Studies link lymph vessels to cancer growth
ATLANTA, Georgia -- Preventing the growth of lymph vessels, not just blood vessels, may be a way for doctors to treat cancer, according to three new studies on human cancer growth cell in mice.
"If lymphatic vessels are involved in keeping tumors alive, blocking these lymphatic pathways could provide more targets than just tumor cells themselves," said Dr. Christopher Widnell, scientific program director of the American Cancer Society.
Published in the journal Nature Medicine, the studies found that tumors not only need their own blood supply to survive, but they also need to form lymph vessels to allow cancer to spread. The formation of lymph vessels is called lymphangiogenesis.
This is an important discovery because it's the "first direct experimental evidence that tumors create their own lymph vessels, not just blood vessels, which may contribute to the spread of cancer," said Dr. Nicole McCarthy from the National Cancer Institute in Rockville, Maryland. The research presented in Nature Medicine, however, is preliminary and "needs to be substantiated with many more studies," she said.
Immune cells in the lymph nodes are essential in fighting infections. The lymphatic system, which consists of vessels and nodes, acts as a filter for foreign substances, including cancer cells. Scientists theorize that a tumor's own lymph system provides an entry into the body's system, which then helps the cancer spread.
"It is well known that many cancers, such as breast cancer, metastasize to the lymphatic vessels," said Dr. Michael Detmar, co-author of one of the studies. But it was thought that tumors did not have functional lymphatic systems. In Detmar's study, scientists discovered a direct correlation between the density of lymphatic vessels in breast cancer tumors and its potential to spread to the lymph nodes and lungs.
In the past few years, scientists have focused on ways to cut off a tumor's blood supply to starve and eventually kill a tumor -- a process called anti-angiogenesis.
If the results from the newest studies are confirmed in larger trials, it could prompt researchers to further explore ways to block a tumor's lymphatic development as well.
In the studies, scientists also reported that certain types of tumors were more likely to spread because of lymph node growth. Two studies found tumors in mice that had high levels of proteins called VEGF-C and VEGF-D were much more likely to spread. Determining the levels of lymphatic-vessel growth and proteins in tumors could eventually "be used as a new diagnostic tool" said Detmar, an associate professor of dermatology at Harvard Medical School.
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