PSPC1 is a potential prognostic marker for hormone-dependent breast cancer patients and modulates RNA processing of ESR1 and SCFD2.

Breast cancer is the most common cancer type among women worldwide. The majority of breast cancer expresses estrogen receptor (ER) and endocrine therapy is a standard treatment of ER-positive breast cancer. However, development of the therapy resistance is still a major challenge and thus new therapeutic approaches are needed. Here we show that an RNA-binding protein, PSPC1, play a crucial role in ER-positive breast cancer growth through post-transcriptional gene regulation. We showed that siRNA-mediated PSPC1 silencing suppressed the proliferation of ER-positive breast cancer cells. Strong immunoreactivity (IR) of PSPC1 was correlated with poor prognosis for ER-positive breast cancer patients. Using immunoprecipitation, RNA-immunoprecipitation (RIP) and quantitative PCR (qPCR) experiments, we showed that PSPC1 interacted with PSF and was involved in post-transcriptional regulation of PSF target genes, ESR1 and SCFD2. Strong SCFD2 IR was correlated with poor prognosis for ER-positive breast cancer patients and combinations of PSPC1, PSF, and SCFD2 IRs were potent prognostic factors. Moreover, we identified DDIAS and MYBL1 as SCFD2 downstream target genes using microarray analysis, and finally showed that SCFD2 silencing suppressed tamoxifen-resistant breast tumor growth in vivo. These results indicated that PSPC1 and SCFD2 axis could be a promising target in the clinical management of the disease.