From MIT News: researchers "have had some striking successes treating melanoma with T-cell therapy, but so far it has been much less effective against other cancers. ... [An] obstacle is keeping the T cells alive once they are returned to the patient. Most T cells have a short lifespan, so after weeks of manipulation in the lab, they may die soon after they enter the patient. Furthermore, the tumor itself creates an environment very hostile to T cells. ... Giving patients large doses of growth factors called cytokines [helps], but those can have severe side effects, including heart and lung failure, when given in large doses. ... [researchers] recently developed a new approach that could avoid those side effects. They engineered T cells with tiny pouches that can carry cytokines, which are gradually released from the pouches, enhancing the longevity of the T cells that carry them. ... [they] used their modified T cells to treat mice with lung and bone marrow tumors. Within 16 days, all of the tumors in the mice treated with T cells carrying the drugs disappeared. Those mice survived until the end of the 100-day experiment, while mice that received no treatment died within 25 days, and mice that received either T cells alone or T cells with injections of cytokines died within 75 days. They are now working on ways to more easily synthesize the pouches at a large scale, so they can be tested in humans, using materials that would be more likely to get FDA approval."