Fig. 1

Combination treatment with H89 and tetrandrine yields a synergistic antitumor effect across different types of cancer cells. a Cell viabilities were determined by a trypan blue dye exclusion assay in cancer cells treated with increasing doses of tetrandrine (0–5 μM) or (b) H89 (0–20 μM) alone for 72 h. c Cancer cells were exposed to the designated concentrations of H89 in combination with tetrandrine (4 μM) for 72 h. Cell viabilities were determined as previously described. d Cells were exposed to the designated concentrations of tetrandrine in combination with H89 (6 μM) for 72 h, following which the cell viabilities were determined. e Cell viabilities were determined in cells incubated with H89 (6 μM) and tetrandrine (4 μM) alone or in combination for 72 h. f HBL-100, L02 and HEK293T cells were treated with H89 (6 μM) and tetrandrine (4 μM) alone or in combination for 72 h. Cells viabilities were determined. g The combination index (CI) values for LOVO, MDA-MB-231, AGS, and Hep3B cells were constructed by CalcuSyn 2.1 software. h Cells were treated with H89 and tetrandrine alone or in combination for 24 h. The attached cells were stained with crystal violet after 8 days. The number of colonies was quantified. All representative images are from three independent experiments. Data are reported as the mean ± SD and were analyzed by Student’s t-test; all data represent at least n = 3 independent experiments, *P < 0.05 compared with DMSO control