Related Experiment Videos
Overlapping epitopes encompassing a point mutation (12 Gly-->Arg) in p21 ras can be recognized by HLA-DR, -DP and -DQ
B Fossum1, T Gedde-Dahl, T Hansen
1Institute of Transplantation Immunology, National Hospital, Oslo, Norway.
Abstract:
Mutations in ras genes which result in transforming gene products carrying amino acid substitutions in position 12, 13 or 61 are common in human cancer. Peptides encompassing these mutations in ras are shown to be immunogenic in both mice and humans. The potential usefulness of such peptides in cancer therapy, depends on their ability to bind to HLA molecules. We therefore stimulated T cells from healthy donors with mutated ras-derived peptides. By repeated in vitro stimulation of peripheral blood mononuclear cells, several T cells clones could be generated which recognized a p21 ras derived peptide carrying a position 12 Gly-->Arg substitution. This peptide (1-25,12 Arg) could be specifically recognized by T cells restricted by either HLA-DQ7 or -DP3. Previously, we showed that this peptide is also recognized by a T cell clone restricted by HLA-DR2. The core region of the peptide was determined to span positions 9-16 for all three HLA restriction elements, and accordingly contains the mutational hot spots in position 12 and 13. The observation that the mutant 1-25,12 Arg ras-derived peptide may contain a promiscuous epitope encompassing the Gly-->Arg mutation in position 12 indicates that lack of peptide presentation by given HLA molecules may not be a major constraint in responsiveness against ras mutations.
Insights
Mutated ras peptides are immunogenic in cancer patients. These mutated ras peptides can be recognized by T cells restricted by multiple HLA types, suggesting broad therapeutic potential for cancer immunotherapy.
Area of Science:
- Oncology
- Immunology
- Molecular Biology
Background:
- Mutations in ras genes (e.g., at positions 12, 13, or 61) are frequent in human cancers.
- Ras peptides with these mutations are immunogenic, showing potential for cancer therapy.
- Therapeutic efficacy depends on the ability of these mutated peptides to bind to Human Leukocyte Antigen (HLA) molecules.
Purpose of the Study:
- To investigate the T cell response to mutated ras-derived peptides.
- To determine if mutated ras peptides can be presented by various HLA molecules for T cell recognition.
Main Methods:
- Stimulation of T cells from healthy donors using mutated ras-derived peptides.
- Generation of T cell clones through in vitro stimulation of peripheral blood mononuclear cells.
- Identification of HLA restriction elements for T cell recognition of specific mutated ras peptides.
Main Results:
- Several T cell clones were generated that recognized a p21 ras peptide with a Glycine to Arginine substitution at position 12 (1-25,12 Arg).
- This mutated peptide was specifically recognized by T cells restricted by HLA-DQ7 and HLA-DP3, and previously shown to be recognized by T cells restricted by HLA-DR2.
- The core recognition region of the peptide spans positions 9-16, encompassing the mutation sites.
Conclusions:
- The mutant 1-25,12 Arg ras-derived peptide contains a promiscuous epitope associated with the Gly-->Arg mutation at position 12.
- The broad HLA restriction suggests that peptide presentation by HLA molecules may not be a significant limitation for immune responses against ras mutations in cancer therapy.