This activation can significantly alter clinical outcomes for patients

Aug 1, 2012 12:44 GMT  ·  By

Experts noticed some time ago that the outcome of certain cancer cases depended on activated immune cells that somehow managed to infiltrate tumors. Now, investigators find one of the locations where these cells can be activated, a piece of information that has eluded scientists for years.

The research effort was conducted by experts at the Ludwig Institute for Cancer Research, the de Duve Institute and the Cancer Center of Cliniques universitaires Saint-Luc in Brussels, Belgium.

The team says that, in a particular subset of metastatic melanoma patients, immune cells are activated within the microenvironment of the tumors themselves. Details of the study appear in the latest issue of the esteemed journal Cancer Research.

Previously, experts thought that lymphocytes, a powerful type of immune cells, could only be activated in specialized structures called lymph nodes. The new data provides researchers with a new frame of reference in dealing with melanoma.

The announcement was made by clinical and laboratory investigator Nicolas van Baren, MD, PhD, who holds appointments at all three research institutions. “Experts used to believe that lymphocytes became activated in lymph nodes and then migrated via the blood to the tumor,” he says.

What the new investigation uncovered is an alternative pathway that allows naive lymphocytes to become activated locally, in the microenvironment of the tumors themselves, without first having to pass through the lymph nodes.

“Fundamental knowledge like this is crucial as we seek to understand how tumors escape antitumor immune responses and how we can develop approaches to counter this,” van Baren explains.

The most common lymphocyte activation sites, besides the lymph nodes, are the spleen and the mucosal-associated lymphoid tissues. But chronic infections can lead to the emergence of ectopic lymphoid structures, which develop near infection centers.

These specialized formations were detected in numerous types of cancer, and proven to be active. Scientists observed the activation of B cell lymphocytes from these locations. “It is important to have established that immune responses can be generated locally, at least in skin metastases,” van Baren says.

“In fact, this last point, that we detected functional lymphoid structures in skin metastases and not in primary tumors, is extremely intriguing. We think that understanding the reasons for this difference will be highly informative in determining how antimelanoma immune responses develop during disease progression,” he concludes.