Small-molecule inhibitors of PD-L1 are postulated to control immune evasion in tumors similar to antibodies that target the PD-L1/PD-1 immune checkpoint axis. However, the identity of targetable PD-L1 inducers is required to develop small-molecule PD-L1 inhibitors. In this study, using chromatin immunoprecipitation (ChIP) assay and siRNA, we demonstrate that vitamin D/VDR regulates PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells. We have examined whether a VDR antagonist, MeTC7, can inhibit PD-L1. To ensure that MeTC7 inhibits VDR/PD-L1 without off-target effects, we examined competitive inhibition of VDR by MeTC7, utilizing ligand-dependent dimerization of VDR-RXR, RXR-RXR, and VDR-coactivators in a mammalian 2-hybrid (M2H) assay. MeTC7 inhibits VDR selectively, suppresses PD-L1 expression sparing PD-L2, and inhibits the cell viability, clonogenicity, and xenograft growth of AML cells. MeTC7 blocks AML/mesenchymal stem cells (MSCs) adhesion and increases the efferocytotic efficiency of THP-1 AML cells. Additionally, utilizing a syngeneic colorectal cancer model in which VDR/PD-L1 co-upregulation occurs in vivo under radiation therapy (RT), MeTC7 inhibits PD-L1 and enhances intra-tumoral CD8⁺T cells expressing lymphoid activation antigen-CD69. Taken together, MeTC7 is a promising small-molecule inhibitor of PD-L1 with clinical potential.

Advanced clear cell ovarian cancer (CCOC) is a highly fatal malignancy with a scarcity of effective treatment options. CCOC is inherently chemotherapy resistance, but the exact mechanism of this resistance has yet to be established. Prosurvival signaling, such as through the MAPK cascade, is one way in which cancer cells can evade chemotherapy. We have determined that CCOC exhibits baseline elevated levels of MAPK activity, which increase further upon cisplatin exposure. We have developed a novel MEK inhibitor, URML-3881, to test the effect of MAPK inhibition in CCOC. URML-3881 was found to reduce in vitro CCOC viability through apoptosis and proliferation inhibition, yet it failed to induce in vivo tumor regression. Similarly, cisplatin alone had minimal impact on tumor growth, but remarkably, the combination of MEK inhibition and cisplatin led to a significant and prolonged tumor regression. These studies confirm that the combination of MEK inhibition with URML-3881 and cisplatin is superior to either agent alone in CCOC. Our data support the design of future preclinical and clinical studies into the combination of MEK inhibition and platinum-based chemotherapy as a treatment strategy for CCOC.

Forchlorfenuron (FCF) is a widely used plant cytokinin that enhances fruit quality and size in agriculture. It also serves as a crucial pharmacological tool for the inhibition of septins. However, the precise target of FCF has not yet been fully determined. This study reveals a novel target of FCF and elucidates its downstream signaling events. FCF significantly impairs mitochondrial respiration and mediates metabolic shift toward glycolysis, thus making cells more vulnerable to glycolysis inhibition. Interestingly, FCF’s impact on mitochondrial function persists, even in cells lacking septins. Furthermore, the impaired mitochondrial function leads to the degradation of HIF-1α, facilitated by increased cellular oxygen. FCF also induces AMPK activation, suppresses Erk1/2 phosphorylation, and reduces the expression of HER2, β-catenin, and PD-L1. Endometrial cancer is characterized by metabolic disorders such as diabetes and aberrant HER2/Ras-Erk1/2/β-catenin signaling. Thus, FCF may hold promise as a potential therapeutic in endometrial cancer.

Inflammation-driven tumor implantation, such as port-site metastasis (PSM) following laparoscopic gynecologic surgery and peritoneal seeding during post-surgical recurrence, represents an aggressive clinical problem that remains poorly understood and lacks targeted therapies. To address this, we developed a non-surgical Mesothelium-Inflammation/Injury-Metastasis (MIM) model and investigated the role of the IL-1β/IL1R1/MYD88/IRAK1/4 axis and NLRP3 in epithelial ovarian cancer (EOC) seeding at inflamed or injured sites. This model created by a needle injury recapitulates inflammation-driven peritoneal seeding and mimics PSM and inflammation associated dissemination in peritoneum during recurrence. Seeding was dependent on Il1r1 but not Nlrp3, despite its role in regulating IL-1β production, as Il1ra⁻/⁻ and Nlrp3⁻/⁻ mice phenocopied wild-type C57BL/6 mice. Given the limited antitumor efficacy of IL-1β–targeting agents such as Anakinra and Canakinumab, we focused on IRAK4 as a therapeutic target. IRAK4 knockdown significantly prolonged survival, reduced tumor cell adhesion, downregulated E-cadherin and Wnt4, and induced S-phase/mitotic arrest. This led to the development of UR241-2, a small-molecule IRAK4 inhibitor, which was validated through molecular simulations, hotspot analysis, nanoBRET, global kinome profiling, and NF-κβ reporter assays. UR241-2 inhibited NF-κβ nuclear translocation and blocked IL-1β–induced IRAK4 phosphorylation. UR241-2 exhibited favorable drug-like properties, including absence of CYP or hERG inhibition, and acceptable CaCo-2 permeability, plasma protein binding, microsomal stability, and pharmacokinetics. In vivo, UR241-2 reduced SKOV3 xenograft growth, suppressed mesothelial seeding, and increased MHC-II⁺ macrophages and activated neutrophils in syngeneic high-grade epithelial ovarian HGS3 tumors. RNA-seq revealed enrichment of neutrophil activation signatures and suppression of extracellular matrix (ECM) gene programs. Together, these findings establish a role for the IL-1β/IL1R1/IRAK4 axis in inflammation-driven PSM and peritoneal seeding and ECM regulation in EOC, and demonstrate that IRAK4 inhibition activates antitumor immune responses, providing a therapeutic strategy to block metastatic seeding and improve tumor control.