Epigenetic analysis of stomach cancer finds new disease subtypes

October 17, 2012

Researchers at the Duke-NUS Graduate Medical School in Singapore have identified numerous new subtypes of gastric cancer that are triggered by environmental factors.

Reported in the Oct. 17, 2012, issue of the journal Science Translational Medicine, the findings are based on the science of epigenetics, a study of . The insights into the complexities of stomach cancer could lead to better treatment approaches for the second leading cancer killer in the world, behind .

" is a heterogenous disease with individual patients often displaying markedly different responses to the same treatment," said Patrick Tan, M.D., Ph.D at Duke-NUS and lead author of the study. "Improving gastric cancer will require molecular approaches capable of subdividing patients into biologically similar subgroups, and designing subtype-specific therapies for each group."

Like many cancers, is caused by genetic mutations, but also by external factors that affect the way genes work. These factors, called epigenetic alterations, work by methylation, a chemical process in which specific locations along the DNA, called CpG sites, are modified through the addition of a . Methylation silences a gene's behavior without actually altering the DNA sequence.

In their study, Tan and colleagues used 240 primary tumors and cell lines to conduct the first full survey of the landscape in gastric cancer, known as the methylome. Their goal was to identify new molecular subgroups of gastric cancer not caused by primary , particularly those that might be targeted with therapies.

The researchers found that the gastric cancer methylome was widespread, with more than half of the CpG sites analyzed demonstrating altered methylation patterns in cancer. Many of the methylation alterations were associated with significant changes in , suggesting that the methylation alterations may be functionally important in the development of gastic cancer.

The researchers also identified a subgroup of gastric cancers with extremely high levels of methylation. The CIMP subgroup (CpG Island Methylator Phenotype) had been previously proposed, but its clinical significance remained unclear. The Duke-NUS-led team confirmed the CIMP subgroup, correlating it with younger patients who had a poor prognosis. They also demonstrated in laboratory experiments that these tumors may have increased sensitivity to demethylating drugs.

"Our study does provide clarity in unambiguously demonstrating the presence of this subgroup and its features," Tan said. "What's more, we are encouraged that there may be potential utility in testing the sensitivity of CIMP tumors to more potent DNA demethylating agents and possibly other epigenetic drugs."

The study also discovered long-range regions of epigenetic silencing, some targeting a generalized region and others that targeting a single gene. The finding may help identify novel genes where methylation events play a role in tumor growth.

"Our results strongly demonstrate that gastric cancer is not one disease but a conglomerate of multiple diseases, each with a different underlying biology and hallmark features," Tan said. "If gastric cancer is the result of multiple interacting factors, including both environmental factors and host genetic factors, we need better ways to diagnosis and treat it.

"These findings move us forward, and additional work will focus on developing simple diagnostic tests to detect gastric cancer at earlier stages, plus drugs and drug targets that might exhibit high potency against different molecular subtypes of disease," Tan said.

Explore further: Bonanza of genomic sequence data gives researchers valuable new insights into a poorly understood cancer

Related Stories

Bonanza of genomic sequence data gives researchers valuable new insights into a poorly understood cancer

September 12, 2012
Stomach cancer doesn't get the same publicity as lung or breast cancer, but it is a health threat to be taken very seriously. "Gastric cancer is the second leading cause of worldwide cancer mortality, with an annual death ...

Genetic differences distinguish stomach cancers, treatment response

August 1, 2011
Stomach cancer is actually two distinct disease variations based on its genetic makeup, and each responds differently to chemotherapy, according to an international team of scientists led by researchers at Duke-National University ...

Experts identify critical genes mutated in stomach cancer

April 8, 2012
An international team of scientists, led by researchers from the Duke-NUS Graduate Medical School (Duke-NUS) in Singapore and National Cancer Centre of Singapore, has identified hundreds of novel genes that are mutated in ...

Recommended for you

No dye: Cancer patients' gray hair darkened on immune drugs

July 21, 2017
Cancer patients' gray hair unexpectedly turned youthfully dark while taking novel drugs, and it has doctors scratching their heads.

Shooting the achilles heel of nervous system cancers

July 20, 2017
Virtually all cancer treatments used today also damage normal cells, causing the toxic side effects associated with cancer treatment. A cooperative research team led by researchers at Dartmouth's Norris Cotton Cancer Center ...

Molecular changes with age in normal breast tissue are linked to cancer-related changes

July 20, 2017
Several known factors are associated with a higher risk of breast cancer including increasing age, being overweight after menopause, alcohol intake, and family history. However, the underlying biologic mechanisms through ...

Immune-cell numbers predict response to combination immunotherapy in melanoma

July 20, 2017
Whether a melanoma patient will better respond to a single immunotherapy drug or two in combination depends on the abundance of certain white blood cells within their tumors, according to a new study conducted by UC San Francisco ...

Discovery could lead to better results for patients undergoing radiation

July 19, 2017
More than half of cancer patients undergo radiotherapy, in which high doses of radiation are aimed at diseased tissue to kill cancer cells. But due to a phenomenon known as radiation-induced bystander effect (RIBE), in which ...

Definitive genomic study reveals alterations driving most medulloblastoma brain tumors

July 19, 2017
The most comprehensive analysis yet of medulloblastoma has identified genomic changes responsible for more than 75 percent of the brain tumors, including two new suspected cancer genes that were found exclusively in the least ...

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.