Kiwix

Overview

Ki-67 is a nuclear protein that is associated with cellular proliferation. It is widely used as a proliferation marker in the study of cancer and other diseases. The Ki-67 protein is present during all active phases of the cell cycle (G1, S, G2, and mitosis), but is absent from resting cells (G0). This makes it an excellent marker for determining the growth fraction of a given cell population.

History

The Ki-67 protein was first identified in the early 1980s by the team of Dr. Johannes Gerdes. The name "Ki-67" is derived from the city of Kiel, Germany, where the research was conducted, and the clone number 67 of the original monoclonal antibody used to detect the protein.

Structure and Function

Ki-67 is a large protein with a molecular weight of approximately 345 kDa. It is encoded by the MKI67 gene located on chromosome 10. The protein is characterized by a unique structure that includes a series of tandem repeats and a forkhead-associated domain. Ki-67 is thought to play a role in maintaining chromosomal stability and is involved in the organization of the nucleolus.

Clinical Significance

Ki-67 is a crucial marker in oncology, particularly in the assessment of tumor proliferation. High levels of Ki-67 expression are often associated with aggressive tumor growth and poor prognosis in various cancers, including breast cancer, prostate cancer, and gliomas. The Ki-67 labeling index, which measures the percentage of Ki-67-positive cells in a tumor sample, is used to guide treatment decisions and predict outcomes.

Diagnostic Use

In clinical practice, Ki-67 is detected using immunohistochemistry (IHC) on formalin-fixed, paraffin-embedded tissue sections. The Ki-67 labeling index is calculated by counting the number of positively stained nuclei in a given area and expressing it as a percentage of the total number of nuclei.

Research Applications

Beyond its use in cancer diagnostics, Ki-67 is also employed in research to study cell proliferation in various biological contexts, including embryonic development, tissue regeneration, and response to therapeutic interventions.

Limitations

While Ki-67 is a valuable marker for cell proliferation, its interpretation can be challenging due to variability in staining techniques, scoring methods, and inter-observer differences. Standardization of protocols and scoring systems is essential to improve the reliability of Ki-67 as a prognostic tool.

Also see

• Cell cycle
• Immunohistochemistry
• Tumor markers
• Proliferation marker
• Breast cancer