ABSTRACT
Cytisine-linked isoflavonoids (CLIFs) inhibited PC-3 prostate and LS174T colon cancer cell proliferation by inhibiting a peroxisomal bifunctional enzyme. A pull-down assay using a biologically active, biotin-modified CLIF identified the target of these agents as the bifunctional peroxisomal enzyme, hydroxysteroid 17ß-dehydrogenase-4 (HSD17B4). Additional studies with truncated versions of HSD17B4 established that CLIFs specifically bind the C-terminus of HSD17B4 and selectively inhibited the enoyl CoA hydratase but not the d-3-hydroxyacyl CoA dehydrogenase activity. HSD17B4 was overexpressed in prostate and colon cancer tissues, knocking down HSD17B4 inhibited cancer cell proliferation, suggesting that HSD17B4 is a potential biomarker and drug target and that CLIFs are potential probes or therapeutic agents for these cancers.
Subject(s)
Alkaloids/pharmacology , Antineoplastic Agents/pharmacology , Enzyme Inhibitors/pharmacology , Isoflavones/pharmacology , Peroxisomal Multifunctional Protein-2/antagonists & inhibitors , Alkaloids/chemistry , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Azocines/chemistry , Azocines/pharmacology , Cell Line, Tumor , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Humans , Isoflavones/chemical synthesis , Isoflavones/chemistry , Molecular Structure , Peroxisomal Multifunctional Protein-2/metabolism , Quinolizines/chemistry , Quinolizines/pharmacology , Structure-Activity RelationshipABSTRACT
Thymine DNA glycosylase (TDG) is a multifunctional protein that plays important roles in DNA repair, DNA demethylation, and transcriptional regulation. These diverse functions make TDG a unique enzyme in embryonic development and carcinogenesis. This review discusses the molecular function of TDG in human cancers and the previously unrecognized value of TDG as a potential target for drug therapy.
Subject(s)
DNA/genetics , Gene Expression Regulation, Developmental , Gene Expression Regulation, Neoplastic , Neoplasms/genetics , Thymine DNA Glycosylase/metabolism , Animals , Carcinogenesis , DNA Methylation , DNA Repair , Humans , Mice , Mutation , Neoplasms/metabolism , Protein Processing, Post-Translational , Substrate SpecificityABSTRACT
Wnt signaling plays important roles in development and tumorigenesis. A central question about the Wnt pathway is the regulation of ß-catenin. Phosphorylation of ß-catenin by CK1α and GSK3 promotes ß-catenin binding to ß-TrCP, leading to ß-catenin degradation through the proteasome. The phosphorylation and ubiquitination of ß-catenin have been well characterized; however, it is unknown whether and how a deubiquitinase is involved. In this study, by screening RNA interference (RNAi) libraries, we identified USP47 as a deubiquitinase that prevents ß-catenin ubiquitination. Inactivation of USP47 by RNAi increased ß-catenin ubiquitination, attenuated Wnt signaling, and repressed cancer cell growth. Furthermore, USP47 deubiquitinates itself, whereas ß-TrCP promotes USP47 ubiquitination through interaction with an atypical motif in USP47. Finally, in vivo studies in the Drosophila wing suggest that UBP64E, the USP47 counterpart in Drosophila, is required for Armadillo stabilization and plays a positive role in regulating Wnt target gene expression.
Subject(s)
Drosophila Proteins/physiology , Ubiquitin Thiolesterase/physiology , Ubiquitin-Specific Proteases/physiology , Ubiquitination , Wnt Signaling Pathway , beta Catenin/metabolism , Amino Acid Sequence , Animals , Binding Sites , Drosophila melanogaster , HEK293 Cells , Humans , Molecular Sequence Data , Proteolysis , Wings, Animal/enzymology , beta-Transducin Repeat-Containing Proteins/metabolismABSTRACT
Wnt signaling plays an important role in colorectal cancer (CRC). Although the mechanisms of ß-catenin degradation have been well studied, the mechanism by which ß-catenin activates transcription is still not fully understood. While screening a panel of DNA demethylases, we found that thymine DNA glycosylase (TDG) up-regulated Wnt signaling. TDG interacts with the transcription factor TCF4 and coactivator CREB-binding protein/p300 in the Wnt pathway. Knocking down TDG by shRNAs inhibited the proliferation of CRC cells in vitro and in vivo. In CRC patients, TDG levels were significantly higher in tumor tissues than in the adjacent normal tissues. These results suggest that TDG warrants consideration as a potential biomarker for CRC and as a target for CRC treatment.
Subject(s)
Colorectal Neoplasms/pathology , Thymine DNA Glycosylase/metabolism , Wnt Proteins/metabolism , Wnt Signaling Pathway , Amino Acid Sequence , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Cell Line, Tumor , Cell Proliferation , Gene Expression Regulation, Neoplastic , Humans , Peptide Fragments/metabolism , Protein Transport , Sialoglycoproteins/metabolism , Sumoylation , Thymine DNA Glycosylase/chemistry , Thymine DNA Glycosylase/genetics , Transcription Factor 4 , Transcription Factors/metabolism , Up-RegulationABSTRACT
We used a baculovirus expression system to express fusion proteins of HCV core, RGD (Arg-Gly-Asp) peptide, and IFN-α2a fragments in Sf9 cells. Western blotting and electron microscopy demonstrate that HCV core, peptides RGD, and IFN-α2a fusion proteins assemble into 30 to 40 nm nano-particles (virus-like particles, VLPs). Xenograft assays show that VLPs greatly reduced tumor volume and weight with regard to a nontreated xenograft. Migration and invasion results show that VLPs can inhibit the migration and invasion of the breast cancer cells MDA-MB231. This study will provide theoretical and experimental basis for the establishment of safe and effective tumor-targeted drug delivery systems and clinical application of VLPs carrying cell interacting cargo.
