Immune checkpoint therapy-elicited sialylation of IgG antibodies impairs antitumorigenic type I interferon responses in hepatocellular carcinoma.

The reinvigoration of anti-tumor T cells in response to immune checkpoint blockade (ICB) therapy is well established. Whether and how ICB therapy manipulates antibody-mediated immune response in cancer environments, however, remains elusive. Using tandem mass spectrometric analysis of modification of immunoglobulin G (IgG) from hepatoma tissues, we identified a role of ICB therapy in catalyzing IgG sialylation in the Fc region. Effector T cells triggered sialylation of IgG via an interferon (IFN)-γ-ST6Gal-I-dependent pathway. DC-SIGN+ macrophages represented the main target cells of sialylated IgG. Upon interacting with sialylated IgG, DC-SIGN stimulated Raf-1-elicited elevation of ATF3, which inactivated cGAS-STING pathway and eliminated subsequent type-I-IFN-triggered antitumorigenic immunity. Although enhanced IgG sialylation in tumors predicted improved therapeutic outcomes for patients receiving ICB therapy, impeding IgG sialylation augmented antitumorigenic T cell immunity after ICB therapy. Thus, targeting antibody-based negative feedback action of ICB therapy has potential for improving efficacy of cancer immunotherapies.

Targeting inflammatory macrophages rebuilds therapeutic efficacy of DOT1L inhibition in hepatocellular carcinoma.

Epigenetic reprogramming is a promising therapeutic strategy for aggressive cancers, but its limitations in vivo remain unclear. Here, we showed, in detailed studies of data regarding 410 patients with human hepatocellular carcinoma (HCC), that increased histone methyltransferase DOT1L triggered epithelial-mesenchymal transition-mediated metastasis and served as a therapeutic target for human HCC. Unexpectedly, although targeting DOT1L in vitro abrogated the invasive potential of hepatoma cells, abrogation of DOT1L signals hardly affected the metastasis of hepatoma in vivo. Macrophages, which constitute the major cellular component of the stroma, abrogated the anti-metastatic effect of DOT1L targeting. Mechanistically, NF-κB signal elicited by macrophage inflammatory response operated via a non-epigenetic machinery to eliminate the therapeutic efficacy of DOT1L targeting. Importantly, therapeutic strategy combining DOT1L-targeted therapy with macrophage depletion or NF-κB inhibition in vivo effectively and successfully elicited cancer regression. Moreover, we found that the densities of macrophages in HCC determined malignant cell DOT1L-associated clinical outcome of the patients. Our results provide insight into the crosstalk between epigenetic reprogramming and cancer microenvironments and suggest that strategies to influence the functional activities of inflammatory cells may benefit epigenetic reprogramming therapy.