Small rings of DNA known as double minute chromosomes may represent one such distinguishing feature.
Thus, double minute chromosomes seem to increase a tumor cell's chances of surviving and proliferating.
"I think double minute chromosomes have escaped attention because people haven't realized how interesting they are as molecular entities and unique targets for therapy," asserts Geoffrey M.
He and his colleagues have recently found a way to track double minute chromosomes in living cells.
The earliest report Wahl has seen that mentions double minute chromosomes was published in the 1960s.
That year, a research group reported that tumor cells which resist the chemotherapeutic drug methotrexate harbor double minute chromosomes composed of many copies of the gene that encodes dihydrofolate reductase, an enzyme that deactivates the drug (SN: 1/3/87, p.
Although double minute chromosomes probably can form with all sorts of genes, those that do not offer the cell some advantage would disappear in time.
Such a selection process will gradually increase the overall number of double minute chromosomes in a cell population.
What is unusual, and of potential medical interest, says Wahl, is that tumor cells sometimes discard double minute chromosomes and that certain compounds encourage this process.
Evidence that tumor cells could be "cured" of double minute chromosomes first emerged in 1983, when Robert M.
Several other drugs, adds Wahl, have a similar impact on laboratory-grown cells that contain double minute chromosomes.