Gene sequencing project identifies abnormal gene that launches rare childhood leukemia

November 12, 2012, St. Jude Children's Research Hospital

Research led by the St. Jude Children's Research Hospital – Washington University Pediatric Cancer Genome Project has identified a fusion gene responsible for almost 30 percent of a rare subtype of childhood leukemia with an extremely poor prognosis.

The finding offers the first evidence of a mistake that gives rise to a significant percentage of acute megakaryoblastic leukemia (AMKL) cases in children. AMKL accounts for about 10 percent of pediatric (AML). The discovery paves the way for desperately needed treatment advances.

Investigators traced the genetic misstep to the rearrangement of chromosome 16, which brings together pieces of two genes and sets the stage for production of an . The fusion protein features the front end of CBFA2T3, a , and the back of GLIS2, a protein that is normally produced only in the kidney. Work that appears in the November 13 edition of the journal Cell reports that in a variety of laboratory models the CBFA2T3-GLIS2 protein switched on genes that drive immature blood cells to keep dividing long after normal cells had died. This alteration directly contributes to leukemia.

AMKL patients with the were also found to be at high risk of failing therapy. Researchers checked long-term survival of 40 AMKL patients treated at multiple medical centers around the world and found about 28 percent of patients with the fusion gene became long-term survivors, compared to 42 percent for patients without CBFA2T3-GLIS2. Overall long-term survival for pediatric in the U.S. is now 71 percent.

"The discovery of the CBFA2T3-GLIS2 fusion gene in a subset of patients with AMKL paves the way for improved diagnostic testing, better to help guide treatment and more effective therapeutic interventions for this aggressive ," said James Downing, M.D., St. Jude scientific director and the paper's corresponding author. The first author is Tanja Gruber, M.D., Ph.D., an assistant member in the St. Jude Department of Oncology.

Co-author Richard Wilson, Ph.D., director of The Genome Institute at Washington University School of Medicine in St. Louis, noted: "We identified this unusual gene fusion by comparing the genome of children's healthy cells with the genome of their . This type of in-depth exploration and analysis is crucial to finding unexpected structural rearrangements in the DNA that can lead to cancer. With this discovery, we now can search for more effective treatment options that target this precise defect."

The study is part of the Genome Project, a three-year collaboration between St. Jude and Washington University to sequence the complete normal and cancer genomes of 600 children and adolescents with some of the most aggressive and least understood cancers. The human genome is the instruction book for assembling and sustaining a person. The instructions are packaged in the DNA molecule. Sequencing the genome involves determining the exact order of the four chemical bases that make up DNA. Human DNA is organized into 46 chromosomes.

"We focused on AMKL because no one had any idea of what caused this leukemia in most patients," Gruber said. The study excluded AMKL patients who were infants or children with Down syndrome because earlier research had linked their disease to other chromosomal rearrangements.

When researchers in this study sequenced just the genes that were switched on in the AMKL cells of 14 young patients, the scientists discovered half carried the CBFA2T3-GLIS2 fusion. Additional fusion genes were identified in five of the other patients. Each of those fusion genes occurred in a single patient. The genes involved included HOXA9 and MN1, both previously linked to leukemia, and GATA2 and FLII, which play roles in normal development of the megakaryocytic blood cells that are targeted in AMKL. Megakaryocytes produce the platelets that help blood clot.

Additional sequencing of DNA from adult and pediatric AMKL patients, including whole genome sequencing of the normal and cancer cells of four young AMKL patients, found the CBFA2T3-GLIS2 protein was unique to pediatric AMKL. Of the 48 pediatric AMKL patients screened in this study, 13 carried the fusion gene. None of 28 adult AMKL screened had the gene.

"Whole genome sequencing has allowed us to detect alterations in cancer cells that were previously unknown. Many of these changes contribute directly to the development of cancer," Gruber said. "Such sequencing also provides the deeper understanding of the disease that is critical for developing more effective, less-toxic targeted therapies."

GLIS2 is a transcription factor, meaning it attaches to DNA and turns genes on or off. GLIS2 is normally switched off in blood cells and has not been previously linked to cancer.

Working in several laboratory models, researchers showed that GLIS2, either alone or in the fusion gene, increased the activity of other genes in pathways that control cell functions disrupted in cancer. The genes include BMP2 and BMP4, which are now the focus of additional research. The genes are in a pathway that is active early in the developing blood system. This study implicated the genes in AMKL.

Explore further: Unraveling why children with Down syndrome have increased leukemia risk

Related Stories

Unraveling why children with Down syndrome have increased leukemia risk

February 22, 2012
Children with Down syndrome (DS) have an increased risk of developing leukemia, in particular acute megakaryoblastic leukemia (AMKL) and acute lymphoblastic leukemia (ALL). Through their studies in a mouse model of DS, a ...

Cancer sequencing project identifies potential approaches to combat aggressive leukemia

January 11, 2012
Researchers have discovered that a subtype of leukemia characterized by a poor prognosis is fueled by mutations in pathways distinctly different from a seemingly similar leukemia associated with a much better outcome. The ...

Existing drugs offer new treatment options for high-risk childhood leukemia subtype

August 13, 2012
Scientists have identified new genetic alterations underlying a high-risk subtype of the most common childhood cancer that could be effectively targeted with existing leukemia therapies.

Gene identified as a new target for treatment of aggressive childhood eye tumor

January 11, 2012
New findings from the St. Jude Children's Research Hospital – Washington University Pediatric Cancer Genome Project (PCGP) have helped identify the mechanism that makes the childhood eye tumor retinoblastoma so aggressive. ...

Recommended for you

T-cells engineered to outsmart tumors induce clinical responses in relapsed Hodgkin lymphoma

January 16, 2018
WASHINGTON-(Jan. 16, 2018)-Tumors have come up with ingenious strategies that enable them to evade detection and destruction by the immune system. So, a research team that includes Children's National Health System clinician-researchers ...

Researchers identify new treatment target for melanoma

January 16, 2018
Researchers in the Perelman School of Medicine at the University of Pennsylvania have identified a new therapeutic target for the treatment of melanoma. For decades, research has associated female sex and a history of previous ...

More evidence of link between severe gum disease and cancer risk

January 16, 2018
Data collected during a long-term health study provides additional evidence for a link between increased risk of cancer in individuals with advanced gum disease, according to a new collaborative study led by epidemiologists ...

Researchers develop a remote-controlled cancer immunotherapy system

January 15, 2018
A team of researchers has developed an ultrasound-based system that can non-invasively and remotely control genetic processes in live immune T cells so that they recognize and kill cancer cells.

Dietary fat, changes in fat metabolism may promote prostate cancer metastasis

January 15, 2018
Prostate tumors tend to be what scientists call "indolent" - so slow-growing and self-contained that many affected men die with prostate cancer, not of it. But for the percentage of men whose prostate tumors metastasize, ...

Pancreatic tumors may require a one-two-three punch

January 15, 2018
One of the many difficult things about pancreatic cancer is that tumors are resistant to most treatments because of their unique density and cell composition. However, in a new Wilmot Cancer Institute study, scientists discovered ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.