Tumor suppressor gene TP53 mutated in 90 percent of most common childhood bone tumor
Posted: April 4, 2014 at 6:43 am
PUBLIC RELEASE DATE:
3-Apr-2014
Contact: Carrie Strehlau carrie.strehlau@stjude.org 901-595-2295 St. Jude Children's Research Hospital
(MEMPHIS, Tenn. April 3, 2014) The St. Jude Children's Research HospitalWashington University Pediatric Cancer Genome Project found mutations in the tumor suppressor gene TP53 in 90 percent of osteosarcomas, suggesting the alteration plays a key role early in development of the bone cancer. The research was published today online ahead of print in the journal Cell Reports.
The discovery that TP53 is altered in nearly every osteosarcoma also helps to explain a long-standing paradox in osteosarcoma treatment, which is why at standard doses radiation therapy is largely ineffective against the tumor. The findings follow the first whole genome sequencing of osteosarcoma, which is diagnosed in about 400 children and adolescents annually, making it the most common pediatric bone tumor.
"Osteosarcoma treatment has remained largely unchanged for more than 20 years, and cure rates are stalled at about 70 percent. This study lays a foundation for new therapies and more immediately identifies numerous mutations in TP53 missed by previous studies that did not include whole genome sequencing," said co-corresponding author Michael Dyer, Ph.D., a Howard Hughes Medical Institute investigator and member of the St. Jude Department of Developmental Neurobiology. Jinghui Zhang, Ph.D., member of the St. Jude Department of Computational Biology, is the other corresponding author.
TP53 carries instructions for assembling the p53 protein, which plays a role in DNA repair and cell death. Inactivation of p53 helps tumor cells survive radiation therapy. Previous studies estimated that TP53 was mutated in a quarter to half of osteosarcomas, suggesting that a significant proportion of patients with this tumor should respond to radiation. That was not the case, Dyer said.
"With whole-genome sequencing, we are gaining new insights into the way various mutations in TP53 promote the development of osteosarcomas," said co-author Richard K. Wilson, Ph.D., director of The Genome Institute at Washington University School of Medicine in St. Louis. "This information will be very helpful in designing treatment protocols."
The study involved whole genome sequencing of 34 osteosarcoma tumors from 32 patients. The patients' normal genomes were also sequenced.
The research revealed that 55 percent of TP53 mutations were caused by structural variations. These alterations occur when chromosomes break and are reassembled. Osteosarcoma is just the second cancer with TP53 mutations resulting from chromosomal rearrangements rather than point mutations, which are small changes in the DNA that makes up the gene. "This suggests that the cell that gives rise to osteosarcoma may either be particularly susceptible to chromosomal breaks or better able to tolerate breaks when they occur," Dyer said.
Originally posted here:
Tumor suppressor gene TP53 mutated in 90 percent of most common childhood bone tumor