Ki-67 (protein)

Antigen KI-67 also known as Ki-67 or MKI67 is a is_associated_with::protein that in humans is encoded by the MKI67 is_associated_with::gene (antigen identified by monoclonal antibody Ki-67).

Function
Antigen KI-67 is a nuclear protein that is associated with and may be necessary for cellular proliferation. Furthermore it is associated with is_associated_with::ribosomal RNA transcription. Inactivation of antigen KI-67 leads to inhibition of ribosomal RNA synthesis.

Use as cell marker
The Ki-67 protein (also known as MKI67) is a cellular marker for proliferation. It is strictly associated with is_associated_with::cell proliferation. During is_associated_with::interphase, the Ki-67 is_associated_with::antigen can be exclusively detected within the is_associated_with::cell nucleus, whereas in is_associated_with::mitosis most of the protein is relocated to the surface of the is_associated_with::chromosomes. Ki-67 protein is present during all active phases of the is_associated_with::cell cycle (G1, S, G2, and mitosis), but is absent from resting cells (G0).

Antibody labeling
Ki-67 is an excellent marker to determine the growth fraction of a given cell population. The fraction of Ki-67-positive is_associated_with::tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of is_associated_with::cancer. The best-studied examples in this context are is_associated_with::carcinomas of the is_associated_with::prostate, is_associated_with::brain and the is_associated_with::breast and nephroblastoma. For these types of tumors, the prognostic value for survival and tumor recurrence have repeatedly been proven in uni- and multivariate analysis.

MIB-1
Ki-67 and is_associated_with::MIB-1 monoclonal antibodies are directed against different epitopes of the same proliferation-related antigen. Ki-67 and MIB1 may be used on fixed sections. MIB-1 is used in clinical applications to determine the Ki-67 labelling index. One of its primary advantages over the original Ki-67 antibody (and the reason why it has essentially supplanted the original antibody for clinical use) is that it can be used on formalin-fixed paraffin-embedded sections, after heat-mediated antigen retrieval (see next section below).

Original Ki-67 antibody
The Ki-67 protein was originally defined by the prototype monoclonal is_associated_with::antibody Ki-67, which was generated by immunizing mice with nuclei of the is_associated_with::Hodgkin lymphoma cell line L428. The name is derived from the city of origin (is_associated_with::Kiel, Germany) and the number of the original clone in the 96-well plate.

Interactions
Ki-67 (protein) has been shown to interact with is_associated_with::CBX3.