For the first time, researchers have traced a childhood form of blood cancer (acute lymphoblastic leukemia or ALL) to a specific virus. The virus, cytomegalovirus (CMV), is common in the herpes family. Children born with congenital infection of this virus have a high risk of developing ALL.
Acute lymphoblastic leukemia (ALL) is the most common form of childhood cancer, and involves the overproduction of immature white blood cells in the bone marrow. These cancerous cells invade the blood and other organ systems, causing massive cell death and damage in a short amount of time.
The causes of ALL vary from genetic abnormalities to exposure to DNA damaging agents. However, researchers have also suspected that infections by certain pathogens may also be a risk factor for developing ALL. To this end, researchers at the University of California, Berkeley and collaborators ventured to pinpoint a pathogen.
The team started by studying a group of 127 children with ALL and 38 children with AML - the myeloid version of leukemia. These children all had infections in their bone marrow in addition to the leukemia. A screen of these samples revealed that CMV infections were detected mostly from children with ALL.
The association was validated in a separate study involving blood samples from 268 newborns who developed ALL, and 270 healthy control newborns. They found a striking connection between presence of CMV and ALL diagnosis. Specifically, those who developed ALL were 3.81 times more likely to have also been diagnosed with congenital CMV.
"Our goal in tracking CMV back from the time of diagnosis to the womb was to establish that this infection occurred well before initiation of disease," said Stephen Francis, the study’s lead author.
Upon stratifying the link by ethnicity, the team found that Hispanic people seem to have the highest risk of developing ALL with CMV infection, at 5.9-fold increased risk.
CMV is a highly common virus. It’s estimated that nearly 80 percent of Americans have been infected with CMV. And most of these infections happen in childhood: one in 3 children are infected with CMV by 5 years of age. While the virus doesn’t usually cause illnesses, those with weakened immune systems may develop complications in vital organs. In particular, congenital CMV infections is typically associated with future hearing loss.
"If it's truly that in utero CMV is one of the initiating events in the development of childhood leukemia, then control of the virus has the potential to be a prevention target," Francis said. "That's the real take-home message."
"This is the first step, but if we do end up finding a causal link to the most common childhood cancer, we hope that will light a fire in terms of stopping mother-to-child transmission of CMV," said Francis .
Additional sources: American Society of Hematology