Tumor antigens are the primary target of therapeutic
cancer vaccines. We set out to define and compare the expression
pattern of tumor antigen genes in esophagus carcinoma biopsies and
in an allogeneic tumor lysate-based cancer vaccine, MelCancerVac®.
Cells used for vaccine production were treated with the DNA methyltransferase
inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR) to determine whether
this treatment could improve the profile of tumor antigen genes
expressed in these cells. In addition, the presence of MAGE-A tumor
antigen protein was evaluated in the purified tumor cell lysate
used in the production of the vaccine. Quantitative PCR was used
to assay 74 tumor antigen genes in patients with squamous cell carcinoma
of the esophagus. 81% (13/16) of tumors expressed more
than five cancer/testis (CT) antigens. A total of 96 genes
were assayed in the tumor cell clone (DDM1.7) used to make tumor
cell lysate for vaccine preparation. Gene expression in DDM1.7 cells
was compared with three normal tissues; 16 tumor antigen genes were induced
more than ten-fold relative to normal tissues. Treatment with 5-aza-CdR
induced expression of an additional 15 tumor antigens to a total
of 31. MAGE-A protein was detected in cell lysate by Western blot
at an estimated concentration of 0.2 µg/ml or
0.01% of the total protein