ABSTRACT
Cancer stem cells (CSC) drive growth, therapy resistance, and recurrence in head and neck squamous cell carcinoma (HNSCC). Regulation of protein translation is crucial for normal stem cells and CSCs; its inhibition could disrupt stemness properties, but translation inhibitors are limited clinically due to toxicity. SVC112 is a synthetic derivative of bouvardin, a plant-derived translation elongation inhibitor. SVC112 had greater antiproliferative effects on HNSCC cells compared with the FDA-approved translation inhibitor omacetaxine mepesuccinate (HHT). SVC112 preferentially inhibited cancer cells compared with patient-matched cancer-associated fibroblasts, whereas HHT was equally toxic to both. SVC112 reduced sphere formation by cell lines and CSCs. SVC112 alone inhibited the growth of patient-derived xenografts (PDX), and SVC112 combined with radiation resulted in tumor regression in HPV-positive and HPV-negative HNSCC PDXs. Notably, CSC depletion after SVC112 correlated with tumor response. SVC112 preferentially impeded ribosomal processing of mRNAs critical for stress response and decreased CSC-related proteins including Myc and Sox2. SVC112 increased cell-cycle progression delay and slowed DNA repair following radiation, enhancing colony and sphere formation radiation effects. In summary, these data demonstrate that SVC112 suppresses CSC-related proteins, enhances the effects of radiation, and blocks growth of HNSCC PDXs by inhibiting CSCs. SIGNIFICANCE: Inhibiting protein elongation with SVC112 reduces tumor growth in head and neck squamous cell carcinoma and increases the effects of radiation by targeting the cancer stem cell pool.
Subject(s)
Head and Neck Neoplasms/therapy , Neoplastic Stem Cells/drug effects , Peptides, Cyclic/pharmacology , Protein Synthesis Inhibitors/pharmacology , Squamous Cell Carcinoma of Head and Neck/therapy , Animals , Cell Cycle/drug effects , Cell Cycle/radiation effects , Cell Line, Tumor , Chemoradiotherapy/methods , DNA Damage/radiation effects , DNA Repair/drug effects , Dose-Response Relationship, Radiation , Female , Head and Neck Neoplasms/pathology , Humans , Mice , Neoplasm Recurrence, Local , Neoplastic Stem Cells/radiation effects , Peptide Chain Elongation, Translational/drug effects , Peptides, Cyclic/chemistry , Protein Synthesis Inhibitors/therapeutic use , Radiotherapy Dosage , Squamous Cell Carcinoma of Head and Neck/pathology , Xenograft Model Antitumor AssaysABSTRACT
A chemoproteomics-based drug discovery strategy is presented that utilizes a highly parallel screening platform, encompassing more than 1000 targets, with a focused chemical library prior to target selection. This chemoproteomics-based process enables a data-driven selection of both the biological target and chemical hit after the screen is complete. The methodology has been exemplified for the purine binding proteome (proteins utilizing ATP, NAD, FAD). Screening of an 8000 member library yielded over 1500 unique protein-ligand interactions, which included novel hits for the oncology target Hsp90. The approach, which also provides broad target selectivity information, was used to drive the identification of a potent and orally active Hsp90 inhibitor, SNX-5422, which is currently in phase 1 clinical studies.
Subject(s)
Drug Evaluation, Preclinical/methods , HSP90 Heat-Shock Proteins/metabolism , Proteomics/methods , Adenosine Triphosphate/metabolism , Administration, Oral , Animals , Binding, Competitive , Clinical Trials, Phase I as Topic , Female , HSP90 Heat-Shock Proteins/antagonists & inhibitors , HSP90 Heat-Shock Proteins/chemistry , Humans , Mice , Models, Molecular , Molecular Conformation , Small Molecule Libraries/administration & dosage , Small Molecule Libraries/chemistry , Small Molecule Libraries/metabolism , Small Molecule Libraries/pharmacology , Substrate SpecificityABSTRACT
Double-stranded short interfering RNAs (siRNA) induce post-transcriptional silencing in a variety of biological systems. In the present study we have investigated the structural requirements of chemically synthesised siRNAs to mediate efficient gene silencing in mammalian cells. In contrast to studies with Drosophila extracts, we found that synthetic, double-stranded siRNAs without specific nucleotide overhangs are highly efficient in gene silencing. Blocking of the 5'-hydroxyl terminus of the antisense strand leads to a dramatic loss of RNA interference activity, whereas blocking of the 3' terminus or blocking of the termini of the sense strand had no negative effect. We further demonstrate that synthetic siRNA molecules with internal 2'-O-methyl modification, but not molecules with terminal modifications, are protected against serum-derived nucleases. Finally, we analysed different sets of siRNA molecules with various 2'-O-methyl modifications for stability and activity. We demonstrate that 2'-O-methyl modifications at specific positions in the molecule improve stability of siRNAs in serum and are tolerated without significant loss of RNA interference activity. These second generation siRNAs will be better suited for potential therapeutic application of synthetic siRNAs in vivo.
Subject(s)
Proto-Oncogene Proteins , RNA Interference , RNA, Small Interfering/chemistry , RNA, Small Interfering/genetics , Endoribonucleases/metabolism , HeLa Cells , Humans , Methylation , Oligonucleotides, Antisense/genetics , PTEN Phosphohydrolase , Phosphatidylinositol 3-Kinases/biosynthesis , Phosphatidylinositol 3-Kinases/genetics , Phosphoric Monoester Hydrolases/biosynthesis , Phosphoric Monoester Hydrolases/genetics , Protein Serine-Threonine Kinases/biosynthesis , Protein Serine-Threonine Kinases/genetics , Proto-Oncogene Proteins c-akt , RNA Stability , RNA, Double-Stranded/chemistry , RNA, Double-Stranded/genetics , Transfection , Tumor Suppressor Proteins/biosynthesis , Tumor Suppressor Proteins/geneticsABSTRACT
The pharmaceutical industry is currently facing several challenges to identify and develop novel drug targets. Traditional drug discovery focussed on a small number of well-characterized gene products. Recently, this picture has changed with the completion of the draft sequence of the human genome, which has led to the identification of thousands of novel genes with unknown or poorly understood function. To cope with this overwhelming number of potential drug target candidates, new strategies for the elucidation of gene function, as well as their involvement in intracellular pathways, are required.
