Restoring MicroRNA expression stops the spread of liver cancer in mice
(24 June 2009: VIDYYA MEDICAL NEWS SERVICE) -- Researchers from the Johns Hopkins University School of Medicine have shown that restoring the expression of a single microRNA (miRNA) that had been lost in liver cancer cells could prevent tumor growth in mice. miRNAs are short strands of RNA that regulate the activity of genes, including some that are involved in cancer. The study results appeared June 12 in Cell.
The researchers chose the microRNA miR-26a, which is abundant in normal adult liver tissue but lacking in both human liver cancer (hepatocellular carcinoma or HCC) and in the mouse model of HCC used in their experiments.
After initiating liver tumor formation in their mouse model, the researchers restored miR-26a to the tumor cells by injecting a virus engineered to specifically target liver tissue. The virus contained the miR-26a gene and a gene for a fluorescent protein to allow the researchers to visualize successful transfer.
Eight out of 10 mice that received the virus containing the miR-26 gene developed only small tumors or did not develop measurable tumors. The two mice that did develop aggressive tumors had significantly less of the miR-26a gene successfully delivered to their liver tissue. Six out of eight control mice that did not receive the miR-26a gene developed aggressive disease.
miR-26a is not thought to target a specific oncogene responsible for initiating liver tumors. Instead, it worked by generally inhibiting cancer cell proliferation and inducing apoptosis (cell death). No measurable effects were seen in normal liver cells, likely due to their naturally high levels of the miRNA.
The study "provides proof-of-principle that the systemic administration of miRNAs may be a clinically viable anticancer therapeutic strategy," concluded the authors.
Among the Elderly, Adverse Events from Colonoscopy Are Rare
Older individuals who undergo outpatient colonoscopy have a low risk of adverse events, but the risk increases with advancing age and in individuals with certain health conditions, such as diabetes, stroke, and congestive heart failure. The findings are from the first study to assess complications from outpatient colonoscopy in older individuals. NCI researchers analyzed the Medicare records of 53,220 people aged 66 to 95 who underwent colonoscopy between 2001 and 2005.
"Colorectal cancer screening is very important for the prevention of this disease, and we need to know whether colonoscopy is a safe method of colorectal cancer screening as a person gets older and whether there are specific health conditions that can increase one's risk," said lead investigator Dr. Joan Warren of NCI's Division of Cancer Control and Population Sciences. "Until now there have been no data on these questions out there."
As the researchers reported today in the Annals of Internal Medicine, the risk of a serious gastrointestinal event within 30 days following colonoscopy was 6.9 per 1,000 procedures. However, the risk of a serious gastrointestinal event for persons aged 85 and older was more than twice that for persons aged 66 to 69.
The results are consistent with recommendations made last October by the U.S. Preventive Services Task Force, noted Dr. Warren. The Task Force advised against colorectal cancer screening in adults older than age 85 because the potential benefits were small compared to the risks. The group also recommended against routine screening for individuals aged 76 to 85.
The findings will likely contribute to an ongoing debate about the use of screening colonoscopy among individuals who have a limited life expectancy because of advanced age or existing health conditions. In their report, the researchers urged clinicians to incorporate the results into their discussions with patients about the risks of colonoscopy.
Return to Vidyya Medical News Service for 24 June 2009
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