Microvesicles – tiny membrane-covered sacs – released from glioblastoma cells contain molecules that may provide data that can guide treatment of the deadly brain tumor. Researchers have found tumor-associated RNA and proteins in membrane microvesicles called exosomes in blood samples from glioblastoma patients. Detailed analysis of exosome contents identified factors that could facilitate a tumor’s growth through delivery of genetic information or proteins, or signify its vulnerability to particular medications.