In recent years, a standard follow-up to colorectal cancer surgery has been to analyze the tumor tissue for the presence of immune cells. Finding high quantities of cytotoxic T cells, or "killer cells", means that there is a good chance that the disease will take a favorable course and that the risk of metastasis is comparatively low.
It has been unclear whether the presence of T cells in tumor tissue is just a matter of chance in more benign tumors, or whether the immune cells are specifically and actively responding to the cancer and thus contribute to a more favorable prognosis. Their mere presence does necessarily mean that the body is mounting an immune response against the malignant tissue, because tumors have many ways to inactivate immune cells.
Professor Dr. Philipp Beckhove, an immunologist from the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ), has now collaborated with surgeons from Heidelberg and Dresden University Hospitals to investigate whether the T cells in colorectal tumors are in fact actively fighting the cancer.
Cytotoxic T cells that are activated because they recognize a specific characteristic of the tumor (a "tumor antigen") produce a combination of three immune mediators. In particular, activated killer cells produce high levels of tumor necrosis factor (TNF) alpha. Beckhove's research team found high TNF alpha levels exclusively in colorectal tumors from patients in whose blood or bone marrow they could also detect memory T cells that responded specifically to the tumor.
The scientists studied cytotoxic T cells that had been isolated from patient blood or tumor tissue. They discovered that only T cells which were simultaneously activated by specific tumor proteins produced TNF alpha. They found that the total quantity of TNF alpha in the tumor correlated to the number of killer cells producing it.
This was true for tissue samples from 88 colorectal cancer patients - could the results be extended to other patients as well? If so, levels of TNF alpha might serve as a valuable, independent biomarker that could be used in a prognosis for the disease. To test the idea, the scientists samples from another 102 bowel cancer patients
Read full article