Characterization of CPSF1-mediated alternative polyadenylation in cancer

Metastasis, the leading cause of cancer-related death, remains a major challenge in cancer treatment. Epithelial-to-mesenchymal transition (EMT) is a well-known driver in metastasis, endowing cancer cells with enhanced migration and invasion properties. While EMT is often triggered by transcriptional reprogramming of gene expression, the contribution of post-transcriptional regulations, such as alternative polyadenylation (APA), remains largely uncharted. APA has gained attention due to its unique role in regulating 3’-untranslated regions (3’UTRs). Cleavage and polyadenylation specific factor 1 (CPSF1) is a core APA component, which facilitates recognition of the canonical poly(A) signals. However, its involvement in metastasis has yet to be thoroughly investigated. Through unbiased bioinformatics interrogation, we identified elevated CPSF1 expression across multiple distinct cancer types, which correlated with metastasis and unfavorable clinical outcomes. Functionally, CPSF1 gain-of-function studies revealed enhanced cancer cell proliferation and motility, while genetic abrogation of CPSF1 impaired cancer cell migration, invasion and EMT. CPSF1-knockout cancer cells exhibited a biased shift towards lengthened 3’UTRs in many gene transcripts through Quantitative APA (QAPA) analysis, including the key EMT regulators such as TGFBR1 and SOX9. Using ultrasound-guided sub-renal capsule xenograft models and orthotopic bladder xenograft models, we demonstrated that CPSF1-deficiency impaired tumor growth, invasion, and metastasis. Additionally, we found that CPSF1 was required to maintain CPSF complex stability by preventing ubiquitin-mediated degradation of the complex components. Collectively, our research uncovers dual function of CPSF1 in maintaining the mesenchymal features and CPSF complex stability in cancer cells. These insights position CPSF1 as a potential therapeutic target in cancer treatment.