Oestrogen drives breast cancer, and hormone directed therapy is the mainstay of treatment. However, a third of patients do not respond or develop therapeutic resistance. Apart from ERα, PR and AR, the role of other nuclear receptors (NR) in breast cancer have been little explored. A previous study(1) on NR in breast cancer found that NR2F6 or EAR2 (V-Erb-A related protein 2) was uniquely upregulated in both ERα-positive and ERα-negative breast cancers, while all other NRs were universally downregulated. This suggests that EAR2 may be a driver of breast cancer proliferation.
Here, we have examined the role of EAR2 in breast cancer cell proliferation, invasion and migration after modulating EAR2 expression in two breast cancer cell lines.
The Tet-On gene expression system was used to overexpress EAR2 in MCF7 cells and Crispr/Cas9 gene editing to knockdown EAR2 expression in T47D cells. Proliferation was assessed using the xCELLigence Real Time Cell Analyser SP system as well as MTS assays. Cell migration was studied using the Incucyte Live Cell Imaging and Analysis System. RNA-seq analysis was performed and analysed using the Beijing Genomic Institute's Dr.Tom platform.
EAR2 overexpression increased proliferation while knockdown of EAR2 decreased proliferation and increased cell size. Cell migration was increased by EAR2 overexpression. In MCF7 cells overexpressing EAR2, 219 differentially expressed genes were identified, including 47 upregulated and 172 downregulated genes. The most highly expressed genes included GALNT16, MACROD2, GPD1 and WNT10B, some of which have implicated in therapy-resistant breast cancer.
EAR2 appears to be a novel driver of breast cancer proliferation with a role in cancer progression in both ERα-positive and ERα-negative breast cancers. The finding that EAR2 upregulated MACROD2 implicates EAR2 in tamoxifen resistance. These findings suggest that EAR2 could be an unexplored and novel target for breast cancer treatment.