Discovery of small molecule β-catenin suppressors that enhance immunotherapy.

Small molecules directly downregulating β-catenin could potentially offer a more effective therapeutic approach for combating against cancer stem cells, as compared to targeting the downstream components of the Wnt/β-catenin pathway. The challenge, however, lies in the fact that very few β-catenin suppressors have proven clinically effective, leaving a significant gap in medical solutions. Given that E-cadherin has a natural affinity for β-catenin, it stands to reason that agents designed to increase E-cadherin expression might provide an alternative method of regulating β-catenin levels. In this study, we report our discovery of DSS-C12 and DSS-B8, specific ester-based drugs derived from Dan-Shen-Su (DSS) extracted from the herb Salvia miltiorrhiza. Remarkably, these compounds display a potent ability to downregulate β-catenin, while also improving overall survival in post-surgery mice. Additionally, when these drugs are used in combination with PD-L1 checkpoint blockade, they stimulate enhanced systemic immune responses leading to significant suppression of primary tumor growth. In-depth mechanistic studies revealed that DSS-B8 functions as a vitamin D receptor agonist without inducing hypercalcemic effects. Collectively, our findings indicate that DSS-derived small molecules have considerable potential as clinically viable therapeutic strategies for β-catenin deactivation.