BackgroundDouble positive (DP) CD4CD8 Tαβ cells have been reported in normal individuals as well as in different pathological conditions including inflammatory diseases, viral infections and cancer, but their function remains to be elucidated. We recently reported the increased frequency of DP Tαβ cells in human breast pleural effusions. This manuscript addresses the question of the existence and above all the role of this non-conventional DP sub-population among tumor associated lymphocytes in melanomas.Methodology/Principal FindingsWe analyzed the intratumoral cell infiltrate in solid metastasis (n = 6) and tumor invaded lymph nodes (n = 26) samples from melanomas patients by multiparametric cytometry. Here we documented for the first time significant increased frequency of DP T cells in about 60% of melanoma tumors compared to blood samples. Interestingly, a high proportion of these cells produced TNF-α in response to autologous melanoma cell lines. Besides, they are characterized by a unique cytokine profile corresponding to higher secretion of IL-13, IL-4 and IL-5 than simple positive T cells. In deep analysis, we derived a representative tumor-reactive DP T cell clone from a melanoma patient's invaded lymph node. This clone was restricted by HLA-A*2402 and recognized both autologous and allogeneic tumor cells of various origins as well as normal cells, suggesting that the target antigen was a ubiquitous self antigen. However, this DP T cell clone failed to kill HLA-A*2402 EBV-transformed B cells, probably due to the constitutive expression of immunoproteasome by these cells.Conclusions/SignificanceIn conclusion, we can postulate that, according to their broad tumor reactivity and to their original cytokine profile, the tumor associated DP T cells could participate in immune responses to tumors in vivo. Therefore, the presence of these cells and their role will be crucial to address in cancer patients, especially in the context of immunotherapies.

Breast cancer remains a leading cause of cancer-related death within the female population. Immunotherapy is expected to provide additional therapeutic benefits but has met so far limited success. This may be due in part to the poor understanding of immune responses to breast cancer. Although CD4 1 and CD8 1 T lymphocytes infiltrate these tumors, the phenotype and functions of these cells remain ill defined. This study was designed to investigate further about these questions, taking advantage of multiparameter flow cytometry on lymphocytes derived from peripheral blood, solid tumors, metastatic lymph nodes and pleural effusions samples of patients with breast cancer. Results showed that, in addition to conventional CD4 1 and CD8 1 ab T cells, individual tumors and most pleural effusions contained significant fractions of unconventional double positive (DP) CD4 1 CD8 1 ab T cells. These DP T cells displayed the phenotype and cytotoxic potential of effector/memory activated CD8 1 T cells but differed essentially from these cells by a high production of IL-5 and IL-13. The increased frequency of DP T cells in advanced breast cancer and their high lytic potential and original cytokine profile suggest that this T-cell subset may play a specific role in the regulation of immune responses to human breast cancer. ' 2009 UICC

We recently showed that the infusion of tumor infiltrating lymphocytes specific for the MELOE-1 antigen was associated with a prolonged relapse-free survival for HLA-A2 1 melanoma patients who received tumor infiltrating lymphocytes therapy. Here, we characterized the MELOE-1/A2-specific T-cell repertoire in healthy donors and melanoma patients to further support an immunotherapy targeting this epitope. Using tetramer enrichment followed by multicolor staining, we found that MELOE-1-specific T cells were present in the blood of healthy donors and patients at similar frequencies (around 1 in 1  10 5 CD8 1 cells). These cells mainly displayed a naïve phenotype in 4/6 healthy donors and 3/6 patients, whereas high proportions of memory cells were observed in the remaining individuals of both groups. There was a recurrent usage of the Va12.1 chain for 17/18 MELOE-1-specific T-cell clones derived from healthy donors or patients, associated with diverse Vb chains and V(D)J junctional sequences. All clones derived from melanoma patients (9/9) were reactive against the MELOE-1 36-44 peptide and against HLA-A2 1 melanoma cell lines. This study documents the existence of a large TCR repertoire specific for the MELOE-1/A2 epitope and its capacity to give rise to antitumor CTL that supports the development of immunotherapies targeting this epitope.Key words: Immunotherapy . Melanoma . MELOE-1 . T-cell repertoire . TCR Introduction A key advance in tumor immunology in the past 15 years has been the elucidation of the antigenic basis of tumor cell recognition and destruction, which has opened the way to development of antigen-based immunotherapy in cancer patients. Tumor-associated antigens (TAA) have been grouped into categories according to their expression pattern in neoplastic and normal tissues. TAA can be roughly subdivided into two main classes: proteins expressed specifically by tumor cells, and proteins that are expressed by both tumor cells and by normal cells to a significant level. The first category includes cancergermline antigens, proteins expressed by unconventional gene expression and mutated antigens (see [1] for review). TAA belonging to the second category are the differentiation antigens, mainly expressed in the melanocytic lineage, and the antigens overexpressed by various tumor tissues. Although the immunogenicity of a number of TAA has been documented in clinical à These authors contributed equally to this work. We recently showed a correlation between the infusion of T cells reactive against an HLA-A2 epitope derived from another melanoma antigen, MELOE-1, and time to progression of patients treated with autologous tumor infiltrating lymphocytes (TIL) [10]. This antigen is encoded by the meloe gene, overexpressed in human melanoma cell lines, when compared to normal melanocytes, and dramatically underexpressed in other cancer cell lines (colon, renal, breast and lung carcinoma cell lines) and in a variety of normal tissues [10]. This expression profile and the potential involvement of MELOE-1-specific...