HRNR and hepatocellular carcinoma: In summary, CircCDYL stabilizes HRNR expression by directly binding to HRNR and preventing its ubiquitination, thereby activating the mTOR signaling pathway to upregulate PD-L1 expression in hepatocellular carcinoma (HCC) cells, ultimately leading to the reduction in the sensitivity of HCC cells to anti-PD-L1 therapy and the sustainment of tumor invasiveness (31).