Abstract 5546: CRISPR-based kinome screen identifies Ikbkb as a regulator of phagocytic evasion in hepatocellular carcinoma

Abstract Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent malignancies worldwide and is associated with poor prognosis. Recently, immune checkpoint inhibitors (ICIs) have revolutionized the oncology landscape by targeting genes critical for immune checkpoint pathways, leading to the immune evasion of cancer cells. Phagocytosis checkpoints have emerged as essential checkpoints for cancer immunotherapy by functioning as “don’t eat me” signal to suppress immune response. Given the druggable properties of protein kinases, together with recent reports showing the antitumor immunity of kinase inhibitors, we aimed to identify protein kinases critical for phagocytic evasion in HCC by transducing a lentiviral sgRNA expression plasmid containing 2,852 unique single-guide RNAs (sgRNAs) targeting the 713 mouse kinase gene in mouse HCC cells, RIL-175, and subsequently co-incubated with RAW 264.7 macrophages. Based on the deep sequencing analysis comparing the sgRNA distribution in RIL-175 with or without co-incubation, we identified the Ikbkb gene as top-sensitizing hit on this screen, with at least two-fold sgRNA reduction upon incubation with macrophages. To verify the phagocytic evasive role of Ikbkb in HCC, we have employed CRISPR/Cas9 knockout approach to delete Ikbkb in mouse HCC cell line, RIL-175 cells. The results showed that upon co-incubation with RAW 264.7 cells, the Ikbkb knockout cells exhibited increased phagocytosis, as confirmed by both flow cytometry analysis and microscopy observation. The analysis of the TCGA-LIHC cohort revealed that the expression level of Ikbkb was elevated and associated with unfavorable clinical outcomes. Notably, Ikbkb expression was found to be significantly correlated with established anti-phagocytic markers, including CD24, CD47, and CD274, further supporting their roles in the anti-phagocytic activities of HCC cells. In summary, we have uncovered IKBKB as a cancer-intrinsic regulator of phagocytosis, which has the potential to target IKBKB as a novel therapeutic strategy to enhance the efficacy of current ICI treatments for HCC patients. Citation Format: Sze Man Chan, Terence Kin Wah Lee. CRISPR-based kinome screen identifies Ikbkb as a regulator of phagocytic evasion in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5546.