An oncolytic adenovirus selective for retinoblastoma tumor suppressor protein pathway-defective tumors: dependence on E1A, the E2F-1 promoter, and viral replication for selectivity and efficacy.
The use of oncolytic adenoviruses as a cancer therapeutic is dependent on the lytic properties of the viral life cycle, and the molecular differences between tumor cells and nontumor cells. One strategy for achieving safe and efficacious adenoviral therapies is to control expression of viral early gene(s) required for replication with tumor-selective promoter(s), particularly those active in a broad range of cancer cells. The retinoblastoma tumor suppressor protein (Rb) pathway is dysregulated in a majority of human cancers. The human E2F-1 promoter has been shown to be selectively activated/derepressed in tumor cells with a defect in the Rb pathway. Ar6pAE2fE3F and Ar6pAE2fF are oncolytic adenoviral vectors (with and without the viral E3 region, respectively) that use the tumor-selective E2F-1 promoter to limit expression of the viral E1A transcription unit, and, thus, replication, to tumor cells. We demonstrate that the antitumor activity of Ar6pAE2fF in vitro and in vivo is dependent on the E2F-1 promoter driving E1A expression in Rb pathway-defective cells, and furthermore, that its oncolytic activity is enhanced by viral replication. Selective oncolysis by Ar6pAE2fF was dependent on the presence of functional E2F binding sites in the E2F-1 promoter, thus linking antitumor viral activity to the Rb pathway. Potent antitumor efficacy was demonstrated with Ar6pAE2fF and Ar6pAE2fE3F in a xenograft model following intratumoral administration. Ar6pAE2fF and Ar6pAE2fE3F were compared with Addl1520, which is reported to be molecularly identical to an E1B-55K deleted vector currently in clinical trials. These vectors were compared in in vitro cytotoxicity and virus production assays, after systemic delivery in an in vivo E1A-related hepatotoxicity model, and in a mouse xenograft tumor model after intratumoral administration. Our results support the use of oncolytic adenoviruses using tumor-selective promoter(s) that are activated or derepressed in tumor cells by virtue of a particular defective pathway, such as the Rb pathway.
Jakubczak
John L
JL
Genetic Therapy, Inc, Gaithersburg, Maryland 20878, USA.
Ryan
Patricia
P
Gorziglia
Mario
M
Clarke
Lori
L
Hawkins
Lynda K
LK
Hay
Carl
C
Huang
Ying
Y
Kaloss
Michele
M
Marinov
Anthony
A
Phipps
Sandrina
S
Pinkstaff
Anne
A
Shirley
Pamela
P
Skripchenko
Yelena
Y
Stewart
David
D
Forry-Schaudies
Suzanne
S
Hallenbeck
Paul L
PL
D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017500:Adenovirus E1A Proteins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000628:therapy / Q000821:virology; D018797:Cell Cycle Proteins; D003588:Cytopathogenic Effect, Viral / Q000502:physiology; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000628:therapy / Q000821:virology; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009369:Neoplasms / Q000235:genetics / Q000628:therapy / Q000821:virology*; D011401:Promoter Regions, Genetic; D016160:Retinoblastoma Protein / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*; D014407:Tumor Cells, Cultured; D014779:Virus Replication; D023041:Xenograft Model Antitumor Assays
D017500:Adenovirus E1A Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; D016160:Retinoblastoma Protein; D014157:Transcription Factors