New Delivery System p53 Gene Holds Promise for Prostate Cancer Treatment

Researchers announced recently that they have developed a new system to deliver the p53 tumor suppressor gene directly into the tumor through the bloodstream. The system, when used in combination with radiotherapy and chemotherapy, may significantly improve treatment outcomes for prostate cancer patients. The findings were presented at the International Conference on Molecular Cancer Therapeutics sponsored by the American Association of Cancer Research (AACR), National Cancer Institute (NCI), and European Organization for Research and Treatment of Cancer (EORTC).

“Our data demonstrate that by introducing p53 in this new way, we can sensitize prostate tumors to radiation and chemotherapeutic agents. Also, by delivering the p53 gene directly into the bloodstream, we can increase the number of cancer cells that are targeted and reached—the cells of the actual tumor and those that may be roaming throughout the body,” said Kathleen F. Pirollo, PhD, research associate professor at the Lombardi Cancer Center at Georgetown University in Washington, DC.

Abnormalities in p53 have been found in the majority of human cancers. This gene is influential in causing apoptosis, and has been the focus of several studies attempting to introduce “normal” copies of the gene into cancer cells in order to stop the disease. The most common way of introducing the normal p53 gene into cancer cells is to use an adenovirus as a carrier. However, limitations to this method include the number of cells reached, the ability to target only the cancer cells, and possible adverse effects.

Three Compounds Comprise New Delivery System

The new delivery system uses a combination of three compounds—ligands, p53, and liposomes—in a carefully developed ratio to produce a small enough structure to penetrate into the small blood vessels in the tumor cells. Either folic acid or transferrin is used as the ligand since both are highly recognized by tumors and can attach easily to tumor cells.

The p53 gene is enclosed in a liposome, which, in turn, is attached to the ligand, and the combined entity is released into the blood to find its way to the cancer cells. When normal p53 is reintroduced into the cancer cells, these cells become more sensitive to common chemotherapy drugs and radiation therapy, thus destroying more of the tumor.