Figure 8.

p120-catenin/β-catenin interactions in human cancer cells and PhIP-induced skin tumors. (A) Target-specific shRNA was used to knockdown p120-catenin, and was compared with vector and non-target shRNA controls. Immunoblotting in A431NS and SW480 cells confirmed the reduced expression of p120-catenin protein, as well as β-catenin and Cyclin D1 (hatched boxes); (B) shRNA knockdown of p120-catenin lowered Ccnd1 (Cyclin D1) mRNA levels significantly, relative to non-target and mock controls; n=3, p<0.001. No changes were detected in Ctnnb1 (β-catenin) mRNA levels under these conditions, data not shown; (C) Co-immunoprecipitation (co-IP) experiments in SW480 cells transiently transfected with p120-catenin isoforms 1A, 3A, 4A, or the vector control, as in Figure 7; solid arrowheads indicate the positions of the three p120-catenin isoforms transfected. (D) Endogenous interactions of β-catenin with p120-isoforms in A431NS cells; open arrowhead designates a putative p120-catenin isoform (or splice variant) of intermediate size between isoforms 3A and 4A, shown with solid arrowheads; (E) co-IP experiments were performed on whole cell lysates from PhIP-induced skin tumors (T) and adjacent normal-looking tissue (N). Data shown are from a single T/N pair run in duplicate, and are representative of the findings from a least three separate rat tumor samples.