ESR1 and breast cancer: In a breast invasive carcinoma study (Cell 2015, 816 tumors), amplification of the StAR gene (~14%), associated with 74% ER+, 64% PR+, and 51% HER2− (15% HER2+), was found to correlate (p-value = 0.008) with poor breast cancer survival (Figure 3C,C’).