A HIGHLY experimental treatment has dramatically shrunk deadly skin cancers in several patients, all by knocking out natural immune cells to make way for an army of tumour-attacking cells.
Only 13 people have had the treatment so far and it hasn’t worked for all of them. But it is already attracting attention as a potential approach against infectious diseases such as AIDS as well as cancer.
The treatment takes advantage of a subset of T cells, a major part of our immune system, which can recognise proteins that are rife in tumour cells. These T cells provide a natural protection against cancer. But if a tumour is too aggressive, the body can’t make enough of them to cope.
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In the past scientists have tried multiplying a patient’s own anti-cancer T cells in the lab and then injecting them back in. But the cells dwindled in just a few days.
Steven Rosenberg’s team at the National Cancer Institute in Maryland have now conquered this problem, using hints from mouse experiments. Before putting the T cells back into patients, the team depleted the normal reservoir of immune cells through chemotherapy, making room for the new T cells.
The tumours shrank in 6 of 13 patients with metastatic melanoma, an aggressive form of skin cancer (Science, DOI: 10.1126/science.1076514). “The first patient, treated in September 2000, is still disease-free,” says Rosenberg. The anti-cancer T cells stuck so well that, in two patients, they peaked at more than 90 per cent of their total T-cell count. That’s remarkable, says Rosenberg. They usually only make up about 1 per cent.
Other patients weren’t as lucky – the new T cells didn’t take and their cancers didn’t shrink. Rosenberg is now trying to figure out why. And others developed side effects such as loss of skin pigment or inflammation in the eye. “For tumours like melanoma, where the autoimmune reaction may not be life threatening, that seems like a good trade-off,” says Gregory Plautz of the Cleveland Clinic in Ohio.
