Abstract:  Background and purpose: Long non-coding RNA (LncRNA) plays a critical role in the malignant progression of tumors. Former study identified lncRNA stathmin 1 pseudogene 2 (STMN1P2) was aberrantly expressed in breast cancer tissues with microarray. However, the role it executes in breast cancer is still unclear. This study aimed to investigate the expression and function of STMN1P2 in breast cancer cells and its underlying mechanism. Methods: Real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR) was used to verify the expression of STMN1P2 in breast cancer tissues from 27 breast cancer patients who were treated in Fudan University Shanghai Cancer Center and paracancerous tissues, 3 breast cancer cell lines of MDA-MB-231, BT-549, MCF-7 and human mammary epithelial cell line MCF-10A. STMN1P2 levels were downregulated or upregulated, and transwell, cell apoptosis and cell cycle detection assays were performed to study the biological functions of STMN1P2. The binding protein was figured out through RNA pull-down experiment combined with Western blot to discover the underlying mechanism. Results: The expression of STMN1P2 was significantly upregulated in breast cancer tissues and cells (P<0.05). Interference with STMN1P2 decreased the migration of BT-549 cells (P<0.05), and overexpression of STMN1P2 increased the migration of MDA- MB-231 cells (P<0.05). Our results showed that STMN1P2 might not be related to cell apoptosis and cell cycle. RNA pull-down results showed that heterogeneous nuclear ribonucleoprotein U (hnRNPU) might be the binding protein of STMN1P2, and the expression of hnRNPU might be regulated by STMN1P2 (P<0.05). The results of the rescue experiment showed that downregulating hnRNPU expression reversed the effect of STMN1P2 on promoting cell migration (P<0.05). Conclusion: STMN1P2 may promote breast cancer cell migration via binding and interacting with hnRNPU.

Key words: Long non-coding RNA, Breast cancer, Migration, Heterogeneous nuclear ribonucleoprotein U