Colorectal cancer is the third most common cancer and the second leading cause of cancer death in Europe. Therefore, the search for new biomarkers to enable facilitate early diagnosis, prognosis, and individualized treatment is particularly warranted. From a clinical point of view, malignancies in the colon and the rectum (RC) present two distinct entities that require different treatment strategies, so CRC might not be considered as a single enteropathogenic entity. MicroRNA (miRNAs) are small noncoding RNA molecules involved in the post-transcriptional and translational regulation of gene expression. The discovery that miRNAs may act either as oncogenes or tumor suppressors has initiated extensive research. It was recently discovered that extracellular miRNAs circulate in the bloodstream and that such circulating miRNAs are remarkably stable. This has raised the possibility that miRNAs might serve as novel markers for disease diagnosis and prognosis. In the present study, we aimed to identify circulating miRNAs enabling early diagnosis and prognosis of RC. MiRNA expression levels (from plasma and plasma exosomes) were characterized by next-generation sequencing (NGS) in 24 patients with RC collected at 2-time intervals. The first sampling was collected at the time of diagnosis and the second sampling was conducted around 1 year after the diagnosis. The expression levels of miR-122 and miR-142 were identified to be associated with overall survival in RC patients. Their functional characteristics were tested in vitro on rectal cancer cell lines HRA16 and SW1463. Increased levels of miRNAs were associated with decreased long-term survival of cells. Identified miRNAs are currently being verified on a larger population of RC patients. This has raised the question whether miRNA can serve as biomarkers for rectal cancer, but prior to its clinical applications, clinical trials are warranted. Acknowledgments: This work was supported by AZV 17-30920A, GA17-16857S, and GA UK 302119.

Citation Format: Klara Cervena, Alena Opattova, Barbara Pardini, Alessio Naccarati, Pavel Vodicka, Veronika Vymetalkova. Identification of circulating miRNA signatures in rectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr A56.