By Stephanie Murg, Managing Director, G2 Intelligence
Tiny particles known as exosomes may be a powerful cancer screening and diagnostic tool—the trick is detecting and isolating those that are derived from cancer cells. Researchers at the University of Texas MD Anderson Cancer Center have done just that, focusing on a protein that is specifically enriched on cancer-cell-derived exosomes and using it to distinguish healthy subjects and patients with a benign pancreatic disease from patients with early- and late-stage pancreatic cancer. The study was published in Nature on June 24.
The researchers used mass spectrometry analyses to identify glypican-1 (GPC1), the cell surface proteoglycan associated with exosomes derived from cancer cells. GPC1-enriched circulating exosomes (GPC1+ crExos) were found in 250 patients with pancreatic cancer with absolute specificity and sensitivity, according to Raghu Kalluri, M.D., Ph.D., chair of cancer biology at MD Anderson and the study’s senior author. Levels of GPC1+ crExos were significantly lower in patients following surgical removal of the tumor.
In addition to healthy donors, patients with a benign pancreatic disease, and those with pancreatic cancer, the study examined crExos from breast cancer patients. Elevated GPC1+ crExos were seen in both cancers.
Cancer exosomes offer several advantages over commonly used cancer biomarkers. “GPC1+ crExos can be detected and isolated in blood samples that were stored in freezers almost 30 years ago, unlike circulating tumor cells that require large amounts of fresh blood,” said Kalluri. “DNA, RNA, and proteins can be isolated from cancer exosomes isolated from stored specimen for further genetic and biological analyses.”
GPC1+ crExos also show promise as a screening tool, exhibiting greater reliability than the commonly used CA 19-9 biomarker. In mouse models, GPC1+ crExos detected the possibility of pancreatic cancer at a time when the mice showed no signs of pancreatic disease by MRI.
“Routine screening of the general population for pancreatic cancer using MRIs or CTs would be prohibitively expensive with the likelihood for many false positives,” said David Piwnica-Worms, M.D., Ph.D., chair of cancer systems imaging at MD Anderson. “Our study suggests the potential for GPC1+ crExos as a detection and monitoring tool for pancreatic cancer in combination with imaging, with an emphasis on its application in early detection.”