Tumors mimic key features of lymph nodes in order to create a tolerant microenviroment and escape attack from the immune system, say researchers from Ecole Polytechnique Fédérale de Lausanne in Switzerland.

The discovery, published in Science underscores the role of the lymphatic system in cancer and may open up new possibilities for cancer treatment.

Researchers studied a protein called CCL21 that is normally present in healthy lymph nodes to attract T cells and program them to perform vital immune functions. They found that some tumors can secrete this protein to transform the outer layer of the tumor into lymphoid-like tissue. This outer layer then attracts and effectively re-programs the T cells to recognize the tumor as friend not foe, resulting in a tumor that goes undetected by the immune system.

The tumor has transformed its outer layer into lymphoid-like tissue to avoid detection by the immune system.

(Photo Credit: EPFL)

"The tumor tricks the body into thinking it is healthy tissue," says lead author Melody Swartz, head of the Laboratory of Lymphatic and Cancer Bioengineering (LLCB) and EPFL professor.

Since most tumors progress only if they have escaped the immune system, this new understanding of one mechanism by which the tumor can bypasses or hides from immune defenses is an important step towards future cancer therapies.

The study also opens up potential novel areas of research focusing on the relationship between lymphatic systems and cancer research. According to Shields, the concept that tumors mimic lymphoid tissue to alter the host's immune response represents a new understanding of tumors' interactions with the lymphatic system.

Citation: Shields et al., 'Induction of Lymphoidlike Stroma and Immune Escape by Tumors That Express the Chemokine CCL21', Science, March 2010; doi:10.1126/science.1185837