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A new study published online in the journal Nature completely upends current thinking about the development of pancreatic cancer, with researchers reporting that the tumors develop not in a sequential, gradual fashion, but in a simultaneous explosion of genetic alterations.
Pancreatic cancer is currently the fourth-leading cause of cancer-related death in the U.S., but is expected to become the second-leading cause of death by 2020. Symptoms typically don’t manifest until late in the disease stage, however, when the tumor has metastasized. Few patients survive more than five years after diagnosis.
Researchers from Ontario Institute for Cancer Research and the Princess Margaret University Health Network’s Princess Margaret Cancer Centre in Toronto set out to explore an ongoing mystery about the disease: How does pancreatic cancer progress so quickly from localized tumor to metastasis?
“The traditional view of the biology of the disease just didn’t [jibe] with what happens clinically,” said lead author Faiyaz Notta, PhD, of the Princess Margaret Cancer Centre, in a statement. “And it’s hard to move forward in trying to find new treatments if you can’t link the biology of the tumor to the clinical reality of the disease.”
Notta and his team developed a new informatics process called CELLULOID, which estimates tumor ploidy and copy number from whole-genome data. They used it to assess whole-genome sequence data for 107 primary or metastatic pancreatic ductal adenocarcinoma tumors.
They found that 45% of the tumors displayed changes in copy number that were consistent with polyploidization. These ploidy changes had a particularly high incidence in tumors containing TP53 gene mutations.
In addition, 65% of the tumors showed evidence of chromothripsis events, which was confirmed in an independent genome cohort of 84 additional pancreatic cancer samples.
“If chromothripsis is indeed the transforming event in some tumors, as our data suggest, a single event could thus confer a cell with both invasive and metastatic properties,” Notta and his coauthors wrote. “In this scenario, there would be a very short latency period between the birth of the invasive clone and the ability of that clone to metastasize.”
The findings, they wrote, have implications for the development of earlier methods of diagnosis, and the use of treatments that can target upstream processes leading to chromothripsis.
“How these mutational processes contribute to disease progression and metastatic phenotype is therefore a critical topic of investigation,” they wrote. “Such knowledge will be essential to guide more effective screening and therapeutic strategies, both for pancreatic cancer and other aggressive tumor types.”