Researchers from Princess Margaret Hospital (PMH) have identified a new enzyme that affects radiation response in patients suffering from head and neck cancer. PMH researchers have made a discovery that may be significant in controlling the side effects for cancer patients. They have discovered that targeting an enzyme called Uroporphyrinogen Decarboxylase (UROD) can sensitize diseased tissue to radiation and chemotherapy.

UROD has been identified as a key ingredient in human cancers and the study suggests that targeting UROD can selectively enhance the effects of radiotherapy and chemotherapy in cancerous tumors of head and neck while minimizing toxicity to normal tissues. These findings have been published in Science Translational Medicine.

Chief investigator, Dr. Fei-Fei Liu (Professor of Radiation Oncology at the University of Toronto and PMH, and Senior Scientist at the Ontario Cancer Institute and The Campbell Family Cancer Research Institute) states that analysis of patient biopsies disclosed that UROD levels were higher in tumor tissues than in the normal ones. UROD can be used to make a general prediction of how will a patient respond to radiation therapy since the cancer patients with lower UROD levels prior to radiation treatment had improved clinical outcome.

Dr. Emma states that lower doses of radiation and chemotherapeutic drugs could be administered to cancer patients without affecting the treatment efficacy. Dr. Liu says that UROD is an enzyme that participates in production of a molecule called heme that is vital to all body organs. Targeting UROD creates an opportunity to exploit the heme synthesis pathway that disrupts the equilibrium of iron and free radical levels in cells which thereby kills cancer cells.