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Retrovirus-mediated suicide gene/prodrug therapy targeting thyroid carcinoma using a thyroid-specific promoter
V Braiden1, Y Nagayama, M Iitaka
1Department of Nature Medicine, Atomic Bomb Disease Institute, Nagasaki University School of Medicine, Japan.
Abstract:
To develop gene therapy targeting thyroid carcinoma, the recombinant retrovirus (LNTGTK) carrying herpes simplex virus thymidine kinase (HSV-TK) gene under the control of thyroglobulin (TG) promoter was constructed and its efficacy was investigated in 3 thyroid cell lines; a differentiated normal rat thyroid cell line (FRTL5), malignant rat thyroid carcinoma cells derived from FRTL5 (FRTC) and a human anaplastic thyroid carcinoma cell line (FRO). TG mRNA was detected by Northern blot analysis in FRTL5 cells and by RT-PCR in FRTC cells when cultured with 2 U/L TSH and its expression levels were decreased by TSH withdrawal. However, either methods revealed no TG expression in FRO cells. In vitro cytotoxic assays demonstrated TG expression status-dependent cell killing by transduction of LNTGTK followed by ganciclovir (GCV) treatment. Thus, LNTGTK transduction increased the GCV sensitivity approximately 13,000- and approximately 160-folds in the presence of TSH and approximately 4- and approximately 27-folds in the absence of TSH in FRTL5 and FRTC cells, respectively. In contrast, there was no difference in the GCV cytotoxicity between parental and transduced FRO cells. Significant growth inhibition, but not complete eradication, of transduced FRTC cells was observed in in vivo subcutaneous tumor models of nude mice. These results demonstrate that retrovirus-mediated transduction of HSV-TK gene under the control of the TG promoter confers the GCV sensitivity selectively to TG-expressing thyroid cells. This system may therefore be feasible for gene therapy targeting TG-expressing thyroid carcinomas.
Insights
Gene therapy for thyroid cancer uses a retrovirus to deliver the herpes simplex virus thymidine kinase (HSV-TK) gene. This approach selectively targets and increases sensitivity to ganciclovir in thyroglobulin-expressing thyroid cancer cells.
Area of Science:
- Molecular Biology
- Oncology
- Gene Therapy
Background:
- Thyroid carcinoma presents a significant challenge in cancer treatment.
- Gene therapy offers a promising avenue for targeted cancer treatment.
- Developing specific gene delivery systems for thyroid cancer is crucial.
Purpose of the Study:
- To construct a recombinant retrovirus (LNTGTK) for gene therapy targeting thyroid carcinoma.
- To evaluate the efficacy of the LNTGTK system in thyroid cell lines with varying thyroglobulin (TG) expression.
- To assess the potential of TG promoter-driven HSV-TK gene delivery for cancer treatment.
Main Methods:
- Construction of the LNTGTK retrovirus carrying the HSV-TK gene under the TG promoter.
- Analysis of TG mRNA expression in FRTL5, FRTC, and FRO thyroid cell lines using Northern blot and RT-PCR.
- In vitro cytotoxic assays with ganciclovir (GCV) treatment post-transduction.
- In vivo studies using subcutaneous tumor models in nude mice.
Main Results:
- TG expression was detected in FRTL5 and FRTC cells, but not in FRO cells.
- LNTGTK transduction followed by GCV treatment resulted in TG expression status-dependent cell killing.
- GCV sensitivity was significantly increased in TG-expressing cells (FRTL5 and FRTC), but not in non-expressing cells (FRO).
- In vivo studies showed significant growth inhibition of transduced FRTC cells.
Conclusions:
- Retrovirus-mediated transduction of the HSV-TK gene under the TG promoter selectively sensitizes TG-expressing thyroid cells to GCV.
- This gene therapy system demonstrates feasibility for targeting TG-expressing thyroid carcinomas.
- The TG promoter-driven HSV-TK gene therapy approach holds potential for future thyroid cancer treatment strategies.