A genetic signature responsible for the spread of cancer or metastasis from one organ to another has been identified by US researchers.
Research collaborators from the Kimmel Cancer Center at Jefferson in Philadelphia and Ohio State University Medical Center in Columbus say that the signature they have found is made up mostly of over expressed microRNAs (miRNAs), tiny pieces of non-coding genetic material.
Presenting their findings at the annual meeting of the American Society of Clinical Oncology in Chicago, the researchers said that their work might represent a novel diagnostic tool in characterizing gene targets in metastatic cancer.
They pointed out that miRNAs play a number of roles in biological regulation, including development and cell differentiation.
When damaged, added the researchers, miRNAs can contribute to cancer by either turning on cancer-causing genes or by inhibiting tumour-blocking genes. The ways that MiRNAs are expressed have been used to profile tumour types in humans.
The researcher said that they wanted to see whether there was a specific gene signature that characterized metastasis, and they undertook the study for the purpose.
During the course of study, the group used micro-array technology that can facilitate the testing of many genes at once, and compared different organs-breast, lung, bladder, and colon-to see if miRNAs were either increased or decreased in activity.
They analysed the miRNAs in both primary and metastatic tumours from 43 patients, including 13 breast cancers, 10 lung cancers, 10 bladder urothelial cell cancers, and 10 colon cancers.
The researchers observed that some miRNAs were organ-specific.
"Some are increased and decreased specifically in certain organs, telling us that these are commonly involved in the metastatic process," said Dr. Raffaele Baffa, associate professor of Urology at Jefferson Medical College of Thomas Jefferson University.
Because of the ups and downs in miRNA activity, "many miRNAs that are involved in metastasis are not necessarily specific for one organ, but rather are related to the cell acquiring the ability to spread," he added.
Dr. Baffa further revealed that the group also found a direct association between the alterations in some miRNAs and changes in target proteins.
He said that many of the miRNAs that were overexpressed in primary tumours had previously been reported, confirming that miRNA signatures are useful in classifying tissue origin.
"Now we have to identify which of the miRNAs in the signature are the most important in facilitating metastasis," Dr. Baffa said.