Eoff, R. L. | Search bioRxiv

bioRxiv2025

Monensin and Its Analogs Exhibit Activity Against Breast Cancer Stem-Like Cells in an Organoid Model

Monensin (MON) is a polyether ionophore antibiotic of natural origin and is an FDA-approved drug for veterinary use. Recent studies have highlighted its potential anti-cancer activity in various in vitro and in vivo models. In this study, we evaluated the anti-breast cancer activity of MON and 37 synthetic analog compounds using cell monolayer and organoid models. Through a mini-ring cell viability assay, several compounds were identified that were more potent and selective against breast cancer cells compared to non-cancerous cells, surpassing the activity of parent MON. MON and these compounds induced significant DNA fragmentation, reduced cell migration, and downregulated SOX2 expression. Furthermore, MON and the most potent analog, compound 12, reduced the percentage of CD44+/CD24-/low stem-like cells and diminished cell self-renewal properties. Proteomics analyses revealed that several pathways, including extracellular matrix organization, were significantly dysregulated by MON and compound 12 in breast cancer cells. Among these, TIMP2, a protein associated with the suppression of tumor growth and metastasis, was identified as one of the most prominently upregulated proteins by MON and compound 12 in MDA-MB-231 cells. This finding was also validated in other breast cancer and melanoma cell lines. To simulate breast cancer metastasis to the brain, a human Hybrid Organoid System: Tumor in Brain Organoid (HOSTBO) model was developed. MON and compound 12 significantly reduced Ki-67 expression within the HOSTBOs, and compound 12 significantly downregulated SOX2 expression. Collectively, MON and compound 12 significantly reduced the proliferation of breast cancer stem-like cells in the organoid models, inhibited their migration, and dysregulated markers associated with stemness, demonstrating their potential as anti-metastatic agents and warranting further clinical development. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/663311v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@388862org.highwire.dtl.DTLVardef@182072dorg.highwire.dtl.DTLVardef@1a55072org.highwire.dtl.DTLVardef@447150_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2020

Inhibition of tryptophan-2,3-dioxygenase impairs DNA damage tolerance and repair in glioma cells

Aberrant expression of tryptophan 2,3-dioxygenase (TDO) is a determinant of malignancy and immune response in gliomas in part through kynurenine (KYN)-mediated activation of the aryl hydrocarbon receptor (AhR). In the current study, we investigated the hypothesis that TDO activation in gliomas has a broad impact upon genome maintenance - promoting tolerance of replication stress (RS) and repair of DNA damage. We report that inhibition of TDO activity attenuated recovery from hydroxyurea (HU)-induced RS and increased the genotoxic effects of bis-chloroethylnitrosourea (BCNU), as fork progress was impeded when TDO-deficient glioma cells were treated with BCNU. Activation of the Chk1 arm of the replication stress response (RSR) was reduced when TDO activity was blocked prior to treatment with BCNU, whereas phosphorylation of serine 33 (pS33) on replication protein A (RPA) was enhanced - indicative of increased fork collapse. Restoration of KYN levels protected against some replication-associated effects of BCNU. Inhibition of TDO activity had a strong anti-proliferative effect on glioma-derived cells - enhancing the cytotoxic effects of BCNU. Analysis of results obtained using quantitative proteomics revealed TDO-dependent changes in several signaling pathways - including down-regulation of DNA repair factors and sirtuin signaling. Consistent with these observations, inhibition of TDO diminished SIRT7 recruitment to chromatin, which increased histone H3K18 acetylation - a key mark involved in 53BP1 recruitment to sites of DNA damage. Cells lacking TDO activity exhibited defective recruitment of 53BP1 to gH2AX foci, which corresponded with delayed repair of BCNU-induced DNA breaks. Addition of exogenous KYN increased the rate of break repair. The discovery that TDO activity modulates sensitivity to DNA damage by fueling SIRT7/53BP1 localization to chromatin and repair of BCNU-induced DNA damage highlights the potential for tumor-specific metabolic changes to influence genome stability and may have implications for glioma biology and treatment strategies.

cancer biology↗