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Volume 3 Supplement 2

30th Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2015)

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Selection of circulating PD-1+ lymphocytes from cancer patients enriches for tumor-reactive and mutation-specific lymphocytes


T cells targeting unique somatic mutations appear to play an important role in the antitumor responses observed following T cell transfer, and isolation of mutation-specific lymphocytes and T-cell receptors has become a major obstacle to the development of more effective immunotherapies. The detection of tumor-reactive and mutation-specific cells in patients with cancer has been largely restricted to tumor-infiltrating lymphocytes, but mutation-specific cells are thought to be far less prevalent in peripheral blood, a more accessible and abundant source of T cells. We recently reported that expression of PD-1 identifies the patient-specific repertoire of tumor-reactive cells infiltrating melanoma tumors. Given these findings, we explored the utility of PD-1 expression on peripheral blood lymphocytes to detect and enrich for tumor and neoantigen specific lymphocytes.


To this end, peripheral blood CD8+ lymphocytes were separated based on the expression of PD-1 into CD8+PD-1- and CD8+PD-1+ and CD8+PD-1hi cells, and expanded in vitro for 15 days. Circulating T cell subsets were subsequently screened for recognition of mutated antigens identified by whole exome sequencing using a high throughput and personalized approach that enables the expression of all the potential tumor neoantigens in the autologous antigen-presenting cells. In addition, recognition of shared melanoma differentiation antigens and cancer germline antigens was also evaluated.


PD-1+ lymphocytes represented a small percentage of all the circulating CD8+ cells in patients with metastatic melanoma. We found that selection of CD8+PD-1+ lymphocytes circulating in peripheral blood, but not the CD8+ or CD8+PD-1- cells, led to direct enrichment of tumor-reactive cells from peripheral blood in all four patients studied. In three out of four melanoma patients, the peripheral blood CD8+PD-1+ and PD-1hi cells contained mutation-specific lymphocytes targeting 3, 3 and 1 unique patient-specific neoantigens, respectively. In addition, circulating CD8+PD- 1+ and PD-1hi lymphocytes from all four patients evaluated were also enriched in T cells targeting at least one cancer germline antigen, including NY-ESO-I, MAGE-A3, and SSX2. Neither mutation-specific nor cancer germline-specific lymphocytes were detected in the peripheral blood CD8+ or the CD8+PD-1- populations.


Our findings provide evidence that peripheral blood CD8+PD-1+ from cancer patients are enriched in naturally-occurring tumor-reactive and mutation-specific cells and provide a novel strategy to develop personalized T cell based therapies to treat cancer.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Gros, A., Tran, E., Parkhurst, M.R. et al. Selection of circulating PD-1+ lymphocytes from cancer patients enriches for tumor-reactive and mutation-specific lymphocytes. j. immunotherapy cancer 3 (Suppl 2), O2 (2015).

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