Combination of PEI-Mn_0.5Zn_0.5Fe₂O₄ nanoparticles and pHsp 70-HSV-TK/GCV with magnet-induced heating for treatment of hepatoma

Abstract

Background

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 Mn_0.5Zn_0.5Fe₂O₄ nanoparticles (MZF-NPs) under an alternating magnetic field was used to activate gene expression.

Methods

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.

Results

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).

Conclusion

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.

Keywords:

• Mn_0.5Zn_0.5Fe₂O₄ nanoparticles
• heat-inducible gene expression
• hyperthermia
• gene therapy
• HSV-TK/GCV
• SMMC-7721 hepatoma cells

Acknowledgments

This work was supported by the National Key Basic Research Program of China (973 Program) (2013 CB933904), the Natural Science Foundation of Jiangsu Province (BK2012335), and the National Natural Science Foundation of China (81271635, 81071881, and 81201131).

Disclosure

The authors report no conflicts of interest in this work.