Science Series #3: Leukemia
What is leukemia?
Leukemia is a cancer of the early blood-forming cells; most often, it is of the white blood cells, but in some cases it starts in other blood cell types. There are several types of leukemia, which are divided based on if they are fast growing (acute) or slower growing (chronic), and whether it starts in myeloid cells or lymphoid cells.
If leukemia is suspected, the doctor will ask about any symptoms of leukemia and risk factors for the disease that the patient may have. A physical examination may reveal signs that leukemia may be present, such as swelling of lymph nodes, pale skin, or bruising. While notable if present, they can indicate other concerns.
(Source: American Cancer Society)
What cause leukemia?
Leukemia starts when the DNA of a single cell in the bone marrow changes (mutates) and cannot develop and function normally (DNA is the “instruction code” for the cell’s growth and function). All cells that arise from that initial mutated cell also have the mutated DNA.
The causes of mutated DNA is still unknown in all cases. Scientists have been able to locate changes in certain DNA sequences of patients diagnosed with leukemia. These changes can be inherited from a parent (as is sometimes the case with childhood leukemia) or they may happen randomly during a person’s lifetime if cells in the body make mistakes as they divide to make new cells.
(Source: Cleveland Clinic and American Cancer Society)
Types of leukemia?
The four most common types of leukemia are:
ALL is the most common in children. This type of leukemia begins in the B or T lymphocytes, which are immature white blood cells. Lymphocytes are the building blocks of the lymphoid tissues that make up the immune system. This type of disease can affect the bone marrow all over the body, and also spread to the Lymph nodes, Liver and Spleen.
Doctors further sub-classify ALL based on the variety and developmental stage of the lymphocyte involved.
AML is the most common type of acute leukemia in adults. It tends to progress quickly. It can affect any component of the blood and there are many subtypes of AML.
Blood stem cells in the bone marrow form into either:
- Lymphoid cells that become white blood cells.
- Myeloid cells that become red blood cells, white blood cells, or platelets.
In AML, myeloid stem cells usually mature into abnormal myeloblasts or white blood cells. However, they sometimes become abnormal red blood cells or platelets. As they multiply, they overwhelm the normal cells in the bone marrow and blood. The cancer cells can also spread to other parts of the body.
CLL accounts for about a third of leukemia diagnoses. It usually affects older adults. One form of CLL progresses slowly and symptoms may not appear until years after onset. Another form of CLL grows very quickly.
This disease begins in the B lymphocytes. As the abnormal cells proliferate, they crowd out the normal cells. More subtypes of CLL exist that affect other types of cells.
This type of leukemia is rare, only 10 percent of leukemia cases are CML and adults are more likely than children to develop it.
CML occurs when a genetic change turns the myeloid cells into immature cancer cells. These cells then grow slowly and overwhelm the healthy cells in the bone marrow and blood. A subtype of CML can form very quickly. This leukemia is hard to treat.
(Source: UPMC Hillman Cancer Center Community)
Is Leukemia Preventable?
Because the cause of this disease remains unknown, there is no certain way to prevent it. However, avoiding exposure to solvents, such as benzene and toluene, and unnecessary exposure to x-rays is generally a good practice. If you think you may be exhibiting signs of leukemia, being aware of the risk factors and symptoms and talking with your doctor are critical to an early diagnosis and treatment. It is especially important for people who have a family history of leukemia to be aware of symptoms and share their family medical history with their doctors.
(Source: American Society of Hematology)
Doing Our Part
The Jacinto Convit World Organization supports a free of cost molecular diagnostics program for the control and survival of patients affected by various types of cancer in developing countries. Through a strategic partnership with local NGOs, specialized tests are performed to detect ALL (TEL/AML1, MLL/AF4, TCF3/PBX1, BCR/ABL genes), AML (PML/RARa, FLT3/ITD, Inv. 16, AML1/ETO, BCR/ABL genes) and CML (BCR/ABL gene) in patients that are most in need.
To date, 12 genetic sequences based on these diagnoses are published in GenBank, a world reference sequence database of the National Center for Biotechnology Information (NIH); contributing to scientific advances in leukemia.