(d) Parental and regorafenib-resistant HCT116 cells were treated with 40 M regorafenib, 20 M sorafenib, 1 M UCN-01, 1 M YM-155, 10 M roscovitine, 15 M sunitinib, 10 M crizotinib, 10 nM TRAIL, 10 M VX680, 20 M etoposide, 20 M temsirolimus or 120 M sulindac sulfide for 48 h. Apoptosis was analyzed as in b. (e) Western blotting of Mcl-1 in parental and regorafenib-resistant HCT116 cells treated with indicated agents as in d for 24 h. Results in (b-d) represent the means s.d. of three independent experiments. NS, P 0.05; *P 0.05; **P 0.01.