Pilot study examining tumor expression of RAD51 and clinical outcomes in human head cancers

Abstract

Radiation therapy and chemotherapy are commonly used treatments for head and neck cancer. RAD51 is a highly conserved DNA repair protein that serves a central function in the homologous recombination pathway. High levels of RAD51 protein expression have been reported in number of human cancer cell lines, and studies suggest that RAD51 overexpression can increase cellular resistance to radiation and some chemotherapeutic drugs. In this study, RAD51 protein levels were quantified by immunohistochemistry in tumor samples from twelve head and neck cancer patients who received identical treatment with induction chemotherapy (paclitaxel and carboplatinum) followed by radiation therapy given concurrently with additional chemotherapy (paclitaxel, fluorouracil, hydroxyurea). Patients with high RAD51 protein levels in their pre-treatment tumor biopsies demonstrated poorer cancer-specific survival rates than patients with lower RAD51 levels (33.3% vs. 88.9% at 2 years; p=0.025). In addition, within a subgroup of patients with normal tumor cell p53 expression, there was a non-significant trend toward better induction chemotherapy response rates observed in the tumors with lower RAD51 protein levels. These results suggest that tumor cell RAD51 expression levels may influence the outcome of patients with head and neck cancer treated with chemotherapy and radiotherapy.