He looked at human cells from breast cancers, colon cancers and melanomas and saw the same phenomenon. But blood cancers and glioblastomas, the deadly brain cancers, did not form the cell-in-cell structures.
Perhaps, Dr. Carmi reasoned, it might be possible to prevent cancer cells from taking refuge. He decided to examine the genes involved in this defense mechanism. Blocking those genes, he discovered, also blocked the ability of T cells to attack the tumors.
“I realized this is the limit of what the immune system can do,” Dr. Carmi said. “Our immune systems cannot win.”
Others, while fascinated by the discovery, say many questions remain.
“It’s definitely an interesting paper with some strong, compelling observations,” said Dr. Michel Sadelain, an immunologist at Memorial Sloan Kettering Cancer Center, where he heads the center’s gene transfer and gene expression laboratory. But, he asked, how relevant is the finding in disabling immunotherapies in the real world?
Dr. Marcela Maus, the director of the cellular immunotherapy program at the Mass General Cancer Center, said the discovery showed what might be a new cancer cell defense mechanism.
“We have seen that tumors can hide from the immune system, including a kind of ‘impersonating’ immune cells, but I don’t think we’ve ever seen that tumor cells hide inside each other.” But, she added, “I do think it needs to be replicated to gain full traction.”
Dr. Jedd Wolchok, the director of the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine, had the same reaction.
