Shikonin is a novel and selective IMPDH2 inhibitor that target triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is heterogeneous disease with a poor prognosis. It is therefore important to explore novel therapeutic agents to improve the clinical efficacy for TNBC. The inosine 5'-monophosphate dehydrogenase 2 (IMPDH2) is a rate-limiting enzyme in the de novo synthesis of guanine nucleotides. It is always overexpressed in many types of tumors, including TNBC and regarded as a potential target for cancer therapy. Through screening a library of natural products, we identified shikonin, a natural bioactive component of Lithospermum erythrorhizon, is a novel and selective IMPDH2 inhibitor. Enzymatic analysis using Lineweaver-Burk plot indicates that shikonin is a competitive inhibitor of IMPDH2. The interaction between shikonin and IMDPH2 was further investigated by thermal shift assay, fluorescence quenching, and molecular docking simulation. Shikonin treatment effectively inhibits the growth of human TNBC cell line MDA-MB-231, and murine TNBC cell line, 4T1 in a dose-dependent manner, which is impaired by exogenous supplementation of guanosine, a salvage pathway of purine nucleotides. Most importantly, IMPDH2 knockdown significantly reduced cell proliferation and conferred resistance to shikonin in TNBC. Collectively, our findings showed the natural product shikonin as a selective inhibitor of IMPDH2 with anti-TNBC activity, impelling its further study in clinical trials.

From a Designer Drug to the Discovery of Selective Cannabinoid Type 2 Receptor Agonists with Favorable Pharmacokinetic Profiles for the Treatment of Systemic Sclerosis.

Synthetic cannabinoids, as exemplified by SDB-001 (1), bind to both CB1 and CB2 receptors and exert cannabimimetic effects similar to (-)-trans-Δ9-tetrahydrocannabinol, the main psychoactive component present in the cannabis plant. As CB1 receptor ligands were found to have severe adverse psychiatric effects, increased attention was turned to exploiting the potential therapeutic value of the CB2 receptor. In our efforts to discover novel and selective CB2 receptor agonists, 1 was selected as a starting point for hit molecule identification and a class of 1H-pyrazole-3-carboxamide derivatives were thus designed, synthesized, and biologically evaluated. Systematic structure-activity relationship investigations resulted in the identification of the most promising compound 66 as a selective CB2 receptor agonist with favorable pharmacokinetic profiles. Especially, 66 treatment significantly attenuated dermal inflammation and fibrosis in a bleomycin-induced mouse model of systemic sclerosis, supporting that CB2 receptor agonists might serve as potential therapeutics for treating systemic sclerosis.

Natural product corynoline suppresses melanoma cell growth through inducing oxidative stress.

Natural product corynoline is a unique isoquinoline alkaloid extracted from traditional Chinese medicine Corydalis bungeana Turcz, whereas its anticancer properties have not been investigated. In this study, we found that corynoline potently impairs the growth of melanoma cells, B16F10, and A375 in a concentration-dependent manner. Treatment of melanoma cells with corynoline results in G2 cell arrest accompanied by reduced cdc2 activation. Furthermore, corynoline triggers apoptosis of melanoma cells, which is associated with increased expression of Bax and cleaved caspase-3. Mechanistic study indicates that corynoline strongly induces reactive oxygen species (ROS) generation and subsequent DNA damage as evidenced by γ-H2AX accumulation. Notably, the effect of corynoline on melanoma cell cycle and apoptosis is abolished by a ROS scavenger N-acetyl cysteine (NAC), indicating a ROS-dependent mechanism. Finally, corynoline significantly inhibits in vivo B16F10 melanoma tumor growth accompanied by reduced expression of Ki-67 in tumor tissue. Taken together, our data suggest that corynoline suppresses melanoma cell growth in vitro and in vivo by inducing oxidative stress and represents a potential therapeutic agent for melanoma patients.

Celastrol is a novel selective agonist of cannabinoid receptor 2 with anti-inflammatory and anti-fibrotic activity in a mouse model of systemic sclerosis.

BACKGROUND: Increasing evidence indicated that the cannabinoid receptors were involved in the pathogenesis of organ fibrogenesis. PURPOSE: The purpose of this study was to discover novel cannabinoid receptor 2 (CB2) agonist and assess the potential of CB2 activation in treating systemic sclerosis. METHODS: A gaussia princeps luciferase-based split luciferase complementation assay (SLCA) was developed for detection of the interaction between CB2 and ß-arrestin2. A library of 366 natural products was then screened as potential CB2 agonist using SLCA approach. Several GPCR functional assays, including HTRF-based cAMP assay and calcium mobilization were also utilized to evaluated CB2 activation. Bleomycin-induced experimental systemic sclerosis was used to assess the in vivo anti-fibrotic effects. Dermal thickness and collagen content were evaluated via H&E and sirius red staining. RESULTS: Celastrol was identified as a new agonist of CB2 by using SLCA. Furthermore, celastrol triggers several CB2-mediated downstream signaling pathways, including calcium mobilization, inhibition of cAMP accumulation, and receptor desensitization in a dose-dependent manner, and it has a moderate selectivity on CB1. In addition, celastrol exhibited the anti-inflammatory properties on lipopolysaccharide (LPS) treated murine Raw 264.7 macrophages and primary macrophages. Finally, we found that celastrol exerts anti-fibrotic effects in the bleomycin-induced systemic sclerosis mouse model accompanied by reduced inflammatory conditions. CONCLUSION: Taken together, celastrol is identified a novel selective CB2 agonist using a new developed arrestin-based SLCA, and CB2 activation by celastrol reduces the inflammatory response, and prevents the development of dermal fibrosis in bleomycin-induced systemic sclerosis mouse model.

A genome-wide positioning systems network algorithm for in silico drug repurposing.

Recent advances in DNA/RNA sequencing have made it possible to identify new targets rapidly and to repurpose approved drugs for treating heterogeneous diseases by the 'precise' targeting of individualized disease modules. In this study, we develop a Genome-wide Positioning Systems network (GPSnet) algorithm for drug repurposing by specifically targeting disease modules derived from individual patient's DNA and RNA sequencing profiles mapped to the human protein-protein interactome network. We investigate whole-exome sequencing and transcriptome profiles from ~5,000 patients across 15 cancer types from The Cancer Genome Atlas. We show that GPSnet-predicted disease modules can predict drug responses and prioritize new indications for 140 approved drugs. Importantly, we experimentally validate that an approved cardiac arrhythmia and heart failure drug, ouabain, shows potential antitumor activities in lung adenocarcinoma by uniquely targeting a HIF1α/LEO1-mediated cell metabolism pathway. In summary, GPSnet offers a network-based, in silico drug repurposing framework for more efficacious therapeutic selections.

Pharmacological inhibition of dihydroorotate dehydrogenase induces apoptosis and differentiation in acute myeloid leukemia cells.

Acute myeloid leukemia is a disorder characterized by abnormal differentiation of myeloid cells and a clonal proliferation derived from primitive hematopoietic stem cells. Interventions that overcome myeloid differentiation have been shown to be a promising therapeutic strategy for acute myeloid leukemia. In this study, we demonstrate that CRISPR/Cas9-mediated knockout of dihydroorotate dehydrogenase leads to apoptosis and normal differentiation of acute myeloid leukemia cells, indicating that dihydroorotate dehydrogenase is a potential differentiation regulator and a therapeutic target in acute myeloid leukemia. By screening a library of natural products, we identified a novel dihydroorotate dehydrogenase inhibitor, isobavachalcone, derived from the traditional Chinese medicine Psoralea corylifolia Using enzymatic analysis, thermal shift assay, pull down, nuclear magnetic resonance, and isothermal titration calorimetry experiments, we demonstrate that isobavachalcone inhibits human dihydroorotate dehydrogenase directly, and triggers apoptosis and differentiation of acute myeloid leukemia cells. Oral administration of isobavachalcone suppresses subcutaneous HL60 xenograft tumor growth without obvious toxicity. Importantly, our results suggest that a combination of isobavachalcone and adriamycin prolonged survival in an intravenous HL60 leukemia model. In summary, this study demonstrates that isobavachalcone triggers apoptosis and differentiation of acute myeloid leukemia cells via pharmacological inhibition of human dihydroorotate dehydrogenase, offering a potential therapeutic strategy for acute myeloid leukemia.

Coptisine, a natural alkaloid from Coptidis Rhizoma, inhibits plasmodium falciparum dihydroorotate dehydrogenase.

Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) is a promising drug target for antimalarial chemotherapy. In our continuous efforts to develop more potent PfDHODH inhibitors, a unique library of active ingredients from traditional Chinese medicine (TCM) has been collected and was screened in this study. Through the initial screening, we found that coptisine, a natural alkaloid from TCM Coptidis Rhizoma, was a novel and potent inhibitor of PfDHODH with an IC50 value of 1.83 ± 0.08 µm. At the same time, enzyme kinetic analysis using Lineweaver-Burk plot indicated that coptisine is an uncompetitive inhibitor for PfDHODH. Thermal shift assay and molecular docking simulation research reveal that coptisine is capable of binding with PfDHODH. Moreover, coptisine exhibits weak inhibition activity against human DHODH, indicating that coptisine is a selective inhibitor of PfDHODH. Taken together, our study highlights the potential of active ingredients in TCM as valuable resource for discovering novel chemical scaffolds for PfDHODH.

Small molecule 1'-acetoxychavicol acetate suppresses breast tumor metastasis by regulating the SHP-1/STAT3/MMPs signaling pathway.

Signal transducer and activator of transcription 3 (STAT3) is implicated breast cancer metastasis and represents a potential target for developing new anti-tumor metastasis drugs. The purpose of this study is to investigate whether the natural agent 1'-acetoxychavicol acetate (ACA), derived from the rhizomes and seeds of Languas galanga, could suppress breast cancer metastasis by targeting STAT3 signaling pathway. ACA was examined for its effects on breast cancer migration/invasion and metastasis using Transwell assays in vitro and breast cancer skeletal metastasis mouse model in vivo (n = 10 mice per group). The inhibitory effect of ACA on cellular STAT3 signaling pathway was investigated by series of biochemistry analysis. The chavicol preferentially suppressed cancer cell migration and invasion, and this activity was superior to its cytotoxic effects. ACA suppressed both constitutive and interleukin-6-inducible STAT3 activation and diminished the accumulation of STAT3 in the nucleus and its DNA-binding activity. More importantly, ACA treatment led to significant up-regulation of Src homology region 2 domain-containing phosphatase 1 (SHP-1), and the ACA-induced depression of cancer cell migration and STAT3 signaling could be apparently reversed by blockade of SHP-1. Matrix metalloproteinase (MMP)-2 and -9, gene products of STAT3 that regulate cell invasion, were specifically suppressed by ACA. In tumor metastasis model, ACA potently inhibited the human breast cancer cell-induced osteolysis, and had little apparent in vivo toxicity at the test concentrations. ACA is a novel drug candidate for the inhibition of tumor metastasis through interference with the SHP-1/STAT3/MMPs signaling pathway.

Dietary flavonoids fisetin and myricetin: dual inhibitors of Plasmodium falciparum falcipain-2 and plasmepsin II.

Malaria is one of the most devastating infectious diseases in the developing world. Until now, only one candidate malaria vaccine RTS,S/AS01 has shown modest protection in phase 3 trial in African infants. Hence the treatment of malaria still depends on the current chemotherapeutic drugs. Considering the resistance of malaria parasites to almost all used antimalarial drugs, aiming at multi-targets rather than a single target will be a more promising strategy. Previous studies have shown that myricetin and fisetin exhibited in vitro antimalarial activity against Plasmodium falciparum, but very little research focused on the molecular mechanism for their parasiticidal activity. The cysteine protease falcipain-2 and aspartic protease plasmepsin II have long been considered as important antimalarial drug targets, especially combined inhibition of these two proteases. In this study, we determined that myricetin and fisetin are dual inhibitors of falcipain-2 and plasmepsin II, which might account for their antimalarial properties. Overall, the dual inhibition of falcipain-2 and plasmepsin II by myricetin and fisetin has shed light on a possible mechanism for their antimalarial activity and provided a rationale for further development as antimalarial drugs.

Discovery of new potent inhibitors for carbonic anhydrase IX by structure-based virtual screening.

Through structure-based virtual screening, some dozen of benzene sulfonamides with novel scaffolds are identified as potent inhibitors against carbonic anhydrase (CA) IX with IC50 values ranging from 2.86 to 588.34 nM. Among them, compounds 1 and 9 show high selectivity against tumor-target CA IX over CA II (the selectivity ratios are 21.3 and 136.6, respectively). The possible binding poses of hit compounds are also explored and the selectivity is elucidated by molecular docking simulations. The hit compounds discovered in this work would provide novel scaffolds for further hit-to-lead optimization.

Identification of diverse dipeptidyl peptidase IV inhibitors via structure-based virtual screening.

Dipeptidyl peptidase IV (DPP4) is an important target for the treatment of type II diabetes mellitus. Inhibition of DPP4 will improve glycemic control in such patients by preventing the rapid breakdown and thereby prolonging the physiological actions of incretin hormones. Known DPP4 inhibitors (including marketed drugs and those drug candidates) appear to share similar structural features: the cyanopyrrolidine moieties, the xanthenes/pyrimidine parts and amino-like linkages. In this study, a multi-step virtual screening strategy including both rigid and flexible docking was employed to search for novel structures with DPP4 inhibition. From SPECS database, consisting of over 190,000 commercially available compounds, 99 virtual hits were picked up and 15 of them were eventually identified to have DPP4 inhibitory activities at 5 ~ 50 µM. Diverse structures of our compounds were out of usual structural categories. Hence a pharmacophore model was built to further explore their common binding features on the enzyme. The results provided a new pathway for the discovery of DPP4 inhibitors and would be helpful for further optimization of DPP4 inhibitors.

[Review on biosynthesis of podophyllotoxin].

Podophyllotoxin (PTOX) is an extremely important plant-derived natural product, of which derivatives, like etoposide and teniposide, have been widely applied in therapies for cancers and venereal wart. A durable, intense plant extraction of podophyllotoxin posed a severe pressure on wild resources; researchers consequently sought to explore new sources, like cultivation, plant cell or organ culture, and chemical synthesis. Understanding biosynthesis of PTOX is one of the basic necessary steps for standard cultivation of medicinal plants and metabolite engineering. An important progress has been made in this field during the last two decades, particularly in the last ten years. Although a number of reviews concerning the related topic have existed, we specifically deal with biosynthesis of podophyllotoxin with an emphasis on the literatures of the past decade, highlighting characterization of genes encoding synthetic enzymes and down-stream metabolism of PTOX. The present review focuses on several key biosynthesis processes, important metabolites, function of related enzymes, and characterization of cDNA encoding the enzymes. Finally, the author proposed a hypothetical biosynthetic scheme of podophyllotoxin and perspectives.