Fig. 2
A-B Effects of OTS964 on the cytotoxicity of chemotherapeutic drugs in ABCB1-overexpressing cells. The effect of OTS964 on the cytotoxicity of PTX, DOX, VCR, and CDDP in A) KB-C2 and KB-3-1 cells and B) HEK293/ABCB1 and HEK293/pcDNA3.1 cells. The GraphPad software [log (inhibitor) vs. response] was used to fit nonlinear regression and to calculate IC50 values. In the concentration-response curve, each dot is expressed as mean ± SD from a representative of three independent experiments. C-D Effects of OTS964 on expression levels of ABCB1 protein and mRNA. The effect of OTS964 on ABCB1 protein and mRNA expression in C) KB-C2 and KB-3-1 cells and D) HEK293/ABCB1 and HEK293/pcDNA3.1 cells. In the Western blot analysis, the relative density of each protein band was analyzed by Fiji software, and ABCB1 protein expression levels were normalized to GAPDH before comparison. In the qRT-PCR analysis, data were calculated based on the comparative ΔΔCT method and expressed as the relative fold changes. Data are expressed as mean ± SD from a representative of three independent experiments. *p < 0.05 versus the respective control group. E Effects of OTS964 on the intracellular and extracellular amount of [3H]-PTX in ABCB1-overexpressing cells after 72 h of treatment. The relative ratio of [3H]-PTX of KB-C2 and KB-3-1 cells, as well as HEK293/ABCB1 and HEK293/pcDNA3.1 cells in cell pellets or remaining medium after 72 h of treatment. The relative ratio was calculated as the treatment group divided by the parental control group. Data are expressed as mean ± SD from a representative of three independent experiments. *p < 0.05 versus the respective control group. F-J Antitumor activity of OTS964 in SW620 and SW620/Ad300 tumor xenograft models. F) From left to right: Images of excised SW620 tumor tissues from nude athymic mice at the end of treatment period. The changes of tumor volume in SW620 tumor xenograft model over time following the implantation. The weight of excised SW620 tumor tissues from nude athymic mice at the end of treatment period. G) From left to right: Images of excised SW620/Ad300 tumor tissues from nude athymic mice at the end of treatment period. The changes of tumor volume in SW620/Ad300 tumor xenograft model over time following the implantation. The weight of excised SW620/Ad300 tumor tissues from nude athymic mice at the end of treatment period. H) The changes of body weight during the treatment period. The I) WBC and J) platelet counts of nude athymic mice at the end of treatment period. Data are expressed as mean ± SD. *p < 0.05 versus the respective control group