title: A novel targeting modality for renal cell carcinoma: human osteocalcin promoter-mediated gene therapy synergistically induced by vitamin C and vitamin D₃.
abstract: BACKGROUND
  Advanced renal cell carcinoma (RCC) frequently develops skeletal metastasis and is highly resistant to conventional therapies. We hypothesized that the osteocalcin (OC) promoter may be a promising gene delivery system for RCC targeted gene therapy because osteotropic tumors gain osteomimetic properties and thrive in the new environment by exhibiting a bone-like gene expression profile. Human OC (hOC) expression is highly regulated by vitamins and hormone. In the present study, we tested the feasibility of vitamin-regulatable hOC promoter for RCC-specific transcriptional targeting, and examined the anti-tumor effect of vitamins C and D₃ with hOC-based adenoviral vectors towards RCC.
  
  
  METHODS
  Real-time reverse transcriptase-polymerase chain reaction measured OC expression induced by vitamins C and D₃, either alone or in combination, in RCC and normal human renal epithelial cells (HRE). The RCC-cytotoxic effects of concomitant vitamins and hOC promoter-based adenoviral vectors, Ad-hOC-TK and Ad-hOC-E1, were evaluated in both cell culture and a xenograft murine model.
  
  
  RESULTS
  We found that high doses of vitamin C induced H₂O₂-dependent apoptosis in RCC but not HRE. Treatment of RCC cells with combined vitamins C and D₃ treatment significantly increased OC promoter activity compared to single reagent treatment. Combined vitamin therapy reduced tumor size (85%) and complete tumor regression occurred in 38% of mice co-administrated Ad-hOC-E1.
  
  
  CONCLUSIONS
  The results obtained in the present study demonstrate that vitamins C and D₃ synergized with the anti-tumor effects of therapeutic genes driven by hOC promoter through direct cytotoxicity as well as transcriptional targeting. This combined gene therapy provides a promising modality for advanced RCC targeted therapy.
authors.affiliation: Department of Urology, Emory University, Atlanta, GA, USA.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Johnson
authors.forename: Bing-Hung
authors.initials: BH
authors.lastname: Chen
authors.forename: Shian-Ying
authors.initials: SY
authors.lastname: Sung
authors.forename: Chia-Hui
authors.initials: CH
authors.lastname: Liao
authors.forename: Wan-Chi
authors.initials: WC
authors.lastname: Hsiao
authors.forename: Leland
authors.initials: L
authors.lastname: W K Chung
authors.forename: Chia-Ling
authors.initials: CL
authors.lastname: Hsieh
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism*; D002292:Carcinoma, Renal Cell / Q000235:genetics / Q000628:therapy*; D045744:Cell Line, Tumor; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics / Q000628:therapy*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008819:Mice, Nude; D015675:Osteocalcin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014807:Vitamin D / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D015675:Osteocalcin; D014807:Vitamin D; D001205:Ascorbic Acid