Tumor suppressor mutations alone don't explain deadly cancer

August 3, 2014

Although mutations in a gene dubbed "the guardian of the genome" are widely recognized as being associated with more aggressive forms of cancer, researchers at the University of California, San Diego School of Medicine have found evidence suggesting that the deleterious health effects of the mutated gene may in large part be due to other genetic abnormalities, at least in squamous cell head and neck cancers.

The study, published online August 3 in the journal Nature Genetics, shows that high mortality rates among head and neck patients tend to occur only when mutations in the tumor suppressor gene coincide with missing segments of genetic material on the cancer genome's third chromosome.

The link between the two had not been observed before because the mutations co-occur in about 70 percent of head and neck tumors and because full genetic fingerprints of large numbers of cancer tumors have become available only recently.

"These two genetic malfunctions are not two separate stab wounds to the body," said co-senior author Trey Ideker, PhD, chief of the Division of Genetics. "One exposes the Achilles tendon and the other is a direct blow to it."

To patients with these cancers, the study's results mean that there may be therapeutic value in testing tumors for the two genetic identifiers, known as a TP53 mutation (short for tumor protein 53) and a 3p deletion (short for deletions of genetic information on the short arm "p" of the third chromosome).

TP53 plays a key role in regulating cell growth, detecting and fixing DNA, and directing cell apoptosis (death) if the DNA damage is irreparable. Because of this, the TP53 protein is sometimes called the "guardian of the ."

The study's findings suggest that if both markers are present, treatment should be intensified. If only one mutation is present, treatment might be de-intensified because the TP53 mutation alone is less deadly than previously thought. The latter would have immediate benefits in reducing deaths caused by complications related to medical care.

"We are in the early stages of being able to personalize head and neck cancer treatments based on the tumor's actual biology, the same as what's done with breast cancers," said co-senior author Quyen Nguyen, MD, PhD, associate professor of Otolaryngology-Head and Neck Surgery. "In the past, treatments have been based largely on the size and location of the . Now, we know that some large tumors may respond to less aggressive treatment while some small tumors may need intensified treatment. This will have a huge impact for patients."

The study analyzed the complete genomic signatures of 250 cases of squamous cell head and neck cancer extracted from The Cancer Genome Atlas, a repository of sequenced cancer genomes for more than 20 different types of human cancers maintained by the National Institutes of Cancer. All of the tumors were from patients younger than 85 years of age.

Of these, 179 had both mutations; 50 had one of the two mutations; and 22 had neither mutation. Comparisons with patient outcome data showed that half of patients with both mutations would likely die of cancer within 2 years, while 66 percent of patients with one or neither mutation would be expected to live five years or more. These survival statistics were independent of the patients' clinical cancer stage.

Besides causing cervical cancer, the human papilloma virus (HPV) is implicated in the growing epidemic of head and neck cancers in otherwise healthy adults. It is believed that the virus can co-opt the activity of TP53, affecting cells in much the same way as a TP53 mutation but without causing a mutation. For this reason, the analysis examined HPV-positive and HPV-negative tumors separately.

One of the study's more compelling discoveries is that among HPV-positive tumors, the most aggressive cancer cases were also highly linked to the presence of 3p deletions.

"Our findings raise fundamental questions about the role of TP53 in cancer and suggest that some of the deleterious health effects of TP53 mutations might actually be due to something else going on in the third chromosome," said lead author Andrew Gross, a graduate student in the Bioinformatics and Systems Biology Program.

Explore further: Newly identified brain cancer mutation will aid drug development

More information: Multi-tiered genomic analysis of head and neck cancer ties TP53 mutation to 3p loss, Nature Genetics, dx.doi.org/10.1038/ng.3051

Related Stories

Newly identified brain cancer mutation will aid drug development

June 1, 2014
A collaborative effort between Duke Medicine researchers and neurosurgeons and scientists in China has produced new genetic insights into a rare and deadly form of childhood and young adult brain cancer called brainstem glioma.

Recurrent head and neck tumors have gene mutations that could be vulnerable to cancer drug

April 4, 2014
An examination of the genetic landscape of head and neck cancers indicates that while metastatic and primary tumor cells share similar mutations, recurrent disease is associated with gene alterations that could be exquisitely ...

Researchers home in on way to predict aggressiveness of oral cancer

June 26, 2014
(Medical Xpress)—Studying mouth cancer in mice, researchers have found a way to predict the aggressiveness of similar tumors in people, an early step toward a diagnostic test that could guide treatment, according to researchers ...

Number of cancer stem cells might not predict outcome in HPV-related oral cancers

January 22, 2014
(Medical Xpress)—New research from The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute (OSUCCC – James) suggests that it may be the quality ...

Tumor suppressor gene TP53 mutated in 90 percent of most common childhood bone tumor

April 3, 2014
The St. Jude Children's Research Hospital—Washington 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 ...

Same cancer, different time zone

July 30, 2014
Just as no two people possess the same genetic makeup, a recent study has shown that no two single tumor cells in breast cancer patients have an identical genome.

Recommended for you

Scientists identify new way cells turn off genes

July 19, 2017
Cells have more than one trick up their sleeve for controlling certain genes that regulate fetal growth and development.

South Asian genomes could be boon for disease research, scientists say

July 18, 2017
The Indian subcontinent's massive population is nearing 1.5 billion according to recent accounts. But that population is far from monolithic; it's made up of nearly 5,000 well-defined sub-groups, making the region one of ...

Mutant yeast reveals details of the aberrant genomic machinery of children's high-grade gliomas

July 18, 2017
St. Jude Children's Research Hospital biologists have used engineered yeast cells to discover how a mutation that is frequently found in pediatric brain tumor high-grade glioma triggers a cascade of genomic malfunctions.

Late-breaking mutations may play an important role in autism

July 17, 2017
A study of nearly 6,000 families, combining three genetic sequencing technologies, finds that mutations that occur after conception play an important role in autism. A team led by investigators at Boston Children's Hospital ...

Newly discovered gene variants link innate immunity and Alzheimer's disease

July 17, 2017
Three new gene variants, found in a genome wide association study of Alzheimer's disease (AD), point to the brain's immune cells in the onset of the disorder. These genes encode three proteins that are found in microglia, ...

Newly identified genetic marker may help detect high-risk flu patients

July 17, 2017
Researchers have discovered an inherited genetic variation that may help identify patients at elevated risk for severe, potentially fatal influenza infections. The scientists have also linked the gene variant to a mechanism ...

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.