ER upregulates the expression of long non-coding RNA LINC00472 which suppresses the phosphorylation of NF-B in breast cancer

PurposeLow expression of long intergenic non-coding RNA LINC00472 in breast cancer is associated with aggressive tumors and unfavorable disease outcomes in multiple clinical datasets, but the reasons for these associations were unknown.MethodsTo study the mechanisms underlying the lncRNA's connection to breast cancer, we investigated the molecular targets and regulation of LINC00472 in breast cancer cells, and analyzed relevant molecular features in relation to patient survival. Gene expression profiles of breast cancer cells overexpressing LINC00472 were analyzed for its regulatory pathways and downstream targets. Effects of LINC00472 overexpression on cell behaviors were evaluated in vitro and in vivo. Meta-analysis was performed using online datasets and our own study.ResultsAnalysis of LINC00472 transcriptome revealed ER upregulation of LINC00472 expression, and an ER-binding site in the LINC00472 promoter was identified. Evaluation of LINC00472 overexpression also indicated a possible link between LINC00472 and NF-B. Cell experiments confirmed that LINC00472 suppressed the phosphorylation of p65 and IB through binding to IKK, inhibiting its phosphorylation. High LINC00472 expression inhibited tumor growth both in vitro and in vivo and suppressed aggressive tumor cell behaviors in vitro. Suppressing LINC00472 expression in ER-positive tumor cells increased cell aggressive behaviors. Tamoxifen treatment of ER-positive cells inhibited ER and LINC00472 expression and increased p65 and IB phosphorylation. Meta-analysis showed that LINC00472 expression were higher in ER-positive than ER-negative tumors and that high expression was associated with better disease outcomes in ER-positive patients.ConclusionsThe study demonstrates that ER upregulates LINC00472 which suppresses the phosphorylation of NF-B, and suggests that endocrine treatment may lower LINC00472 and increase NF-B activities, leading to tumor progression and disease recurrence.