Enhancement of gene transfer efficiency in the Bcap-37 cell line by dimethyl sulphoxide and menthol.

Simple and efficient gene transfer into the nucleus would facilitate non-viral gene delivery. One promising method of non-viral gene delivery is to apply penetration enhancers. Chemicals, such as dimethyl sulfoxide (DMSO) and menthol, may have promise as non-toxic vehicles in improving gene transfer efficiency. In this study, the cytotoxic effects of DMSO and menthol were evaluated using MTT assays. Gene delivery efficiency in a human breast cancer cell line (Bcap-37) was investigated by quantitative PCR, fluorescence microscopy and flow cytometry. Non-toxic concentrations of DMSO (2%) and menthol (12.5 µM) enhanced the efficiency of liposome-mediated gene delivery in Bcap-37 cells. Quantitative PCR results showed that growth hormone (GH) mRNA expression in the post-menthol and pre-DMSO treatment groups was 10-fold higher compared to that in the liposome group, while in the pre-menthol and post-DMSO treatment groups, a 30-fold increase in GH mRNA expression was observed. Both DMSO and menthol treatments increased green fluorescent protein (GFP) expression efficiency as shown by fluorescence microscopy experiments. Compared to the liposome group, the number of positive cells in the pre-menthol and post-DMSO treatment groups was significantly increased by 15%. Furthermore, cell cycle analysis demonstrated that there were significant differences among the DMSO-treated group, the menthol-treated group and the normal group, which implied different effects of DMSO and menthol treatments. In conclusion, both non-toxic and harmless DMSO (2%) and menthol (12.5 µM) treatments improve gene transfer efficiency, while post-DMSO treatment may be the most effective protocol in increasing transgene expression efficiency.