MKI67 and neoplasm: Compared to the vehicle group or the single treatment group with vorinostat and/or QC, the combined administration of the two drugs grouped to lower tumor cell proliferation, as assessed by Ki-67 staining, and a higher percentage of apoptotic cells as evidenced by the increase of terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells (Fig. 5c).