From Scientific American:
Lead study author Cassian Yee, an immunologist, says that he and his team removed so-called CD4+ T cells (a type of infection-fighting white blood cell) from a 52-year-old man with stage IV (the most advanced) melanoma—the deadliest form of skin cancer; it had spread to a lung and a groin lymph node. The researchers grew T cells (that target a specific protein, or antigen, on the tumor cells) in the lab until they had a population they believed was large enough to destroy the cancer.
They infused five billion of the cloned cells into the patient. Two months later, PET (positron emission tomography) and CT (computed tomography) scans did not reveal any tumors—and the patient has remained disease-free for two years, Yee says. “This is the first example that I can think of where someone actually grew CD4+ T cells outside the body and gave [them] back and got results,” says Willem Overwijk, an immunologist at the University of Texas M.D. Anderson Cancer Center in Houston, who was not involved in this study.