PARP3 and in situ carcinoma: Compared with scrambled siRNA-transfected A549, where CIS exposure induced ~25.2% early apoptosis, silencing DDIT4, PARP3 or EP300 reduced 4.1% (P=0.0435), 2.9% (P=0.0476) and 6.8% (P=0.0363) apoptosis, respectively; in particular, combined silencing of them reduced 10.7% apoptosis (P=0.0085) (Figures 5f and g and Supplementary Figure S8).