PRL-3 promotes epithelial mesenchymal transition by regulating cadherin directly

Abstract

PRL-3 is a key gene associated with progression and metastasis of colorectal cancer.

Recently PRL-3 was suggested to promote epithelial mesenchymal transition（EMT）

by down-regulating E-cadhrin expression. But the mechanisms of EMT induced by

PRL-3 remain largely unknown. Here we found that PRL-3 could also promote EMT

in a colorectal cancer cell model SW480 with deficient E-cadherin expression in vivo

and in vitro. PRL-3 stable overexpression or knockdown SW480 cells were injected

subcutaneously into nude mice. Immunohistochemical analyses of tumor samples from

nude mice showed that PRL-3 promoted up-regulation of mesenchymal marker

vimentin and down-regulation of epithelial markers E-cadherin and cytokeratin.

Glycogen synthase kinase-3β inactivated by PRL-3 as assessed by phosphospecific

antibodies was a key event in EMT induced by PRL-3. Inhibition of glycogen

synthase kinase-3β by lithium chloride, a highly selective inhibitor, leading to

phosphorylation of glycogen synthase kinase-3β increased Snail expression. In order

to identify the direct effects of PRL-3, we isolated CDH22, one member of cadherin

family, as a new candidate of interacting proteins of PRL-3 in yeast two-hybrid

systems, and the interaction was confirmed in vitro by GST pull-down assay or in

exogenous cell systems and endogenous colorectal cancer cells by

co-immunoprecipitation assay and co-localization analysis. We observed that PRL-3

promoted down-regulation of CDH22 expression. Interestingly, expression of

E-cadherin was recovered in SW480 cells after PRL-3 was knocked-down. Our

results first linked PRL-3 to cadherin directly. It provided new insights into the

regulatory mechanisms of EMT induced by PRL-3.