How EBV Causes Cancer
In order to cause cancer, EBV must "maintain it's viral genome in the cell, avoid killing the cell, and prevent the cell from becoming a target for destruction from the immune system. Finally the virus must activate cellular growth control pathways," (Thompson & Kurzrock, 2004). The EBV remains latent in the B cells and integrates its DNA into the host genome. In cancer-causing EBV, a gene called EBNA-1 is expressed, and the immune system doesn't detect it, so the cytotoxic T cells don't attack it. The EBV goes through the lyric cycle which suppresses protein synthesis in the host. Cell death then occurs which releases virions to infect more cells. The final step that makes EBV oncogenic is interfering with intracellular signals that control cell growth. This will result in rapid and uncontrolled growth, ultimately resulting in a malignant tumor. (Thompson & Kurzrock, 2004).
Hodgkin's Lymphoma
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It is believed that a history of infectious mononucleosis (caused by the EBV) increases a person's chance to develop Hodgkin's lymphoma. The distinguishing factor between non-Hodgkin's lymphoma and Hodgkin's lymphoma is an abnormal type of cells called Reed-Sternburg cells that are found solely in Hodgkin's lymphoma. Pieces of DNA from the EBV have been found in the Reed-Sternburg cells, suggesting that this virus may be the cause. It is most common in the United States, Europe, and Canada and occurs more commonly among high socioeconomic populations. It is speculated that it occurs among the wealthier populations because they may have been protected from the virus until much later in life than someone with a lower socioeconomic status (American Cancer Society, 2012).
Symptoms of Hodgkin's Lymphoma
- Enlargement of lymph nodes-usually neck, armpit, or groin. Usually not painful!
- Night sweats
- Severe and persistent itching
- Fatigue
- Loss of appetite
- Weight loss
- Fever that comes and goes
- Cough
- Trouble breathing while laying down
(American Cancer Society, 2012).
Diagnosis of Hodgkin's Lymhoma
Typically, patients will see their doctor when they have a lump on their neck, armpit, or groin that won't go away. The first step in diagnosing Hodgkin's is performing a biopsy. If the lymph node is near the surface of the skin, a local anesthetic is used to numb the skin while a small portion or the whole lymph node is removed for testing. If the lymph node is in the chest, the patient will be put under general anesthesia to have the biopsy done. Normally, a diagnosis can be made by examining the tissue underneath a microscope. Immunohistochemistry may be performed to confirm the diagnosis. With this test, a stain is used to identify surface proteins that are unique to Hodgkin's Lymphoma (American Cancer Society, 2012).
Treatment of Hodgkin's Lymphoma
- Chemotherapy
- Radiation
- Stem cell transplant
- Injecting antibodies that identify the surface proteins on Hodgkin's cells
(American Cancer Society, 2012).
Burkitt's Lymphoma
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Burkitt's Lymphoma is a type of Non-Hodgkin's lymphoma. It is a rare type of B-cell lymphoma. There are only about 300 new cases per year in the United States. Burkitt's lymphoma is more common in children and is found mainly in Africa, but there are sporadic cases world-wide. It is linked to the EBV, but not all patients with Burkitt's lymphoma have EBV. Endemic Burkitt's lymphoma only affects children who have had malaria, and it is believed that malaria lowers the resistance to the EBV. One of the distinctive features of endemic Burkitt's lymhoma is cancerous growths in the jawbone or other facial bones. Sporadic Burkitt's lymphoma, also called non-African Burkitt's lymphoma, is also tied to EBV but presents slightly differently. Sporadic Burkitt's lymphoma tends to affect the ileo-cecal region more than the jawbone. (Canadian Cancer Society, n.d).
Symptoms of Burkitt's Lymphoma
- Lymph nodes growing together
- Nodes that aren't tender
- Swollen nodes in abdomen or chest
- Abdominal pain
- Nausea and vomiting
- Diarrhea
- Bowel obstruction
- Weight loss
- Fever
- Night sweats
(Lymphoma Association, 2012)
Diagnosis
Diagnosis is made by a biopsy of the tissue that is affected. CT scans, ultrasounds, X-rays, and bone marrow biopsies are used to determine the stage of the cancer.
Stage I-One area outside of the lymph nodes are affected or one area of lymph nodes outside of the chest is affected.
Stage II-There is a tumor outside of the lymph nodes and nearby nodes are affected.
Stage III- There are tumors on both sides of the diaphragm.
Stage IV- The cancer has spread to the bone marrow or spinal cord.
(Stanford School of Medicine, 2001)
Treatment
- Chemotherapy
- Rituximab- a form of antibody therapy that targets a surface protein on B-lymphoma cells
(Lymphoma Association, 2012)
Nasopharyngeal Carcinoma
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Nasopharyngeal cancer starts in the back of the throat, behind the nose. All types of nasopharyngeal cancer start in the epithelial cells that line the surface of our body. This type of cancer isn't very prevalent in the United States, but occurs more commonly in China. The EBV is linked to nasopharyngeal cancer because parts of the EBV is found in almost all cancerous nasopharyngeal cells. Most patients with this type of cancer also have traces of the EBV in their blood as well (American Cancer Society, 2013).
Symptoms of Nasopharyngeal Carcinoma
- Lump in neck
- Headache
- Facial pain
- Double vision
- Chronic ear infections
- Nose bleeds
- Hearing loss
- Ringing in the ears
- Numbness in the face
- Nasal blockages or stuffiness
- Trouble opening mouth
(American Cancer Society, 2013).
Diagnosis of Nasopharyngeal Carcinoma
Typically, patients will consult their doctor about a lump in their neck. The doctor will perform a nasopharyngoscopy by either placing a scope through the nose or a small light with mirrors down the throat to inspect the nasopharynx. Not all tumors are visible with a physical exam, so a CT scan may be necessary. A biopsy is taken of the abnormal cells and they are examined underneath a microscope (American Cancer Society, 2013).
Treatment
- Chemotherapy
- Radiation
- Surgery
- Monoclonal antibodies- man-made antibodies that target a surface protein that signals growth
(American Cancer Society, 2013)
References
Burkitt lymphoma. (2001). Retrieved from Stanford School of Medicine website: http://surgpathcriteria.stanford.edu/bcell/burkitt/grading.html
Burkitt lymphoma. (2012, November 9). Retrieved from Lymphoma Association website: http://www.lymphomas.org.uk/sites/default/files/pdfs/Burkitt-lymphoma.pdf
Burkitt’s lymphoma. (n.d.). Retrieved from Canadian Cancer Society website: http://www.cancer.ca/en/cancer-information/cancer-type/non-hodgkin-lymphoma/pathology-and-staging/types-of-nhl/burkitt-s-lymphoma/?region=on
Dolcetti, R., Guenco, S., Dal Col, J., Celeghin, A., Mastorci, K., & De Rossi, A. (2014). Epstein-Barr virus and telomerase: from cell immortalization to therapy. Infectious Agents and Cancer, 9(8).
Hodgkin disease. (2012, December 10). Retrieved from American Cancer Society website: http://www.cancer.org/cancer/hodgkindisease/detailedguide/hodgkin-disease-treating-general-info
Nasopharyngeal cancer. (2013, September 23). Retrieved from American Cancer Society website: http://www.cancer.org/cancer/nasopharyngealcancer/detailedguide/nasopharyngeal-cancer-treating-general-info
