Ki67

The Ki-67 antigen is a nuclear protein, which is preferentially expressed during all active phases of the cell cycle (G1, S, G2, and M-phases), but it is absent in resting cells (G0-phase). The antigen is rapidly degraded as the cell enters the non-proliferative state. Comparisons between pre- and post-treatment levels of Ki-67 may be used to evaluate the effectiveness of mitotic inhibitors, drugs that induce senescence, and drugs that damage DNA since Ki-67 staining is lost during the DNA repair process.