Non-transmissible Sendai virus vector encoding c-myc suppressor FBP-interacting repressor for cancer therapy

AIM: To investigate a novel therapeutic strategy to target and suppress c-myc in human cancers using far up stream element (FUSE)-binding protein-interacting repressor (FIR).

AIM:To investigate a novel therapeutic strategy to target and suppress c-myc in human cancers using far up stream element(FUSE)-binding protein-interacting repressor(FIR).METHODS:Endogenous c-Myc suppression and apoptosis induction by a transient FIR-expressing vector was examined in vivo via a HA-tagged FIR(HA-FIR)expression vector.A fusion gene-deficient,non-transmissible,Sendai virus(SeV)vector encoding FIR cDNA,SeV/dF/FIR,was prepared.SeV/dF/FIR was examined for its gene transduction efficiency,viral dose dependency of antitumor effect and apoptosis induction in HeLa(cervical squamous cell carcinoma)cells and SW480(colon adenocarcinoma)cells.Antitumor efficacy in a mouse xenograft model was also examined.The molecular mechanism of the anti-tumor effect and c-Myc suppression by SeV/dF/FIR was examined using Spliceostatin A(SSA),a SAP155 inhibitor,or SAP155siRNA which induce c-Myc by increasing FIR△exon2 in HeLa cells.RESULTS:FIR was found to repress c-myc transcription and in turn the overexpression of FIR drove apoptosis through c-myc suppression.Thus,FIR expressing vectors are potentially applicable for cancer therapy.FIR is alternatively spliced by SAP155 in cancer cells lacking the transcriptional repression domain within exon 2(FIR△exon2),counteracting FIR for c-Myc protein expression.Furthermore,FIR forms a complex with SAP155 and inhibits mutual well-established functions.Thus,both the valuable effects and side effects of exogenous FIR stimuli should be tested for future clinical application.SeV/dF/FIR,a cytoplasmic RNA virus,was successfully prepared and showed highly efficient gene transduction in in vivo experiments.Furthermore,in nude mouse tumor xenograft models,SeV/dF/FIR displayed high antitumor efficiency against human cancer cells.SeV/dF/FIR suppressed SSA-activated c-Myc.SAP155 siRNA,potentially produces FIR△exon2,and led to c-Myc overexpression with phosphorylation at Ser62.HA-FIR suppressed endogenous c-Myc expression and induced apoptosis in HeLa and SW480 cells.A c-myc transcriptional suppressor FIR expressing SeV/dF/FIR showed high gene transduction efficiency with significant antitumor effects and apoptosis induction in HeLa and SW480 cells.CONCLUSION:SeV/dF/FIR showed strong tumor growth suppression with no significant side effects in an animal xenograft model,thus SeV/dF/FIR is potentially applicable for future clinical cancer treatment.