The mir-199b-5p encapsulated in adipocyte-derived exosomes mediates radioresistance of colorectal cancer cells by targeting JAG1.

ABSTRACT

Radiotherapy is a key treatment option for colorectal cancer, but its efficacy varies among patients. Our previous studies suggested that adipose tissue may confer the radioresistance of several abdominal tumors, such as pancreatic cancer, biliary cancer, and others. In the present work, the effects of adipocytes in regulating the radiosensitivity of colorectal cancer are explored for the first time. It was found that colony formation was increased and radiation-induced apoptosis decreased in colorectal cancer cells HCT8 and HCT116 co-cultured with adipocytes, which verified the mediation of adipocyte-driven radioresistance in colorectal cancer in vitro. Next, the colorectal cancer cells were incubated with adipocyte-derived exosomes, and a perceptible reduction in radiosensitivity was detected. Furthermore, to investigate the possible mechanisms involved, the exosomes were isolated, the encapsulated microRNAs were extracted and analyzed by small RNA sequencing. Based on bioinformatics analysis and qRT-PCR verification, miR-199b-5p was chosen for functional annotation. It was shown that miR-199b-5p expression was significantly upregulated after 6 Gy irradiation, and overexpressed miR-199b-5p significantly suppressed the radiosensitivity of HCT8 and HCT116 cells. In addition, jagged canonical Notch ligand 1(JAG1) was identified as the target gene of miR-199b-5p by using bioinformatics prediction and dual luciferase reporter gene assay. It was demonstrated that JAG1 conferred the radioresistance of colorectal cancer cells both in vivo and in vitro. Taken together, the present study demonstrates that adipocytes trigger the radioresistance of colorectal cancer cells, probably by targeting JAG1 through an adipocyte-derived exosomal miR-199b-5p.