24 September 2012

Natural killers protect against lung cancer

Why not all smokers get lung cancer

Kirill Stasevich, Compulenta

Immune cells have been found, which determine whether a person is at risk of getting lung cancer.

Although doctors constantly warn that smoking causes lung cancer, not every smoker is susceptible to this disease. This means that a person has mechanisms that can resist the influence of harmful substances contained in tobacco. And these mechanisms work better for some, and worse for others.

Researchers from Washington University in St. Louis (USA) suggested that it's all about the difference in immunity. The immune system monitors not only bacteria and viruses, but also malignant cells: if an oncocell appears somewhere, the immune system destroys it. And since there are people who are especially susceptible to colds due to weak immunity, there are also those who suffer from cancer more often because of this. But in the case of colds and cancer, different parts of the immune system monitor the order, and researchers undertook to find out which guard cells prevent the development of cancer, and even more specifically, lung cancer.

To do this, scientists gave mice a strong carcinogen, after which the animals were divided into three groups: those who calmly suffered a harmful substance, those who had a tumor in their lungs quickly, and those who also had cancer, but not too aggressive. Then lymphocytes called "natural killer cells" (NK cells) were removed from healthy mice. They are known to be involved in antitumor defense, and this was confirmed again: without NK cells, healthy mice instantly developed a lung tumor.

And vice versa: As the researchers write in the journal Cancer Research (Kreisel et al., Strain-Specific Variation in Murine Natural Killer Gene Complex Contributes to Differences in Immunosurveillance for Urethane-Induced Lung Cancer), manipulations with bone marrow made it possible to significantly suppress the disease in mice with cancer. The new, transplanted bone marrow produced more energetic, more skillful NK cells that could resist the tumor. The researchers point out that the difference in the "varieties" of these cells was reflected in the sequence of certain regions on the 6th chromosome, where the genes responsible for the activity of NK cells are located. Obviously, with negligent cells, lung cancer can occur without the help of a carcinogen.

Not only "natural killers" take part in the antitumor response of the immune system. In the case of tumors of the mammary glands, intestines and prostate, T-lymphocytes play an important role. However, with lung cancer, they turn off for some reason, and then everything depends on NK cells. Strictly speaking, the main result of the study is not even that the responsibility for cancer was assigned to poor immunity (the role of immunity in the development of cancer has been known for quite a long time), but that it was possible to find out which immune cells protect us from a specific tumor, in this case from lung cancer.

Now the authors of the work have started a second series of experiments, intending to compare cellular and immune parameters in humans to find out whether the results of the "mouse" study can be extended to humans.

Prepared based on the materials of Washington University in St. Louis:
Key immune cell may play role in lung cancer susceptibility.

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