CTCF May Not Directly Regulate ERα mRNA Expression in the ER+ MCF7 Breast Cancer Cell Line

Abstract

Introduction: CTCF is an evolutionally conserved 11-zinc finger protein factor involved in an array of processes whose deregulation could lead to cellular transformation. Through interactions with ERα binding regions and ERregulated genes, CTCF was shown to compartmentalize the cellular genome into domains. It also colocalized with ERα in MCF7 cells and had interactions with ERα during histone deacetylase recruitment and fork-head activity. A fast-running isoform was previously shown to be expressed in breast cancer tissue but not in normal breast tissue. It is not clear whether there is a regulatory relationship between CTCF and ERα in breast cancer. Aim: To determine whether CTCF expression regulated ERα expression in the ER+ MCF7 breast cancer cell line. Methods: MCF7 breast cancer cells were transfected with either CTCF expression vectors or siRNA against CTCF. Following CTCF over-expression and knock-down, changes in endogenous expression of ERα gene and protein expression were monitored by quantitative polymerase chain reaction (using MIQE guidelines) and western blot analysis respectively. Results: CTCF plasmid overexpression and siRNA knockdown was associated with cell rounding but with 96.4% and 95.7% cell viability respectively. Increase in CTCF mRNA on over-expression was associated with a rise in CTCF protein expression. siRNA knockdown of CTCF mRNA was accompanied by a corresponding decrease in CTCF protein expression. CTCF over-expression and knockdown appeared to inhibit the ability to detect ERα protein expression by western blotting. Neither the over-expression nor knockdown of CTCF altered ERα mRNA expression as detected by QPCR. Conclusion: Alterations in CTCF mRNA expression did not affect ERα gene expression in MCF7 cells suggesting that CTCF interactions with the estrogen receptor in breast cancer may not be mediated via direct regulation of ERα mRNA expression.