Cancer. Cancer immunotherapy is more than a numbers game

Emerging Challenges to Cellular Therapy of Cancer

ABSTRACT

Cellular immunotherapy of cancer in the form of chimeric antigen receptor-modified T-cell therapy has become a standard treatment for lymphoid and more recently plasma cell malignancies. Although their successes in these cancers represent a breakthrough for adoptive cell therapy, there are several challenges to their continued growth in the field of cancer medicine. In this review, we discuss the progress made thus far toward achieving "off-the-shelf" accessibility of cell therapies that has the potential to greatly offset the costs associated with the current practice of making patient-specific products. We also review the innovations under investigation that attempt to make cellular therapy applicable to solid tumors as well.

Characterization of increasing stages of invasiveness identifies stromal/cancer cell crosstalk in rat models of mesothelioma

Sarcomatoid mesothelioma (SM) is a devastating cancer associated with one of the poorest outcome. Therefore, representative preclinical models reproducing different tumor microenvironments (TME) observed in patients would open up new prospects for the identification of markers and evaluation of innovative therapies. Histological analyses of four original models of rat SM revealed their increasing infiltrative and metastatic potential were associated with differences in Ki67 index, blood-vessel density, and T-lymphocyte and macrophage infiltration. In comparison with the noninvasive tumor M5-T2, proteomic analysis demonstrated the three invasive tumors F4-T2, F5-T1 and M5-T1 shared in common a very significant increase in the abundance of the multifunctional proteins galectin-3, prohibitin and annexin A5, and a decrease in proteins involved in cell adhesion, tumor suppression, or epithelial differentiation. The increased metastatic potential of the F5-T1 tumor, relative to F4-T2, was associated with an increased macrophage vs T-cell infiltrate, changes in the levels of expression of a panel of cytokine genes, an increased content of proteins involved in chromatin organization, ribosome structure, splicing, or presenting anti-adhesive properties, and a decreased content of proteins involved in protection against oxidative stress, normoxia and intracellular trafficking. The most invasive tumor, M5-T1, was characterized by a pattern of specific phenotypic and molecular features affecting the presentation of MHC class I-mediated antigens and immune cell infiltration, or involved in the reorganization of the cytoskeleton and composition of the extracellular matrix. These four preclinical models and data represent a new resource available to the cancer research community to catalyze further investigations on invasiveness.

More than a scaffold: Stromal modulation of tumor immunity

Current clinical success with anti-cancer immunotherapy provides exciting new treatment opportunities. While encouraging, more needs to be done to induce durable effects in a higher proportion of patients. Increasing anti-tumor effector T cell quantity or quality alone does not necessarily correlate with therapeutic outcome. Instead, the tumor microenvironment is a critical determinant of anti-cancer responsiveness to immunotherapy and can confer profound resistance. Yet, the tumor-promoting environment - due to its enormous plasticity - also delivers the best opportunities for adjuvant therapy aiming at recruiting, priming and sustaining anti-tumor cytotoxicity. While the tumor environment as an entity is increasingly well understood, current interventions are still broad and often systemic. In contrast, tumors grow in a highly compartmentalized environment which includes the vascular/perivascular niche, extracellular matrix components and in some tumors lymph node aggregates; all of these structures harbor and instruct subsets of immune cells. Targeting and re-programming specific compartments may provide better opportunities for adjuvant immunotherapy.

Axitinib increases the infiltration of immune cells and reduces the suppressive capacity of monocytic MDSCs in an intracranial mouse melanoma model

Melanoma patients are at a high risk of developing brain metastases, which are strongly vascularized and therefore have a significant risk of spontaneous bleeding. VEGF not only plays a role in neo-angiogenesis but also in the antitumor immune response. VEGFR-targeted therapy might not only have an impact on the tumor vascularization but also on tumor-infiltrating immune cells. In this study, we investigated the effect of axitinib, a small molecule TKI of VEGFR-1, -2, and -3, on tumor growth and on the composition of tumor-infiltrating immune cells in subcutaneous and intracranial mouse melanoma models. In vivo treatment with axitinib induced a strong inhibition of tumor growth and significantly improved survival in both tumor models. Characterization of the immune cells within the spleen and tumor of tumor-bearing mice respectively showed a significant increase in the number of CD3⁺CD8⁺ T cells and CD11b⁺ cells of axitinib-treated mice. More specifically, we observed a significant increase of intratumoral monocytic myeloid-derived suppressor cells (moMDSCs; CD11b⁺Ly6C^highLy6G^-). Interestingly, in vitro proliferation assays showed that moMDSCs isolated from spleen or tumor of axitinib-treated mice had a reduced suppressive capacity on a per cell basis as compared to those isolated from vehicle-treated mice. Moreover, MDSCs from axitinib-treated animals displayed the capacity to stimulate allogeneic T cells. Thus, treatment with axitinib induces differentiation of moMDSC toward an antigen-presenting phenotype. Based on these observations, we conclude that the impact of axitinib on tumor growth and survival is most likely not restricted to direct anti-angiogenic effects but also involves important effects on tumor immunity.

Vascular normalizing doses of antiangiogenic treatment reprogram the immunosuppressive tumor microenvironment and enhance immunotherapy

The recent approval of a prostate cancer vaccine has renewed hope for anticancer immunotherapies. However, the immunosuppressive tumor microenvironment may limit the effectiveness of current immunotherapies. Antiangiogenic agents have the potential to modulate the tumor microenvironment and improve immunotherapy, but they often are used at high doses in the clinic to prune tumor vessels and paradoxically may compromise various therapies. Here, we demonstrate that targeting tumor vasculature with lower vascular-normalizing doses, but not high antivascular/antiangiogenic doses, of an anti-VEGF receptor 2 (VEGFR2) antibody results in a more homogeneous distribution of functional tumor vessels. Furthermore, lower doses are superior to the high doses in polarizing tumor-associated macrophages from an immune inhibitory M2-like phenotype toward an immune stimulatory M1-like phenotype and in facilitating CD4(+) and CD8(+) T-cell tumor infiltration. Based on this mechanism, scheduling lower-dose anti-VEGFR2 therapy with T-cell activation induced by a whole cancer cell vaccine therapy enhanced anticancer efficacy in a CD8(+) T-cell-dependent manner in both immune-tolerant and immunogenic murine breast cancer models. These findings indicate that vascular-normalizing lower doses of anti-VEGFR2 antibody can reprogram the tumor microenvironment away from immunosuppression toward potentiation of cancer vaccine therapies. Given that the combinations of high doses of bevacizumab with chemotherapy have not improved overall survival of breast cancer patients, our study suggests a strategy to use antiangiogenic agents in breast cancer more effectively with active immunotherapy and potentially other anticancer therapies.

IL-12 delivered intratumorally by multilamellar liposomes reactivates memory T cells in human tumor microenvironments

Using a novel loading technique, IL-12 is reported here to be efficiently encapsulated within large multilamellar liposomes. The preclinical efficacy of the cytokine loaded liposomes to deliver IL-12 into human tumors and to reactive tumor-associated T cells in situ is tested using a human tumor xenograft model. IL-12 is released in vivo from these liposomes in a biologically active form when injected into tumor xenografts that are established by the subcutaneous implantation of non-disrupted pieces of human lung, breast or ovarian tumors into immunodeficient mice. The histological architecture of the original tumor tissue, including tumor-associated leukocytes, tumor cells and stromal cells is preserved anatomically and the cells remain functionally responsive to cytokines in these xenografts. The local and sustained release of IL-12 into the tumor microenvironment reactivates tumor-associated quiescent effector memory T cells to proliferate, produce and release IFN-gamma resulting in the killing of tumor cells in situ. Very little IL-12 is detected in the serum of mice for up to 5 days after an intratumoral injection of the IL-12 liposomes. We conclude that IL-12 loaded large multilamellar liposomes provide a safe method for the local and sustained delivery of IL-12 to tumors and a therapeutically effective way of reactivating existing tumor-associated T cells in human solid tumor microenvironments. The potential of this local in situ T cell re-stimulation to induce a systemic anti-tumor immunity is discussed.

The anti-tumor effect of human monocyte-derived dendritic cells loaded with HSV-TK/GCV induced dying cells

Herpes simplex virus thymidine kinase (HSV-TK) gene and dendritic cells (DC) have been used as the pioneering in cancer therapy. HSV-TK gene can induce apoptosis and necrosis in tumor cells in the presence of the non-toxic prodrug ganciclovir (GCV). We investigated the anti-tumor effect of DC vaccination by introducing dying cells from HSV-TK gene treatment as an adjuvant. HepG(2)-TK cell line was established by transfecting human hepatoma cell line HepG(2) (HLA-A(2) positive) with HSV-TK gene. Dying tumor cells were generated by culturing HepG(2)-TK cells with GCV. After engulfed dying cells efficiently, immature DCs (imDC) derived from human monocytes were fully matured and elicited marked proliferation and cytotoxicity against HLA matched HepG(2) cells in autologous peripheral blood mononuclear cells (PBMC). It also implied that HepG(2) specific CTLs played an important role in the cytotoxicity which was primarily depended on Th1 responses. Given the feasibility of inducing dying cells by HSV-TK/GCV in vivo, our results suggest an effective method in clinical human hepatocellular carcinoma (HCC) treatment by an in vitro model of applying HSV-TK gene modified human tumor cells integrated with DC vaccination.

Interleukin-15/interleukin-15R alpha complexes promote destruction of established tumors by reviving tumor-resident CD8+ T cells

Tumors often escape immune-mediated destruction by suppressing lymphocyte infiltration or effector function. New approaches are needed that overcome this suppression and thereby augment the tumoricidal capacity of tumor-reactive lymphocytes. The cytokine interleukin-15 (IL-15) promotes proliferation and effector capacity of CD8(+) T cells, natural killer (NK) cells, and NKT cells; however, it has a short half-life and high doses are needed to achieve functional responses in vivo. The biological activity of IL-15 can be dramatically increased by complexing this cytokine to its soluble receptor, IL-15R alpha. Here, we report that in vivo delivery of IL-15/IL-15R alpha complexes triggers rapid and significant regression of established solid tumors in two murine models. Despite a marked expansion of IL-2/IL-15R beta(+) cells in lymphoid organs and peripheral blood following treatment with IL-15/IL-15R alpha complexes, the destruction of solid tumors was orchestrated by tumor-resident rather than newly infiltrating CD8(+) T cells. Our data provide novel insights into the use of IL-15/IL-15R alpha complexes to relieve tumor-resident T cells from functional suppression by the tumor microenvironment and have significant implications for cancer immunotherapy and treatment of chronic infections.

Anti-inflammatory pretreatment enables an efficient dendritic cell-based immunotherapy against established tumors

Although animals can be immunized against the growth of some tumor implants, most of the attempts to use immunotherapy to cause the regression of animal and human tumors once they have become established have been disappointing even when strongly immunogenic tumors were used as target. In this paper, we demonstrate that the failure to achieve an efficient immunological treatment against an established strongly immunogenic murine fibrosarcoma was paralleled with the emergence of a state of immunological unresponsiveness (immunological eclipse) against tumor antigens observed when the tumor surpassed the critical size of 500 mm(3). In turn, the onset of the immunological eclipse was coincidental with the onset of a systemic inflammatory condition characterized by a high number of circulating and splenic polymorphonucleated neutrophils (PMN) displaying activation and Gr1(+)Mac1(+) phenotype and an increasing serum concentration of the pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6 cytokines and C-reactive protein (CRP) and serum A amyloid (SAA) phase acute proteins. Treatment of tumor-bearing mice with a single low dose (0.75 mg/kg) of the synthetic corticoid dexamethasone (DX) significantly reduced all the systemic inflammatory parameters and simultaneously reversed the immunological eclipse, as evidenced by the restoration of specific T-cell-dependent concomitant immunity, ability of spleen cells to transfer anti-tumor activity and recovery of T-cell signal transduction molecules. Two other anti-inflammatory treatments by using indomethacin or dimeric TNF-alpha receptor, also partially reversed the immunological eclipse although the effect was not as striking as that observed with DX. The reversion of the immunological eclipse was not enough on its own to inhibit the primary growing tumor. However, when we used the two-step strategy of inoculating DX to reverse the eclipse and then dendritic cells loaded with tumor antigens (DC) as an immunization booster, a significant inhibition of the growth of both established tumors and remnant tumor cells after excision of large established tumors was observed, despite the fact that the vaccination alone (DC) had no effect or even enhanced tumor growth in certain circumstances. The two-step strategy of tumor immunotherapy that we present is based on the rationale that it is necessary to eliminate or ameliorate the immunological eclipse as a precondition to allow an otherwise ineffective anti-tumor immunological therapy to have a chance to be successful.

Therapeutic anti-tumor vaccines: from tumor inhibition to enhancement

Numerous immunization trials have proved successful in preventing the growth of experimental animal tumors and human hepatocarcinomas induced by hepatitis B virus. These results have prompted researchers and physicians to use vaccines in a therapeutic mode but the results have, in general, been disappointing even when strongly immunogenic murine tumors were concerned. Data presented herein suggest that immunotherapy induced by a single dose of a dendritic cell-based vaccine against a murine established tumor or against residual tumor cells after debulking the primary tumor, can render not only inhibitory or null but also stimulatory effects on tumor growth. These different effects might be dependent on where the system is located in the immune response curve that relates the quantity of the immune response to the quantity of target tumor cells. We suggest that high ratios render tumor inhibition, medium and very low ratios render null effects and low ratios-between medium and very low ones-render tumor stimulation. Since the magnitude of these ratios would depend on the antigenic profile of the tumor, the immunogenic strength of the vaccine used and the immunological state of the host, studies aimed to determine the magnitude of these variables in each particular case, seem to be necessary as a pre-condition to design rational immunotherapeutic approaches to cancer. In contrast, if these studies are neglected, the worst thing that an immunotherapist could face is not merely a null effect but enhancement of tumor growth.

Prostate cancer: genes, environment, immunity and the use of immunotherapy

Prostate cancer remains the most prevalent noncutaneous cancer, leading to almost 30,000 deaths every year in men in the United States. A large body of knowledge emphasizes a strong influence of epidemiological factors such as lifestyle, environment and diet, on the development of prostate cancer. Although risk reduction of prostate cancer has been somewhat successful, effective prevention is still lacking. Immunotherapeutic approaches, although moderately complicated, remain promising in an effort to control the progression and development of the disease. Taken together, the parameters of epidemiological studies and immunotherapeutic regimens might eventually be the most effective and preventive approach for prostate cancer. This review highlights some of the events associated with the development and prevention of prostate cancer.

Lentiviral vectors encoding human immunodeficiency virus type 1 (HIV-1)-specific T-cell receptor genes efficiently convert peripheral blood CD8 T lymphocytes into cytotoxic T lymphocytes with potent in vitro and in vivo HIV-1-specific inhibitory activity

The human immunodeficiency virus type 1 (HIV-1)-specific CD8 cytotoxic T-lymphocyte (CTL) response plays a critical role in controlling HIV-1 replication. Augmenting this response should enhance control of HIV-1 replication and stabilize or improve the clinical course of the disease. Although cytomegalovirus (CMV) or Epstein-Barr virus (EBV) infection in immunocompromised patients can be treated by adoptive transfer of ex vivo-expanded CMV- or EBV-specific CTLs, adoptive transfer of ex vivo-expanded, autologous HIV-1-specific CTLs had minimal effects on HIV-1 replication, likely a consequence of the inherently compromised qualitative function of HIV-1-specific CTLs derived from HIV-1-infected individuals. We hypothesized that this limitation could be circumvented by using as an alternative source of HIV-1-specific CTLs, autologous peripheral CD8(+) T lymphocytes whose antigen specificity is redirected by transduction with lentiviral vectors encoding HIV-1-specific T-cell receptor (TCR) alpha and beta chains, an approach used successfully in cancer therapy. To efficiently convert peripheral CD8 lymphocytes into HIV-1-specific CTLs that potently suppress in vivo HIV-1 replication, we constructed lentiviral vectors encoding the HIV-1-specific TCR alpha and TCR beta chains cloned from a CTL clone specific for an HIV Gag epitope, SL9, as a single transcript linked with a self-cleaving peptide. We demonstrated that transduction with this lentiviral vector efficiently converted primary human CD8 lymphocytes into HIV-1-specific CTLs with potent in vitro and in vivo HIV-1-specific activity. Using lentiviral vectors encoding an HIV-1-specific TCR to transform peripheral CD8 lymphocytes into HIV-1-specific CTLs with defined specificities represents a new immunotherapeutic approach to augment the HIV-1-specific immunity of infected patients.

Tumor transfected with CCL21 enhanced reactivity and apoptosis resistance of human monocyte-derived dendritic cells

Chemokine CCL21 can effectively attract CCR7(+) dendritic cells (DCs), however its role in this event is poorly understood. In this report, we investigated the effect of exogenous CCL21 expressed in breast cancer MCF-7 on human monocyte-derived DCs. CCL21-transfected MCF-7 stimulation prompted DC functions: migration, antigen-uptake and presentation. The stimulated DCs facilitated Th1 type cytokines production, perforin-forming CD8(+) T cell transformation and final T cell-associated clearance of MCF-7. Moreover, the MCF-7-resourced CCL21 protected DCs from apoptosis significantly, involving up-regulations of Bcl-2 expression and NF-kappaB activity, and reduction of caspase-3. This study provides evidence that tumor-derived CCL21 increases the presentation and apoptosis resistance of DCs, suggesting such a mechanism may be useful for the improvement of tumor cell immunogenicity and anti-tumor response.

The immune system--is it relevant to cancer development, progression and treatment?

The ability of the immune system to effectively respond to human tumours is a matter of long-term controversy. There is an increasing body of recent evidence to support a role for the immune system in eliminating pre-clinical cancers, an old concept termed 'immunosurveillance'. 'Immunoediting' is an updated hypothesis, in which selection pressures applied by the immune response to tumours modulate tumour immunogenicity and growth. Tumour infiltration by immune cells has been shown to have powerful prognostic significance in a host of cancer types. Paradoxically, in some circumstances the immune system can promote tumour development. Cytotoxic therapies, including radiotherapy and chemotherapy, induce potentially immunogenic cell death, releasing tumour-associated antigens in the context of a 'danger' signal to the immune system. An understanding of the interaction between immune cells, tumour cells and treatment modalities will therefore guide the future combination of immunotherapy with conventional therapy to achieve optimal anti-tumour effects.

Immunodeficiency and immunotherapy in multiple myeloma

Multiple myeloma is a malignant tumour of plasma cells that remains incurable for the vast majority of patients, with a median survival of 2-3 years. It is characterized by the patchy accumulation of tumour cells within bone marrow leading to variable anaemia, bone destruction, hypercalcaemia, renal failure and infections. Immune dysfunction is an important feature of the disease and leads to infections that are both a major cause of morbidity and mortality and may promote tumour growth and resistance to chemotherapy. Numerous defects of the immune system have been described in multiple myeloma although the relative clinical importance of these remains elusive. There has been considerable interest in the identification of an autologous response against myeloma. Although T cells and humoral responses directed against myeloma-associated antigens have been described, it is uncertain if the immune system plays a role in preventing or controlling myeloma cell growth. There is increasing interest in the potential role of immunotherapy but the success of these interventions is likely to be modified by the immunologically hostile environment associated with multiple myeloma. This review attempts to summarize the current knowledge relating to the immune defects found in multiple myeloma.

Functional T Cell Responses to Tumor Antigens in Breast Cancer Patients Have a Distinct Phenotype and Cytokine Signature

The overall prevalence with which endogenous tumor Ags induce host T cell responses is unclear. Even when such responses are detected, they do not usually result in spontaneous remission of the cancer. We hypothesized that this might be associated with a predominant phenotype and/or cytokine profile of tumor-specific responses that is different from protective T cell responses to other chronic Ags, such as CMV. We detected significant T cell responses to CEA, HER-2/neu, and/or MAGE-A3 in 17 of 21 breast cancer patients naive to immunotherapy. The pattern of T cell cytokines produced in response to tumor-associated Ags (TAAs) in breast cancer patients was significantly different from that produced in response to CMV or influenza in the same patients. Specifically, there was a higher proportion of IL-2-producing CD8(+) T cells, and a lower proportion of IFN-gamma-producing CD4(+) and/or CD8(+) T cells responding to TAAs compared with CMV or influenza Ags. Finally, the phenotype of TAA-responsive CD8(+) T cells in breast cancer patients was almost completely CD28(+)CD45RA(-) (memory phenotype). CMV-responsive CD8(+) T cells in the same patients were broadly distributed among phenotypes, and contained a high proportion of terminal effector cells (CD27(-)CD28(-)CD45RA(+)) that were absent in the TAA responses. Taken together, these results suggest that TAA-responsive T cells are induced in breast cancer patients, but those T cells are phenotypically and functionally different from CMV- or influenza-responsive T cells. Immunotherapies directed against TAAs may need to alter these T cell signatures to be effective.

Fatos e mitos sobre imunomoduladores

O objetivo deste artigo é discutir alguns fatos dos imunomoduladores modernos que podem ser úteis para o dermatologista clínico. Outro objetivo importante é o de dissipar mitos que possam ter impacto negativo no uso dessas drogas pelo clínico. O foco inicial está em imunomoduladores estimuladores que podem conduzir à acentuação da resposta normal das células imunocompetentes. Para tanto, diversos aspectos associados à regulação do sistema imune e às vias regulatórias das células do sistema imune são mencionados. Discutem-se a regulação aberrante e seu impacto no sistema imune e examina-se a classe de drogas imunossupressoras que têm sua função bem estabelecida. Diversas drogas não foram mencionadas. A razão para isso é o foco do artigo que pretende cobrir os fatos bem estabelecidos ou os mitos que as novas evidências científicas modificaram. Com esse padrão em mente, é provável que exista uma quantidade considerável de similaridade nos conceitos, uma vez que descrevem drogas imunomoduladoras. Nesse contexto, a intenção de fornecer novas perspectivas de como o sistema imune pode ser modulado por essas drogas supera esse problema.