What is the Difference Between Ki67 and BrdU

The key difference between Ki67 and BrdU is that Ki67 is a specific protein commonly used in the detection of proliferating cells in living tissues, while BrdU (bromodeoxyuridine) is a synthetic nucleoside commonly used in the detection of proliferating cells in living tissues.

Cell proliferation increases the number of cells. It is usually defined by the balance between cell divisions and cell loss through cell death or differentiation. In tumours, cell proliferation is increased. Cell proliferation can be measured through compounds or dyes incorporated into live cells. Cell proliferation can also be measured by detecting the expression of certain proteins called proliferation markers in live cells. Ki67 and BrdU are two types of proliferation markers used to detect cell proliferation.

CONTENTS

1. Overview and Key Difference
2. What is Ki67  
3. What is BrdU
4. Similarities – Ki67 and BrdU
5. Ki67 vs BrdU in Tabular Form
6. Summary – Ki67 vs BrdU

What is Ki67?

Ki67 is a specific protein commonly used in the detection of proliferating cells in living tissues. It is also known as antigen-Ki67 or MKI67. The human gene MKI67 codes this protein. This protein is also associated with ribosomal RNA transcription. Inactivation of antigen Ki67 leads to inhibition of ribosomal RNA synthesis. Ki67 is a protein in cells that increases when the cells prepare to divide into new cells. A staining process can measure the percentage of tumour cells that are positive for KI67. The presence of more positive cells indicates that cells divide and form new cells more quickly.  In breast cancer, a result of less than 10% is considered low, 10-20% borderline, and high if more than 20%.

Ki67 is present during all active phases of the cell cycle (G1, S, G2, and M). But it is absent in the resting cells (G₀). Therefore, the nuclear expression of Ki67 can be evaluated to assess tumour proliferation by immunohistochemistry (IHC). Moreover, it is a popular proliferation marker routinely used in pathology labs due to its diagnostic capability.

What is BrdU?

BrdU (bromodeoxyuridine) is a synthetic nucleoside commonly used in the detection of proliferating cells in living tissues. To proliferate, cells need to produce DNA during the S phase. Therefore, a reliable method for assessing cell proliferation is the measurement of DNA synthesis. Generally, this is done by incubating live cells with compounds or dyes which can easily be incorporated into newly synthesized DNA.

Thymidine analogues are the most popular compound for incorporation into DNA. Therefore, BrdU is a thymidine analogue that is generally used in the detection of proliferating cells in living tissues. BrdU can be incorporated into the newly synthesized DNA of replicating cells during the S phase. This is because it substitutes thymidine during DNA replication. IHC detection of BrdU incorporation into DNA is a powerful technique to study the cytokinetic of normal and tumour cells. Moreover, BrdU labelling of tumour cells involves steps such as the incorporation of BrdU into DNA and specific detection of incorporated BrdU with anti-BrdU antibodies, etc.

What are the Similarities Between Ki67 and BrdU?

• Ki67 and BrdU are two types of proliferation markers used in the detection of cell proliferation.
• Both markers can be used to differentiate normal and tumour cells.
• They can label cells in the S phase.
• Both markers show similar expression patterns.
• They show high reliability.

What is the Difference Between Ki67 and BrdU?

Ki67 is a specific protein that is commonly used in the detection of proliferating cells in living tissues, while BrdU is a synthetic nucleoside that is commonly used in the detection of proliferating cells in living tissues. So, this is the key difference between Ki67 and BrdU. Moreover, Ki67 labels cells in G1, G2, S and M phases of the cell cycle while BrdU labels cells only in the S phase of the cell cycle.

The following infographic lists the differences between Ki67 and BrdU in tabular form for side by side comparison.

Summary – Ki67 vs BrdU

Ki67 and BrdU are two types of proliferation markers that are useful in the detection of cell proliferation. Ki67 is a specific protein, while BrdU is a synthetic nucleoside. Thus, this is the key difference between Ki67 and BrdU. Ki67 is able to label the cells in the G1, G2, S and M phases of the cell cycle. In contrast, BrdU labels cells only in the S phase of the cell cycle.

Reference:

1. “Ki-67 (Protein).” An Overview | ScienceDirect Topics.
2. “Bromodeoxyuridine.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Protein MKI67 PDB 1r21″ By Emw – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “GFAP and BrdU double labeling in the rat subrganular zone” By Charlotte A. Oomen, Carlos E. N. Girardi, Rudy Cahyadi, Eva C. Verbeek, Harm Krugers, Marian Joëls, Paul J. Lucassen – Opposite Effects of Early Maternal Deprivation on Neurogenesis in Male versus Female Rats (CC BY 2.5) via Commons Wikimedia