Disease recurrence is the major cause of morbidity and mortality of ovarian cancer (OC). In terms of maintenance therapies after platinum-based chemotherapy, PARP inhibitors significantly improve the overall survival of patients with BRCA mutations but is of little benefit to patients without homologous recombination deficiency (HRD). The stem-like tumor-initiating cell (TIC) population within OC tumors are thought to contribute to disease recurrence and chemoresistance. Therefore, there is a need to identify drugs that target TICs to prevent relapse in OC without HRD. RNA sequencing analysis of OC cells grown in TIC conditions revealed a strong enrichment of genes involved in drug metabolism, oxidative phosphorylation and reactive oxygen species (ROS) pathways. Concurrently, a high-throughput drug screen identified drugs that showed efficacy against OC cells grown as TICs compared to adherent cells. Four drugs were chosen that affected drug metabolism and ROS response: disulfiram, bardoxolone methyl, elesclomol and salinomycin. The drugs were tested in vitro for effects on viability, sphere formation and markers of stemness CD133 and ALDH in TICs compared to adherent cells. The compounds promoted ROS accumulation and oxidative stress and disulfiram, elesclomol and salinomycin increased cell death following carboplatin treatment compared to carboplatin alone. Disulfiram and salinomycin were effective in a post-surgery, post-chemotherapy OC relapse model in vivo, demonstrating that enhancing oxidative stress in TICs can prevent OC recurrence.

Osteosarcoma is the most common malignant bone tumor in young patients and remains a significant clinical challenge, particularly at the metastatic stage. Studies detailing the immunosuppressive mechanisms within the metastatic osteosarcoma microenvironment are needed to elucidate the cellular communities in the metastatic microenvironment that support metastatic growth and to identify therapeutic approaches to target the cross-talk between cancer cells and their microenvironment. In this study, we performed spatial transcriptional profiling on a cohort of osteosarcoma pulmonary metastases from pediatric patients. The data revealed a conserved spatial gene expression pattern resembling a foreign body granuloma, characterized by peripheral inflammatory signaling, fibrocollagenous encapsulation, lymphocyte exclusion, and peritumoral macrophage accumulation. The intratumoral microenvironment of these lesions, however, lacked inflammatory signaling. Exploration of spatially distinct drug–gene interactions identified the CXCR4 signaling axis, which displayed spatial heterogeneity and complexity, as a potential therapeutic target that bridges both the intra- and extratumoral microenvironments. Collectively, this study reveals that metastatic osteosarcoma comprises multiple regionally distinct immunosuppressive microenvironments. Significance: Exploration of spatially resolved microenvironments in metastatic osteosarcoma tissues reveals how the tissue architecture promotes immunosuppression and identifies actionable processes to enhance immunotherapy efficacy.

Epithelial ovarian cancer (EOC) remains the fifth leading cause of cancer-related death in women worldwide, partly due to the survival of chemoresistant, stem-like tumor-initiating cells (TICs) that promote disease relapse. We previously described a role for the NF-κB pathway in promoting TIC chemoresistance and survival through NF-κB transcription factors (TFs) RelA and RelB, which regulate genes important for the inflammatory response and those associated with cancer, including microRNAs (miRNAs). We hypothesized that NF-κB signaling differentially regulates miRNA expression through RelA and RelB to support TIC persistence. Inducible shRNA was stably expressed in OV90 cells to knockdown RELA or RELB; miR-seq analyses identified differentially expressed miRNAs hsa-miR-452-5p and hsa-miR-335-5p in cells grown in TIC versus adherent conditions. We validated the miR-seq findings via qPCR in TIC or adherent conditions with RELA or RELB knocked-down. We confirmed decreased expression of hsa-miR-452-5p when either RELA or RELB were depleted and increased expression of hsa-miR-335-5p when RELA was depleted. Either inhibiting miR-452-5p or mimicking miR-335-5p functionally decreased the stem-like potential of the TICs. These results highlight a novel role of NF-κB TFs in modulating miRNA expression in EOC cells, thus opening a better understanding toward preventing recurrence of EOC.

High-grade serous ovarian cancer (HGSOC) often relapses after chemotherapy due to chemoresistant cancer stem-like cells (CSCs). NF-κB signaling, previously shown to enhance stemness traits, was investigated for its role in post-treatment tumor regrowth. Here, we found that NF-κB subunits RelA and RelB jointly regulate extracellular matrix genes but differentially control integrin subunits: RelA regulates ITGAV (αV) and RelB regulates ITGB3 (β3). Integrin αVβ3 expression is upregulated on CSCs, and this is partially driven by NF-κB activation. In vivo models demonstrate that αVβ3⁺ cells have higher tumor-initiating capacity and comprise over 90% of cells from relapsed tumors. Cells expressing RelB and αVβ3 preferentially grow on mesentery at relapse. Targeting this pathway, combined RelB knockdown and inhibition of αVβ3 eliminated stress-tolerant CSCs, reduced tumor burden, and extended survival. These findings highlight integrins as promising therapeutic targets and reveal distinct roles for NF-κB subunits in regulating metastasis and relapse in HGSOC.

Distribution and abundance of genes encoding functional and phenotypic macrophage markers. Clustered dot plots illustrating the spatial distribution of gene encoding different functional and phenotypic macrophage markers within each individual metastatic osteosarcoma specimen. The color bar above each dot plot corresponds to the different spatial clusters displayed on the adjoining spatial cluster maps that are shown for reference (above). Separate color palettes denote the independent clustering analysis of each specimen. Spatial clusters were localized to the extratumoral (black) or intratumoral (gray) microenvironments as depicted in the second color bar.