E3 ubiquitin ligase Smurf2: a prognostic factor in microsatellite stable colorectal cancer

Fee Klupp,1 Christina Giese,1 Niels Halama,2 Clemens Franz,1 Felix Lasitschka,3,4 Arne Warth,3 Thomas Schmidt,1 Matthias Kloor,5 Alexis Ulrich,1 Martin Schneider1 1Department of General, Visceral and Transplantation Surgery, University of Heidelberg, Heidelberg 69120, Germany; 2National Center for Tumor Diseases, Medical Oncology and Internal Medicine VI, Tissue Imaging and Analysis Center, Bioquant, University of Heidelberg, Heidelberg 69120, Germany; 3Institute of Pathology, University of Heidelberg, Heidelberg 69120, Germany; 4Tissue Bank of the National Center for Tumor Diseases, Heidelberg 69120, Germany; 5Department of Applied Tumor Biology, German Cancer Research Center, Heidelberg 69120, Germany Purpose: Smurf2 is a member of the homologous to E6-AP carboxyl terminus family of E3 ubiquitin ligases. Changes in their expression pattern are known to contribute to tumorigenesis. Smurf2 plays a decisive role in cell differentiation, proliferation, and migration and exhibits a dual role in cancer – functioning as both oncogene and tumor suppressor. Dysregulation of Smurf2 in different cancer types has been described, besides colorectal cancer (CRC). We therefore examined the expression and oncogenic potential of Smurf2 in human CRC patients.Materials and methods: Expression levels of Smurf2 were analyzed via qRT-PCR in CRC specimens and healthy mucosa from 98 patients who had undergone surgery due to CRC. Spatial expression of Smurf2 was additionally studied by immunohistochemistry. siRNA-mediated knockdown of Smurf2 was applied for migration and invasion assays in DLD-1 and SW-480 cells.Results: Smurf2 was significantly overexpressed in CRC tissue compared to corresponding healthy colon mucosa. Smurf2 expression levels differed significantly between microsatellite instable (MSI) and microsatellite stable (MSS) CRC. In patients suffering from MSS CRC, high tumoral expression of Smurf2 was significantly associated with impaired overall survival. Consistently, in vitro analysis revealed that knockdown of Smurf2 reduced the invasive and migratory potential of MSS CRC cells.Conclusion: Smurf2 expression is upregulated in CRC specimens and affects survival dependent on patients’ MSI status. Moreover, Smurf2 supports cancer cell migration and invasion, collectively suggesting an oncogenic function in CRC. Keywords: Smurf2, colorectal cancer, MSS status, prognosis, biomarke