They also found that a non-mutant cell lacking a telomere occasionally escapes suicide and divides. Then, its progeny accumulate defects, including the wrong number of chromosomes or chromosomes that have exchanged pieces with each other. Those defects are hallmarks of cancer cells.
One possible reason a cell avoids suicide even after telomere loss and other damage is that chromosomes in the cell's offspring regain telomeres.
"All cancer cells have figured out how to add new telomeres, which allows them to survive and divide indefinitely," says Titen. "By interfering with this process, it might be possible to provide a route therapeutically to treat cancer."
A telomere is made of short sequences of DNA repeated hundreds of times. Proteins bind to the DNA, forming a cap or telomere that protects the end of the chromosome.
In humans, cells in certain tissues, such as the skin, continue to divide over a lifetime. Each time a cell divides, the telomeres become shorter until, in rare cases, the rest of the chromosome is no longer protected. It has been proposed that this can trigger cancer, but previous studies have been done only in yeast or cultured animal cells that are grown in a dish. The new Utah study shows in flies that telomere loss can cause cancer-like changes in a cell.
When Cell Suicide is Blocked, Cells Start on the Road to Cancer
Fruit flies often are used for chromosomal studies because they share 60 percent of their genes with humans, and it is unethical to cause genetic abnormalities in humans. Also, the process by which fly cells grow and divide are comparable with human cells.
To trigger telomere loss, the researchers inserted into the flies a gene from common baker's yeast. The gene makes an enzyme that breaks and rejoins DNA. When they tur
|Contact: Lee Siegel|
University of Utah