title: A novel, conditionally replicative adenovirus for the treatment of breast cancer that allows controlled replication of E1a-deleted adenoviral vectors.
abstract: The efficiency of gene therapy strategies against cancer is limited by the poor distribution of the vectors in the malignant tissues. To solve this problem, a new generation of tumor-specific, conditionally replicative adenoviruses is being developed. To direct the replication of the virus to breast cancer, we have considered one characteristic present in a great proportion of these cancers, which is the expression of estrogen receptors (ERs). On the basis of the wild-type adenovirus type 5, we have constructed a conditionally replicative adenovirus (Ad5ERE2) in which the E1a and E4 promoters have been replaced by a portion of the pS2 promoter containing two estrogen-responsive elements (EREs). This promoter induces transcriptional activation of the E1a and E4 units in response to estrogens in cells that express the ERs. Ad5ERE2 is able to kill ER(+) human breast cancer cell lines as efficiently as the wild-type virus, but has decreased capacity to affect ER(-) cells. By complementation of the E1a protein in trans, Ad5ERE2 allows restricted replication of a conventional E1a-deleted adenoviral vector. When a virus expressing the proapoptotic gene Bc1-xs (Clarke et al., Proc. Natl. Acad. Sci. U.S.A. 1995;92:11024-11028) is used in combination with Ad5ERE2, the ability of both viruses to induce cell death is dramatically increased, and the effect can be modulated by addition of the antiestrogen tamoxifen.
authors.affiliation: Department of Internal Medicine, University of Michigan Comprehensive Cancer Center, Ann Arbor, MI 48109, USA.
authors.forename: R
authors.initials: R
authors.lastname: Hernandez-Alcoceba
authors.forename: M
authors.initials: M
authors.lastname: Pihalja
authors.forename: M S
authors.initials: MS
authors.lastname: Wicha
authors.forename: M F
authors.initials: MF
authors.lastname: Clarke
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D017500:Adenovirus E1A Proteins / Q000235:genetics*; D017504:Adenovirus E4 Proteins / Q000235:genetics; D000818:Animals; D001943:Breast Neoplasms / Q000628:therapy*; D016923:Cell Death; D004967:Estrogens / Q000235:genetics / Q000494:pharmacology; D005260:Female; D017353:Gene Deletion; D017930:Genes, Reporter; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008957:Models, Genetic; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011960:Receptors, Estrogen / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D013629:Tamoxifen / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D017500:Adenovirus E1A Proteins; D017504:Adenovirus E4 Proteins; D004967:Estrogens; D011960:Receptors, Estrogen; D013629:Tamoxifen; D008156:Luciferases