CTAG2 and esophageal cancer: First, MAGE-A, NY-ESO-1, LAGE-1, and TTK are not expressed in all esophageal cancer patients as described above; second, whether the expression of these antigens in esophageal cancer patients can trigger an effective immune response to eliminate tumor cells; third, whether there are more effective peptides for MAGE-A, NY-ESO-1, LAGE-1 and TTK that can stimulate sufficient immune responses.