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Fig. 8 Top2b (topoisomerase 2b) is required for atg7-mediated autophagy in the early but not the late phase of anthracycline-induced cardiotoxicity (AIC). A, Temporal changes of Atg7 protein level post the first dose of doxorubicin (DOX) in the mouse AIC model. n=5 mice per group. Four weeks postinjection (wpi) would be considered as the early phase because it is equal to 1 wk post the last dose of DOX. B, H9C2 cells were transfected with the indicated siRNA. Cell lysates were analyzed by Western blots to check the knockdown effects. H9C2 cells transfected with NC RNAi or Top2b RNAi were treated by DOX for 3 h (C) or 18 h (D), then levels of Atg7 and LC3II (microtubule-associated protein light chain 3II) were examined by Western blots. Kruskal-Wallis test was used followed by post hoc Tukey test. Con indicates control; H9C2,rat cardiomyocytes; LC3,light chain 3; NC, negative control; RNAi, RNA interference; and SiRNA, small interfering RNA.