UCHL1 and breast cancer: Furthermore, using catalytic mutant UCHL1 C90S as a control, the accumulation of p53 mediated by UCHL1 was observed, subsequently, p21, as key p53 downstream target genes and regulators of cell cycle G1/S checkpoint, as well as cleaved-caspase 3 and PARP, were obviously upregulated, accompanied by UCHL1-mediated p53 activation, but not in UCHL1 C90S-expressing breast cancer cells.