A gene therapy that restores tumor-suppressor gene expression, developed by University of Texas researchers, has become the first gene therapy to succeed in a U.S. phase III clinical trial.

The therapy uses a modified adenovirus that expresses the tumor-suppressing gene p53 for end-stage head and neck cancer. The p53 gene is inactivated in many types of cancer. Its normal role is to halt the division of a defective cell and then force the cell to kill itself.

The researchers deleted an important region of the adenovirus’ genome, preventing it from replicating, and installed a genomic segment that expresses p53. When injected into a tumor, the p53 adenovirus burrows into the cancer cell’s nucleus and expresses p53 (instead of replicating in a typical viral manner), resulting in cancer-cell death.

They are now working on p53 nanoparticles–wrapping the genes in tiny balls of fat that get taken up by the tumor–as another way to deliver p53 to tumors.

University of Texas M. D. Anderson Cancer Center News Release