MKI67 and neoplasm: HDAC2 inhibition inhibited the proliferation of ESCC cells in the TRIB2‐high PDX group but failed to influence tumor growth in the TRIB2‐low PDX group as determined by IHC staining of Ki‐67, indicating the biological relevance of the TRIB2/HDAC2 axis in attenuating radiotherapy‐mediated growth suppression in ESCC (Figure 8C).