ERBB2 and breast cancer: Accordingly, our observations that PAQR8 CN gain occurs in > 50% of patients treated with anti-estrogen therapies, as well as in > 50% of patients treated with chemotherapy or Her2-targeted therapies [3], suggest the important possibility that PAQR8 upregulation may account for a substantial fraction of therapy resistance, including endocrine therapy resistance, and in doing so may facilitate tumor recurrence across multiple subtypes of breast cancer.