A novel therapeutic approach: Blocking Glioblastoma cells’ interaction with their microenvironment

Abstract Due to the highly invasive nature of Glioblastoma (GB), complete surgical resection is not feasible, while motile tumour cells are often associated with several specific brain structures that enhance treatment-resistance. Here, we investigate the therapeutic potential of Disulfiram and Carbenoxolone, that inhibit two distinct interactions between GB and the brain tissue microenvironment: stress-induced cell-matrix adhesion and gap junction mediated cell-cell communication, respectively. Increase in cell numbers of tumour-initiating cells, which are cultured in suspension as cell clusters, and adherent differentiated cells can be blocked to a similar extent by Carbenoxolone, as both cell populations form gap junctions, but the adherent differentiated cells are much more sensitive to Disulfiram treatment, which – via modulation of NF-κB signalling – interferes with cell-substrate adhesion. Interestingly, inducing adhesion in tumour-initiating cells without differentiating them does not sensitize for Disulfiram. Importantly, combining Disulfiram, Carbenoxolone and the standard chemotherapeutic drug Temozolomide reduces tumour size in an orthotopic mouse model. Isolating GB cells from their direct environment within the brain represents an important addition to current therapeutic approaches. The blockage of cellular interactions via the clinically relevant substances Disulfiram and Carbenoxolone, has distinct effects on different cell populations within a tumour, potentially reducing motility and/or resistance to apoptosis

Blockade of Gap Junction Hemichannel Suppresses Disease Progression in Mouse Models of Amyotrophic Lateral Sclerosis and Alzheimer's Disease

Glutamate released by activated microglia induces excitotoxic neuronal death, which likely contributes to non-cell autonomous neuronal death in neurodegenerative diseases, including amyotrophic lateral sclerosis and Alzheimer's disease. Although both blockade of glutamate receptors and inhibition of microglial activation are the therapeutic candidates for these neurodegenerative diseases, glutamate receptor blockers also perturbed physiological and essential glutamate signals, and inhibitors of microglial activation suppressed both neurotoxic/neuroprotective roles of microglia and hardly affected disease progression. We previously demonstrated that activated microglia release a large amount of glutamate specifically through gap junction hemichannel. Hence, blockade of gap junction hemichannel may be potentially beneficial in treatment of neurodegenerative diseases.In this study, we generated a novel blood-brain barrier permeable gap junction hemichannel blocker based on glycyrrhetinic acid. We found that pharmacologic blockade of gap junction hemichannel inhibited excessive glutamate release from activated microglia in vitro and in vivo without producing notable toxicity. Blocking gap junction hemichannel significantly suppressed neuronal loss of the spinal cord and extended survival in transgenic mice carrying human superoxide dismutase 1 with G93A or G37R mutation as an amyotrophic lateral sclerosis mouse model. Moreover, blockade of gap junction hemichannel also significantly improved memory impairments without altering amyloid β deposition in double transgenic mice expressing human amyloid precursor protein with K595N and M596L mutations and presenilin 1 with A264E mutation as an Alzheimer's disease mouse model.Our results suggest that gap junction hemichannel blockers may represent a new therapeutic strategy to target neurotoxic microglia specifically and prevent microglia-mediated neuronal death in various neurodegenerative diseases