PSMB9 and esophageal squamous cell carcinoma: In the present study, although the expressions of TAP-1, LMP-7, and tapasin were downregulated or lost in HER2 high-expressing TE4 in comparison to HER2 low-expressing TE1, we could not detect significant alterations in the expressions of LMP2, LMP7, Tap1, and tapasin between ESCC treated with HER2-siRNA and the control.