Fig. 1: Induction of micronuclei by CPT and LMP776 is similar in human HeLa and SCLC H209, H889 and DMS114 cell lines, and is reduced by RNaseH1 overexpression.

a Schematic representation of experimental conditions. One day after seeding, cells were treated for 24 h with TOP1 poisons and, after drug removal, let to recover for 48 h. b Cancer cells were treated for 24 h with 100 nM CPT or 200 nM LMP776 and then recovered for 48 h in a drug-free medium. Micronuclei were then stained with DAPI and counted with fluorescence imaging. Bars represent treated/control ratios and show mean values ± SEM (biological replicates for each cell line are: five for HeLa, two for H209, three for H889, and three for DMS114). Numbers of analysed cells are reported above the bar for each sample. Representative IF images are reported on the right. Asterisks indicate statistical significance in comparison with untreated cells by t test. *P < 0.05, **P < 0.01, ***P < 0.001. c Micronuclei were counted 48 h after release from drug treatment (100 nM CPT or 200 nM LMP776 for 24 h) in U2OS_RH cells, which are stably transfected with doxycycline-dependent RNaseH1-expressing vector. U2OS_RH cells were then exposed to doxycycline (+doxy) or not (−doxy) for 48 h before treatment with TOP1 poisons. RNaseH1 expression was detected with an antibody against a FLAG tag fused to the enzyme. RNaseH1-expressing cells were split into two categories (low and high) depending on the level of RNaseH1 expression. Representative IF images are reported on the right. Statistical significance of three biological replicates calculated with t test with respect to no Doxy are: CPT low P = 0.054, CPT high P = 0.068, LMP776 low P = 0.191, LMP776 high P = 0.058.