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Objective:Intratumoral administration of adenoviral vector encoding herpes simplex virus(HSV)thymidine kinase(TK)gene(Ad-TK)followed by systemic ganciclovir(GCV)is an effective approach in treating experimental hepatocellular carcinoma(HCC).However,hepatotoxicity due to unwanted vector spread and suicide gene expression limited the application of this therapy.miR-122 is an abundant,liver-specific microRNA whose expression is decreased in human primary HCC and HCC-derived cell lines.These different expression profiles provide an opportunity to induce tumor-specific gene expression by miR-122 regulation.Methods:By inserting miR-122 target sequences(miR-122T)in the 3’untranslated region(UTR)of TK gene,we constructed adenovirus(Ad)vectors expressing miR-122-regulated TK(Ad-TK-122T)and report genes.After intratumoral administration of Ad vectors into an orthotopic miR-122-deficient HCC mouse model,we observed the miR-122-regulated transgene expression and assessed the antitumor activity and safety of Ad-TK-122T.Results:Insertion of miR-122T specifically down-regulated transgene expression in vitro and selectively protected the miR-122-positive cells from killing by TK/GCV treatment.Insertion of miR-122T led to significant reduction of tansgene expression in the liver without inhibition of its expression in tumors in vivo,resulting in an 11-fold improvement of tumor-specific transgene expression.Intratumoral injection of Ad vectors mediated TK/GCV system led to a vector dosage-dependent regression of tumor.The insertion of miR-122T does not influence the antitumor effects of suicide gene therapy.Whereas mice administrated with Ad-TK showed severe lethal hepatotoxicity at the effective therapeutic dose,no liver damage was found in Ad-TK-122T group.Conclusions:miR-122-regulated TK expression achieved effective anti-tumor effects and increased the safety of intratumoral delivery of adenovirus-mediated TK/GCV gene therapy for miR-122-deficient HCC.
Objective: Intratumoral administration of adenoviral vector encoding herpes simplex virus (HSV) thymidine kinase (TK) gene (Ad-TK) followed by systemic ganciclovir (antiviral therapy) is an effective approach in treating experimental hepatocellular carcinoma (HCC) unwanted vector spread and suicide gene expression limited the application of this therapy. miR-122 is an abundant, liver-specific microRNA whose expression is decreased in human primary HCC and HCC-derived cell lines. The different expression profiles provide an opportunity to induce tumors -specific gene expression by miR-122 regulation. Methods: By inserting miR-122 target sequences (miR-122T) in the 3’untranslated region (UTR) of TK gene, we constructed adenovirus (Ad) vectors expressing miR- TK (Ad-TK-122T) and report genes. After intratumoral administration of Ad vectors into an orthotopic miR-122-deficient HCC mouse model, we observed the miR-122-regulated transgene expression and evaluated the antitumor activity and safety of Ad-TK-122T. Results: Insertion of miR-122T specifically down-regulated transgene expression in vitro and selectively protected the miR-122-positive cells from killing by TK / GCV treatment. Insertion of miR-122T led to significant reduction of tansgene expression in the liver without inhibition of its expression in tumors in vivo, resulting in an 11-fold improvement of tumor-specific transgene expression. Intratumoral injection of Ad vectors mediated TK / GCV system led to a vector dosage-dependent regression of tumor The insertion of miR-122T does not affect the antitumor effects of suicide gene therapy. Western mice administrated with Ad-TK showed severe lethal hepatotoxicity at the effective therapeutic dose, no liver damage was found in Ad-TK-122T group. Conclusions: miR-122-regulated TK expression achieved effective anti-tumor effects and increased the safety of intratumoral delivery of adenovirus-mediated TK / GCV gene therapy for miR-122-deficient HCC.