therapy examples include pro-apoptotic gene therapy, gene-directed prodrug
therapy, imaging/targeted radiotherapy and immunotherapy. Oncolytic viral
therapy places viral genes, which are critical for replication, under the
control of the hTERT gene promoter. This results in virus vectors that are
able to replicate only in cancer cells, and can then spread to adjacent
cancer cells on cell lysis. To date, most studies have taken advantage of
the versatile suicide gene therapy approach to use both the hTR and hTERT
promoters to regulate a wide variety of cell killing agents.