Depletion of CD4+ CD25+ regulatory cells augments the generation of specific immune T cells in tumor-draining lymph nodes

Depletion of regulatory T cells enhances the T cell response induced by the neoantigen vaccine with weak immunogenicity

BACKGROUND

The neoantigen vaccine has remarkable potential in treating advanced cancer due to its tumor specificity and ability to bypass central tolerance mechanisms. However, numerous neoantigens show poor immunogenicity, and the immune inhibitory factors of present in both tumors and tumor-draining lymph nodes impair the efficacy of cancer neoantigen vaccine. Eliminating immunosuppressive cells will improve the priming and expansion of anti-tumor immune cells induced by the vaccine.

METHODS

In this study, a Treg-depleting regimen (consisting of CD25mAb and low-dose cyclophosphamide (LD-CTX)) was used in conjunction with a neoantigen vaccine for treating mice with solid tumors. We constructed two types of tumor models and investigated differences in therapy efficacy in the four groups (PBS, vaccine, CD25mAb+CTX and combination) at the genetic and protein levels. ELISPOT and TCR sequencing were applied to detect the expansion of neoantigen reactive T cells (NRT) and tumor antigen spreading.

RESULTS

In the combinational group, the ELISPOT results showed an obvious expansion of NRT cells induced by weak immunogenic peptides. The combinational group exhibited significant improvement in inhibiting the tumor growth extended the survival time of tumor-bearing mice, and promoted T cells infiltration into tumors. Besides, compared to the Vac group, more neoantigen-targeted and TAA-targeted T cells were detected in the combinational group by TCR sequencing. The results of transcriptomic sequencing and flow cytometry showed that the number of Tregs in the combinational group was lower, while the proportions of memory effector T cells and effector T cells were higher than those in the vaccine group. An increase in mature DCs was also observed in vaccinated mice after receiving this Treg-depleting strategy.

CONCLUSION

Our research first revealed that inhibiting the normal function of Tregs transformed "weaker" neoantigens into "stronger" ones, while also contributing to the proliferation of NRT cells. This Treg-depleting strategy allowed neoantigens with poor immunogenicity to elicit a robust immune response, thereby augmenting the efficacy of the neoantigen vaccine in delaying tumor growth and prolonging the survival of the hosts.

Circulating Immune Cells Predict Prognosis and Clinical Response to Chemotherapy in Cholangiocarcinoma

BACKGROUND

The immune system is linked to the prognosis and response to treatment of patients with cancer. However, the clinical implication of peripheral blood immune cells in cholangiocarcinoma (CCA) remains vague. Thus, we aimed to assess whether peripheral circulating immune cells could be used as an indicator for prognosis and chemotherapeutic efficacy in CCA.

METHODS

The distributions of immune subsets were analyzed in peripheral blood samples from 141 patients with CCA and 131 healthy volunteers by using flow cytometry. The variation in the subset distribution in the two groups and the relationship between clinicopathological features and the subpopulations were investigated. Meanwhile, we assessed the implications of lymphocyte subsets as predictors of chemotherapy outcomes and overall survival (OS).

RESULTS

The proportion of total lymphocytes decreased, while the percentages of activated T cells as well as CD4+CD25+ regulatory T cells (Tregs) increased in CCA. Notably, lymphocyte proportion decreased in patients with regional lymph node (N) (p=0.016) and distant metastasis (M) (p= 0.001). Furthermore, our study showed that peripheral blood lymphocyte subsets were significantly correlated with chemotherapy efficacy, with increased proportions of CD3+ cells (p=0.021) and CD4+ cells (p=0.016) in the effective group. Finally, the Kaplan-Meier analysis indicated that patients with high natural killer (NK) cell proportion might have prolonged OS (p = 0.028).

CONCLUSION

The relationship between circulating immune cells with prognosis and chemotherapy response in patients with CCA highlights their potential application as an indicator of CCA prognosis and stratification of chemotherapy response.

Jiawei Maxing Shigan Tang alleviates radiation-induced lung injury via TGF-β1/Smad signaling pathway mediated by regulatory T cells

ETHNOPHARMACOLOGICAL RELEVANCE

Radiation-induced lung injury (RILI) is a common complication during thoracic radiotherapy which impairs the quality of life in patients and limits radiation doses. Jiawei Maxing Shigan Tang (JMST), which is a modified decoction made of Ephedra, Apricot Kernel, Gypsum, and Licorice, can alleviate the symptoms of RILI in patients. Previous studies and preliminary findings suggested a potential molecular mechanism of JMST in the treatment of RILI. Further studies are needed.

AIM OF THE STUDY

To elucidate the mechanisms of how regulatory T cells (Tregs) promote RILI and the effect of JMST on Tregs, as well as the corresponding pathway.

MATERIALS AND METHODS

CD4+CD25+ Tregs were isolated from rats, and the supernatant's TGF-β1 level was examined by using enzyme-linked immunosorbent assay (ELISA). Type II alveolar epithelial cells (AECs) were co-cultured with the supernatant of Tregs, and the expression levels of epithelial-to-mesenchymal transition (EMT)-related and TGF-β1/Smad signaling pathway-related proteins were analyzed by using western blotting (WB). Afterward, the Tregs were incubated with different concentrations of JMST. The cell viability and TGF-β1 concentration were confirmed by cell counting kit-8 (CCK-8) assay and ELISA, respectively. The optimized concentration of JMST was applied in vitro and vivo experiments. The specific mechanism was investigated through the combination of using flow cytometry, lung histopathology analysis, ELISA, and WB.

RESULTS

Radiation could promote Tregs to secrete TGF-β1. After radiation, the expression levels of Smad2/3, phosphorylated Smad2/3 (p-Smad2/3), Smad4 and mesenchymal markers Vimentin and α-SMA were all increased, while the expression level of epithelial markers E-cadherin was decreased. The expression levels of these proteins were reversed after interventions involving Treg cell activation inhibition or TGF-β1 receptor inhibitor. JMST reduced the number of Tregs in lung tissue and alleviated the degree of pulmonary fibrosis. The expression of Smad2/3, p-Smad2/3, Smad4, TGF-β1, Vimentin, and α-SMA were significantly downregulated, while the E-cadherin was upregulated, through the intervention of JMST.

CONCLUSION

Tregs could mediate EMT through TGF-β1/Smad pathway. JMST inhibits EMT via TGF-β1/Smad pathway by regulating Tregs, therefore alleviating RILI.

Tobacco Use and Response to Immune Checkpoint Inhibitor Therapy in Non-Small Cell Lung Cancer

Tobacco is a known risk factor for lung cancer, and continued tobacco use is associated with poorer outcomes across multiple lung cancer treatment modalities including surgery, chemotherapy and radiation therapy. Less is known about the association of tobacco use and outcomes with immune checkpoint inhibitors (ICIs), which are becoming an important part of the treatment landscape in lung cancer, both in metastatic and curative settings. We reviewed the literature on the association of tobacco and tumor biology as it relates to immunotherapy. We also reviewed the association of tobacco use on outcomes among phase III randomized clinical trials involving ICIs in non-small cell lung cancer (NSCLC). We identified that patients with a smoking history may have a greater benefit with ICI treatment compared to never smokers in both treatment-naïve (HR 0.82, 95% CI 0.69-0.97, vs. HR 1.06, 95% CI 0.81-1.38) and pre-treated (HR 0.79, 95% CI 0.70-0.90 vs. 1.03, 95% CI 0.74-1.43) settings. In trials where smoking status was further defined, ex-smokers appear to demonstrate greater benefit with ICI therapy compared to current smokers (HR 0.78, 95% CI 0.59-1.01 vs. 0.91, 95% CI 0.72-1.14). We conclude by offering our perspective on future directions in this area of research, including implementation of standardized collection and analysis of tobacco use in clinical trials involving ICI therapy in lung cancer and other disease sites, and also evaluating how tobacco may affect toxicities related to ICI therapy. Based on our review, we believe that a patient's history of tobacco smoking does have a role to play in guiding treatment decision making in patients with lung cancer.

The Cancer Cell Dissemination Machinery as an Immunosuppressive Niche: A New Obstacle Towards the Era of Cancer Immunotherapy

Although cancer immunotherapy has resulted in unpreceded survival benefits to subsets of oncology patients, accumulating evidence from preclinical animal models suggests that the immunosuppressive tumor microenvironment remains a detrimental factor limiting benefit for many patient subgroups. Recent efforts on lymphocyte-mediated immunotherapies are primarily focused on eliminating cancer foci at primary and metastatic sites, but few studies have investigated the impact of these therapies on the highly complex process of cancer cell dissemination. The metastatic cascade involves the directional streaming of invasive/migratory tumor cells toward specialized blood vessel intravasation gateways, called TMEM doorways, to the peripheral circulation. Importantly, this process occurs under the auspices of a specialized tumor microenvironment, herewith referred to as "Dissemination Trajectory", which is supported by an ample array of tumor-associated macrophages (TAMs), skewed towards an M2-like polarization spectrum, and which is also vital for providing microenvironmental cues for cancer cell invasion, migration and stemness. Based on pre-existing evidence from preclinical animal models, this article outlines the hypothesis that dissemination trajectories do not only support the metastatic cascade, but also embody immunosuppressive niches, capable of providing transient and localized immunosubversion cues to the migratory/invasive cancer cell subpopulation while in the act of departing from a primary tumor. So long as these dissemination trajectories function as "immune deserts", the migratory tumor cell subpopulation remains efficient in evading immunological destruction and seeding metastatic sites, despite administration of cancer immunotherapy and/or other cytotoxic treatments. A deeper understanding of the molecular and cellular composition, as well as the signaling circuitries governing the function of these dissemination trajectories will further our overall understanding on TAM-mediated immunosuppression and will be paramount for the development of new therapeutic strategies for the advancement of optimal cancer chemotherapies, immunotherapies, and targeted therapies.

Benign lymph node microenvironment is associated with response to immunotherapy

Introduction

Benign lymph nodes have been considered the hubs of immune surveillance in cancer patients. The microenvironment of these lymphoid tissues can be immune suppressed, hence allowing for tumor progression. Understanding the spectrum of benign findings in bystander lymph nodes in immune checkpoint blockade therapy could prove to be key to understanding the mechanism and assessing treatment response.

Methods

Benign lymph nodes and spleen were evaluated from patients treated with immunotherapy who subsequently received postmortem examination. We used quantitative immunofluorescence (QIF) to assess tumor infiltrating lymphocytes (TIL) and macrophage marker expression and characterized activation status using a novel multiplexed QIF assay including CD3, GranzymeB, and Ki67. We performed immunohistochemistry to correlate results of QIF.

Results

Benign lymph nodes from non-responders to immunotherapy showed significantly higher expression of cytotoxic markers and proliferation index (Ki67) in T cells compared to responders. Higher expression of PD-L1 in macrophages was also observed. There was no significant difference in CD3⁺ expression, but higher levels of CD8⁺ T cells as well as CD20⁺ B cells were seen in lymph nodes of non-responders. No significant differences were seen between responder and non-responder splenic tissue. Findings were supported by traditional immunostaining methods.

Conclusions

While most studies in biomarkers for immunotherapy focus on tumor microenvironment, we show that benign lymph node microenvironment may predict response to immunotherapy. In responding patients, bystander lymph nodes appear to have been mobilized, resulting in reduced cytotoxic T cells. Conversely, patients whose disease progressed on immunotherapy demonstrate higher levels of macrophages that express increased PD-L1, and activated T cells not recruited to the tumor site.

CCL22 Signaling in the Tumor Environment

T cell-mediated elimination of malignant cells is one cornerstone of endogenous and therapeutically induced antitumor immunity. Tumors exploit numerous regulatory mechanisms to suppress T cell immunity. Regulatory T cells (T regs) play a crucial role in this process due to their ability to inhibit antitumoral immune responses and they are known to accumulate in various cancer entities. The chemokine CCL22, predominately produced by dendritic cells (DCs), regulates T reg migration via binding to its receptor CCR4. CCL22 controls T cell immunity, both by recruiting T regs to the tumor tissue and by promoting the formation of DC-T reg contacts in the lymph node. Here, we review the current knowledge on the role of CCL22 in cancer immunity. After revising the principal mechanisms of CCL22-induced immune suppression, we address the factors leading to CCL22 expression and ways of targeting this chemokine therapeutically. Therapeutic interventions to the CCL22-CCR4 axis may represent a promising strategy in cancer immunotherapy.

T-Regulatory Cells In Tumor Progression And Therapy

Regulatory T cells (Tregs) are important members of the immune system regulating the host responses to infection and neoplasms. Tregs prevent autoimmune disorders by protecting the host-cells from an immune response, related to the peripheral tolerance. However, tumor cells use Tregs as a shield to protect themselves against anti-tumor immune response. Thus, Tregs are a hurdle in achieving the complete potential of anti-cancer therapies including immunotherapy. This has prompted the development of novel adjuvant therapies that obviate their negative effects thereby enhancing the therapeutic efficacy. Our earlier studies have shown the efficacy of the glycolytic inhibitor, 2-deoxy-D-glucose (2-DG) by reducing the induced Tregs pool and enhance immune stimulation as well as local tumor control. These findings have suggested its potential for enhancing the efficacy of immunotherapy, besides radiotherapy and chemotherapy. This review provides a brief account of the current status of Tregs as a component of the immune-biology of tumors and various preclinical and clinical strategies pursued to obviate the limitations imposed by them in achieving therapeutic efficacy.

Inflammation-induced Id2 promotes plasticity in regulatory T cells

TH17 cells originating from regulatory T (Treg) cells upon loss of the Treg-specific transcription factor Foxp3 accumulate in sites of inflammation and aggravate autoimmune diseases. Whether an active mechanism drives the generation of these pathogenic 'ex-Foxp3 TH17' cells, remains unclear. Here we show that pro-inflammatory cytokines enhance the expression of transcription regulator Id2, which mediates cellular plasticity of Treg into ex-Foxp3 TH17 cells. Expression of Id2 in in vitro differentiated iTreg cells reduces the expression of Foxp3 by sequestration of the transcription activator E2A, leading to the induction of TH17-related cytokines. Treg-specific ectopic expression of Id2 in mice significantly reduces the Treg compartment and causes immune dysregulation. Cellular fate-mapping experiments reveal enhanced Treg plasticity compared to wild-type, resulting in exacerbated experimental autoimmune encephalomyelitis pathogenesis or enhanced anti-tumor immunity. Our findings suggest that controlling Id2 expression may provide a novel approach for effective Treg cell immunotherapies for both autoimmunity and cancer.

Targeting regulatory T cells for improving cancer therapy: Challenges and prospects

OBJECTIVE

Regulatory T cells (Tregs) play a central role in immune responses to infectious agents and tumors. Paradoxically, Tregs protect self-cells from the immune response as a part of peripheral tolerance and prevents autoimmune disorders, whereas during the process of carcinogenesis, they are exploited by tumor cells for protection against antitumor immune responses. Therefore, Tregs are often considered as a major obstacle in anticancer therapy. The objective of this review is to provide a current understanding on Tregs as a potential cellular target for achieving therapeutic gain and discuss various approaches that are implicated at preclinical and clinical scenario.

RECENT FINDINGS

Several approaches like immunotherapy and adjuvant chemotherapy, which reduce Tregs population, have been found to be useful in improving local tumor control. Our recent observations with the glycolytic inhibitor, 2-deoxy-D-glucose, established as an adjuvant in radiotherapy and chemotherapy of tumors also show that potential of 2-deoxy-D-glucose to improve local tumor control is linked with its ability to reduce the Tregs pool.

CONCLUSIONS

Several published studies and emerging evidences indicate that suppression of Treg numbers, infiltration into the tumors, and function can improve the cancer therapy by enhancing the antitumor immunity.

Tumor-associated Glycans and Tregs in Immunogenicity of an Autologous Cell-based Vaccine

Development of cancer vaccines targeting tumor-associated antigens (TAAs) is an alternative approach to chemotherapy with sustained anti-tumor effects. The success of active immunotherapy has been hampered by tumor-induced immune suppressors. Regulatory T cells (Tregs) are a population of immune suppressors with a proven role in regulating anti-tumor immune responses. Removing or subduing Tregs activity leads to more robust anti-tumor immune responses. Here, we used a cell-based vaccination strategy in the 4T1 murine mammary model to examine whether bulk removal of certain TAAs, using their glycan profile, can affect the immunogenicity of the vaccine. We employed affinity columns of several lectins that are reactive with breast cancer cell lines to deplete lectin-reactive TAAs, while enriching for other antigens. Wheat germ agglutinin (WGA), concanavalin A (Con A), Vicia villosa (VVA), and Griffonia simplicifolia lectin-I (GS-I) were used to fraction crude tumor secreted antigens (TSA). Fractions were tested for their ability to stimulate Tregs and their anti-tumor efficacy. We observed that crude TSA activated Tregs and activation of CD4⁺CD25⁺ cells led to an inhibitory function on CD4⁺CD25^- effector cells. Immunization of mice with GS-I- and VVA-depleted fractions significantly delayed tumor establishment and inhibited lung metastases. Depletion of WGA-reactive glycoconjugates led to activation of Tregs, larger tumors and more distant metastases. The data indicate that TAAs can be enriched using their glycan expression pattern to weaken immune suppression and improve anti-tumor response. Therefore, the efficacy of autologous cancer cell vaccination can be improved through enrichment for certain TAAs using carbohydrate specificity.

Molecular Mechanisms for cAMP-Mediated Immunoregulation in T cells - Role of Anchored Protein Kinase A Signaling Units

The cyclic AMP/protein kinase A (cAMP/PKA) pathway is one of the most common and versatile signal pathways in eukaryotic cells. A-kinase anchoring proteins (AKAPs) target PKA to specific substrates and distinct subcellular compartments providing spatial and temporal specificity for mediation of biological effects channeled through the cAMP/PKA pathway. In the immune system, cAMP is a potent negative regulator of T cell receptor-mediated activation of effector T cells (Teff) acting through a proximal PKA/Csk/Lck pathway anchored via a scaffold consisting of the AKAP Ezrin holding PKA, the linker protein EBP50, and the anchoring protein phosphoprotein associated with glycosphingolipid-enriched microdomains holding Csk. As PKA activates Csk and Csk inhibits Lck, this pathway in response to cAMP shuts down proximal T cell activation. This immunomodulating pathway in Teff mediates clinically important responses to regulatory T cell (Treg) suppression and inflammatory mediators, such as prostaglandins (PGs), adrenergic stimuli, adenosine, and a number of other ligands. A major inducer of T cell cAMP levels is PG E2 (PGE2) acting through EP2 and EP4 prostanoid receptors. PGE2 plays a crucial role in the normal physiological control of immune homeostasis as well as in inflammation and cancer immune evasion. Peripherally induced Tregs express cyclooxygenase-2, secrete PGE2, and elicit the immunosuppressive cAMP pathway in Teff as one tumor immune evasion mechanism. Moreover, a cAMP increase can also be induced by indirect mechanisms, such as intercellular transfer between T cells. Indeed, Treg, known to have elevated levels of intracellular cAMP, may mediate their suppressive function by transferring cAMP to Teff through gap junctions, which we speculate could also be regulated by PKA/AKAP complexes. In this review, we present an updated overview on the influence of cAMP-mediated immunoregulatory mechanisms acting through localized cAMP signaling and the therapeutical increasing prospects of AKAPs disruptors in T-cell immune function.

Photodynamic therapy downregulates the function of regulatory T cells in patients with esophageal squamous cell carcinoma

Photodynamic therapy (PDT) by selective photosensitization of cancer cells and subsequent laser application results in local tumor necrosis. However, the effects of PDT on immune function, which may depend on the type of immune response, are controversial. We investigated the immunological changes induced by PDT and the effect of PDT on level and function of regulatory T cells (Treg) in patients with invasive esophageal squamous cell carcinoma (ESCC). We analyzed patient's blood samples before and after PDT. Blood CD4+CD25+CD127-FoxP3+ Treg levels were quantified by FACS, and Treg function was evaluated by coculture proliferation assays with T effector (Teff) cells. We found that PDT abrogated the suppressive capacity of peripheral Treg (Days 7 and 14, p = 0.016) but had no effect on Treg levels. The effect of PDT on Treg function at Day 7 was accompanied by slight but statistically significant increases in peripheral neutrophil granulocytes (p = 0.035) and monocytes (p = 0.013) and a statistically significant increase (approximately 18-fold) in serum IL-6 levels (p = 0.008). In conclusion, PDT abolished Treg function, possibly due to increased IL-6 levels in treated ESCC patients. This may be crucial for an improved therapeutic outcome.

Not just for tumor targeting: unmet medical needs and opportunities for nanomedicine

During the last 3 decades, nanomedicines have provided novel opportunities to improve the delivery of chemotherapeutics in cancer therapy effectively. However, many principles learnt from there have the potential to be transferred to other diseases. This perspective article, on the one hand, critically reflects the limitations of nanomedicines in tumor therapy and, on the other hand, provides alternative examples of nanomedicinal applications in immunotherapy, noninvasive drug deliveries across epithelial barriers and strategies to combat intra- and extra-cellular bacterial infections. Looking ahead, access to highly complex nanoparticular delivery vehicles given nowadays may allow further improved therapeutic concepts against several diseases in the future too.

T-cell mediated anti-tumor immunity after photodynamic therapy: why does it not always work and how can we improve it?

Photodynamic therapy (PDT) uses the combination of non-toxic photosensitizers and harmless light to generate reactive oxygen species that destroy tumors by a combination of direct tumor cell killing, vascular shutdown, and activation of the immune system. It has been shown in some animal models that mice that have been cured of cancer by PDT, may exhibit resistance to rechallenge. The cured mice can also possess tumor specific T-cells that recognize defined tumor antigens, destroy tumor cells in vitro, and can be adoptively transferred to protect naïve mice from cancer. However, these beneficial outcomes are the exception rather than the rule. The reasons for this lack of consistency lie in the ability of many tumors to suppress the host immune system and to actively evade immune attack. The presence of an appropriate tumor rejection antigen in the particular tumor cell line is a requisite for T-cell mediated immunity. Regulatory T-cells (CD25+, Foxp3+) are potent inhibitors of anti-tumor immunity, and their removal by low dose cyclophosphamide can potentiate the PDT-induced immune response. Treatments that stimulate dendritic cells (DC) such as CpG oligonucleotide can overcome tumor-induced DC dysfunction and improve PDT outcome. Epigenetic reversal agents can increase tumor expression of MHC class I and also simultaneously increase expression of tumor antigens. A few clinical reports have shown that anti-tumor immunity can be generated by PDT in patients, and it is hoped that these combination approaches may increase tumor cures in patients.

Requirement of Innate Immunity in Tumor-Bearing Mice Cured by Adoptive Immunotherapy Using Tumor-Draining Lymph Nodes

BACKGROUND

The purpose of this study was to determine the cellular effectors of both the adoptively transferred cells and the tumor-bearing host that participate in the antitumor response to adoptive immunotherapy using culture-activated tumor-draining lymph nodes (TDLNs).

METHODS

TDLNs harvested from mice with 4T1 carcinoma cells were fractionated to derive the L-selectin(low) subpopulation and activated ex vivo prior to in vitro cytokine release assays and adoptive transfer into BALB/c mice bearing 3-day established subcutaneous tumors. Tumor-bearing recipients were SCID (lacking T, B, and NK cells), Rag2 deficient (lacking T and B cells), and wild-type BALB/c mice.

RESULTS

Culture-activated L-selectin(low) 4T1 TDLN from BALB/c mice secreted significant levels of interferon-gamma in response to 4T1 but not control tumor cells in vitro. CD4 cells within the adoptively transferred effector cell population contributed significantly to the antitumor effect in vivo. Culture-activated L-selectin(low) TDLNs from BALB/c wild-type mice were able to cure Rag2 deficient but not SCID mice bearing 4T1 subcutaneous tumors, suggesting a requirement of NK cells within the innate immune system of the tumor-bearing host during the antitumor response.

CONCLUSIONS

These results identify the cellular effectors involved in tumor regression following adoptive transfer and demonstrate the requirement for intact innate immunity within the tumor-bearing host.

Manipulation of regulatory T cells and antigen-specific cytotoxic T lymphocyte-based tumour immunotherapy

The most potent killing machinery in our immune system is the cytotoxic T lymphocyte (CTL). Since the possibility for self-destruction by these cells is high, many regulatory activities exist to prevent autoimmune destruction by these cells. A tumour (cancer) grows from the cells of the body and is tolerated by the body's immune system. Yet, it has been possible to generate tumour-associated antigen (TAA) -specific CTL that are also self-antigen specific in vivo, to achieve a degree of therapeutic efficacy. Tumour-associated antigen-specific T-cell tolerance through pathways of self-tolerance generation represents a significant challenge to successful immunotherapy. CD4(+)  CD25(+)  FoxP3(+) T cells, referred to as T regulatory (Treg) cells, are selected in the thymus as controllers of the anti-self repertoire. These cells are referred to as natural T regulatory (nTreg) cells. According to the new consensus (Nature Immunology 2013; 14:307-308) these cells are to be termed as (tTreg). There is another class of CD4(+) Treg cells also involved in regulatory function in the periphery, also phenotypically CD4(+)  CD25(±) , classified as induced Treg (iTreg) cells. These cells are to be termed as peripherally induced Treg (pTreg) cells. In vitro-induced Treg cells with suppressor function should be termed as iTreg. These different Treg cells differ in their requirements for activation and in their mode of action. The current challenges are to determine the degree of specificity of these Treg cells in recognizing the same TAA as the CTL population and to circumvent their regulatory constraints so as to achieve robust CTL responses against cancer.

Aging and cancer vaccines

Cancer vaccination is less effective at old than at young age, due to T cell unresponsiveness. This is caused by age-related changes of the immune system. Major immune defects at older age are lack of naive T cells, impaired activation pathways of T cells and antigen-presenting cells (APC), and age-related changes in the tumor microenvironment (TME). Also innate immune responses are affected by aging, but this seems less abundant than adaptive immune responses. In this review we compared various cancer vaccine studies at young and old age, demonstrating the importance of both innate and adaptive immune responses for cancer immunotherapy. Moreover, we found suggestive evidence that innate immune responses could help improve adaptive immune responses through cancer vaccination in old age.

Is cancer vaccination feasible at older age?

Age-related defects of the immune system are responsible for T cell unresponsiveness to cancer vaccination at older age. Major immune defects at older age are lack of naive T cells, impaired activation pathways of T cells and antigen-presenting cells (APCs), and age-related changes in the tumor microenvironment (TME). This raises the question whether cancer vaccination is feasible at older age. We compared various cancer vaccine studies at young and old age, thereby focusing on the importance of both innate and adaptive immune responses for cancer immunotherapy. These analyses suggest that creating an immune-stimulating environment with help of the innate immune system may improve T cell responses in cancer vaccination at older age.

Modulation of bone morphogenic protein signaling in T-cells for cancer immunotherapy

Immunotherapy is becoming an increasingly attractive therapeutic alternative for conventional cancer therapy. In recent years Foxp3(+) regulatory T-cells (T(R)) were identified as the major obstacle to effective cancer immunotherapy. The abundance of these cells in peripheral blood is increased in patients with multiple types of cancer and their prevalence among tumor-infiltrating lymphocytes correlated with poor clinical prognosis. In contrast, removal or inactivation of T(R) cells led to enhanced anti-tumor immune response and better efficacy of cancer vaccines. This study reports that Bone Morphogenic Protein Receptor 1α (BMPR1α, Alk-3) is expressed by activated effector CD4(+) and T(R) cells and modulates functions of both cell types. Bone Morphogenic Proteins (BMPs) belong to the transforming growth factor (TGF)-β family of cytokines that also include TGFβ and activins. BMPs play crucial roles in embryonic development, tissue differentiation and homeostasis, and development of cancer. It was demonstrated that BMPs and activins synergize with TGFβ to regulate thymic T-cell development, maintain T(R) cells, and control peripheral tolerance. Inactivation of BMPR1α in T-cells results in impaired thymic and peripheral generation of T(R) cells. BMPR1α-deficient activated T-cells produced a higher level of interferon (IFN)-γ than BMPR1α-sufficient T-cells. Moreover, transplanted B16 melanoma tumors grew smaller in mice lacking expression of BMPR1α in T-cells and tumors had few infiltrating TR cells and a higher proportion of CD8(+) T-cells than wild-type mice.

Adoptive cell therapies for glioblastoma

Glioblastoma (GBM) is the most common and most aggressive primary brain malignancy and, as it stands, is virtually incurable. With the current standard of care, maximum feasible surgical resection followed by radical radiotherapy and adjuvant temozolomide, survival rates are at a median of 14.6 months from diagnosis in molecularly unselected patients (1). Collectively, the current knowledge suggests that the continued tumor growth and survival is in part due to failure to mount an effective immune response. While this tolerance is subtended by the tumor being utterly “self,” it is to a great extent due to local and systemic immune compromise mediated by the tumor. Different cell modalities including lymphokine-activated killer cells, natural killer cells, cytotoxic T lymphocytes, and transgenic chimeric antigen receptor or αβ T cell receptor grafted T cells are being explored to recover and or redirect the specificity of the cellular arm of the immune system toward the tumor complex. Promising phase I/II trials of such modalities have shown early indications of potential efficacy while maintaining a favorable toxicity profile. Efficacy will need to be formally tested in phase II/III clinical trials. Given the high morbidity and mortality of GBM, it is imperative to further investigate and possibly integrate such novel cell-based therapies into the current standards-of-care and herein we collectively assess and critique the state-of-the-knowledge pertaining to these efforts.

Photodynamic therapy plus regulatory T-cell depletion produces immunity against a mouse tumour that expresses a self-antigen

Background:

Photodynamic therapy (PDT) can lead to development of antigen-specific immune response and PDT-mediated immunity can be potentiated by T regulatory cell (Treg) depletion. We investigated whether the combination of PDT with cyclophosphamide (CY) could foster immunity against wild-type tumours expressing self-antigen (gp70).

Methods:

Mice with CT26 tumours were treated with PDT alone or in combination with low-dose CY. T regulatory cell numbers and transforming growth factor-β (TGF-β) levels were measured at several time points after treatment. Mice cured by PDT+CY were rechallenged with CT26 and monitored for long-term survival.

Results:

Photodynamic therapy+CY led to complete tumour regression and long-term survival in 90% of treated mice while the absolute numbers of Treg decreased after PDT+CY and the TGF-β levels were reduced to a level comparable to naïve mice. Sixty-five percent of the mice treated with PDT+CY that survived over 90 days tumour free rejected the rechallenge with the same tumour when a second dose of CY was administered before rechallenge but not without.

Conclusion:

Administration of CY before PDT led to depletion of Treg and potentiated PDT-mediated immunity, leading to long-term survival and development of memory immunity that was only uncovered by second Treg depletion.

Therapy model for advanced intracerebral B16 mouse melanoma using radiation therapy combined with immunotherapy

A reproducible therapy model for advanced intracerebral B16 melanoma is reported. Implanted tumors (D0), suppressed by a single 15 Gy radiosurgical dose of 100 kVp X-rays (D8), were further suppressed by a single ip injection of a Treg-depleting mAb given 2 days prior to the initiation (D9) of four weekly then eight bi-monthly sc injections of GMCSF-transfected, mitotically disabled B16 cells. The trends of seven independent experiments were similar to the combined result: The median (days) [SD/total N] of survival went from 15[1.09/62] (no treatment control) to 35.8[8.8/58] (radiation therapy only) to 52.5[13.5/57] (radiation therapy plus immunotherapy). Within 2 weeks after immunization, tumors in mice receiving radiation therapy plus immunotherapy were significantly smaller than tumors in mice treated only with radiosurgery. Splenocytes and lymph node cells from immunized mice showed increased interferon γ production when cultured with syngeneic tumor cells. We suggest that our model will be useful for the development and testing of novel combination therapies for brain tumors.

Antitumor activity of tumor-targeted RNA replicase-based plasmid that expresses interleukin-2 in a murine melanoma model

Double-stranded RNA (dsRNA) has multiple antitumor mechanisms that may be used to control tumor growth. Previously we have shown that treatment of solid tumors with a plasmid that encodes Sindbis viral RNA replicase complex, pSIN-β, significantly inhibited the growth of tumors in mice. In the present study, we evaluated the feasibility of further improving the antitumor activity of the pSIN-β plasmid by incorporating interleukin-2 (IL2) gene into the plasmid. The resultant pSIN-IL2 plasmid was delivered to mouse melanoma cells that overexpress the sigma receptor. Here we report that the pSIN-IL2 plasmid was more effective at controlling the growth of B16 melanoma in mice when complexed with sigma receptor-targeted liposomes than with the untargeted liposomes. Importantly, the pSIN-IL2 plasmid was more effective than pSIN-β plasmid at controlling the growth of B16 melanoma in mice, and B16 tumor-bearing mice that were treated with pSIN-IL2 had an elevated number of activated CD4(+), CD8(+), and natural killer cells, as compared to those treated with pSIN-β. The RNA replicase-based, IL2-expressing plasmid may have applications in melanoma gene therapy.

Intrinsic immune alterations in renal cell carcinoma and emerging immunotherapeutic approaches

INTRODUCTION

Individuals affected by kidney cancer present a variety of immune abnormalities including cellular immune dysfunction, cytokine alterations and antigen presentation defects. On the other hand, spontaneous remissions are seen in up to 4% of renal cell carcinoma (RCC) patients and they are thought to occur via immune mechanisms.

AREAS COVERED

The authors comprehensively review the immune abnormalities in RCC patient and describe the kidney cancer immunotherapy candidates that are most advanced in their clinical development. Most relevant publications were identified through searching the PubMed database; the obtained information was thoroughly analyzed and synthesized.

EXPERT OPINION

As cure in advanced RCC cannot be accomplished with the current therapy standards such as tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors, new treatment strategies are being sought. Enhancing the immune system represents an appealing avenue for kidney cancer therapy. Disappointingly, high-dose interleukin-2 and interferon-α cause severe toxicity and produce a questionable clinical benefit. The authors postulate that the 'durable responses' seen with these agents in only a handful of RCC patients represent spontaneous remissions. Promising immune strategies in RCC such as anti-cytotoxic T-lymphocyte-associated protein antibodies, anti-programmed cell death 1 (PD1)/PD1 ligand and tumor vaccines may expand the existing options for kidney cancer in future years.

Immunotherapy against HPV16/18 generates potent TH1 and cytotoxic cellular immune responses

Despite the development of highly effective prophylactic vaccines against human papillomavirus (HPV) serotypes 16 and 18, prevention of cervical dysplasia and cancer in women infected with high-risk HPV serotypes remains an unmet medical need. We report encouraging phase 1 safety, tolerability, and immunogenicity results for a therapeutic HPV16/18 candidate vaccine, VGX-3100, delivered by in vivo electroporation (EP). Eighteen women previously treated for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3) received a three-dose (intramuscular) regimen of highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens followed by EP in a dose escalation study (0.3, 1, and 3 mg per plasmid). Immunization was well tolerated with reports of mild injection site reactions and no study-related serious or grade 3 and 4 adverse events. No dose-limiting toxicity was noted, and pain was assessed by visual analog scale, with average scores decreasing from 6.2/10 to 1.4 within 10 min. Average peak interferon-γ enzyme-linked immunospot magnitudes were highest in the 3 mg cohort in comparison to the 0.3 and 1 mg cohorts, suggesting a trend toward a dose effect. Flow cytometric analysis revealed the induction of HPV-specific CD8(+) T cells that efficiently loaded granzyme B and perforin and exhibited full cytolytic functionality in all cohorts. These data indicate that VGX-3100 is capable of driving robust immune responses to antigens from high-risk HPV serotypes and could contribute to elimination of HPV-infected cells and subsequent regression of the dysplastic process.

In vitro selective depletion of CD4(+)CD25(+) regulatory T-cells from PBMC using anti-tac-SAP

It has been shown that naturally occurring regulatory T-cells (CD4(+)CD25(+) Foxp3(+) T-cells) have critical roles in tumor invasion and down-regulation of immune response against established tumors. High expression of CD25 (IL-2Rα) by regulatory T (T(reg)) cells may cause an inefficient response when using IL-2-based cancer vaccines. It seems that selective elimination of T(reg) cells before treatment of tumor-bearing T-cells can strongly increase the efficacy of a vaccine. The aim of this study was to set up an efficient cost-effective protocol to eliminate CD4(+)CD25(+) T-cells-using the immunotoxin anti-tac-SAP. Peripheral blood mononuclear cells (PBMC) taken from colon cancer patients were treated with different concentrations (i.e., 0-100 µg/dl) of the immunotoxin. Flow cytometric analyses were then preformed to analyze expression of CD4, CD25, CD3, CD8, and CD45 surface markers; semi-quantitative fluorescent-PCR was used for the detection of Foxp3 expression before and after anti-tac-SAP treatment. The results indicated that anti-tac-SAP effectively eliminated CD4(+)CD25(+) T(reg) cells and that 25 µg/dl was the optimal concentration of anti-tac-SAP for selective depletion of these cells. These outcomes were verified by analyses of Foxp3 expression. The results also indicated that this immunotoxin had no non-specific effects on other T-cells, including CD4(+)CD25(-) and CD8(+)CD45(+) T-cells. Building on the work here, ongoing/future studies with the anti-tac-SAP will focus on functional assessments of the remaining (i.e., non-eliminated) T-cells (i.e., CD8, CD4; using proliferation and peptide sensitization assays) to ascertain if the immunotoxin inadvertently alters the functions of these cells-an untoward outcome.

Modulation of T cell immune functions by the prostaglandin E(2) - cAMP pathway in chronic inflammatory states

Cyclic AMP is the intracellular second messenger for a variety of immunoregulatory inflammatory mediators such as prostaglandin E2, adenosine and histamine that signal to effector T cells from monocytes, macrophages and regulatory T cells. Protein kinase A (PKA) type I localizes to lipid rafts in effector T cells during T cell activation and directly modulates proximal signal events including phosphorylation of C-terminal Src kinase (Csk), which initiates a negative signal pathway that fine-tunes the T cell activation process. The PKA-Csk immunoregulatory pathway is scaffolded by the A kinase anchoring protein ezrin, the Csk binding protein phosphoprotein associated with glycosphingolipid-enriched membrane microdomains and the linker protein ezrin/radixin/moesin binding protein of 50 kDa. This pathway is hyperactivated in chronic infections with an inflammatory component such as HIV, other immunodeficiencies and around solid tumours as a consequence of local inflammation leading to inhibition of anti-tumour immunity. LINKED ARTICLES This article is part of a themed section on Novel cAMP Signalling Paradigms. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.166.issue-2.

Depletion of radio-resistant regulatory T cells enhances antitumor immunity during recovery from lymphopenia

Cytotoxic lymphodepletion therapies augment antitumor immune responses. The generation and therapeutic efficacy of antitumor effector T cells (T(E)s) are enhanced during recovery from lymphopenia. Although the effects of lymphodepletion on naive T cells (T(N)s) and T(E)s have been studied extensively, the influence of lymphodepletion on suppressor cells remains poorly understood. In this study, we demonstrate a significant increase of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) in sublethally irradiated lymphopenic mice. These radio-resistant Tregs inhibited the induction of T(E)s in tumor-draining lymph-nodes (TDLNs) during recovery from lymphopenia. The transfer of T(N)s into lymphopenic tumor-bearing mice resulted in some antitumor effects; however, Treg depletion after whole-body irradiation and reconstitution strongly inhibited tumor progression. Further analyses revealed that tumor-specific T cells were primed from the transferred T(N)s, whereas the Tregs originated from irradiated recipient cells. As in irradiated lymphopenic mice, a high percentage of Tregs was observed in cyclophosphamide-treated lymphopenic mice. The inhibition of Tregs in cyclophosphamide-treated mice significantly reduced tumor growth. These results indicate that the Tregs that survive cytotoxic therapies suppress antitumor immunity during recovery from lymphopenia and suggest that approaches to deplete radio and chemo-resistant Tregs can enhance cancer immunotherapies.

Novel strategies for immunotherapy in multiple myeloma: previous experience and future directions

Multiple myeloma (MM) is a life-threatening haematological malignancy for which standard therapy is inadequate. Autologous stem cell transplantation is a relatively effective treatment, but residual malignant sites may cause relapse. Allogeneic transplantation may result in durable responses due to antitumour immunity mediated by donor lymphocytes. However, morbidity and mortality related to graft-versus-host disease remain a challenge. Recent advances in understanding the interaction between the immune system of the patient and the malignant cells are influencing the design of clinically more efficient study protocols for MM. Cellular immunotherapy using specific antigen-presenting cells (APCs), to overcome aspects of immune incompetence in MM patients, has received great attention, and numerous clinical trials have evaluated the potential for dendritic cell (DC) vaccines as a novel immunotherapeutic approach. This paper will summarize the data investigating aspects of immunity concerning MM, immunotherapy for patients with MM, and strategies, on the way, to target the plasma cell more selectively. We also include the MM antigens and their specific antibodies that are of potential use for MM humoral immunotherapy, because they have demonstrated the most promising preclinical results.

T cell subpopulations in lymph nodes may not be predictive of patient outcome in colorectal cancer

Background

The immune response has been proposed to be an important factor in determining patient outcome in colorectal cancer (CRC). Previous studies have concentrated on characterizing T cell populations in the primary tumour where T cells with regulatory effect (Foxp3+ Tregs) have been identified as both enhancing and diminishing anti-tumour immune responses. No previous studies have characterized the T cell response in the regional lymph nodes in CRC.

Methods

Immunohistochemistry was used to analyse CD4, CD8 or Foxp3+ T cell populations in the regional lymph nodes of patients with stage II CRC (n = 31), with (n = 13) or without (n = 18) cancer recurrence after 5 years of follow up, to determine if the priming environment for anti-tumour immunity was associated with clinical outcome.

Results

The proportions of CD4, CD8 or Foxp3+ cells in the lymph nodes varied widely between and within patients, and there was no association between T cell populations and cancer recurrence or other clinicopathological characteristics.

Conclusions

These data indicate that frequency of these T cell subsets in lymph nodes may not be a useful tool for predicting patient outcome.

Regulatory T cells in gastrointestinal tumors

Regulatory T cells (Tregs) have the ability to suppress the activity of most other lymphoid cells, as well as dendritic cells through cell-cell contact-dependent mechanisms, which have not yet been fully defined. Tregs are a key component of a functional immune system and Treg deficiency is associated with severe autoimmunity and allergies. However, Tregs specific for tumor-associated antigens are present in cancer patients and Tregs accumulate in many types of solid tumors, where they probably act to promote tumor escape from cytotoxic immune responses. Indeed, some studies even show a negative correlation between Treg infiltration and survival of the patient. Several studies indicate an active recruitment of Tregs to the tumor site and the mechanisms of Treg accumulation are starting to be better understood as a result of more detailed analysis of their adhesion molecule and chemokine receptor expression. In addition, in gastrointestinal tumors there is an increase in tumor-associated Tregs, but intriguingly, Treg infiltration into colorectal adenocarcinomas is associated with improved prognosis. In this article, we will review the proposed mechanisms of immune suppression by tumor-associated Tregs, how the tumor microenvironment favors immune evasion and Treg induction, the tumor-homing mechanisms of Tregs and how Tregs affect progression of gastric and colorectal tumors.

The impact of aging on cancer vaccination

Cancer vaccination is less effective at old than at young age, due to T cell unresponsiveness, caused by various age-related changes of the immune system. This includes lack of naïve T cells, defects in activation pathways of T cells and antigen-presenting cells (APC), and age-related changes in the tumor microenvironment. Although evidence exists that also natural killer (NK) and natural killer T (NKT) cells of the innate immune system change with age, comparison of various studies involving adaptive and innate immune responses in elderly and cancer patients, as well as cancer vaccination at young and old age in this review, indicates that also innate immune responses should be tested as a potential candidate to improve immunotherapy against cancer at older age.

An injectable synthetic immune-priming center mediates efficient T-cell class switching and T-helper 1 response against B cell lymphoma

Patients with malignant non-Hodgkin's lymphomas (NHL) of B-cell lineages relapse despite initial anti-tumor response to chemotherapy or antibody treatments. Failure to eliminate the tumor is often because of inadequate priming, low cell numbers and suboptimal phenotype of effector T cells. Here we describe a new biomaterial-based controlled-release paradigm to treat weakly immunogenic NHLs by in-situ amplifying the number of functional, antigen-specific T-helper 1 (Th1) cells following immunotherapy. An injectable, synthetic immune priming center (sIPC) consisting of an in-situ crosslinking, chemokine-carrying hydrogel and both DNA- and siRNA dual-loaded microparticles, is reported. This sIPC chemo attracts a large number of immature dendritic cells (DCs) at the site of administration and efficiently co-delivers both DNA antigens and interleukin-10 (IL10)-silencing siRNA to those cells. Using a murine model of A20 B cell lymphoma, we demonstrate that combination of DNA-antigen delivery and IL10 silencing, synergistically activate recruited immature DCs and cause a strong shift towards Th1 response while suppressing Th2 and Th17 cytokines. sIPC-based immunotherapy showed 45% more CD8+ cytotoxic T cell (CTL) response and 53% stronger CD4+ CTL activity compared to naked DNA vaccine. In addition, in-vivo sIPC immunization induced significant protection (p<0.01) against subsequent tumor challenge. Such a multi-modal, injectable system that simultaneously delivers chemokines, siRNA and DNA antigens to DCs marks a new approach to in-situ priming and modulation during immunotherapy and could provide effective vaccination strategies against cancers and infectious diseases.

NKT cell exacerbation of liver metastases arising from melanomas transplanted into either the eyes or spleens of mice

PURPOSE

To explore the role of natural killer T (NKT) cells in the development of liver metastases in mice harboring intraocular melanomas.

METHODS

Cells derived from the cutaneous B16 melanoma cell line (B16LS9) were transplanted either into the vitreous body or under the spleen capsules of wild-type C57BL/6 mice and NKT-cell-deficient Jα18(-/-) and CD1d(-/-) mice. The development of liver metastases was evaluated by histopathology. The effect of NK cells on liver metastases was determined by selective depletion with anti-asialo-GM1 antiserum in vivo and NK-cell-mediated cytolysis of B16LS9 melanoma cells in vitro. The role of IL-10 and transforming growth factor (TGF)-β in the inhibition of liver NK resistance to liver metastases was determined by in vivo and in vitro neutralization with monoclonal antibodies.

RESULTS

Liver NKT cells, especially type I NKT cells, enhanced liver metastases arising from intraocular melanomas. NKT-cell-deficient mice developed significantly fewer liver metastases that were NK-cell dependent. Tumor-induced liver NKT cells, especially type I NKT cells, inhibited liver NK-cell cytotoxicity by an IL-10-dependent process.

CONCLUSIONS

NKT cells exert protective effects in many murine tumor models. However, the present results reveal that NKT cells exacerbate liver metastases arising from intraocular melanomas. To the authors' knowledge, this is the first report that liver NKT cells, especially type I NKT cells, inhibit liver NK-cell antimetastatic activity by the production of IL-10. These results suggest that hepatic NKT cell activity can have an important effect in the immune surveillance of liver metastases.

Effective melanoma immunotherapy with interleukin-2 delivered by a novel polymeric nanoparticle

Interleukin-2 (IL-2) has been shown to possess antitumor activity in numerous preclinical and clinical studies. However, the short half-life of recombinant IL-2 protein in serum requires repeated high-dose injections, resulting in severe side effects. Although adenovirus-mediated IL-2 gene therapy has shown antitumor efficacy, the host antibody response to adenoviral particles and potential biosafety concerns still obstruct its clinical applications. Here we report a novel nanopolymer for IL-2 delivery, consisting of low molecular weight polyethylenimine (600 Da) linked by β-cyclodextrin and conjugated with folate (named H1). H1 was mixed with IL-2 plasmid to form H1/pIL-2 polyplexes of around 100 nm in diameter. Peritumoral injection of these polyplexes suppressed the tumor growth and prolonged the survival of C57/BL6 mice bearing B16-F1 melanoma grafts. Importantly, the antitumor effects of H1/pIL-2 (50 μg DNA) were similar to those of recombinant adenoviruses expressing IL-2 (rAdv-IL-2; 2 × 10(8) pfu). Furthermore, we showed that H1/pIL-2 stimulated the activation and proliferation of CD8+, CD4+ T cell, and natural killer cells in peripheral blood and increased the infiltration of CD8+, CD4+ Tcells, and natural killer cells into the tumor environment. In conclusion, these results show that H1/pIL-2 is an effective and safe melanoma therapeutic with an efficacy comparable to that of rAdv-IL-2. This treatment represents an alternative gene therapy strategy for melanoma.

Efficient Treg depletion induces T-cell infiltration and rejection of large tumors

There are a number of factors that hamper immunotherapy of cancer. For example, tumors exhibit an aberrant vasculature that appears to form a barrier against T-cell infiltration. Another major obstacle is created by Treg. So far, conventional depletion of Treg with anti-CD25 antibodies, which eliminate only 70% of Treg, has failed to significantly reduce the growth of established tumors. Using Foxp3.LuciDTR-4 mice, we show here that 90-95% Treg depletion resulted in complete regression of large established tumors, whereas 70% depletion was ineffective. The extensive Treg depletion induced a number of processes that are critical for tumor rejection, including activation of tumor-specific CD8(+) T cells and enhanced infiltration of these cells into the tumor. The precise mechanism of enhanced infiltration is not known, but normalization of the tumor vasculature is assumed to assist infiltration. Indeed, we observed that 90% Treg depletion caused normalization of the tumor vasculature as indicated by a reduction in leakiness and the number of dilated vessels. These results suggest that for clinical immunotherapy of cancer, it would be desirable to have reagents that allow high-level depletion of Treg, which, in conjunction with treatment modalities such as vaccination, may concomitantly increase T-cell activation and infiltration.

Lymphadenectomy exacerbates tumor growth while lymphadenectomy plus the adoptive transfer of autologous cytotoxic cells and low-dose cyclophosphamide induces regression of an established murine fibrosarcoma

Tumor-draining lymph node (TDLN) ablation is routinely performed in the management of cancer; nevertheless, its usefulness is at present a matter of debate. TDLN are central sites where T cell priming to tumor antigens and onset of the antitumor immune response occur. However, tumor-induced immunosuppression has been demonstrated at TDLN, leading to downregulation of antitumor reaction and tolerance induction. Tolerance in turn is a main impairment for immunotherapy trials. We used a murine immunogenic fibrosarcoma that evolves to a tolerogenic state, to study the cellular and molecular mechanisms underlying tolerance induction at the level of TDLN and to design an appropriate immunotherapy. We determined that following a transient activation, the established tumor induces signs of immunosuppression at TDLN that coexist with local and systemic evidences of antitumor response. Therefore, we evaluated the feasibility of removing TDLN in order to eliminate a focus of immunosuppression and favor tumor rejection; but instead, a marked exacerbation of tumor growth was induced. Combining TDLN ablation with the in vivo depletion of regulatory cells by low-dose cyclophosphamide and the restoring of the TDLN-derived cells into the donor mouse by adoptive transference, resulted in lowered tumor growth, enhanced survival and a considerable degree of tumor regression. Our results demonstrate that important antitumor elements can be eliminated by lymphadenectomy and proved that the concurrent administration of low-dose chemotherapy along with the reinoculation of autologous cytotoxic cells provides protection. We suggest that this protocol may be useful, especially in the cases where lymphadenectomy is mandatory.

Immunotherapy for lung cancers

Lung cancer is the leading cause of cancer-related deaths worldwide. Although treatment methods in surgery, irradiation, and chemotherapy have improved, prognosis remains unsatisfactory and developing new therapeutic strategies is still an urgent demand. Immunotherapy is a novel therapeutic approach wherein activated immune cells can specifically kill tumor cells by recognition of tumor-associated antigens without damage to normal cells. Several lung cancer vaccines have demonstrated prolonged survival time in phase II and phase III trials, and several clinical trials are under investigation. However, many clinical trials involving cancer vaccination with defined tumor antigens work in only a small number of patients. Cancer immunotherapy is not completely effective in eradicating tumor cells because tumor cells escape from host immune scrutiny. Understanding of the mechanism of immune evasion regulated by tumor cells is required for the development of more effective immunotherapeutic approaches against lung cancer. This paper discusses the identification of tumor antigens in lung cancer, tumor immune escape mechanisms, and clinical vaccine trials in lung cancer.

Cyclic AMP-mediated immune regulation--overview of mechanisms of action in T cells

The canonical second messenger cAMP is well established as a potent negative regulator of T cell immune function. Through protein kinase A (PKA) it regulates T cell function at the level of transcription factors, members of the mitogen-activated protein kinase pathway, phospholipases (PLs), Ras homolog (Rho)A and proteins involved in the control of cell cycle progression. Type I PKA is the predominant PKA isoform in T cells. Furthermore, whereas type II PKA is located at the centrosome, type I PKA is anchored close to the T cell receptor (TCR) in lipid rafts by the Ezrin-ERM-binding phosphoprotein of 50 kDa (EBP50)-phosphoprotein associated with glycosphingolipid-enriched microdomains (PAG) scaffold complex. The most TCR-proximal target for type I PKA is C-terminal Src kinase (Csk), which upon activation by raft recruitment and phosphorylation inhibits the Src family tyrosine kinases Lck and Fyn and thus functions to maintain T cell homeostasis. Recently, induction of cAMP levels in responder T cells has emerged as one of the mechanisms by which regulatory T (T(R)) cells execute their suppressive action. Thus, the cAMP-type I PKA-Csk pathway emerges as a putative target for therapeutic intervention in autoimmune disorders as well as in cancer, where T(R) cell-mediated suppression contributes to suboptimal local immune responses.

A reversed CD4/CD8 ratio of tumor-infiltrating lymphocytes and a high percentage of CD4(+)FOXP3(+) regulatory T cells are significantly associated with clinical outcome in squamous cell carcinoma of the cervix

In this study, 40 biopsy samples collected from cervical cancer patients at the First Affiliated Hospital of Xi'an Jiaotong University, China, were retrospectively assessed using immunohistochemistry for CD4(+) and CD8(+) tumor-infiltrating lymphocytes (TILs) and were analyzed for the expression of FOXP3, OX40, granzyme B (GrB) and perforin (Prf). The proliferating index of the TILs was determined by assessing Ki67 expression. We determined the prognostic value of low and high numbers of TILs on survival by performing Kaplan-Meier analysis using median values as the cut-off points. Except for the number of CD4(+)FOXP3(+) regulatory T cells (Tregs) and the CD4/CD8 ratio, none of the CD4(+), CD8(+), OX40(+), GrB(+) or Prf(+) TILs were associated with the overall 5-year survival rate. The 5-year survival rate was significantly lower in patients who had a high percentage of Tregs as compared with the those who had a lower percentage (35.3% versus 88.9%, P=0.001), while the 5-year survival rate was significantly higher in patients with a high CD4/CD8 ratio as compared with patients who had a low CD4/CD8 ratio (82.4% versus 44.4%, P=0.029). When we considered the deaths and surviving cases as separate groups, we found that both the number of CD4(+) T cells and the CD4/CD8 ratio were significantly lower in patients who died as compared with those who survived (26.33±11.80 versus 47.79±38.18, P=0.023 and 0.60±0.25 versus 1.17±1.02, P=0.019, respectively). In conclusion, decreased proportions of tumor-infiltrating CD4(+) T cells with high percentages of Tregs and reversed CD4/CD8 ratios were significantly associated with the clinical outcome of patients with cervical carcinoma.

Depletion of regulatory T cells facilitates growth of established tumors: a mechanism involving the regulation of myeloid-derived suppressor cells by lipoxin A4

Regulatory T cells (Tregs) are thought to facilitate tumor development by suppressing protective antitumor immune responses. However, recent clinical and laboratory studies show that Tregs are a favorable element against cancer. In this study, we provide evidence that Tregs have both promoting and inhibiting effects on tumors, depending on the stage of tumor development. By using 0.5 mg cyclophosphamide, we constructed a murine liver cancer model in which Tregs were continuously and selectively depleted. Under such conditions, we found that tumor growth was inhibited at early stages but accelerated later on. Analysis of the tumor microenvironment disclosed that long-term Treg depletion by 0.5 mg cyclophosphamide treatment induced Gr-1(+)CD11b(+) myeloid-derived suppressor cells (MDSCs). Ablation of MDSCs by anti-Gr-1 Ab blocked Treg depletion-induced promotion of tumor growth. Furthermore, lipoxygenases 5 and 12, two enzymes participating in the biosynthesis of the lipid anti-inflammatory mediator lipoxin A(4), were upregulated or downregulated by Treg depletion or adoptive transfer. Correspondingly, the levels of lipoxin A(4) were increased or decreased. Lipoxin A(4) thus regulated the induction of MDSCs in response to Treg depletion. These findings suggest that Tregs may play different roles at different stages of tumor growth: promoting early and inhibiting late tumor growth. Our study also suggests that the interplay among Tregs, MDSCs, and lipoxin A(4) tunes the regulation of tumor-associated inflammation.

Different radiosensitivity of CD4(+)CD25(+) regulatory T cells and effector T cells to low dose gamma irradiation in vitro

PURPOSE

To determine the radiosensitivity difference of human Cluster of Differentiation (CD)4(+)CD25(+) regulatory T cells (Treg) and effector T cells to low dose gamma ray and elucidate the underlying mechanisms in vitro.

MATERIALS AND METHODS

Blood samples were collected from five health subjects and five patients with advanced hepatocellular carcinoma (HCC). Treg and CD4(+)CD25⁻ T cells were selected using magnetic microbeads. The proliferative profiles, cytokine secretion, and differential expressions of apoptosis-related proteins in Treg and CD4(+)CD25⁻ T cells were compared using [³H]-thymidine incorporation, Luminex assay and flow cytometry when treated with various low doses of γ-ray.

RESULTS

A dose-dependent reduction of proliferation in response to irradiation which paralleled the induction of apoptosis existed in Treg and CD4(+)CD25⁻ T cells. Treg were more radiosensitive to low-dose irradiation (0.94 Gray [Gy]) than effector T cells. The interferon-γ (IFNγ) was significantly upregulated and interleukin 10 (IL-10) was significantly downregulated in irradiated Treg. An enhanced immune response to low dose gamma ray existed in the peripheral blood in patients with advanced HCC. Higher levels of active caspase-3, CD95, B cell lymphoma 2 (Bcl-2)-associated X protein (Bax) expression were observed in Treg compared to CD4(+)CD25⁻ T cells. In addition, gamma irradiation activated CD4(+)CD25⁻ T cells to express CD25.

CONCLUSIONS

These studies revealed that Treg were more radiosensitive than CD4(+)CD25⁻ T cells to low dose irradiation. Higher expressions of apoptosis-related proteins such as caspase-3, CD95 and Bax were observed in Treg when compared to CD4(+)CD25⁻ T cells. Our results suggest that treatment with low doses of gamma irradiation may be a viable strategy to enhance immune response in patients with advanced HCC.

Treatment combining RU486 and Ad5IL-12 vector attenuates the growth of experimentally formed prostate tumors and induces changes in the sentinel lymph nodes of mice

BACKGROUND

Tumor immune responses are first generated and metastases often begin in tumor sentinel lymph nodes (TSLN). Therefore, it is important to promote tumor immunity within this microenvironment. Mifepristone (RU486) treatment can interfere with cortisol signaling that can lead to suppression of tumor immunity. Here, we assessed whether treatment with RU486 in conjunction with an intratumor injection of Ad5IL-12 vector (a recombinant adenovirus expressing IL-12) could impact the TSLN microenvironment and prostate cancer progression.

METHODS

The human PC3, LNCaP or murine TRAMP-C1 prostate cancer cell lines were used to generate subcutaneous tumors in NOD.scid and C57BL/6 mice, respectively. Adjuvant effects of RU486 were looked for in combination therapy with intratumor injections (IT) of Ad5IL-12 vector in comparison to PBS, DL70-3 vector, DL70-3 + RU486, RU486 and Ad5IL-12 vector treatment controls. Changes in tumor growth, cell cytotoxic activity and populations of CD4+/FoxP3+ T regulatory cells (Treg) in the TSLN were evaluated.

RESULTS

Treatment of human PC3 prostate xenograft or TRAMP-C1 tumors with combination Ad5IL-12 vector and RU486 produced significantly better therapeutic efficacy in comparison to controls. In addition, we found that combination therapy increased the capacity of TSLN lymphocytes to produce Granzyme B in response to tumor cell targets. Finally, combination therapy tended towards decreases of CD4+/FoxP3+ T regulatory cell populations to be found in the TSLN.

CONCLUSION

Inclusion of RU486 may serve as a useful adjuvant when combined with proinflammatory tumor killing agents by enhancement of the immune response and alteration of the TSLN microenvironment.