Encapsulating cancer therapies
A single injection of living drug "factories" can shrink tumors in mice by cutting off their blood supply, raising hopes for potentially less toxic cancer treatments in humans.
Tumor cells, which need oxygen and nutrients to continue to grow, stimulate the growth of networks of new blood vessels—a process called angiogenesis. In theory, cutting off the blood supply by blocking angiogenesis could stall the cancer’s growth or even kill it. However, natural angiogenesis inhibitors are not effective medicines because they are quickly degraded in the body. To overcome this obstacle, researchers have found a way to deliver the agent using cell "factories."
Teams led by Rona Carroll and Mary-Ann Read [Nature Biotechnology, Vol. 19, Issue 1, 01 Jan 2001] genetically engineered baby hamster kidney cells in the test tube to secrete endostatin, a natural angiogenesis inhibitor. The cells were then coated in a jelly-like substance, rendering them invisible to the host’s immune system but still able to "breathe." The capsules were then injected into mice to study their effect on glioblastoma, an aggressive form of cancer.
In Carroll’s study, just a single injection of the capsules close to a tumor that had been grown under the mouse’s skin reduced the weight of the tumor by over 70%. Read’s group took a different approach, injecting the capsules into the brain before a cancer was induced. In this case, a single injection slowed the growth of the cancer and prolonged survival of the rats by up to 70%. Although the cancer was not cleared completely by either approach, the work suggests that local delivery of angiogenesis inhibitors using living drug "factories" is feasible.
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(News & Views)
Gabriele Bergers and Douglas Hanahan
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Hormone Research Institute
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