CD Markers in Cancer Diagnosis and Treatment

Using Cellular Tags to Create Targeted Therapies

Human breast cancer cell
Cultura Science/Rolf Ritter/Oxford Scientific/Getty Images

CD markers, also known as CD antigens, are specific types of molecules found on the surface of cells that help differentiate one cell type from another. In fact, the initials "CD" stands for "cluster of differentiation," the nomenclature of which was first established in 1982.

While some people may be familiar with the terms CD4 and CD8, which differentiate defensive immune cells known as T-cells, there are no less than 371 known CD antigens that "tag" virtually every cell of the body, providing each its own unique marker.

What CD Markers Tell Us

Among other things, CD markers are used to classify white blood cells produced by the body to help fight infection. These cells are central components of the immune system which work in tandem to identify, target, and neutralize disease-causing pathogens.

For example, CD4 T-cells are referred to as "helper cells" because their role is to signal "killer" CD8 T-cells to attack and neutralize a specific pathogen.

By understanding these dynamics, scientists can use CD markers to not only evaluate the status of an infection (measured by an increase or decrease in cell numbers) but measure the strength of the immune system itself. Certain conditions such as HIV and organ transplantation are associated with immune suppression, meaning that the body is less capable of mounting an immune defense as evidenced by the absence of CD4 T-cells.

Prior to the introduction of the CD nomenclature, evaluating a person's immune function was far more difficult and non-specific.

CD Markers in Cancer Diagnosis and Treatment

In addition to monitoring infection and immune status, CD antigens can be used to detect the abnormal growth of cells known as a neoplasm. Neoplasms may be benign (non-cancerous), malignant (cancerous), or precancerous, but, like any other cell, have CD markers that scientists can use to identify them.

CD markers are not only important in the diagnosis of cancer, they can help identify which types of treatment may be most successful and measure how effective the treatment is by monitoring changes in the relevant CD markers.

Moreover, researchers are today able to create a type of defensive protein, known as a monoclonal antibody (mAb), which is matched to a specific CD antigen. These cloned antibodies mimic those produced by the body and can be used to fight cancer in a form of treatment known as targeted immunotherapy.

When injected into the body, mAbs can act in distinctive ways depending on their design:

  • They might bind to the CD marker on cancer cells and destroy them.
  • They might bind to the CD marker on cancer cells and block their ability to replicate, stopping or slowing their growth.
  • They might amplify the body's natural defense specific to that cancer.

Outside of the body, mAbs are commonly used in diagnosis to detect specific CD antigens in blood, tissue, or body fluid samples.

Targeted Immunotherapy for Cancer

Monoclonal antibodies are today used to treat many different diseases, including some autoimmune disorders and certain types of cancer. Their effectiveness can vary, with some cancers responding better than others.

With that being said, advances in genetic technology have led to a growing number of approved immunotherapeutic agents. As opposed to older generation chemotherapy which targets fast-replicating cells, both cancerous and healthy, these newer generation drugs target only those cells with a specific CD "tag."

Among the drugs currently approved by the U.S. Food Drug Administration for use in cancer immunotherapy:

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Article Sources
  • American Cancer Society. "Monoclonal antibodies to treat cancer." Atlanta, Georgia; updated October 2017.
  • Vanneman, R. and Dranoff, G. "Combining immunotherapy and targeted therapies in cancer treatment." Nat Rev Cancer. 2012: 12:237-51. DOI:10.1038/nrc3237.