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Johns Hopkins University (JHU) scientists have developed a gene-based test to distinguish harmless from precancerous pancreatic cysts, and which could eventually help some patients avoid needless surgery to remove the harmless variety. The investigators estimate that fluid-filled cysts are identified in more than a million patients each year, most of whom have undergone CT or MRI scans to evaluate non-specific symptoms, such as abdominal pain and swelling.
Dr Bert Vogelstein, co-director of the Ludwig Center at JHU and a Howard Hughes Medical Institute investigator, and his colleagues analysed precancerous cysts from 19 patients and searched for mutations in 169 cancer-causing genes. They found mutations in the KRAS gene, known for its prevalence in pancreatic cancers, and the GNAS gene, which had not previously been associated with pancreatic cancer. In both KRAS and GNAS, the mutations occur at a single coding spot in the DNA, the equivalent of a typo in a word within an entire encyclopaedia. KRAS and GNAS genes produce signalling proteins, relaying signals from the cell surface to areas within the cell.
The researchers then tested a total of 132 precancerous pancreatic cysts for mutations in KRAS and GNAS. The latter were found in more than half of the samples (87 of them), and KRAS mutations occurred in 107 samples. Nearly all (127) had mutations in GNAS, KRAS or both. The mutations occurred in large and small, high- and low-grade cysts, and in all major types of the most common precancerous pancreatic cysts. There were no major differences in age, gender or smoking history for people with GNAS or KRAS mutations in their cysts’ cells. Finally, the investigators tested tissue from pancreatic cancers that had developed in eight people with GNAS-mutated cysts. Seven of the eight had GNAS mutations in their cancer, as well as cells in the cysts.
GNAS and KRAS mutations were not found in benign cysts, although KRAS mutations did appear occasionally in a rare type of cyst with a relatively low potential to become cancerous. These rare, mostly benign cysts are less challenging to diagnose because of their location within the pancreas and type of patient, according to the investigators. Genetic analysis of the kind reported in the new study offers a new way to sort the potential of these cysts to cause malignant trouble.
The investigators caution that cyst fluid removal, an invasive procedure, also has its drawbacks and can cause bleeding, infection and inflammation in a very small percentage of patients. Further studies on a larger number of patients are expected to be done before the gene-based test can be widely offered. However, Vogelstein says that the technology for developing a gene-based test in this case is relatively straightforward because “the mutation occurs at one spot in both of the genes.”
Major funding for the study was provided by the Lustgarten Foundation, a private foundation that provides to funding pancreatic cancer research. Other funding was provided by the Virginia and D K Ludwig Fund for Cancer Research, the Sol Goldman Center for Pancreatic Cancer Research, the Joseph L Rabinowitz Fund, the Michael Rolfe Foundation, the Indiana Genomics Initiative of Indiana University, which is supported in part by Lilly Endowment., the J.C. Monastra Foundation, Swim Across America and the National Institutes of Health. JHU has filed a patent application on inventions described in the study.
Thanks to Lawrence Miller for this post, if you woul like more information like this, or to start your subscription please click on the link Diagnostics Focus Newsletter
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