title: Smurf2 E3 ubiquitin ligase modulates proliferation and invasiveness of breast cancer cells in a CNKSR2 dependent manner.
abstract: BACKGROUND
  Smurf2 is a member of the HECT family of E3 ubiquitin ligases that play important roles in determining the competence of cells to respond to TGF- β/BMP signaling pathway. However, besides TGF-β/BMP pathway, Smurf2 regulates a repertoire of other signaling pathways ranging from planar cell polarity during embryonic development to cell proliferation, migration, differentiation and senescence. Expression of Smurf2 is found to be dysregulated in many cancers including breast cancer. The purpose of the present study is to examine the effect of Smurf2 knockdown on the tumorigenic potential of human breast cancer cells emphasizing more on proliferative signaling pathway.
  
  
  METHODS
  siRNAs targeting different regions of the Smurf2 mRNA were employed to knockdown the expression of Smurf2. The biological effects of synthetic siRNAs on human breast cancer cells were investigated by examining the cell proliferation, migration, invasion, focus formation, anchorage-independent growth, cell cycle arrest, and cell cycle and cell proliferation related protein expressions upon Smurf2 silencing.
  
  
  RESULTS
  Smurf2 silencing in human breast cancer cells resulted in a decreased focus formation potential and clonogenicity as well as in vitro cell migration/invasion capabilities. Moreover, knockdown of Smurf2 suppressed cell proliferation. Cell cycle analysis showed that the anti-proliferative effect of Smurf2 siRNA was mediated by arresting cells in the G0/G1 phase, which was caused by decreased expression of cyclin D1and cdk4, followed by upregulation p21 and p27. Furthermore, we demonstrated that silencing of Smurf2 downregulated the proliferation of breast cancer cells by modulating the PI3K- PTEN-AKT-FoxO3a pathway via the scaffold protein CNKSR2 which is involved in RAS-dependent signaling pathways. The present study provides the first evidence that silencing Smurf2 using synthetic siRNAs can regulate the tumorigenic properties of human breast cancer cells in a CNKSR2 dependent manner.
  
  
  CONCLUSIONS
  Our results therefore suggest a novel relation between Smurf2 and CNKSR2 thereby regulating AKT-dependent cell proliferation and invasion. Owing to the fact that PI3K-AKT signaling is hyperactivated in various human cancers and that Smurf2 also regulates cellular transformation, our results indicate that Smurf2 may serve as a potential molecule for targeted cancer therapy of certain tumour types including breast cancer.
authors.affiliation: Research Scholar, Cancer Research, Rajiv Gandhi Centre for Biotechnology, Trivandrum 695 014, Kerala, India.
authors.forename: Diana
authors.initials: D
authors.lastname: David
authors.affiliation: Research Scholar, Department of Genetics, Dr.ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai, Taramani 600 113, India.
authors.forename: Sankar
authors.initials: S
authors.lastname: Jagadeeshan
authors.affiliation: Depatment of Pathology, University of Washington, Seattle, WA 98105, USA.
authors.forename: Ramkumar
authors.initials: R
authors.lastname: Hariharan
authors.affiliation: Research Scholar, Cancer Research, Rajiv Gandhi Centre for Biotechnology, Trivandrum 695 014, Kerala, India.
authors.forename: Asha Sivakumari
authors.initials: AS
authors.lastname: Nair
authors.affiliation: Research Scholar, Cancer Research, Rajiv Gandhi Centre for Biotechnology, Trivandrum 695 014, Kerala, India.
authors.forename: Radhakrishna Madhavan
authors.initials: RM
authors.lastname: Pillai
keywords: Breast cancer; CNKSR2; Oncogenic signaling; PI3K-AKT; Proliferation; Smurf2