Pharmacological inhibition of β-catenin/BCL9 interaction overcomes resistance to immune checkpoint blockades by modulating Treg cells.

The Wnt/β-catenin (β-cat) pathway plays a critical role in cancer. Using hydrocarbon-stapled peptide technologies, we aim to develop potent, selective inhibitors targeting this pathway by disrupting the interaction of β-cat with its coactivators B-cell lymphoma 9 (BCL9) and B-cell lymphoma 9-like (B9L). We identified a set of peptides, including hsBCL9CT-24, that robustly inhibits the activity of β-cat and suppresses cancer cell growth. In animal models, these peptides exhibit potent anti-tumor effects, favorable pharmacokinetic profiles, and minimal toxicities. Markedly, these peptides promote intratumoral infiltration of cytotoxic T cells by reducing regulatory T cells (Treg) and increasing dendritic cells (DCs), therefore sensitizing cancer cells to PD-1 inhibitors. Given the strong correlation between Treg infiltration and APC mutation in colorectal cancers, it indicates our peptides can reactivate anti-cancer immune response suppressed by the oncogenic Wnt pathway. In summary, we report a promising strategy for cancer therapy by pharmacological inhibition of the Wnt/β-cat signaling.