New Process Eliminates Cancer Cells’ ‘Immortality’
The first test of a possible new approach to treating cancer has caused malignant cells that had been growing for decades in a laboratory dish to lose their “immortality” and die within weeks.
Many hurdles must be overcome to show whether the process can be turned into a treatment for patients. But the experiments, reported in today’s issue of the journal Science, provide what the researchers call “proof of principle.”
The principle was proposed last year when scientists announced that they had discovered how cancer cells escape a normal process believed to cause most cells in the body to grow old and die. Their research suggested that cancer cells would die if they could be deprived of that escape route.
“We’re making progress,” said Calvin B. Harley, leader of the scientific group at Geron Corp., a Menlo Park, Calif., biomedical research firm where the studies were done. “We’re on track.”
Harley cautioned, however, that the particular way in which the cancer cells were deprived of their immortality in the experiments--dosing them with laboratory-made genes--is not likely to become useful therapy in the near future.
Instead, he said, Geron and Memorial-Sloan Kettering Cancer Center in New York have received a grant from the National Cancer Institute to develop a drug that accomplishes the same goal.
“We have candidates [drugs] that we are testing, but they are not ready for trial in human beings,” Harley said.
Whether a drug to block the anti-aging mechanism of cancer cells could be effective and safe is unknown.
At the center of all the research is a natural phenomenon that occurs every time cells prepare to divide--which most cells in the human body do many times during a person’s life.
When the cell duplicates its chromosomes so that each of the two daughter cells can have one complete set, parts of the tips of DNA strands are lost.
When the last of the protective sequences of DNA at the tips is gone, subsequent cycles of cell division fail to duplicate some genes. The daughter cells become badly deranged and may die.
One major exception, Harley has found, is cancer cells. Before they have lost the last of their telomeres--the protective DNA at the chromosome tips--they begin to reproduce it. This way, cancer cells can go on dividing endlessly--making new tumors and spreading--without suffering the aging process that dooms normal cells.
Harley and colleagues did their new experiments on a widely used strain of cancer cells, called HeLa, that have been dividing repeatedly in laboratory dishes around the world for decades. HeLa cells are descendants of cervical cancer tissue removed from a Baltimore woman who died in the 1950s.
