Downregulation of PLK4 Expression Induces Cellular Dormancy in Colorectal Cancer via Mesenchymal-to-epithelial Transition

Abstract

Background: Reactivation of dormant tumor cells is a critical step in the recurrence of many cancers, including colorectal cancer (CRC). Polo-like kinases 4 (PLK4), a central regulator of the cell cycle and proliferation, is a validated oncogene in tumorigenesis. However, the roles of PLK4 in tumor cell dormancy and reactivation still need to be further explored.Methods: The expression level of PLK4 was determined by immunohistochemical staining, Western blotting (WB) and quantitative real-time PCR (qRT-PCR). PLK4-dependent clinicopathological risk factors and the prognosis of CRC were characterized with 122 clinical samples. The roles of PLK4 in tumor cell dormancy, cell cycle progression, proliferation and invasion were determined by molecular and cell biology methods in vitro and in vivo.Results: The expression of PLK4 was dramatically increased in CRCs and positively correlated with aggressive tumor behavior and clinicopathological risk factors. Downregulation of PLK4 expression contributed to restoring phenotypically aggressive tumor cells to a quiescent state, and this transformation was likely regulated by mesenchymal-to-epithelial transformation (MET) progression in vitro and in vivo.Conclusions: This study elucidates the mechanisms involving PLK4 depletion in the induction and maintenance of CRC dormancy, which are very important in terms of both clinical significance and application value.