Immunotherapy opportunities in ovarian cancer

Ovarian cancer is responsible for the majority of gynecologic cancer deaths and despite the highest standard of multimodality therapy with surgery and cytotoxic chemotherapy, long-term survival remains low. With compelling evidence that epithelial ovarian cancer is an immunogenic tumor capable of stimulating an antitumor immune response, renewed efforts to develop immune therapies to augment the efficacy of traditional therapies are underway. Current immunotherapies focus on varied modes of antitumor vaccine development, particularly with the use of dendritic cell vaccines, effective methods for adoptive T-cell transfer and combinatorial approaches with immune modulatory therapy subverting natural tolerance mechanisms or boosting effector mechanisms. Additional combinatorial approaches include the use of cytokines and/or chemotherapy with immune therapy.     

Immunotherapy opportunities in ovarian cancer

Ovarian cancer is responsible for the majority of gynecologic cancer deaths and despite the highest standard of multimodality therapy with surgery and cytotoxic chemotherapy, long-term survival remains low. With compelling evidence that epithelial ovarian cancer is an immunogenic tumor capable of stimulating an antitumor immune response, renewed efforts to develop immune therapies to augment the efficacy of traditional therapies are underway. Current immunotherapies focus on varied modes of antitumor vaccine development, particularly with the use of dendritic cell vaccines, effective methods for adoptive T-cell transfer and combinatorial approaches with immune modulatory therapy subverting natural tolerance mechanisms or boosting effector mechanisms. Additional combinatorial approaches include the use of cytokines and/or chemotherapy with immune therapy.     

Cytokine-induced senescence for cancer surveillance

The immune response is a first-line systemic defense to curb tumorigenesis and metastasis. Much effort has been invested to design antitumor interventions that would boost the immune system in its fight to defeat or contain cancerous growth. Tumor vaccination protocols, transfer of tumor-associated-antigen-specific T cells, T cell activity-regulating antibodies, and recombinant cytokines are counted among a toolbox filled with immunotherapeutic options. Although the mechanistic underpinnings of tumor immune control remain to be deciphered, these are studied with the goal of cancer cell destruction. In contrast, tumor dormancy is considered as a dangerous equilibrium between cell proliferation and cell death. There is, however, emerging evidence that tumor immune control can be achieved in the absence of overt cancer cell death. Here, we propose cytokine-induced senescence (CIS) by transfer of T helper-1 cells (T_H1) or by recombinant cytokines as a novel therapeutic intervention for cancer treatment. Immunity-induced senescence triggers a stable cell cycle arrest of cancer cells. It engages the immune system to construct defensive, isolating barriers around tumors, and prevents tumor growth through the delivery or induction of T_H1-cytokines in the tumor microenvironment. Keeping cancer cells in a non-proliferating state is a strategy, which directly copes with the lost homeostasis of aggressive tumors. As most studies show that even after efficient cancer therapies minimal residual disease persists, we suggest that therapies should include immune-mediated senescence for cancer surveillance. CIS has the goal to control the residual tumor and to transform a deadly disease into a state of silent tumor persistence.     

Granulocyte-macrophage colony-stimulating factor (GM-CSF) secreted by cDNA-transfected tumor cells induces a more potent antitumor response than exogenous GM-CSF

Clinical cancer gene therapy trials have generally focused on the transfer of cytokine cDNA to tumor cells ex vivo and with the subsequent vaccination of the patient with these genetically altered tumor cells. This approach results in high local cytokine concentrations that may account for the efficacy of this technique in animal models. We hypothesized that the expression of certain cytokines by tumor cells would be a superior immune stimulant when compared with local delivery of exogenous cytokines. Granulocyte-macrophage colony-stimulating factor (GM-CSF) cDNA in a nonviral expression vector was inserted into MDA-MB-231 (human breast cancer), M21 (human melanoma), B16 (murine melanoma), and P815 (mastocytoma) cells by particle-mediated gene transfer. The ability of transfected tumor cells to generate a tumor-specific immune response was evaluated in an in vitro mixed lymphocyte-tumor cell assay and in an in vivo murine tumor protection model. Peripheral blood lymphocytes cocultured with human GM-CSF-transfected tumor cells were 3- to 5-fold more effective at lysis of the parental tumor cells than were peripheral blood lymphocytes incubated with irradiated tumor cells and exogenous human GM-CSF. Mice immunized with murine GM-CSF-transfected irradiated B16 murine melanoma cells or P815 mastocytoma cells were protected from subsequent tumor challenge, whereas mice immunized with the nontransfected tumors and cutaneous transfection of murine GM-CSF cDNA at the vaccination site developed tumors more frequently. The results indicate that GM-CSF protein expressed in human and murine tumor cells is a superior antitumor immune stimulant compared with exogenous GM-CSF in the tumor microenvironment.     

卵巢癌患者化疗及减瘤手术对机体免疫功能影响的研究进展

卵巢癌作为免疫相关性肿瘤,可通过特殊的免疫抑制微环境促进肿瘤生长。随着研究的进展可以发现,以铂类为基础的化疗方案,可以诱导卵巢癌肿瘤微环境中淋巴细胞,尤其是CD8+T细胞的浸润与活化、减少肿瘤内调节性T细胞浸润,提高抗原提呈细胞的功能促进抗肿瘤免疫。上调免疫检查点抑制分子的表达,促进免疫抑制形成,调节细胞因子网络,破坏导致肿瘤生长的炎症环境,提高外周淋巴细胞的抗肿瘤活性等。而手术也通过直接减少肿瘤负荷、增加肿瘤微环境中淋巴细胞的浸润对机体免疫产生调节作用。针对一线治疗方案对抗肿瘤免疫产生的积极作用,在卵巢癌治疗过程中加强机体免疫功能变化的检测,或许能对治疗方案的制定提供帮助。     

Immunotherapy with cytokine gene-transduced tumor cells: the next wave in gene therapy for cancer.

Recently, new tumor vaccine approaches were developed in animal systems that modify tumor cells genetically to secrete certain cytokines. Engineering tumor cells to secrete cytokines in a paracrine fashion can induce powerful local cytokine effects without producing significant systemic toxicity. In addition to local inflammation, this approach can alter the presentation of tumor antigens or activation of tumor antigen-specific T lymphocytes, resulting in systemic antitumor immunity. The development of high efficiency gene transfer technologies such as defective retroviral vectors allows for the translation of these preclinical studies to clinical trials. However, before large investments are made in this area of gene therapy, it will be important to demonstrate that the actual gene transfer component of the strategy significantly enhances antitumor immune responses relative to alternative nongenetic approaches.     

Antibody-directed, effector cell-mediated tumor destruction.

Preclinical and clinical development of antitumor strategies using mAbs are showing antitumor efficacy in animal models and in some clinical settings. Preclinical models suggest that mAb treatment would be most effective when provided in the minimal residual disease setting and can involve mAbs in a variety of roles. In murine models, the combination of mAbs with recombinant cytokines, such as IL-2, IL-12, or GM-CSF, can augment the immunologic effect of the mAbs by activating effector cell functions. Efficacy appears to be greatest when the mAb can recruit the effector cells of the host's immune system into helping in the mediation of the antitumor effect. Clinical testing of these concepts is under way.     

Immunobiology and immunotherapy of head and neck cancer

The development of head and neck cancer (HNC) is strongly influenced by the host immune system. Immunoselection of tumors resistant to immune attack and the ability of established tumors to disarm or eliminate immune cells favor tumor progression. Recent evidence for local as well as systemic apoptosis of T lymphocytes, the paucity of dendritic cells (DC) at the tumor site, or the presence of signaling defects in T lymphocytes of patients with HNC emphasizes the fact that their antitumor responses are compromised. The clinical and biologic importance of these immune biomarkers is revealed by the finding that they appear to independently predict 5-year survival in patients with oral carcinoma. Whereas the mechanisms responsible for immune dysfunction in HNC are being investigated, new immunotherapeutic strategies, including antitumor vaccines and DC-based interventions, aim at the restoration of tumor-targeted immune responses. These novel biologic therapies, alone or in combination with conventional therapies, might be expected to protect immune cells from dysfunction or death and to enhance their antitumor activity.     

Impact of chemotherapeutic agents on the immunostimulatory properties of human 6‐sulfo LacNAc+ (slan) dendritic cells

Chemotherapy is an important treatment modality for many patients with advanced cancer. Recent data revealed that certain chemotherapeutic agents differentially affect maturation, cytokine production and T‐cell stimulatory capacity of dendritic cells (DCs), which play a crucial role in the induction of antitumor immunity. Whereas most reports are based on mouse or human monocyte‐derived DCs, studies investigating the direct effect of chemotherapeutic drugs on native human DCs are rather limited. Here, we evaluated the impact of various chemotherapeutic drugs on the immunostimulatory properties of 6‐sulfo LacNAc⁺ (slan) DCs, representing a major subpopulation of human blood DCs. Because of their various antitumor effects, slanDCs may essentially contribute to the immune defense against tumors. We demonstrated that doxorubicin and vinblastine significantly impair the release of tumor necrosis factor‐α, interleukin (IL)‐6 and IL‐12 by slanDCs. Functional data revealed that both drugs inhibit slanDC‐mediated proliferation of T lymphocytes and their capacity to differentiate naive CD4⁺ T cells into proinflammatory T‐helper type I cells. Furthermore, these agents markedly suppressed the ability of slanDCs to stimulate interferon‐γ secretion by natural killer (NK) cells. In contrast, paclitaxel, mitomycin C and methotrexate sustained the ability of slanDCs to produce proinflammatory cytokines and their potential to activate T‐lymphocytes and NK cells. These results indicate that doxorubicin and vinblastine impair the ability of native human DCs to stimulate important immune effector cells, whereas methotrexate, mitomycin C and paclitaxel maintain their immunostimulatory properties. These novel findings may have implications for the design of treatment modalities for tumor patients combining immunotherapeutic strategies and chemotherapy.     

Intratumoral cytokines/chemokines/growth factors and tumor infiltrating dendritic cells: friends or enemies?

The tumor microenvironment consists of a variable combination of tumor cells, stromal fibroblasts, endothelial cells and infiltrating leukocytes, such as macrophages, T lymphocytes, and dendritic cells. A variety of cytokines, chemokines and growth factors are produced in the local tumor environment by different cells accounting for a complex cell interaction and regulation of differentiation, activation, function and survival of multiple cell types. The interaction between cytokines, chemokines, growth factors and their receptors forms a comprehensive network at the tumor site, which is primary responsible for overall tumor progression and spreading or induction of antitumor immune responses and tumor rejection. Although the general thought is that dendritic cells are among the first cells migrating to the tumor site and recognizing tumor cells for the induction of specific antitumor immunity, the clinical relevance of dendritic cells at the site of the tumor remains a matter of debate regarding their role in the generation of successful antitumor immune responses in human cancers. While several lines of evidence suggest that intratumoral dendritic cells play an important role in antitumor immune responses, understanding the mechanisms of dendritic cell/tumor cell interaction and modulation of activity and function of different dendritic cell subtypes at the tumor site is incomplete. This review is limited to discussing the role of intratumoral cytokine network in the understanding immunobiology of tumor-associated dendritic cells, which seems to possess different regulatory functions at the tumor site.     

Extravasation of antitumor effector cells.

Development of effective local immune responses depends on the ability of lymphocytes to extravasate and migrate into nonlymphoid solid tissues. Different lymphocyte subpopulations seem to vary in their abilities to extravasate. In this review, recent advances made in understanding lymphocyte extravasation, interactions between lymphocytes and vascular endothelial cells, receptors on lymphocytes which are involved in their movement through the extracellular matrix, and cytokines, which regulate lymphocyte mobility through tissue, are described. In pathologic conditions, lymphocyte extravasation may be compromised, and delivery of immune effector cells to the site of injury is an important therapeutic end point. Adoptive therapy of solid tumors with antitumor effector cells depends on their successful delivery to the tumor. Although parameters which determine this delivery are not yet defined, considerable progress has been made in studies of the mechanisms involved in lymphocyte movement through tissues.     

The immunotherapy and cellular biology of renal cell carcinoma

It is clear from the work presented at this symposium that immunotherapy has joined surgery, chemotherapy, and radiation as the next generation of treatment for at least some human malignancies. Several problems remain to be addressed before the use of immunotherapy is optimized, including: (1) understanding the genetic and cellular growth control mechanisms gone awry in the development and progression of RCC; (2) defining the mechanisms by which antitumor lymphocytes are cytotoxic; (3) establishing an inexpensive and less labor-intensive way of identifying and isolating the most active antitumor lymphocytes from LAK cells and TILs; (4) designing methods to optimize delivery of effector cells to tumor beds; and (5) exploiting combinations of immune effectors and other therapies for improved killing of cells and lower toxicity. Answers to these problems will no doubt form the basis for future symposia.     

Targeting Toll-Like Receptors for Cancer Therapy

The immune system encompasses a broad array of defense mechanisms against foreign threats, including invading pathogens and transformed neoplastic cells. Toll-like receptors (TLRs) are critically involved in innate immunity, serving as pattern recognition receptors whose stimulation leads to additional innate and adaptive immune responses. Malignant cells exploit the natural immunomodulatory functions of TLRs, expressed mainly by infiltrating immune cells but also aberrantly by tumor cells, to foster their survival, invasion, and evasion of anti-tumor immune responses. An extensive body of research has demonstrated context-specific roles for TLR activation in different malignancies, promoting disease progression in certain instances while limiting cancer growth in others. Despite these conflicting roles, TLR agonists have established therapeutic benefits as anti-cancer agents that activate immune cells in the tumor microenvironment and facilitate the expression of cytokines that allow for infiltration of anti-tumor lymphocytes and the suppression of oncogenic signaling pathways. This review focuses on the clinical application of TLR agonists for cancer treatment. We also highlight agents that are undergoing development in clinical trials, including investigations of TLR agonists in combination with other immunotherapies.     

Glycolipid-anchored IL-12 expressed on tumor cell surface induces antitumor immune response

Systemic or local administration of cytokine has been used as a mode to enhance the antitumor immune response induced by many cancer vaccines. We have investigated whether the expression of cytokines on the tumor cell surface as a glycolipid (GPI)-anchored form will be effective in inducing antitumor immune response using a GPI-anchored interleukin (IL)-12 (GPI-IL-12) as a model. GPI-IL-12-induced the proliferation of concanavalin A-activated T cells and induced IFN-gamma secretion by activated and allogeneic T cells, indicating that the membrane-expressed IL-12 can stimulate T cells. GPI-IL-12 expressed on the tumor cell surface prevented tumor growth in mice in a highly tumorigenic murine mastocytoma model. These results suggest that the cell surface-expressed GPI-IL-12 can be effective in inducing antitumor immune response, and GPI-anchored cytokines expressed on the tumor cell surface may be a novel approach to deliver cytokines at the immunization site during vaccination against cancer. Furthermore, purified GPI-anchored cytokines can be used to quickly modify tumor membranes by the protein transfer method to express the desired cytokines for vaccine development.     

Prostate cancer vaccines: current status

Recent insights into cell-mediated immunotherapy have led to a wave of new trials involving immunotherapy for prostate cancer. Vaccines have evolved from nonspecific immune stimulants like Bacillus Calmette-Guerin (BCG) to much more specific and potent strategies. Techniques currently being investigated include passive immunotherapy with monoclonal antibodies, adoptive transfer of activated effector T cells, and active immunotherapy involving immunization with whole-cell or antigen-specific vaccines. These therapies are being modified with cytokines and other immune modulating agents. Understanding the mechanisms of antitumor immunity and identifying relevant tumor-specific antigens will likely improve these vaccine strategies and provide them with a niche in the future of prostate cancer therapy.     

Activated CTLA-4-independent immunosuppression of Treg cells disturbs CTLA-4 blockade-mediated antitumor immunity

Combination therapy with anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and anti-programmed death-1 (PD-1) monoclonal antibodies (mAbs) has dramatically improved the prognosis of patients with multiple types of cancer, including renal cell carcinoma (RCC). However, more than half of RCC patients fail to respond to this therapy. Regulatory T cells (Treg cells) are a subset of highly immunosuppressive CD4⁺ T cells that promote the immune escape of tumors by suppressing effector T cells in the tumor microenvironment (TME) through various mechanisms. CTLA-4 is constitutively expressed in Treg cells and is regarded as a key molecule for Treg-cell-mediated immunosuppressive functions, suppressing antigen-presenting cells by binding to CD80/CD86. Reducing Treg cells in the TME with an anti-CTLA-4 mAb with antibody-dependent cellular cytotoxicity (ADCC) activity is considered an essential mechanism to achieve tumor regression. In contrast, we demonstrated that CTLA-4 blockade without ADCC activity enhanced CD28 costimulatory signaling pathways in Treg cells and promoted Treg-cell proliferation in mouse models. CTLA-4 blockade also augmented CTLA-4-independent immunosuppressive functions, including cytokine production, leading to insufficient antitumor effects. Similar results were also observed in human peripheral blood lymphocytes and tumor-infiltrating lymphocytes from patients with RCC. Our findings highlight the importance of Treg-cell depletion to achieve tumor regression in response to CTLA-4 blockade therapies.     

TNFalpha contributes to the antitumor activity of a bispecific, trifunctional antibody

Immunological cancer therapies focus on the activation of immune effector cells yielding a specific antitumor activity. Disseminated tumor cells are regarded as the origin of metastases and consequently their elimination is the central objective of adjuvant immune therapies. The use of bispecific antibodies is an approach that is regarded as promising in order to fight those disseminated tumor cells. Unfortunately, the efficiency of these antibodies is limited by the fact that they usually activate a single class of effector cell, thus not yielding optimal immune response. In addition, tumor cells may down-regulate the antibody's target molecule and escape recognition. We have recently described results with an intact bispecific molecule, BiUII, that represents a new class of intact antibodies. These antibodies, termed "triomab", provide an excellent antitumor activity in vitro, a fact that most probably is attributable to the simultaneous activation of different classes of immune effector cells. We have now investigated this antitumor activity in more detail and demonstrate here that at least a dual mechanism accounts for triomab-mediated killing of tumor cells: besides direct cell-mediated killing, triomab induces the production of TNFalpha in PBMCs at concentrations that induce apoptosis in target cells. This bystander effect may be of special interest for the clinical application of triomab in terms of killing of target antigen-negative tumor cells.     

The immune system as anti-tumor sentinel: molecular requirements for an anti-tumor immune response.

The concept behind immune surveillance against cancer is that tumor cells continuously develop, but that there may not be clinical evidence of their presence because the immune system recognizes the cells as foreign and destroys them. A clear role for the immune system in preventing and/or eliminating tumors is emerging as insights into the molecular requirements for the induction and effector function of cytolytic T lymphocytes (CTL) have been gained. Using murine tumor rejection models, the role of particular molecular components of the immune system in controlling tumor growth has been defined. However, tumor rejection does not always occur spontaneously in vivo, indicating that defects in the generation or execution of an anti-tumor immune response may be common. Understanding defects when they arise should allow for development of new therapeutic approaches in tumor-bearing individuals. Many clinical studies are underway to test strategies to induce or heighten an antitumor immune response in cancer patients.     

New perspectives on complement mediated immunotherapy

Tumor-specific monoclonal antibodies (mAbs) offer several modes of tumor cell killing, from direct cytotoxic activity to indirect mechanisms employing the host immune system, particularly its innate branch. The latter effector functions seem to dominate among clinically approved anti-cancer mAbs and major efforts are being undertaken by both academia and the pharmaceutical industry with the aim to improve complement activation, antibody-dependent cellular cytotoxicity (ADCC) and Fc/opsonin-mediated phagocytosis. On one hand, there are a variety of available effector mechanisms to allow multistep elimination of tumor cells. On the other hand, tumor cells adopt a number of strategies to evade immune attack, such as overexpression of complement inhibitors, trogocytosis, shedding or internalization of mAb-targeted epitopes, which all contribute to their resistance against host defense mechanisms. Another problem recognized only recently is the depletion of immune effectors during the first round of treatment, which in concordance with delayed turnover of immune components renders subsequent rounds of therapy ineffective. Herein, we discuss newly identified limiting factors but also novel mechanistic data on complement activation by antitumor antibodies as issues important for guidance towards the next generations of immunotherapeutics.