Circulating microRNAs in breast cancer and healthy subjects

We measured miRNA in the serum of samples with and without the addition of miRNA prior to analysis. To test our RNA extraction efficiency, we spiked-in serial dilutions of single-strand C elegens miR-39 (cel-miR-39) and human miR-145 (has-miR-145) into goat serum and a 10 year old human serum specimen. We next analyzed miR-16, -145, and -155 in archived serum specimens from 21 participants, 13 of whom did and 8 of whom did not have breast cancer. We were able to detect the miRNAs from all the serum samples to which the miRNAs had been added. We were also able to detect endogenous miR-16, -145, and -155 in all serum samples. While the expression of all three miRNAs was similar in samples from healthy women compared to those with breast cancer, women with progesterone receptor (PR, p = 0.016) positive tumors had higher miR-155 expression than tumors that were negative for these receptors.1) RNA species can be detected in archived serum; 2) miR-155 may be differentially expressed in the serum of women with hormone sensitive compared to women with hormone insensitive breast cancer. Screening serum for miRNAs that predict the presence of breast cancer is feasible, and may be useful for breast cancer detection.There is increasing evidence supporting microRNA (miRNA) analysis for breast cancer diagnosis, prognosis and therapy [1-3]. miRNAs are ~22 nucleotide long RNA molecules encoded in the genome that can control gene expression. Their expression levels vary greatly among species and tissues [4]. Over 700 miRNAs have been identified from human tissue. Some of these short, endogenous non-protein coding miRNAs are linked to human malignancy and are differentially expressed in human cancer vs. matched normal tissue [5]. For example, a recent publication identified 29 miRNAs that were aberrantly expressed in primary breast cancer tissue. Of the 29, miR-10b, miR-125b, and miR-145 were down-regulated, while miR-21 and miR-155 were up-regulated [6]. Depending on the genes that