Abstract 1175: Persistent upregulation of U6 small RNA in the serum of breast cancer patients

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Serum microRNAs have the potential to be valuable biomarkers of cancer. This investigation addresses two issues that impact their utility: a) appropriate normalization controls and b) whether their altered levels persist in patients who are clinically free of disease. Sera from 40 age-matched healthy women and 39 breast cancer patients without clinical disease at the time of serum collection were analyzed for microRNAs let-7f, miR-16, miR-21, and miR-155 using quantitative real-time PCR. U6 and 5S, which are transcribed by RNA polymerase III (RNAP-III), and the small nucleolar RNA44 (SNORD44), were also analyzed for normalization. Sera from additional 14 healthy and 15 patients with overt metastasis were examined for U6, miR-16, and miR-195 levels. SNORD44 and miR-16 did not vary significantly in the sera of patients and healthy volunteers and thus served as normalization controls. Unexpectedly, we observed upregulation of U6 (2.4 fold, p=0.001) and 5S RNAs (1.7-fold, p=0.02) but not any of the other microRNAs analyzed in the sera of patients without active disease. U6 level was significantly elevated in the sera of patients with overt metastasis compared to healthy women. Elevated serum U6 levels in patients who are clinically cancer-free suggest persistently altered systemic RNAP-III activity in cancer patients and that cancer cells may not be the only primary source of serum U6. Additionally, U6 and 5S, to some extent, are of limited value for normalization. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1175. doi:10.1158/1538-7445.AM2011-1175