New techniques in molecular biology and increasing insights in the genetic
basis of tumorigenesis led to the development of therapeutic agents compose
d of genetic information. The majority of gene therapy trials is targeted t
owards cancer therapy. The most frequently used strategy is immunotherapy w
hich comprises transfer of genes encoding cytokines, costimulatory molecule
s or tumorspecific antigens to enable cells of the immune system to identif
y and destroy tumor cells. The second important strategy makes use of suici
de genes to selectively kill tumor cells. Compensation of genetic defects b
y the downregulation of activated oncogenes or the restoration of tumor sup
pressor gene functions is the third concept to revert the malignant phenoty
pe of cancer cells.