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. 2019 Mar 5;9:3617. doi: 10.1038/s41598-019-40218-0

Figure 3.

Figure 3

CHK1 siRNA and additional CHK1 inhibitors enhance CPX-351-induced apoptosis. (a) U937 cells were transfected with two different CHK1 siRNAs (siCHK1) or control luciferase siRNA (siLuc), incubated for 24 h, exposed to the indicated concentrations of CPX-351 for 24 h, stained with PI, and subjected to flow microfluorimetry. Left panel, results of one experiment. Middle panel, immunoblot of cell lysates prepared from cells 48 h after transfection with control or CHK1 siRNAs. Right panel, summarized results of 3 independent experiments. *p < 0.01 relative to control siRNA samples treated with CPX-351. (b–g) U937 cells were treated for 24 h with diluent or CPX-351 in the absence of presence of the indicated concentrations of rabusertib (b) or prexasertib (e) or in 300 nM rabusertib (c,d) or 3 nM prexasertib (f,g) in the absence or presence of CPX-351 at 10 µM cytarabine equivalents (b,c,e,f) or 5 µM cytarabine equivalents (d,g) and examined for subdiploid DNA by flow microfluorimetry (b,e), annexin V binding (c,f) or cleavage of procaspase-3 and PARP1 (d,g). In b and e, left hand panels show dose-response curves from individual experiments. Bar graphs show mean ± sd from 6 (b), 4 (c,f), or 3 (e) independent experiments. ** and ***p < 0.02 and p = 0.003 relative to CPX-351 plus diluent.