A new target of anti–cancer therapy is tumor stroma

Many solid tumors develop complex mechanisms that prevent their recognition and destruction by cells of the immune system. Genetically unstable malignant cells often shed antigen-presenting surface structures that inform the immune system about the presence of pathological cells in the body. In the absence of these markers, leukocytes cannot recognize and destroy malignant cells. Often such tumors grow rapidly and do not respond to chemotherapy drugs or attempts to cause an antitumor immune response.

However, the tumor stroma – non-malignant cells surrounding and supporting the tumor, can accumulate tumor antigens and present them on its surface. These genetically stable cells containing tumor antigens and promoting tumor growth are a promising target for tumor immunotherapy.

According to the authors, the fact that the effect on the stroma is an important component of the treatment of large tumors was known earlier, but the effects of existing treatments are usually transient and nonspecific to tumors. Since cancer is a genetic disease, scientists have suggested that tumor cells can release protein products of mutated genes that subsequently accumulate in the stroma, and, accordingly, a tumor-specific effect on the stroma can lead to growth arrest and tumor destruction.

During the experiments, mice with large tumors were injected with specially modified T-lymphocytes that recognize tumor antigens. This did not have a direct effect on the tumor cells, but led to the death of the tumor stroma. As a result, the size of the tumors decreased, and their growth was suspended for more than 80 days.

Although complete elimination of tumors did not occur, such blocking of tumor growth is a significant achievement in the treatment of many types of cancer and can be used as an additional measure in complex treatment protocols. It is obvious that the destruction of the tumor is preferable than stopping its growth, but it is impossible to selectively affect cells that have lost tumor markers, therefore, in such cases, the ideal target for T-lymphocytes is the tumor stroma.

Theoretically, in this case, the accumulation of tumor antigens by healthy tissues of organs such as the spleen is possible, but during the work the authors did not observe this phenomenon.

In the near future, scientists plan to test the new approach on melanoma, as well as breast and colon cancers, whose stroma often presents tumor antigens. They are also considering the possibility of transferring the technique to human tumors and believe that it can be very useful for clinical medicine.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily

13.03.2008