In contrast to other enzymes, Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) has a broad substrate specificity and high catalytic rate when transferred in human cells. This makes it a promising therapeutic agent when administered together with several cytotoxic nucleoside analogs, such as gemcitabine 2',2'-difluoro-deoxycytidine (dFdC). Therefore, lentiviral vectors, which potentially allow stable long-term transgene expression, are good candidates for gene delivery vehicles. In the present study, we successfully developed a lentivirus-mediated transgene expression system of Dm-dNK under the control of hTERT promoter against the breast cancer cell line (Bcap37), the gastric cancer cell line (SGC7901) and the normal fibroblast cell line (WI-38). Moreover, we also analyzed its targeted cytotoxicity in vitro with treatment of the prodrug dFdC. Bcap37 tumor growth was inhibited in nude mice. Both cancer cell lines exhibited apparent cytotoxicity when infected with recombinant lentivirus constructs expressing Dm-dNK. In contrast, lentivirus-infected WI-38 cells exhibited less cytotoxicity. These data suggested that Dm-dNK was sensitive to dFdC, and it resulted in synergistic growth inhibition and apoptosis induction in vitro. In addition, Lenti-hTERT-dNK/dFdC also suppressed tumor growth in vivo. Our results suggest that the Lenti-hTERT-dNK/dFdC system is a safe and feasible treatment strategy in the development of suicide gene therapy.
Gene transfer using different viral vectors has demonstrated different antitumor effects in suicide gene therapy. In the present study, in order to optimize the efficacy of replication-defective adenoviral and lentiviral vectors for gene therapy, RT-PCR was used to evaluate the expression of Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) in the Bcap37 human breast cancer cell line, dThd was used to determine the activity of Dm-dNK, cell cytotoxicity was evaluated by MTT assay and cell proliferation was assessed using a hemocytometer. Moreover, apoptosis induction was evaluated by the Annexin V-FITC-labeled FACS method. Furthermore, BALB/C nude mice bearing tumors were treated with Dm-dNK mediated with the pyrimidine nucleoside analog, brivudine [BVDU, (E)-5-(2-bromovinyl)-2'-deoxyuridine]. Our results indicated that the gene expression of Dm-dNK transfected by adenoviral and lentiviral vectors may be detected and that its long-term activity may be retained. Both vectors containing the Dm-dNK gene revealed high cytotoxicity and sensitized cell apoptosis from the BVDU prodrug. In tumor models, lentivirus-mediated gene therapy significantly inhibited the growth of tumors compared with adenovirus-mediated gene therapy. Although adenovirus- and lentivirus-transduced Dm-dNK reveal strong treatment efficacy in vitro, the latter has great potential due to the long-term expression of the therapeutic gene in vivo.
Background: Nova Circular RNA (circRNA) of non-coding RNA has gradually become an important regulatory factor, and it has made people attach great concern over the occurrence and development of many diseases, particularly carcinomas. circ_RPPH1 is a newly discovered circRNA. Gene Expression Omnibus (GEO) analysis showed that there are high contents of circ_RPPH1 in breast cancer (BC), but the mechanism of circRNA in BC remains unclear. Methods: Real-time quantitative PCR (qRT-PCR) was applied to test the role of circ_RPPH1 in BC patients, and functional experiments were applied to test the role of circ_RPPH1 on BC tumor. Fluorescence in situ hybridization, double luciferase reporter gene analysis, RNA pull-down and RNA immunoprecipitation experiments were performed to explore the correlation of circ_RPPH1 with miR-146b-3p/E2F2 in BC. Results: circ_RPPH1 was evidently enhanced in BC, and its content was related to the clinical stage and pathological grade. circ_RPPH1 can accelerate the proliferation, migration and invasion, and promote tumorigenesis and metastasis. Mechanism exploration indicated that circ_RPPH1 acted as ceRNA (competing endogenous RNA) of miR-146b-3p, so as to reduce the inhibitory role of miR-146b-3p on its target E2F2. Conclusion: Circ_RPPH1/miR-146b-3p/E2F2 axis can promote the progression of BC, and it might be a latent therapeutic target for clinical BC.
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