PPP3CB inhibits pancreatic cancer progression by promoting ATOH8 translocation and transcriptionally regulating Sp1.

[AIMS] Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy which lacks effective therapeutic targets. We previously demonstrated that low PPP3CB expression correlates with poor prognosis in PDAC. This study aims to investigate the function and underlying mechanism of PPP3CB in pancreatic cancer progression.

[MATERIALS AND METHODS] We analyzed PPP3CB expression via immunohistochemistry in PDAC specimens and investigated its prognostic value by statistical method. Differentially expressed genes were analyzed by qRT-PCR and Western blot. Mass spectrometry, Co-IP, ChIP-seq, luciferase analysis, flow cytometry, immunofluorescence and confocal microscopy were performed to investigate the underlying mechanisms of PPP3CB and regulation of ATOH8/Sp1 axis. Mice xenograft models were employed to assess the malignant behaviors in vivo.

[KEY FINDINGS] We found that PPP3CB expression was higher in patients with early-stage PDAC than in those with late-stage PDAC. PPP3CB overexpression impaired PDAC proliferation and metastasis in vitro and in vivo, whereas its depletion or treatment with CsA-a PPP3CB inhibitor, had the opposite effect. Liquid chromatography-tandem mass spectrometry predicted an interaction between PPP3CB and ATOH8. Further investigation confirmed that PPP3CB interacts with ATOH8 and enhances its nuclear translocation in PDAC cells. ChIP-seq and luciferase analyses showed that ATOH8 binds to the promoter of Sp1, a well-known oncogenic transcription factor in PDAC. Furthermore, PPP3CB transcriptionally inhibits Sp1 expression and suppresses pancreatic cancer metastases by increasing ATOH8 nuclear content.

[SIGNIFICANCE] These findings suggest a novel role for PPP3CB in preventing PDAC progression by promoting ATOH8 nuclear translocation and transcriptionally inhibiting Sp1. Consequently, PPP3CB emerges as a potential therapeutic target for PDAC.