Furthermore, while previous studies have looked at gene expression levels in relation to histone modifications [9, 10], we assessed this relationship in our four HER2+ breast cancer cell lines; two HER2+/ER+ cell lines (MB361 and UACC815) and two HER2+/ER- cell lines (AU565 and SKBR3). The gene discussed is ERBB2; the disease is breast cancer.