Characterisation of the anti-migratory activity of the 6-bromoindirubin-3’oxime (BIO) derivative VTIND42 in patient-derived GBM subpopulations

Introduction Targeting the infiltrative nature of GBMs with anti-migratory drugs as combination treatment for prevention of tumour recurrence is an attractive disease management option. One such class of drugs are the GSK-3 inhibitors 6-bromoindirubin-3′-oximes (BIO). BIO has been proposed for use in combination therapy, however, the administration of indirubins remains problematic due to low solubility causing low bioavailability. We describe the characterisation of a BIO derivative, VTIND42, identified from a screen of 450 compounds with improved solubility. Method The compounds were initially screened on the following criteria, selective anti-migratory effect with enhanced potency over the lead compound BIO. Effect on cell migration in two cell subpopulations (core obtained, edge obtained) from the patient derived GBM40 was assessed by 3D migration/invasion assays and for cytoskeletal rearrangements by immunofluorescence. Results VTIND42 (1 µM) showed the best performance overall in terms of specificity and efficacy in comparison to BIO with a pronounced effect on GBM40 edge cell populations. Anti-migratory effects over 72 hours in GBM40 edge (24h, 10.74% p=0.04; 48h, 6.52% p=0.06, 72h, 4.26% p=0.06) in comparison to the control were observed; BIO (5 µM) significantly reduced migration over 72 hours (24h, 12.79% p<0.001; 48h 5.43% p<0.001; 72h 4.26% p<0.001). Immunofluorescence assays revealed cytoskeletal rearrangements; cells treated with VTIND42 showed an increased ratio of cells with stress fibres to cortical fibres and elongated cells. Discussion VTIND42 displayed increased efficacy in comparison to BIO, further investigations will determine its potential as a bioavailable anti-migratory drug for glioblastoma treatment potentially improving disease outcome in patients.