High frequency of prostate antigen-directed T cells in cancer patients compared to healthy age-matched individuals

• BACKGROUND. In order to obtain a sustained cytotoxic T lymphocyte (CTL) response against cancer cells it is preferable to have CTLs directed against multiple peptide epitopes from numerous tumor-associated antigens. METHODS. We used a flow cytometry-based interferon (IFN)-g secretion assay to analyze whether CD8+ T cells directed against any of 24 HLA-A*0201-binding peptides from 15 prostate-associated proteins can be found in the peripheral blood of patients with localized prostate cancer. We also investigated whether multiple prostate antigen-specific CD8+ T cells can be generated simultaneously, from a naïve T cell repertoire. In that case, dendritic cells (DCs) from peripheral blood of healthy donors were divided in six portions and separately pulsed with six peptides. The peptide-pulsed DCs were then pooled and used to stimulate autologous T cells. The T cells were re-stimulated with peptide-pulsed monocytes. RESULTS. We found prostate antigen-restricted CD8+ T cells in the peripheral blood in 48 out of 184 (26.1%) analyzed samples from 25 cancer patients. This is significantly higher than 17 out of 214 analyzed samples (7.9%) from 10 healthy age-matched male individuals (p = 0.0249). In the cases when antigen-specific T cells could not be detected, we were able to generate IFN-g-producing CD8+ T cells specific for up to three prostate antigens simultaneously from a naïve T cell repertoire. CONCLUSIONS. CD8+ T cells directed against prostate antigen peptides can be found in, or generated from, peripheral blood. This indicates that such T cells could be expanded ex vivo for adoptive transfer to prostate cancer patients.

Nyckelord

prostate cancer

T cell

dendritic cell

HLA-A2 peptides

MEDICINE

MEDICIN

Klinisk immunologi

Clinical Immunology

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