Ki-67 is a nuclear protein that is expressed during various stages in the cell cycle, particularly during late G1, S, G2, and M phases. The protein has a forkhead associated domain (FHA) through which it associates with euchromatin at the perichromosomal layer, the centromeric heterochromatin, and the nucleolus. Ki-67 is shown to have a cell cycle dependent topographical distribution with perinucleolar expression at G1, expression in the nuclear matrix at G2, and expression on the chromosomes during M phase. Ki-67 is commonly used as a proliferation marker because it is not detected in G0 cells, but increases steadily from G1 through mitosis. Ki-67 antibodies are useful in establishing the cell growing fraction in neoplasms. In neoplastic tissues, the prognostic value is comparable to the tritiated thymidine-labelling index. The correlation between low Ki-67 index and histologically low-grade tumors is strong. Ki-67 is routinely used as a neuronal marker of cell cycling and proliferation.
Antigen identified by monoclonal antibody Ki-67; Antigen identified by monoclonal antibody Ki-67 homolog; Antigen KI-67; Antigen KI-67 homolog; Proliferation marker protein Ki-67; proliferation-related Ki-67 antigen; protein phosphatase 1, regulatory subunit 105; RP11-380J17.2; unnamed protein product