JX06 Selectively Inhibits Pyruvate Dehydrogenase Kinase PDK1 by a Covalent Cysteine Modification

PDK1 promotes breast cancer progression by enhancing the stability and transcriptional activity of HIF-1α

Pyruvate dehydrogenase kinase 1 (PDK1) phosphorylates the pyruvate dehydrogenase complex, which inhibits its activity. Inhibiting pyruvate dehydrogenase complex inhibits the tricarboxylic acid cycle and the reprogramming of tumor cell metabolism to glycolysis, which plays an important role in tumor progression. This study aims to elucidate how PDK1 promotes breast cancer progression. We found that PDK1 was highly expressed in breast cancer tissues, and PDK1 knockdown reduced the proliferation, migration, and tumorigenicity of breast cancer cells and inhibited the HIF-1α (hypoxia-inducible factor 1α) pathway. Further investigation showed that PDK1 promoted the protein stability of HIF-1α by reducing the level of ubiquitination of HIF-1α. The HIF-1α protein levels were dependent on PDK1 kinase activity. Furthermore, HIF-1α phosphorylation at serine 451 was detected in wild-type breast cancer cells but not in PDK1 knockout breast cancer cells. The phosphorylation of HIF-1α at Ser 451 stabilized its protein levels by inhibiting the interaction of HIF-1α with von Hippel-Lindau and prolyl hydroxylase domain. We also found that PDK1 enhanced HIF-1α transcriptional activity. In summary, PDK1 enhances HIF-1α protein stability by phosphorylating HIF-1α at Ser451 and promotes HIF-1α transcriptional activity by enhancing the binding of HIF-1α to P300. PDK1 and HIF-1α form a positive feedback loop to promote breast cancer progression.

Hypoxic adaptation of mitochondria and its impact on tumor cell function

Mitochondria are the major sink for oxygen in the cell, consuming it during ATP production. Therefore, when environmental oxygen levels drop in the tumor, significant adaptation is required. Mitochondrial activity is also a major producer of biosynthetic precursors and a regulator of cellular oxidative and reductive balance. Because of the complex biochemistry, mitochondrial adaptation to hypoxia occurs through multiple mechanisms and has significant impact on other cellular processes such as macromolecule synthesis and gene regulation. In tumor hypoxia, mitochondria shift their location in the cell and accelerate the fission and quality control pathways. Hypoxic mitochondria also undergo significant changes to fundamental metabolic pathways of carbon metabolism and electron transport. These metabolic changes further impact the nuclear epigenome because mitochondrial metabolites are used as enzymatic substrates for modifying chromatin. This coordinated response delivers physiological flexibility and increased tumor cell robustness during the environmental stress of low oxygen.

Recent advances in pyruvate dehydrogenase kinase inhibitors: Structures, inhibitory mechanisms and biological activities

Metabolism is reprogrammed in a variety of cancer cells to ensure their rapid proliferation. Cancer cells prefer to utilize glycolysis to produce energy as well as to provide large amounts of precursors for their division. In this process, cancer cells inhibit the activity of pyruvate dehydrogenase complex (PDC) by upregulating the expression of pyruvate dehydrogenase kinases (PDKs). Inhibiting the activity of PDKs in cancer cells can effectively block this metabolic transition in cancer cells, while also activating mitochondrial oxidative metabolism and promoting apoptosis of cancer cells. To this day, the study of PDKs inhibitors has become one of the research hotspots in the field of medicinal chemistry. Novel structures targeting PDKs are constantly being discovered, and some inhibitors have entered the clinical research stage. Here, we reviewed the research progress of PDKs inhibitors in recent years and classified them according to the PDKs binding sites they acted on, aiming to summarize the structural characteristics of inhibitors acting on different binding sites and explore their clinical application value. Finally, the shortcomings of some PDKs inhibitors and the further development direction of PDKs inhibitors are discussed.

Targeting the pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis to discover potent PDK inhibitors through structure-based virtual screening and pharmacological evaluation

Proliferating cancer cells are characterized by the Warburg effect, a metabolic alteration in which ATP is generated from cytoplasmic glycolysis instead of oxidative phosphorylation. The pyruvate dehydrogenase complex/pyruvate dehydrogenase kinase (PDC/PDK) axis plays a crucial role in this effect and has been identified as a potential target for anticancer drug development. Herein, we present the discovery and pharmacological evaluation of potent PDK inhibitors targeting the PDK/PDC axis. We successfully identified 6 compounds from a small molecule library through a structure-based virtual screening campaign and evaluated their enzymatic inhibitory potencies for PDK1-4. Our results indicated that compound 1 exhibited submicromolar inhibitory activities against PDK1-3 (IC50 = 109.3, 135.8, and 458.7 nM, respectively), but is insensitive to PDK4 (IC50 = 8.67 μM). Furthermore, compound 1 inhibited the proliferation of A549 cells with an EC50 value of 10.7 μM. In addition, compound 1 induced cell apoptosis, arrested the cell cycle at the S phase, and reduced cell invasion and migration, while showing low in vivo toxicity at a high dose. Based on these observations, it can be concluded that compound 1 is a promising anti-PDK1-3 lead that merits further investigation.

FDCA Attenuates Neuroinflammation and Brain Injury after Cerebral Ischemic Stroke

Ischemic stroke is a deleterious cerebrovascular disease with few therapeutic options, and its functional recovery is highly associated with the integrity of the blood-brain barrier and neuroinflammation. The Rho-associated coiled-coil containing protein kinase (ROCK) inhibitor fasudil (F) and the pyruvate dehydrogenase kinase (PDK) inhibitor dichloroacetate (DCA) have been demonstrated to exhibit neuroprotection in a series of neurological disorders. Hence, we synthesized and biologically examined the new salt fasudil dichloroacetate (FDCA) and validated that FDCA was eligible for attenuating ischemic volume and neurological deficits in the rat transient middle cerebral artery occlusion (tMCAO) model. Additionally, FDCA exerted superior effects than fasudil and dichloroacetate alone or in combination in reducing cerebral ischemic injury. Particularly, FDCA could maintain the blood-brain barrier (BBB) integrity by inhibiting matrix metalloproteinase 9 (MMP-9) protein expression and the degradation of zonula occludens (ZO-1) and Occludin protein. Meanwhile, FDCA could mitigate the neuroinflammation induced by microglia. The in vivo and in vitro experiments further demonstrated that FDCA disrupted the phosphorylations of myosin phosphatase target subunit 1 (MYPT1), mitogen-activated protein kinase (MAPK) cascade, including p38 and c-Jun N-terminal kinase (JNK), and pyruvate dehydrogenase (PDH) and limited excessive lactic acid metabolites, resulting in inhibition of BBB disruption and neuroinflammation. In addition, FDCA potently mitigated inflammatory response in human monocytes isolated from ischemic stroke patients, which provides the possibilities of a clinical translation perspective. Overall, these findings provided a therapeutic potential for FDCA as a candidate agent for ischemic stroke and other neurological diseases associated with BBB disruption and neuroinflammation.

Pyruvate Dehydrogenase Kinase 1 inhibition mediated oxidative phosphorylation enhancement in cartilage promotes osteoarthritis progression

Osteoarthritis (OA) is a common disease characterized by cartilage degradation. Growing evidence showed that glucose metabolism impacts joint homeostasis and an imbalance between glycolysis and oxidative phosphorylation (OXPHOS) may exacerbate OA progression, however, a definitive link is yet to be established. Here, we report that pyruvate metabolism and oxidative phosphorylation pathway is enriched in OA cartilage through gene set enrichment analysis (GSEA) and expression of Pyruvate Dehydrogenase Kinase 1 (PDK1), an enzyme that can phosphorylate Pyruvate Dehydrogenase (PDH), and inhibit pyruvate fluxes into the tricarboxylic acid (TCA) cycle and to OXPHOS, in articular cartilage is notably reduced through destabilization of medial meniscus (DMM). Moreover, by inhibiting PDK1, cartilage loss is markedly accelerated in DMM-induced OA through extracellular matrix (ECM) degradation and apoptosis of chondrocytes. These results indicate that PDK1 is involved in the progression of OA through accelerating cartilage matrix degradation and synovium inflammation to ameliorate cartilage degeneration.

Drug repurposing of propafenone to discover novel anti-tumor agents by impairing homologous recombination to delay DNA damage recovery of rare disease conjunctival melanoma

Conjunctival melanoma (CM), a rare and fatal malignant ocular tumor, lacks proper diagnostic biomarkers and therapy. Herein, we revealed the novel application of propafenone, an FDA-approved antiarrhythmic medication, which was identified effective in inhibiting CM cells viability and homologous recombination pathway. Detailed structure-activity relationships generated D34 as one of the most promising derivatives, which strongly suppressed the proliferation, viability, and migration of CM cells at submicromolar concentrations. Mechanically, D34 had the potential to increase γ-H2AX nuclear foci and aggravated DNA damage by suppressing homologous recombination pathway and its factors, particularly the complex of MRE11-RAD50-NBS1. D34 bound to human recombinant MRE11 protein and inhibited its endonuclease activity. Moreover, D34 dihydrochloride significantly suppressed tumor growth in the CRMM1 NCG xenograft model without obvious toxicity. Our finding shows that propafenone derivatives modulating the MRE11-RAD50-NBS1 complex will most likely provide an approach for CM targeted therapy, especially for improving chemo- and radio-sensitivity for CM patients.

PKM2/PDK1 dual-targeted shikonin derivatives restore the sensitivity of EGFR-mutated NSCLC cells to gefitinib by remodeling glucose metabolism

Pyruvate kinase 2 (PKM2) and pyruvate dehydrogenase kinase 1 (PDK1) are two key enzymes in tumor glucose metabolism pathway that not only promote tumor growth and proliferation through accelerating aerobic glycolysis, but also contribute to drug resistance of non-small cell lung cancer (NSCLC). Considering that targeting PKM2 or PDK1 alone seems insufficient to remodel abnormal glucose metabolism to achieve significant antitumor activity, we proposed a "two-step approach" that regulates PKM2 and PDK1 synchronously. Firstly, we found that the combination of ML265 (PKM2 activator) and AZD7545 (PDK1 inhibitor) could synergistically inhibit proliferation and induce apoptosis in H1299 cells. Base on this, we designed a series of novel shikonin (SK) thioether derivatives as PKM2/PDK1 dual-target agents, among which the most potent compound E5 featuring a 2-methyl substitution on the benzene ring exerted significantly increased inhibitory activity toward EGFR mutant NSCLC cell H1975 (IC₅₀ = 1.51 μmol/L), which was 3 and 17-fold more active than the lead compound SK (IC₅₀ = 4.56 μmol/L) and the positive control gefitinib (IC₅₀ = 25.56 μmol/L), respectively. Additionally, E5 also showed good anti-tumor activity in xenografted mouse models, with significantly lower toxicity side effects than SK. Moreover, E5 also inhibited the entry of PKM2 into nucleus to regulate the transcriptional activation of oncogenes, thus restoring the sensitivity of H1975 cell to gefitinib. Collectively, these data demonstrate that E5, a dual inhibitor of PKM2/PDK1, may be a promising adjunct to gefitinib in the treatment of EGFR-TKIs resistant NSCLC, deserving further investigation.

Pyruvate dehydrogenase kinase supports macrophage NLRP3 inflammasome activation during acute inflammation

Activating the macrophage NLRP3 inflammasome can promote excessive inflammation with severe cell and tissue damage and organ dysfunction. Here, we show that pharmacological or genetic inhibition of pyruvate dehydrogenase kinase (PDHK) significantly attenuates NLRP3 inflammasome activation in murine and human macrophages and septic mice by lowering caspase-1 cleavage and interleukin-1β (IL-1β) secretion. Inhibiting PDHK reverses NLRP3 inflammasome-induced metabolic reprogramming, enhances autophagy, promotes mitochondrial fusion over fission, preserves crista ultrastructure, and attenuates mitochondrial reactive oxygen species (ROS) production. The suppressive effect of PDHK inhibition on the NLRP3 inflammasome is independent of its canonical role as a pyruvate dehydrogenase regulator. Our study suggestsa non-canonical role of mitochondrial PDHK in promoting mitochondrial stress and supporting NLRP3 inflammasome activation during acute inflammation.

Revisited Metabolic Control and Reprogramming Cancers by Means of the Warburg Effect in Tumor Cells

Aerobic glycolysis is an emerging hallmark of many human cancers, as cancer cells are defined as a “metabolically abnormal system”. Carbohydrates are metabolically reprogrammed by its metabolizing and catabolizing enzymes in such abnormal cancer cells. Normal cells acquire their energy from oxidative phosphorylation, while cancer cells acquire their energy from oxidative glycolysis, known as the “Warburg effect”. Energy–metabolic differences are easily found in the growth, invasion, immune escape and anti-tumor drug resistance of cancer cells. The glycolysis pathway is carried out in multiple enzymatic steps and yields two pyruvate molecules from one glucose (Glc) molecule by orchestral reaction of enzymes. Uncontrolled glycolysis or abnormally activated glycolysis is easily observed in the metabolism of cancer cells with enhanced levels of glycolytic proteins and enzymatic activities. In the “Warburg effect”, tumor cells utilize energy supplied from lactic acid-based fermentative glycolysis operated by glycolysis-specific enzymes of hexokinase (HK), keto-HK-A, Glc-6-phosphate isomerase, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase, phosphofructokinase (PFK), phosphor-Glc isomerase (PGI), fructose-bisphosphate aldolase, phosphoglycerate (PG) kinase (PGK)1, triose phosphate isomerase, PG mutase (PGAM), glyceraldehyde-3-phosphate dehydrogenase, enolase, pyruvate kinase isozyme type M2 (PKM2), pyruvate dehydrogenase (PDH), PDH kinase and lactate dehydrogenase. They are related to glycolytic flux. The key enzymes involved in glycolysis are directly linked to oncogenesis and drug resistance. Among the metabolic enzymes, PKM2, PGK1, HK, keto-HK-A and nucleoside diphosphate kinase also have protein kinase activities. Because glycolysis-generated energy is not enough, the cancer cell-favored glycolysis to produce low ATP level seems to be non-efficient for cancer growth and self-protection. Thus, the Warburg effect is still an attractive phenomenon to understand the metabolic glycolysis favored in cancer. If the basic properties of the Warburg effect, including genetic mutations and signaling shifts are considered, anti-cancer therapeutic targets can be raised. Specific therapeutics targeting metabolic enzymes in aerobic glycolysis and hypoxic microenvironments have been developed to kill tumor cells. The present review deals with the tumor-specific Warburg effect with the revisited viewpoint of recent progress.

Mannose ameliorates experimental colitis by protecting intestinal barrier integrity

Metabolite alteration has been associated with the pathogenesis of inflammatory bowel disease (IBD), including colitis. Mannose, a natural bioactive monosaccharide that is involved in metabolism and synthesis of glycoproteins, exhibits anti-inflammatory and anti-oxidative activities. We show here that the circulating level of mannose is increased in patients with IBD and mice with experimental colitis. Mannose treatment attenuates intestinal barrier damage in two mouse colitis models, dextran sodium sulfate (DSS)-induced colitis and spontaneous colitis in IL-10-deficient mice. We demonstrate that mannose treatment enhanced lysosomal integrity and limited the release of cathepsin B, preventing mitochondrial dysfunction and myosin light chain kinase (MLCK)-induced tight junction disruption in the context of intestinal epithelial damage. Mannose exerts a synergistic therapeutic effect with mesalamine on mouse colitis. Cumulatively, the results indicate that mannose supplementation may be an optional approach to the treatment of colitis and other diseases associated with intestinal barrier dysfunction.

Small-Molecule Thioesters as SARS-CoV-2 Main Protease Inhibitors: Enzyme Inhibition, Structure-Activity Relationships, Antiviral Activity, and X-ray Structure Determination

The main protease (Mpro, 3CLpro) of SARS-CoV-2 is an attractive target in coronaviruses because of its crucial involvement in viral replication and transcription. Here, we report on the design, synthesis, and structure-activity relationships of novel small-molecule thioesters as SARS-CoV-2 Mpro inhibitors. Compounds 3w and 3x exhibited excellent SARS-CoV-2 Mpro inhibition with kinac/Ki of 58,700 M-1 s-1 (Ki = 0.0141 μM) and 27,200 M-1 s-1 (Ki = 0.0332 μM), respectively. In Calu-3 and Vero76 cells, compounds 3h, 3i, 3l, 3r, 3v, 3w, and 3x displayed antiviral activity in the nanomolar range without host cell toxicity. Co-crystallization of 3w and 3af with SARS-CoV-2 Mpro was accomplished, and the X-ray structures showed covalent binding with the catalytic Cys145 residue of the protease. The potent SARS-CoV-2 Mpro inhibitors also inhibited the Mpro of other beta-coronaviruses, including SARS-CoV-1 and MERS-CoV, indicating that they might be useful to treat a broader range of coronaviral infections.

Discovery of Triple Inhibitors of Both SARS-CoV-2 Proteases and Human Cathepsin L

One inhibitor of the main SARS-CoV-2 protease has been approved recently by the FDA, yet it targets only SARS-CoV-2 main protease (Mpro). Here, we discovered inhibitors containing thiuram disulfide or dithiobis-(thioformate) tested against three key proteases involved in SARS-CoV-2 replication, including Mpro, SARS-CoV-2 papain-like protease (PLpro), and human cathepsin L. The use of thiuram disulfide and dithiobis-(thioformate) covalent inhibitor warheads was inspired by an idea to find a better alternative than disulfiram, an approved treatment for chronic alcoholism that is currently in phase 2 clinical trials against SARS-CoV-2. Our goal was to find more potent inhibitors that target both viral proteases and one essential human protease to reduce the dosage, improve the efficacy, and minimize the adverse effects associated with these agents. We found that compounds coded as RI175, RI173, and RI172 were the most potent inhibitors in an enzymatic assay against SARS-CoV-2 Mpro, SARS-CoV-2 PLpro, and human cathepsin L, with IC₅₀s of 300, 200, and 200 nM, which is about 5-, 19-, and 11-fold more potent than disulfiram, respectively. In addition, RI173 was tested against SARS-CoV-2 in a cell-based and toxicity assay and was shown to have a greater antiviral effect than disulfiram. The identified compounds demonstrated the promising potential of thiuram disulfide or dithiobis-(thioformate) as a reactive functional group in small molecules that could be further developed for treatment of the COVID-19 virus or related variants.

AKR1C1 promotes non-small cell lung cancer proliferation via crosstalk between HIF-1α and metabolic reprogramming

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AKR1C1 accelerates the proliferation of NSCLC cells.

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AKR1C1 remodels metabolism in NSCLC cells.

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HIF-1α may play a vital role in AKR1C1-mediated metabolic reprogramming.

Non-small cell lung cancer (NSCLC) ranks first among cancer death worldwide. Despite efficacy and safety priority, targeted therapy only benefits ∼30% patients, leading to the unchanged survival rates for whole NSCLC patients. Metabolic reprogramming occurs to offer energy and intermediates for fuelling cancer cells proliferation. Thus, mechanistic insights into metabolic reprogramming may shed light upon NSCLC proliferation and find new proper targets for NSCLC treatment. Herein, we used loss- and gain-of-function experiments to uncover that highly expressed aldo-keto reductase family1 member C1 (AKR1C1) accelerated NSCLC cells proliferation via metabolic reprogramming. Further molecular profiling analyses demonstrated that AKR1C1 augmented the expression of hypoxia-inducible factor 1-alpha (HIF-1α), which could drive tumour metabolic reprogramming. What's more, AKR1C1 significantly correlated with HIF-1α signaling, which predicted poor prognosis for NSCLC patients. Collectively, our data display that AKR1C1 reprograms tumour metabolism to promote NSCLC cells proliferation by activating HIF-1α. These newly acquired data not only establish the specific role for AKR1C1 in metabolic reprogramming, but also hint to the possibility that AKR1C1 may be a new therapeutic target for NSCLC treatment.

Cucurbitacin B-induced G2/M cell cycle arrest of conjunctival melanoma cells mediated by GRP78–FOXM1–KIF20A pathway

Conjunctival melanoma (CM) is a rare and fatal malignant eye tumor. In this study, we deciphered a novel anti-CM mechanism of a natural tetracyclic compound named as cucurbitacin B (CuB). We found that CuB remarkably inhibited the proliferation of CM cells including CM-AS16, CRMM1, CRMM2 and CM2005.1, without toxicity to normal cells. CuB can also induce CM cells G2/M cell cycle arrest. RNA-seq screening identified KIF20A, a key downstream effector of FOXM1 pathway, was abolished by CuB treatment. Further target identification by activity-based protein profiling chemoproteomic approach revealed that GRP78 is a potential target of CuB. Several lines of evidence demonstrated that CuB interacted with GRP78 and bound with a K_d value of 0.11 μmol/L. Furthermore, ATPase activity evaluation showed that CuB suppressed GRP78 both in human recombinant GRP78 protein and cellular lysates. Knockdown of the GRP78 gene significantly induced the downregulation of FOXM1 and related pathway proteins including KIF20A, underlying an interesting therapeutic perspective. Finally, CuB significantly inhibited tumor progression in NCG mice without causing obvious side effects in vivo. Taken together, our current work proved that GRP78–FOXM1–KIF20A as a promising pathway for CM therapy, and the traditional medicine CuB as a candidate drug to hinder this pathway.

Targeting Cancer Metabolism Plasticity with JX06 Nanoparticles via Inhibiting PDK1 Combined with Metformin for Endometrial Cancer Patients with Diabetes

Diabetes is closely related to the occurrence of endometrial cancer (EC) and its poor prognosis. However, there is no effective clinical treatment for EC patients with diabetes (patient^EC+/dia+ ). To explore new therapeutic targets, Ishikawa is cultured with high glucose (Ishikawa^HG ) mimicking hyperglycemia in patient^EC+/dia+ . Subsequently, it is discovered that Ishikawa^HG exhibits glucose metabolic reprogramming characterized by increased glycolysis and decreased oxidative phosphorylation. Further, pyruvate dehydrogenase kinase 1 (PDK1) is identified to promote glycolysis of Ishikawa^HG by proteomics. Most importantly, JX06, a novel PDK1 inhibitor combined metformin (Met) significantly inhibits Ishikawa^HG proliferation though Ishikawa^HG is resistant to Met. Furthermore, a reduction-sensitive biodegradable polymer is adopted to encapsulate JX06 to form nanoparticles (JX06-NPs) for drug delivery. It is found that in vitro JX06-NPs have better inhibitory effect on the growth of Ishikawa^HG as well as patient-derived EC cells (PDC) than JX06. Additionally, it is found that JX06-NPs can accumulate to the tumor of EC-bearing mouse with diabetes (mice^EC+/dia+ ) after intravenous injection, and JX06-NPs combined Met can significantly inhibit tumor growth of mice^EC+/dia+ . Taken together, the study demonstrates that the combination of JX06-NPs and Met can target the cancer metabolism plasticity, which significantly inhibits the growth of EC, thereby provides a new adjuvant therapy for patients^EC+/dia+ .

A novel PDK1 inhibitor, JX06, inhibits glycolysis and induces apoptosis in multiple myeloma cells

Pyruvate dehydrogenase kinase 1 (PDK1) is a Ser/Thr kinase that inactivates mitochondrial pyruvate dehydrogenase (PDH), leading to switch of glucose metabolism from mitochondrial oxidation to aerobic glycolysis. We previously reported that PDK1 inhibition is a potent therapeutic strategy in multiple myeloma (MM). However, availability of PDK1 inhibitors, which are effective at low concentrations, are limited at present, making PDK1 inhibition difficult to apply in the clinic. In the present study, we examined the efficacy and mechanism of action of JX06, a novel PDK1 inhibitor, against MM cells. We confirmed that PDK1 is highly expressed in normal plasma cells and MM cells using publicly available gene expression datasets. JX06 suppressed cell growth and induced apoptosis against MM cells from approximately 0.5 μM JX06 treatment reduced PDH phosphorylation, suggesting that JX06 is indeed inhibiting PDK1. Intracellular metabolite analysis revealed that JX06 treatment reduced metabolites associated with glucose metabolism of MM cells. Additionally, JX06 in combination with a well-known proteasome inhibitor, bortezomib, significantly increased MM cell death, which raises the possibility of combination use of JX06 with proteasome inhibitors in the clinic. These findings demonstrate that PDK1 can be potentially targeted by JX06 in MM through glycolysis inhibition, leading to a novel therapeutic strategy in MM.

Drug evaluation based on phosphomimetic PDHA1 reveals the complexity of activity-related cell death in A549 non-small cell lung cancer cells

Cancer cells predominantly generate energy via glycolysis, even in the presence of oxygen, to support abnormal cell proliferation. Suppression of PDHA1 by PDK1 prevents the conversion of cytoplasmic pyruvate into Acetyl-CoA. Several PDK inhibitors have been identified, but their clinical applications have not been successful for unclear reasons. In this study, endogenous PDHA1 in A549 cells was silenced by the CRISPR/Cas9 system, and PDHA1^WT and PDHA1^3SD were transduced. Since PDHA1^3SD cannot be phosphorylated by PDKs, it was used to evaluate the specific activity of PDK inhibitors. This study highlights that PDHA1^WT and PDHA1^3SD A549 cells can be used as a cell-based PDK inhibitor-distinction system to examine the relationship between PDH activity and cell death by established PDK inhibitors. Leelamine, huzhangoside A and otobaphenol induced PDH activity-dependent apoptosis, whereas AZD7545, VER-246608 and DCA effectively enhanced PDHA1 activity but little toxic to cancer cells. Furthermore, the activity of phosphomimetic PDHA1 revealed the complexity of its regulation, which requires further in-depth investigation.

α-Lipoic Acid Targeting PDK1/NRF2 Axis Contributes to the Apoptosis Effect of Lung Cancer Cells

As an antioxidant, α-lipoic acid (LA) has attracted much attention to cancer research. However, the exact mechanism of LA in cancer progression control and prevention remains to be unclear. In this study, we demonstrated that α-lipoic acid has inhibitory effects on the proliferation, migration, and proapoptotic effects of non-small-cell lung cancer (NSCLC) cell lines A549 and PC9. LA-induced NSCLC cell apoptosis was mediated by elevated mitochondrial reactive oxygen species (ROS). Further study confirmed that it is by downregulating the expression of PDK1 (the PDH kinase), resulted in less phospho-PDH phenotype which could interact with Keap1, the negative controller of NRF2, directly leading to NRF2 decrease. Thus, by downregulating the NRF2 antioxidant system, LA plays a role in promoting apoptosis through the ROS signaling pathway. Moreover, LA could enhance other PDK inhibitors with the proapoptosis effect. In summary, our study shows that LA promotes apoptosis and exerts its antitumor activity against lung cancer by regulating mitochondrial energy metabolism enzyme-related antioxidative stress system. Administration of LA to the tumor-bearing animal model further supported the antitumor effect of LA. These findings provided new ideas for the clinical application of LA in the field of cancer therapy.

Targeting pyruvate dehydrogenase kinase signaling in the development of effective cancer therapy

Pyruvate is irreversibly decarboxylated to acetyl coenzyme A by mitochondrial pyruvate dehydrogenase complex (PDC). Decarboxylation of pyruvate is considered a crucial step in cell metabolism and energetics. The cancer cells prefer aerobic glycolysis rather than mitochondrial oxidation of pyruvate. This attribute of cancer cells allows them to sustain under indefinite proliferation and growth. Pyruvate dehydrogenase kinases (PDKs) play critical roles in many diseases because they regulate PDC activity. Recent findings suggest an altered metabolism of cancer cells is associated with impaired mitochondrial function due to PDC inhibition. PDKs inhibit the PDC activity via phosphorylation of the E1a subunit and subsequently cause a glycolytic shift. Thus, inhibition of PDK is an attractive strategy in anticancer therapy. This review highlights that PDC/PDK axis could be implicated in cancer's therapeutic management by developing potential small-molecule PDK inhibitors. In recent years, a dramatic increase in the targeting of the PDC/PDK axis for cancer treatment gained an attention from the scientific community. We further discuss breakthrough findings in the PDC-PDK axis. In addition, structural features, functional significance, mechanism of activation, involvement in various human pathologies, and expression of different forms of PDKs (PDK1-4) in different types of cancers are discussed in detail. We further emphasized the gene expression profiling of PDKs in cancer patients to prognosis and therapeutic manifestations. Additionally, inhibition of the PDK/PDC axis by small molecule inhibitors and natural compounds at different clinical evaluation stages has also been discussed comprehensively.

Pyruvate dehydrogenase kinases (PDKs): an overview toward clinical applications

Pyruvate dehydrogenase kinase (PDK) can regulate the catalytic activity of pyruvate decarboxylation oxidation via the mitochondrial pyruvate dehydrogenase complex, and it further links glycolysis with the tricarboxylic acid cycle and ATP generation. This review seeks to elucidate the regulation of PDK activity in different species, mainly mammals, and the role of PDK inhibitors in preventing increased blood glucose, reducing injury caused by myocardial ischemia, and inducing apoptosis of tumor cells. Regulations of PDKs expression or activity represent a very promising approach for treatment of metabolic diseases including diabetes, heart failure, and cancer. The future research and development could be more focused on the biochemical understanding of the diseases, which would help understand the cellular energy metabolism and its regulation by pharmacological effectors of PDKs.

Synthesis, biological evaluation and structure-activity relationship of novel dichloroacetophenones targeting pyruvate dehydrogenase kinases with potent anticancer activity

Pyruvate dehydrogenase kinases (PDKs) are promising therapeutic targets that have received increasing attentions in cancer metabolism. In this paper, we report the synthesis and biological evaluation of a series of novel dichloroacetophenones as potent PDKs inhibitors. Structure-activity relationship analysis enabled us to identify a potent compound 6u, which inhibited PDKs with an EC₅₀ value of 0.09 μM, and reduced various cancer cells proliferation with IC₅₀ values ranging from 1.1 to 3.8 μM, while show weak effect against non-cancerous L02 cell (IC₅₀ > 10 μM). In the A375 xenograft model, 6u displayed an obvious antitumor activity at a dose of 5 mg/kg, but with no negative effect to the mice weight. Molecular docking suggested that 6u formed direct hydrogen bond interactions with Ser75 and Gln61 in PDK1, and meanwhile the aniline skeleton in 6u was sandwiched by the conserved hydrophobic residues Phe78 and Phe65, which contribute to the biochemical activity improvement. Moreover, 6u induced A375 cell apoptosis and cell arrest in G1 phase, and inhibited cancer cell migration. In addition, 6u altered glucose metabolic pathway in A375 cell by decreasing lactate formation and increasing ROS production and OCR consumption, which could serve as a potential modulator to reprogram the glycolysis pathway in cancer cell.

Hemistepsin A suppresses colorectal cancer growth through inhibiting pyruvate dehydrogenase kinase activity

Most cancer cells primarily produce their energy through a high rate of glycolysis followed by lactic acid fermentation even in the presence of abundant oxygen. Pyruvate dehydrogenase kinase (PDK) 1, an enzyme responsible for aerobic glycolysis via phosphorylating and inactivating pyruvate dehydrogenase (PDH) complex, is commonly overexpressed in tumors and recognized as a therapeutic target in colorectal cancer. Hemistepsin A (HsA) is a sesquiterpene lactone isolated from Hemistepta lyrata Bunge (Compositae). Here, we report that HsA is a PDK1 inhibitor can reduce the growth of colorectal cancer and consequent activation of mitochondrial ROS-dependent apoptotic pathway both in vivo and in vitro. Computational simulation and biochemical assays showed that HsA directly binds to the lipoamide-binding site of PDK1, and subsequently inhibits the interaction of PDK1 with the E2 subunit of PDH complex. As a result of PDK1 inhibition, lactate production was decreased, but oxygen consumption was increased. Mitochondrial ROS levels and mitochondrial damage were also increased. Consistent with these observations, the apoptosis of colorectal cancer cells was promoted by HsA with enhanced activation of caspase-3 and -9. These results suggested that HsA might be a potential candidate for developing a novel anti-cancer drug through suppressing cancer metabolism.

An insight into medicinal attributes of dithiocarbamates: Bird's eye view

Dithiocarbamates are considered as an important motif owing to its extensive biological applications in medicinal chemistry. The synthesis of this framework can easily be achieved via a one-pot reaction of primary/secondary amines, CS₂, and alkyl halides under catalyst-free conditions or sometimes in the presence of a base. By virtue of its colossal pharmacological scope, it has been an evolving subject of interest for many researchers around the world. The present review aims to highlight various synthetic approaches for dithiocarbamates with the major emphasis on medicinal attributes of these architectures as leads in the drug discovery of small molecules such as HDAC inhibitor, lysine-specific demethylase 1 (LSD1) down-regulator, kinase inhibitor (focal adhesion kinase, pyruvate kinase, Bruton's tyrosine kinase), carbonic anhydrase inhibitor, DNA intercalators, and apoptosis-inducing agents. Moreover, recent medicinal advancements in the synthesis of dithiocarbamate derivatives as anticancer, antifungal, antibacterial, anti-Alzheimer, antitubercular, anti-glaucoma, anti-cholinergic, antihyperglycemic, anti-inflammatory activities have been elaborated with notable examples.

Ilimaquinone Induces the Apoptotic Cell Death of Cancer Cells by Reducing Pyruvate Dehydrogenase Kinase 1 Activity

In cancer cells, aerobic glycolysis rather than oxidative phosphorylation (OxPhos) is generally preferred for the production of ATP. In many cancers, highly expressed pyruvate dehydrogenase kinase 1 (PDK1) reduces the activity of pyruvate dehydrogenase (PDH) by inducing the phosphorylation of its E1α subunit (PDHA1) and subsequently, shifts the energy metabolism from OxPhos to aerobic glycolysis. Thus, PDK1 has been regarded as a target for anticancer treatment. Here, we report that ilimaquinone (IQ), a sesquiterpene quinone isolated from the marine sponge Smenospongia cerebriformis, might be a novel PDK1 inhibitor. IQ decreased the cell viability of human and murine cancer cells, such as A549, DLD-1, RKO, and LLC cells. The phosphorylation of PDHA1, the substrate of PDK1, was reduced by IQ in the A549 cells. IQ decreased the levels of secretory lactate and increased oxygen consumption. The anticancer effect of IQ was markedly reduced in PDHA1-knockout cells. Computational simulation and biochemical assay revealed that IQ interfered with the ATP binding pocket of PDK1 without affecting the interaction of PDK1 and the E2 subunit of the PDH complex. In addition, similar to other pyruvate dehydrogenase kinase inhibitors, IQ induced the generation of mitochondrial reactive oxygen species (ROS) and depolarized the mitochondrial membrane potential in the A549 cells. The apoptotic cell death induced by IQ treatment was rescued in the presence of MitoTEMPO, a mitochondrial ROS inhibitor. In conclusion, we suggest that IQ might be a novel candidate for anticancer therapeutics that act via the inhibition of PDK1 activity.

Development of disulfide-derived fructose-1,6-bisphosphatase (FBPase) covalent inhibitors for the treatment of type 2 diabetes

Fructose-1,6-bisphosphatase (FBPase), as a key rate-limiting enzyme in the gluconeogenesis (GNG) pathway, represents a practical therapeutic strategy for type 2 diabetes (T2D). Our previous work first identified cysteine residue 128 (C128) was an important allosteric site in the structure of FBPase, while pharmacologically targeting C128 attenuated the catalytic ability of FBPase. Herein, ten approved cysteine covalent drugs were selected for exploring FBPase inhibitory activities, and the alcohol deterrent disulfiram displayed superior inhibitory efficacy among those drugs. Based on the structure of lead compound disulfiram, 58 disulfide-derived compounds were designed and synthesized for investigating FBPase inhibitory activities. Optimal compound 3a exhibited significant FBPase inhibition and glucose-lowering efficacy in vitro and in vivo. Furthermore, 3a covalently modified the C128 site, and then regulated the N125-S124-S123 allosteric pathway of FBPase in mechanism. In summary, 3a has the potential to be a novel FBPase inhibitor for T2D therapy.

Inhibition of pyruvate dehydrogenase kinase‑1 by dicoumarol enhances the sensitivity of hepatocellular carcinoma cells to oxaliplatin via metabolic reprogramming

The Warburg effect is a unique metabolic feature of the majority of tumor cells and is closely related to chemotherapeutic resistance. Pyruvate dehydrogenase kinase 1 (PDK1) is considered a 'switch' that controls the fate of pyruvate in glucose metabolism. However, to date, to the best of our knowledge, there are only a few studies to available which had studied the reduction of chemotherapeutic resistance via the metabolic reprogramming of tumor cells with PDK1 as a target. In the present study, it was found dicoumarol (DIC) reduced the phosphorylation of pyruvate dehydrogenase (PDH) by inhibiting the activity of PDK1, which converted the metabolism of human hepatocellular carcinoma (HCC) cells to oxidative phosphorylation, leading to an increase in mitochondrial reactive oxygen species ROS (mtROS) and a decrease in mitochondrial membrane potential (MMP), thereby increasing the apoptosis induced by oxaliplatin (OXA). Furthermore, the present study elucidated that the targeting of PDK1 may be a potential strategy for targeting metabolism in the chemotherapy of HCC. In addition, DIC as an 'old drug' exhibits novel efficacy, bringing new hope for antitumor therapy.

Repurposing of antipsychotics perphenazine for the treatment of endometrial cancer

Endometrial cancer (EC) is one of the most common and fatal gynecological cancers worldwide, but there is no effective treatment for the EC patients of progesterone resistance. Repurposing of existing drugs is a good strategy to discover new candidate drugs. In this text, perphenazine (PPZ), approved for psychosis therapy, was identified as a potential agent for the treatment of both progesterone sensitive and resistant endometrial cancer for the first time. Specifically, perphenazine exhibited good cell proliferation inhibition in Ishikawa (ISK) and KLE cell lines according to the CCK-8 assay and colony formation assay. It also reduced the cell migration of ISK and KLE cell lines in the light of the transwell migration assay. Annexin-V/PI double staining assay suggested that perphenazine could effectively induce ISK and KLE cell apoptosis. Moreover, results of western blot assay indicated perphenazine obviously inhibited the phosphorylation of Akt. Delightedly, PPZ also could significantly attenuate xenograft tumor growth at both 3 mg/kg and 15 mg/kg in mice without influencing the body weights.

Advances in covalent kinase inhibitors

This comprehensive review details recent advances, challenges and innovations in covalent kinase inhibition within a 10 year period (2007–2018).

Increased pyruvate dehydrogenase activity in skeletal muscle of growth-restricted ovine fetuses

Fetal sheep with placental insufficiency-induced intrauterine growth restriction (IUGR) have lower fractional rates of glucose oxidation and greater gluconeogenesis, indicating lactate shuttling between skeletal muscle and liver. Suppression of pyruvate dehydrogenase (PDH) activity was proposed because of greater pyruvate dehydrogenase kinase (PDK) 4 and PDK1 mRNA concentrations in IUGR muscle. Although PDK1 and PDK4 inhibit PDH activity to reduce pyruvate metabolism, PDH protein concentrations and activity have not been examined in skeletal muscle from IUGR fetuses. Therefore, we evaluated the protein concentrations and activity of PDH and the kinases and phosphatases that regulate PDH phosphorylation status in the semitendinosus muscle from placenta insufficiency-induced IUGR sheep fetuses and control fetuses. Immunoblots were performed for PDH, phosphorylated PDH (E1α), PDK1, PDK4, and pyruvate dehydrogenase phosphatase 1 and 2 (PDP1 and PDP2, respectively). Additionally, the PDH, lactate dehydrogenase (LDH), and citrate synthase (CS) enzymatic activities were measured. Phosphorylated PDH concentrations were 28% lower (P < 0.01) and PDH activity was 67% greater (P < 0.01) in IUGR fetal muscle compared with control. PDK1, PDK4, PDP1, PDP2, and PDH concentrations were not different between groups. CS and LDH activities were also unaffected. Contrary to the previous speculation, PDH activity was greater in skeletal muscle from IUGR fetuses, which parallels lower phosphorylated PDH. Therefore, greater expression of PDK1 and PDK4 mRNA did not translate to greater PDK1 or PDK4 protein concentrations or inhibition of PDH as proposed. Instead, these findings show greater PDH activity in IUGR fetal muscle, which indicates that alternative regulatory mechanisms are responsible for lower pyruvate catabolism.

Targeting virulence factors as an antimicrobial approach: Pigment inhibitors

The fascinating and dangerous colored pathogens contain unique chemically pigmented molecules, which give varied and efficient assistance as virulence factors to the crucial reproduction and growth of microbes. Therefore, multiple novel strategies and inhibitors have been developed in recent years that target virulence factor pigments. However, despite the importance and significance of this topic, it has not yet been comprehensively reviewed. Moreover, research groups around the world have made successful progress against antibacterial infections by targeting pigment production, including our serial works on the discovery of CrtN inhibitors against staphyloxanthin production in Staphylococcus aureus. On the basis of the previous achievements and recent progress of our group in this field, this article will be the first comprehensive review of pigment inhibitors against colored pathogens, especially S. aureus infections, and this article includes design strategies, representative case studies, advantages, limitations, and perspectives to guide future research.

Huzhangoside A Suppresses Tumor Growth through Inhibition of Pyruvate Dehydrogenase Kinase Activity

Aerobic glycolysis is one of the important metabolic characteristics of many malignant tumors. Pyruvate dehydrogenase kinase (PDHK) plays a key role in aerobic glycolysis by phosphorylating the E1α subunit of pyruvate dehydrogenase (PDH). Hence, PDHK has been recognized as a molecular target for cancer treatment. Here, we report that huzhangoside A (Hu.A), a triterpenoid glycoside compound isolated from several plants of the Anemone genus, acts as a novel PDHK inhibitor. Hu.A was found to decrease the cell viability of human breast cancer MDA-MB-231, hepatocellular carcinoma Hep3B, colon cancer HT-29, DLD-1, and murine lewis lung carcinoma LLC cell lines. The activity of PDHK1 was decreased by Hu.A in both in vitro assays and in vivo assays in DLD-1 cells. Hu.A significantly increased the oxygen consumption and decreased the secretory lactate levels in DLD-1 cells. In addition, Hu.A interacted with the ATP-binding pocket of PDHK1 without affecting the interaction of PDHK1 and pyruvate dehydrogenase complex (PDC) subunits. Furthermore, Hu.A significantly induced mitochondrial reactive oxygen species (ROS) and depolarized the mitochondrial membrane potential in DLD-1 cells. Consistently, when Hu.A was intraperitoneally injected into LLC allograft mice, the tumor growth was significantly decreased. In conclusion, Hu.A suppressed the growth of tumors in both in vitro and in vivo models via inhibition of PDHK activity.

The roles of glucose metabolic reprogramming in chemo- and radio-resistance

Reprogramming of cancer metabolism is a newly recognized hallmark of malignancy. The aberrant glucose metabolism is associated with dramatically increased bioenergetics, biosynthetic, and redox demands, which is vital to maintain rapid cell proliferation, tumor progression, and resistance to chemotherapy and radiation. When the glucose metabolism of cancer is rewiring, the characters of cancer will also occur corresponding changes to regulate the chemo- and radio-resistance of cancer. The procedure is involved in the alteration of many activities, such as the aberrant DNA repairing, enhanced autophagy, oxygen-deficient environment, and increasing exosomes secretions, etc. Targeting altered metabolic pathways related with the glucose metabolism has become a promising anti-cancer strategy. This review summarizes recent progress in our understanding of glucose metabolism in chemo- and radio-resistance malignancy, and highlights potential molecular targets and their inhibitors for cancer treatment.

New Electrophiles and Strategies for Mechanism-Based and Targeted Covalent Inhibitor Design

Covalent inhibitors are experiencing a growing resurgence in drug design and are an increasingly useful tool in molecular biology. The ability to attach inhibitors to their targets by a covalent linkage offers pharmacodynamic and pharmacokinetic advantages, but this can also be a liability if undesired off-target reactions are not mitigated. The discovery of new electrophilic groups that react selectively with specific amino acid residues is therefore highly desirable in the design of targeted covalent inhibitors (TCIs). Additionally, the ability to control the reactivity through exploitation of the target enzyme's machinery, as in mechanism-based inhibitors (MBIs), greatly benefits from the discovery of new strategies. This Perspective showcases recent advances in electrophile development and their application in TCIs and MBIs, exhibiting high selectivity for their targets.

Penicisulfuranol A, a novel C-terminal inhibitor disrupting molecular chaperone function of Hsp90 independent of ATP binding domain

The goal of this study is to explore the mechanism of a heat shock protein 90 (Hsp90) C-terminal inhibitor, Penicisulfuranol A (PEN-A), for cancer therapy. PEN-A was produced by a mangrove endophytic fungus Penicillium janthinellum and had a new structure with a rare 3H-spiro [benzofuran-2, 2'-piperazine] ring system. PEN-A caused depletion of multiple Hsp90 client proteins without induction of heat shock protein 70 (Hsp70). Subsequently, it induced apoptosis and inhibited xerograph tumor growth of HCT116 cells in vitro and in vivo. Mechanism studies showed that PEN-A was bound to C-terminus of Hsp90 at the binding site different from ATP binding domain. Therefore, it inhibited dimerization of Hsp90 C-terminus, depolymerization of ADH protein by C-terminus of Hsp90, and interaction of co-chaperones with Hsp90. These inhibitory effects of PEN-A were similar to those of novobiocin, an inhibitor binding to interaction site for ATP of C-terminus of Hsp90. Furthermore, our study revealed that disulfide bond was essential moiety for inhibition activity of PEN-A on Hsp90. This suggested that PEN-A may be bound to cysteine residues near amino acid region which was responsible for dimerization of Hsp90. All results indicate that PEN-A is a novel C-terminal inhibitor of Hsp90 and worthy for further study in the future not only for drug development but also for unraveling the bioactivities of Hsp90.

High-throughput screening of novel pyruvate dehydrogenase kinases inhibitors and biological evaluation of their in vitro and in vivo antiproliferative activity

Overexpression of pyruvate dehydrogenase kinases (PDKs) has been widely noticed in a variety of human solid tumors, which could be regarded as an attractive therapeutic target for cancer therapy. In this paper, we present an enzymatic screening assay and multiple biological evaluations for the identification of potential PDKs, especially PDK1 inhibitors. We identified 9 potential PDKs inhibitors from the screening of an in-house small molecule library, all of the identified inhibitors reduced pyruvate dehydrogenase (PDH) complex phosphorylation. Among which, 4, 5, and 9 displayed the most potent PDKs inhibitory activities, with EC₅₀ values of 0.34, 1.4, and 1.6 μM in an enzymatic assay, respectively. A kinase inhibition assay suggested that 4, 5, and 9 were pan-isoform PDK inhibitors, but more sensitive to PDK1. Meanwhile, the three compounds inhibited HSP90, with IC₅₀ values of 0.78, 3.58, and 2.70 μM, respectively. The cell viability assay indicated that 4 inhibited all of the tested cancer cells proliferation, with a GC₅₀ value of 2.3 μM against NCIH1975 cell, but has little effect on human normal lung cell BEAS-2B cell. In the NCIH1975 xenograft models, 4 displayed strong antitumor activities at a dose of 10 and 20 mg/kg, but with no negative effect on the mice weight. In addition, 4 decreased the ECAR and lactate formation, increased OCR and ROS level in NCIH1975 cancer cell, which could be used as a promising modulator to reprogram the glucose metabolic pathways in NCIH1975 cancer cells.

Discovery of novel pyruvate dehydrogenase kinases inhibitors by screening of an in-house small molecule library for anti-lung cancer therapeutics

Pyruvate dehydrogenase kinases (PDKs) are widely over-expressed in various human solid cancers, making them attractive therapeutic targets for cancer treatment. Herein, we report the identification of structurally novel PDKs inhibitors by screening of an in-house small molecule library. Biochemical assay indicated that the identified compounds 1-4 inhibited PDK1 activity with EC₅₀ values of 0.50, 1.99, 4.64, and 0.42 µM, respectively. The ITC analysis suggested that the identified compounds 1-4 were pan-isoform PDK inhibitors, which bound to and inhibited the four PDK isoforms. Moreover, 1-4 dose-dependently reduced pyruvate dehydrogenase complex phosphorylation in NCI-H1975 cell. Molecular docking suggested that the most potent compound 4 docked well in the ATP binding pocket of the four PDK isoforms, forming direct hydrogen bond interactions with the conserved amino acids Thr and Asp in ATP binding pocket of PDKs. The cell viability assay demonstrated that 4 potently blocked NCI-H1975 cell proliferation (IC₅₀ = 3.32 µM), but had little effect on human normal lung cell MRC-5 even with the tested concentration up to 40 µM. All the data demonstrated that 4 was a promising lead for the development of structurally novel PDKs inhibitor for the cancer treatment.

Identification of Novel Pyruvate Dehydrogenase Kinase 1 (PDK1) Inhibitors by Kinase Activity-Based High-Throughput Screening for Anticancer Therapeutics

Warburg effect, a preference of aerobic glycolysis for energy production even in the presence of adequate oxygen, is one of the most prominent distinctions of cancer cells from their normal equivalents. Upregulated pyruvate dehydrogenase kinase 1 (PDK1) was found to dominate the pivotal switch from mitochondrial respiration to aerobic glycolysis by inactivating pyruvate dehydrogenase (PDH) in cancer cells. PDK1 inhibition may lead to an unfavorable environment for cancer cells, which presents an opportunity for anticancer therapy. However, up to now, only limited number of PDK1 inhibitors were reported. In this work, we reported our attempt to discover novel small molecules from a diverse chemical library containing 15 000 small molecules selected from the Chembridge screening library. We developed a kinase activity-based high throughput screening (HTS) assay for initial screening of PDK1 inhibitors. Seven PDK1 inhibitory compounds were identified with IC₅₀ values range from 0.68 and 45.69 μM. Follow up evaluations on these compounds revealed good PDK1 binding affinity and antiproliferative activities in cancer cell lines, with two novel hits (9 and 10) clearly outperformed others compounds in terms of PDK1 inhibition and the suppression of cancer cell proliferation. 9 and 10 may serve as new chemistry starting points for further structural modifications to improve the potency on PDK1 inhibition for anticancer treatment.

Phenotype and target-based chemical biology investigations in cancers

Chemical biology has been attracting a lot of attention because of the key roles of chemical methods and techniques in helping to decipher and manipulate biological systems. Although chemical biology encompasses a broad field, this review will focus on chemical biology aimed at using exogenous chemical probes to interrogate, modify and manipulate biological processes, at the cellular and organismal levels, in a highly controlled and dynamic manner. In this area, many advances have been achieved for cancer biology and therapeutics, from target identification and validation based on active anticancer compounds (forward approaches) to discoveries of anticancer molecules based on some important targets including protein-protein interaction (reverse approaches). Herein we attempt to summarize some recent progresses mainly from China through applying chemical biology approaches to explore molecular mechanisms of carcinogenesis. Additionally, we also outline several new strategies for chemistry to probe cellular activities such as proximity-dependent labeling methods for identifying protein-protein interactions, genetically encoded sensors, and light activating or repressing gene expression system.

Liquid Chromatography-Tandem Mass Spectrometry Method Revealed that Lung Cancer Cells Exhibited Distinct Metabolite Profiles upon the Treatment with Different Pyruvate Dehydrogenase Kinase Inhibitors

Pyruvate dehydrogenase kinases (PDKs) dominate the critical switch between mitochondria-based respiration and cytoplasm-based glycolysis by controlling pyruvate dehydrogenase (PDH) activity. Up-regulated PDKs play a great role in the Warburg effect in cancer cells and accordingly present a therapeutic target. Dichloroacetate (DCA) and AZD7545 are the two most-well-known PDK inhibitors exhibiting distinct pharmacological profiles. DCA showed anticancer effects in various preclinical models and clinical studies, while the primary preclinical indication of AZD7545 was on the improvement of glucose control in type II diabetes. Little, if any, study has been undertaken the elucidation of the effects of PDK inhibition on the metabolites in the tricarboxylic acid (TCA) cycle. Herein, the metabolite alterations of lung cancer cells (A549) upon the treatment with PDK inhibitors were studied using a reliable liquid-chromatography-based tandem mass spectrometry method. The developed method was validated for quantification of all common glycolysis and TCA cycle catabolites with good sensitivity and reproducibility, including glucose, pyruvate, lactate, acetyl coenzyme A, citrate, α-ketoglutarate, fumarate, succinate, malate, and oxaloacetate. Our results suggested that A549 cells exhibited distinct metabolite profiles following the treatment with DCA or AZD7545, which may reflect the different pharmacological indications of these two drugs.

Effects of β-caryophyllene on arginine ADP-ribosyltransferase 1-mediated regulation of glycolysis in colorectal cancer under high-glucose conditions

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of the development of colorectal cancer (CRC). A previous study revealed that the levels of arginine-specific mono-ADP-ribosyltransferase 1 (ART1) in CRC tissues from patients with T2DM were higher than in non-diabetic patients. Hyperglycemia, which is a risk factor of cancer, is a common feature of T2DM; however, the effects of ART1 on glycolysis and energy metabolism in CRC cells under high-glucose conditions remains to be elucidated. β-caryophyllene (BCP) has been reported to exert anticancer and hypoglycemic effects. In the present study, CT26 cells were cultured under a high-glucose conditions and the expression levels of relevant factors were detected by western blotting. Cell Counting Kit-8 assay, flow cytometry, Hoechst 33258 staining, ATP assay and lactic acid assay were used to detect the proliferation, apoptosis and energy metabolism of CT26 cells. To observe the effects of ART1 and BCP on tumor growth in vivo, CT26 cell tumors were successfully transplanted into BALB/c mice with T2DM. The results demonstrated that overexpression of ART1 may increase glycolysis and energy metabolism in CT26 CRC cells under high glucose conditions by regulating the protein kinase B/mammalian target of rapamycin/c‑Myc signaling pathway and the expression of glycolytic enzymes. BCP inhibited the effects induced by ART1, which may be due to a BCP-induced reduction in the expression levels of ART1 via nuclear factor-κB. Therefore, ART1 may be considered a therapeutic target for the treatment of diabetic patients with CRC.

Design, Synthesis, and Biological Evaluation of Orally Available First-Generation Dual-Target Selective Inhibitors of Acetylcholinesterase (AChE) and Phosphodiesterase 5 (PDE5) for the Treatment of Alzheimer's Disease

Through drug discovery strategies of repurposing and redeveloping existing drugs, a series of novel tadalafil derivatives were rationally designed, synthesized, and evaluated to seek dual-target AChE/PDE5 inhibitors as good candidate drugs for Alzheimer's disease (AD). Among these derivatives, 1p and 1w exhibited excellent selective dual-target AChE/PDE5 inhibitory activities and improved blood-brain barrier (BBB) penetrability. Importantly, 1w·Cit (citrate of 1w) could reverse the cognitive dysfunction of scopolamine-induced AD mice and exhibited an excellent effect on enhancing cAMP response element-binding protein (CREB) phosphorylation in vivo, a crucial factor in memory formation and synaptic plasticity. Moreover, the molecular docking simulations of 1w with hAChE and hPDE5A confirmed that our design strategy was rational. In summary, our research provides a potential selective dual-target AChE/PDE5 inhibitor as a good candidate drug for the treatment of AD, and it could also be regarded as a small molecule probe to validate the novel AD therapeutic approach in vivo.