Discovery of 2-((1H-benzo[d]imidazol-1-yl)methyl)-4H-pyrido[1,2-a]pyrimidin-4-ones as novel PKM2 activators

The M2 isoform of pyruvate kinase is an emerging target for antitumor therapy. In this letter, we describe the discovery of 2-((1H-benzo[d]imidazol-1-yl)methyl)-4H-pyrido[1,2-a]pyrimidin-4-ones as potent and selective PKM2 activators which were found to have a novel binding mode. The original lead identified from high throughput screening was optimized into an efficient series via computer-aided structure-based drug design. Both a representative compound from this series and an activator described in the literature were used as molecular tools to probe the biological effects of PKM2 activation on cancer cells. Our results suggested that PKM2 activation alone is not sufficient to alter cancer cell metabolism.     

Proviral Insertion in Murine Lymphomas 2 (PIM2) Oncogene Phosphorylates Pyruvate Kinase M2 (PKM2) and Promotes Glycolysis in Cancer Cells

Pyruvate kinase M2 (PKM2) is a key player in the Warburg effect of cancer cells. However, the mechanisms of regulating PKM2 are not fully elucidated. Here, we identified the protein-serine/threonine kinase PIM2, a known oncogene, as a novel binding partner of PKM2. The interaction between PIM2 and PKM2 was confirmed by multiple biochemical approaches in vitro and in cultured cells. Importantly, we found that PIM2 could directly phosphorylate PKM2 on the Thr-454 residue, resulting in an increase of PKM2 protein levels. Compared with wild type, PKM2 with the phosphorylation-defective mutation displayed a reduced effect on glycolysis, co-activating HIF-1α and β-catenin, and cell proliferation, while enhancing mitochondrial respiration of cancer cells. These findings demonstrate that PIM2-dependent phosphorylation of PKM2 is critical for regulating the Warburg effect in cancer, highlighting PIM2 as a potential therapeutic target.     

1-(sulfonyl)-5-(arylsulfonyl)indoline as activators of the tumor cell specific M2 isoform of pyruvate kinase

Cancer cells preferentially use glycolysis rather than oxidative phosphorylation for their rapid growth. They consume large amount of glucose to produce lactate even when oxygen is abundant, a phenomenon known as the Warburg effect. This metabolic change originates from a shift in the expression of alternative spliced isoforms of the glycolytic enzyme pyruvate kinase (PK), from PKM1 to PKM2. While PKM1 is constitutively active, PKM2 is switched from an inactive dimer form to an active tetramer form by small molecule activators. The prevalence of PKM2 in cancer cells relative to the prevalence of PKM1 in many normal cells, suggests a therapeutic strategy whereby activation of PKM2 may counter the abnormal cellular metabolism in cancer cells, and consequently decreased cellular proliferation. Herein we describe the discovery and optimization of a series of PKM2 activators derived from the 2-((2,3-dihydrobenzo[b][1,4] dioxin-6-yl)thio)-1-(2-methyl-1-(methylsulfonyl)indolin-5-yl) ethanone scaffold. The synthesis, SAR analysis, enzyme active site docking, enzymatic reaction kinetics, selectivity and pharmaceutical properties are discussed.     

Design and synthesis of novel 3-(benzo[d]oxazol-2-yl)-5-(1-(piperidin-4-yl)-1H-pyrazol-4-yl)pyridin-2-amine derivatives as selective G-protein-coupled receptor kinase-2 and -5 inhibitors

G-protein-coupled receptor kinase (GRK)-2 and -5 are emerging therapeutic targets for the treatment of cardiovascular disease. In our efforts to discover novel small molecules to inhibit GRK-2 and -5, a class of compound based on 3-(benzo[d]oxazol-2-yl)-5-(1-(piperidin-4-yl)-1H-pyrazol-4-yl)pyridin-2-amine was identified as a novel hit by high throughput screening campaign. Structural modification of parent benzoxazole scaffolds by introducing substituents on phenyl displayed potent inhibitory activities toward GRK-2 and -5.     

A Novel Pyruvate Kinase M2 Activator Compound that Suppresses Lung Cancer Cell Viability under Hypoxia

Pyruvate kinase M2 isoform (PKM2), a rate-limiting enzyme in the final step of glycolysis, is known to be associated with the metabolic rewiring of cancer cells, and considered an important cancer therapeutic target. Herein, we report a novel PKM2 activator, PA-12, which was identified via the molecular docking-based virtual screening. We demonstrate that PA-12 stimulates the pyruvate kinase activity of recombinant PKM2 in vitro, with a half-maximal activity concentration of 4.92 μM, and effectively suppresses both anchorage-dependent and -independent growth of lung cancer cells in non-essential amino acid-depleted medium. In addition, PA-12 blocked the nuclear translocalization of PKM2 in lung cancer cells, resulting in the inhibition of hypoxia response element (HRE)-mediated reporter activity as well as hypoxia-inducible factor 1 (HIF-1) target gene expression, eventually leading to the suppression of cell viability under hypoxia. We also verified that the effects of PA-12 were dependent on PKM2 expression in cancer cells, demonstrating the specificity of PA-12 for PKM2 protein. Taken together, our data suggest that PA-12 is a novel and potent PKM2 activator that has therapeutic implications for lung cancer.     

Translocalization of enhanced PKM2 protein into the nucleus induced by cancer upregulated gene 2 confers cancer stem cell-like phenotypes

Increased mRNA levels of cancer upregulated gene (CUG)2 have been detected in many different tumor tissues using Affymetrix microarray. Oncogenic capability of the CUG2 gene has been further reported. However, the mechanism by which CUG2 overexpression promotes cancer stem cell (CSC)-like phenotypes remains unknown. With recent studies showing that pyruvate kinase muscle 2 (PKM2) is overexpressed in clinical tissues from gastric, lung, and cervical cancer patients, we hypothesized that PKM2 might play an important role in CSC-like phenotypes caused by CUG2 overexpression. The present study revealed that PKM2 protein levels and translocation of PKM2 into the nucleus were enhanced in CUG2-overexpressing lung carcinoma A549 and immortalized bronchial BEAS-2B cells than in control cells. Ex-pression levels of c-Myc, CyclinD1, and PKM2 were increased in CUG2-overexpressing cells than in control cells. Furthermore, EGFR and ERK inhibitors as well as suppression of Yap1 and NEK2 expression reduced PKM2 protein levels. Interestingly, knockdown of β-catenin expression failed to reduce PKM2 protein levels. Furthermore, reduction of PKM2 expression with its siRNA hindered CSC-like phenotypes such as faster wound heal-ing, aggressive transwell migration, and increased size/number of sphere formation. The introduction of mutant S37A PKM2-green fluorescence protein (GFP) into cells without ability to move to the nucleus did not confer CSC-like phenotypes, whereas forced expression of wild-type PKM2 promoted such phenotypes. Overall, CUG2-induced increase in the expression of nuclear PKM2 contributes to CSC-like phenotypes by upregulating c-Myc and CyclinD1 as a co-activator.     

Protein Tyrosine Phosphatase 1B Regulates Pyruvate Kinase M2 Tyrosine Phosphorylation

Protein-tyrosine phosphatase 1B (PTP1B) is a physiological regulator of glucose homeostasis and adiposity and is a drug target for the treatment of obesity and diabetes. Here we identify pyruvate kinase M2 (PKM2) as a novel PTP1B substrate in adipocytes. PTP1B deficiency leads to increased PKM2 total tyrosine and Tyr¹⁰⁵ phosphorylation in cultured adipocytes and in vivo. Substrate trapping and mutagenesis studies identify PKM2 Tyr-105 and Tyr-148 as key sites that mediate PTP1B-PKM2 interaction. In addition, in vitro analyses illustrate a direct effect of Tyr-105 phosphorylation on PKM2 activity in adipocytes. Importantly, PTP1B pharmacological inhibition increased PKM2 Tyr-105 phosphorylation and decreased PKM2 activity. Moreover, PKM2 Tyr-105 phosphorylation is regulated nutritionally, decreasing in adipose tissue depots after high-fat feeding. Further, decreased PKM2 Tyr-105 phosphorylation correlates with the development of glucose intolerance and insulin resistance in rodents, non-human primates, and humans. Together, these findings identify PKM2 as a novel substrate of PTP1B and provide new insights into the regulation of adipose PKM2 activity.     

Parkin Regulates the Activity of Pyruvate Kinase M2

Parkin, a ubiquitin E3 ligase, is mutated in most cases of autosomal recessive early onset Parkinson disease. It was discovered that Parkin is also mutated in glioblastoma and other human malignancies and that it inhibits tumor cell growth. Here, we identified pyruvate kinase M2 (PKM2) as a unique substrate for parkin through biochemical purification. We found that parkin interacts with PKM2 both in vitro and in vivo, and this interaction dramatically increases during glucose starvation. Ubiquitylation of PKM2 by parkin does not affect its stability but decreases its enzymatic activity. Parkin regulates the glycolysis pathway and affects the cell metabolism. Our studies revealed the novel important roles of parkin in tumor cell metabolism and provided new insight for therapy of Parkinson disease.     

Identification of 4-(2-furanyl)pyrimidin-2-amines as Janus kinase 2 inhibitors

Janus kinases inhibitor is considered to have therapeutic potential for the treatment of oncology and immune-inflammatory diseases. Two series of 4-(2-benzofuranyl)pyrimidin-2-amine and 4-(4,5,6,7-tetrahydrofuro[3,2-c]pyridin-2-yl)pyrimidin-2-amine derivatives have been designed and synthesized. Primary SAR studies resulted in the discovery of a novel class of 4,5,6,7-tetrahydrofuro[3,2-c]pyridine based JAK2 inhibitors with higher potency (IC₅₀ of 0.7 nM) and selectivity (>30 fold) to JAK3 kinase than tofacitinib.     

miR-625-5p/PKM2 negatively regulates melanoma glycolysis state

PKM2 plays an important role in cancer glycolysis, however, the link of PKM2 and microRNAs (miRNAs) in melanoma is still unclear. The study will investigate the role of miRNAs in regulating PKM2 mediated melanoma cell glycolysis. We found that high PKM2 expression in melanoma tissues and cell lines was positively associated with glycolysis. Further study indicated that miR-625-5p regulated PKM2 expression on mRNA and protein levels in melanoma cells. There was a negative relationship between miR-625-5p and PKM2 expression in the clinical melanoma samples. These findings provide an evidence that miR-625-5p/PKM2 plays a role in melanoma cell glucose metabolism.     

Knockdown of pyruvate kinase type M2 suppresses tumor survival and invasion in osteosarcoma cells both in vitro and in vivo

Osteosarcoma (OS) is the mostly diagnosed primary bone malignancy. Emerging evidence indicates that the activity of pyruvate kinase M2 (PKM2) isoform is crucial for the survival of tumor cells. In the present study, the effect of PKM2 knockdown on the proliferation and migration of OS cells were assessed both in vitro and in vivo. Small hairpin RNA (shRNA) technology were employed to suppress the expression of PKM2 in MG-63 and Saos-2 cell lines. In vitro, shRNA-mediated knockdown of PKM2 efficiently inhibited cell proliferation, and induced G1 cell cycle arrest and apoptosis in both cell lines, which was associated with decreased expressions of cyclin D1 and Bcl-2 as well as increased expressions of Bax, cleaved-caspase-3, and cleaved-PARP. The invasion and migration potential of OS cell lines were also inhibited by PKM2 knockdown through the regulating effect of PKM2 on MMP-2 and VEGF signaling. In vivo, knockdown of PKM2 decelerated tumor growth rate and induced structure deterioration in tumor tissues. The current study for the first time showed that the activity of PKM2 was indispensable for the development and metastasis of OS, thereby providing the basic information for the future development of PKM2-based anti-OS therapies.     

(E)-2-(2-(2-hydroxyphenyl)hydrazono)-1-phenylbutane-1,3-dione: Tautomery and coordination to copper(II)

(E)-2-(2-(2-hydroxyphenyl)hydrazono)-1-phenylbutane-1,3-dione (H₂L) was synthesized by azocoupling of diazonium salt of 2-hydroxyaniline with 1-phenylbutane-1,3-dione and characterized by IR, ¹H and ¹³C NMR spectroscopies and X-ray diffraction analysis. In solution, H₂L exists as a mixture of the enol-azo and hydrazone tautomeric forms and a decrease of temperature and of solvent polarity shifts the tautomeric balance to the hydrazone form. In the solid state, H₂L crystallizes from ethanol-water in the monohydrate hydrazone form, as shown by X-ray analysis. The dissociation constants of H₂L (pK₁ = 5.98 ± 0.04, pK₂ = 9.72 ± 0.03) and the stability constants of its copper(II) complex (log β₁ = 11.01 ± 0.07, log β₂ = 20.19 ± 0.08) were determined by the potentiometric method in aqueous-ethanol solution. The copper(II) complex [Cu₂(μ-L)₂]_n was isolated in the solid state and found by X-rays to be a coordination polymer of a binuclear core with a distorted square pyramidal metal coordination geometry.     

Synthesis and evaluation of (E)-2-(acrylamido)cyclohex-1-enecarboxylic acid derivatives as HCA1, HCA2, and HCA3 receptor agonists

2-(3-(Naphthalen-2-yl)propanamido)cyclohex-1-enecarboxylic acid and its 6-hydroxynaphthalen-2-yl analogue are well-known hydroxyl-carboxylic acid (HCA) receptor HCA2 agonists. A series of novel aryl derivatives of 2-amidocyclohex-1-ene carboxylic acid that contained rigidity elements, such as an E-double bond, triple bond, and trans or cis-substituted cyclopropane rings, instead of the saturated ethane linker in the amide part of the molecules were designed and synthesized, and the derivatives’ potency for the activation of HCA1, HCA2, and HCA3 receptors by 3′–5′-cyclic adenosine monophosphate (cAMP) assay were evaluated. The SAR studies revealed that the rigidifying of appropriate molecules enabled modulation of the potency and selectivity of the HCA2 receptor activation.     

AKT2 contributes to increase ovarian cancer cell migration and invasion through the AKT2-PKM2-STAT3/NF-κB axis

Multiple studies have shown that protein kinase Bβ (AKT2) is involved in the development and progression of ovarian cancer, however, its precise role remains unclear. Here we explored the underlying molecular mechanisms how AKT2 promotes ovarian cancer progression. We examined the effects of AKT2 in vitro in two ovarian cancer cell lines (SKOV3 and HEY), and in vivo by metastasis assay in nude mice. The migration and invasion ability of SKOV3 and HEY cells was determined by transwell assay. Overexpression and knockdown (with shRNA) experiments were carried out to unravel the underlying signaling mechanisms induced by AKT2. Overexpression of AKT2 led to increased expression of pyruvate kinase (PKM2) in ovarian cancer cells and in lung metastatic foci from nude mice. Elevated AKT2/PKM2 expression induced cell migration and invasion in vitro, as well as lung metastasis in vivo; silencing AKT2 blocked these effects. Meanwhile, PKM2 overexpression was unable to increase AKT2 expression. The expressions of p-PI3K, p-AKT2, and PKM2 were increased when stimulated by epidermal growth factor (EGF); however, these expressions were blocked when inhibited the PI3K by LY294002. STAT3 expression was elevated and NF-κB p65 nuclear translocation was activated both in vitro and in vivo when either AKT2 or PKM2 was overexpressed; and these effects were inhibited when silencing AKT2 expression. Taken together, AKT2 increases the migration and invasion of ovarian cancer cells in vitro and promotes lung metastasis in nude mice in vivo through PKM2-mediated elevation of STAT3 expression and NF-κB activation. In conclusion, we highlight a novel mechanism of the AKT2-PKM2-STAT3/NF-κB axis in the regulation of ovarian cancer progression, and our work suggested that both AKT2 and PKM2 may be potential targets for the treatment of ovarian cancer.     

Quinoxalinone (Part II). Discovery of (Z)-3-(2-(pyridin-4-yl)vinyl)quinoxalinone derivates as potent VEGFR-2 kinase inhibitors

Inhibition of VEGFR-2 kinase has been highlighted as one of the well-defined strategies to suppress tumor growth via blockade of angiogenesis. Guided by the principles of bioisosteric replacement and pharmacophoric fragment migration, a series of novel quinoxalinone derivates were designed, synthesized and evaluated for their VEGFR-2 inhibitory potencies. Among them, compounds 7c, 8b, 8c, 8e and 10b displayed antiangiogenic abilities via the in vitro tube formation assay (cellular level) and ex vivo rat aortic ring assay (tissue level) at a low concentration (0.1 μM). By means of in vivo zebrafish embryo model, two (Z)-3-(2-(pyridin-4-yl)vinyl)quinoxalinone derivates 8c and 8e showed significant antiangiogenesis effects, suggesting they have potentials to be developed into antiangiogenesis agents via further structural optimization. Moreover, these two compounds also demonstrated potent inhibition toward VEGFR-2 and B-raf kinases in a low concentration (1 μM). A possible interpretation of our evaluation result has been presented by a molecular docking study by docking representative compound 8c with VEGFR-2.     

Lactylation of PKM2 Suppresses Inflammatory Metabolic Adaptation in Pro-inflammatory Macrophages

Emerging evidence suggests that metabolic adaptation is a vital hallmark and prerequisite for macrophage phenotype transition. Pyruvate kinase M2 (PKM2) is an essential molecular determinant of metabolic adaptions in pro-inflammatory macrophages. Post-translational modifications play a central role in the regulation of PKM2. However, doubt remains on whether lactylation in PKM2 exists and how lactylation modulates the function of PKM2. For the first time, our study reports that lactate inhibits the Warburg effect by activating PKM2, promoting the transition of pro-inflammatory macrophages towards a reparative phenotype. We identify PKM2 as a lactylation substrate and confirm that lactylation occurs mainly at the K62 site. We find that lactate increases the lactylation level of PKM2, which inhibits its tetramer-to-dimer transition, promoting its pyruvate kinase activity and reducing nuclear distribution. In short, our study reports a novel post-translational modification type in PKM2 and clarifies its potential role in regulating inflammatory metabolic adaptation in pro-inflammatory macrophages.     

Therapeutic effect of (Z)-3-(2,5-dimethoxyphenyl)-2-(4-methoxyphenyl) acrylonitrile (DMMA) against Staphylococcus aureus infection in a murine model

Sortase enzymes belong to a family of transpeptidases found in Gram-positive bacteria. Sortase is responsible for the reaction that anchors surface protein virulence factors to the peptidoglycan cell wall of the bacteria. The compound (Z)-3-(2,5-dimethoxyphenyl)-2-(4-methoxyphenyl) acrylonitrile (DMMA) has previously been reported as a novel sortase inhibitor in vitro, but the in vivo effects of DMMA have not been studied. Here, we evaluated the in vivo effects of DMMA against infection by wild-type and sortase A- and/or sortase B-deficient Staphylococcus aureus in Balb/c mice. With DMMA treatment, survival rates increased and kidney and joint infection rates decreased (p < 0.01) in a dose-dependent manner. The rate of kidney infection was significantly reduced in the mice treated with sortase A knock-out S. aureus (p < 0.01). These results indicate that by acting as a potent inhibitor of sortase A and moderate inhibitor of sortase B, DMMA can decrease kidney and joint infection rates and reduce mortality in mice infected with S. aureus. These findings suggest that DMMA is a promising therapeutic compound against Gram-positive bacteria.     

Switching of Pyruvate Kinase Isoform L to M2 Promotes Metabolic Reprogramming in Hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is an aggressive tumor, with a high mortality rate due to late symptom presentation and frequent tumor recurrences and metastasis. It is also a rapidly growing tumor supported by different metabolic mechanisms; nevertheless, the biological and molecular mechanisms involved in the metabolic reprogramming in HCC are unclear. In this study, we found that pyruvate kinase M2 (PKM2) was frequently over-expressed in human HCCs and its over-expression was associated with aggressive clinicopathological features and poor prognosis of HCC patients. Furthermore, knockdown of PKM2 suppressed aerobic glycolysis and cell proliferation in HCC cell lines in vitro. Importantly, knockdown of PKM2 hampered HCC growth in both subcutaneous injection and orthotopic liver implantation models, and reduced lung metastasis in vivo. Of significance, PKM2 over-expression in human HCCs was associated with a down-regulation of a liver-specific microRNA, miR-122. We further showed that miR-122 interacted with the 3UTR of the PKM2 gene. Re-expression of miR-122 in HCC cell lines reduced PKM2 expression, decreased glucose uptake in vitro, and suppressed HCC tumor growth in vivo. Our clinical data and functional studies have revealed a novel biological mechanism involved in HCC metabolic reprogramming.     

Inhibition of PKM2 sensitizes triple-negative breast cancer cells to doxorubicin

Cancer cells alter regular metabolic pathways in order to sustain rapid proliferation. One example of metabolic remodeling in cancerous tissue is the upregulation of pyruvate kinase isoenzyme M2 (PKM2), which is involved in aerobic glycolysis. Indeed, PKM2 has previously been identified as a tumor biomarker and as a potential target for cancer therapy. Here, we examined the effects of combined treatment with doxorubicin and anti-PKM2 small interfering RNA (siRNA) on triple-negative breast cancer (TNBC). The suppression of PKM2 resulted in changes in glucose metabolism, leading to decreased synthesis of adenosine triphosphate (ATP). Reduced levels of ATP resulted in the intracellular accumulation of doxorubicin, consequently enhancing the therapeutic efficacy of this drug in several triple-negative breast cancer cell lines. Furthermore, the combined effect of PKM2 siRNA and doxorubicin was evaluated in an in vivo MDA-MB-231 orthotopic breast cancer model. The siRNA was systemically administered through a polyethylenimine (PEI)-based delivery system that has been extensively used. We demonstrate that the combination treatment showed superior anticancer efficacy as compared to doxorubicin alone. These findings suggest that targeting PKM2 can increase the efficacy of chemotherapy, potentially providing a new approach for improving the outcome of chemotherapy in patients with TNBC.