Figure 3 from ZSTK3744, a Novel Aryl Hydrocarbon Receptor Agonist, Exhibits Efficacy against Chemotherapy-Resistant Triple-Negative Breast Cancer

Evaluation of the cell growth–inhibitory activity of ZSTK3744 on chemotherapy-resistant cells. Parental MM468, MM468/AR (A), and MM468/PR cells (B) were treated with ZSTK3744, ZSTK3341, adriamycin, paclitaxel, or eribulin at the indicated concentrations for 72 hours. Cell viability was assessed using the Cell Counting Kit-8 assay (mean ± SD of quadruplicate experiments). C, AhR and GAPDH protein expression levels were analyzed using Western blotting in parental MM468, MM468/AR, and MM468/PR cells. GAPDH was used as a loading control. D, Parental and ABCB1-overexpressed MM468 cell clone #10 and #12 were treated with ZSTK3744 for 72 hours. Cell viability was assessed using the Cell Counting Kit-8 assay (mean ± SD of quadruplicate experiments). F, ABCB1-overexpressed MM468 cell clone #10 were treated with ZSTK3744, adriamycin, paclitaxel, and eribulin for 72 hours. Cell viability was assessed using the Cell Counting Kit-8 assay (mean ± SD of quadruplicate experiments). E, Evaluation of the antitumor activity of ZSTK3744 and eribulin in a mouse xenograft model. NOD/SCID mice were subcutaneously injected with MM468/AR cells. Administration of these drugs was initiated when the tumor volume reached 100–300 mm3. ZSTK3744 was administered intravenously at doses of 2.5 or 10 mg/kg, whereas eribulin was administered intravenously at a dosage of 1.5 mg/kg on days 0, 7, and 14. G, Tumor volumes and body weight were measured on days 0, 4, 7, 10, 14, 17, 20, 24, 28, and 32 (mean ± SD, n = 5). Body weight data are presented as the change from baseline (day 0). Statistical analysis was performed using the Kruskal–Wallis test, followed by the Steel–Dwass test (*, P < 0.05 vs. vehicle-treated group; #P < 0.05 vs. eribulin-treated group on day 32 of administration). wt, wild type.