Impact of holmium:YAG and neodymium:YAG lasers on the efficacy of DNA delivery in transitional cell carcinoma.

New approaches in the treatment of transitional cell carcinoma (TCC) are using gene therapy to influence the disease at the genetic level. Technical advances in genomics, the availability of tissue-specific gene promoters and other developments have made this approach more realistic. Transporting the gene into the target cell is still the major problem. Several transfection techniques have been introduced. Transfection of naked DNA is one of the simplest to perform but transfection rates have been very poor. We investigated the influence of laser energy on transfection efficacy in urothelial cancer cells in vitro with two types of medical lasers. A suspension of human transitional cancer cells (UM-UC3; 3.5 million cells/ml) was mixed with 200 microg of plasmid DNA (pEGFP-N1). Two types of laser energy, neodymium:YAG (Nd:YAG) and holmium:YAG (Ho:YAG), were applied to the cell suspension in different energy settings. Twenty four hours after treatment, transfection rates were measured with FACS analysis. Energy setting parameters that determine the efficacy of laser were investigated. The significance of different transfection rates was estimated with the student's t-test. We demonstrated that the Nd:YAG laser was not suitable for achieving significant transfection of the reporter gene to the cells. In contrast, the Ho:YAG laser produced satisfactory transfection rates. There was an increase in transfection with increasing frequency of laser pulses, from 16% with 2 Hz up to 40% with 10 Hz (p < 0.0005). Pulse frequency was therefore stabilised at 10 Hz. Pulse energy (mJ) showed the same dependency: a transfection rate of 18.3% was achieved with 1,000 mJ and 53.8% with 2,000 mJ (p > 0.0005). Additionally, we investigated the impact of total pulse number (imp) with different pulse energies. At 1,000 mJ, a transfection rate of 18.3% was estimated with 200 imp and 48.56% with 750 imp, (p < 0.0005). At 2,000 mJ, a transfection rate of 53.8% was achieved with 200 imp and 58.26% with 500 imp. The optimal laser setting observed in this experiment was 10 Hz, 2,000 mJ and 500 imp. This study indicates that the efficacy of naked DNA delivery into TCC in vitro is improvable by application of Ho:YAG laser energy. The Nd:YAG laser did not increase transfection rates in our model. Our results with the Ho:YAG laser are encouraging for further studies to optimise DNA delivery. As TCC tissue is relatively easy to access, this method could become an effective and minimally invasive procedure in urothelial cancer treatment.