Monensin and its analogues show anti-glioblastoma activity in an organoid model of cancer.

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. Despite numerous clinical trials, the standard of care therapy has remained unchanged for the last decade. One of the main problems contributing to the limited effective treatment options and poor overall survival is the lack of models which can reliably recapitulate tumor heterogeneity. Organoids are 3D self-organized structures which mimic tumor architecture, microenvironment, and cellular interactions which makes them an improved model for anti-cancer drug discovery. Monensin (MON) is a polyether ionophore antibiotic characterized by wide range of biological properties including anti-cancer activity. In order to identify more potent compounds based on the scaffold of MON, we investigated the anti-GBM activity of 14 novel esters and urethanes of MON. In 3D mini-ring cell viability assays, we identified seven analogues (IC = 91.5 ± 54.4 - 291.7 ± 68.8 nM) more potent towards GBM than the parental MON (IC = 612.6 ± 184.4 nM). These analogues induced DNA fragmentation in an organoid model of GBM, suggestive of apoptotic cell death. Furthermore, the most potent analog, compound 1, significantly reduced GBM cell migration, induced PARP cleavage and degradation, increased ɣH2AX signaling and increased expression of the autophagy marker LCII. To investigate the activity of these novel compounds in a tumor microenvironment, we have developed a host:tumor hybrid 3D organoid system. For host tissue, we generated human cerebral organoids (COs) from hiPSCs. The COs displayed multiple neural rosettes with a proliferative zone of neural stem cells (Nestin+), neurons (TUJ1+), primitive ventricular system (SOX2+/Ki67+), intermediate zone (TBR2+) and cortical plate (MAP2+). These findings suggest the level of differentiation and development of our COs as equivalent to early stage human fetal brain. We then co-cultured RFP-labeled U87MG cells with fully formed COs. After establishing U87MG tumor formation, hybrid organoids were treated with MON or compound 1. Compound 1 significantly reduced U87MG tumor size after four days of treatment. Our findings highlight the therapeutic potential of MON analogues towards GBM and support further research and clinical development of these compounds.