PRRX1 isoforms cooperate with FOXM1 to regulate the DNA damage response in pancreatic cancer cells

Oncogene. 2019 May;38(22):4325-4339. doi: 10.1038/s41388-019-0725-6. Epub 2019 Jan 31.

Abstract

PRRX1 is a homeodomain transcriptional factor, which has two isoforms, PRXX1A and PRRX1B. The PRRX1 isoforms have been demonstrated to be important in pancreatic cancer, especially in the regulation of epithelial-to-mesenchymal transition (EMT) in Pancreatic Ductal Adenocarcinoma (PDAC) and of mesenchymal-to-epithelial transition (MET) in liver metastasis. In order to determine the functional underpinnings of PRRX1 and its isoforms, we have unraveled a new interplay between PRRX1 and the FOXM1 transcriptional factors. Our detailed biochemical analysis reveals the direct physical interaction between PRRX1 and FOXM1 proteins that requires the PRRX1A/B 200-222/217 amino acid (aa) region and the FOXM1 Forkhead domain. Additionally, we demonstrate the cooperation between PRRX1 and FOXM1 in the regulation of FOXM1-dependent transcriptional activity. Moreover, we establish FOXM1 as a critical downstream target of PRRX1 in pancreatic cancer cells. We demonstrate a novel role for PRRX1 in the regulation of genes involved in DNA repair pathways. Indeed, we show that expression of PRRX1 isoforms may limit the induction of DNA damage in pancreatic cancer cells. Finally, we demonstrate that targeting FOXM1 with the small molecule inhibitor FDI6 suppress pancreatic cancer cell proliferation and induces their apoptotic cell death. FDI6 sensitizes pancreatic cancer cells to Etoposide and Gemcitabine induced apoptosis. Our data provide new insights into PRRX1's involvement in regulating DNA damage and provide evidence of a possible PRRX1-FOXM1 axis that is critical for PDAC cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Carcinoma, Pancreatic Ductal / drug therapy
  • Carcinoma, Pancreatic Ductal / genetics
  • Cell Line
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cell Proliferation / genetics
  • DNA Damage / genetics*
  • DNA Repair / drug effects
  • DNA Repair / genetics
  • Deoxycytidine / analogs & derivatives
  • Deoxycytidine / pharmacology
  • Epithelial-Mesenchymal Transition
  • Etoposide / pharmacology
  • Forkhead Box Protein M1 / genetics*
  • Gemcitabine
  • HEK293 Cells
  • Homeodomain Proteins / genetics*
  • Humans
  • Liver Neoplasms / drug therapy
  • Liver Neoplasms / genetics
  • Mice
  • Mice, Knockout
  • Pancreas / drug effects
  • Pancreatic Neoplasms / drug therapy
  • Pancreatic Neoplasms / genetics*
  • Pancreatic Neoplasms / pathology
  • Protein Isoforms / genetics*
  • Transcription, Genetic / drug effects
  • Transcription, Genetic / genetics

Substances

  • FOXM1 protein, human
  • Forkhead Box Protein M1
  • Homeodomain Proteins
  • PRRX1 protein, human
  • Protein Isoforms
  • Deoxycytidine
  • Etoposide
  • Gemcitabine