Localization and in vitro activity of β-catenin in MCL cell lines. (A) Subcellular fractionation using the cell lysates of 3 MCL cell lines revealed that β-catenin was localized to the nucleus (N). The expression of α-tubulin in the cytoplasm (C) served as a control for the efficiency of subcellular fractionation. (B) Confocal microscopy revealed the nuclear accentuation of the β-catenin staining in MCL cells (bottom panel). The use of secondary antibody served only as negative controls (top panel). (C) The use of the TOP/FOP system confirmed that β-catenin is transcriptionally active in SP53 and Mino cells. Luciferase activity is expressed as arbitrary units (AU). Error bars indicate SD. Experiments were performed in triplicates and the differences are statistically significant (P < .05, Student t test).