Abstract
Background: Exosomes are nano-sized extracellular vesicles and are detectable in most body fluids. Circulating exosomal microRNAs are an easily obtained, and they could be minimally invasive biomarker for cancer treatment. Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive carcinomas. Radiotherapy is one of the most important treatment option for ESCC, and it would thus be extremely crucial to predict therapeutic sensitivity and the patient prognosis in advance. Methods: A search for miRNAs with a therapeutic biomarker in ESCC was performed using the miRNA expression signatures obtained from ESCC plasma before radiotherapy. miR-191-5p was selected because it was found to be associated with the prognosis in ESCC based on the findings of previous reports. As a result, we decided to perform more studies to elucidate the significance of miR-191-5p. Gain-of-function analyses were performed to evaluate the functional significance of miR-191-5p in ESCC progression. The effects of miR-191-5p on ESCC radiosensitivity were determined by cell proliferation, a clonogenic survival assay and an apoptosis assay. A gene set enrichment analysis was used to investigate the downstream signaling pathway related to the miR-191-5p functions. The 5-year progression-free survival (PFS) rate was used to directly compare the usefulness of these biomarkers for determining the patient prognosis between the miR-191-5p high expression patients and low expression patients. Results: A subset of seven microRNAs (miR-628, miR-363, miR-191-5p, miR-185, miR-148a, miR-320d, miR-30e) was identified to be candidates of therapeutic biomarker for ESCC patients underwent radiotherapy in a global microRNA expression analysis. A high miR-191-5p expression promoted ESCC cell proliferation, invasion and migration and induced G0/G1 to S/G2M transition. miRNA-191-5p overexpression promoted cell survival and reduced cell apoptosis after irradiation. Mechanistically, miR-191-5p may directly target death-associated protein kinase 1 (DAPK1) to induce radiation resistance via the MAPK-JNK pathway. The 5-year progression-free survival rate for ESCC patients who underwent radiotherapy with high circulating exosomal miR-191-5p expression was significantly lower than in those with a low expression. Conclusion: Tumor-derived exosomal miR-191-5p is a potential non-invasive biomarker for predicting the prognosis in esophageal cancer patients after radiotherapy.
Circulating exosome-derived miR-191-5p is a novel therapeutic biomarker for radiotherapy in esophageal squamous cell carcinoma patients