Background: In patients with Osteosarcoma (OS), larger primary tumor size correlates with higher metastasis
incidence and lower overall survival. Identifying the mechanisms that control primary tumor growth can lead to the new
therapeutic approaches and improve prognosis. Cytoskeleton regulatory molecules play an important role in tumor cells
proliferation and motility. In the current study, we investigated the role of scaffolding protein Cdc42-interacting protein 4
(CIP4) in OS.
Methods: Murine OS cells, DLM8 were stably transfected with shCIP4 plasmid and their tumorigenic activity was studied
in vitro and in vivo. The effect of CIP4 downregulation on cytoskeleton was studied by immunohistochemical analysis.
Results: In vivo studies revealed that downregulation of CIP4 in OS tumor cells can inhibit primary subcutaneous tumor
growth and delay spontaneous metastases growth in the animal lungs. In vitro studies confirmed that inhibiting CIP4
expression significantly reduced tumor cells invasiveness and migration. Changes in CIP4 expression altered its cellular
localization pattern and tumor cell morphology, which could explain changes in OS cell behavior in vivo and in vitro.
Cells with downregulated CIP4 showed lower levels of actin in cells along with fewer perinuclear actin stress filaments
and actin bridges to the lipid bilayer of the cell membrane than control cells.
Conclusions: This study presents compelling evidence that inhibition of CIP4 expression in OS cells impairs
metastatic behavior of cells in vitro and prolongs survival of animals by inhibiting primary tumor growth. Although the
lack of CIP4 in tumor cells did not prevent formation of metastasis, it did substantially delay their formation in the