Mislocalization of the cell polarity protein Scribble (Scrib) induces SPARC secretion in hepatocellular carcinoma

Cell polarity is crucial for the maintenance of epithelial cell function and its loss may have an im-portant role in the development and progression of cancer. We here show that overexpression and cytoplasmic enrichment of the baso-lateral polarity complex protein Scribble (Scrib) correlates with poor prognosis of hepatocellular cancer (HCC) patients. Expression of the cytoplasmic ScribP305L in hepatocellular cells induces epithelial to mesenchymal transition (EMT) and supports HCC cell invasion in comparison to cells expressing membrane-localized ScribWT. ScribP305L induces AKT signalling through destabilization of the phosphatases phosphatase and tensin homolog (PTEN) and PH domain and leucine rich repeat protein phosphatase 1 (PHLPP1). Moreover, cytoplasmic ScribP305L stimulates the expression of secreted protein acidic and cysteine rich (SPARC) de-pending on the AP1 constituents ATF2 and JunB, which drives HCC cell invasiveness. In vivo, combined hydrodynamic delivery of ScribP305L but not ScribWT and c-MYC initiates tumour for-mation in hepatocytes and cytoplasmic Scrib correlates with AKT phosphorylation, and AP1 ex-pression in human HCC tissues. Together, overexpression and mislocalization of Scrib represents an early event involved in the initiation and progression of liver cancer. Triplicates of three cell lines were compared: untrasfected HepG2, HepG2 cell expressing wildtype Scribbel and HepG2 cell expressing mutated Scribble.