Colorectal cancer (CRC) accounts for 9.7% of all cancers which makes it one of the three most commonly diagnosed cancer types worldwide. Prognosis of the patients with CRC depends mainly on the extent of the disease at the time of diagnosis. Therefore, the early detection of CRC and precancerous lesions is one of the main requirements of successful treatment. In recent years exosomes emerged as potential reservoirs of clinically useful biomarkers. Exosomes are 30-150 nm sized membranous vesicles that are endogenously produced by almost all cell types. They participate in intercellular communication by delivering proteins, microRNAs (miRNAs), mRNAs or long non-coding RNAs (lncRNAs) to recipient cells. In the context of cancer, intercellular communication allows cancer cells to create a favorable microenvironment for their growth. It has been shown that cancer-derived exosomes promote pathways contributing to hallmarks of cancer.To investigate diagnostic potential of exosomal RNA in CRC, blood serum samples were collected from patients with CRC and age- and sex-matched controls. Exosome isolation protocol was optimized, and the presence of vesicles in the exosome size range was confirmed using both dynamic light scattering (DLS) analysis as well as electron microscopy (TEM). Downstream analysis of serum exosomal RNA using next-generation sequencing (Illumina NextSeq 550) from exploratory cohort of CRC samples (N=50) and healthy controls (N=20) revealed both coding and non-coding RNAs to be differentially expressed (FC>1.5, p-value < 0.01). Among these were genes already reported to be dysregulated in CRC such as GAS5, but also lncRNAs previously unreported in CRC exosomes (AC103760.1, LINC02709 or PGBP) were identified.

Gene set enrichment analysis (GSEA) was used to link RNAs identified within exosomes to their molecular functions. Using the Hallmark gene sets (MsigDB) as a reference, we discovered high enrichment of genes related to MYC targets, E2F targets and G2M checkpoint in healthy controls compared to CRC samples. All three hallmarks comprise genes crucial for cell proliferation. The first results indicated that the exosomal RNAs could be promising candidates as new diagnostic biomarkers in CRC, although further in vitro and in vivo exploration of identified differentially expressed lncRNAs is necessary. This work was supported by Ministry of Health of the Czech Republic grant nr. NU20-03-00127, NV19-03-00501 and NV19-03-00559. All rights reserved.

Citation Format: Tina Catela Ivkovic, Marie Mądrzyk, Karolina Trachtova, Petra Faltejskova-Vychytilova, Tana Machackova, Petra Pokorna, Jaroslav Juracek, Jiri Sana, Ondrej Slaby. Molecular and functional characterization of colorectal cancer derived-exosomes and exosomal coding and long non-coding RNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2802.