September 06, 2008
MicroRNAs In Blood Show Patterns For Cancer And Pregnancy

A group of researchers in Nanjing China have demonstrated that each type of cancer shows a unique fingerprint of types of microRNA in the blood. This opens up the possibility of cheap screening for cancer detection.

Serum microRNAs (miRNAs) can serve as biomarkers for the detection of diseases including cancer and diabetes, according to research published online this week in Cell Research. The findings pave the way for a revolutionary non-invasive diagnostic tool.

“Nowadays, almost all of the routinely used serum markers are proteins and the conventional methodologies used to measure them remain labor-intensive. No serum-based test is currently suitable for widespread use in diseases diagnosis, particularly in early tumor detection,” said Chen-Yu Zhang of School of Life Sciences, Nanjing University. “Our goal therefore was to discover a novel class of serum biomarkers for clinic uses, even for drug screening and personalized medicine.”

miRNAs are a class of naturally occurring small non-coding RNAs that have been linked with cancer development. Recent studies reporting individual miRNAs as diagnostic biomarkers of specific cancers were unable to rule out the possibility that these miRNAs appeared as a result of contamination.

Chen-Yu Zhang and colleagues are the first to comprehensively characterize entire blood miRNA profiles of healthy subjects and patients with lung cancer, colorectal cancer and diabetes, ruling out contamination. They propose that the specific serum miRNA expression profiles they identified constitute ‘fingerprints’ for cancer and disease.

But will diagnosis using microRNAs lead to cancer cures? Detection at early stage is key. Longitudinal studies that watch the same subjects from healthy starting points until disease diagnosis are probably needed in order determine whether microRNAs will allow early detection of cancer. Early stages of these studies could probably be conducted first in mice and other species with shorter lives where the time between healthy to cancerous is shorter.

Separately an Israeli group has just published a paper in Plos One where they demonstrate that circulating microRNA show distinct patterns between pregnant and non-pregnant women.

Finally, as a proof of concept, we investigated whether circulating microRNAs can be used to identify clinical conditions. It has been established that circulating maternal RNA contains placental embryonic RNA [2]. Therefore, we chose to compare the serum microRNA abundance profiles of non pregnant versus pregnant women, the latter in either their first or third trimester. We measured the serum levels of 28 microRNAs, including microRNAs reported to be placenta-specific [10], [20] as well as broadly expressed microRNAs. Box plots show relative microRNA levels in the sera of 10 non pregnant women, 10 women in the first trimester and 10 women in the third trimester (Figure 4A). The median fold changes in microRNA levels comparing third trimester pregnant women to non pregnant women are detailed in Table 1. MicroRNAs expressed equivalently across all samples were used for normalization. All of the placental microRNAs are found at higher levels in the sera from pregnant women, their levels rising with gestational age, and the levels of 12 microRNAs increased by more than 5-fold. Specifically, amounts of hsa-miR-526a and hsa-miR-527 are dramatically higher in the sera of third trimester pregnant women (elevated by more than 600 fold). Indeed, we found that the levels of three placental microRNAs (hsa-miR-526a, hsa-miR-527 and hsa-miR-520d-5p) could be used to accurately distinguish pregnant from non pregnant women (Figure 5).

This seems like a technology that could be commercialized pretty quickly. If microRNAs can detect cancers at early stages then going to the doctor a few times a year for periodic microRNA tests might replace many uses of colonoscopy, mammography, pap smears, and other early stage cancer tests.

I expect that microRNA expression patterns change with age and at different rates for different people. This might lead to more accurate ways to predict life expectancy. But will that allow extension of life expectancies? Or will it just give people a better idea of how much to save for retirement?

Share |      Randall Parker, 2008 September 06 08:14 PM  Biotech Assay Tools

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