["3Y" problem and principle in gene therapy].

Somatic gene therapy based on nonviral and viral vectors is an attractive approach for treatment of human diseases. However,the application of gene therapy to human disease is currently hampered by potential hazards of methods of gene delivery,the relatively low efficiency and intracellular stability of target gene. Therefore,we summarized them as the "3Y" problems----(safety,efficacy and stability) and also think people should abide the "3Y" principles in gene therapy.