All too often, cancer that seems to have been wiped out by treatment comes back. Some scientists have blamed so-called cancer stem cells, a subset of cancer cells that might be able to remain dormant, evading chemotherapy or radiation treatments, only to form new tumors months or years later. The idea has been controversial, but three papers published today report evidence that in certain brain, skin, and intestinal tumors, cancer stem cells are the source of tumor growth.
The cancer stem cell model differs from the traditional idea that tumor growth is equal opportunity—that is, any and all cancerous cells can divide and cause the tumor to grow and spread. The stem cell model says that tumor growth is more hierarchical, mainly driven by a subset of cells that can make new copies of themselves and give rise to the other cell types the tumor contains. Some of the first evidence for cancer stem cells came from studies of leukemia in the 1990s, which showed that only a small subset of the cancerous blood cells could propagate the disease in mice. But it has been harder to test whether cancer stem cells fuel the growth of tumors in other tissues.
Hay fever, dog, peanut and other allergies may protect sufferers from certain types of brain tumors, a new study suggests.
In surveys of hospital patients, individuals with glioma — a common form of brain and spinal cancer — were less likely than cancer-free individuals to report having allergies, University of Illinois at Chicago researchers report online Feb. 7 in Cancer Epidemiology, Biomarkers & Prevention.
Several teams had previously explored the link between allergies and glioma, says UIC epidemiologist Bridget McCarthy, who led the study. Her team set out to confirm these results, cobbling together a wide list of variables. The researchers quizzed about 1,000 hospital patients with or without cancer about their allergy histories. Of the 344 patients with high-grade glioma, about 35 percent reported having been diagnosed with one or more allergies in their lifetimes, compared with about 46 percent of the 612 cancer-free respondents. About 10 percent of high-grade tumor patients had three or more allergy diagnoses, as opposed to 22 percent of the controls. “The more allergies you have, the more protected you were,” says McCarthy, an oncologist at UIC.
Glioma isn’t the first cancer to be negatively correlated with common allergies, says Michael Scheurer, an oncologist at Baylor Medical College in Houston. Allergy-prone people may fight off colorectal and pancreatic cancer, and even childhood leukemia, better than sniffle-free people, according to some studies. At the other end of the spectrum, allergies that cause asthma may spur lung tumors.