title: Osteocalcin-directed gene therapy for prostate-cancer bone metastasis.
abstract: Osteocalcin (OC) is a major noncollagenous bone protein whose expression is limited almost exclusively to osteotropic tumors and mature calcified tissue (differentiated osteoblasts). The function of OC, a highly conserved gamma-carboxyglutamic acid-containing protein, relies in part on its ability to bind hydroxyapatite and act as a chemoattractant for bone-resorbing cells. Serum osteocalcin levels are used clinically as an index of active bone turnover. Research in our laboratory has revealed that OC is expressed in several solid tumors, including osteosarcoma and ovarian, lung, brain, and prostate cancers. Evidence arising from reverse-transcription polymerase chain reaction (RT-PCR; detection of OC mRNA), immunohistochemical staining (detection of OC protein), and transient transfection and reporter assay (detection of OC mRNA transcription) reveals that OC expression is up-regulated in numerous solid tumors, with its expression being further elevated in androgen-independent prostate cancers. A recombinant, replication-defective adenovirus, Ad-OC-TK (OC promoter-driven herpes-simplex-virus thymidine kinase) was constructed and, when combined with the appropriate prodrug, either ganciclovir (GCV) or acyclovir (ACV), was found to be effective at destroying prostate-cancer cell lines in vitro and prostate tumor xenografts in vivo in both subcutaneous and bone sites. Additionally, via use of the OC promoter the supporting bone stromal cells are cotargeted when the prostate cancer interdigitates with bone stroma at the metastatic skeletal sites. Thus, maximal tissue-specific cell toxicity is achieved by the interruption of cellular communication between the prostate cancer and the bone stroma. We describe herein the preclinical foundation as well as the design and implementation of an ongoing phase I clinical trial at the University of Virginia that targets androgen-independent metastatic prostate cancer using the Ad-OC-TK vector.
authors.affiliation: Department of Urology, University of Virginia Health Sciences System, Charlottesville 22908, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Koeneman
authors.forename: C
authors.initials: C
authors.lastname: Kao
authors.forename: S C
authors.initials: SC
authors.lastname: Ko
authors.forename: L
authors.initials: L
authors.lastname: Yang
authors.forename: Y
authors.initials: Y
authors.lastname: Wada
authors.forename: D F
authors.initials: DF
authors.lastname: Kallmes
authors.forename: J Y
authors.initials: JY
authors.lastname: Gillenwater
authors.forename: H E
authors.initials: HE
authors.lastname: Zhau
authors.forename: L W
authors.initials: LW
authors.lastname: Chung
authors.forename: T A
authors.initials: TA
authors.lastname: Gardner
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000368:Aged; D017209:Apoptosis; D001706:Biopsy; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary* / Q000628:therapy*; D001842:Bone and Bones / Q000473:pathology; D015331:Cohort Studies; D004848:Epithelium / Q000473:pathology; D015967:Gene Expression Regulation, Viral; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D020287:In Situ Nick-End Labeling; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000235:genetics*; D010957:Plasmids; D011471:Prostatic Neoplasms / Q000473:pathology*; D011877:Radionuclide Imaging; D017154:Stromal Cells / Q000473:pathology
chemical_list: D015675:Osteocalcin