Fig. 6.

DSB-dependent PD-L1 upregulation is mediated through IRF1 pathway. a, b DSBs activate STAT1/3 and IRF1 signalling. U2OS (a) or H1299 (b) cells were harvested after 10 Gy, 500 nM Etp or 50 nM CPT. c IRF1 is required for PD-L1 upregulation after IR. PD-L1 expression was examined in IRF1-depleted U2OS cells 48 h after 10 Gy. d, e ATM and Chk1 activities promote IRF1 upregulation after IR. IRF1 levels were examined with or without ATM (d) or Chk1 (MK8776) (e) inhibitor after 10 Gy. f, g Depletion of IRF1 significantly reduces the upregulation of cell-surface PD-L1 after IR. Cell-surface PD-L1 expression in IRF1-depleted U2OS (f) or H1299 (g) cells was examined by flow cytometry at 48 h after 10 Gy. A representative histogram is shown in the right panel. Error bars represent the s.d. of three independent experiments (f, g). Statistical significance was determined using Student’s two-tailed t-test. *P < 0.05, **P < 0.01, ***P < 0.001