Non-transmissible Sendai virus vector encoding c-myc suppressor FBP-interacting repressor for cancer therapy.
OBJECTIVE
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 SAP155 siRNA 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.


CONCLUSIONS
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.
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Kazuyuki
K
Matsushita
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Hideaki
H
Shimada
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Yasuji
Y
Ueda
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Makoto
M
Inoue
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Mamoru
M
Hasegawa
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Takeshi
T
Tomonaga
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Hisahiro
H
Matsubara
Kazuyuki Matsushita, Fumio Nomura, Department of Molecular Diagnosis, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Fumio
F
Nomura
D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D002470:Cell Survival; D003110:Colonic Neoplasms / Q000378:metabolism / Q000628:therapy*; D018076:DNA, Complementary / Q000378:metabolism; D016259:Genes, myc; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011714:Pyrans / Q000737:chemistry; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D029082:Sendai virus / Q000235:genetics*; D013141:Spiro Compounds / Q000737:chemistry
D018076:DNA, Complementary; C577426:FARP2 protein, human; D020662:Guanine Nucleotide Exchange Factors; D011714:Pyrans; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D013141:Spiro Compounds; C410595:poly-U binding splicing factor 60KDa; C553684:spliceostatin A; D049452:Green Fluorescent Proteins
Cancer gene therapy; Far up stream element-binding protein-interacting repressor; Sendai virus vector; c-myc suppressor