The body's immune system is able to identify the cancerous cells of a tumor and launch an attack against them (the cancerous growth just often overwhelms the body's capabilities). Immunotherapies aim to destroy cancer by enhancing the efficacy of this natural system.
In the video, T lymphocytes (green) attack a tumor (blue and orange). In vivo real-time experiments indicate T lymphocytes act both locally and remotely within the tumor. © Ronan Thibaut and Philippe Bousso, Institut Pasteur / Inserm
Scientists have now learned more about how the immune system tries to limit the growth of tumors. Researchers have used imaging tools on a mouse model to view the movement of immune cells called T lymphocytes as they launched both a local and a remote attack on tumors. The findings have been reported in Nature Cancer.
T lymphocytes can infiltrate tumors and destroy the cancerous cells that they are made of, one by one, using direct contact. This phenomenon is highly localized, and occurs only in the immediate vicinity of these killer T cells. The T lymphocytes produce and release molecules called cytokines. In this research, the scientists aimed to learn more about how one cytokine in particular, called interferon-gamma (IFN-γ), impacts the tumor microenvironment.
The researchers used powerful imaging tools to watch how T lymphocytes behaved in real-time in live mice. They also observed how the IFN-γ was affecting cells within tumors. They saw that the cytokines were not acting locally; they quickly dispersed inside the tumor as well as impacting cells that were farther away from the T cells.
"This remote action within the tumor is very interesting because it enables T lymphocytes to act on a large number of cancer cells, especially those that may have developed mechanisms to escape the immune system," explained the lead study author Philippe Bousso, an Inserm researcher and Head of the Dynamics of Immune Responses Unit at the Institut Pasteur.
The investigators also showed that cytokine levels and the response to the cancer were linked to the number of T lymphocytes that were successfully able to get into the tumor. An analysis of cells from melanoma patients supported the idea that immune cells can act remotely. It may, therefore, be possible to stimulate this response as part of an immunotherapy strategy.