A long-term clinical trial of suicide gene therapy has shown that it safely and effectively destroys prostate cancer cells. The method alters the genetic composition of cancer cells so that they trigger the immune system to kill them.
Researchers from Houston Methodist Hospital in Texas, led by Bin Teh, MD, enrolled 66 patients with prostate cancer in the trial. Patients with less advanced cancer received two rounds of gene therapy plus radiotherapy, whereas patients with more advanced cancer received three rounds of gene therapy plus radiation and hormonal therapy.
Prostate cancer patients that received suicide gene therapy and radiotherapy with or without hormonal therapy showed 5–20% improvement in 5-year overall survival compared with historical controls. The findings were published in Journal of Radiation Oncology.
The gene therapy technique used an adenovirus to incorporate a herpes virus gene that produces the enzyme thymidine kinase (TK) into the cancer cells’ DNA. This caused cancer cells to begin producing the TK enzyme, signaling the patient’s immune system to target and destroy the cells. As a second line of attack, the patients were also treated with the anti-herpes drug valacyclovir, which had a cytotoxic effect on the herpes virus–infected cancer cells.
The authors concluded, “The combination of immunomodulatory in situ gene therapy and IMRT with or without hormonal therapy is feasible, safe, and effective in the treatment of prostate cancer.” A randomized phase 3 trial has been initiated in order to confirm the study’s findings and to determine whether suicide gene therapy is better than radiotherapy alone.
