ABSTRACT
Human respiratory syncytial virus (hRSV) is a leading cause of acute lower respiratory tract infection in infants, elderly and immunocompromised individuals. To date, no specific antiviral drug is available to treat or prevent this disease. Here, we report that the Smoothened receptor (Smo) antagonist cyclopamine acts as a potent and selective inhibitor of in vitro and in vivo hRSV replication. Cyclopamine inhibits hRSV through a novel, Smo-independent mechanism. It specifically impairs the function of the hRSV RNA-dependent RNA polymerase complex notably by reducing expression levels of the viral anti-termination factor M2-1. The relevance of these findings is corroborated by the demonstration that a single R151K mutation in M2-1 is sufficient to confer virus resistance to cyclopamine in vitro and that cyclopamine is able to reduce virus titers in a mouse model of hRSV infection. The results of our study open a novel avenue for the development of future therapies against hRSV infection.
Subject(s)
Respiratory Syncytial Virus, Human/physiology , Transcription, Genetic , Viral Proteins/metabolism , Virus Replication/physiology , Alkaloids/pharmacology , Animals , Cell Line , DNA-Directed RNA Polymerases/metabolism , Disease Models, Animal , Drug Resistance, Viral/drug effects , Female , Gene Expression Regulation, Viral/drug effects , Humans , Mice, Inbred BALB C , Models, Molecular , Respiratory Syncytial Virus Infections/drug therapy , Respiratory Syncytial Virus Infections/virology , Respiratory Syncytial Virus, Human/drug effects , Smoothened Receptor/metabolism , Transcription, Genetic/drug effects , Veratrum/chemistry , Veratrum Alkaloids/chemistry , Veratrum Alkaloids/pharmacology , Veratrum Alkaloids/therapeutic use , Virus Replication/drug effects , Virus Replication/geneticsABSTRACT
Enhanced sensitivity to Wnts is an emerging hallmark of a subset of cancers, defined in part by mutations regulating the abundance of their receptors. Whether these mutations identify a clinical opportunity is an important question. Inhibition of Wnt secretion by blocking an essential post-translational modification, palmitoleation, provides a useful therapeutic intervention. We developed a novel potent, orally available PORCN inhibitor, ETC-1922159 (henceforth called ETC-159) that blocks the secretion and activity of all Wnts. ETC-159 is remarkably effective in treating RSPO-translocation bearing colorectal cancer (CRC) patient-derived xenografts. This is the first example of effective targeted therapy for this subset of CRC. Consistent with a central role of Wnt signaling in regulation of gene expression, inhibition of PORCN in RSPO3-translocated cancers causes a marked remodeling of the transcriptome, with loss of cell cycle, stem cell and proliferation genes, and an increase in differentiation markers. Inhibition of Wnt signaling by PORCN inhibition holds promise as differentiation therapy in genetically defined human cancers.