They were once seen as lowly cellular garbage trucks. But now, microscopic substances found in the blood called exosomes may help us understand how cancer cripples the immune system and goes on its destructive rampage throughout the body.
UCI Health scientists, along with researchers around the country, are studying the role these bubble-like sacs play in the development of cancer with the aim of devising better treatments and diagnostic tools to catch tumors at their earliest and most treatable stages.
Nearly all cells, including cancer cells, release exosomes into the blood. Early studies of these tiny structures suggested they served cellular housekeeping functions, such as clearing out unneeded proteins and other cellular debris when cells turned over and divided.
But scientists now know that these sacs carry with them bits of proteins, DNA and RNA from their originating cells. When they enter the bloodstream, they travel to distant locations in the body and spread their cargo at these remote sites.
Even more recent research indicates exosomes may dampen immune function, creating an environment that supports cancer and helps it spread.
"Over the past several years, we've come to recognize that exosomes are not just benign bags of cellular garbage," says oncologist Dr. Edward Nelson, chief of the Division of Hematology/Oncology at the UCI School of Medicine.
Patients undergoing treatment were tracked for six months to see if there was a correlation between the level of exosomes in the blood and whether the treatment was working, or if exosome concentrations might be an early indication that the tumor was not responding to treatment.
"If we know that a spike in exosomes means that the tumor is starting to grow, it will help us monitor treatment more closely," says Nelson, who is working with Aethlon Medical Inc., a San Diego-based biotech company, and expects to have study results before the end of the year.
This research may also shed light on how exosomes released from cancer cells hamper the immune system's ability to limit the growth of tumors.
The ultimate aim of these studies is to uncover new strategies for targeting cancer.