Prognostic significance of MRP5 immunohistochemical expression in glioblastoma

Glioblastoma multiforme (GBM) is the most frequent malignant primary brain tumor in adults, exhibiting poor survival. The efficacy of chemotherapy is often limited by the development of multidrug resistance by the tumor cells. In the current study, we investigated the prognostic significance of the multidrug resistance protein 5 (MRP5) in patients with GBM. We retrospectively studied 33 patients with GBM treated with a combination of surgery, postoperative radiotherapy and adjuvant temozolomide chemotherapy. MRP5 protein expression was determined immunohistochemically and correlated with other prognostic factors and survival. The immunohistochemical expression of MRP5 was observed in 0-45% of tumor cells. Patients with MRP5 index > 11% exhibited significantly worse survival compared to those with MRP5 index a parts per thousand currency sign11 (10.5 vs. 18 months, p = 0.0002). Patients with Ki-67 index lower than 30% had longer survival (15 vs. 11 months, p = 0.0084). Furthermore, patients with a gross total tumor excision had better survival (p = 0.016). No significant difference was observed between preoperative Karnofsky performance score, age, gender and survival. In multivariate analysis, MRP5 index and the extent of tumor resection were identified as factors with independent prognostic power. The present results imply that MRP5 index may hold a prognostic role in patients with GBM.