Illustration of immune cells. A new cancer-fighting technique has seen three kilos of tumour disappear from a cancer patient in the U.S.
Credit: iStockPhoto
WASHINGTON: An advanced form of leukemia has been wiped out in three U.S. cancer patients by a new therapy that turns immune cells into tumour killers.
The breakthrough stunned scientists and although the gene transfer therapy technique is still in development, it could offer hope one day to people who suffer from ovarian, lung, breast and skin cancers.
"We saw amazing results," said Michael Kalos from the University of Pennsylvania, lead author of the study that appeared in Science Translational Medicine and was published simultaneously in the New England Journal of Medicine.
"These were nasty tumours that were late-stage, a lot of mutations that had bad prognosis," he said. "We saw massive reduction in tumour burden. One patient had over three kilograms of tumour and it all disappeared."
Worked better than expected
Two of the three men in the study with chronic lymphocytic leukemia (CLL) have remained cancer-free for almost a year, while the third has seen a slight recurrence of disease.
"Within three weeks, the tumours had been blown away, in a way that was much more violent than we ever expected," said senior author Carl June, also from the University of Pennsylvania. "It worked much better than we thought it would."
Scientists removed a sample of the patients' T-cells and genetically modified them to attack all cells that express a certain kind of protein, CD19, which includes tumour cells.
They altered them using a lentivirus vector that encodes an antibody-like protein known as a chimeric antigen receptor and expressed. The protein is expressed on the surface of T-cells and designed to bind to CD19.
T-cells as serial killers
The scientists also engineered the T-cells to start triggering other T-cells to multiply as soon as they attached to a cancer cell, bringing on a faster death for the tumour but avoiding the side-effects of cancer drugs.
"We saw at least a 1,000-fold increase in the number of modified T-cells in each of the patients. Drugs don't do that," said June, describing the infused T-cells as "serial killers".
"On average, each infused T-cell led to the killing of thousands of tumour cells."
In one case, a 64-year-old man had blood and marrow "replete with tumour cells". He saw little change for the first two weeks after treatment, but then started experiencing nausea, chills and fever. Tests showed he was undergoing a huge rise in T-cell count, and a condition known as tumour lysis syndrome that can arise when cancer cells are dying off. By day 28, his blood showed no evidence of leukemia.
A 65-year-old patient saw similar results, with no trace of leukemia after a year, but a 77-year-old patient saw a slight recurrence of cancer after he was treated with steroids for the symptoms of tumour lysis syndrome. However, his tumour load remains far below what it was before the treatment.
