RNA Fragments May Yield Rapid, Accurate Cancer Diagnosis

Tumor cells shed microvesicles containing proteins and RNA fragments, called exosomes, into cerebral spinal fluid, blood, and urine. Within these exosomes is genetic information that can be analyzed to determine the cancer’s molecular composition and state of progression.Researchers at Massachusetts General Hospital discovered that exosomes preserve the genetic information of their parent cells exosomes have not seen widespread clinical testing as a means of cancer diagnosis until now.We have never really been able to detect the genetic components of a tumor by blood or spinal fluid,” says Harvard University neurologist Fred Hochberg. 

Exosome diagnostic tests could potentially detect and monitor the progression of a wide variety of cancers. When treating other forms of cancer, surgeons are able to biopsy tumors to diagnose and monitor the state of the disease. For brain cancers like glioma, however, multiple biopsies can be life threatening.Magnetic Resonance Imaging (MRI) is a useful tool, tumors only show up on imaging scans once they are at least one millimeter in diameter and comprise about 100,000 tumor cells.By that time, it may be too late for an early intervention. On the flip side, MRIs can also yield false positives. Exosomes may be a reliable method of screening for prostate cancer as well. A PSA test is currently the most common, noninvasive means to screen for prostate cancer in the U.S. PSA testing measures for elevated levels of prostate-specific antigen, a protein produced by the prostate gland that is used to liquefy semen in men.The higher a man’s PSA level, the more likely it is that he has prostate cancer, says James McKiernan, director of urologic oncology at Columbia University Medical Center. There are additional reasons, however, for high PSA levels-and some men with prostate cancer do not always have elevated PSA, he added.“Exosomes could be very much [more] cancer specific. PSA might give you one specific biomarker for cancer identification, but exosomes can give you an entire disease specific profile so you would know whether or not it is a form of prostate cancer that necessitates treatment.”Researchers at Exosome have developed a diagnostic kit for prostate cancer with a diagnostic accuracy of around 75 percent-a rate comparable with that of actually taking a tissue biopsy, says Wayne Comper, a renal physiologist and chief science officer at Exosome. He says the first diagnostic kit could be available commercially by the end of 2013.