Figure 5: DSCAM-AS1 is implicated in tamoxifen resistance.

(a) qPCR expression of DSCAM-AS1, ESR1, GREB1 and PGR in tamoxifen-resistant MCF7 cells relative to parental MCF7. Error bars represent the s.e.m. for three biological replicates. *P<0.01, ***P<0.0001, comparing to parental MCF7 for each condition via Student’s t-test. (b) Proliferation assay in parental MCF7 cells and in TamR-MCF7 cells following siRNA-mediated knockdown of DSCAM-AS1 via two independent siRNAs. Error bars represent the s.e.m. for three biological replicates. **P<0.001, ***P<0.0001, comparing to parental TamR siNT for each condition via Student’s t-test. (c) WST viability assay following 10 days of culture in varying levels of tamoxifen performed for T47D cells overexpressing LacZ control and DSCAM-AS1. Error bars represent the s.e.m. for three biological replicates. ***P<0.0001, comparing to LacZ overexpression via Student’s t-test. (d) Depiction of oestrogen receptor binding to the DSCAM-AS1 (left) and GREB1 (right) promoters via ChIP-seq performed in primary and metastatic breast cancer tumour tissues. ER status and response to tamoxifen treatment detailed to left. ER binding peaks (determined using MACS software) are depicted in red (for promoter binding) and black (for non-promoter binding). Promoter defined as 5KB upstream of any transcriptional start site. ER promoter binding indicated by red check or ‘x’ to the right. Genomic coordinates in hg19 listed above. siRNA, small interfering RNA.