Likewise, changes to the physiological environment of cells, with drugs or toxins, for example, can alter their metabolic output. To track these processes, scientists need ways to mark genes and their protein products. This month's release of Cold Spring Harbor Protocols (www.cshprotocols) features freely available methods for marking molecules to identify gene alterations and metabolic shifts.

The first method (cshprotocols/cgi/content/full/2007/10/pdb.prot4743) describes how to grow cells from bacteria, yeast, insects, or mammals in media containing the stable isotope nitrogen-15. As the cells grow, they produce nascent proteins that include nitrogen-15, a marker that distinguishes newly formed metabolic products from pre-existing ones. The differences between these cells and "normal" cells (grown in media without nitrogen-15) can then be quantified using a technique called mass spectrometry.

To identify structural features and abnormalities in chromosomes, scientists need to tag DNA probes with visual markers. The second freely available method (cshprotocols/cgi/content/full/2007/10/pdb.prot4730) describes how to label DNA probes with fluorescent markers of six different colors, which span the visible spectrum. These labeled DNA probes can be used simultaneously in FISH (fluorescent in situ hybridization) experiments, during which the probes bind to specific chromosomal regions of interest. The colorful chromosomes can then be viewed under a microscope.

cshl

"Although this study was not designed to identify mutations that would contribute to disease progression, our results suggest that these would also be found. These considerations highlight the importance of gaining further understanding of the control of DNA replication and repair in the leukemic stem cells from patients with chronic phase [chronic myeloid leukemia] in future efforts to devise therapies with curative potential," the authors write.

In an accompanying editorial, Margret Rodrigues, Ph.D., and Martin Sattler, Ph.D., of the Dana Farber Cancer Institute in Boston, discuss the possible causes of genetic instability in the BCR-ABL gene and future approaches to developing successful therapies for chronic myeloid leukemia. "A future challenge will be to devise approaches that overcome drug resistance within these [chronic myeloid leukemia stem] cells without selecting for additional drug-resistant populations," the authors write.

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