WASHINGTON, Nov. 6 (Xinhua) -- Long and thin nanomaterials called carbon nanotubes may have the same carcinogenic effect as asbestos, a new study said Monday.
Long carbon nanotubes, a subtype of nanotubes used in the manufacture of incredibly strong and lightweight materials for a number of industrial and consumer products, can induce the formation of mesothelioma, according to the study published in the U.S. journal Current Biology.
"Unlike previously reported short-term studies, this is the first time the effects of long and thin carbon nanotubes, leading to mesothelioma, have been monitored in mice over many months," senior author Marion MacFarlane, a Professor at the Medical Research Council (MRC) Toxicology Unit in Leicester, Britain, said in a statement.
"Importantly, not all nanofibers pose a hazard," she added. "We want our research to inform manufacturers and regulators about safer options when a nanofiber is being selected for the production of nanomaterials for emerging technologies."
In the animal experiments, the investigators placed long carbon nanotubes in the pleura, the area around the lungs where mesothelioma develops in human.
Follow-up observations revealed stages of chronic inflammation, activation of pro-oncogenic signaling pathways, and eventually inactivation and loss of genes that are the gatekeepers of cancer development, MacFarlane said.
The mesothelioma caused by long carbon nanotubes was observed in at least 10 percent of the animals included in the study, which has not yet been replicated in humans.
The investigators stressed that the danger is posed only by types of nanomaterials that are long, thin and biopersistent -- meaning that they are not broken down inside the body.
"These long, thin nanotubes are very similar to asbestos in their structural and physical characteristics," MacFarlane said. "The immune system does a good job of recognizing nanotubes that are shorter, thicker, or tangled up. They can be phagocytized by macrophages and cleared out of the body."
Observations in the mice also showed that chronic inflammation caused by long nanotubes led to inactivation of the same genes observed to be disrupted in people with mesothelioma.
The researchers found that hypermethylation and silencing of the Cdkn2a locus ultimately led to loss of the tumor suppressor proteins p16 and p19.
"Because mesothelioma is diagnosed when it's quite advanced, we don't know much about the early mechanisms by which it forms," said first author Tatyana Chernova, a senior staff scientist at MRC.
"This research could help us find biomarkers for early detection, as well as provide information for developing targeted therapies for this devastating disease."