Overexpression of poly(rC) binding protein 2 by alternative cleavage and polyadenylation promotes breast cancer progression via regulating UFD1 and NT5E

Alternative cleavage and polyadenylation (APA) is an important post-transcriptional regulatory mechanism, which could lead many diseases. PCBP2 plays critical roles in mRNA stabilization, translational enhancement and contributes to human cancer development and progression even though the molecular mechanism is not completely understood. Herein, we report that increased expression of PCBP2 is observed in human breast cancer tissues compared to benign or normal breast tissues, and high expression of PCBP2 is significantly associated with disease progression and poor outcome in patients with breast cancer. Knockdown of PCBP2 expression significantly decreased breast cancer cell proliferation, migration and invasion in vitro and in vivo. Molecularly, UFD1 and NT5E were identified as the downstream genes of PCBP2, which were scanned and verified based on RNA sequencing. Moreover, PCBP2 promotes oncogenic behaviors of breast cancer cells via upregulating the expression of UFD1 and NT5E by directly binding to their 3' untranslated regions (UTRs). Furthermore, we determine that the APA process is involved in regulating the overexpression PCBP2 in breast cancer cells. Therefore, our findings reveal that APA of PCBP2 3' UTR contributes to its overexpression and then promotes breast cancer progression by regulating the expression of UFD1 and NT5E. The expression of PCBP2 in human benign breast disease tissues and breast cancer tissues was evaluated by immunohistochemistry and western blot. Second, the association of PCBP2 expression with clinicopathological parameters and survival of breast cancer patients were analyzed. Third, the role of PCBP2 in breast cancer cell proliferation, migration and invasion was determined in vitro and in vivo. In the following stage, the downstream genes of PCBP2 was scanned by RNA sequencing and verified by western blotting, immunohistochemistry as well as qRT-PCR. Meanwhile, Biotin pull-down assay was carried out to examine the binding site of PCBP2 protein in UFD1 or NT5E mRNA. Finally, 3'RACE was performed to detect the APA status of PCBP2 mRNA.