To explore a new combination of thermal treatment and gene therapy for hepatoma, a heat-inducible herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy system was developed in which thermal energy generated by Mn0.5Zn0.5Fe2O4 nanoparticles (MZF-NPs) under an alternating magnetic field was used to activate gene expression.
First, a recombinant eukaryotic plasmid, pHsp 70-HSV-TK, was constructed as a target gene for therapy. This recombinant plasmid was used to transfect SMMC-7721 hepatoma cells and the gene expression was evaluated. Magnet-induced heating was then applied to cells to assess the antihepatoma effects of the polyethylenimine (PEI)-MZF-NPs/pHsp 70-HSV-TK/GCV complex, in vitro and in vivo.
The results showed that cells were successfully transfected with pHsp 70-HSV-TK and that expression levels of HSV-TK remained stable. Both in vitro and in vivo results indicated that the combination of gene therapy and heat treatment resulted in better therapeutic effects than heating-alone group. The rates of apoptosis and necrosis in the combined treatment group were 49.0% and 7.21%, respectively. The rate of inhibition of cell proliferation in the combined treatment group was significantly higher (87.5%) than that in the heating-alone group (65.8%; P<0.01). The tumor volume and mass inhibition rates of the combined treatment group were 91.3% and 87.91%, respectively, and were significantly higher than the corresponding rates of the heating-alone group (70.41% and 57.14%; P<0.01). The expression levels of Stat3 and Bcl-xL messenger RNA and p-Stat3 and Bcl-xL protein in the combined treatment group were significantly lower than those in the other groups (P<0.01). The expression levels of Bax messenger RNA and protein in the recombinant plasmid group were significantly higher than those in the other groups (P<0.01).
It can therefore be concluded that the combined application of heat treatment and gene therapy has a synergistic and complementary effect and that PEI-MZF-NPs can simultaneously act both as a nonviral gene vector and a magnet-induced source of heat, thereby representing a viable approach for the treatment of cancer.