Tumor antigens: From discovery to vaccine

Abstract

Tumor specific antigens are the holy grails of cancer research. We made an attempt to identify novel tumor antigens by examining the tumor infiltrating B lymphocyte (TIL-B), and lymph node derived B cell (LN-B) population. TIL-B and LN-B cells were tested for reactivity against glutaraldehyde-fixed allogeneic cell lines by enzyme linked immunosorbant assay (ELISA). Of the 466 wells containing TIL-B cells, 29 (6.2%) of them produced antibodies that were reactive to allogeneic tumor cell lines. Of the 712 wells containing LN-B cells, 79 (11.1%) of them produced reactive antibodies to allogeneic tumor cell lines. Unfortunately, we were unable to identify specific clones producing those reactive antibodies by limiting dilution. Furthermore, we examined the murine immune response to a truncated p53 harboring four point mutations and fused to enhanced green fluorescent protein (EGFP). Balb/c mice were immunized with either plasmid DNA or the recombinant protein. We found that delivery by intramuscular injection of plasmid DNA encoding truncated, mutant p53 along with murine GM-CSF mice resulted in non-measurable antibody response and minimal cellular cytotoxic activity while recombinant protein immunization resulted in a strong antibody response and no measurable cytotoxic activity. We conclude that immunization with the fusion construct containing green fluorescent protein does not enhance cytotoxic responses to mutant p53. In addition, the creation of multiple point mutations in the p53 gene may have prevented the fusion protein from being processed and expressed on MHC class I molecules.