Testing of T-cell based cancer therapeutics often involves measuring cancer antigen-specific T-cell populations with the assumption that they arise from in vivo clonal expansion. This analysis, using peptide/MHC tetramers, is often ambiguous. From a leukemia cell line, we identified a CDK4-derived peptide epitope, UNC-CDK4-1 (ALTPVVVTL) that bound HLA-A*02:01 with high affinity and could induce CD8+ T-cell responses in vitro. We identified UNC-CDK4-1/HLA-A*02:01 tetramer+ populations in 3 of 6 acute myeloid leukemia patients who had undergone allogeneic stem cell transplant (SCT). Using tetramer-based, single cell sorting and T-cell receptor β (TCRβ) sequencing we identified recurrent UNC-CDK4-1 tetramer-associated TCRβ clonotypes in a patient with a UNC-CDK4-1 tetramer+ population, suggesting in vivo T-cell expansion to UNC-CDK4-1. In parallel, we measured the patient's TCRβ repertoire and found it to be highly restricted / oligoclonal. The UNC-CDK4-1 tetramer-associated TCRβ clonotypes represented >17% of the entire TCRβ repertoire - far in excess of the UNC-CDK4-1 tetramer+ frequency, indicating that the recurrent TCRβ clonotypes identified from UNC-CDK-4-1 tetramer+ cells were likely a consequence of the extremely constrained T-cell repertoire in the patient and not in vivo UNC-CDK4-1-driven clonal T-cell expansion. Mapping recurrent TCRβ clonotype sequences onto TCRβ repertoires can help confirm or refute antigen-specific T-cell expansion in vivo.
- Received January 7, 2014.
- Revision received December 15, 2014.
- Accepted December 29, 2014.
- Copyright © 2015, American Association for Cancer Research.