Extracellular vesicles activate ATM‐Chk2 signaling pathway through the intercellular transfer of mitochondrial DNA in HBV‐infected human hepatocytes

Abstract Hepatitis B virus (HBV) is a human hepatotropic pathogen causing hepatocellular carcinoma. We recently obtained HBV‐susceptible immortalized human hepatocyte NKNT‐3 by exogenously expressing NTCP and its derived cell clones, #28.3.8 and #28.3.25.13 exhibiting different levels of HBV susceptibility. In the present study, we showed that HBV infection activated the ATM‐Chk2 signaling pathway in #28.3.25.13 cells but not in #28.3.8 cells. Both the cell culture supernatant and extracellular vesicles (EVs) derived from HBV‐infected #28.3.25.13 cells also activated the ATM‐Chk2 signaling pathway in naïve #28.3.25.13 cells. Interestingly, EVs derived from HBV‐infected #28.3.25.13 cells included higher level of mitochondrial DNA (mtDNA) than those from HBV‐infected #28.3.8 cells. Based on our results, we propose the novel model that EVs mediate the activation of ATM‐Chk2 signaling pathway by the intercellular transfer of mtDNA in HBV‐infected human hepatocyte.