Moreover, we discovered that the protein level of EWSR1 was significantly elevated in RAD18 knockdown HCC cells, while its ubiquitination level was clearly decreased, suggesting that RAD18 acted as an E3 ubiquitin ligase that can degrade EWSR1 via the ubiquitin‐proteasome pathway in HCC cells (Figure 4O; Figure S4E, Supporting Information). Here, RAD18 is linked to hepatocellular carcinoma.