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Lymphocytes From A Risk Group

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07.03.2006

The thyroid gland is very sensitive to ionizing radiation. The number of patients with thyroid gland cancer is particularly high among those who endured the Chernobyl catastrophe in childhood. Ultrasonic scanning and bioptic tests investigations are usually used for early detection of thyroid gland cancer but researchers do not stop the search of more efficient methods.

They deal with molecular markers of cancer in order to discover mutation of the genes participating in carcinogenesis. Unfortunately, the existing methods for search of mutant genes are labour-intensive and expensive, therefore they do not fit for mass use. However, there is no need to seek changes particularly in oncogenes. In case of malignant transformation, mutation frequency increases in all cells of the organism.

Thus, European researchers have discovered that people with increased frequency of chromosomal abnormalities in lymphocytes of blood more often fall ill with cancer. According to Japanese and Russian researchers’ data, the patients suffering from larynx cancer and some other malignant growths, even before treatment starts experience increase of quantity of lymphocytes with T-cell receptor (TCR) genes mutations. These mutations are easy to discover via a special immunological test, which was used by the Obninsk physicians for search of mutant lymphocytes in blood of patients with thyroid gland cancer.

The investigation involved venous blood of oncological patients (who had not undergone treatment yet) and that of healthy donors. Double increase of mutant lymphocyte frequency (more than 6.2 mutants per 10,000 cells) as compared to the background group was discovered with 37 percent of cancer patients, and this result cannot be considered accidental. Increased mutation frequency may be a hereditary trait - predisposition to genome instability, when probability of malignant transformation rises significantly. The same thing happens in case of some hereditary diseases (for example, Bloom’s syndrome, Fanconi anemia). Among the mutations discovered with patients with such syndromes, T-cell receptor mutations occupied a noticeable place.

After the Chernobyl catastrophe, a vast territory was exposed to contamination by radionuclids, and its inhabitants – to action of low ionizing radiation doses. Ionizing radiation leads to genetic instability. Among participants to the experiment, who lived in contaminated territories, the frequency of TCR-mutation made 45 percent. There is other indirect evidence as well that genotoxic influence, including ionizing radiation increase TCR-mutation frequency.

Therefore, a large number of mutant T-lymphocytes with a person means that their owner has become a prey to irradiation or his/her genome is non-stable for some reason. In this case, the patient should at least be attributed to a risk group, and it should be kept in mind that TCR-mutations are often found with oncological patients prior to treatment . This circumstance will help discover cancer at the very early stage.

Increased frequency of mutations in patient’s lymphocytes is the evidence of risk. But, unfortunately, the lack of mutation does not mean anything. Therefore, the researchers are going to continue the search for other molecular markers of cancer development. The more tests are used, the higher probability is to discover the risk.

Sergey Komarov | Source: alphagalileo
Further information: www.informnauka.ru

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