Exosomal transfer of HCC-derived miR-17-5p downregulates NK cell function by targeting RUNX1-NKG2D axis.

Objective: Natural killer (NK) cells are an integral part of the staunch defense line against malignant tumors within the tumor microenvironment. Existing research indicates that miRNAs can influence the development of NK cells by negatively modulating gene expression. In this study, we aim to explore how the miR-17-5p in Hepatocellular Carcinoma (HCC) exosomes regulates the killing function of NK cells towards HCC cells through the transcription factor RNX1.

Methods: The exosomes were isolated from HCC tissues and cell lines, followed by a second generation sequencing to compare differential miRNAs. Verification was performed using qRT-PCR and Western blot methods. The mutual interactions between miR-17-5p and RUNX1, as well as between RUNX1 and NKG2D, were authenticated using techniques like luciferase reporter gene assays, Western blotting, and Chromatin Immunoprecipitation (ChIP). The cytotoxic activity of NK cells towards HCC cells in vitro was measured using methods such as RTCA and ELISPOT. The zebrafish xenotransplantation was utilized to assess the in vivo killing capacity of NK cells against HCC cells.

Results: The level of miR-17-5p in exosomes from HCC tissue increased compared to adjacent tissues. We verified that RUNX1 was a target of miR-17-5p and that RUNX1 enhances the transcription of NKG2D. MiR-17-5p was found to downregulate the expression of RUNX1 and NKG2D, subsequently reducing the in vitro and in vivo cytotoxic capabilities of NK cells against HCC cells.

Conclusions: The miR-17-5p found within HCC exosomes can target RUNX1, subsequently attenuating the cytotoxic activity of NK cells.