Frontiers in Suicide Gene Therapy of Cancer.

The National Cancer Institute (NCI) and the American Cancer Society (ACS) predict that 1,638,910 men and women will be diagnosed with cancer in the USA in 2012. Nearly 577,190 patients will die of cancer of all sites this year. Patients undergoing current systemic therapies will suffer multiple side effects from nausea to infertility. Potential parents, when diagnosed with cancer, will have to deposit oocytes or sperm prior to starting systemic radiation or chemo-therapy for the future genetic testing and in vitro fertilization, while trying to avoid risks of iatrogenic mutations in their germ cells. Otherwise, children of parents treated with systemic therapies, will be at high risk of developing genetic disorders. According to these predictions, this year will carry another, very poor therapeutic record again.The ultimate goal of cancer therapy is the complete elimination of all cancer cells, while leaving all healthy cells unharmed. One of the most promising therapeutic strategies in this regard is cancer suicide gene therapy (CSGT), which is rapidly progressing into new frontiers.The therapeutic success, in CSGT, is primarily contingent upon precision in delivery of the therapeutic transgenes to the cancer cells only. This is addressed by discovering and targeting unique or / and over-expressed biomarkers displayed on the cancer cells and cancer stem cells. Specificity of cancer therapeutic effects is further enhanced by designing the DNA constructs, which put the therapeutic genes under the control of the cancer cell specific promoters. The delivery of the suicidal genes to the cancer cells involves viral, as well as synthetic vectors, which are guided by cancer specific antibodies and ligands. The delivery options also include engineered stem cells with tropisms towards cancers. Main mechanisms inducing cancer cells' deaths include: transgenic expression of thymidine kinases, cytosine deaminases, intracellular antibodies, telomeraseses, caspases, DNases. Precautions are undertaken to eliminate the risks associated with transgenesis.Progress in genomics and proteomics should help us in identifying the cancer specific biomarkers and metabolic pathways for developing new strategies towards clinical trials of targeted and personalized gene therapy of cancer.