Tuesday, September 20, 2011

An Immune System Trained to Kill Cancer

An Immune System Trained to Kill Cancer by Denise Grady from The New York Times September 12, 2011

The New York Times reported last week that scientists at the University of Pennsylvania might have discovered a new method of treating – or even curing – cancer. Dr. Carl June of UPenn’s Cancer Center tested a method of genetically engineering T-cells to specifically attack cancer cells in a patient with leukemia. Doctors removed about a billion T-cells – the white blood cells that fight infections – from the patient’s body by filtering his blood and then exposing the T-cells to an altered form of HIV-1. The HIV-1, a harmless variant that was altered to no longer cause AIDS, inserted a copy of a gene to produce chimeric antigen receptors (CARs) into the T-cells. HIV-1 is a retro-virus, which means that it carries enzymes which allow it to cut up parts of the genome and insert new DNA; in this case, the DNA it was inserting would strengthen rather than weaken the immune system. The CARs allowed the genetically modified T-cells to seek out the cancer cells and kill them. Once inside the body, these T-cells multiply and wipe out the cancer by destroying all B-cells – the blood cells affected by leukemia – that carry the CD19 protein on their surfaces. After the cancer is gone, memory cells are left behind to fight the cancer if it comes back. Once the B-cells have been destroyed, the patient is left essentially cancer-free.

So far, only three patients have undergone this treatment. Of the three, two went into complete remission, while the third went into partial remission. This treatment was only tested on patients with chronic lymphocytic leukemia and it is not clear if it would be work on other types of cancer. More tests will be needed to determine whether this treatment is truly as effective as it appears. At this point in time, no drug companies are testing genetic modification of T-cells to fight cancer and research is only in the beginning stages. There are certain risks that come with treatment: as the T-cells fight cancer, they cause high fever, low blood pressure, swelling and inflammation. In addition, the engineered T-cells can accidentally attack healthy tissues if the proteins on the tissues are too similar to the ones that the T-cells are supposed to kill, such as those cells that line the chest and abdomen. Treatment could also cause mimic lupus, an autoimmune disease. After treatment, memory cells remain behind to kill any future cancer cells, but they also attack normal B-cells, which leads to immunosuppression. Monthly intravenous immune globulin injections are required for protection from other illnesses. In spite of these risks, the genetic alteration of T-cells is an exciting new way of treating cancer that must be explored further to discover its true risks and benefits.

View the original article at: http://www.nytimes.com/2011/09/13/health/13gene.html?_r=1&scp=1&sq=cancer%20gene&st=cse

Image comes from source article

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