Abstract
Radiotherapy is one of the established treatments for solid tumors. Investigation of tumor radioresistance is important for future tumor radiotherapy. Biological bases on the resistance have not been fully understood. Recent studies have demonstrated that there is a small fraction in solid tumor which is highly resistant to ionizing radiation and the radioresistant tumor cells often expressed some stem cell markers. Resistance of tumors to both radiation and chemotherapeutic agents can be attributed to the features of the cancer stem cells. In the present study, we show that a human glioblastoma cell line A172 transiently becomes to cancer stem cell-like when cultured with non-serum media which is supplemented with growth factors. The treated cell was found significantly resistant to X-rays and heavy ion particles (carbon) compared with the A172 cells cultured with the normal media. Phosphorylation of histon H2Ax was induced in both forms, however, recovered earlier in the stem cell-like population than in the parental cells. Our result is consistent with the hypothesis that cancer stemness causes radioresistance through the efficient activity of DNA double-strand break repair.
