Genetics

Breast cancer cells spread in an already-armed mob

cluster of tumor cells

New research has revealed that cancer cells travel in mob-like patterns. This is a beneficial discovery because it is known that it is the spread of tumor cells that causes death. Often times, when cancer recurs it is stronger and more deadly than before. It is in part due to the clusters that break off in this way.

Breast cancer cells may break away from the main tumor in clumps, already bearing most of the mutations that will drive cancer recurrence, a study suggests. Shown here is a cluster of circulating tumor cells (red) from a patient with breast cancer.

ON THE ROAD

COLD SPRING HARBOR, N.Y. — When breast cancer spreads, it moves in gangs of ready-to-rumble tumor cells, a small genetic study suggests. Most of the mutations that drive recurrent tumors when they pop up elsewhere in the body were present in the original tumor, geneticist Elaine Mardis reported May 9 at the Biology of Genomes meeting.

For many types of cancer, it is the spread, or metastasis, of tumor cells that kill people. Because cancer that comes back and spreads after initial treatment is often deadlier than the original tumors,…

Autism, ADHD risk not linked to prenatal exposure to antidepressants

pregnant woman
SEEKING TREATMENT Pregnant women coping with depression now may have one less thing to worry about: Prenatal exposure to antidepressants doesn’t raise autism risk, two new studies suggest.

Taking antidepressants during pregnancy does not increase the risk of autism or attention-deficit/hyperactivity disorder, two new large studies suggest. Genetic or environmental influences, rather than prenatal exposure to the drugs, may have a greater influence on whether a child will develop these disorders. The studies are published online April 18 in JAMA.

Clinically, the message is “quite reassuring for practitioners and for mothers needing to make a decision about antidepressant use during pregnancy,” says psychiatrist Simone Vigod, a coauthor of one of the studies. Past research has questioned the safety of expectant moms taking antidepressants (SN: 6/5/10, p. 22).

“A mother’s mood disturbances during pregnancy are a big public health issue — they impact the health of mothers and their children,” says Tim Oberlander, a developmental pediatrician at the University of British Columbia in Vancouver. About one in 10 women develop a major depressive episode during pregnancy. “All treatment options should be explored. Nontreatment is never an option,” says Oberlander, who coauthored a commentary, also published in JAMA.

Untreated depression during pregnancy creates risks for the child, including poor fetal growth, preterm birth and developmental problems. Some women may benefit from psychotherapy alone. A more serious illness may require antidepressants. “Many of us have started to look at longer term child outcomes related to antidepressant exposure because mothers want to know about that in the decision-making process,” says Vigod, of Women’s College Hospital in Toronto.

Previous studies indicated that the use of antidepressants came with its own developmental risks: autism spectrum disorder, ADHD, premature birth and…

Genetic risk of getting second cancer tallied for pediatric survivors

childhood cancer
RISK ROUNDUP Some pediatric cancer survivors carry genetic mutations that increase the risk of a later, second cancer.

WASHINGTON — A second cancer later in life is common for childhood cancer survivors, and scientists now have a sense of the role genes play when this happens. A project that mined the genetic data of a group of survivors finds that 11.5 percent carry mutations that increase the risk of a subsequent cancer.

“We’ve always known that among survivors, a certain population will experience adverse outcomes directly related to therapy,” says epidemiologist and team member Leslie Robison of St. Jude Children’s Research Hospital in Memphis. The project sought “to find out what contribution genetics may play.” The team presented their work at the American Association of Cancer Research meeting April 3.

“This is a nice first step,” says David Malkin, a pediatric oncologist at the University of Toronto. “The results validate the thoughts of those of us who believe there is a genetic risk that increases the risk of second malignancies.”

Five-year survival rates for kids with cancer have grown to more than 80 percent. But “there are long-term consequences for having been diagnosed and treated for cancer as a child,” notes Robison. Some survivors develop a later, second cancer due to the radiation or chemotherapy that treated the first cancer (SN: 3/10/07, p. 157).

The researchers examined 3,007 survivors of pediatric cancer who routinely undergo medical evaluation at St. Jude. About a third had leukemia as children. By age 45, 29 percent of this group had developed new tumors, often in the skin, breast or thyroid.

The team cataloged…

Number of species depends how you count them

Hercules beetles
DRAWING LINES Scientists sometimes have difficulty determining whether organisms, such as these Hercules beetles, are members of different species. Genetic analysis alone may divide populations into species that don’t exist by other biological criteria.

Genetic methods for counting new species may be a little too good at their jobs, a new study suggests.

Computer programs that rely on genetic data alone split populations of organisms into five to 13 times as many species as actually exist, researchers report online January 30 in Proceedings of the National Academy of Sciences. These overestimates may muddy researchers’ views of how species evolve and undermine conservation efforts by claiming protections for species that don’t really exist, say computational evolutionary biologist Jeet Sukumaran and evolutionary biologist L. Lacey Knowles.

The lesson, says Knowles, “is that we shouldn’t use genetic data alone” to draw lines between species.

Scientists have historically used data about organisms’ ecological distribution, appearance and behavior to classify species. But the number of experts in taxonomy is dwindling, and researchers have turned increasingly to genetics to help them draw distinctions. Large genetic datasets and powerful computer programs can quickly sort out groups that have become or are in the process of becoming different species. That’s especially important in analyzing organisms for which scientists don’t have much ecological data, such as insects in remote locations or recently extinct organisms.

Knowles and Sukumaran, both of the University of Michigan in Ann Arbor, examined a commonly used computer analysis method, called multispecies coalescent, which picks out genetic differences among individuals that have arisen recently in evolutionary time. Such differences could indicate that a population of organisms is becoming a separate species. The researchers used a set of known species and tested the program’s ability to correctly predict…