The long noncoding RNA SPRY4-IT1 increases the proliferation of human breast cancer cells by upregulating ZNF703 expression

Background: Long noncoding RNAs (lncRNAs) have emerged recently as a new class of genes regulating cellular processes, such as cell growth and apoptosis. The SPRY4 intronic transcript 1 (SPRY4-IT1) is a 708-bp lncRNA on chromosome 5 with a potential functional role in tumorigenesis. The clinical significance of SPRY4-IT1 and the effect of SPRY4-IT1 on cancer progression are unclear. Methods: Quantitative reverse transcriptase PCR (qRT-PCR) was performed to investigate the expression of SPRY4-IT1 in 48 breast cancer tissues and four breast cancer cell lines. Gain and loss of function approaches were used to investigate the biological role of SPRY4-IT1 in vitro. Microarray bioinformatics analysis was performed to identify the putative targets of SPRY4-IT1, which were further verified by rescue experiments, as well as by western blotting and qRT-PCR. Results: SPRY4-IT1 expression was significantly upregulated in 48 breast cancer tumor tissues compared to normal tissues. Additionally, increased SPRY4-IT1 expression was associated with larger tumor size and an advanced pathological stage in breast cancer patients. Knockdown of SPRY4-IT1 significantly suppressed proliferation and caused apoptosis of breast cancer cells in vitro. Furthermore, we discovered ZNF703 was a direct target of SPRY4-IT1 and was downregulated by SPRY4-IT1 knockdown. Moreover, we demonstrated for the first time that ZNF703 is a genetic driver in ER (-) breast carcinoma cells. Conclusions: SPRY4-IT1 is a novel prognostic biomarker and a potential therapeutic candidate for breast cancer. Five samples are analyzed, including three control groups and two small interfering RNA groups