Abstract B11: Level of circulating miRNAs in patients before and after surgical removal of colorectal tumors: A pilot study

Abstract

Abstract Introduction: MicroRNAs (miRNAs) are small, noncoding RNAs that function as regulators of many critical cellular processes, are known to be abnormally expressed in cancer, and play a role either by oncogenic or tumor-suppressor function. miRNA expression differs between normal and tumor tissue and varies among tissue types. Upregulated miRNAs in tumor tissue can also be detected in the blood circulation and are emerging as promising biomarkers. So far, little is known about how rapid changes, i.e. surgical removal of a colorectal tumor, will be reflected by changing miRNA level in the circulation. Thus, within this pilot study we aim to characterize the level of circulating miRNA prior to and after surgical removal of a colorectal tumor. Methods: The investigations are based on the ColoCare Study, an ongoing cohort study of colorectal cancer patients (stage I-IV). Newly-diagnosed colorectal cancer patients are recruited at the ColoCare study site in Heidelberg, Germany prior to surgery for tumor resection. For this pilot study, pre- and post-surgical blood (4.1 (2-9) days after surgery) from n=31 patients was examined. Plasma was obtained by centrifugation (2,500 x g) and stored at -80°C upon isolation of miRNA using the Qiagen miRNeasy Mini Kit. We selected 17 candidate miRNAs which have been previously noted to be altered in the circulation of colorectal cancer patients. miRNA levels (n=17) were measured by qRT-PCR using Taqman miRNA reverse transcription kits with miRNA-specific stem-loop primers and Taqman MicroRNA Assays. Data were normalized by subtracting the CT value of the spike-in control (cel-miR-39) from the target miRNA's CT value and miRNA expression is presented as 2−ΔCT transformed values. Statistical analysis was performed using log-transformed normalized CT values using PROC GLM (SAS 9.2). Results: Study participants were on average 61 years old (35-79), 10 of the participants were diagnosed with colon and 21 with rectal cancer. Ten patients had later stage disease (stages III or IV). Comparing pre- and post-surgical miRNA levels, revealed a statistically significant decrease of 7 circulating miRNAs (miR-106a: p=0.002, miR-16: p=0.02, miR-18a: p=0.004, miR20a: p=0.01, miR223: p=0.04, miR-320: p=0.006, miR-92: p=0.0008). The remaining candidate miRNAs did not change significantly between the time points. Conclusion: Although the sample size of this pilot study is small, we observed a substantial decrease of 7 target miRNAs approximately one week after surgical tumor removal. Our results underscore the role of these miRNAs in colorectal carcinogenesis. As next steps, we will continue characterizing the changes in plasma level of the described miRNAs for subsequent post-surgical follow-up time points. Citation Format: Nina Habermann, Jonas Ristau, Katharina Buck, Jürgen Staffa, Petra Schrotz-King, Dominique Scherer, Stephanie Tosic, Verena Widmer, Clare Abbenhardt, Karen W. Makar, Barbara Burwinkel, Cornelia M. Ulrich. Level of circulating miRNAs in patients before and after surgical removal of colorectal tumors: A pilot study. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B11.