MedWire News: Levels of two micro (mi)RNA molecules in stool samples could be used to screen for colorectal cancer (CRC), suggest study findings published in the journal Gut.
Expression of the non-coding miR-21 and miR-92a molecules has previously been shown to be significantly higher in CRC tissue than adjacent healthy tissue, and plasma levels of miR-92a are also significantly elevated in CRC patients, explain Jun Yu and co-authors, from The Chinese University of Hong Kong in Shatin, China.
To determine whether the miRNAs can also be used as stool sample markers for CRC, the team performed quantitative reverse transcription polymerase chain reaction on stool samples from 88 CRC patients, 57 patients with colorectal polyps, and 101 healthy individuals. Stool mR-21 and miR-92a levels were determined before and after removal of tumors or advanced adenomas in the patients.
Analysis showed that miR-92a levels in the stool samples were stable over 72 hours after collection, with a 30% degradation in the first 60 hours but no further deterioration thereafter.
In tissue samples taken from CRC patients, miR-21 and miR-92a levels were significantly higher in malignant tissue than in surrounding healthy tissues.
Moreover, levels of the two markers were significantly higher in stool samples from the CRC patients than in those from healthy controls. Stool miR-92a was significantly higher in patients with polyps than in controls, but no such differentiation was found for miR-21.
Using a cut-off of 435 copies/ng stool RNA, miR-92a had sensitivities of 71.6% and 56.1% for the detection of CRC and polyps, respectively, with corresponding specificity of 73.3% for both.
The researchers note that stool miR-92a was significantly more sensitive for distal than for proximal CRC, and for advanced adenoma than for minor polyps (< 1 cm diameter).
Stool levels of miR-21 and miR-92a fell significantly after the removal of CRC tumors, while miR-92a levels showed a significant decrease after removal of advanced adenomas.
Finding the markers to have moderate sensitivity and specificity for CRC and polyps, the researchers suggest the test could be used alone or as part of a miRNA panel for the disease.
"An alternative strategy would be to integrate stool-based miRNA markers such as miR-92a into an already existing molecular marker panel," conclude Yu et al.
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