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Introduction: Tumor-associated calcium signal transducer 2 (Trop2) has been used as a transport gate for cytotoxic agents into cells in antibody–drug conjugate designs because of its expression in a wide range of solid tumors. However, the specific role of Trop2 itself in breast cancer progression remains unclear and small molecules targeting Trop2 have not yet been reported. Objectives: To screen small molecules targeting Trop2, and to reveal its pharmacological effects and the molecular mechanisms of action. Methods: Small molecule targeting Trop2 was identified by cell membrane chromatography, and validated by cellular thermal shift assay and point mutation analyses. We investigated the pharmacological effects of Trop2 inhibitor using RNA-seq, human foreskin fibroblast (HFF)-derived extracellular matrix (ECM), Matrigel drop invasion assays, colony-forming assay, xenograft tumor model, 4T1 orthotopic metastasis model and 4T1 experimental metastasis model. The molecular mechanism was determined using immunoprecipitation, mass spectrometry, immunofluorescence, immunohistochemistry and Western blotting. Results: Here we identified Bruceine D (BD) as the inhibitor of Trop2, and demonstrated anti-metastasis effects of BD in breast cancer. Notably, Lys307 and Glu310 residues of Trop2 acted as critical sites for BD binding. Mechanistically, BD suppressed Trop2-induced cancer metastasis by blocking the formation of Trop2/β-catenin positive loop, in which the Trop2/β-catenin complex prevented β-catenin from being degraded via the ubiquitin-proteosome pathway. Destabilized β-catenin caused by BD reduced nucleus translocation, leading to the reduction of transcription of Trop2, the reversal of epithelial-mesenchymal transition (EMT) process, and the inhibition of ECM remodeling, further inhibiting cancer metastasis. Additionally, the inhibitory effects of BD on lung metastatic colonization and the beneficial effects of BD on prolongation of survival were validated in 4T1 experimental metastasis model. Conclusions: These results support the tumor-promoting role of Trop2 in breast cancer by stabilizing β-catenin in Trop2/β-catenin positive loop, and suggest Bruceine D as a promising candidate for Trop2 inhibition.

Hepatocellular carcinoma (HCC) is a globally prevalent and fatal malignancy worldwide, and identifying therapeutic strategies is time-consuming. Numerous reports have suggested the involvement of the NLRP3 inflammasome in the progression of various cancers. However, the detailed mechanisms underlying the role of NLRP3 inflammasome in HCC progression remain unclear. In this study, we observed low expression levels of the NLRP3 inflammasome in a subset of HCC cells. Furthermore, we demonstrated that the NLRP3 inflammasome can be activated by LPS + ATP through the nuclear factor kappa B signaling pathway, as confirmed by western blotting and immunofluorescence staining. To assess the impact of NLRP3 inflammasome activation on HCC cell behavior, we employed Edu staining, cell cycle assay, Annexin V/PI staining, and wound healing assay. Our results revealed that NLRP3 inflammasome activation inhibited the proliferation of Bel-7402 and SMMC-7721 cells, arrested the cell cycle at the G1 phase, and suppressed cell migration, while apoptosis remained unaffected. In summary, our findings suggest that targeting the NLRP3 inflammasome could have therapeutic potential for HCC.