How to kill tumor-supporting macrophages

Researchers at the University of Washington, working under the guidance of Associate Professor Suzie H. Pun, have developed a new strategy to slow tumor growth and increase life expectancy by selectively destroying immune cells that suppress the body's response to cancer.

The immune system of a healthy body usually recognizes and destroys malignant cells that periodically appear in it. However, one of the types of immune cells – macrophages – is capable of "betrayal" under the influence of signals coming from a cancerous tumor. Once inside the tumor, these cells sometimes lose the ability to act on the side of the body and, conversely, begin to suppress the immune response directed against the tumor. The results of several studies have demonstrated the existence of a positive correlation between a large number of macrophages in a tumor biopsy sample and a poor prognosis for the patient.

Until now, specialists have not been able to find a way to selectively destroy tumor-associated macrophages, and the complete elimination of these cells from the body means a strong decrease in immunity.

The authors proposed an original solution to this problem using the M2pep peptide developed and synthesized by them, specific to the molecular target on the surface of tumor-associated macrophages. A study of the tissues of mice with colon tumors after injection into the tail vein of M2pep showed that this peptide binds to target cells with a high degree of selectivity and does not interact with other leukocytes or cells of healthy organs.
The introduction of the M2pep complex and the proapoptotic protein to animals led to the selective destruction of macrophages inside tumors. The result was a slowdown in tumor growth and better survival of mice in the experimental group.

Stained section of a mouse tumor: macrophages are colored red,
the green color indicates the presence of a macrophage-binding peptide.

The authors believe that this strategy should show good results when used simultaneously with traditional chemotherapy. In the near future, they plan to test the effectiveness of its use in conjunction with existing anticancer drugs. The next stage of the work will be the search and synthesis of a peptide specific to human tumor-associated macrophages.

Article by Maryelise Cieslewicz et al. Targeted delivery of proapoptotic peptides to tumor-associated macrophages improves survival is published in the journal PNAS.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of the University of Washington:
Depletion of ‘traitor’ immune cells slows cancer growth in mice.

19.09.2013