Discovery of an Orally Bioavailable Small-Molecule Inhibitor for the β-Catenin/B-Cell Lymphoma 9 Protein-Protein Interaction

Aberrant activation of Wnt/β-catenin signaling is strongly associated with many diseases including cancer invasion and metastasis. Small-molecule targeting of the central signaling node of this pathway, β-catenin, is a biologically rational approach to abolish hyperactivation of β-catenin signaling but has been demonstrated to be a difficult task. Herein, we report a drug-like small molecule, ZW4864, that binds with β-catenin and selectively disrupts the protein-protein interaction (PPI) between B-cell lymphoma 9 (BCL9) and β-catenin while sparing the β-catenin/E-cadherin PPI. ZW4864 dose-dependently suppresses β-catenin signaling activation, downregulates oncogenic β-catenin target genes, and abrogates invasiveness of β-catenin-dependent cancer cells. More importantly, ZW4864 shows good pharmacokinetic properties and effectively suppresses β-catenin target gene expression in the patient-derived xenograft mouse model. This study offers a selective chemical probe to explore β-catenin-related biology and a drug-like small-molecule β-catenin/BCL9 disruptor for future drug development.

Targeting Casein Kinase 1 Delta Sensitizes Pancreatic and Bladder Cancer Cells to Gemcitabine Treatment by Upregulating Deoxycytidine Kinase

Although gemcitabine is the cornerstone of care for pancreatic ductal adenocarcinoma (PDA), patients lack durable responses and relapse is inevitable. While the underlying mechanisms leading to gemcitabine resistance are likely to be multifactorial, there is a strong association between activating gemcitabine metabolism pathways and clinical outcome. This study evaluated casein kinase 1 delta (CK1δ) as a potential therapeutic target for PDA and bladder cancer, in which CK1δ is frequently overexpressed. We assessed the antitumor effects of genetically silencing or pharmacologically inhibiting CK1δ using our in-house CK1δ small-molecule inhibitor SR-3029, either alone or in combination with gemcitabine, on the proliferation and survival of pancreatic and bladder cancer cell lines and orthotopic mouse models. Genetic studies confirmed that silencing CK1δ or treatment with SR-3029 induced a significant upregulation of deoxycytidine kinase (dCK), a rate-limiting enzyme in gemcitabine metabolite activation. The combination of SR-3029 with gemcitabine induced synergistic antiproliferative activity and enhanced apoptosis in both pancreatic and bladder cancer cells. Furthermore, in an orthotopic pancreatic tumor model, we observed improved efficacy with combination treatment concomitant with increased dCK expression. This study demonstrates that CK1δ plays a role in gemcitabine metabolism, and that the combination of CK1δ inhibition with gemcitabine holds promise as a future therapeutic option for metastatic PDA as well as other cancers with upregulated CK1δ expression.

Therapeutic Targeting of CDK12/CDK13 in Triple-Negative Breast Cancer

Epigenetic regulation enables tumors to respond to changing environments during tumor progression and metastases and facilitates treatment resistance. Targeting chromatin modifiers or catalytic effectors of transcription is an emerging anti-cancer strategy. The cyclin-dependent kinases (CDKs) 12 and 13 phosphorylate the C-terminal domain of RNA polymerase II, regulating transcription and co-transcriptional processes. Here we report the development of SR-4835, a highly selective dual inhibitor of CDK12 and CDK13, which disables triple-negative breast cancer (TNBC) cells. Mechanistically, inhibition or loss of CDK12/CDK13 triggers intronic polyadenylation site cleavage that suppresses the expression of core DNA damage response proteins. This provokes a "BRCAness" phenotype that results in deficiencies in DNA damage repair, promoting synergy with DNA-damaging chemotherapy and PARP inhibitors.