Zhengfeng Yang

Maslinic acid potentiates the anti-tumor activity of tumor necrosis factor α by inhibiting NF-κB signaling pathway

BackgroundTumor necrosis factor alpha (TNFα) has been used to treat certain tumors in clinic trials. However, the curative effect of TNFα has been undermined by the induced-NF-κB activation in many types of tumor. Maslinic acid (MA), a pharmacological safe natural product, has been known for its important effects as anti-oxidant, anti-inflammatory, and anti-viral activities. The aim of this study was to determine whether MA potentiates the anti-tumor activity of TNFα though the regulation of NF-κB activation.ResultsIn this study, we demonstrate that MA significantly enhanced TNFα-induced inhibition of pancreatic cancer cell proliferation, invasion, and potentiated TNFα-induced cell apoptosis by suppressing TNFα-induced NF-κB activation in a dose- and time-dependent manner. Addition of MA inhibited TNFα-induced IκBα degradation, p65 phosphorylation, and nuclear translocation. Furthermore, MA decreased the expression levels of NF-κB-regulated genes, including genes involved in tumor cell proliferation (Cyclin D1, COX-2 and c-Myc), apoptosis (Survivin, Bcl-2, Bcl-xl, XIAP, IAP-1), invasion (MMP-9 and ICAM-1), and angiogenesis (VEGF). In athymic nu/nu mouse model, we further demonstrated that MA significantly suppressed pancreatic tumor growth, induced tumor apoptosis, and inhibited NF-κB-regulated anti-apoptotic gene expression, such as Survivin and Bcl-xl.ConclusionsOur data demonstrate that MA can potentiate the anti-tumor activities of TNFα and inhibit pancreatic tumor growth and invasion by activating caspase-dependent apoptotic pathway and by suppressing NF-κB activation and its downstream gene expression. Therefore, MA together with TNFα could be new promising agents in the treatment of pancreatic cancer.

LGR4 is a receptor for RANKL and negatively regulates osteoclast differentiation and bone resorption

Tumor necrosis factor (TNF) superfamily member 11 (TNFSF11, also known as RANKL) regulates multiple physiological or pathological functions, including osteoclast differentiation and osteoporosis. TNFRSF11A (also called RANK) is considered to be the sole receptor for RANKL. Herein we report that leucine-rich repeat-containing G-protein-coupled receptor 4 (LGR4, also called GPR48) is another receptor for RANKL. LGR4 competes with RANK to bind RANKL and suppresses canonical RANK signaling during osteoclast differentiation. RANKL binding to LGR4 activates the Gαq and GSK3-β signaling pathway, an action that suppresses the expression and activity of nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1 (NFATC1) during osteoclastogenesis. Both whole-body (Lgr4−/−) and monocyte conditional knockout mice of Lgr4 (Lgr4 CKO) exhibit osteoclast hyperactivation (including elevation of osteoclast number, surface area, and size) and increased bone erosion. The soluble LGR4 extracellular domain (ECD) binds RANKL and inhibits osteoclast differentiation in vivo. Moreover, LGR4-ECD therapeutically abrogated RANKL-induced bone loss in three mouse models of osteoporosis. Therefore, LGR4 acts as a second RANKL receptor that negatively regulates osteoclast differentiation and bone resorption.

Maslinic Acid Suppresses Osteoclastogenesis and Prevents Ovariectomy-Induced Bone Loss by Regulating RANKL-Mediated NF-κB and MAPK Signaling Pathways

Activation of NF‐κB and MAPK/activator protein 1 (AP‐1) signaling pathways by receptor activator NF‐κB ligand (RANKL) is essential for osteoclast activity. Targeting NF‐κB and MAPK/AP‐1 signaling to modulate osteoclast activity has been a promising strategy for osteoclast‐related diseases. In this study we examined the effects of maslinic acid (MA), a pentacyclic triterpene acid that is widely present in dietary plants, on RANKL‐induced osteoclastogenesis, osteoclast function, and signaling pathways by in vitro and in vivo assay systems. In mouse bone marrow monocytes (BMMs) and RAW264.7 cells, MA inhibited RANKL‐induced osteoclastogenesis in a dose‐dependent manner within nongrowth inhibitory concentration, and MA decreased osteoclastogenesis‐related marker gene expression, including TRACP, MMP9, c‐Src, CTR, and cathepsin K. Specifically, MA suppressed osteoclastogenesis and actin ring formation at early stage. In ovariectomized mice, administration of MA prevented ovariectomy‐induced bone loss by inhibiting osteoclast activity. At molecular levels, MA abrogated the phosphorylation of MAPKs and AP‐1 activity, inhibited the IκBα phosphorylation and degradation, blocked NF‐κB/p65 phosphorylation, nuclear translocation, and DNA‐binding activity by downregulating RANK expression and blocking RANK interaction with TRAF6. Together our data demonstrate that MA suppresses RANKL‐induced osteoclastogenesis through NF‐κB and MAPK/AP‐1 signaling pathways and that MA is a promising agent in the treatment of osteoclast‐related diseases such as osteoporosis.

Inhibition of Breast Cancer Metastases by a Novel Inhibitor of TGFβ Receptor 1

BACKGROUND Transforming growth factor beta (TGFβ), which is implicated in metastasis to various organs in breast cancer, is a potential target for new antitumor metastasis drugs. METHODS To identify specific inhibitors of TGFβ receptor 1 (TGFβR1) in breast cancer metastasis, a virtual library of more than 400000 different compounds was screened by molecular docking modeling and confirmed with Smad-binding element luciferase and TGFβR1 kinase assays. Affymetrix GeneChip expression analysis of mRNA levels and real-time polymerase chain reaction were performed to determine expression changes of TGFβ-mediated, metastasis-associated genes in breast cancer cells after treatment with the small-molecule inhibitor YR-290. YR-290 was also examined for its effects on breast cancer migration, invasion, and metastasis using transwell and epithelial-to-mesenchymal transition (EMT) assays in vitro and three different mouse (BALB/c and NU/NU nude) models (n = 10 per group). Kaplan-Meier analyses were used to assess survival. All statistical tests were two-sided. RESULTS YR-290 interacted with the kinase domain of TGFβR1, abrogated kinase activity (half maximal inhibitory concentration = 137nM, 95% confidence interval = 126.4 to 147.6nM) and inhibited the TGFβ-mediated downstream signaling pathway and metastasis-associated genes in breast cancer cells. YR-290 inhibited TGFβ-modulated breast cancer cell migration and invasion. In tumor metastasis mouse models, YR-290 almost completely blocked cancer metastasis. Numbers of lung tumor nodules of mice treated with 1mg/kg and 5mg/kg YR-290 were reduced by 74.93% (95% confidence interval = 61.45% to 88.41%) and 94.93% (95% confidence interval = 82.13% to 100%), respectively, compared with control mice. Treatment with YR-290 also statistically significantly prolonged the survival of tumor-bearing mice. CONCLUSIONS YR-290 is a novel inhibitor of tumor metastasis that works by blocking TGFβ signaling pathways.

Caffeic acid 3,4-dihydroxy-phenethyl ester suppresses receptor activator of NF-κB ligand–induced osteoclastogenesis and prevents ovariectomy-induced bone loss through inhibition of mitogen-activated protein kinase/activator protein 1 and Ca2+–nuclear factor of activated T-cells cytoplasmic 1 signaling pathways.

Receptor activator of NF‐κB ligand (RANKL) stimulation leads to the activation of mitogen‐activated protein kinase (MAPK)/AP‐1 and Ca2+–nuclear factor of activated T‐cells cytoplasmic 1 (NFATc1) signaling pathways in osteoclastogenesis. Targeting these pathways has been an encouraging strategy for bone‐related diseases, such as postmenopausal osteoporosis. In this study, we examined the effects of caffeic acid 3,4‐dihydroxy‐phenethyl ester (CADPE) on osteoclastogenesis. In mouse bone marrow monocytes (BMMs) and RAW264.7 cells, CADPE suppressed RANKL‐induced osteoclast differentiation and actin‐ring formation in a dose‐dependent manner within non–growth inhibitory concentrations at the early stage, while CADPE had no effect on macrophage colony‐stimulating factor (M‐CSF)‐induced proliferation and differentiation. At the molecular level, CADPE inhibited RANKL‐induced phosphorylation of MAPKs, including extracellular signal‐regulated kinases 1/2 (ERK1/2), p38, and c‐Jun N‐terminal kinase (JNK), without significantly affecting the NF‐κB signaling pathway. CADPE abrogated RANKL‐induced activator protein 1 (AP‐1)/FBJ murine osteosarcoma viral oncogene homolog (c‐Fos) nuclear translocation and activation. Overexpression of c‐Fos prevented the inhibition by CADPE of osteoclast differentiation. Furthermore, CADPE suppressed RANKL‐induced the tumor necrosis factor receptor associated factor 6 (TRAF6) interaction with c‐src tyrosine kinase (c‐Src), blocked RANKL‐induced the phosphorylation of protein kinase B (AKT), and inhibited RANKL‐induced Ca2+ oscillation. As a result, CADPE decreased osteoclastogenesis‐related marker gene expression, including NFATc1, TRAP, cathepsin K, and c‐Src. To test the effects of CADPE on osteoclast activity in vivo, we showed that CADPE prevented ovariectomy‐induced bone loss by inhibiting osteoclast activity. Together, our data demonstrate that CADPE suppresses osteoclastogenesis and bone loss through inhibiting RANKL‐induced MAPKs and Ca2+‐NFATc1 signaling pathways. CADPE is a novel agent in the treatment of osteoclast‐related diseases, such as osteoporosis.

Dauricine induces apoptosis, inhibits proliferation and invasion through inhibiting NF-κB signaling pathway in colon cancer cells†

Dauricine, a bioactive component of Asiatic Moonseed Rhizome, has been widely used to treat a large number of inflammatory diseases in traditional Chinese medicine. In our study, we demonstrated that dauricine inhibited colon cancer cell proliferation and invasion, and induced apoptosis by suppressing nuclear factor‐kappaB (NF‐κB) activation in a dose‐ and time‐dependent manner. Addition of dauricine inhibited the phosphorylation and degradation of IκBα, and the phosphorylation and translocation of p65. Moreover, dauricine down‐regulated the expression of various NF‐κB‐regulated genes, including genes involved cell proliferation (cyclinD1, COX2, and c‐Myc), anti‐apoptosis (survivin, Bcl‐2, XIAP, and IAP1), invasion (MMP‐9 and ICAM‐1), and angiogenesis (VEGF). In athymic nu/nu mouse model, we further demonstrated that dauricine significantly suppressed colonic tumor growth. Taken together, our results demonstrated that dauricine inhibited colon cancer cell proliferation, invasion, and induced cell apoptosis by suppressing NF‐κB activity and the expression profile of its downstream genes. These findings provide evidence for a novel role of dauricine in preventing or treating colon cancer through modulation of NF‐κB singling pathway. J. Cell. Physiol. 225: 266–275, 2010.

Synthesis and Biological Evaluation of Novel Tetrahydro-β-carboline Derivatives as Antitumor Growth and Metastasis Agents through Inhibiting the Transforming Growth Factor-β Signaling Pathway

The transforming growth factor beta (TGFβ) signaling cascade is considered as one of the pivotal oncogenic pathways in most advanced cancers. Inhibition of the TGFβ signaling pathway by specific antagonists, neutralizing antibodies, or small molecules is considered as an effective strategy for the treatment of tumor growth and metastasis. Here we demonstrated the identification of a series of tetrahydro-β-carboline derivatives from virtual screening which potentially inhibit the TGFβ signaling pathway. Optimization of the initial hit compound 2-benzoyl-1,3,4,9-tetrahydro-β-carboline (8a) through substitution at different positions to define the structure-activity relationship resulted in the discovery of potent inhibitors of the TGFβ signaling pathway. Among them, compound 8d, one of the tested compounds, not only showed potent inhibition of lung cancer cell proliferation and migration in vitro but also strongly suppressed growth of lung cancer and breast cancer in vivo.

Stereoselective synthesis of some methyl-substituted steroid hormones and their in vitro cytotoxic activity against human gastric cancer cell line MGC-803.

A series of 3-, 7-, 15-, and 16-methyl-substituted steroid analogs were synthesized via a highly stereoselective 1,6-conjugate addition. Under the catalysis of CuBr, AlMe(3) reacted with four steroid dienone precursors to afford either the corresponding alpha-epimer of C-3 and C-7 methyl-substituted steroids as the major products, and the ratio of alpha/beta was up to 10/1. No beta-epimer has been detected for methyl addition at C-16. However, under the same reaction conditions, enantioselective methyl addition at C-15 afforded the 15beta-epimer as the major product. The preliminary SAR analysis showed that the methyl substituents at C-7alpha and C-15beta positions lead to a dramatical increase in potency against human gastric cancer cell line MGC-803.

Crystal structure of LGR4-Rspo1 complex: insights into the divergent mechanisms of ligand recognition by leucine-rich repeat G-protein-coupled receptors (LGRs).

Background: LGR receptors play important roles in many developmental processes. Results: The structure of human LGR4-Rspo1 complex was solved. Conclusion: Diverse mechanisms are utilized by LGRs in ligand recognition. Significance: Our structures are important for potential drug design. Leucine-rich repeat G-protein-coupled receptors (LGRs) are a unique class of G-protein-coupled receptors characterized by a large extracellular domain to recognize ligands and regulate many important developmental processes. Among the three groups of LGRs, group B members (LGR4–6) recognize R-spondin family proteins (Rspo1–4) to stimulate Wnt signaling. In this study, we successfully utilized the “hybrid leucine-rich repeat technique,” which fused LGR4 with the hagfish VLR protein, to obtain two recombinant human LGR4 proteins, LGR415 and LGR49. We determined the crystal structures of ligand-free LGR415 and the LGR49-Rspo1 complex. LGR4 exhibits a twisted horseshoe-like structure. Rspo1 adopts a flat and β-fold architecture and is bound in the concave surface of LGR4 in the complex through electrostatic and hydrophobic interactions. All the Rspo1-binding residues are conserved in LGR4–6, suggesting that LGR4–6 bind R-spondins through an identical surface. Structural analysis of our LGR4-Rspo1 complex with the previously determined LGR4 and LGR5 structures revealed that the concave surface of LGR4 is the sole binding site for R-spondins, suggesting a one-site binding model of LGR4–6 in ligand recognition. The molecular mechanism of LGR4–6 is distinct from the two-step mechanism of group A receptors LGR1–3 and the multiple-interface binding model of group C receptors LGR7–8, suggesting LGRs utilize the divergent mechanisms for ligand recognition. Our structures, together with previous reports, provide a comprehensive understanding of the ligand recognition by LGRs.

Bortezomib Inhibits Giant Cell Tumor of Bone through Induction of Cell Apoptosis and Inhibition of Osteoclast Recruitment, Giant Cell Formation, and Bone Resorption

Giant cell tumor of bone (GCTB) is a rare and highly osteolytic bone tumor that usually leads to an extensive bone lesion. The purpose of this study was to discover novel therapeutic targets and identify potential agents for treating GCTB. After screening the serum cytokine profiles in 52 GCTB patients and 10 normal individuals using the ELISA assay, we found that NF-κB signaling–related cytokines, including TNFα, MCP-1, IL1α, and IL17A, were significantly increased in GCTB patients. The results were confirmed by IHC that the expression and activity of p65 were significantly increased in GCTB patients. Moreover, all of the NF-κB inhibitors tested suppressed GCTB cell growth, and bortezomib (Velcade), a well-known proteasome inhibitor, was the most potent inhibitor in blocking GCTB cells growth. Our results showed that bortezomib not only induced GCTB neoplastic stromal cell (NSC) apoptosis, but also suppressed GCTB NSC–induced giant cell differentiation, formation, and resorption. Moreover, bortezomib specifically suppressed GCTB NSC–induced preosteoclast recruitment. Furthermore, bortezomib ameliorated GCTB cell–induced bone destruction in vivo. As a result, bortezomib suppressed NF-κB–regulated gene expression in GCTB NSC apoptosis, monocyte migration, angiogenesis, and osteoclastogenesis. Particularly, the inhibitory effects of bortezomib were much better than zoledronic acid, a drug currently used in treating GCTB, in our in vitro experimental paradigms. Together, our results demonstrated that NF-κB signaling pathway is highly activated in GCTB, and bortezomib could suppress GCTB and osteolysis in vivo and in vitro, indicating that bortezomib is a potential agent in the treatment of GCTB. Mol Cancer Ther; 15(5); 854–65. ©2016 AACR.