Ovarian cancer (OCa) is the deadliest gynecologic cancer. Emerging studies suggest ovarian cancer stem cells (OCSCs) contribute to chemotherapy resistance and tumor relapse. Recent studies demonstrated estrogen receptor beta (ERβ) exerts tumor suppressor functions in OCa. However, the status of ERβ expression in OCSCs and the therapeutic utility of the ERβ agonist LY500307 for targeting OCSCs remain unknown. OCSCs were enriched from ES2, OV90, SKOV3, OVSAHO, and A2780 cells using ALDEFLUOR kit. RT-qPCR results showed ERβ, particularly ERβ isoform 1, is highly expressed in OCSCs and that ERβ agonist LY500307 significantly reduced the viability of OCSCs. Treatment of OCSCs with LY500307 significantly reduced sphere formation, self-renewal, and invasion, while also promoting apoptosis and G2/M cell cycle arrest. Mechanistic studies using RNA-seq analysis demonstrated that LY500307 treatment resulted in modulation of pathways related to cell cycle and apoptosis. Western blot and RT-qPCR assays demonstrated the upregulation of apoptosis and cell cycle arrest genes such as FDXR, p21/CDKN1A, cleaved PARP, and caspase 3, and the downregulation of stemness markers SOX2, Oct4, and Nanog. Importantly, treatment of LY500307 significantly attenuated the tumor-initiating capacity of OCSCs in orthotopic OCa murine xenograft models. Our results demonstrate that ERβ agonist LY500307 is highly efficacious in reducing the stemness and promoting apoptosis of OCSCs and shows significant promise as a novel therapeutic agent in treating OCa.

Approaches targeting factors that simultaneously promote tumor growth and progression, induce therapy resistance, and inhibit antitumor immunity offer clear benefits over therapies targeting only one of these tumor-promoting processes. Through comprehensive loss-of-function genomic screening, we identified SCUBE3 as a pivotal factor that supports survival and therapy resistance and also orchestrates an immunosuppressive tumor microenvironment. Secretory SCUBE3 supported oncogenic activity through interactions with key oncogenic cell surface receptor proteins, including EGFR, mutant CALR, and TGFβRI/II. These interactions activated the transcription factors FOXR2 and c-Myc, promoting cancer cell proliferation and therapy resistance by enhancing DNA damage repair. Additionally, the SCUBE3–FOXR2 axis created an immunosuppressive tumor microenvironment by facilitating recruitment of the DNMT1 epigenetic repressor complex to the transcription regulator IRF1, thereby inhibiting the expression of MHC-I and MHC-II genes. A first-in-class neutralizing antibody targeting SCUBE3, which was developed using a sophisticated antibody discovery platform and engineered with specific mutations in the heavy chain for enhanced specificity and efficacy, demonstrated profound therapeutic potential across various cancer types in preclinical models, including patient-derived breast and ovarian cancer xenografts. This discovery marks an advancement toward developing a targeted therapy for cancers characterized by hyperactive SCUBE3-associated signaling pathways. Significance: Targeting SCUBE3 with a neutralizing antibody inhibits tumor growth and metastasis by blocking oncogenic signaling through FOXR2 and c-Myc and by circumventing immunosuppression, providing a promising pan-cancer treatment approach.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with limited effective treatments, partly because of its complex tumor microenvironment. In this study, we report discoidin domain receptor 2 (DDR2), a receptor tyrosine kinase, as a critical protein that promotes PDAC growth and survival. Our results reveal that DDR2 is highly expressed and its expression correlates with the worst survival outcome in patients with PDAC. Using an unbiased high-throughput screen of small-molecule inhibitor libraries, we identified CIDD-8633, a novel inhibitor targeting DDR2. Our study suggests that CIDD-8633 interacts with DDR2 and inhibits DDR2-associated signaling. Importantly, in vivo studies demonstrate that CIDD-8633 effectively blocks PDAC tumor growth in preclinical mouse models. Additionally, combining CIDD-8633 with gemcitabine enhanced its efficacy synergistically. Mechanistically, CIDD-8633 treatment induces pro-apoptotic genes in PDAC cells. These findings position DDR2 as a promising therapeutic target and CIDD-8633 as a potential DDR2 inhibitor, offering new avenues for the treatment of PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with limited effective treatments, partly because of its complex tumor microenvironment. In this study, we report discoidin domain receptor 2 (DDR2), a receptor tyrosine kinase, as a critical protein that promotes PDAC growth and survival. Our results reveal that DDR2 is highly expressed and its expression correlates with the worst survival outcome in patients with PDAC. Using an unbiased high-throughput screen of small-molecule inhibitor libraries, we identified CIDD-8633, a novel inhibitor targeting DDR2. Our study suggests that CIDD-8633 interacts with DDR2 and inhibits DDR2-associated signaling. Importantly, in vivo studies demonstrate that CIDD-8633 effectively blocks PDAC tumor growth in preclinical mouse models. Additionally, combining CIDD-8633 with gemcitabine enhanced its efficacy synergistically. Mechanistically, CIDD-8633 treatment induces pro-apoptotic genes in PDAC cells. These findings position DDR2 as a promising therapeutic target and CIDD-8633 as a potential DDR2 inhibitor, offering new avenues for the treatment of PDAC.