Gene therapy for thyroid cancer: current status and future prospects

Despite multimodality treatment for thyroid cancer, including surgical resection, radioiodine therapy, thyrotropin (TSH)-suppressive thyroxine treatment, and chemotherapy/radiotherapy, survival rates have not improved over the last decades. Therefore, development and evaluation of novel treatment strategies, including gene therapy, are urgently needed. A variety of gene therapy approaches have been evaluated for the treatment of follicular cell-derived and medullary thyroid cancer, including corrective gene therapy (p53 restoration, expression of a dominant negative RET mutant), cytoreductive gene therapy (suicide gene/prodrug strategy herpes simplex virus-thymidine kinase [HSV-tk]/ganciclovir, antiangiogenic therapy with endostatin) and immunomodulatory gene therapy (expression of interleukin (IL)-2 and IL-12). Furthermore, cloning of the sodium iodide symporter (NIS) gene has paved the way for the development of a novel cytoreductive gene therapy strategy based on NIS gene transfer followed by the application of radioiodine therapy ((131)I). NIS gene delivery into medullary and follicular cell-derived thyroid cancer cells has been shown to be capable of establishing or restoring radioiodine accumulation and might therefore represent an effective therapy for medullary and dedifferentiated thyroid tumors that lack iodide accumulating activity. The data summarized in this review article clearly demonstrate that the currently available strategies represent potentially curative novel therapeutic approaches for future gene therapy of thyroid cancer. The combination of different therapeutic genes has been demonstrated to be very useful to enhance therapeutic efficacy and seems to have a promising role at least as part of a multimodality approach for advanced thyroid cancer.