Engineered T Cells Versus Leukemia

The positive results of a cancer immunotherapy trial are noted here:

Nine of twelve leukemia patients who received infusions of their own T cells after the cells had been genetically engineered to attack the patients' tumors responded to the [therapy]. Two of the first three patients treated with the [protocol] remain healthy and in full remissions more than two years after their treatment, with the engineered cells still circulating in their bodies. The findings reveal the first successful and sustained demonstration of the use of gene transfer therapy to turn the body's own immune cells into weapons aimed at cancerous tumors.

The protocol for the new treatment involves removing patients' cells through an apheresis process similar to blood donation, and modifying them in [a] vaccine production facility. Scientists there reprogram the patients' T cells to target tumor cells through a gene modification technique using a HIV-derived lentivirus vector. The vector encodes an antibody-like protein, called a chimeric antigen receptor (CAR), which is expressed on the surface of the T cells and designed to bind to a protein called CD19.

The modified cells are then infused back into the patient's body following lymphodepleting chemotherapy. Once the T cells start expressing the CAR, they focus all of their killing activity on cells that express CD19, which includes [tumor] cells, and normal B cells. All of the other cells in the patient that do not express CD19 are ignored by the modified T cells, which limits systemic side effects typically experienced during traditional therapies.

In addition to initiating the death of the cancer cells, a signaling molecule built into the CAR also spurs the cell to produce cytokines that trigger other T cells to multiply - building a bigger and bigger army until all the target cells in the tumor are destroyed.

Link: http://www.eurekalert.org/pub_releases/2012-12/uops-lpr120712.php

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