Naturally occurring peptides associated with HLA-A2 in ovarian cancer cell lines identified by mass spectrometry are targets of HLA-A2-restricted cytotoxic T cells

Abstract

Identifying naturally occurring peptides bound to HLA class I molecules recognized by HLA-restricted cytotoxic T lymphocytes (CTL) is both relevant and central to the development of effective immunotherapeutic strategies against cancer. Several cancer-related genes have been reported for ovarian cancer, but very few are known to be naturally processed T cell epitopes. In the present study we used mass spectrometry to identify 16 novel HLA-A2-bound peptides from HLA-A2(+) ovarian cancer cell lines. All 16 peptides are derived from source proteins with diverse functions and marked homology to known proteins found in public databases. Synthetic peptide analogues of identified sequences were found to stabilize HLA-A2.1, albeit with varying affinities. The peptides were found to be antigenic in that a primary CD8(+) CTL response could be elicited from normal donor blood. The CTL generated were not only peptide specific, but failed to recognize targets pulsed with control peptides. In addition, recognition of shared HLA-A2-restricted epitopes by these CTL is suggested by their reactivity with a subset of HLA-A2(+) tumor lines and freshly isolated cancer cells or cell lines established from peritoneal ascites. These results were further corroborated by competitive inhibition of lysis of an otherwise susceptible cell line in the presence of cold peptide-pulsed targets. Furthermore, lack of recognition of several HLA-A2(+) control cell lines or cells isolated from normal ovaries suggests that these peptides are cancer related. These findings broaden the list of CTL-defined antigens that could lead to the development of multi-epitope vaccines for the treatment of ovarian cancer.

Polyethylenimine-based siRNA nanocomplexes reprogram tumor-associated dendritic cells via TLR5 to elicit therapeutic antitumor immunity

“…First, ovarian cancers express tumor antigens known to be recognized by antibodies and/or CD8 + T cells (42)(43)(44)(45). Second, the infiltration of ovarian tumor islets by T cells is a strong independent prognostic factor (12,14,15).…”

Mannose Receptor Targeting of Tumor Antigen pmel17 to Human Dendritic Cells Directs Anti-Melanoma T Cell Responses via Multiple HLA Molecules

“…Autologous B cell lines were prepared as previously described (32). Briefly, 2.5-3 ϫ 10 7 /ml PBMCs were infected by incubation with B95.8 supernatants (American Type Culture Collection) for 90 min at 37°C, followed by addition of 5 ml of RP-15 medium (RPMI 1640 supplemented with 20 mM HEPES, 2 mM L-glutamine, 1% sodium pyruvate, 15% FBS, 40 g/ml gentamicin, and 50 M 2-ME).…”

“…Medium was changed on days 5 and 8 by first removing half the spent medium and replacing with fresh medium containing 50 U/ml IL-2. T cells were harvested and assayed between days 10 -12 or were cryopreserved for later use (32).…”

Rapid T cell–based identification of human tumor tissue antigens by automated two-dimensional protein fractionation

“…By eluting MHC I-bound peptides from tumor cells and subsequently identifying corresponding TAAs by mass spectrometry (MS), antigen epitopes being processed and presented by tumor cells to the immune system can be identified (3)(4)(5)(6)(7)(8). However, such approaches do not answer the question of whether such epitopes are recognized by the patient's immune system and do not address the issue of MHC II-restricted epitopes playing a major role in efficient tumor-immune rejection and in autoimmune disease.…”