Recombinant AAV-mediated HSVtk gene transfer with direct intratumoral injections and Tet-On regulation for implanted human breast cancer.
BACKGROUND
HSVtk/ganciclovir (GCV) gene therapy has been extensively studied in tumors and relies largely on the gene expression of HSVtk. Most studies, however, have failed to demonstrate any significant benefit of a controlled gene expression strategy in cancer treatment. The Tet-On system is commonly used to regulate gene expression following Dox induction. We have evaluated the antitumor effect of HSVtk/ganciclovir gene therapy under Tet-On regulation by means of adeno-associated virus-2 (AAV-2)-mediated HSVtk gene transfer with direct intratumoral injections in mice bearing breast cancer tumors.


METHODS
Recombinant adeno-associated virus-2 (rAAV) was constructed and transduced into MCF-7 cell line. GCV treatment to the rAAV infected MCF-7 cells was performed by MTT assay under the doxycycline (Dox) induction or without Dox induction at a vp (viral particle) number of > or =10(4)/cell. The virus was administered intratumorally to nude mice that had also received GCV intraperitoneally. The antitumor effects were evaluated by measuring tumor regression and histological analysis.


RESULTS
We have demonstrated that GCV treatment to the infected MCF-7 cells under the Dox induction was of more inhibited effects than those without Dox induction at > or =10(4) vp/cell. In ex vivo experiments, tumor growth of BALB/C nude mice breast cancer was retarded after rAAV-2/HSVtk/Tet-On was injected into the tumors under the Dox induction. Infiltrating cells were also observed in tumors after Dox induction followed by GCV treatment and cells were profoundly damaged. The expression of HSVtk gene in MCF-7 cells and BALB/C nude mice tumors was up-regulated by Tet-On under Dox induction with reverse transcription-PCR (RT-PCR) analysis.


CONCLUSIONS
The antitumor effect of rAAV-mediated HSVtk/GCV gene therapy under the Dox induction with direct intratumoral injections may be a useful treatment for breast cancer and other solid tumors.
Li
Zi-Bo
ZB
Molecular Biology Research Center, Xiangya Medical College, Central South University, Changsha, Hunan 410078, PR China. Lzb1022@hotmail.com
Zeng
Zhao-Jun
ZJ
Chen
Qian
Q
Luo
Sai-Qun
SQ
Hu
Wei-Xin
WX
D000230:Adenocarcinoma / Q000473:pathology / Q000628:therapy*; D000818:Animals; D000998:Antiviral Agents / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000473:pathology / Q000628:therapy*; D045744:Cell Line, Tumor; D000229:Dependovirus / Q000235:genetics*; D004318:Doxycycline / Q000494:pharmacology; D004790:Enzyme Induction; D005260:Female; D015774:Ganciclovir / Q000627:therapeutic use; D015967:Gene Expression Regulation, Viral / Q000187:drug effects; D005813:Genes, Synthetic; D041722:Genes, Transgenic, Suicide; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D015552:Injections, Intralesional; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D012045:Regulatory Sequences, Nucleic Acid; D018139:Simplexvirus / Q000201:enzymology*; D013937:Thymidine Kinase / Q000235:genetics* / Q000502:physiology; D023041:Xenograft Model Antitumor Assays
D000998:Antiviral Agents; D013937:Thymidine Kinase; D004318:Doxycycline; D015774:Ganciclovir