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Study Investigates Genetics of Pediatric Medulloblastomas

Appear to have fewer gene alterations than adult solid tumors

MONDAY, Dec. 20 (HealthDay News) -- Childhood medulloblastomas may have a smaller number of gene alterations than the number seen in adult solid tumors, according to research published online Dec. 16 in Science.

D. Williams Parsons, M.D., Ph.D., of the Johns Hopkins Kimmel Cancer Center in Baltimore, and colleagues analyzed data from pediatric medulloblastoma samples.

After sequencing protein-coding genes and microRNA genes from a set of 22 pediatric medulloblastomas, the researchers found that each tumor had an average of 11 gene alterations, which is five to 10 times fewer than the number seen in adult solid tumors that have been sequenced. The researchers found alterations in the Hedgehog and Wnt pathways. In addition, 16 percent of patients had inactivating mutations of the histone-lysine N-methyltransferase genes MLL2 or MLL3.

"The identification of MLL2 and MLL3 as frequently-inactivated medulloblastoma genes supports the concept that medulloblastoma is fundamentally characterized by dysregulation of core developmental pathways. Although alterations of classic cancer genes (e.g., TP53, MYC, and PTEN) were also identified in these childhood tumors, our sequence analysis demonstrated that mutations of genes involved in normal developmental processes, such as MLL family genes and Hedgehog and Wnt pathway genes, were much more frequent," the authors write.

Several authors disclosed financial relationships with Inostics and Personal Genome Diagnostics, while some authors may receive royalties related to research described in this study.

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