Delivery of "suicide" thymidine kinase gene of herpes virus in the complex with cationic peptide into human hepatoma cells in vitro

The delivery of "suicide" herpes simplex virus type-1 thymidine kinase gene (tk) into tumor cells, followed by treatment with synthetic nucleotide analogues (gancyclovir, acyclovir), is a perspective approach to cancer therapy. Serious limitations in employment of the existing means of gene delivery into target cells constitute the main obstacle for cancer gene therapy development. In the present work a possibility to use a nonviral gene delivery system is shown based on the employment of lysine rich peptide K8 and amphipathic peptide JTS-1 for transferring tk gene into human hepatoma HepG2 cells. Cationic peptide K8 forms compact complexes with plasmid DNA, and JTS-1 acts as a pH-dependent endosomal releasing agent. Transfection of HepG2 cells by tk expression vector coupled with K8/JTS-1 peptides, followed by acyclovir administration (50-100 micrograms/ml) for 24 h leads to cell cycle arrest in the G1/S checkpoint of some cells, which eventually die through apoptosis. Treatment of HepG2 cells with higher acyclovir concentration (200 micrograms/ml) additionally results in a nonspecific toxic effect. The above results demonstrate the efficacy of K8/JTS-1 delivery system for the "suicide" cancer gene therapy, and may be regarded as a basis for further elaboration of "suicide" cancer approaches in vivo.