BackgroundCTLA-4 (Cytotoxic T lymphocyte antigen-4) is traditionally known as a negative regulator of T cell activation. The blocking of CTLA-4 using human monoclonal antibodies, such as Ipilimumab, is currently used to relieve CTLA-4-mediated inhibition of anti-tumor immune response in metastatic melanoma. Herein, we have analyzed CTLA-4 expression and Ipilimumab reactivity on melanoma cell lines and tumor tissues from cutaneous melanoma patients. Then, we investigated whether Ipilimumab can trigger innate immunity in terms of antibody dependent cellular cytotoxicity (ADCC) or Tumor Necrosis Factor (TNF)-α release. Finally, a xenograft murine model was set up to determine in vivo the effects of Ipilimumab and NK cells on melanoma.MethodsCTLA-4 expression and Ipilimumab reactivity were analyzed on 17 melanoma cell lines (14 primary and 3 long-term cell lines) by cytofluorimetry and on 33 melanoma tissues by immunohistochemistry. CTLA-4 transcripts were analyzed by quantitative RT-PCR. Soluble CTLA-4 and TNF-α were tested by ELISA. Peripheral blood mononuclear cells (PBMC), NK and γδT cells were tested in ADCC assay with Ipilimumab and melanoma cell lines. TNF-α release was analyzed in NK-melanoma cell co-cultures in the presence of ipilimumab. In vivo experiments of xenotransplantation were carried out in NOD/SCID mice. Results were analyzed using unpaired Student’s t-test.ResultsAll melanoma cell lines expressed mRNA and cytoplasmic CTLA-4 but surface reactivity with Ipilimumab was quite heterogeneous. Accordingly, about 2/3 of melanoma specimens expressed CTLA-4 at different level of intensity.Ipilimumab triggered, via FcγReceptorIIIA (CD16), ex vivo NK cells as well as PBMC, IL-2 activated NK and γδT cells to ADCC of CTLA-4+ melanoma cells. No ADCC was detected upon interaction with CTLA-4- FO-1 melanoma cell line. TNF-α was released upon interaction of NK cells with CTLA-4+ melanoma cell lines. Remarkably, Ipilimumab neither affected proliferation and viability nor triggered ADCC of CTLA-4+ T lymphocytes. In a chimeric murine xenograft model, the co-engraftment of Ipilimumab-treated melanoma cells with human allogeneic NK cells delayed and significantly reduced tumor growth, as compared to mice receiving control xenografts.ConclusionsOur studies demonstrate that Ipilimumab triggers effector lymphocytes to cytotoxicity and TNF-α release. These findings suggest that Ipilimumab, besides blocking CTLA-4, can directly activate the elimination of CTLA-4+ melanomas.

Herein we describe that in classic Hodgkin lymphomas (cHL, n ‫؍‬ 25) the lymph node (LN) stroma displayed in situ high levels of transcription and expression of the disulfide-isomerase ERp5 and of the disintegrin-metalloproteinase ADAM10, able to shed the ligands for NKG2D (NKG2D-L) from the cell membrane. These enzymes were detected both in LN mesenchymal stromal cells ( IntroductionIt is now accepted that the so-called stress surveillance contributes to the anti-neoplastic immunity, both in solid tumors and hematologic malignancies, through the activation of the NKG2D receptor that recognizes NKG2D ligands (NKG2D-L) on cancer cells, including the MHC class-I related chain-A and -B (MIC-A/B) and the UL16-binding proteins 1-4 (ULBPs). [1][2][3][4][5] These ligands are commonly expressed at very low levels or retained in the cytoplasm, in healthy tissues, but their transcription and surface expression are enhanced on viral infection or tumor transformation. [5][6][7][8][9] Besides natural killer cells and CD8 ϩ T lymphocytes, ␥␦ T cells can recognize these molecules and activate an antitumor response in different cancers. [10][11][12][13][14][15][16][17] In this regard, we have described that ␥␦ T lymphocytes belonging to the V␦1 subset are expanded in patients with chronic lymphocytic leukemia (CLL) and nonHodgkin lymphomas (NHLs), where they proliferate in response to tumor cells, provided they express NKG2D-L, exert cytotoxicity, and produce anti-neoplastic or pro-differentiating cytokines, such as TNF-␣ and IL-4. 15,16 However, NKG2D-L can be shed by tumor cells and, in their soluble form, interact with NKG2D expressed by effector lymphocytes and hinder the recognition of tumor cells. 18,19 Proteolytic cleavage of MIC-A has been shown to depend on the thiol isomerase ERp5 and the disintegrins and metalloproteinases ADAM10 and ADAM17, which are also able to cleave ULBPs. 19,22 Overexpression of these enzymes has been reported in multiple myeloma and other tumors. [19][20][21][22][23] In turn, soluble (s) NKG2D-L and cytokines produced at the tumor site can down-regulate the expression of the NKG2D receptor on effector lymphocytes, contributing to tumor escape from immunosurveillance. [22][23][24][25] Indeed, the TGF-␤ has been shown to reduce the surface density of the NKG2D receptor on CD8 ϩ T and NK cells, impairing their antitumor reactivity in cancer patients. [24][25][26] Moreover, we and others reported that plasma levels of sNKG2D-L correlate with disease progression in multiple myeloma, CLL, NHL, and acute myeloid leukemias; in particular, among sNKG2D-L, both sMIC-A and sULBP2 have been shown as a prognostic marker for multiple myeloma and for the identification of early-stage CLL patients with risk of disease progression. [14][15][16]21,27,28 In this paper, we studied 25 classic HL (cHL) and found that the tumor microenvironment is prone to inhibit the development of an antitumor response. This is mainly because of the release of soluble MIC-A and ULBP3 by lymph node mesenchymal stromal cells (LN MS...

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