostate cancer patients elicited mixed responses on PET at 12-16 weeks despite predominantly stable radiological appearances. The sum of the weighted tumour-to-background ratios (TBRs-wsum) was associated with the duration of survival.

Recent advancements in nanomedicine based lipid metabolism for tumour immunotherapy

Therapy on lipid metabolism is emerging as a groundbreaking cancer treatment, offering the unprecedented opportunity to effectively treat and in several cases. Tumorigenesis is inextricably linked to lipid metabolism. In this regard, the features of lipid metabolism include lipid synthesis, decomposition, metabolism and lipid storage and mobilisation from intracellular lipid droplets. Most importantly, the regulation of lipid metabolism is central to the appropriate immune response of tumour cells, and ultimately to exert the immune efforts to realise the perspective of many anti-tumour effects. Different cancers and immune cells have different dependence on lipid metabolism, playing a pivotal role in differentiation and function of immune cells. However, what lies before the immunotherapy targeting lipid metabolism is side effects of systemic toxicity and defects of individual drugs, which strongly highlights that nanodelivery strategy is a magnet for it to enhance drug efficiency, reduce drug toxicity and improve application deficiencies. This review will first focus on emerging research progress of lipid metabolic reprogramming mechanism, and then explore the complex role of lipid metabolism in the tumour cells including the effect on immune cells and their nano-preparations of monotherapy and multiple therapies used in combination, in a shift away from conventional cancer research.HighlightsThe regulation of lipid metabolism is central to the appropriate immune response of tumour cells, and ultimately to exert the immune efforts to realise the perspective of many anti-tumour effects.Preparations of focusing lipid metabolism have side effects of systemic toxicity and defects of individual drugs. It strongly highlights that nanodelivery strategy is a magnet for it to enhance drug efficiency, reduce drug toxicity and improve application deficiencies.This review will first focus on emerging research progress of lipid metabolic reprogramming mechanism, and then explore the complex role of lipid metabolism in the tumour cells including the effect on immune cells as well as their nano-preparations of monotherapy and multiple therapies used in combination, in a shift away from conventional cancer research.

Integrative genetic analysis identifies FLVCR1 as a plasma-membrane choline transporter in mammals

Genome-wide association studies (GWASs) of serum metabolites have the potential to uncover genes that influence human metabolism. Here, we combined an integrative genetic analysis that associates serum metabolites to membrane transporters with a coessentiality map of metabolic genes. This analysis revealed a connection between feline leukemia virus subgroup C cellular receptor 1 (FLVCR1) and phosphocholine, a downstream metabolite of choline metabolism. Loss of FLVCR1 in human cells strongly impairs choline metabolism due to the inhibition of choline import. Consistently, CRISPR-based genetic screens identified phospholipid synthesis and salvage machinery as synthetic lethal with FLVCR1 loss. Cells and mice lacking FLVCR1 exhibit structural defects in mitochondria and upregulate integrated stress response (ISR) through heme-regulated inhibitor (HRI) kinase. Finally, Flvcr1 knockout mice are embryonic lethal, which is partially rescued by choline supplementation. Altogether, our findings propose FLVCR1 as a major choline transporter in mammals and provide a platform to discover substrates for unknown metabolite transporters.

Mapping of exogenous choline uptake and metabolism in rat glioblastoma using deuterium metabolic imaging (DMI)

Introduction

There is a lack of robust metabolic imaging techniques that can be routinely applied to characterize lesions in patients with brain tumors. Here we explore in an animal model of glioblastoma the feasibility to detect uptake and metabolism of deuterated choline and describe the tumor-to-brain image contrast.

Methods

RG2 cells were incubated with choline and the level of intracellular choline and its metabolites measured in cell extracts using high resolution 1H NMR. In rats with orthotopically implanted RG2 tumors deuterium metabolic imaging (DMI) was applied in vivo during, as well as 1 day after, intravenous infusion of 2H9-choline. In parallel experiments, RG2-bearing rats were infused with [1,1',2,2'-2H4]-choline and tissue metabolite extracts analyzed with high resolution 2H NMR to identify molecule-specific 2H-labeling in choline and its metabolites.

Results

In vitro experiments indicated high uptake and fast phosphorylation of exogenous choline in RG2 cells. In vivo DMI studies revealed a high signal from the 2H-labeled pool of choline + metabolites (total choline, 2H-tCho) in the tumor lesion but not in normal brain. Quantitative DMI-based metabolic maps of 2H-tCho showed high tumor-to-brain image contrast in maps acquired both during, and 24 h after deuterated choline infusion. High resolution 2H NMR revealed that DMI data acquired during 2H-choline infusion consists of free choline and phosphocholine, while the data acquired 24 h later represent phosphocholine and glycerophosphocholine.

Discussion

Uptake and metabolism of exogenous choline was high in RG2 tumors compared to normal brain, resulting in high tumor-to-brain image contrast on DMI-based metabolic maps. By varying the timing of DMI data acquisition relative to the start of the deuterated choline infusion, the metabolic maps can be weighted toward detection of choline uptake or choline metabolism. These proof-of-principle experiments highlight the potential of using deuterated choline combined with DMI to metabolically characterize brain tumors.

Bilayer Forming Phospholipids as Targets for Cancer Therapy

Phospholipids represent a crucial component for the structure of cell membranes. Phosphatidylcholine and phosphatidylethanolamine are two phospholipids that comprise the majority of cell membranes. De novo biosynthesis of phosphatidylcholine and phosphatidylethanolamine occurs via the Kennedy pathway, and perturbations in the regulation of this pathway are linked to a variety of human diseases, including cancer. Altered phosphatidylcholine and phosphatidylethanolamine membrane content, phospholipid metabolite levels, and fatty acid profiles are frequently identified as hallmarks of cancer development and progression. This review summarizes the research on how phospholipid metabolism changes over oncogenic transformation, and how phospholipid profiling can differentiate between human cancer and healthy tissues, with a focus on colorectal cancer, breast cancer, and non-small cell lung cancer. The potential for phospholipids to serve as biomarkers for diagnostics, or as anticancer therapy targets, is also discussed.

Biological Evaluation of New Thienopyridinium and Thienopyrimidinium Derivatives as Human Choline Kinase Inhibitors

Due to its role in lipid biosynthesis, choline kinase α1 (CKα1) is an interesting target for the development of new antitumor agents. In this work, we present a series of 41 compounds designed based on the well-known and successful strategy of introducing thienopyridine and pyrimidine as bioisosteres of other heterocycles in active antitumor compounds. Notwithstanding the fact that some of these compounds do not show significant enzymatic inhibition, others, in contrast, feature substantially improved enzymatic and antiproliferative inhibition values. This is also confirmed by docking analysis, whereby compounds with longer linkers and thienopyrimidine cationic head have been identified as the most compelling. Among the best compounds is Ff-35, which inhibits the growth of different tumor cells at submicromolar concentrations. Moreover, Ff-35 is more potent in inhibiting CKα1 than other previous biscationic derivatives. Treatment of A549, Hela, and MDA-MB-231 cells with Ff-35 results in their arrest at the G1 phase of the cell cycle. Furthermore, the compound induces cellular apoptosis in a concentration-dependent manner. Altogether, these findings indicate that Ff-35 is a promising new chemotherapeutic agent with encouraging preclinical potential.

Phage-Choline Kinase Inhibitor Combination to Control Pseudomonas aeruginosa: A Promising Combo

BACKGROUND

Pseudomonas aeruginosa is one of the most prevalent opportunistic pathogens in humans that has thrived and proved to be difficult to control in this "post-antibiotic era." Antibiotic alternatives are necessary for fighting against this resilient bacterium. Even though phages might not be "the wonder drug" that solves everything, they still provide a viable option to combat P. aeruginosa and curb the threat it imposes.

MAIN FINDINGS

The combination of antibiotics with phages, however, poses a propitious treatment option for P. aeruginosa. Choline kinase (ChoK) is the enzyme that synthesizes phosphorylcholine subsequently incorporated into lipopolysaccharide located at the outer membrane of gram-negative bacteria. Recently, inhibition of ChoKs has been proposed as a promising antibacterial strategy. Successful docking of Hemicholinium-3, a choline kinase inhibitor, to the model structure of P. aeruginosa ChoK also supports the use of this inhibitor or its derivatives to inhibit the growth of this microorganism.

CONCLUSION

Therefore, the combination of the novel antimicrobial "choline kinase inhibitors (ChoKIs)" with a phage cocktail or synthetic phages as a potential treatment for P. aeruginosa infection has been proposed.

Consideration of Metabolite Efflux in Radiolabelled Choline Kinetics

Hypoxia is a complex microenvironmental condition known to regulate choline kinase α (CHKA) activity and choline transport through transcription factor hypoxia-inducible factor-1α (HIF-1α) and, therefore, may confound the uptake of choline radiotracer [18F]fluoromethyl-[1,2-2H4]-choline ([18F]-D4-FCH). The aim of this study was to investigate how hypoxia affects the choline radiotracer dynamics. Three underlying mechanisms by which hypoxia could potentially alter the uptake of the choline radiotracer, [18F]-D4-FCH, were investigated: 18F-D4-FCH import, CHKA phosphorylation activity, and the efflux of [18F]-D4-FCH and its phosphorylated product [18F]-D4-FCHP. The effects of hypoxia on [18F]-D4-FCH uptake were studied in CHKA-overexpressing cell lines of prostate cancer, PC-3, and breast cancer MDA-MB-231 cells. The mechanisms of radiotracer efflux were assessed by the cell uptake and immunofluorescence in vitro and examined in vivo (n = 24). The mathematical modelling methodology was further developed to verify the efflux hypothesis using [18F]-D4-FCH dynamic PET scans from non-small cell lung cancer (NSCLC) patients (n = 17). We report a novel finding involving the export of phosphorylated [18F]-D4-FCH and [18F]-D4-FCHP via HIF-1α-responsive efflux transporters, including ABCB4, when the HIF-1α level is augmented. This is supported by a graphical analysis of human data with a compartmental model (M2T6k + k5) that accounts for the efflux. Hypoxia/HIF-1α increases the efflux of phosphorylated radiolabelled choline species, thus supporting the consideration of efflux in the modelling of radiotracer dynamics.

Novel Non-Congeneric Derivatives of the Choline Kinase Alpha Inhibitor ICL-CCIC-0019

Choline kinase alpha (CHKA) is a promising target for the development of cancer therapeutics. We have previously reported ICL-CCIC-0019, a potent CHKA inhibitor with high cellular activity but with some unfavorable pharmacological properties. In this work, we present an active analogue of ICL-CCIC-0019 bearing a piperazine handle (CK146) to facilitate further structural elaboration of the pharmacophore and thus improve the biological profile. Two different strategies were evaluated in this study: (1) a prodrug approach whereby selective CHKA inhibition could be achieved through modulating the activity of CK146, via the incorporation of an ε-(Ac) Lys motif, cleavable by elevated levels of histone deacetylase (HDAC) and cathepsin L (CTSL) in tumour cells; (2) a prostate-specific membrane antigen (PSMA) receptor targeted delivery strategy. Prodrug (CK145) and PSMA-targeted (CK147) derivatives were successfully synthesized and evaluated in vitro. While the exploitation of CK146 in those two strategies did not deliver the expected results, important and informative structure-activity relationships were observed and have been reported.

DNA Methylation of Human Choline Kinase Alpha Promoter-Associated CpG Islands in MCF-7 Cells

Choline kinase (CK) is the enzyme catalyzing the first reaction in CDP-choline pathway for the biosynthesis of phosphatidylcholine. Higher expression of the α isozyme of CK has been implicated in carcinogenesis, and inhibition or downregulation of CKα (CHKA) is a promising anticancer approach. This study aimed to investigate the regulation of CKα expression by DNA methylation of the CpG islands found on the promoter of this gene in MCF-7 cells. Four CpG islands have been predicted in the 2000 bp promoter region of ckα (chka) gene. Six CpG island deletion mutants were constructed using PCR site-directed mutagenesis method and cloned into pGL4.10 vectors for promoter activity assays. Deletion of CpG4C region located between -225 and -56 significantly increased the promoter activity by 4-fold, indicating the presence of important repressive transcription factor binding site. The promoter activity of methylated full-length promoter was significantly lower than the methylated CpG4C deletion mutant by 16-fold. The results show that DNA methylation of CpG4C promotes the binding of the transcription factor that suppresses the promoter activity. Electrophoretic mobility shift assay analysis showed that cytosine methylation at MZF1 binding site in CpG4C increased the binding of putative MZF1 in nuclear extract. In conclusion, the results suggest that DNA methylation decreased the promoter activity by promoting the binding of putative MZF1 transcription factor at CpG4C region of the ckα gene promoter.

Choline Kinase: An Unexpected Journey for a Precision Medicine Strategy in Human Diseases

Choline kinase (ChoK) is a cytosolic enzyme that catalyzes the phosphorylation of choline to form phosphorylcholine (PCho) in the presence of ATP and magnesium. ChoK is required for the synthesis of key membrane phospholipids and is involved in malignant transformation in a large variety of human tumours. Active compounds against ChoK have been identified and proposed as antitumor agents. The ChoK inhibitory and antiproliferative activities of symmetrical bispyridinium and bisquinolinium compounds have been defined using quantitative structure-activity relationships (QSARs) and structural parameters. The design strategy followed in the development of the most active molecules is presented. The selective anticancer activity of these structures is also described. One promising anticancer compound has even entered clinical trials. Recently, ChoKα inhibitors have also been proposed as a novel therapeutic approach against parasites, rheumatoid arthritis, inflammatory processes, and pathogenic bacteria. The evidence for ChoKα as a novel drug target for approaches in precision medicine is discussed.

The PD-L1 metabolic interactome intersects with choline metabolism and inflammation

Background

Harnessing the power of the immune system by using immune checkpoint inhibitors has resulted in some of the most exciting advances in cancer treatment. The full potential of this approach has, however, not been fully realized for treating many cancers such as pancreatic and breast cancer. Cancer metabolism influences many aspects of cancer progression including immune surveillance. An expanded understanding of how cancer metabolism can directly impact immune checkpoints may allow further optimization of immunotherapy. We therefore investigated, for the first time, the relationship between the overexpression of choline kinase-α (Chk-α), an enzyme observed in most cancers, and the expression of the immune checkpoint PD-L1.

Methods

We used small interfering RNA to downregulate Chk-α, PD-L1, or both in two triple-negative human breast cancer cell lines (MDA-MB-231 and SUM-149) and two human pancreatic ductal adenocarcinoma cell lines (Pa09C and Pa20C). The effects of the downregulation were studied at the genomic, proteomic, and metabolomic levels. The findings were compared with the results obtained by the analysis of public data from The Cancer Genome Atlas Program.

Results

We identified an inverse dependence between Chk-α and PD-L1 at the genomic, proteomic, and metabolomic levels. We also found that prostaglandin-endoperoxide synthase 2 (COX-2) and transforming growth factor beta (TGF-β) play an important role in this relationship. We independently confirmed this relationship in human cancers by analyzing data from The Cancer Genome Atlas Program.

Conclusions

Our data identified previously unknown roles of PD-L1 in cancer cell metabolic reprogramming, and revealed the immunosuppressive increased PD-L1 effect of Chk-α downregulation. These data suggest that PD-L1 regulation of metabolism may be mediated through Chk-α, COX-2, and TGF-β. The observations provide new insights that can be applied to the rational design of combinatorial therapies targeting immune checkpoints and cancer metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40170-021-00245-w.

Recent advances in the design of choline kinase α inhibitors and the molecular basis of their inhibition

Upregulated choline metabolism, characterized by an increase in phosphocholine (PCho), is a hallmark of oncogenesis and tumor progression. Choline kinase (ChoK), the enzyme responsible for PCho synthesis, has consequently become a promising drug target for cancer therapy and as such a significant number of ChoK inhibitors have been developed over the last few decades. More recently, due to the role of this enzyme in other pathologies, ChoK inhibitors have also been used in new therapeutic approaches against malaria and rheumatoid arthritis. Here, we review research results in the field of ChoKα inhibitors from their synthesis to the molecular basis of their binding mode. Strategies for the development of inhibitors and their selectivity on ChoKα over ChoKβ, the plasticity of the choline-binding site, the discovery of new exploitable binding sites, and the allosteric properties of this enzyme are highlighted. The outcomes summarized in this review will be a useful guide to develop new multifunctional potent drugs for the treatment of various human diseases.

Lipids and cancer: Emerging roles in pathogenesis, diagnosis and therapeutic intervention

With the advent of effective tools to study lipids, including mass spectrometry-based lipidomics, lipids are emerging as central players in cancer biology. Lipids function as essential building blocks for membranes, serve as fuel to drive energy-demanding processes and play a key role as signaling molecules and as regulators of numerous cellular functions. Not unexpectedly, cancer cells, as well as other cell types in the tumor microenvironment, exploit various ways to acquire lipids and extensively rewire their metabolism as part of a plastic and context-dependent metabolic reprogramming that is driven by both oncogenic and environmental cues. The resulting changes in the fate and composition of lipids help cancer cells to thrive in a changing microenvironment by supporting key oncogenic functions and cancer hallmarks, including cellular energetics, promoting feedforward oncogenic signaling, resisting oxidative and other stresses, regulating intercellular communication and immune responses. Supported by the close connection between altered lipid metabolism and the pathogenic process, specific lipid profiles are emerging as unique disease biomarkers, with diagnostic, prognostic and predictive potential. Multiple preclinical studies illustrate the translational promise of exploiting lipid metabolism in cancer, and critically, have shown context dependent actionable vulnerabilities that can be rationally targeted, particularly in combinatorial approaches. Moreover, lipids themselves can be used as membrane disrupting agents or as key components of nanocarriers of various therapeutics. With a number of preclinical compounds and strategies that are approaching clinical trials, we are at the doorstep of exploiting a hitherto underappreciated hallmark of cancer and promising target in the oncologist's strategy to combat cancer.

ChoK-ing the Pathogenic Bacteria: Potential of Human Choline Kinase Inhibitors as Antimicrobial Agents

Novel antimicrobial agents are crucial to combat antibiotic resistance in pathogenic bacteria. Choline kinase (ChoK) in bacteria catalyzes the synthesis of phosphorylcholine, which is subsequently incorporated into the cell wall or outer membrane. In certain species of bacteria, phosphorylcholine is also used to synthesize membrane phosphatidylcholine. Numerous human ChoK inhibitors (ChoKIs) have been synthesized and tested for anticancer properties. Inhibition of S. pneumoniae ChoK by human ChoKIs showed a promising effect by distorting the cell wall and retarded the growth of this pathogen. Comparison of amino acid sequences at the catalytic sites of putative choline kinases from pathogenic bacteria and human enzymes revealed striking sequence conservation that supports the potential application of currently available ChoKIs for inhibiting bacterial enzymes. We also propose the combined use of ChoKIs and nanoparticles for targeted delivery to the pathogen while shielding the human host from any possible side effects of the inhibitors. More research should focus on the verification of putative bacterial ChoK activities and the characterization of ChoKIs with active enzymes. In conclusion, the presence of ChoK in a wide range of pathogenic bacteria and the distinct function of this enzyme has made it an attractive drug target. This review highlighted the possibility of "choking" bacterial ChoKs by using human ChoKIs.

Choline Uptake and Metabolism Modulate Macrophage IL-1β and IL-18 Production

Choline is a vitamin-like nutrient that is taken up via specific transporters and metabolized by choline kinase, which converts it to phosphocholine needed for de novo synthesis of phosphatidylcholine (PC), the main phospholipid of cellular membranes. We found that Toll-like receptor (TLR) activation enhances choline uptake by macrophages and microglia through induction of the choline transporter CTL1. Inhibition of CTL1 expression or choline phosphorylation attenuated NLRP3 inflammasome activation and IL-1β and IL-18 production in stimulated macrophages. Mechanistically, reduced choline uptake altered mitochondrial lipid profile, attenuated mitochondrial ATP synthesis, and activated the energy sensor AMP-activated protein kinase (AMPK). By potentiating mitochondrial recruitment of DRP1, AMPK stimulates mitophagy, which contributes to termination of NLRP3 inflammasome activation. Correspondingly, choline kinase inhibitors ameliorated acute and chronic models of IL-1β-dependent inflammation.

Choline kinase inhibitors EB-3D and EB-3P interferes with lipid homeostasis in HepG2 cells

A full understanding of the molecular mechanism of action of choline kinase α (ChoKα) inhibitors at the cell level is essential for developing therapeutic and preventive approaches for cancer. The aim of the present study was to evaluate the effects of the ChoKα inhibitors EB-3D and EB-3P on lipid metabolism in HepG2 cells. We used [methyl-¹⁴C]choline, [1,2-¹⁴C]acetic acid and [2-³H]glycerol as exogenous precursors of the corresponding phospholipids and neutral lipids. [Methyl-¹⁴C]choline was also used to determine choline uptake. Protein levels were determined by Western blot. Ultrastructural alterations were investigated by transmission electron microscopy. In this work, we demonstrate that EB-3D and EB-3P interfere with phosphatidylcholine biosynthesis via both CDP-choline pathway and choline uptake by the cell. Moreover, the synthesis of both diacylglycerols and triacylglycerols was affected by cell exposure to both inhibitors. These effects were accompanied by a substantial decrease in cholesterol biosynthesis, as well as alterations in the expression of proteins related to cholesterol homeostasis. We also found that EB-3D and EB-3P lowered ChoKα protein levels. All these effects could be explained by the modulation of the AMP-activated protein kinase signalling pathway. We show that both inhibitors cause mitochondrial alteration and an endoplasmic reticulum stress response. EB-3D and EB-3P exert effects on ChoKα expression, AMPK activation, apoptosis, endoplasmic reticulum stress and lipid metabolism. Taken together, results show that EB-3D and EB-3P have potential anti-cancer activity through the deregulation of lipid metabolism.

A cell-based high-throughput screen identifies tyrphostin AG 879 as an inhibitor of animal cell phospholipid and fatty acid biosynthesis

Inhibition of animal cell phospholipid biosynthesis has been proposed for anticancer and antiviral therapies. Using CHO—K1 derived cell lines, we have developed and used a cell-based high-throughput procedure to screen a 1280 compound, small molecule library for inhibitors of phospholipid biosynthesis. We identified tyrphostin AG 879 (AG879), which inhibited phospholipid biosynthesis by 85–90% at a concentration of 10 μM, displaying an IC₅₀ of 1–3 μM. The synthesis of all phospholipid head group classes was heavily affected. Fatty acid biosynthesis was also dramatically inhibited (90%). AG879 inhibited phospholipid biosynthesis in all additional cell lines tested, including MDCK, HUH7, Vero, and HeLa cell lines. In CHO cells, AG879 was cytostatic; cells survived for at least four days during exposure and were able to divide following its removal. AG879 is an inhibitor of receptor tyrosine kinases (RTK) and inhibitors of signaling pathways known to be activated by RTK's also inhibited phospholipid biosynthesis. We speculate that inhibition of RTK by AG879 results in an inhibition of fatty acid biosynthesis with a resulting decrease in phospholipid biosynthesis and that AG879's effect on fatty acid synthesis and/or phospholipid biosynthesis may contribute to its known capacity as an effective antiviral/anticancer agent.

3D Growth of Cancer Cells Elicits Sensitivity to Kinase Inhibitors but Not Lipid Metabolism Modifiers

Tumor cells exhibit altered lipid metabolism compared with normal cells. Cell signaling kinases are important for regulating lipid synthesis and energy storage. How upstream kinases regulate lipid content, versus direct targeting of lipid-metabolizing enzymes, is currently unexplored. We evaluated intracellular lipid concentrations in prostate and breast tumor spheroids, treated with drugs directly inhibiting metabolic enzymes fatty acid synthase (FASN), acetyl-CoA carboxylase (ACC), diacylglyceride acyltransferase (DGAT), and pyruvate dehydrogenase kinase (PDHK), or cell signaling kinase enzymes PI3K, AKT, and mTOR with lipidomic analysis. We assessed whether baseline lipid profiles corresponded to inhibitors' effectiveness in modulating lipid profiles in three-dimensional (3D) growth and their relationship to therapeutic activity. Inhibitors against PI3K, AKT, and mTOR significantly inhibited MDA-MB-468 and PC3 cell growth in two-dimensional (2D) and 3D spheroid growth, while moderately altering lipid content. Conversely, metabolism inhibitors against FASN and DGAT altered lipid content most effectively, while only moderately inhibiting growth compared with kinase inhibitors. The FASN and ACC inhibitors' effectiveness in MDA-MB-468, versus PC3, suggested the former depended more on synthesis, whereas the latter may salvage lipids. Although baseline lipid profiles did not predict growth effects, lipid changes on therapy matched the growth effects of FASN and DGAT inhibitors. Several phospholipids, including phosphatidylcholine, were also upregulated following treatment, possibly via the Kennedy pathway. As this promotes tumor growth, combination studies should include drugs targeting it. Two-dimensional drug screening may miss important metabolism inhibitors or underestimate their potency. Clinical studies should consider serial measurements of tumor lipids to prove target modulation. Pretherapy tumor classification by de novo lipid synthesis versus uptake may help demonstrate efficacy.

Choline Kinase Alpha Inhibition by EB-3D Triggers Cellular Senescence, Reduces Tumor Growth and Metastatic Dissemination in Breast Cancer

Choline kinase (ChoK) is the first enzyme of the Kennedy pathway leading to the biosynthesis of phosphatidylcholine (PtdCho), the most abundant phospholipid in eukaryotic cell membranes. EB-3D is a novel choline kinase α1 (ChoKα1) inhibitor with potent antiproliferative activity against a panel of several cancer cell lines. ChoKα1 is particularly overexpressed and hyperactivated in aggressive breast cancer. By NMR analysis, we demonstrated that EB-3D is able to reduce the synthesis of phosphocholine, and using flow cytometry, immunoblotting, and q-RT-PCR as well as proliferation and invasion assays, we proved that EB-3D strongly impairs breast cancer cell proliferation, migration, and invasion. EB-3D induces senescence in breast cancer cell lines through the activation of the metabolic sensor AMPK and the subsequent dephosphorylation of mTORC1 downstream targets, such as p70S6K, S6 ribosomal protein, and 4E-BP1. Moreover, EB-3D strongly synergizes with drugs commonly used for breast cancer treatment. The antitumorigenic potential of EB-3D was evaluated in vivo in the syngeneic orthotopic E0771 mouse model of breast cancer, where it induces a significant reduction of the tumor mass at low doses. In addition, EB-3D showed an antimetastatic effect in experimental and spontaneous metastasis models. Altogether, our results indicate that EB-3D could be a promising new anticancer agent to improve aggressive breast cancer treatment protocols.

Lead optimization-hit expansion of new asymmetrical pyridinium/quinolinium compounds as choline kinase α1 inhibitors

AIM

Choline kinase α inhibitors represent one of the newest classes of cytotoxic drugs for cancer treatment, since aberrant choline metabolism is a characteristic shared by many human cancers.

RESULTS

Here, we present a new class of asymmetrical pyridinium/quinolinium derivatives developed and designed based on drug optimization.

CONCLUSION

Among all compounds described here, compound 8, bearing a 7-chloro-4N-methyl-p-chloroaniline quinolinium moiety, exhibited the greatest inhibitory activity at the enzyme (IC₅₀ = 0.29 μM) and antiproliferative activity in cellular assays (GI₅₀ = 0.29-0.92 μM). Specifically, compound 8 strongly induces a cell-cycle arrest in G1 phase, but it does not significantly induce apoptosis while causing senescence in the MDA-MB-231 cell line.

EB-3D a novel choline kinase inhibitor induces deregulation of the AMPK-mTOR pathway and apoptosis in leukemia T-cells

Choline kinase alpha 1 (ChoKα1) has recently become an interesting therapeutic target since its overexpression has been associated to tumorigenesis in many cancers. Nevertheless, little is known regarding hematological malignancies. In this manuscript, we investigated the effect of a novel and selective ChoKα inhibitor EB-3D in T acute lymphoblastic leukemia (T-ALL). The effect of EB-3D was evaluated in a panel of T-leukemia cell lines and ex-vivo primary cultures derived from pediatric T-ALL patients. We also evaluated in detail, using Reverse Phase Protein Array (RPPA), protein phosphorylation level changes in T-ALL cells upon treatment. The drug exhibits a potent antiproliferative activity in a panel of T-leukemia cell lines and primary cultures of pediatric patients. Moreover, the drug strongly induces apoptosis and more importantly it enhanced T-leukemia cell sensitivity to chemotherapeutic agents, such as dexamethasone and l-asparaginase. In addition, the compound induces an early activation of AMPK, the main regulator of cellular energy homeostasis, by its phosphorylation at residue T712 of catalytic subunit α, and thus repressing mTORC1 pathway, as shown by mTOR S2448 dephosphorylation. The inhibition of mTOR in turn affects the activity of several known downstream targets, such as 4E-BP1, p70S6K, S6 Ribosomal Protein and GSK3 that ultimately may lead to a reduction of protein synthesis and cell death. Taken together, our findings suggest that targeting ChoKα may be an interesting option for treating T-ALL and that EB-3D could represent a valuable therapeutic tool.

Patent Highlights February-March 2018

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research development.

Activation of choline kinase drives aberrant choline metabolism in esophageal squamous cell carcinomas

Esophageal squamous cell carcinoma (ESCC) is a major health threat worldwide. Research focused on molecular events associated with ESCC carcinogenesis for diagnosis, treatment and prevention is needed. Our goal is to discover novel biomarkers and investigate the underlying molecular mechanisms of ESCC progression by employing a global metabolomic approach. Sera from 34 ESCC patients and 32 age and sex matched healthy controls were profiled using two-dimensional liquid chromatography-mass spectrometry (2D LC-MS). We identified 120 differential metabolites in ESCC patient serums compared to healthy controls. Several amino acids, serine, arginine, lysine and histidine were significantly changed in ESCC patients. Most importantly, we found dysregulated lipid metabolism as an important characteristic in ESCC patients. Several free fat acids (FFA) and carnitines were found down-regulated in ESCC patients. Choline was significantly increased and phosphatidylcholines (PC) were significantly decreased in ESCC serum. The high expression of choline and low expression of total PC in patient serum were associated with the high expression of choline kinase (Chok) and activated Kennedy pathway in ESCC cells. Chok expression can serve as a significant biomarker for ESCC prognosis. In conclusion, metabolite profiles in the ESCC patient serum were significantly different from those in the healthy controls. Phosphatidylcholines and Chok, the key enzyme in the PC metabolism pathway, may serve as novel biomarkers for ESCC.

Overexpression of CHKA contributes to tumor progression and metastasis and predicts poor prognosis in colorectal carcinoma

Aberrant expression of choline kinase alpha (CHKA) has been reported in a variety of human malignancies including colorectal carcinoma (CRC). However, the role of CHKA in the progression and prognosis of CRC remains unknown. In this study, we found that CHKA was frequently upregulated in CRC clinical samples and CRC-derived cell lines and was significantly correlated with lymph node metastasis (p = 0.028), TNM stage (p = 0.009), disease recurrence (p = 0.004) and death (p < 0.001). Survival analyses indicated that patients with higher CHKA expression had a significantly shorter disease-free survival (DFS) and disease-specific survival (DSS) than those with lower CHKA expression. Multivariate analyses confirmed that increased CHKA expression was an independent unfavorable prognostic factor for CRC patients. In addition, combination of CHKA with TNM stage was a more powerful predictor of poor prognosis than either parameter alone. Functional study demonstrated that knockdown of CHKA expression profoundly suppressed the growth and metastasis of CRC cells both in vitro and in vivo. Mechanistic investigation revealed that EGFR/PI3K/AKT pathway was essential for mediating CHKA function. In conclusion, our results provide the first evidence that CHKA contributes to tumor progression and metastasis and may serve as a novel prognostic biomarker and potential therapeutic target in CRC.

Near infrared fluorescent imaging of choline kinase alpha expression and inhibition in breast tumors

Choline kinase alpha (ChoKα) overexpression is associated with an aggressive tumor phenotype. ChoKα inhibitors induce apoptosis in tumors, however validation of their specificity is difficult in vivo. We report the use of optical imaging to assess ChoKα status in cells and in vivo using JAS239, a carbocyanine-based ChoKα inhibitor with inherent near infrared fluorescence. JAS239 attenuated choline phosphorylation and viability in a panel of human breast cancer cell lines. Antibody blockade prevented cellular retention of JAS239 indicating direct interaction with ChoKα independent of the choline transporters and catabolic choline pathways. In mice bearing orthotopic MCF7 breast xenografts, optical imaging with JAS239 distinguished tumors overexpressing ChoKα from their empty vector counterparts and delineated tumor margins. Pharmacological inhibition of ChoK by the established inhibitor MN58b led to a growth inhibition in 4175-Luc+ tumors that was accompanied by concomitant reduction in JAS239 uptake and decreased total choline metabolite levels as measured using magnetic resonance spectroscopy. At higher therapeutic doses, JAS239 was as effective as MN58b at arresting tumor growth and inducing apoptosis in MDA-MB-231 tumors, significantly reducing tumor choline below baseline levels without observable systemic toxicity. These data introduce a new method to monitor therapeutically effective inhibitors of choline metabolism in breast cancer using a small molecule companion diagnostic.

Antitumoral activity of 1,2-diaminocyclohexane derivatives in breast, colon and skin human cancer cells

Aim: Cancer is among the leading causes of death worldwide. Medical interest has focused on macrocyclic polyamines because of their properties as antitumor agents. Results/Methodology: We have designed and synthesized a series of 1,2-diaminocyclohexane derivatives with notable in vitro antiproliferative activities against the MCF-7, HCT-116 and A375 cancer cell lines. Cell cycle and apoptosis analyses were also carried out. Our results show that all the compounds are potent cytotoxic agents, especially against the A375 cell line. Conclusion: The selective activity of the macrocyclic derivative against A375, via apoptosis, supposes a great advantage for future therapeutic use. This exemplifies the potential of 1,2-diaminocyclohexane derivatives to qualify as lead structures for future anticancer drug development due to their easy syntheses and noteworthy bioactivity.

Metabolic positron emission tomography imaging of cancer: Pairing lipid metabolism with glycolysis

The limitations of fluorine-18 fluorodeoxy-D-glucose (FDG) in detecting some cancers has prompted a longstanding search for other positron emission tomography (PET) tracers to complement the imaging of glycolysis in oncology, with much attention paid to lipogenesis based on observations that the production of various lipid and lipid-containing compounds is increased in most cancers. Radiolabeled analogs of choline and acetate have now been used as oncologic PET probes for over a decade, showing convincingly improved detection sensitivity over FDG for certain cancers. However, neither choline nor acetate have been thoroughly validated as lipogenic biomarkers, and while acetyl-CoA produced from acetate is used in de-novo lipogenesis to synthesize fatty acids, acetate is also consumed by various other synthetic and metabolic pathways, with recent experimental observations challenging the assumption that lipogenesis is its predominant role in all cancers. Since tumors detected by acetate PET are also frequently detected by choline PET, imaging of choline metabolism might serve as an alternative albeit indirect marker of lipogenesis, particularly if the fatty acids produced in cancer cells are mainly destined for membrane synthesis through incorporation into phosphatidylcholines. Aerobic glycolysis may or may not coincide with changes in lipid metabolism, resulting in combinatorial metabolic phenotypes that may have different prognostic or therapeutic implications. Consequently, PET imaging using dual metabolic tracers, in addition to being diagnostically superior to imaging with individual tracers, could eventually play a greater role in supporting precision medicine, as efforts to develop small-molecule metabolic pathway inhibitors are coming to fruition. To prepare for this advent, clinical and translational studies of metabolic PET tracers must go beyond simply estimating tracer diagnostic utility, and aim to uncover potential therapeutic avenues associated with these metabolic alterations.