Master switches found for adult blood stem cells

Scientists have found a set of “master switches” that keep adult blood-forming stem cells in their primitive state. Unlocking the switches’ code may one day enable scientists to grow new blood cells for transplant into patients with cancer and other bone marrow disorders.

The scientists located the control switches not at the gene level, but farther down the protein production line in more recently discovered forms of ribonucleic acid, or RNA. MicroRNA molecules, once thought to be cellular junk, are now known to switch off activity of the larger RNA strands which allow assembly of the proteins that let cells grow and function.

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Researchers map out networks that determine cell fate

A two-step process appears to regulate cell fate decisions for many types of developing cells, according to researchers from the University of Chicago.

This finding sheds light on a puzzling behavior. For some differentiating stem cells, the first step leads not to a final decision but to a new choice. In response to the initial chemical signal, these cells take on the genetic signatures of two different cell types. It often requires a second signal for them to commit to a single cellular identity.

In the Aug. 25 2006 issue of Cell, the researchers, working with hematopoietic stem cells, which give rise to the many types of blood cells, show how “pioneer transcription factors” trigger the first step, pushing these stem cells towards this mixed lineage, midway between two related cell types — in this case between a macrophage and a neutrophil.

Targeting leukemic stem cells by Bcl-2 inhibition

Researchers at The University of Texas M. D. Anderson Cancer Center have found, in laboratory studies, that the experimental drug ABT-737 which has shown promise in some cancers, can destroy acute myeloid leukemia (AML) blast, progenitor and even stem cells that are often resistant to standard chemotherapy treatment.

The drug was powerful in its own right, the researchers say, but they found that some AML cells were themselves resistant to ABT-737, so they added another drug that knocked out this secondary resistance. Together, these agents may provide a powerful therapy against AML, and could form the basis of a new way to treat the cancer, say the scientists, whose study was published in the November 14 issue of the journal, Cancer Cell.

Scientists Discover Key to Growing New Stem Cells

Scientists at Duke University Medical Center have demonstrated they can grow human stem cells in the laboratory by blocking an enzyme that naturally triggers stem cells to mature and differentiate into specialized cells.
The discovery may enable scientists to rapidly grow stem cells and transplant them into patients with blood disorders, immune defects and select genetic diseases, said the Duke researchers.

Drug that battles resistance to leukemia pill Gleevec ‘extremely effective’ against cancer

An experimental therapy that battles drug resistance in Chronic Myeloid Leukemia (CML) has proved "extremely effective" in fighting cancer, giving patients for whom all conventional therapies have failed another option, researchers at UCLA's Jonsson Cancer Center reported.

The Bristol-Myers Squibb therapy, Sprycel (dasatinib), treats CML that has mutated and becomes resistant to the leukemia pill Gleevec, said Dr. Charles Sawyers, a professor of hematology/oncology, a Jonsson Cancer Center researcher and lead author of the study, published in the June 15, 2006 issue of the peer-reviewed New England Journal of Medicine.

Sickle cell disease corrected in human models using stem cell-based gene therapy

In a study to be published in the January 2006 issue of Nature Biotechnology, researchers led by a team of scientists at Memorial Sloan-Kettering Cancer Center have devised a novel strategy that uses stem cell-based gene therapy and RNA interference to genetically reverse sickle cell disease (SCD) in human cells. This research is the first to demonstrate a way to genetically correct this debilitating blood disease using RNA interference technology.