PHC3 and neoplasm: Immunofluorescence microscopy analysis of tumor sections for pH3 as a marker for tumor cell mitosis and for clCasp3 as a marker of tumor cell apoptosis revealed that the reduced tumor growth in β-catenin mutant-expressing mice is due to diminished tumor cell proliferation (Fig. 6F and Supplementary Fig. 5B), and not to an increase in tumor cell apoptosis (Fig. 6G and Supplementary Fig. 5C).