Gene therapy of thyroid cancer via retrovirally-driven combined expression of human interleukin-2 and herpes simplex virus thymidine kinase.
OBJECTIVE
Based on our clinical experience with combined gene therapy of glioblastoma, we developed a retroviral vector expressing two therapeutic genes (i.e. thymidine kinase of herpes simplex virus, HSV-TK, and interleukin-2, IL-2) and evaluated its efficiency in vitro and in vivo.


METHODS
Expression of therapeutic genes in transduced thyroid carcinoma cells was analyzed by real-time RT-PCR. Ganciclovir sensitivity of infected cells was assessed in vitro in thyroid carcinoma cell lines and in vivo in nude mice bearing xenografted thyroid cancers. The combined effect of IL-2/HSV-TK was compared with the effect of IL-2 alone.


RESULTS
Expression of therapeutic genes was higher in differentiated than in anaplastic thyroid carcinoma cells. Ganciclovir treatment led to dose- and time-dependent killing of transduced cells in vitro. A bystander effect was demonstrated by using mixtures of infected and non-infected cells. In vivo studies showed a significant reduction of growth and the presence of an inflammatory infiltrate in transduced thyroid tumors expressing IL-2 alone, as compared with non-infected tumors. By using the retroviral vector expressing IL-2/HSV-TK, treatment with ganciclovir led to complete eradication of anaplastic tumors and a >80% reduction of the size of differentiated thyroid carcinomas. Histological analysis of tumor specimens showed extensive necrosis and inflammatory cell infiltrates. The combination of IL-2/HSV-TK plus ganciclovir was significantly more efficient than IL-2 alone in eradicating tumor masses. The bystander effect was also obtained in vivo.


CONCLUSIONS
These findings demonstrate the feasibility and efficiency of a combined immunomodulating and suicide gene therapy approach for thyroid carcinomas.
Barzon
Luisa
L
Department of Histology, Microbiology and Medical Biotechnologies, University of Padova, Via Gabelli 63, I-35121 Padova, Italy.
Bonaguro
Roberta
R
Castagliuolo
Ignazio
I
Chilosi
Marco
M
Franchin
Elisa
E
Del Vecchio
Claudia
C
Giaretta
Ilaria
I
Boscaro
Marco
M
Palù
Giorgio
G
D016475:3T3 Cells; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism*; D000998:Antiviral Agents / Q000494:pharmacology; D015774:Ganciclovir / Q000494:pharmacology; D015967:Gene Expression Regulation, Viral; D015316:Genetic Therapy; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D012190:Retroviridae / Q000187:drug effects / Q000235:genetics*; D018139:Simplexvirus / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000628:therapy*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000502:physiology
D000970:Antineoplastic Agents; D000998:Antiviral Agents; D007376:Interleukin-2; D013937:Thymidine Kinase; D015774:Ganciclovir