Abstract
IntroductionDespite recent improvements in the survival rates for nasopharyngeal carcinoma (NPC), novel treatment strategies are required to improve distant metastasis-free survival. The sodium iodine symporter (NIS) gene has been applied for in vivo imaging and cancer therapy. In this study, we examined the potential of NIS gene therapy as a therapeutic approach in NPC by performing non-invasive imaging using 125I and 131I therapy in vivo.MethodsWe constructed a lentiviral vector expressing NIS and enhanced green fluorescent protein (EGFP) under the control of the human elongation factor-1α (EF1α) promoter, and stably transfected the vector into CNE-2Z NPC cells to create CNE-2Z-NIS cells. CNE-2Z and CNE-2Z-NIS tumor xenografts were established in nude mice; 125I uptake, accumulation and efflux were measured using micro-SPECT/CT imaging; the therapeutic effects of treatment with 131I were assessed over 25 days by measuring tumor volume and immunohistochemical staining of the excised tumors.ResultsqPCR, immunofluorescence and Western blotting confirmed that CNE-2Z-NIS cells expressed high levels of NIS mRNA and protein. CNE-2Z-NIS cells and xenografts took up and accumulated significantly more 125I than CNE-2Z cells and xenografts. In vitro, 131I significantly reduced the clonogenic survival of CNE-2Z-NIS cells. In vivo, 131I effectively inhibited the growth of CNE-2Z-NIS xenografts. At the end of 131I therapy, CNE-2Z-NIS xenograft tumor cells expressed higher levels of NIS and caspase-3 and lower levels of Ki-67.ConclusionLentiviruses effectively delivered and mediated long-lasting expression of NIS in CNE-2Z cells which enabled uptake and accumulation of radioisotopes and provided a significant therapeutic effect in an in vivo model of NPC. NIS-mediated radioiodine treatment merits further investigation as a potentially effective, low toxicity therapeutic strategy for NPC.
Highlights
Despite recent improvements in the survival rates for nasopharyngeal carcinoma (NPC), novel treatment strategies are required to improve distant metastasis-free survival
We examined the potential of NIS gene therapy as a therapeutic approach in NPC by performing non-invasive imaging using 125I and 131I therapy in vivo
Due to improved radiotherapy techniques and chemotherapy strategies, the 5-year survival rate for NPC has increased from 50% in the 1980s to 80% at present [2]
Summary
We constructed a lentiviral vector expressing NIS and enhanced green fluorescent protein (EGFP) under the control of the human elongation factor-1α (EF1α) promoter, and stably transfected the vector into CNE-2Z NPC cells to create CNE-2Z-NIS cells. Lv-EF1α-OCT4-IRES-EGFP was kindly provided by the Institute of Molecular Biology, Chinese Academy of Sciences; pcDNA3.1-NIS was obtained from our own library [11]. HEK293T cell line (Cell Bank of the Chinese Academy of Science, Shanghai, China) was cultured in RPMI-1640 medium supplemented with 10% FBS(Fetal Bovine Serum) and 1% penicillin/streptomycin. Virus particles were generated by cotransfection of HEK293T cells with Lv-EF1α-NISIRES-EGFP and the three packaging plasmids pRsv-REV, pMDIg-pRRE and pMD2G (Biovector Science Lab, Beijing, China). The virus particles were harvested by collecting the cell culture medium at 48 h post-transfection; the supernatants were filtered through 0.45 μm filters, centrifuged at 10,000 g for 15 min and the resulting pellet was resuspended in 100 μl culture medium.
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