Identification and structural characterization of a mutant KRAS-G12V specific TCR restricted by HLA-A3
Malcolm J W Sim1,2, Ken-Ichi Hanada3, Zachary Stotz1
1Division of Intramural Research (DIR), Laboratory of Immunogenetics, NIAID, NIH, Bethesda, Maryland, USA.
Abstract:
Mutations in KRAS are some of the most common across multiple cancer types and are thus attractive targets for therapy. Recent studies demonstrated that mutant KRAS generates immunogenic neoantigens that are targetable by adoptive T-cell therapy in metastatic diseases. To expand mutant KRAS-specific immunotherapies, it is critical to identify additional HLA-I allotypes that can present KRAS neoantigens and their cognate T-cell receptors (TCR). Here, we identified a murine TCR specific to a KRAS-G12V neoantigen (7VVVGAVGVGK16) using a vaccination approach with transgenic mice expressing HLA-A*03:01 (HLA-A3). This TCR demonstrated exquisite specificity for mutant G12V and not WT KRAS peptides. To investigate the molecular basis for neoantigen recognition by this TCR, we determined its structure in complex with HLA-A3(G12V). G12V-TCR CDR3β and CDR1β formed a hydrophobic pocket to interact with p6 Val of the G12V but not the WT KRAS peptide. To improve the tumor sensitivity of this TCR, we designed rational substitutions to improve TCR:HLA-A3 contacts. Two substitutions exhibited modest improvements in TCR binding avidity to HLA-A3 (G12V) but did not sufficiently improve T-cell sensitivity for further clinical development. Our study provides mechanistic insight into how TCRs detect neoantigens and reveals the challenges in targeting KRAS-G12V mutations.
Insights
Researchers identified a T-cell receptor (TCR) targeting KRAS-G12V mutations, a common cancer driver. While specific, this TCR showed limited effectiveness for clinical use, highlighting challenges in developing KRAS-targeted immunotherapies.
Area of Science:
- Oncology
- Immunology
- Structural Biology
Background:
- KRAS mutations are prevalent in many cancers, making them key therapeutic targets.
- Mutant KRAS proteins can generate neoantigens, which are recognized by the immune system and can be targeted by T-cell therapies.
- Identifying T-cell receptors (TCRs) that recognize KRAS neoantigens presented by specific HLA-I allotypes is crucial for advancing KRAS-specific immunotherapies.
Purpose of the Study:
- To identify and characterize a T-cell receptor (TCR) specific for a KRAS-G12V neoantigen presented by HLA-A*03:01 (HLA-A3).
- To elucidate the structural basis of the TCR-neoantigen interaction.
- To explore strategies for enhancing TCR efficacy for potential clinical application.
Main Methods:
- Generated a murine TCR specific to a KRAS-G12V neoantigen using transgenic mice expressing HLA-A3.
- Determined the crystal structure of the TCR in complex with the HLA-A3/KRAS-G12V neoantigen.
- Performed structural analysis to understand the molecular interactions between the TCR and the neoantigen.
- Engineered TCR variants with substitutions to improve binding avidity and T-cell sensitivity.
Main Results:
- A murine TCR specific for the KRAS-G12V neoantigen (but not wild-type KRAS) presented by HLA-A3 was identified.
- Structural analysis revealed that specific TCR regions (CDR3β and CDR1β) form a hydrophobic pocket interacting with the G12V mutation.
- Rational TCR modifications showed modest improvements in binding avidity but insufficient enhancement in T-cell sensitivity for clinical development.
Conclusions:
- The study provides mechanistic insights into TCR recognition of KRAS neoantigens.
- Targeting KRAS-G12V mutations with TCRs presents significant challenges, particularly in achieving sufficient T-cell sensitivity for effective immunotherapy.
- Further research is needed to overcome these limitations for developing effective KRAS-targeted cancer immunotherapies.
