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News Article | May 5, 2017
Site: www.eurekalert.org

Platelets promote immune tolerance to certain cancers by suppressing T cells and adoptive T cell therapy may be enhanced by adding antiplatelet drugs, report researchers at the Medical University of South Carolina in Science Immunology Blood platelets help disguise cancer from the immune system by suppressing T cells, report scientists at the Medical University of South Carolina (MUSC) in the May 5, 2017 issue of Science Immunology. In extensive preclinical tests, a promising T cell therapy more successfully boosted immunity against melanoma when common antiplatelet drugs such as aspirin were added. Zihai Li, M.D., Ph.D., senior author on the article, is chair of the MUSC Department of Microbiology and Immunology, the program leader for the Cancer Immunology Research Program at MUSC Hollings Cancer Center, and the SmartState® Sally Abney Rose Chair in Stem Cell Biology & Therapy. Li studies how tumors hide themselves from the immune system. Li's team found that platelets release a molecule that suppresses the activity of cancer-fighting T cells. That molecule, unsurprisingly, was TGF-beta, which has been recognized for decades for its role in cancer growth. Yet this study is the first of its kind. Most TGF-beta is inactive. Li and his group found that the surface of platelets has a protein called GARP, a molecular hook that is uniquely able to trap and activate TGF-beta. Platelets, which are small cell fragments that circulate throughout the blood and are normally involved in clotting, become the major source of activated TGF-beta that invading tumor cells use to suppress T cells. In other words, platelets help give tumors their invisibility cloak from the immune system. Scientists have known for several years that certain cancers suppress T cells to avoid the immune system. That is why adoptive T cell therapy is one of the most promising advances in modern cancer treatment. It is a type of immunotherapy that awakens the immune system by retraining a patient's T cells to recognize their cancer. T cells are isolated from a patient's blood and retrained, or "primed," to recognize tumor cells. They are then injected back into the patient's bloodstream where they can now hunt and fight cancer. There was some evidence that platelets might make cancer worse. For example, patients who have excessive clotting related to their cancer almost always have a worse prognosis, according to Li. "Over the years, it has become appreciated that platelets are doing more than just clotting," says Li. The first clue that cancer-fighting T cells might be suppressed by the body's own clotting system came when the researchers gave melanoma to mice with genetically defective platelets. Melanoma tumors grew much more slowly and primed T cells were much more active than in mice with normal platelets. Next, the team isolated platelets and T cells from blood drawn from humans and mice. In both cases, platelets with activated clotting activity suppressed T cell response. It then used mass spectrometry to thoroughly identify the molecules released by activated platelets that most suppressed T cell activity. The molecule with the most T cell suppression was TGF-beta. Li and his team then studied how platelets activate TGF-beta. In genetically modified mice without GARP, the molecular hook on the surface of platelets, adoptive T cell therapy was more successful at controlling melanoma. This meant that platelets without the ability to grab and activate TGF-beta were not able to suppress cancer-fighting T cells. Similar experiments confirmed this result in mice with colon carcinoma. Finally, mice with normal platelets that were given melanoma and then adoptive T cell therapy survived longer and relapsed less when aspirin and clopidogrel, two antiplatelet drugs, were added. The researchers noted that antiplatelet drugs by themselves were not successful in combating melanoma in their experiments. This study could inform future treatment of melanoma and other cancers and offers a sound reason to test antiplatelet drugs in clinical trials of adoptive T cell therapy. In patients with melanoma or other cancers, adoptive T cell therapy may be successful if highly available platelet-blocking drugs such as aspirin are added to the treatment. However, the current standard of care for melanoma is not adoptive T cell therapy, but so-called checkpoint inhibitors. Li and his group want to know if combination therapy with antiplatelet drugs could improve existing cancer treatment. They are waiting for approval to begin a clinical trial that will test certain checkpoint inhibitors in combination with aspirin and clopidogrel for the treatment of patients with advanced cancers. Li's trial will complement clinical trials that are already testing adoptive T cell therapy as a single treatment for cancer. "I'm very excited about this," says Li. "We can test simple, over-the-counter antiplatelet agents to really improve immunity and make a difference in how to treat people with cancer." Founded in 1824 in Charleston, The Medical University of South Carolina is the oldest medical school in the South. Today, MUSC continues the tradition of excellence in education, research, and patient care. MUSC educates and trains more than 3,000 students and residents in six colleges (Dental Medicine, Graduate Studies, Health Professions, Medicine, Nursing, and Pharmacy), and has nearly 13,000 employees, including approximately 1,500 faculty members. As the largest non-federal employer in Charleston, the university and its affiliates have collective annual budgets in excess of $2.2 billion, with an annual economic impact of more than $3.8 billion and annual research funding in excess of $250 million. MUSC operates a 700-bed medical center, which includes a nationally recognized children's hospital, the Ashley River Tower (cardiovascular, digestive disease, and surgical oncology), Hollings Cancer Center (a National Cancer Institute-designated center), Level I Trauma Center, Institute of Psychiatry, and the state's only transplant center. In 2016, U.S. News & World Report named MUSC Health the number one hospital in South Carolina. For more information on academic programs or clinical services, visit musc.edu. For more information on hospital patient services, visit muschealth.org.


Devaud C.,University of Melbourne | Devaud C.,Cancer Immunology Research Program | Darcy P.K.,University of Melbourne | Darcy P.K.,Monash University | And 3 more authors.
Cancer Immunology, Immunotherapy | Year: 2014

Forkhead box P3 (Foxp3) is an important transcription factor that belongs to the forkhead/winged-helix family of transcriptional regulators. Foxp3 has been extensively studied over the past 13 years as a master regulator of transcription in a specific T-cell type, CD4+ regulatory T cells (Treg), both in humans and in mice. Compelling data characterize Foxp3 as critically important and necessary for the development and the differentiation of Treg. It has been considered initially as the only specific marker for Treg. However, recent work has proposed that Foxp3 can be expressed by other types of lymphoid cells or myeloid cells and also by some non-hematopoietic cells such as epithelial cells. It remains controversial about the expression of Foxp3 in cells other than Treg, but understanding the potential expression and function of this master regulator in different cell subsets could have a wide range of implications for immune tolerance and several pathologies including autoimmune disorders and immune responses to cancer. © 2014 Springer-Verlag.


Amos S.M.,Cancer Immunology Research Program | Pegram H.J.,Cancer Immunology Research Program | Westwood J.A.,Cancer Immunology Research Program | John L.B.,Cancer Immunology Research Program | And 12 more authors.
Cancer Immunology, Immunotherapy | Year: 2011

Toll-like receptor (TLR) agonists can trigger broad inflammatory responses that elicit rapid innate immunity and promote the activities of lymphocytes, which can potentially enhance adoptive immunotherapy in the tumor-bearing setting. In the present study, we found that Polyinosinic:Polycytidylic Acid [Poly(I:C)] and CpG oligodeoxynucleotide 1826 [CpG], agonists for TLR 3 and 9, respectively, potently activated adoptively transferred T cells against a murine model of established melanoma. Intratumoral injection of Poly(I:C) and CpG, combined with systemic transfer of activated pmel-1 T cells, specific for gp10025-33, led to enhanced survival and eradication of 9-day established subcutaneous B16F10 melanomas in a proportion of mice. A series of survival studies in knockout mice supported a key mechanistic pathway, whereby TLR agonists acted via host cells to enhance IFN-γ production by adoptively transferred T cells. IFN-γ, in turn, enhanced the immunogenicity of the B16F10 melanoma line, leading to increased killing by adoptively transferred T cells. Thus, this combination approach counteracted tumor escape from immunotherapy via downregulation of immunogenicity. In conclusion, TLR agonists may represent advanced adjuvants within the setting of adoptive T-cell immunotherapy of cancer and hold promise as a safe means of enhancing this approach within the clinic. © 2011 Springer-Verlag.


Duong C.P.M.,Cancer Immunology Research Program | Duong C.P.M.,University of Melbourne | Yong C.S.M.,Cancer Immunology Research Program | Yong C.S.M.,University of Melbourne | And 8 more authors.
Molecular Immunology | Year: 2015

The immune system plays a critical role in the elimination and suppression of pathogens. Although the endogenous immune system is capable of immune surveillance resulting in the elimination of cancer cells, tumor cells have developed a variety of mechanisms to escape immune recognition often resulting in tumor outgrowth. The presence of immune infiltrate in tumors has been correlated with a good prognosis following treatment (. Sato et al., 2005; Loi et al., 2013; Clemente et al., 1996; Galon et al., 2006). As such, immune cells such as T cells, have been harnessed in order to target cancer. Tumor reactive lymphocytes, called tumor-infiltrating lymphocytes (TILs) have been isolated and expanded from the tumor and reinfused back into patients for the treatment of melanoma. The promise of adoptive immunotherapy utilizing TILs as a robust treatment for cancer has been highlighted in patients with advanced melanoma with greater than 50% of patients responding to treatment (. Dudley et al., 2005). Although TIL therapy has shown promising results in melanoma patients, it has proved difficult to translate this approach to other cancers, given that the numbers of TILs that can be isolated are generally low. To broaden this therapy for other cancers, T cells have been genetically modified to endow them with tumor reactivity using either a T cell receptor (TCR) (. Parkhurst et al., 2009, 2011; Chinnasamy et al., 2011) or a chimeric antigen receptor (CAR) (. Grupp et al., 2013; Park et al., 2007). This review will outline the origins and development of adoptive immunotherapy utilizing TILs leading to genetic modification strategies to redirect T cells to cancer. Potential hurdles and novel strategies will be discussed for realizing the full potential of adoptive immunotherapy becoming a standard of care treatment for cancer. © 2014 Elsevier Ltd.


Amos S.M.,Cancer Immunology Research Program | Duong C.P.M.,Cancer Immunology Research Program | Westwood J.A.,Cancer Immunology Research Program | Ritchie D.S.,Peter MacCallum Cancer Center | And 7 more authors.
Blood | Year: 2011

In this age of promise of new therapies for cancer, immunotherapy is emerging as an exciting treatment option for patients. Vaccines and cytokines are being tested extensively in clinical trials, and strategies using monoclonal antibodies and cell transfer are mediating dramatic regression of tumors in patients with certain malignancies. However, although initially advocated as being more specific for cancer and having fewer side effects than conventional therapies, it is becoming increasingly clear that many immunotherapies can lead to immune reactions against normal tissues. Immunotoxicities resulting from treatment can range from relatively minor conditions, such as skin depigmentation, to severe toxicities against crucial organ systems, such as liver, bowel, and lung. Treatment-related toxicity has correlated with better responses in some cases, and it is probable that serious adverse events from immune-mediated reactions will increase in frequency and severity as immunotherapeutic approaches become more effective. This review introduces immunotherapeutic approaches to cancer treatment, provides details of toxicities arising from therapy, and discusses future potential ways to avoid or circumvent these side effects. © 2011 by The American Society of Hematology.


Duong C.P.,Cancer Immunology Research Program | Westwood J.A.,Cancer Immunology Research Program | Berry L.J.,Cancer Immunology Research Program | Darcy P.K.,Cancer Immunology Research Program | And 5 more authors.
Immunotherapy | Year: 2011

Adoptive immunotherapy is a promising approach for the treatment of cancer; however, autoimmunity against normal tissue can be a serious complication of this therapy. We hypothesized that T-cell cultures responding maximally only when engaging two antigens would be more specific for tumor cells, and less active against normal cells, as long as the tumor expressed both antigens, while normal cells expressed only one of the antigens. A model system was developed consisting of cell lines expressing either folate binding protein or erbB-2, representing 'normal tissue, and cells expressing both antigens representing tumor tissue. Human T-cell cultures were produced using two chimeric antigen receptor vectors ('dual transduced), or using a single chimeric antigen receptor vector (monospecific). Dual-transduced T cells responded less against 'normal cells compared with tumor cells. This relatively simple procedure produced T-cell cultures that were as active against a tumor as the monospecific cultures used traditionally, but had lower activity against model normal cells.


Pegram H.J.,Cancer Immunology Research Program | Andrews D.M.,Cancer Immunology Research Program | Smyth M.J.,Cancer Immunology Research Program | Darcy P.K.,Cancer Immunology Research Program | Kershaw M.H.,Cancer Immunology Research Program
Immunology and Cell Biology | Year: 2011

Natural killer (NK) cells are potent immune effector cells that can respond to infection and cancer, as well as allowing maternal adaptation to pregnancy. In response to malignant transformation or pathogenic invasion, NK cells can secrete cytokine and may be directly cytolytic, as well as exerting effects indirectly through other cells of the immune system. To recognize and respond to inflamed or infected tissues, NK cells express a variety of activating and inhibitory receptors including NKG2D, Ly49 or KIR, CD94-NKG2 heterodimers and natural cytotoxicity receptors, as well as co-stimulatory receptors. These receptors recognize cellular stress ligands as well as major histocompatibility complex class I and related molecules, which can lead to NK cell responses. Importantly, NK cells must remain tolerant of healthy tissue, and some of these receptors can also prevent activation of NK cells. In this review, we describe the expression of prominent NK cell receptors, as well as expression of their ligands and their role in immune responses. In addition, we describe the main signaling pathways used by NK cell receptors. Although we now appreciate that NK cell biology is more complicated than first thought, there are still facets of their biology that remain unclear. These will be highlighted and discussed in this review. © 2011 Australasian Society for Immunology Inc. All rights reserved.


Stewart T.J.,Cancer Immunology Research Program | Smyth M.J.,Cancer Immunology Research Program
Cancer and Metastasis Reviews | Year: 2011

The status of a host's immune response influences both the development and progression of a malignancy such that immune responses can have both pro- and anti-tumorigenic effects. Cancer immunotherapy is a form of treatment that aims to improve the ability of a cancer-bearing individual to reject the tumor immunologically. However, antitumor immunity elicited by the host or by immunotherapeutic strategies, can be actively attenuated by mechanisms that limit the strength and/or duration of immune responses, including the presence of immunoregulatory cell types or the production of immunosuppressive factors. As our knowledge of tumor-induced immune suppression increases, it has become obvious that these mechanisms are probably a major barrier to effective therapy. The identification of multiple mechanisms of tumor-induced immune suppression also provides a range of novel targets for new cancer therapies. Given the vital role that a host's immune response is known to play in cancer progression, therapies that target immune suppressive mechanisms have the potential to enhance anticancer immune responses thus leading to better immune surveillance and the limitation of tumor escape. In this review, mechanisms of tumor-associated immune suppression have been divided into four forms that we have designated as (1) regulatory cells; (2) cytokines/chemokines; (3) T cell tolerance/exhaustion and (4) metabolic. We discuss select mechanisms representing each of these forms of immunosuppression that have been shown to aid tumors in evading host immune surveillance and overview therapeutic strategies that have been recently devised to "suppress these suppressors." © 2011 Springer Science+Business Media, LLC.


Li M.,Cancer Immunology Research Program | Knight D.A.,Cancer Immunology Research Program | Smyth M.J.,Cancer Immunology Research Program | Stewart T.J.,Cancer Immunology Research Program
Cancer Immunology, Immunotherapy | Year: 2012

Cancer stem cells (CSC) are resistant to radiation and chemotherapy and play a significant role in cancer recurrence and metastatic disease. It is therefore important to identify alternative strategies, such as immunotherapies that can be used to control this refractory population. A CD44?CD24-/low subpopulation of cells within the B6 PyMT-MMTV transgenic mouse-derived AT-3 mammary carcinoma cell line was identified, which had CSC-like characteristics, including pluripotency and a resistance to chemo- and radiotherapy. Therefore, unlike xenograph models that require immunocompromised settings, this novel system may provide a means to study immune-mediated responses against CSC-like cells. The immunobiology of the AT-3 CSC-like cell population was studied by their surface molecule expression profile and their sensitivity to specified cell death pathways. Comparable levels of Rae-1, CD155, CD54 and higher levels of Fas and DR5 were expressed on the AT-3 CSC-like cells compared to non-CSC-like tumor cells. Expression correlated with an in vitro sensitivity to cell death by NK cells or through the ligation of the death receptors (Fas or DR5), by their ligands or anti-Fas and anti-DR5 mAbs. Indeed, compared to the rest of the AT-3 tumor cells, the CD44?CD24-/low subpopulation of cells were more sensitive to both Fas- and TRAIL-mediated cell death pathways. Therefore, despite the refractory nature of CSC to other conventional therapies, these CSC-like cells were not inherently resistant to specified forms of immune-mediated cell death. These results encourage the continued investigation into immunotherapeutic strategies as a means of controlling breast CSC, particularly through their cell death pathways. © Springer-Verlag 2012.


Westwood J.A.,Cancer Immunology Research Program | Kershaw M.H.,Cancer Immunology Research Program | Kershaw M.H.,University of Melbourne
Journal of Leukocyte Biology | Year: 2010

Adoptive immunotherapy can induce dramatic tumor regressions in patients with melanoma or viral-induced malignancies, but extending this approach to many common cancers has been hampered by a lack of naturally occurring tumor-specific T cells. In this review, we describe recent advances in the genetic modification of T cells using genes encoding cell-surface receptors specific for tumor-associated antigen. Using genetic modification, the many functional properties of T cells, including cytokine secretion and cytolytic capacity, are redirected from their endogenous specificity toward the elimination of tumor cells. Advances in gene design, vectors, and cell production are discussed, and details of the progress in clinical application of this approach are provided. © Society for Leukocyte Biology.

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