HIF1A and glioblastoma: Given that topotecan has been shown capable of modulating the SUMOylation status of its target DNA topoisomerase I25 and has recently been reported to have other non-canonical functions (e.g. the inhibition of hypoxia inducible factor-1 [HIF-1α])26, we sought to explore its ability to modulate global SUMOylation in GBM.