Abstract 1610: Inhibiting HuR, a RNA-binding protein, for inhibition of pancreatic cancer EMT and CSCs

Abstract Purpose Epithelial- mesenchymal transition (EMT) contributes importantly to cancer cell metastasis, and formation of cancer stem cells (CSCs). An RNA-binding protein, HuR, plays an important role in many solid tumors for promoting cell proliferation, metastasis, anti-apoptosis and drug resistance. However, the role of HuR in cancer cell EMT and CSC has not been elucidated. Here we aim to investigate the role of HuR in pancreatic cancer EMT and CSC, and developing a new HuR inhibitor ST-3 as an inhibitor for pancreatic cancer EMT and CSCs. Methods Fluorescence Polarization assay and surface plasmon resonance assay was utilized for St-3, HuR and target mRNA binding. Scratching assay and matrigel invasion assay were used for cell migration and invasion, whereas MTT assay for viability. Tumor spheroid formation assay was used as an indication of CSCs. Western blot and RT-qPCR was used for protein and mRNA expression. Results Knockdown of HuR with siRNA inhibited migration of pancreatic cancer cells MIAPaCa-2, and suppressed the expression of Vimentin, Snail, and increased E-cadherin expression, showing inhibition in EMT. The suppression of Snail is due to accelerated mRNA decay. Overexpression of HuR protected mRNA of Snail from degradation, suggesting that Snail is a direct target of HuR. Knockdown of HuR also decreased pancreatic cancer spheroids formation. St-3 inhibited the proliferation of pancreatic cancer cell lines more potently in HuR-high cells MIAPaCa-2 (IC50 ∼2 μM), than in HuR-low cells BxPc-3 and PANC-1 (IC50 6-20 μM). St-3 directly bound to HuR, and inhibited binding of HuR with its target mRNAs. St-3 treatment mimicked the HuR knockdown effects in inhibiting cell migration, EMT, and spheroids formation. Conclusion HuR is an important regulator in pancreatic cancer EMT and CSCs. ST-3 as a novel HuR inhibitor inhibited pancreatic cancer EMT and CSCs. Further investigation is under way. Citation Format: Ruochen Dong, Kishore Polireddy, Ying Zhang, Qi Chen. Inhibiting HuR, a RNA-binding protein, for inhibition of pancreatic cancer EMT and CSCs. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1610.