Figure 4.

(a–d) Representative figures of hyperinduced autophagic cells by a single dose of 10-Gy X-rays in parental HepG2 and radioresistant HepG2-8960-R cells. Autophagosomes were immunocytochemically visualized by anti-LC-3 antibody and cells filled with autophagosomes were counted as hyperinduced autophagic cells (arrows). (e–h) Electron microscopic analysis of HepG2 and HepG2-8960-R. (a) Hyperinduced autophagic cells were seldom observed in HepG2 cells without irradiation. (b) At day 7 after exposure to 10 Gy of X-rays, the level of hyperinduced autophagic HepG2 cells was 78.2±6.1%. (c) HepG2-8960-R cells 2 days after the last maintenance irradiation (2 Gy per day). (d) At day 7 after exposure to 10 Gy of X-rays, significant induction of hyperinduced autophagic cells was not observed in HepG2-8960-R. (e) HepG2 cells without X-rays. (f) At day 5 after exposure to 10 Gy of X-rays, HepG2 cells were filled with autophagosomes (arrow head). (g) HepG2-8960-R cell 2 days after the last maintenance irradiation (2 Gy per day). (h) HepG2-8960-R cell filled with autophagosomes at day 5 after exposure to 10 Gy of X-rays