C2-Symmetrical Terphenyl Derivatives as Small Molecule Inhibitors of Programmed Cell Death 1/Programmed Death Ligand 1 Protein-Protein Interaction.

The PD-1/PD-L1 complex is an immune checkpoint responsible for regulating the natural immune response, but also allows tumors to escape immune surveillance. Inhibition of the PD-1/PD-L1 axis positively contributes to the efficacy of cancer treatment. The only available therapeutics targeting PD-1/PD-L1 are monoclonal antibody-based drugs, which have several limitations. Therefore, small molecule compounds are emerging as an attractive alternative that can potentially overcome the drawbacks of mAb-based therapy. In this article, we present a novel class of small molecule compounds based on the terphenyl scaffold that bind to PD-L1. The general architecture of the presented structures is characterized by axial symmetry and consists of three elements: an m-terphenyl core, an additional aromatic ring, and a solubilizing agent. Using molecular docking, we designed a series of final compounds, which were subsequently synthesized and tested in HTRF assay and NMR binding assay to evaluate their activity. In addition, we performed an in-depth analysis of the mutual arrangement of the phenyl rings of the terphenyl core within the binding pocket of PD-L1 and found several correlations between the plane angle values and the affinity of the compounds towards the protein.

Anti-inflammatory and anticancer p-terphenyl derivatives from fungi of the genus Thelephora.

Fungi from the genus Thelephora have been exploited to identify bioactive compounds. The main natural products characterized are para-terphenyl derivatives, chiefly represented by the lead anti-inflammatory compound vialinin A isolated from species T. vialis and T. terrestris. Different series of p-terphenyls have been identified, including vialinins, ganbajunins, terrestrins, telephantins and other products. Their mechanism of action is not always clearly identified, and different potential molecule targets have been proposed. The lead vialinin A functions as a protease inhibitor, efficiently targeting ubiquitin-specific peptidases USP4/5 and sentrin-specific protease SENP1 which are prominent anti-inflammatory and anticancer targets. Protease inhibition is coupled with a powerful inhibition of the cellular production of tumor necrosis factor TNFα. Other mechanisms contributing to the anti-inflammatory or anti-proliferative action of these p-terphenyl compounds have been invoked, including the formation of cytotoxic copper complexes for derivatives bearing a catechol central unit such vialinin A, terrestrin B and telephantin O. These p-terphenyl compounds could be further exploited to design novel anticancer agents, as evidenced with the parent compound terphenyllin (essentially found in Aspergillus species) which has revealed marked antitumor and anti-metastatic effects in xenograft models of gastric and pancreatic cancer. This review shed light on the structural and functional diversity of p-terphenyls compounds isolated from Thelephora species, their molecular targets and pharmacological properties.

HDAC6 inhibitor WT161 performs anti-tumor effect on osteosarcoma and synergistically interacts with 5-FU.

BACKGROUND: WT161, as a selective HDAC6 inhibitor, has been shown to play anti-tumor effects on several kinds of cancers. The aim of the present study is to explore the roles of WT161 in osteosarcoma and its underlying mechanisms. METHODS: The anti-proliferative effect of WT161 on osteosarcoma cells was examined using MTT assay and colony formation assay. Cell apoptosis was analyzed using flow cytometer. The synergistic effect was evaluated by isobologram analysis using CompuSyn software. The osteosarcoma xenograft models were established to evaluate the anti-proliferative effect of WT161 in vivo. RESULTS: WT161 suppressed the cell growth and induced apoptosis of osteosarcoma cells in a dose- and time-dependent manner. Mechanistically, we found that WT161 treatment obviously increased the protein level of PTEN and decreased the phosphorylation level of protein kinase-B (AKT). More importantly, WT161 showed synergistic inhibition with 5-FU on osteosarcoma cells in vitro and in vivo. CONCLUSIONS: These results indicate that WT161 inhibits the growth of osteosarcoma through PTEN and has a synergistic efficiency with 5-FU.

Polyhydroxy p-Terphenyls from a Mangrove Endophytic Fungus Aspergillus candidus LDJ-5.

Six undescribed polyhydroxy p-terphenyls, namely asperterphenyllins A-F, were isolated from an endophytic fungus Aspergillus candidus LDJ-5. Their structures were determined by NMR and MS data. Differing from the previously reported p-terphenyls, asperterphenyllin A represents the first p-terphenyl dimer connected by a C-C bond. Asperterphenyllin A displayed anti-influenza virus A (H1N1) activity and protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with IC50 values of 53 µM and 21 µM, respectively. The anti-influenza virus A (H1N1) activity and protein tyrosine phosphatase 1B (PTP1B) inhibitory activity of p-terphenyls are reported for the first time. Asperterphenyllin G exhibited cytotoxicity against nine cell lines with IC50 values ranging from 0.4 to 1.7 µM. Asperterphenyllin C showed antimicrobial activity against Proteus species with a MIC value of 19 µg/mL.

The Ubiquitin-Proteasome Pathway and Epigenetic Modifications in Cancer.

BACKGROUND: The ubiquitin-proteasome pathway is involved in almost all cellular processes (cell cycle, gene transcription and translation, cell survival and apoptosis, cell metabolism and protein quality control) mainly through the specific degradation of the majority of intracellular proteins (>80%) or partial processing of transcription factors (e.g., NF-κB). A growing amount of evidence now indicates that epigenetic changes are also regulated by the ubiquitin-proteasome pathway. Recent studies indicate that epigenetic regulations are equally crucial for almost all biological processes as well as for pathological conditions such as tumorigenesis, as compared to non-epigenetic control mechanisms (i.e., genetic alterations or classical signal transduction pathways). OBJECTIVE: Here, we reviewed the recent work highlighting the interaction of the ubiquitin-proteasome pathway components (e.g., ubiquitin, E1, E2 and E3 enzymes and 26S proteasome) with epigenetic regulators (histone deacetylases, histone acetyltransferases and DNA methyltransferases). RESULTS: Alterations in the regulation of the ubiquitin-proteasome pathway have been discovered in many pathological conditions. For example, a 2- to 32-fold increase in proteasomal activity and/or subunits has been noted in primary breast cancer cells. Although proteasome inhibitors have been successfully applied in the treatment of hematological malignancies (e.g., multiple myeloma), the clinical efficacy of the proteasomal inhibition is limited in solid cancers. Interestingly, recent studies show that the ubiquitin-proteasome and epigenetic pathways intersect in a number of ways through the regulation of epigenetic marks (i.e., acetylation, methylation and ubiquitylation). CONCLUSION: It is therefore believed that novel treatment strategies involving new generation ubiquitinproteasome pathway inhibitors combined with DNA methyltransferase, histone deacetylase or histone acetyltransferase inhibitors may produce more effective results with fewer adverse effects in cancer treatment as compared to standard chemotherapeutics in hematological as well as solid cancers.

A new p-terphenyl derivative from the fruiting bodies of Sarcodon imbricatus (L.) P. Karst.

A new p-terphenyl, 2',3'-diacetoxy-4,5,5',6',4'',5''-hexahydroxy-p-terphenyl (1), along with 12 known compounds were isolated from the fruiting bodies of Sarcodon imbricatus (Bankeraceae). Their structures were confirmed on the basis of extensive spectroscopic analysis and comparison with the spectral data in the literature. Compound 1 exhibited weak cytotoxicity against colon cancer SW480 and leukemia HL-60 cell lines, with IC50 values of 55.02 ± 1.79 µM and 44.71 ± 2.15 µM, respectively.

Cytotoxic p-terphenyls from the deep-sea-derived Aspergillus candidus.

From the deep-sea-derived fungus Aspergillus candidus, one novel (1) and three known (2-4) p-terphenyl derivates were isolated. The structure of the new compound was established mainly on the basis of extensive analysis of 1D and 2D NMR data. All four isolates were tested for in vitro anti-food allergic and antitumor bioactivities. Compounds 3 and 4 showed potent antiproliferative effect against four cancer cells of Hela, Eca-109, Bel-7402, and PANC-1 with IC50 values ranging from 5.5 µM to 9.4 µM.

p-Terphenyls and actinomycins from a Streptomyces sp. associated with the larva of mud dauber wasp.

In the course of searching for cytotoxic metabolites from insects associated actinomyces, two new natural p-terphenyl glycosides, strepantibin D (1) and strepantibin E (2), along with terferol (3), actinomycin D (4), actinomycin V (5) and actinomycin V0ß (6), were identified from the fermentation medium of a Streptomyces sp. which was obtained from the larva body of mud dauber wasp. Strepantibin D (1), previously reported as a synthetic derivative of terfestatin A, is firstly isolated as a natural p-terphenyl in this research. Strepantibin D (1) and terferol (3) showed medium cytotoxic activity against breast cancer cells MCF-7, MDA-MB-231 and BT-474. Actinomycins (4-6), especially actinomycin V (5), displayed remarkable cytotoxicity against breast cancer cells, with IC50 values ranging from 0.83 nM to 369.90 nM.

Ubiquitously specific protease 4 inhibitor-Vialinin A attenuates inflammation and fibrosis in S100-induced hepatitis mice through Rheb/mTOR signalling.

Inflammation and fibrosis are major consequences of autoimmune hepatitis, however, the therapeutic mechanism remains to be investigated. USP4 is a deubiquitinating enzyme and plays an important role in tissue fibrosis and immune disease. Vialinin A is an extract from mushroom and is a specific USP4 inhibitor. However, there is lack of evidences that Vialinin A plays a role in autoimmune hepatitis. By employing S100-induced autoimmune hepatitis in mice and AML12 cell line, therapeutic mechanism of Vialinin A was examined. Inflammation was documented by liver histological staining and inflammatory cytokines. Fibrosis was demonstrated by Masson, Sirius red staining and fibrotic cytokines with western blot and real-time RT-PCR. In experimental animal, there were increases in inflammation and fibrosis as well as USP4, and which were reduced after treatment of Vialinin A. Vialinin A also reduced Rheb and phosphorylated mTOR. Moreover, in LPS-treated AML12 cells, LPS-induced USP4, inflammatory and fibrotic cytokines, phosphorylated mTOR and Rheb. Specific inhibitory siRNA of USP4 reduced USP4 level and the parameters mentioned above. In conclusion, USP4 was significantly elevated in autoimmune hepatitis mice and Vialinin A reduced USP4 level and attenuate inflammation and fibrosis in the liver. The mechanism may be related to regulation of Rheb/mTOR signalling.

Structure-Activity Relationships and Potent Cytotoxic Activities of Terphenyllin Derivatives from a Small Compound Library.

A small library of 120 compounds was established with seventy new alkylated derivatives of the natural product terphenyllin, together with 45 previous reported derivatives and four natural p-terphenyl analogs. The 70 new derivatives were semi-synthesized and evaluated for cytotoxic activities against four cancer cell lines. Interestingly, 2',4''-diethoxyterphenyllin, 2',4,4''-triisopropoxyterphenyllin, and 2',4''-bis(cyclopentyloxy)terphenyllin showed potent activities with IC50 values in a range from 0.13 to 5.51 µM, which were similar to those of the positive control, adriamycin. The preliminary structure-activity relationships indicated that the introduction of alkyl substituents including ethyl, allyl, propargyl, isopropyl, bromopropyl, isopentenyl, cyclopropylmethyl, and cyclopentylmethyl are important for improving the cytotoxicity.

Terphenyl derivatives and terpenoids from a wheat-born mold Aspergillus candidus.

A new p-terphenyl derivative aspergicandidusin A (1), a new cleistanthane diterpenoid 6-deoxyaspergiloid C (13), and 12 known compounds (2-12, and 14) were isolated from the mold Aspergillus candidus. The structures of the new compounds were elucidated by spectral analysis of NMR and MS data. The absolute configuration of C-1 in 13 was determined via the circular dichroism data of the [Rh2(OCOCF3)4] complex. Compounds 2-8 and 11 showed moderate inhibitory activity against K562 cell lines with the IC50 value in the range from 17.9 to 46.3 µM. Compound 13 exhibited moderate cytotoxicity against HepG2 cells with the IC50 value of 47.7 µM. Compounds 11 and 12 exhibited moderate activity against the growth of S. aureus with MIC value of 6.25 µM, respectively.

Cytotoxic p-Terphenyls from a Marine-Derived Nocardiopsis Species.

Three new p-terphenyl derivatives, nocarterphenyls A-C (1-3), along with three known analogues (4-6) were isolated from the marine-derived actinobacterial strain Nocardiopsis sp. OUCMDZ-4936. Their structures were elucidated on the basis of spectroscopic analysis and a single-crystal X-ray diffraction experiment. Compounds 1 and 2 possess a benzothiazole and benzothiazine moiety, respectively, which are rare in the skeleton of p-terphenyls. Nocarterphenyl A (1) showed potent cytotoxic activity against the HL60 and HCC1954 cancer cell lines with the IC50 values of 0.38 and 0.10 µM among 26 human cancer cell lines.

TPP-related mitochondrial targeting copper (II) complex induces p53-dependent apoptosis in hepatoma cells through ROS-mediated activation of Drp1.

BACKGROUND: In recent years, copper complexes have gradually become the focus of potential anticancer drugs due to their available redox properties and low toxicity. In this study, a novel mitochondrion-targeting copper (II) complex, [Cu (ttpy-tpp)Br2] Br (simplified as CTB), is first synthesized by our group. CTB with tri-phenyl-phosphine (TPP), a targeting and lipophilic group, can cross the cytoplasmic and mitochondrial membranes of tumor cells. The present study aims to investigate how CTB affects mitochondrial functions and exerts its anti-tumor activity in hepatoma cells. METHODS: Multiple molecular experiments including Flow cytometry, Western blot, Immunofluorescence, Tracker staining, Transmission Electron Microscopy and Molecular docking simulation were used to elucidate the underlying mechanisms. Human hepatoma cells were subcutaneously injected into right armpit of male nude mice for evaluating the effects of CTB in vivo. RESULTS: CTB induced apoptosis via collapse of mitochondrial membrane potential (MMP), ROS production, Bax mitochondrial aggregation as well as cytochrome c release, indicating that CTB-induced apoptosis was associated with mitochondrial pathway in human hepatoma cells. Mechanistic study revealed that ROS-related mitochondrial translocation of p53 was involved in CTB-mediated apoptosis. Simultaneously, elevated mitochondrial Drp1 levels were also observed, and interruption of Drp1 activation played critical role in p53-dependent apoptosis. CTB also strongly suppressed the growth of liver cancer xenografts in vivo. CONCLUSION: In human hepatoma cells, CTB primarily induces mitochondrial dysfunction and promotes accumulation of ROS, leading to activation of Drp1. These stimulation signals accelerate mitochondrial accumulation of p53 and lead to the eventual apoptosis. Our research shows that CTB merits further evaluation as a chemotherapeutic agent for the treatment of Hepatocellular carcinoma (HCC).

Novel Metabolites from the Endophytic Fungus Chaetomium subaffine L01.

One natural p-terphenyl glycoside, gliocladinin C, and two furano-polyene derivatives, chaetominins A and B, were isolated from potato endophytic fungus Chaetomium subaffine. The absolute configurations of these compounds were elucidated by HR-ESI-MS, NMR, the DP4+ probabilities and electronic circular dichroism (ECD) spectra. Furthermore, gliocladinin C and chaetominin A showed cytotoxic activity against two selected human tumor cell lines (Hep-2 and HepG-2).

Inhibition of USP4 attenuates pathological scarring by downregulation of the TGF­ß/Smad signaling pathway.

Pathological scarring is a result of the hypertrophy of scar tissue during tissue repair following trauma. The aim of the present study was to assess the effect of ubiquitin­specific protease 4 (USP4) silencing on pathological scarring, and to evaluate the mechanistic basis for the effect. An MTT assay was used to assess cell viability. Immunoprecipitation (IP) was used to determine ubiquitination levels of the TGF­ß receptor (TßR)I and Smad7. Tumor formation was assessed by injecting keloid fibroblasts. Hematoxylin and eosin staining was used to detect pathological changes in tumor tissue. Reverse transcription quantitative polymerase chain reaction and western blot analysis assays were used to evaluate the expression levels of TßRI and Smad7. Compared with the untreated control animals, cell viability and the expression of TßRI and Smad7 increased significantly in animals treated with TGF­ß. Short hairpin RNA for USP4 (shUSP4) decreased the cell viability of negative control cells, TGF­ß­induced cellular proliferation, and the expression of TßRI and Smad7. IP experiments indicated that the ubiquitination level of TßRI was decreased following USP4 silencing. There was no remarkable difference in the structure of scar tissue among the various animal groups at 14 days following treatment, while the necrotic area of the scar tissue in the shUSP4 and vialinin A (USP inhibitor)­treated animals increased significantly at the 28th and 42nd day compared with the control animals. At days 14, 28 and 42, the expression levels of TßRI and Smad7 in the shUSP4 and vialinin A­treated animals were significantly decreased compared with the control animals (P<0.05). In summary, interference with or inhibition of USP4 prevented the activity of the TGF­ß/Smad pathway signaling and inhibited the formation of pathological scars.

Cytotoxic, antimicrobial and antiviral secondary metabolites produced by the plant pathogenic fungus Cytospora sp. CCTU A309.

Chemical analysis of extracts from cultures of the plant pathogenic fungus Cytospora sp. strain CCTU A309 collected in Iran led to the isolation of two previously unreported heptanedioic acid derivatives namely (2R,3S) 2-hydroxy-3-phenyl-4-oxoheptanedioic acid (1) and (2S,3S) 2-hydroxy-3-phenyl-4-oxoheptanedioic acid (2) as diastereomers, four previously undescribed prenylated p-terphenyl quinones 3-6 in addition to five known metabolites. Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. For metabolites 1 and 2, the absolute configurations at C-2 were deduced from comparison of the 1H NMR difference of their (S)- and (R)-phenylglycine methyl ester derivatives while the relative configurations were tentatively assigned by a J-based analysis and confirmed by comparison of 13C chemical shifts to literature data. The isolated compounds were tested for their cytotoxic, antimicrobial (including biofilm inhibition), antiviral, and nematicidal activities. While only moderate antimicrobial effects were observed, the terphenyl quinone derivatives 3-6 and leucomelone (10) exhibited significant cytotoxicity against the mouse fibroblast L929 and cervix carcinoma KB-3-1 cell lines with IC50 values ranging from 2.4 to 26 µg/mL. Furthermore, metabolites 4-6 showed interesting antiviral activity against hepatitis C virus (HCV).

Cytotoxic p-Terphenyls from the Endolichenic Fungus Floricola striata.

Eleven new p-terphenyls, floricolins K-U (1-11), together with 13 biosynthetically related known compounds (12-24) were isolated from an endolichenic fungus, Floricola striata. Their structures were elucidated by extensive spectroscopic analyses and single-crystal X-ray diffraction measurements. The newly isolated p-terphenyls inhibited the growth of A2780, MCF-7, and A549 cell lines. Further evaluation for the multidrug resistance (MDR) reversal activity of compound 5 revealed it enhanced the sensitivity of MCF-7/ADR cells toward adriamycin 39-fold at 10 µM through modulating P-glycoprotein-mediated drug exclusion.

Hawaiienols A-D, Highly Oxygenated p-Terphenyls from an Insect-Associated Fungus, Paraconiothyrium hawaiiense.

Four new highly oxygenated p-terphenyls, hawaiienols A-D (1-4), have been isolated from cultures of Paraconiothyrium hawaiiense, a fungus associated with the Septobasidium-infected insect Diaspidiotus sp.; their structures were elucidated primarily by NMR experiments. The absolute configurations of 1 and 2-4 were assigned by single-crystal X-ray diffraction analysis using Cu Kα radiation and via electronic circular dichroism calculations, respectively. Compound 1 incorporated the first naturally occurring 4,7-dioxatricyclo[3.2.1.03,6]octane unit in its p-terphenyl skeleton and showed cytotoxicity toward six human tumor cell lines.

Secondary Metabolites from the Root Rot Biocontrol Fungus Phlebiopsis gigantea.

Three cyclopentanoids (phlebiopsin A⁻C), one glycosylated p-terphenyl (methyl-terfestatin A), and o-orsellinaldehyde were isolated from the biocontrol fungus Phlebiopsis gigantea, and their structures were elucidated by 1D and 2D NMR spectroscopic analysis, as well as by LC-HRMS. The biological activity of the compounds against the root rot fungus Heterobasidion occidentale, as well as against Fusarium oxysporum and Penicillium canescens, was also investigated, but only o-orsellinaldehyde was found to have any antifungal activity in the concentration range tested.

Vialinin A, an Edible Mushroom-Derived p-Terphenyl Antioxidant, Prevents VEGF-Induced Neovascularization In Vitro and In Vivo.

Increased side toxicities and development of drug resistance are the major concern for the cancer chemotherapy using synthetic drugs. Therefore, identification of novel natural antioxidants with potential therapeutic efficacies is important. In the present study, we have examined how the antioxidant and anti-inflammatory activities of vialinin A, a p-terphenyl compound derived from Chinese edible mushroom T. terrestris and T. vialis, prevents human umbilical vascular endothelial cell (HUVEC) neovascularization in vitro and in vivo models. Pretreatment of HUVECs with vialinin A prevents vascular endothelial growth factor- (VEGF) induced HUVEC cell growth in a dose-dependent manner. Further, vialinin A also inhibits VEGF-induced migration as well as tube formation of HUVECs. Treatment of HUVECs prevents VEGF-induced generation of reactive oxygen species (ROS) and malondialdehyde (MDA) and also inhibits VEGF-induced NF-κB nuclear translocation as well as DNA-binding activity. The VEGF-induced release of various angiogenic cytokines and chemokines in HUVECs was also significantly blunted by vialinin A. Most importantly, in a mouse model of Matrigel plug assay, vialinin A prevents the formation of new blood vessels and the expression of CD31 and vWF. Thus, our results indicate a novel role of vialinin A in the prevention of neovascularization and suggest that anticancer effects of vialinin A could be mediated through its potent antioxidant and antiangiogenic properties.