A team of researchers at the National Cancer Institute (NCI), part of the National Institutes of Health (NIH), has demonstrated sustained regression of advanced melanoma in a study of 17 patients by genetically engineering patients' own white blood cells to recognize and attack cancer cells.
Autologous lymphocytes — a person's own white blood cells — have previously been used to treat metastatic melanoma. In a process called adoptive cell transfer, lymphocytes are first removed from patients with advanced melanoma. Next, the most aggressive tumor-killing cells are isolated, multiplied in the lab, and then reintroduced to patients who have been depleted of all remaining lymphocytes. While reasonably successful, this method can only be used for melanoma patients and only for those who already have a population of specialized lymphocytes that recognize tumors as abnormal cells.
Thus, NCI researchers, led by Steven A. Rosenberg, M.D., Ph.D., sought an effective way to convert normal lymphocytes in the lab into cancer-fighting cells. To do this, they drew a small sample of blood that contained normal lymphocytes from individual patients and infected the cells with a retrovirus in the laboratory. The retrovirus acts like a carrier pigeon to deliver genes that encode specific proteins, called T cell receptors (TCRs), into cells. When the genes are turned on, TCRs are made and these receptor proteins decorate the outer surface of the lymphocytes. The TCRs act as homing devices in that they recognize and bind to certain molecules found on the surface of tumor cells. The TCRs then activate the lymphocytes to destroy the cancer cells.
The study appears in the online edition of the journal Science on August 31, 2006.
NCI Media Relations Branch
Message posted by: Rashmi Nemade
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