STUDY. Increased Programmed Death-1 Expression on CD4 T Cells in Cutaneous T-Cell Lymphoma

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1 ONLINE FIRST STUDY Increased Programmed Death-1 Expression on T Cells in Cutaneous T-Cell Lymphoma Implications for Immune Suppression Sara Samimi, MD; Bernice Benoit, BS; Katherine Evans, MD; E. John Wherry, PhD; Louise Showe, PhD; Maria Wysocka, PhD; Alain H. Rook, MD Objectives: To investigate the expression profile of programmed death-1 (PD-1) on T cells derived from patients with cutaneous T-cell lymphoma (CTCL), analyze a potential mechanism responsible for upregulation of PD-1, and assess the correlation between blockade of its signaling pathway and improvement in immunological function. Design: Translation research study. Setting: University medical center. Participants: Patients with Sézary syndrome, patients with mycosis fungoides, and healthy volunteers. Main Outcome Measures: Programmed death-1 expression on T cells by flow cytometry and interferon (IFN- ) production by enzyme-linked immunosorbent assay. Results: We report significantly increased PD-1 expression on T cells from patients with Sézary syndrome compared with T cells from patients with mycosis fungoides and healthy volunteers. Both CD26 and CD26 populations of T cells demonstrated increased expression of PD-1, which was upregulated by the engagement of the T-cell receptor with anti-cd3/cd28 antibodies. In addition, blockade of the signaling pathway with blocking antibodies to PD-1 or its ligand PD-L1 led to an increase in the capacity to produce IFN- among some patients. Finally, longitudinal studies of 1 patient revealed a progressive decrease in PD-1 expression on T cells with improvement of clinical disease. Conclusion: Our data imply that increased PD-1 expression in Sézary syndrome may play a role in attenuating the immune response and provide further insight into the immunosuppressive nature of T cells in Sézary syndrome and suggest another potential means of targeted therapy for these patients. Arch Dermatol. 2010;146(12): Published online August 16, doi: /archdermatol Author Affiliations: Departments of Dermatology (Drs Samimi, Evans, Wysocka, and Rook and Ms Benoit), Microbiology (Dr Wherry), and Molecular and Cellular Oncogenesis (Dr Showe), University of Pennsylvania School of Medicine and the Wistar Institute, Philadelphia. CUTANEOUS T-CELL LYMPHOmas (CTCLs) are typically a group of lymphoproliferative disorders comprised of clonally derived skin-homing T cells. Mycosis fungoides (MF) and Sézary syndrome (SS) are the most common forms of CTCL. Sézary syndrome, a leukemic variant of CTCL, is defined by the triad of erythroderma, generalized lymphadenopathy, and the presence of neoplastic T cells in the skin, lymph nodes, and peripheral blood. 1 The neoplastic cell is typically characterized by a CD26 phenotype. 2 Patients with SS manifest both clinical and immunologic abnormalities. They commonly display, within the peripheral blood and skin, a helper T cell, subtype 2 (T H 2) cytokine profile characterized by increased levels of interleukin 4 (IL-4) and IL-5 3 and concomitant decreased levels of T H 1 cytokines such as IL-2 and interferon (IFN- ), 4 resulting in reduced cellmediated immunity. 5 Even though circulating populations of activated CD8 T cells are detected, malignant T cells persist, suggesting the inability to mount an effective immune response. 6 Endogenous immunosuppression, implicated by an ineffective effector response and an altered cytokine milieu, renders patients susceptible to opportunistic infections. 7 Overall, these findings point to the immunosuppressive nature of the disease, with malignant T cells evading the immune system and resisting activation-induced cell death. 8 Programmed death-1 (PD-1) was originally cloned as a molecule overexpressed on apoptotic cells. 9 It is commonly expressed on activated T cells and B cells on T-cell receptor and B-cell receptor stimulation, re- 1382

2 spectively. 10 Programmed death-1, a member of the B7- CD28 family, has 2 known ligands, PD-L1 and PD-L2; PD-L1 is expressed on many cell types, such as T cells, dendritic cells, and tumor cells, whereas PD-L2 expression is limited to antigen-presenting cells. 11 Engagement of PD-1 by its ligands transduces a signal that leads to inhibition of T-cell function, including proliferation and cytokine production. 12 Therefore, it is postulated that a major function of PD-1 is to attenuate the immune response. Increased expression profiles of PD-1 have been identified in models of defective immune function, including chronic viral infection and adult T-cell leukemia/ lymphoma, 16 indicating a role in disease progression and immunosuppression. Murine models have demonstrated the crucial role that PD-1 plays in maintenance of selftolerance and prevention of autoimmunity. 17 In these models, alteration of the PD-1 gene and/or complete knockout of the gene has led to diabetes mellitus, 18 lupus, 19 and autoimmune cardiomyopathy. 20 It has been proposed that the loss of PD-1 may lower the threshold for antigen recognition in peripheral tissues evidenced by increased numbers of antigen-specific cytotoxic cells and increased cytokine production when compared with wild-type mice. 21 Furthermore, blockade of the PD-1/PD-L1 pathway results in the restored ability to proliferate and secrete cytokines. 13,22-24 In this study, we investigate the expression profile of PD-1 on T cells derived from patients with CTCL, and its functional significance for IFN- production. Our data imply a role for PD-1 in attenuating the immune response and antitumor immunity, providing further insight into the immunosuppressive nature of T cells in CTCL and the potential for immunotherapy. METHODS PATIENTS Blood samples were collected from healthy donors (HDs), and from patients with MF and SS who were seen and followed at the University of Pennsylvania Cutaneous Lymphoma Clinic, Philadelphia. Donation of blood by patients and HDs conformed to the protocols approved by the University of Pennsylvania institutional review board, and written informed consent was obtained. Patients were considered to have a low to medium tumor burden if their percentage of circulating malignant T cells with the flow cytometric phenotype of CD26 ranged from 20% to less than 50% of total lymphocytes. Patients whose percentage of circulating phenotypically abnormal T cells was 50% or higher were considered to have a high tumor burden. 25 Peripheral blood cells from a total of 21 patients with SS, 4 patients with MF (skin-only involvement without blood involvement with less than 5% CD26 T cells), and 5 agematched HDs were evaluated over the course of this study. The diagnoses of SS and MF were made clinically, histologically, and by flow cytometry of the blood and conformed to the criteria of the International Society for Cutaneous Lymphomas and the European Organization of Research and Treatment of Cancer. 26 PERIPHERAL BLOOD MONONUCLEAR CELL ISOLATION AND CULTURE Venous blood was collected into heparinized syringes using uniform standards. The heparinized blood was diluted 1:2 with phosphate-buffered saline (PBS) and was layered on a Ficoll- Hypaque gradient (Amersham, Pittsburgh, Pennsylvania). The gradient was centrifuged at 2400 rpm for 30 minutes at room temperature. The peripheral blood mononuclear cell (PBMC) band was collected and washed twice in PBS. Cells were cultured in medium (RPMI 1640; Life Technologies, Gaithersburg, Maryland) supplemented with 10% fetal bovine serum, 1% penicillin/streptomycin, and 1% L-glutamine (all from Gibco- BRL, Grand Island, New York). FLOW CYTOMETRY To detect PD-1 expression on T cells, approximately 1 million PBMCs per sample were stained with CD8 fluorescein isothiocyanate, CD26 phycoerythrin, peridinin chlorophyll protein complex, and PD-1 allophycocyanin (all from BD Pharmingen, San Jose, California) for 30 minutes on ice. Cells were analyzed with the FACS Calibur flow cytometer using CELLQuest software (BD Biosciences, San Jose) at the Flow Cytometry and Cell Sorting Core, Abramson Cancer Center, University of Pennsylvania. Approximately cells were collected for each analysis. STIMULATION WITH ANTI-CD3/CD28 ANTIBODIES: ASSESSMENT OF PD-1 EXPRESSION AND IFN- LEVELS AFTER PD-1/PD-L1 BLOCKADE Freshly isolated PBMCs from patients and HDs were plated at a density of /ml per well in the presence or absence of anti-cd3/cd28 antibodies (R&D Systems, Minneapolis, Minnesota) (0.5 µg each) with medium alone, isotype control antibody (ebioscience, San Diego, California) (17 µg/ml), purified anti PD-1 (R&D Systems) (17 µg/ml), or purified anti PD-L1 (ebioscience) (17 µg/ml). Cells were incubated at 37 C in 5% carbon dioxide for 72 hours prior to the collection of supernatants for cytokine analysis or assessment of PD-1 expression on cultured T cells by flow cytometry. ELISA FOR CYTOKINE ANALYSIS Culture supernatants were harvested at 72 hours and stored at 80 C until analysis (not exceeding 3-4 weeks). Interferon production was detected by enzyme-linked immunosorbent assay (ELISA) according to the manufacturer s recommendations using a DuoSet ELISA kit (R&D Systems) (sensitivity for IFN- : 10 pg/ml). STATISTICAL ANALYSIS Data are expressed as means (SDs) in Figure 1 for tested individuals. Statistical significance was determined using the t test when applicable. RESULTS SIGNIFICANT INCREASE IN CIRCULATING PD-1 T CELLS FROM PATIENTS WITH SS COMPARED WITH T CELLS FROM THOSE WITH MF OR HDs Increased levels of PD-1 or its ligand PD-L1 have been observed on so-called exhausted T cells during chronic viral infections and on various tumor cells. 13,15,16,25,27,

3 + PD-1 +, % P <.01 HDs MF SS Patients + CD CD26 Figure 1. Increased expression of programmed death-1 (PD-1) on T cells from patients with Sézary syndrome (SS). The peripheral blood mononuclear cells from patients with SS (n=7), patients with mycosis fungoides (MF) (n=4), and healthy donors (HDs) (n=4) were stained with anti-, anti PD-1, and anti-cd26, and were analyzed by flow cytometry. The percentage of PD-1 is demonstrated according to patient population and CD26 status. Error bars indicate the standard deviation of uncertainty. We postulated that a similar increase in PD-1/PD-L1 expression would be evident on T cells of patients with SS. Seven patients with SS (of a total of 14 patients tested), 4 patients with MF, and 5 age-matched HDs were tested for PD-1 expression in association with, CD8, and CD26 by flow cytometry using antibody against PD-1. The PD-1 T cells were significantly increased in patients with SS compared with T cells from patients with MF or age-matched HDs (P.01) (Figure 1). The percentage of PD-1 CD8 T cells from patients with SS, although increased in comparison to those from HDs, was not statistically significant (P =.05) (data not shown). Expression of PD-L1 or PD-L2 was not detected on either population of T cells. However, variable and/or low-level expression of PD-L1 (range, 0.5%-7.4%) was observed on CD14 monocytes from some, but not all, HDs and patients (data not shown). It is noteworthy that the CD26 population from patients with SS (range, 20%-98% of T cells) showed a small, but statistically insignificant (P=.42), upregulation of PD-1 expression compared with the CD26 population (range, 2%-80% of T cells) (Figure 1). T-CELL RECEPTOR ACTIVATION AND UPREGULATION OF PD-1 EXPRESSION ON T CELLS FROM PATIENTS WITH SS To further investigate the underlying mechanisms responsible for upregulated PD-1 expression on patients T cells, we examined the effect of anti-cd3/ CD28, IFN-, or IFN- on the expression of PD-1. The engagement of the T-cell receptor by anti-cd3/cd28 led to enhanced expression of PD-1 on T cells from 12 patients with SS. Stimulation of PBMCs from patients with a low to medium tumor burden (and from HDs; data not shown) with anti-cd3/28 resulted in an increase in the percentage of PD-1 expression on both CD26 and CD26 T cells, and an increase in density of PD-1 molecules on the surface of those cells (mean fluorescent intensity [MFI], 1.2- to 1.3-fold increase, respectively) (Figure 2A). In contrast, patients with a high tumor burden did not demonstrate an increased percentage of PD-1 within CD26 T cells. However, an increase in MFI (1.0-fold) suggests an increase in density of PD-1 molecules on some CD26 T cells on TCR stimulation. The CD26 population maintained the ability to upregulate expression of PD-1 on anti-cd3/cd28 engagement, resulting in an increased percentage of PD-1 T cells and intensity of PD-1 expression on cell surfaces (1.2-fold increase in MFI) (Figure 2B). Both IFN- and IFN- have been used as therapeutic modalities for CTCL, and consequently we theorized that they might play a role in the expression of PD-1. However, findings from cultures of PBMCs from patients and HDs for 3 days with either interferon (at 10 ng/ml) did not alter the expression profile of PD-1 on T cells. Both interferons also failed to upregulate PD-L1 on T cells, but in concordance with previously published data, IFN-, and, to a lesser extent, IFN- were able to upregulate expression of PD-L1 on monocytes (data not shown). 29 PD-1/PD-L1 BLOCKADE AND ENHANCED IFN- PRODUCTION The expression of PD-L1 on monocytes of some patients (4 patients; range, 0.7%-7.4% of CD14 T cells), although low, suggested the potential for the engagement of the PD-1/PD-L1 pathway to affect the end production of cytokines, such as IFN-. To analyze the effect of blocking PD-1 and PD-L1 on cytokine production, we performed coculture assays using PBMCs from 6 patients with SS and 2 HDs in the presence of blocking antibody to PD-1 or PD-L1. We incubated the cells in medium alone or in the presence of CD3/CD28 to determine a change in IFN- production. After the cells had been in the culture for 72 hours, we noted enhanced production of IFN- in 3 of 6 patients and 1 HD when cells were activated with anti-cd3/cd28 in the presence of blocking antibodies (Figure 3). It is worth noting that 2 of 3 patients demonstrated increased IFN- production resulting from the blockade of both PD-1 and PD-L1, while 1 patient demonstrated increased IFN- production in the presence of PD-1 blocking antibody alone. CORRELATION OF DECREASE IN PD-1 EXPRESSION WITH CLINICAL IMPROVEMENT To further our understanding of the biological significance of PD-1 expression on patients T cells, we examined PBMCs from patients collected at different times and different stages of disease. In 1 patient with SS, clinical remission in association with clearing of circulating malignant T cells correlated with progressive changes of PD-1 expression on T cells from initial high 1384

4 A Gated on + CD (37.6) Gated on + CD (33.1) Medium PE (46.7) (45.4) Anti-CD3/CD PE CD PD B Gated on + CD (55.9) Gated on + CD (62.9) Medium FITC (60.6) (78.9) Anti-CD3/CD FITC CD PD Figure 2. Activation of CD26 T cells by anti-cd3/cd28 antibodies varies between patients with a low and high tumor burden in circulation. The peripheral blood mononuclear cells were isolated from either a patient with a low tumor burden (A) or a high tumor burden (B) and were cultured with medium alone or with anti-cd3/cd28. After 48 hours of stimulation, cells were harvested, stained with antibodies, and analyzed by flow cytometry. In both A and B, the top panels demonstrate cells cultured with medium alone, and the lower panels demonstrate cells cultured with anti-cd3/cd28 antibodies. Panels on the left reveal the expression of CD26 on T cells, the center panels reveal the expression of programmed death-1 (PD-1) on the CD26 population, and panels on the right reveal the expression of PD-1 on the CD26 population. The numbers in the quadrants represent the percentages of cells that are double positive for each condition, and the numbers in parentheses represent the mean fluorescent intensity for PD-1 expression. Results shown are representative of a total of 12 patients tested. indicates allophycocyanin; FITC, fluorescein isothiocyanate; PE, phycoerythrin; and, peridinin chlorophyll protein complex (all from BD Pharmingen, San Jose, California). 1385

5 IFN-γ, pg/ml Patient 1 Patient 2 Patient 3 migg Anti PD-1 Anti PD-L1 Figure 3. Blocking the pathway of programmed death-1 (PD-1) and its ligand PD-L1 results in increased interferon (IFN- ) production by patients peripheral blood mononuclear cells (PBMCs) stimulated with anti-cd3/cd28. The PBMCs of patients with Sézary syndrome were cultured for 72 hours with either medium or anti-cd3/cd28 alone, and with the following: murine IgG (migg), anti PD-1, or anti PD-L1. Subsequently, culture supernatants were collected and tested for the presence of IFN-. There was no detectable level of IFN- in samples treated with medium only (data not shown). Table. Decrease in PD-1 Expression Correlating With Clinical Improvement of Disease a Date PD-1 T Cells, % levels at the time of diagnosis to normal levels as the patient responded to immunotherapy (Table). COMMENT :CD8 CD26 T Cells, % April December *LCP March August Abbreviations: LCP, large-cell population; PD-1, programmed death-1; asterisk, the evidence of a malignant LCP, which correlates with a peak in the percentage of PD-1 expression. a Peripheral blood mononuclear cells from 1 patient were collected over 1 year and examined for PD-1 and CD26 expression on T cells and for the ratio of :CD8. Our study demonstrates increased PD-1 expression on circulating T cells of patients with SS compared with T cells of patients with MF and HDs. To our knowledge, this has not been previously described in patients with SS. The presence of PD-1 on CD26 T cells, currently defined as the malignant population of cells in CTCL, implies a role for an increase in PD-1 expression in tumor progression. This is demonstrated in the case of adult T-cell leukemia lymphoma, in which the neoplastic T cell, characterized by a CD25 phenotype, demonstrates increased PD-1 expression with a correlative increase in the absolute number of tumor cells. 16 However, in patients with SS, PD-1 is not limited to the malignant population of cells but is also found on CD26 T cells, considered normal and immunocompetent. Additional studies on the mechanisms responsible for the upregulation of PD-1 on patients T cells demonstrated upregulated PD-1 expression on both CD26 and CD26 T cells on T-cell receptor activation. Interestingly, an increase in the percentage of PD-1 CD26 T cells was apparent only in patients with a low to medium tumor burden and not in those with a high tumor burden, despite the presence of CD3 on their surface. Similarly, as we have previously reported, these patients also fail to upmodulate 0 ligand on their T cells in response to anti-cd3 ligation. 30 Our data suggest that increased expression of PD-1 on T cells from patients with SS results mainly from activation of the TCR on patients T cells with putative tumor antigen. Furthermore, both CD26 and CD26 populations, comprising normal immunocompetent cells and malignant cells, respectively, are activated, particularly in patients with low tumor burden, suggesting a less clearly defined population of potential tumor cells than previously assumed. The normal CD26 T cells may in fact contain a subset of cells that have not yet lost CD26 on their cell surface and represent an activated phenotype resulting from ongoing stimulation with tumor antigen. In addition, the CD26 T cells may contain a subset of cells that are still sensitive to TCR stimulation implicated by an increase in intensity of PD-1 expression (MFI) on CD26 T cells in patients with a high tumor burden. As tumorigenesis progresses, there seems to be a diminished capacity of peripheral blood T cells to respond to TCR stimulation. These malignant cells may represent an exhaustion phenomenon, suggesting that the level of PD-1 expression likely correlates with an impaired T-cell response. 14 At present, more detailed studies are needed to fully understand the mechanism responsible for the impairment of TCR signaling in patients with a high tumor burden. In the case of 1 patient followed longitudinally, we noted a clear correlation between a decrease in PD-1 expression with improvement in clinical disease. The change in percentage of PD-1 T cells paralleled a decrease in the :CD8 ratio and a decrease in the absolute numbers of the CD26 population in the circulation. Similar findings are noted in human immunodeficiency virus, in which PD-1 expression is shown to correlate positively with plasma viral load and inversely with a T-cell count. 14 As a result, decreased expression of PD-1 that correlates with improvement of disease status may result from either a diminished number of tumor cells expressing PD-1 owing to therapy, a loss of PD-1 on exhausted immune-compatible cells and recovery of immune function owing to therapy, or a combination of both. Of note, our previous study 31 of patients with SS revealed normalization of dysregulated immune functions during remissions induced by immune modulatory therapy. Blockade of the PD-1/PD-L1 pathway revealed a relative increase in IFN- production by PBMCs of patients with CTCL. Patients with active CTCL demonstrate a skewed cytokine profile, resulting in a deficiency of IFN- production. Interferon is critical for the generation of 1386

6 antitumor immunity and plays an important role in stabilizing a T H 1 phenotype, 32 particularly when used as a therapeutic agent. 33 In studies using human T cells, activation of those cells using anti-cd3 in the presence of PD-L1 demonstrates decreased IFN- secretion. 12 Recovery of IFN- production in some patients with CTCL during PD-1/PD-L1 blockade implies an operational PD-1/PD-L1 pathway that may contribute to a skewed cytokine profile. In the case of LCMV and human immunodeficiency virus infections, blockade of PD-L1 or PD-L2 results in enhanced T-cell proliferation, cytokine production, and restored function of exhausted CD8 T cells. 14,22 However, unlike PD-1, PD-L1 and PD-L2 are not frequently or highly expressed on monocytes and dendritic cells of patients with CTCL without stimulation by IFN-. The engagement of the TCR, which provides a strong signal for upregulation of PD-1 in patients with a low to medium tumor burden, results in a rather weak upregulation of PD-L1 or PD-L2 (data not shown). It is therefore possible that blockade of this pathway, as our results demonstrate, would not consistently result in upregulation of T H 1 cytokine production and improvement of T-cell responses in patients with CTCL. One of the most important implications of fully understanding the role of both PD-1 and PD-L1 on malignant T cells in CTCL relates to the application of novel therapies. Blockade of PD-1 can increase immune activating cytokine production and may enhance functioning of cytotoxic T cells, which would lead to enhanced disease eradication. Injection of tumors into PD-1 doublenegative mice has revealed increased effector cytokine production, greater recruitment of T cells, and reduced spread of tumor cells. 34 To further develop PD-1 targeted therapy, it will be necessary to acknowledge the complexity of its role in T-cell homeostasis by considering treatment that spares normal, immunocompetent T cells, induces a vigorous antitumor response, and avoids the consequence of inducing autoimmune disease. While PD-1 seems to act as a negative regulator of the immune response, its function in T cells, specifically in patients with SS, largely remains unclear. It is unknown whether an increase in PD-1 expression serves to protect tumor cells from elimination, particularly if PD-1 ligands are not in abundance, or if it represents an exhausted phenotype of immunocompetent cells chronically stimulated with tumor antigen. More detailed investigations are needed to fully elucidate its role in this specific patient population. Accepted for Publication: May 6, Published Online: August 16, doi: /archdermatol Correspondence: Sara Samimi, MD, University of Pennsylvania, Pennsylvania Hospital, Department of Dermatology, 800 Spruce St, Philadelphia, PA Author Contributions: Drs Samimi, Wysocka, and Rook had full access to the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Samimi, Evans, Wysocka, and Rook. Acquisition of data: Samimi, Benoit, Evans, and Wysocka. Analysis and interpretation of data: Samimi, Wherry, Showe, Wysocka, and Rook. Drafting of the manuscript: Samimi, Wysocka, and Rook. Critical revision of the manuscript for important intellectual content: Samimi, Benoit, Evans, Wherry, Showe, Wysocka, and Rook. Obtained funding: Rook. Administrative, technical, and material support: Samimi, Benoit, Evans, Wherry, Showe, and Rook. Study supervision: Evans, Wysocka, and Rook. Financial Disclosure: Dr Wherry has a licensing agreement on a PD-1 pathway blockade patent with Genentech. Funding/Support: This work was supported in part by grant CA from the National Institutes of Health, by grant NCI RO1 CA132098, and by a Translational Research Grant from the Leukemia and Lymphoma Society. Role of the Sponsors: The sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of data; or in the preparation, review, or approval of the manuscript. REFERENCES 1. Willemze R, Jaffe ES, Burg G, et al. WHO-EORTC classification for cutaneous lymphomas. Blood. 2005;105(10): Jones D, Dang NH, Duvic M, Washington LT, Huh YO. Absence of CD26 expression is a useful marker for diagnosis of T-cell lymphoma in peripheral blood. Am J Clin Pathol. 2001;115(6): Vowels BR, Cassin M, Vonderheid XX, Rook AH. Aberrant cytokine production by Sézary syndrome patients: cytokine secretion pattern resembles murine Th2 cells. 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