Introduction: MicroRNAs (miRNAs) are a large class of single strand RNA molecules consistent of 18-25 nucleotides, involved in post transcriptional gene silencing. miRNAs show tissue-specific expression and play an important role in carcinogenesis.

The aim of the present study was: A. to identify colorectal cancer (CRC)-specific miRNAs. B. To study the potential value of CRC-specific miRNAs in CRC detection and staging.

Methods: This study was approved by the Institutional Review Board (IRB). RNA was extracted from paired samples of normal and tumor tissue of CRC patients (n=10). miRNA expression was tested using a commercially available array. Differential expression between normal and tumor tissues was identified in 30 human miRNAs and in additional 16 miRNAs identified from database mining. Differential expression was validated by quantitative (real-time) PCR in a larger cohort of samples (n=20). RNA was extracted from sentinel lymph nodes (SLN) of CRC patients. A calibration plot was generated using a CRC cell line (HT29) mixed with peripheral blood lymphocytes (PBL) of healthy donors in a range of concentrations.

Results: After validation, only 8 miRNAs were found to be overexpressed in CRC.

The detection threshold for all 8 miRNAs measured by the calibration plot was 1:1000 (one HT-29 cell in 1000 PBMCs). The expression of the 8 miRNAs was then tested in SLNs (n=86). Fourteen lymph nodes (16.3%) were positive by standard pathological examination (H&E staining) and 25/86 (29.1%) were positive by miRNA expression analysis (p<0.01). miRNA expression was detected in all sera from CRC patients (n=3) and in none of the sera obtained from healthy individuals (n=5, p<0.0001).

Conclusions: A panel of 8 miRNAs was found to be overexpressed in CRC patients. Occult residual disease was indentified in lymph nodes and serum of CRC patients using this miRNA panel.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3016.