PCNA and breast cancer: However, intervention by CA or FK866 (visfatin inhibitor) could inhibit (1) visfatin-induced iNAMPT and eNAMPT protein expression, (2) NAMPT enzyme activity, (3) breast cancer cell proliferation, (4) cell proliferative-associated protein expression (PI3K, mTOR, and PCNA), and (5) tumor growth in vivo (Figure 7).