As shown in Kaplan–Meier survival curves (Figure 1B,C), BC Patients with a high expression of the HDAC2 gene [hazard ratio (HR), 1.65; p < 1 × 10−16; Figure 1B] or high expression level of the HDAC2 protein (HR, 2; p = 0.059; Figure 1C) exhibited a less favorable prognosis compared with patients with low expression levels. The gene discussed is HDAC2; the disease is breast cancer.