ERBB2 and breast cancer: SAHA was also effective in targeting SK- BR-3 (ER−/HER2+, caspase-3, and p53 mutant-expressing) and the triple-negative MDA-MB-231 (ER−/HER2−/PR−, caspase-3, and p53 mutant-expressing) breast cancer cells at low micromolar concentrations (Table 1).