Effects of minocycline on the cytotoxicity of AC chemotherapy in MDA-MB-231 and MDA-MB-468 TNBC cells. A. Cell viability was assessed by MTT assay after minocycline co-treatment with AC (doxorubicin/cyclophosphamide [μM/mM]: 0/0, 1/2.5, 2.5/5, 5/10, 7.5/15, and 10/20). B. Cell survival was assessed by colony formation assay after minocycline co-treatment with AC (nM/μM: 0/0, 0.5/0.5, 1/1, 2.5/2.5, 5/5, 10/10). C. Evaluation of the effect of minocycline (Mino) on biomarkers in AC-treated TNBC cells by western blot. Cells were treated with AC at 0/0 0.5/1, 1/2.5, 2.5/5, 5/10 μM/mM. For panels A and C, cells were pretreated with minocycline for 24 hours, followed by 48-hour exposure to the AC-minocycline combination. For B, cells were treated with minocycline for 24 hours, and then the AC-minocycline combination for 24 hours, followed by a 12-day growth period.