MKI67 and cancer: In these studies, leveraging the CT26 tumor model, mCD38-mAtt treatment enhanced CD8 T-cell proliferation (as assessed by percentage of positivity of the proliferation marker Ki67 on tumor CD8 T cells; Fig 6A) 7 days post treatment, which coincided with a concomitant increase in the tumor CD8 T cell to Treg ratio (Fig 6B), a positive prognostic indicator in many human cancers [20–22].