ERINA is an estrogen-responsive lncRNA that drives breast cancer through the E2F1/RB1 pathway

Resistance to therapeutic drugs is a major challenge in the treatment of cancers including breast cancer. Long noncoding RNAs (lncRNA) are known to have diverse physiological and pathophysiological functions, including in cancer. In searching for lncRNA responsible for cancer drug resistance, we identified an intergenic lncRNA ERINA (estrogen inducible lncRNA) as a novel lncRNA highly expressed in multiple cancer types, especially in estrogen receptor (ER)-positive breast cancers. Expression of ERINA was inversely correlated with survival of ER-positive breast cancer patients and sensitivity to CDK inhibitor in breast cancer cell lines. Functional characterization established ERINA as an oncogenic lncRNA, as knockdown of ERINA in breast cancer cells inhibited cell cycle progression and tumor cell proliferation in vitro and xenograft tumor growth in vivo. In contrast, overexpression of ERINA promoted cell growth and cell cycle progression. ERINA promoted cell cycle progression by interacting with the E2F transcription factor 1 (E2F1), which prevents the binding of E2F1 to the tumor suppressor retinoblastoma protein 1 (RB1). ERINA also functioned as an estrogen and ER-responsive gene, and an intronic ER binding site was identified as an enhancer that mediates the transactivation of ERINA. In summary, ERINA is an estrogen-responsive oncogenic lncRNA that may serve as a novel biomarker and potential therapeutic target in breast cancer.