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

Glioblastoma (GBM) is the most common primary brain tumor and among the most lethal cancers. Due to its highly invasive nature, complete surgical resection is not feasible, while motile tumor cells are often associated with brain structures that enhance treatment-resistance. Here, we investigate the therapeutic potential of two substances, Disulfiram and Carbenoxolone that inhibit different cellular interactions of GBM, stress-induced cell-matrix and gap junction mediated cell-cell adhesion, respectively. To this extend we used genetically identical pairs of primary cell populations that, due to their contrasting differentiation status, exhibit different dominant forms of cellular interaction. Increase in cell numbers of tumor-initiating cells, which are cultured in suspension as neurospheres, and adherent differentiated cells can be blocked to 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 signaling – interferes with cell-substrate adhesion. Interestingly, inducing adhesion in tumor-initiating cells without differentiating them does not sensitize for Disulfiram. Importantly, Disulfiram, Carbenoxolone and the standard chemotherapeutic drug Temozolomide do not interact antagonistic, making them ideal partners for combination therapy. In addition, combining these three substances reduces tumor size in an orthotrophic mouse model. While an independent line of investigation clearly establishes that high expression of the major putative targets of Disulfiram and Carbenoxolone, members of the NF-κB signaling complex and connexins, respectively, is associated with reduced disease-free and overall survival. Therefore, we postulate that the addition of the well-established drugs Disulfiram and Carbenoxolone to the treatment regime for GBM will be of considerable benefit for the patients.