Nanostring gene expression analysis of Tregs islated from Kdr KO versus transgene control SB1 tumors

Tumor-infiltrating Tregs were FACS sorted using their YFP signal from processed SB1 tumors implanted in Kdr(fl/fl)xFoxp3(yfp-cre) or Kdr(+/+)xFoxp3(yfp-cre) mice, fro which RNA was isolated for Nanostring analysis usig the Murine Cancer Immune Profiling Panel Anti-VEGF treatment has shown clinical activity in combination with checkpoint inhibitor therapy, but the exact mechanism is not known. We show that adding VEGF blockade to the ICB combination of anti-CTLA4 + anti-PD-L1 in cholangiocarcinoma unleashed a therapeutic efficacy driven through a novel multimodal mechanism dependent on BAFF production by T and myeloid cells, leading to a BAFF-dependent proinflammatory B cell response characterized by Germinal center B cell and plasma cell expansion, as well as IL-12 production. The mechanism culminates in a BAFF and IL-12-dependent expansion and rewiring of Tregs towards an anti-tumor Th-1-like fragile state. We translated this approach to the clinic with encouraging outcomes following an interim analysis of the first six CCA patients. Using paired PBMC, serum and tumor biopsy samples from patients treated with anti-CTLA4, anti-PD-L1 and anti-VEGF, we again observed treatmentassociated immunological changes characterized by Treg expansion and rewiring towards fragile and unstable states and a proinflammatory cytokine profile including elevated BAFF and IL-12 levels. Correlating immune changes with overall survival identified BAFF and IL-12 as potential biomarkers of treatment response. Finally, we explored the direct effect of VEGFR2 signaling on Treg transcriptional programming. Fragile and unstable Tregs showed diminished VEGF/VEGFR2 signaling. A mouse model genetically ablating VEGFR2 expression on Tregs led to diminished suppressive function and delayed tumor growth, an effect that was further enhanced by ICB therapy. 6 samples were analysed including 3 biological replicates fro 2 groups (KO versus control)