抄録
Stress-induced senescence may play an important role as an acute, drug- or ionizing radiation(IR)-induced program along with interphase apoptosis and mitotic catastrophe. The aim of the study was to evaluate whether IR can induce senescence-like phenotype (SLP) associated with terminal growth arrest in the thyroid cancer cells, and if so, to evaluate impact of terminal growth arrest associated with SLP in intrinsic radiosensitivity of various thyroid carcinomas. The induction of SLP in thyroid cells were identified by: 1) SA- β -Gal staining method, 2) Dual flow cytometric analysis of cell proliferation and side light scatter using vital staining with PKH-2 dye, 3) Double labeling for 5-BrdUrd and SA- β -Gal. IR induced SLP associated with terminal growth arrest in ARO, FRO, KTC-2, NPA and TPC-1 thyroid cancer cells lines in time- and dose dependent manner. Analysis of relationship between induction of SLP and radiosensitivity revealed a trend in which more radioresistant cell lines strongly tended to show lower specific SLP yields (r=-0.93, p=0.068). We find out that SA- β -Gal staining is detectable in irradiated ARO xenotransplants, but not in control tumors. We, therefore, conclude that induction of SLP with terminal growth arrest contribute to the elimination of clonogenic populations after IR.
