How does leukemia develop
Leukemias are a group of diseases that are also known as blood cancers . They make up about 2.4 percent of all cancers in adults and are therefore relatively rare – much rarer than, for example, lung cancer, colon cancer or breast cancer.
In children, however, leukemia is much more common: it accounts for about a third of all cancers. The causes of leukemia are not yet entirely clear, but various factors are known that increase the risk of developing the disease.
How does leukemia develop – leukocytes flood the blood
The word “leukemia” comes from the Greek and means “white blood”. This designation comes from the fact that the white blood cells, the leukocytes , multiply extremely strongly in leukemia . This leads to massive proliferation of a cell clone, so that many similar cells of a specific cell line are formed. These cells are flushed out of the bone marrow and are found in the blood. They can also infiltrate other organs.
The symptoms caused by leukemia arise on the one hand from the infiltration of organs and on the other hand from the fact that the massive proliferation of the cell clone suppresses normal blood formation from the bone marrow. The infiltrated organs are usually the spleen or the liver, which can enlarge and cause abdominal pain.
The suppression of healthy blood formation leads to various symptoms depending on the cell line:
- The repression of erythropoiesis leads to anemia. This can lead to paleness, tiredness, a drop in performance or shortness of breath during exertion.
- Too few platelets in the blood result in a tendency to bleed, which can manifest itself in increased nosebleeds or bleeding gums. Bruises or small, punctiform hemorrhages in the skin are also typical.
- The malignant cell clones are often not functional, so that there are not enough functional leukocytes in the blood despite massive leukocytosis . This manifests itself in a pronounced feeling of illness, fever and an increased susceptibility to infections.
What types of leukemia are there?
A distinction can be made between acute and chronic leukemias and between the lymphatic and myeloid forms. There are four different forms of leukemia:
- Acute myeloid leukemia (AML)
- Acute Lymphocytic Leukemia (ALL)
- Chronic Lymphocytic Leukemia (CLL)
- Chronic myeloid leukemia (CML)
How does leukemia develop – risk factors
Even if the causes of leukemia have not yet been fully clarified, it has been observed that certain risk factors lead to an increased rate of diseases.
- Nicotine use : It is estimated that about 10 percent of all leukemias are caused by cigarette smoking. The harmful substances in cigarettes not only increase the risk of lung cancer, but also of all other types of cancer. In the case of leukemia, the risk of developing smokers is about 40 percent higher than that of non-smokers. Ex-smokers also have an increased risk of developing the disease.
- Radioactive radiation : After the atomic bombs exploded in Hiroshima and Nagasaki, it was shown that the released radioactive radiation significantly increased the incidence of leukemia. X-rays also increase the likelihood of getting sick. Radiation exposure damages DNA, particularly in cells that divide frequently. These include the blood-forming cells in the bone marrow, which are particularly vulnerable.
- Chemical substances : There are various chemicals that can also promote the occurrence of leukemia. These include benzene and other solvents, pesticides or insecticides.
- Medications : Certain medications can also cause leukemia as a long-term consequence. B
In some patients who have been treated with cytostatics as part of chemotherapy , leukemia develops years later as a result of the damage caused to the bone marrow.
The treatment of cancer must therefore always be carefully considered by doctors and placed in a benefit-risk ratio.
However, since most cancers are fatal sooner or later without treatment and treatment-related leukemia is very rare, the decision is usually made in favor of chemotherapy. Drugs for immunosuppression, which are used after organ transplants, for example, also increase the risk of leukemia.
Not only is the rejection of the foreign organ suppressed in the body, but the defense against malignant cells is also reduced.
– Viruses: A very rare special form of T-cell ALL is triggered by HTLV-1 and HTLV-2 viruses. However, it hardly occurs in Germany, but mainly in Japan and the Caribbean.
– Underlying hematopoietic disease: Leukemia can develop over time from other diseases that are associated with a disorder of hematopoiesis. These include, for example, a myelodysplastic syndrome, aplastic anemia or myeloproliferative syndromes. Acute myeloid leukemia (AML) usually develops from this.
Is leukemia hereditary?
Whether leukemia is hereditary has not yet been determined with certainty. However, it has been observed that the risk of developing the disease is increased if there is an increased incidence of malignant diseases in the family. Thus, a hereditary component is likely.
It has also been shown that leukemia occurs at an increased rate in hereditary diseases. For example, patients with Down syndrome are about 20 times more likely to develop leukemia.
In some types of leukemia, certain chromosomal changes can also be detected. These are usually translocations, in which a piece of a chromosome breaks off and joins another chromosome.
As a result, fusion genes are formed, from which faulty proteins are produced. These in turn lead to the development of leukemia. The best-known example is a translocation between chromosomes 9 and 22, which gives rise to the BCR-ABL fusion gene.
The resulting chromosome is called the Philadelphia chromosome and is found in almost all patients with chronic myeloid leukemia (CML). However, these mutations are not congenital and cannot be inherited.
Molecular mutations in certain proteins can also cause leukemia. Most commonly involved are kinases that regulate cell division. A mutation can increase the activity of the kinases and cause increased cell division in the leukocytes. An example is the FLT3 kinase mutation found in some patients with AML.
So far, certain dispositions to leukemia have turned out to be hereditary, but the disease itself cannot be inherited as things stand at present.
Therapy: stop the development of malignant cells
In order to treat leukemia, all malignant cells must be killed, otherwise it can always come back. However, because healthy tissue can only tolerate a certain amount of chemotherapy without dying itself, there are limits to drug therapy.
“Stem cell transplantation is still the only chance for many patients.
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Sources and literature
www.krebsgesellschaft.de/onko-internetportal/basis-informationen-krebs/krebsarten/leukaemie/
Gerd Herold, Internal Medicine 2017, Chapter “Leukemia”, p. 95ff.
