IntroductionProgrammed death-1 (PD-1), a member of the CD28 costimulatory receptor superfamily, inhibits T-cell activity by providing a second signal to T cells in conjunction with signaling through the T-cell receptor. 1 To date, B7-H1 and B7-DC have been identified as ligands for PD-1 (PD-Ls). During chronic viral infection, PD-1 is selectively up-regulated by the exhausted T cells, and blockade of this pathway restores CD8 ϩ T-cell function and reduces viral load. 2 This signaling system has been recently highlighted in the research of human immunodeficiency virus (HIV) infection. [3][4][5][6] In addition, PD-1 is indicated to be involved in the evasion of tumor immunity. [7][8][9][10] Hodgkin lymphoma (HL) is characterized by massive reactive infiltrates surrounding Hodgkin/Reed-Sternberg (H/RS) cells. HL patients are well recognized as having defective cellular immunity; they are susceptible to bacterial, fungal, and viral infections, and in vitro studies show depressed T-cell proliferation and reduced synthesis of Th1 cytokines. 11 We report here that PD-1-PD-L signaling system is operative in patients with HL, and tumor-infiltrating T cells around H/RS cells seem to be kept in balance by this inhibitory signaling. Our findings illuminate the mechanism for deficient cellular immunity observed in HL patients, and propose a potentially effective immunologic strategy for the treatment of HL. Methods Cell lines and clinical sample preparationThe following cell lines were described previously 12,13 : HL cell lines KM-H2, L428, and HDLM-2; anaplastic large cell lymphoma (ALCL) cell line DEL; follicular lymphoma cell line FL-218; diffuse large B-cell lymphoma (DLBCL) cell line KIS-1; Burkitt lymphoma cell lines Daudi, Raji, Middle 91, Tree 92, and Ramos; adult T-cell leukemia/lymphoma cell line HUT 102; and acute T-cell leukemia cell line Jurkat. LCL-OHN is an Epstein-Barr virus (EBV)-transformed lymphoblastoid B-cell line (LCL). Peripheral blood samples were collected from 19 HL patients, 12 B-NHL patients, and 11 healthy volunteers after informed consent was obtained in accordance with the Declaration of Helsinki. This study is approved by the institutional review board of Kyoto University. After removing red blood cells using ACK lysis buffer, leukocytes were subjected to flow cytometry. For immunohistochemistry, tissue specimens were snap-frozen in OCT compound (TissueTek, Tokyo, Japan) and stored at Ϫ80°C. Reverse transcription-polymerase chain reaction, flow cytometry, and immunohistochemistryTotal RNA was isolated from cells with Trizol (Invitrogen, Carlsbad, CA), and cDNA was synthesized using MultiScribe Reverse Transcriptase (Applied Biosystems, Foster City, CA). PCR assays were performed by the conventional method using Taq polymerase (TaKaRa Biotechnology, Shiga, Japan). For flow cytometry, cells were analyzed on a FACScan (Becton Dickinson, Mansfield, MS). The following antibodies were used: PEconjugated B7-H1 and B7-DC (eBioscience, San Diego, CA), FITC-PD-1 (BD Pharmingen, San Diego, CA), PC5-CD4 a...

Ceramide is now recognized as an intracellular lipid signal mediator, which induces various kinds of cell functions including apoptosis. Ceramide-induced apoptosis was reported to be blocked by 12-O-tetradecanoylphorbol 13-acetate, a protein kinase C (PKC) activator, but its mechanism remained unclear. Therefore, we investigated whether ceramide has any effects on PKC in the induction of apoptosis. We here report that N-acetylsphingosine (synthetic membrane-permeable ceramide) induced translocation of PKC-delta and -epsilon isozymes from the membrane to the cytosol within 5 min in human leukemia cell lines. Treatment with sphingomyelinase, tumor necrosis factor-alpha, or anti-Fas antibody, all of which can induce apoptosis by generating natural ceramide, similarly induced cytosolic translocation of PKC-delta and -epsilon. In Fas-resistant cells anti-Fas antibody did not induce cytosolic translocation of PKC-delta and -epsilon because of no generation of ceramide, whereas N-acetylsphingosine induced apoptosis with cytosolic translocation of PKC-delta and -epsilon. Furthermore, both 12-O-tetradecanoylphorbol 13-acetate and a nonspecific kinase inhibitor, staurosporine, prevented ceramide-induced apoptosis by inhibiting cytosolic translocation of PKC-delta and -epsilon. These data suggest that cytosolic translocation of PKC-delta and -epsilon plays an important role in ceramide-mediated apoptosis.

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B7-H1 is a member of the B7 family that inhibits the function of T-cells through its receptor programmed death-1 (PD-1). We examined B7-H1 expression in anaplastic large cell lymphoma (ALCL) and Hodgkin lymphoma (HL) and found that it was constitutively expressed in both clinical samples and cell lines. In anaplastic lymphoma kinase-positive (ALK + ) ALCL cells, B7-H1 expression was suppressed by the blocking of extracellular signal-regulated kinase (ERK) signaling and upregulated by the augmentation of ERK activity by phorbol 13-myristate 12-acetate stimulation, suggesting that B7-H1 expression is regulated by ERK signaling pathway in ALCL. ERK is one of the downstream mediators of nucleophosmin (NPM)/ALK signaling in ALK + ALCL, and pharmacological inhibition of ALK was shown to dephosphorylate ERK and downregulate B7-H1. The involvement of NPM /ALK in B7-H1 expression was also demonstrated by introducing the construct into human non-ALCL lymphoid cell lines, which resulted in B7-H1 expression. In the case of HL, B7-H1 expression was shown to be dependent on the ERK and p38 mitogen-activated protein kinase (MAPK) signaling pathways. These results suggest that B7-H1 expression is controlled by common ERK signaling pathways in ALCL and HL cells. Our findings provide a potentially effective immunotherapeutic strategy for these B7-H1-expressing tumors. (Cancer Sci 2009; 100: 2093-2100) P rogrammed death-1 (PD-1) is a member of the CD28 costimulatory receptor superfamily that inhibits T-cell activity by providing a second signal to T-cells in conjunction with signaling via the T-cell receptor.(1,2) One of its ligands B7-H1, which is also known as PD-L1 or CD274, is reported to be expressed on a variety of malignancies, including breast, lung, colon, and ovarian cancers.(3) Its expression is associated with poor prognosis in some of these diseases.(4,5) Several studies using mouse models have indicated that PD-1 ⁄ B7-H1 signaling plays a pivotal role in the immune escape of tumors. Subcutaneously injected B7-H1-expressing tumor cells grow in wild-type mice but are eliminated in PD-1 knockout mice.(6) In addition, B7-H1 expression on tumor cells increases the apoptosis of tumor-reactive T-cells.(7) However, little is known about the regulatory mechanisms of B7-H1 expression in these malignant cells.Hodgkin lymphoma (HL) is characterized by massive reactive infiltrates surrounding Hodgkin ⁄ Reed-Sternberg (H ⁄ RS) cells, and H ⁄ RS cells represent only about 1% of cells in tumor tissues. We previously reported B7-H1 expression in H ⁄ RS cells and PD-1 expression in tumor-infiltrating T-cells and that the antitumor activity of T-cells was restored by blocking the PD-1 ⁄ B7-H1 signaling pathway. (8) Anaplastic large cell lymphoma (ALCL) is a subtype of T-cell lymphoma characterized by a proliferation of CD30-positive large tumor cells with abundant cytoplasm and pleomorphic nuclei. ALCL is sometimes accompanied by variable amounts of reactive cells, and the clinical and pathological features of ALCL often resemble those...

Programmed death-1 (PD-1), a member of the CD28 costimulatory receptor superfamily, inhibits T cell activity by providing a second signal to T cells in conjunction with signaling through the T-cell receptor. PD-1/PD-1 ligand (PD-L) signaling system is indicated to be involved in the functional impairment of T cells such as in chronic viral infection or tumor immune evasion. We hypothesized that this signaling system is also involved in the pathogenesis of Hodgkin lymphoma (HL). We examined expression of B7-H1 and B7-DC, two known PD-Ls, in lymphoid cell lines using RT-PCR and flow cytometry. They were expressed in HL and several T-cell lines, whereas most B-NHL lines lacked their expression. Immunohistochemical staining of HL tissues demonstrated that PD-Ls were also expressed in primary H/RS cells. As gene expression of B7-H1 and B7-DC was increased in Epstein-Barr virus (EBV)-transformed lymphoblastoid B-cell lines, we examined the effect of EBV latent membrane proteins on their gene regulation. By luciferase reporter assay, both LMP1 and LMP2A were shown to enhance promoter activity of B7-H1 and B7-DC genes. This finding implies that in cases of EBV-positive HL, latent membrane proteins may help H/RS cells escape from host immune surveillance by upregulating PD-L gene expression. We next analyzed PD-1 expression of tumor-infiltrating T cells of HL tissue samples by flow cytometry, and found that PD-1+ cells were elevated markedly in these cells. As HL patients are well recognized as having defective cellular immunity, we compared PD-1 expression level in peripheral blood T cells of HL patients with those of healthy volunteers and B-NHL patients. PD-1 was significantly elevated in peripheral T cells of HL patients compared to the other two groups. PD-1+ T cells were highest in patients with active disease, and tended to decline along with treatment. Although regulatory T cells are reported to play a part in the pathogenesis of HL, FOXP3+ T cells were not significantly elevated in peripheral T cells of HL patients, and PD-1+ T cells did not overlap with these regulatory population. To elucidate whether the PD-1/PD-L signaling pathway is functional in the immunosuppressive microenvironment of HL, we finally examined the effect of blockade of this pathway. After culturing bulk HL tumor cells with anti-PD-L blocking antibodies, IFN-γ production was measured by ELISA. Blockade of PD-Ls augmented IFN-γ production of HL-infiltrating T cells. We concluded that anti-tumor activity of HL-infiltrating T cells was inhibited via the PD-1/PD-L pathway, and this inhibition could be successfully relieved by PD-L blockade. Taken together, our observations indicate that “T-cell exhaustion” is essential to the pathogenesis of HL, and tumor-infiltrating T cells around H/RS cells seem to be kept in balance by this inhibitory signaling. Our findings provide a potentially effective and clinically applicable strategy for the immunotherapy of HL.