Ks. Kim et al., Tissue-specific expression of beta-catenin in normal mesenchyme and uveal melanomas and its effect on invasiveness, EXP CELL RE, 245(1), 1998, pp. 79-90
This paper is the first in a series aimed at understanding the role of beta
-catenin in epithelial-mesenchymal transformation (EMT) and acquisition of
mesenchymal invasive motility. Here, we compare the expression of this and
related molecules in the two major tissue phenotypes, epithelial and mesenc
hymal, the latter including normal avian and mammalian fibroblasts and mali
gnant human uveal melanoma cells. Previously, it was proposed that src init
iates EMT by tyrosine phosphorylation of the cadherin/catenin complex resul
ting in a negative effect on epithelial gene expression. On the contrary, w
e found that although beta-catenin becomes diffuse in the cytoplasm during
embryonic EMT, the cytoplasmic beta-catenin of the embryonic and adult mese
nchymal cells we examined is not tyrosine phosphorylated. Pervanadate exper
iments indicate that cytoplasmic PTPases maintain this dephosphorylation. G
SK-3 beta is present, but little or no APC occurs in normal and neoplastic
mesenchymal cells. The function of the nonphosphorylated cytoplasmic beta-c
atenin in mesenchyme may be related to invasive motility. Indeed, in order
to invade extracellular matrix, transitional (Mel 252) melanoma cells trans
form from an epithelial to a mesenchymal phenotype with increased cytoplasm
ic beta-catenin. Moreover, antisense beta-catenin and plakoglobin ODNs inhi
bit Mel 252 and corneal fibroblast invasion of collagen. All fibroblastic,
transitional, and spindle melanoma cells contain nuclear as well as cytopla
smic beta-catenin, but they are not significantly more invasive than normal
fibroblasts that contain only cytoplasmic beta-catenin. (C) 1998 Academic
Press.