An RNA-binding protein, Hu-antigen R, in pancreatic cancer epithelial to mesenchymal transition, metastasis, and cancer stem cells.

Pancreatic cancer has poor prognosis and treatment outcomes due to its highly metastatic nature and resistance to current treatments. The RNA binding protein (RBP) Hu-antigen R (HuR) is a central player in posttranscriptional regulation of cancer related gene expression, and contributes to tumorigenesis, tumor growth, metastasis and drug resistance. HuR has been suggested to regulate pancreatic cancer epithelial to mesenchymal transition (EMT) but the mechanism was not well understood. Here we further elucidated the role HuR plays in pancreatic cancer cell EMT, and developed a novel inhibitor specifically interrupting HuR-RNA binding. The data showed that HuR binds to the 39-UTR of the mRNA of the transcription factor Snail, resulting in stabilization of Snail mRNA and enhanced Snail protein expression, thus promoted EMT, metastasis and formation of stem-like cancer cells (CSCs) in pancreatic cancer cells. siRNA silencing or CRISPR/Cas9 gene deletion of HuR inhibited pancreatic cancer cell EMT, migration, invasion, and inhibited CSCs. HuR knockout cells had dampened tumorigenicity in immunocompromised mice. A novel compound KH-3 interrupted HuR-RNA binding, and KH-3 inhibited pancreatic cancer cell viability, EMT, migration/invasion in vitro. KH-3 showed HuR-dependent activity and inhibited HuR-positive tumor growth and metastasis in vivo.