Figure 2: Defects in DNA mismatch repair genes leads to the generation of immunogenic Peptides expressed by the tumor. (a): The first sequence is a partial sequence of the TGF RII gene. Note the ten base stretch of adenines. The area of the gene is susceptible to strand slippage during replication. When DNA mismatch repair genes are mutated, base-pairs can be lost or added during DNA replication. Additions or deletions result in an altered reading frame. Using the TGF RII gene as an example, the amino acid sequence is shown on the right. Bolded animo acids are those amino acids represented by the nucleotide on the left. Unbolded sequences are those that are predicted based on the mutation, using the nucleotide sequence of TGF RII (120). (b): Following the generation of novel frameshift peptides to which the immune system has not developed central tolerance to, the host can generate a robust immune response to the peptides that are uniquely expressed by the tumor.