SLC9A9 and glioblastoma: Although the overexpression of NHE9 in glioblastoma and oesophageal squamous cell carcinoma has previously been shown to be involved in chemoresistance25, 26, in this study knockdown of NHE9 had no significant impact on endosome pH homeostasis, intracellular Dox partitioning or Dox resistance.