Natural CD8 super(+) T-cell responses against MHC class I epitopes of the HER-2/neu oncoprotein in patients with epithelial tumors

• Published in: Cancer Immunology, Immunotherapy Immunotherapy, 2003-12, Vol.52 (12), p.771-779
• Main Authors: Sotiropoulou, P A, Perez, SA, Voelter, V, Echner, H, Missitzis, I, Tsavaris, N B, Papamichail, M, Baxevanis, C N
• Format: Article
• Language: English
• ISSN: 0340-7004
• DOI: 10.1007/s00262-003-0420-9

HER-2/neu is an immunogenic protein eliciting both humoral and cellular immune responses in patients with HER-2/neu-positive ( super(+)) tumors. Preexisting cytotoxic T lymphocyte (CTL) immunity to HER-2/neu has so far been mainly evaluated in terms of detection of CTL precursor (CTLp) frequencies to the immunogenic HLA-A2-binding nona-peptide 369-377 (HER-2(9 sub(369))). In the present study, we examined patients with HER-2/neu super(+) breast, ovarian, lung, colorectal, and prostate cancers for preexisting CTL immunity to four recently described HER-2/neu-derived and HLA-A2-restricted "cytotoxic" peptides and to a novel one spanning amino acids 777-785 also with HLA-A2-binding motif. We utilized enzyme-linked immunosorbent spot (ELISpot) assay, which allows a quantitative and functional assessment of T cells directed against specific peptides after only brief in vitro incubation. CTL reactivity was determined with an interferon gamma (IFN- gamma ) ELISpot assay detecting T cells at the single cell level secreting IFN- gamma . CTLp were defined as peptide-specific precursors per 10 super(6) peripheral blood mononuclear cells (PBMCs). Patients" PBMCs with increased CTLp were also tested against autologous tumor targets and peptide-pulsed dendritic cells (DCs) in cytotoxicity assays. We also studied patients with HER-2/neu-negative (") tumors and healthy individuals. Of the HER-2/neu super(+) patients examined, 31% had increased CTLp to HER-2(9 sub(952)), 19% to HER-2(9 sub(665)), 16% to HER-2(9 sub(689)), and 12.5% HER-2(9 sub(435)), whereas only 2 of 32 patients (6%) responded to HER-2(9 sub(777)). The CTLp recognizing HER-2(9 sub(952)) were extremely high in two patients with breast cancer, one with lung cancer, and one with prostate cancer. None of the HER-2/neu super(-) patients or healthy donors exhibited increased CTLp to any of these peptides. Besides IFN- gamma production, preexisting CTL immunity to all five HER-2/neu peptides was also shown in cytotoxicity assays where patients" PBMCs with increased CTLp specifically lysed autologous tumor targets and autologous peptide-pulsed DCs. Our results demonstrate for the first time that (1) preexisting immunity to peptides HER-2(9 sub(435)), HER-2(9 sub(952)), HER-2(9 sub(689)), HER-2(9 sub(665)), and HER-2(9 sub(777)) is present in patients with HER-2/neu super(+) tumors of distinct histology, (2) HER-2(9 sub(777)) is a naturally processed peptide expressed on the surface of HER-2/neu super(+) tumors, a