Understanding CD Markers in Cancer Diagnosis and Treatment

How CD Antigens are Used in Cancer and Lymphoma Diagnosis and Treatment

Lymphoma cancer cell, SEM. Credit: Steve Gschmeissner/Science Photo Library / Getty Images

CD markers or CD antigens, which stands for cluster of differentiation markers, are a group of special molecules on the surface of the cells in our body. All cells in our body have one or more of them. There are more than 250 types of CD molecules. They are most useful for classifying the white blood cells (WBCs), which are the type of cell in the blood that protects us from infections. Antibodies are specifically matched against each type of CD antigen.

This allows them to be used in tests to diagnose different types of lymphoma as well as being used for targeted immunotherapy.

Why CD Markers Are Important in Cancer Diagnosis

There are different types of WBCs and they don’t always look different. The most precise way to identify the different types is to see what CD molecules appear on their surface. This is especially important for diagnosis of blood cancers. Lymphomas and leukemias are cancers of WBCs. To find out the type of WBC affected and the exact type of leukemia and lymphoma, we need to identify the types of CD molecules that the cancer cells have.

As an example, two lymphomas diffuse large B-cell lymphoma (DLBCL) and anaplastic large cell lymphoma (ALCL) often look similar under the microscope with large cancer cells. Yet, their prognosis and treatments are different. CD markers can tell them apart. DLBCL is CD20 positive, while ALCL is CD20 negative but positive for CD30.

Pathologists often use CD markers to distinguish between different lymphomas.

Identification of CD Antigen Molecules

The molecules themselves cannot be seen with the eye. They are identified using antibodies –- matching molecules that will bind to the specific type of CD molecule and also show up under the microscope.

Using antibodies in the lab, samples from blood and lymph nodes can be checked for CD molecules and the type of cancer precisely determined.

CD Molecules in Cancer Treatment

Now, we have even better uses for CD molecules. Special drugs have been designed that identify and attack cells that have a particular type of CD molecule. These drugs are called monoclonal antibodies and they can attack only the type of cell that contains the specific target CD molecule. Monoclonal antibodies can also be tagged to drugs or radiation-emitting substances that add to the ability to kill cells that have the specific CD marker on their surface.

Examples of CD markers targeted in lymphoma treatment:

  • Rituxan (Rituximab) - a monoclonal antibody against CD20.
  • Zevalin (Ibritumomab Tiuxetan) - another antibody against CD20, tagged with a radiation emitting substance (Y90).
  • Bexxar (Tositumomab) - similar to Zevalin, only the radiation emitting substance is different (I131)
  • Gazyva (Obinutuzumab): targets CD20 antigen, used in initial treatment for small lymphocytic lymphoma/chronic lymphocytic leukemia.
  • Arzerra (Ofatumumab): targets CD 20 antigen, used in SLL/CLL.
  • Campath (Alemtuzumab): targets CD52 antigen in SLL/CLL and peripheral T-cell lymphomas.
  • Adcetris (Brentuximab vedotin): targets CD30 and is attached to a chemotherapy drug. Used in anaplastic large cell lymphoma.

Source:

Wintrobe's Clinical Hematology (11th Edition). Editors J.P. Greer, J. Foerster, J.N. Lukens. Published by Lippincott Williams & Wilkins.

Immunotherapy for non-Hodgkin Lymphoma, American Cancer Society, updated 01/22/2016.

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