Gene mutations linked to lethal childhood brain tumors

London, Jan 30 (ANI): Gene mutations may be responsible for aggressive pediatric brain tumors, a new study has suggested.

Researchers studying a rare, lethal childhood tumor of the brainstem have discovered that nearly 80 percent of the tumors have mutations in genes not previously tied to cancerarly evidence also suggests that the alterations play a unique role in other aggressive pediatric brain tumors as well.

The findings from the St. Jude Children's Research Hospital - Washington University Pediatric Cancer Genome Project (PCGP) offer important insight into a poorly understood tumor that kills more than 90 percent of patients within two years.

The tumor, diffuse intrinsic pontine glioma (DIPG), is found almost exclusively in children and accounts for 10 to 15 percent of pediatric tumors of the brain and central nervous system.

"We are hopeful that identifying these mutations will lead us to new selective therapeutic targets, which are particularly important since this tumor cannot be treated surgically and still lacks effective therapies," said Suzanne Baker, Ph.D., co-leader of the St. Jude Neurobiology and Brain Tumor Program and a member of the St. Jude Department of Developmental Neurobiology.

DIPG is an extremely invasive tumor that occurs in the brainstem, which is at the base of the skull and controls such vital functions as breathing and heart rate. It cannot be cured by surgery and is accurately diagnosed by non-invasive imaging.

In this study, investigators found 78 percent of the DIPG tumors had alterations in one of two genes that carry instructions for making proteins that play similar roles in packaging DNA inside cells.

Both belong to the histone H3 family of proteins. DNA must be wrapped around histones so that it is compact enough to fit into the nucleus. The packaging of DNA by histones influences which genes are switched on or off, as well as the repair of mutations in DNA and the stability of DNA. Disruption of any of these processes can contribute to cancer.

Researchers said that the mutations seem unique to aggressive childhood brain tumors.

For this study, researchers sequenced the complete normal and cancer genomes of seven patients with DIPG.

When researchers sequenced all 16 of the related genes that make closely related variants of histone H3 proteins in an additional 43 DIPGs, they found many of the tumors contained the same mistakes in only two of these genes.

Of the 50 DIPG tumors included in this study, 60 percent had a single alteration in the makeup of the H3F3A gene. When the mutated gene was translated into a protein, the point mutation led to the substitution of methionine for lysine as the 27th amino acid in this variant of histone H3 protein.

Another 18 percent of the DIPG patients carried the same mistake in a different gene, HIST1H3B.

Researchers are now working to understand how mutations in H3F3A and HIST1H3B impact cell function and contribute to cancer.

The study has been published in the online edition of the scientific journal Nature Genetics. (ANI)

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