Normal cells help to survive cancer during chemotherapy

Sometimes cancer cells from the very beginning can withstand chemotherapy: as it turned out, they receive this "gift" from the proteins of healthy cells surrounding the tumor.

In modern medicine, cancer is preferred to treat, causing pinpoint strikes on the tumor. Cancer cells are looking for a specific mutation, and the drug is aimed at a specific cancerous mutant protein. Such chemotherapy is much better than usual, in which the whole organism is filled with poison, which affects not only the tumor, but also healthy tissues.

However, the effectiveness of such therapy in the laboratory is incomparable with the clinical results. Cancer cells in a test tube are dying together from the medicine specially created for them - and in patients all this has only a partial and (or) temporary effect. So, for example, things are going on with melanoma: for the treatment of this type of tumor, an inhibitor of the RAF protein was created, which has a specific mutation in melanoma cells. In some patients, the response to therapy was more than noticeable, and the malignant cells almost completely disappeared, and in other cases the tumor only retreated a little, showing surprising stability. And here it is worthwhile to clarify that this is not an acquired trait: the resistance to drugs that appears in cancer cells after therapy is another, though more familiar, problem of oncology. In this case, the cancer cells seem to initially have something that protects them from death as a result of purposeful treatment with the drug.

This riddle was solved by two research groups - from the company Genetech and the Institute of Broad (USA). Genetech specialists tested 41 lines of various cancer cells for primary resistance to drugs, from a breast tumor to lung and skin tumors. In an article published in the journal Nature, they write that the cells resisted drugs only in the presence of a protein cocktail taken from the tumor stroma - that is, from normal cells surrounding the tumor and serving as a support for it.

The second group of scientists cultivated several types of cancer cells, again adding normal to them. The cancer cells grown on their own died from drugs, but if they were normal with them, then in more than half of the cases the tumor survived. That is, it turns out that the legendary immortality of cancer is at least partly provided by healthy tissues. In an article published in the same journal, researchers from the Broad Institute report that they have been able to identify a protein that secrete normal cells and that helps cancer cells survive during a "chemical attack". Approximately 500 secreted proteins were analyzed, and as a result, HGF, or hepatocyte growth factor, turned out to be "extreme". It binds to one of the receptors of cancer cells, as a result of which melanoma cells become resistant to a drug aimed at a mutant RAF protein. It was previously established that the hyperactivity of this receptor is related to tumor growth.

These results were confirmed in clinical experiments. In patients with a high level of HGF, targeted antitumor therapy did not give the proper effect, whereas at a low level of HGF the drug caused a sharp decrease in the tumor. That is, for full-fledged treatment it is necessary to beat not only the cancer protein, which is important for the life of the cancer cell, but also the receptor by which the oncoclet receives help from the healthy ones.

The data obtained are of great fundamental and practical importance, but their implementation in everyday clinical practice will be very difficult. The HGF aid protein may be important only for the melanoma with which the researchers worked. Other types of cancer can use other proteins, and for each of them it is necessary to do a great job to identify these proteins.

In this connection, the question arises: will not chemotherapy, which together with cancer cells kill healthy people, and so are able to deprive the tumor of hope of salvation, return to its advantage?

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