Satb1 Overexpression Drives Tumor-Promoting Activities In Cancer-Associated Dendritic Cells

Special AT-rich sequence-binding protein-1 (Satb1) governs genome-wide transcriptional programs. Using a new conditional knockout mouse, we found that Satb1 is required for normal differentiation of conventional dendritic cells (DCs). Furthermore, Satb1 governs the differentiation of inflammatory DCs by regulating MHC-II expression through Notch1 signaling. Mechanistically, Satb1 binds to the Notch1 promoter, activating Notch expression and driving RBPJ occupancy of the H2-Ab1 promoter, which activates MHC-II transcription. However, tumor-driven, unremitting expression of Satb1 in activated Zbtb46+ inflammatory DCs that universally infiltrate ovarian tumors results in an immunosuppressive phenotype characterized by increased secretion of tumor-promoting Galectin-1 and IL-6. Correspondingly, specific in vivo silencing of Satb1 in tumor-associated DCs reverses their tumorigenic activity and boosts protective immunity. Therefore, dynamic fluctuations in Satb1 expression govern the generation and immunostimulatory activity of steady-state and inflammatory DCs, but relentless Satb1 overexpression in differentiated DCs converts them into tolerogenic/pro-inflammatory cells that contribute to malignant progression. Overall design: RNA-seq with whild type and knocked-down Satb1