PSF promotes ER-positive breast cancer progression via posttranscriptional regulation of ESR1 and SCFD2.

Endocrine therapy is standard treatment for estrogen receptor (ER)-positive breast cancer, yet long-term treatment often causes acquired resistance, which results in recurrence and metastasis. Recent studies have revealed that RNA-binding proteins (RBP) are involved in tumorigenesis. Here we demonstrate that PSF/SFPQ is an RBP that potentially predicts poor prognosis of ER-positive breast cancer patients by posttranscriptionally regulating ERα (ESR1) mRNA expression. Strong PSF immunoreactivity correlated with shorter overall survival in ER-positive breast cancer patients. PSF was predominantly expressed in a model of tamoxifen-resistant breast cancer cells, and depletion of PSF attenuated proliferation of cultured cells and xenografted tumors. PSF expression was significantly associated with estrogen signaling. PSF siRNA downregulated ESR1 mRNA by inhibiting nuclear export of the RNA. Integrative analyses of microarray and RNA-immunoprecipitation sequencing also identified SCFD2, TRA2B, and ASPM as targets of PSF. Among the PSF targets, SCFD2 was a poor prognostic indicator of breast cancer and SCFD2 knockdown significantly suppressed breast cancer cell proliferation. Collectively, this study shows that PSF plays a pathophysiological role in ER-positive breast cancer by posttranscriptionaly regulating expression of its target genes such as ESR1 and SCFD2. Overall, PSF and SCFD2 could be potential diagnostic and therapeutic targets for primary and hormone-refractory breast cancers.