PIKFYVE and cancer: To evaluate whether the action of PIKfyve inhibitors was on-target, we treated Pikfyve-wild-type or Pikfyve-null cancer cells with apilimod or ESK981 and found that upregulation of MHC-I surface expression by PIKfyve inhibition was only observed in the wild-type cells but not Pikfyve-null cells (Fig. 1F).