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.

Glioblastoma (GBM) is the most common and lethal malignant primary brain tumor. The standard treatment for GBM including surgical resection followed by radiation therapy and adjuvant chemotherapy with temozolomide remains unsatisfactory. In this study, we investigated the effects of the Aurora kinase inhibitor, TAK901, in GBM both in vitro and in vivo, and explored its key downstream targets. The effects of TAK901 were investigated using cell viability, cell apoptosis, live/dead, cell cycle, Transwell, 3D cell invasion, neuro-sphere, and self-renewal assays. Mechanistic studies were conducted using RNA-seq, lipid measurements, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western blotting. The in vivo efficacy of TAK901 was validated using orthotopic xenograft GBM mouse models. In both GBM cells and GSCs, TAK901 remarkably reduced cell viability, self-renewal, migration and invasion and induced apoptosis and cell cycle arrest. Treatment with TAK901 considerably inhibited GBM growth in vivo. RNA-seq and RT-qPCR analyses showed that TAK901 downregulated the expression and activation of SREBP1. Moreover, SREBP1 overexpression alleviated the TAK901-mediated suppression of cell viability and apoptosis in GBM cells. Our results provide evidence that TAK901 inhibits GBM growth by suppressing SREBP1-mediated lipid metabolism.

Glioblastoma is the most common malignant primary brain tumor. Molecular mechanisms underlying the pathobiology of glioblastoma are incompletely understood, emphasizing an unmet need for the identification of new therapeutic candidates. Reticulocalbin 3 (RCN3), an ER lumen-residing Ca²⁺ binding protein, plays an essential role in protein biosynthesis processes via the secretory pathway. Emerging studies demonstrated that RCN3 is a target for therapeutic intervention in various diseases. However, a knowledge gap exists about whether RCN3 plays a role in glioblastoma. Publicly available datasets suggest RCN3 is overexpressed in glioblastoma and portends poor survival rates. The knockdown or knockout of RCN3 using shRNA or CRISPR/Cas9 gRNA, respectively, significantly reduced proliferation, neurosphere formation, and self-renewal of GSCs. The RNA-seq studies showed downregulation of genes related to translation, ribosome, and cytokine signaling and upregulation of genes related to immune response, stem cell differentiation, and extracellular matrix (ECM) in RCN3 knockdown cells. Mechanistic studies using qRT-PCR showed decreased expression of ribosomal and increased expression of ER stress genes. Further, in silico analysis of glioblastoma patient datasets showed RCN3 expression correlated with the ribosome, ECM, and immune response pathway genes. Importantly, the knockdown of RCN3 using shRNA significantly enhanced the survival of tumor-bearing mice in orthotopic glioblastoma models. Our study suggests that RCN3 could be a potential target for the development of a therapeutic intervention in glioblastoma.