CRISPR/Cas9 screen identifies DCAF4 as a novel protector of hepatocellular carcinoma against brachytherapy via stress granule-dependent NRF2 activation

Hepatocellular carcinoma (HCC) cells sustain viability and radioresistance by actively countering oxidative stress. Understanding the mechanisms regulating reactive oxygen species (ROS) homeostasis is therefore crucial for developing novel therapies. Using integrated genome-wide CRISPR-Cas9 screening coupled with transcriptomic and metabolomic profiling, we identified DDB1 and CUL4-associated factor 4 (DCAF4) as an essential regulator of oxidative stress resistance in HCC. Mechanistically, DCAF4 functions as a CRL4 E3 ligase adapter that promotes KEAP1 ubiquitination and degradation. Notably, under oxidative stress, cytoplasmic stress granules (SGs) form a localized platform that facilitates the DCAF4–KEAP1 interaction, accelerating KEAP1 degradation and leading to NRF2 activation and upregulation of antioxidant genes. We further identified that the transcription factor XBP1 enhances DCAF4 expression. Targeting this axis, we performed computational screening to identify a small-molecule inhibitor that disrupts the DCAF4–KEAP1 interaction. This compound effectively enhanced brachytherapy (BT) sensitivity and inhibited tumor growth in preclinical HCC models.