Long-Term Recovery of Irradiated Prostate Cancer Increases Cancer Stem Cells

BACKGROUND. Despite improvements in treatment, prostate cancer (PC) remains the second-leading cause of cancer death in men. Radiotherapy is among the first-line treatments for PC, but a significant number of patients relapse. Recent evidence supports the idea that PC is initiated by a subset of cells, termed cancer stem cells (CSCs). CSCs have also been implicated in radioresistance in various malignancies, but their role in PC has not yet been investigated. METHODS. We compared the relative radiosensitivity of isolated CSCs to the total population of their corresponding cell lines, and examined the relative numbers of CSCs in irradiated cell lines following long-term recovery and in recurrent human PC. RESULTS. Here, we show that while irradiation does not immediately favor increased survival of CSCs, irradiated PC cell lines showed an increase in CSC properties with long-term recovery. These data suggest that, although CSCs are initially damaged by radiation, they possess a greater capacity for recovery and regrowth. CONCLUSIONS. The combination of radiotherapy with a CSC-targeted therapeutic strategy may prevent tumor recurrence. Prostate 72: 1746-1756, 2012. (C) 2012 Wiley Periodicals, Inc.