Detection of circulating microRNAs with Ago2 complexes to monitor the tumor dynamics of colorectal cancer patients during chemotherapy

Abstract

Because of the different forms of circulating miRNAs in plasma, Argonaute2 (Ago2)‐miRNAs and extracellular vesicles (EV‐miRNAs), we examined the two forms of extracellular miRNAs in vitro and developed a unique methodology to detect circulating Ago2‐miRNAs in small volumes of plasma. We demonstrated that Ago2‐miR‐21 could be released into the extracellular fluid by active export from viable cancer cells and cytolysis in vitro. As miR‐21 and miR‐200c were abundantly expressed in both metastatic liver sites and primary lesions, we evaluated Ago2‐miR‐21 as a candidate biomarker of both active export and cytolysis while Ago2‐miR‐200c as a biomarker of cytolysis in plasma obtained from colorectal cancer (CRC) patients before treatment and in a series of plasma obtained from CRC patients with liver metastasis who received systemic chemotherapy. The measurement of Ago2‐miR‐21 allowed us to distinguish CRC patients from subjects without CRC. The trend in ΔCt values for Ago2‐miR‐21 and ‐200c during chemotherapy could predict tumor response to ongoing treatment. Thus, capturing circulating Ago2‐miRNAs from active export can screen patients with tumor burdens, while capturing them from passive release by cytolysis can monitor tumor dynamics during chemotherapy treatment.

Extracellular Vesicles from Thyroid Carcinoma: The New Frontier of Liquid Biopsy

“…Circulating cell-free RNAs, like miRNAs, have also been explored as candidates for liquid biopsy in cancer patients [22]. It has been suggested that miRNAs are actively released in the extracellular fluid and in the bloodstream by viable cancer cells [23]. This is particularly interesting in the case of naïve patients because these biomarkers are abundantly released by viable cells before treatment.…”

Exosomal miRNA: Small Molecules, Big Impact in Colorectal Cancer

“…It is thereby possible that the circulating biomarker value of miR-21 comes mostly from its presence in exosomes. Nevertheless, it was recently shown that nonvesicular Ago2-associated miR-21 was actively released from HT29 CRC cell lines and that its levels could surpass those of EV-encapsulated miRNA in the absence of chemical lysis [120].…”

Current and New Predictors for Treatment Response in Metastatic Colorectal Cancer. The Role of Circulating miRNAs as Biomarkers

“…Extracellular miRNAs have two main sources: the miRNAs that cofractionate with Agonaut2 (Ago2) protein complexes which are thought to originate mainly from dead cells and the miRNAs that are released through extracellular vesicles (EV), mainly from viable cells and engaged in intracellular communication [72]. The authors hypothesized that by measuring levels of Ago2 miRNAs and EV miRNAs during chemotherapy, they would be able to assess the response to antitumor therapy.…”