Tracking the molecular pathway to mixed-lineage leukemia

Dec 15, 2008

Infants and adults with the blood cancer mixed-lineage leukemia (MLL) typically have a poor prognosis, and most infants die before their first birthdays. Although there are varying causes of MLL, most cases are caused by a fusion of two genes, the MLL and the AF4 genes.

When the MLL gene is fused to the AF4 gene, a potent cancer-causing oncogene is created. Although researchers have known that the MLL-AF4 protein produced by this genetic fusion causes leukemia, they had not been able to determine precisely how this oncogene disrupted cells' normal protein production.

To pinpoint the oncogene's activities, Matthew Guenther, a postdoctoral researcher in Whitehead Member Richard Young's lab, used a technique called ChIP-seq (chromatin immunoprecipitation with DNA sequencing) to map where the MLL-AF4 protein interacts with a cell's genome. He found that in cancer cells the MLL-AF4 protein binds to at least 169 genes, many of which are overexpressed in leukemia cells and encode hematopoietic stem cell regulators (the genes that initiate blood cell production).

It seems that when the MLL-AF4 protein interacts with these genes, it forces them into a hyperactive state, with disastrous consequences.

"The MLL-AF4 fusion protein is somehow targeted to a set of genes that essentially hijacks the blood stem cell machinery and makes that cell become cancerous, basically a younger-looking cell that is dividing much more than it should," says Guenther.

Looking closer at the MLL-AF4 protein-bound genes, Guenther noticed that these genes display strange patterns of chromatin proteins. In the cell, DNA is wrapped around chromatin proteins for dual purposes: to safely package DNA for cell division and to control gene expression (epigenetics). Changes in chromatin structures can affect normal gene expression, and other studies have linked chromatin misregulation to cancer and to leukemia disease progression. In MLL patients, it seems the MLL-AF4 protein alters the normal chromatin state of the hematopoietic stem cell regulators.

Guenther's findings may take scientists one step closer to a treatment for this deadly disease.

"We think we've figured out a key piece of how this leukemia works," says Young. "If we understand the molecular pathway for how the MLL-AF4 protein interacts with genes, it gives us a set of new target genes that might be used for drug development."

Published: Genes and Development, December 15, 2008.

Source: Whitehead Institute for Biomedical Research

Explore further: Revolutionary handheld DNA diagnostic unit allows lab-quality analysis in the field

add to favorites email to friend print save as pdf

Related Stories

Earthquakes over 5 magnitude shake Iceland volcano

55 minutes ago

Two earthquakes measuring over 5 in magnitude—the biggest yet—have shaken Iceland's Bardarbunga volcano after the country issued an aviation red alert warning that an ash-emitting eruption may be imminent.

Airlines on alert as eruption begins in Iceland

15 hours ago

Iceland's Bardarbunga volcano burst forth with a small eruption Saturday under the ice of Europe's largest glacier, scientists said, prompting the country to close airspace over the area.

Two Galileo satellites lose their way

18 hours ago

Two European Galileo satellites launched as part of a navigation system designed to rival GPS have failed to locate their intended orbit, launch firm Arianespace said Saturday.

Recommended for you

NIH issues finalized policy on genomic data sharing

8 hours ago

The National Institutes of Health has issued a final NIH Genomic Data Sharing (GDS) policy to promote data sharing as a way to speed the translation of data into knowledge, products and procedures that improve health while ...

The genes behind the guardians of the airways

13 hours ago

Dysfunctions in cilia, tiny hair-like structures that protrude from the surface of cells, are responsible for a number of human diseases. However the genes involved in making cilia have remained largely elusive. ...

Cancer leaves a common fingerprint on DNA

Aug 25, 2014

Regardless of their stage or type, cancers appear to share a telltale signature of widespread changes to the so-called epigenome, according to a team of researchers. In a study published online in Genome Me ...

User comments : 0