In situ vaccination combined with androgen ablation and regulatory T-cell depletion reduces castration-resistant tumor burden in prostate-specific pten knockout mice

Systemic immune profiling of Omicron-infected subjects inoculated with different doses of inactivated virus vaccine

SARS-CoV-2 primary strain-based vaccination exerts a protective effect against Omicron variants-initiated infection, symptom occurrence, and disease severity in a booster-dependent manner. Yet, the underlying mechanisms remain unclear. During the 2022 Omicron outbreak in Shanghai, we enrolled 122 infected adults and 50 uninfected controls who had been unvaccinated or vaccinated with two or three doses of COVID-19 inactive vaccines and performed integrative analysis of 41-plex CyTOF, RNA-seq, and Olink on their peripheral blood samples. The frequencies of HLA-DRhi classical monocytes, non-classical monocytes, and Th1-like Tem tended to increase, whereas the frequency of Treg was reduced by booster vaccine, and they influenced symptom occurrence in a vaccine dose-dependent manner. Intercorrelation and mechanistic analysis suggested that the booster vaccination induced monocytic training, which would prime monocytic activation and maturation rather than differentiating into myeloid-derived suppressive cells upon Omicron infections. Overall, our study provides insights into how booster vaccination elaborates protective immunity across SARS-CoV-2 variants.

Disturbing NLRP3 acetylation and inflammasome assembly inhibits androgen receptor-promoted inflammatory responses and prostate cancer progression

Chronic inflammation is one of the definite factors leading to the occurrence and development of tumors, including prostate cancer (PCa). The androgen receptor (AR) pathway is essential for PCa tumorigenesis and inflammatory response. However, little is known about the AR-regulated NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome pathway in human PCa. In this study, we explored the expression of inflammatory cytokine and AR in high-grade PCa and observed that NLRP3 inflammasome-associated genes were upregulated in high-grade PCa compared with that in low-grade PCa and benign prostatic hyperplasia and were associated with AR expression. In addition, we identified circAR-3-a circRNA derived from the AR gene-which is involved in the AR-regulated inflammatory response and cell proliferation by activating the NLRP3 inflammatory pathway. While circAR-3 overexpression promoted cell proliferation and the inflammatory response, its depletion induced opposite effects. Mechanistically, we noted that circAR-3 mediated the acetylation modification of NLRP3 by KAT2B and then promoted NLRP3 inflammasome complex subcellular distribution and assembly. Disturbing NLRP3 acetylation or blocking inflammasome assembly with an inhibitor suppressed the progression of PCa xenograft tumors. Our findings provide the first evidence that targeting NLRP3 acetylation or inflammasome assembly may be effective in inhibiting PCa progression.

Comprehensive characterization of TNFSF14/LIGHT with implications in prognosis and immunotherapy of human gliomas

Glioblastoma multiforme (GBM) is a common central neural system malignant tumor among adults. Alongside its microscopic spread, immunosuppression in the tumor microenvironment also induces its refractoriness, which makes immunotherapy for GBM particularly important. Unfortunately, traditional immune checkpoint inhibitors (ICIs) often show limited therapeutic effects in GBM clinical trials, and new therapeutic strategies or targets are urgently needed. TNFSF14/LIGHT is a novel immune checkpoint molecule that plays essential roles in both innate and acquired immunity. Despite recent advances in our understanding of the function of TNFSF14/LIGHT in a variety of cancer types, the clinical and immunological importance of TNFSF14/LIGHT in human gliomas has not been fully explained. Here, we employed a comprehensive in silico analysis with publicly available data to analyze the molecular and immune characteristics of TNFSF14/LIGHT to explore its feasibility as an immunotherapy target. Totally, 2215 glioma cases were enrolled in the current study. Immunohistochemistry staining based on patient tissues (n = 34) was performed for the validation. TNFSF14/LIGHT was expressed higher in higher-WHO-grade gliomas and mesenchymal subtypes, and it was sensitive as a prognostic marker in GBM and low-grade glioma (LGG). A nomogram prognostic model was established based on TNFSF14/LIGHT expression together with other risk factors. Additionally, Gene Ontology and pathway analysis revealed that TNFSF14/LIGHT participated in T-cell activities and inflammatory processes. Moreover, analysis based on the structure and interactions of TNFSF14/LIGHT revealed its mutation sites in tumors as well as crucial interacting proteins. Analysis of IMvigor210 indicated the role of TNFSF14/LIGHT in immunotherapy. Altogether, our results reveal an underlying role of TNFSF14/LIGHT as an immunotherapy target in GBM.

The evolving role of immune cells in prostate cancer

Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death among men in western countries. Androgen deprivation therapy (ADT) is considered the standard therapy for recurrent prostate cancer; however, this therapy may lead to ADT resistance and tumor progression, which seems to be regulated by epithelial-mesenchymal transition (EMT) and/or neuroendocrine differentiation (NED). In addition, recent data suggested the involvement of either adaptive or innate infiltrated immune cells in the initiation, progression, metastasis, and treatment of prostate cancer. In this review, we outlined the characteristics and roles of these immune cells in the initiation, progression, metastasis, and treatments of prostate cancer. We also summarized the current therapeutic strategies in targeting immune cells of the prostate tumor microenvironment.

The role of regulatory T cells in the pathogenesis and treatment of prostate cancer

Despite developments in the treatment of various cancers, prostate cancer is one of the deadliest diseases known to men. Systemic therapies such as androgen deprivation, chemotherapy, and radiation therapy have not been very successful in treating this disease. Numerous studies have shown that there is a direct relationship between cancer progression and inhibition of anti-tumor immune responses that can lead to progression of various malignancies, including prostate cancer. Interestingly, CD4⁺CD25⁺FoxP3⁺ regulatory T cells significantly accumulate and increase in draining lymph nodes and PBMCs of patients with prostate cancer and other solid tumors. In vivo and in vitro studies have shown that Tregs can suppress anti-tumor responses, which is directly related to the increased risk of cancer recurrence. Tregs are essential for preserving self-tolerance and inhibiting extra immune responses harmful to the host. Since the tumor-related antigens are mainly self-antigens, Tregs could play a major role in tumor progression. Accordingly, it has discovered that prostate cancer patients with higher Tregs have poor prognosis and low survival rates. However, anti-tumor responses can be reinforced by suppression of Tregs with using monoclonal antibodies against CD25 and CTLA-4. Therefore, depleting Tregs or suppressing their functions could be one of the effective ways for prostate cancer immunotherapy. The purpose of this review is to investigate the role of Treg cells in the progression of prostate cancer and to evaluate effective strategies for the treatment of prostate cancer by regulating Treg cells.

Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis

Tuberous sclerosis complex (TSC) represents the prototypic monogenic disorder of the mammalian target of rapamycin (mTOR) pathway dysregulation. It provides the rational mechanistic basis of a direct link between gene mutation and brain pathology (structural and functional abnormalities) associated with a complex clinical phenotype including epilepsy, autism, and intellectual disability. So far, research conducted in TSC has been largely neuron-oriented. However, the neuropathological hallmarks of TSC and other malformations of cortical development also include major morphological and functional changes in glial cells involving astrocytes, oligodendrocytes, NG2 glia, and microglia. These cells and their interglial crosstalk may offer new insights into the common neurobiological mechanisms underlying epilepsy and the complex cognitive and behavioral comorbidities that are characteristic of the spectrum of mTOR-associated neurodevelopmental disorders. This review will focus on the role of glial dysfunction, the interaction between glia related to mTOR hyperactivity, and its contribution to epileptogenesis in TSC. Moreover, we will discuss how understanding glial abnormalities in TSC might give valuable insight into the pathophysiological mechanisms that could help to develop novel therapeutic approaches for TSC or other pathologies characterized by glial dysfunction and acquired mTOR hyperactivation.

Role of tumor-associated immune cells in prostate cancer: angel or devil?

Prostate cancer is the most common malignancy in the reproductive system of older males. Androgen deprivation therapy (ADT) is an important treatment for prostate cancer patients. However, almost all prostate cancer patients unavoidably progress to the castration-resistant stage after ADT treatment. Recent studies have shown that tumor-associated immune cells play major roles in the initiation, progression, and metastasis of prostate cancer. Various phenotypes of tumor-associated immune cells have tumor-promoting or antitumor functions mediated by interacting with tumor cells. Here, we review the current knowledge of tumor-associated immune cells in prostate cancer.

Influence of Androgens on Immunity to Self and Foreign: Effects on Immunity and Cancer

It is well-known that sex hormones can directly and indirectly influence immune cell function. Different studies support a suppressive role of androgens on different components of the immune system by decreasing antibody production, T cell proliferation, NK cytotoxicity, and stimulating the production of anti-inflammatory cytokines. Androgen receptors have also been detected in many different cells of hematopoietic origin leading to direct effects of their ligands on the development and function of the immune system. The immunosuppressive properties of androgens could contribute to gender dimorphisms in autoimmune and infectious disease and thereby also hamper immune surveillance of tumors. Consistently, females generally are more prone to autoimmunity, while relatively less susceptible to infections, and have lower incidence and mortality of the majority of cancers compared to males. Some studies show that androgen deprivation therapy (ADT) can induce expansion of naïve T cells and increase T-cell responses. Emerging clinical data also reveal that ADT might enhance the efficacy of various immunotherapies including immune checkpoint blockade. In this review, we will discuss the potential role of androgens and their receptors in the immune responses in the context of different diseases. A particular focus will be on cancer, highlighting the effect of androgens on immune surveillance, tumor biology and on the efficacy of anti-cancer therapies including emerging immune therapies.

A QSP model of prostate cancer immunotherapy to identify effective combination therapies

Immunotherapy, by enhancing the endogenous anti-tumor immune responses, is showing promising results for the treatment of numerous cancers refractory to conventional therapies. However, its effectiveness for advanced castration-resistant prostate cancer remains unsatisfactory and new therapeutic strategies need to be developed. To this end, systems pharmacology modeling provides a quantitative framework to test in silico the efficacy of new treatments and combination therapies. In this paper we present a new Quantitative Systems Pharmacology (QSP) model of prostate cancer immunotherapy, calibrated using data from pre-clinical experiments in prostate cancer mouse models. We developed the model by using Ordinary Differential Equations (ODEs) describing the tumor, key components of the immune system, and seven treatments. Numerous combination therapies were evaluated considering both the degree of tumor inhibition and the predicted synergistic effects, integrated into a decision tree. Our simulations predicted cancer vaccine combined with immune checkpoint blockade as the most effective dual-drug combination immunotherapy for subjects treated with androgen-deprivation therapy that developed resistance. Overall, the model presented here serves as a computational framework to support drug development, by generating hypotheses that can be tested experimentally in pre-clinical models.

Increased mortality in elderly patients with acute respiratory distress syndrome is not explained by host response

Background

Advanced age is associated with increased mortality in acute respiratory distress syndrome (ARDS) patients. Preclinical studies suggest that the host response to an injurious challenge is age-dependent. In ARDS patients, we investigated whether the association between age and mortality is mediated through age-related differences in the host response.

Methods

This was a prospective longitudinal observational cohort study, performed in the ICUs of two university-affiliated hospitals. The systemic host response was characterized in three predefined age-groups, based on the age-tertiles of the studied population: young (18 to 54 years, N = 209), middle-aged (55 to 67 years, N = 213), and elderly (67 years and older, N = 196). Biomarkers of inflammation, endothelial activation, and coagulation were determined in plasma obtained at the onset of ARDS. The primary outcome was 90-day mortality. A mediation analysis was performed to examine whether age-related differences in biomarker levels serve as potential causal pathways mediating the association between age and mortality.

Results

Ninety-day mortality rates were 30% (63/209) in young, 37% (78/213) in middle-aged, and 43% (84/196) in elderly patients. Middle-aged and elderly patients had a higher risk of death compared to young patients (adjusted odds ratio, 1.5 [95% confidence interval 1.0 to 2.3] and 2.1 [1.4 to 3.4], respectively). Relative to young patients, the elderly had significantly lower systemic levels of biomarkers of inflammation and endothelial activation. Tissue plasminogen activator, a marker of coagulation, was the only biomarker that showed partial mediation (proportion of mediation, 10 [1 to 28] %).

Conclusion

Little evidence was found that the association between age and mortality in ARDS patients is mediated through age-dependent differences in host response pathways. Only tissue plasminogen activator was identified as a possible mediator of interest.

Trial registration

This trial was registered at ClinicalTrials.gov (identifier NCT01905033, date of registration July 23, 2013).

Systematically understanding the immunity leading to CRPC progression

Prostate cancer (PCa) is the most commonly diagnosed malignancy and the second leading cause of cancer-related death in American men. Androgen deprivation therapy (ADT) has become a standard treatment strategy for advanced PCa. Although a majority of patients initially respond to ADT well, most of them will eventually develop castration-resistant PCa (CRPC). Previous studies suggest that ADT-induced changes in the immune microenvironment (mE) in PCa might be responsible for the failures of various therapies. However, the role of the immune system in CRPC development remains unclear. To systematically understand the immunity leading to CRPC progression and predict the optimal treatment strategy in silico, we developed a 3D Hybrid Multi-scale Model (HMSM), consisting of an ODE system and an agent-based model (ABM), to manipulate the tumor growth in a defined immune system. Based on our analysis, we revealed that the key factors (e.g. WNT5A, TRAIL, CSF1, etc.) mediated the activation of PC-Treg and PC-TAM interaction pathways, which induced the immunosuppression during CRPC progression. Our HMSM model also provided an optimal therapeutic strategy for improving the outcomes of PCa treatment.

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in American men. Androgen deprivation therapy (ADT) is the first-line therapy for advanced PCa, yet a significant number of primary PCa patients treated with ADT eventually develop incurable castration-resistant prostate cancer (CRPC). Recent observations suggest that the immunosuppressive microenvironment of PCa might be responsible for the failures of various therapies. However, the role of immune system in CRPC progression is still unclear. To deeply understand the immunity leading to CRPC progression, we developed a unique systems biology approach (HMSM). Based on our analysis, we identified the key molecules (e.g. WNT5A, TRAIL, CSF1, etc.) mediating the communication of PCa and immune cells. Our HMSM system also revealed the optimal therapeutic strategy for PCa treatment. Collectively, our study provides a new insight to study tumor-related immune mechanisms and pave the way for the development of more effective treatments.

Androgen deprivation and immunotherapy for the treatment of prostate cancer

Prostate cancer is the most common newly diagnosed malignancy in men, and the second most common cause of cancer-related death in the United States. The primary treatment for recurrent prostate cancer is androgen deprivation, and this therapy is typically continued lifelong for patients with metastatic prostate cancer. Androgens and androgen deprivation have profound effects on the immune system, a finding that has become more appreciated in an era where immune-based treatments for cancer are being increasingly explored. Preclinical studies suggest that androgen deprivation could potentially positively or negatively affect the use of approved immunotherapies, or those that are being developed for the treatment of prostate cancer. In this review, we provide a brief overview of the different types of androgen deprivation treatments used in the management of prostate cancer, discuss their effects on prostate tumors and the immune system and how they are being explored in combination with immunotherapy. Finally, we address some of the critical questions in the field that must be answered to identify the best approaches to combine androgen deprivation with immunotherapy for the treatment of prostate cancer.

Prostate Cancer Cells Express More Androgen Receptor (AR) Following Androgen Deprivation, Improving Recognition by AR-Specific T Cells

Androgen deprivation is the primary therapy for recurrent prostate cancer, and agents targeting the androgen receptor (AR) pathway continue to be developed. Because androgen-deprivation therapy (ADT) has immmunostimulatory effects as well as direct antitumor effects, AR-targeted therapies have been combined with other anticancer therapies, including immunotherapies. Here, we sought to study whether an antigen-specific mechanism of resistance to ADT (overexpression of the AR) may result in enhanced AR-specific T-cell immune recognition, and whether this might be strategically combined with an antitumor vaccine targeting the AR. Androgen deprivation increased AR expression in human and murine prostate tumor cells in vitro and in vivo The increased expression persisted over time. Increased AR expression was associated with recognition and cytolytic activity by AR-specific T cells. Furthermore, ADT combined with vaccination, specifically a DNA vaccine encoding the ligand-binding domain of the AR, led to improved antitumor responses as measured by tumor volumes and delays in the emergence of castrate-resistant prostate tumors in two murine prostate cancer models (Myc-CaP and prostate-specific PTEN-deficient mice). Together, these data suggest that ADT combined with AR-directed immunotherapy targets a major mechanism of resistance, overexpression of the AR. This combination may be more effective than ADT combined with other immunotherapeutic approaches. Cancer Immunol Res; 5(12); 1074-85. ©2017 AACR.

Changes in regulatory T cells in patients with ovarian cancer undergoing surgery: Preliminary results

Regulatory T cells (Treg) suppress immune responses in patients with cancer. Surgery is the most effective therapeutic strategy for ovarian cancer (OC). However, the interplay between the Treg population and surgical resection remains unclear. 61 patients with OC who received no prior treatment were enrolled in the study. Treg percentages were characterized from peripheral blood mononuclear cells. We investigated CD4⁺CD25⁺, CD4⁺CD25⁺Foxp3⁺, CD8⁺CD28^-, and CD8⁺Foxp3⁺ Tregs in OC patients and their postoperative changes using flow cytometry. Treg percentages were significantly higher in OC patients than those in benign ovarian tumors (BOT) and healthy controls. Higher percentages of Tregs were found in patients with stage III/IV than stage I/II OC. Treg percentages were significantly decreased postoperatively. The postoperative Treg percentages in patients with stage I/II OC were similar to those in BOT patients, while postoperative Treg percentages in patients with stage III/IV OC remained higher. Tregs were markedly lower on postoperative day (POD) 3 than preoperatively. They increased slightly after 7days, but remained lower than preoperative levels. These data suggested that Tregs continued to decline from POD 7 to POD 30. Treg percentages are correlated with the tumor burden and could be a key factor in monitoring the immunological status of patients with OC.

Androgen regulation of host defenses and response to inflammatory stimuli in the prostate gland

The prostate gland is a strictly androgen-dependent organ which is also the main target of infectious and inflammatory diseases in the male reproductive tract. Host defenses and immunity of the gland have unique features to maintain a constant balance between response and tolerance to diverse antigens. In this context, the effects of reproductive hormones on the male tract are thus complex and have just started to be defined. From the classical description of "the prostatic antibacterial factor," many host defense proteins with potent microbicidal and anti-tumoral activities have been described in the organ. Indeed, it has been proposed a central role for resident cells, that is, epithelial and smooth muscle cells, in the prostatic response against injuries. However, these cells also represent the target of the inflammatory damage, leading to the development of a Proliferative Inflammatory Atrophy-like process in the epithelium and a myofibroblastic-like reactive stroma. Available data on androgen regulation of inflammation led to a model of the complex control, in which the final effect will depend on the tissue microenvironment, the cause of inflammation, and the levels of androgens among other factors. In this paper, we review the current scientific literature about the inflammatory process in the gland, the modulation of host defense proteins, and the influence of testosterone on the resolution of prostatitis.

Immune mediators in the tumor microenvironment of prostate cancer

Prostate cancer tissue is composed of both cancer cells and host cells. The milieu of host components that compose the tumor is termed the tumor microenvironment (TME). Host cells can be those derived from the tissue in which the tumor originates (e.g., fibroblasts and endothelial cells) or those recruited, through chemotactic or other factors, to the tumor (e.g., circulating immune cells). Some immune cells are key players in the TME and represent a large proportion of non-tumor cells found within the tumor. Immune cells can have both anti-tumor and pro-tumor activity. In addition, crosstalk between prostate cancer cells and immune cells affects immune cell functions. In this review, we focus on immune cells and cytokines that contribute to tumor progression. We discuss T-regulatory and T helper 17 cells and macrophages as key modulators in prostate cancer progression. In addition, we discuss the roles of interleukin-6 and receptor activator of nuclear factor kappa-B ligand in modulating prostate cancer progression. This review highlights the concept that immune cells and cytokines offer a potentially promising target for prostate cancer therapy.

DNA vaccines for prostate cancer

DNA vaccines offer many advantages over other anti-tumor vaccine approaches due to their simplicity, ease of manufacturing, and safety. Results from several clinical trials in patients with cancer have demonstrated that DNA vaccines are safe and can elicit immune responses. However, to date few DNA vaccines have progressed beyond phase I clinical trial evaluation. Studies into the mechanism of action of DNA vaccines in terms of antigen-presenting cell types able to directly present or cross-present DNA-encoded antigens, and the activation of innate immune responses due to DNA itself, have suggested opportunities to increase the immunogenicity of these vaccines. In addition, studies into the mechanisms of tumor resistance to anti-tumor vaccination have suggested combination approaches that can increase the anti-tumor effect of DNA vaccines. This review focuses on these mechanisms of action and mechanisms of resistance using DNA vaccines, and how this information is being used to improve the anti-tumor effect of DNA vaccines. These approaches are then specifically discussed in the context of human prostate cancer, a disease for which DNA vaccines have been and continue to be explored as treatments.

Prediction of treatment efficacy for prostate cancer using a mathematical model

Prostate immune system plays a critical role in the regulation of prostate cancer development regarding androgen-deprivation therapy (ADT) and/or immunotherapy (vaccination). In this study, we developed a mathematical model to explore the interactions between prostate tumor and immune microenvironment. This model was used to predict treatment outcomes for prostate cancer with ADT, vaccination, Treg depletion and/or IL-2 neutralization. Animal data were used to guide construction, parameter selection, and validation of our model. Our analysis shows that Treg depletion and/or IL-2 neutralization can effectively improve the treatment efficacy of combined therapy with ADT and vaccination. Treg depletion has a higher synergetic effect than that from IL-2 neutralization. This study highlights a potential therapeutic strategy in effectively managing prostate tumor growth and provides a framework of systems biology approach in studying tumor-related immune mechanism and consequent selection of therapeutic regimens.

Exploiting synergy: immune-based combinations in the treatment of prostate cancer

Cancer treatment is being revolutionized by the emergence of immunotherapies such as immune checkpoint inhibitors and therapeutic cancer vaccines. Prostate cancer is amenable to such therapeutic approaches. The improved understanding of the relationship between the immune system and tumors has allowed therapeutic targeting of immune checkpoints and tumor associated antigens to be developed. Furthermore, interventions used in prostate cancer are capable of impacting the immune system. As demonstrated by preclinical data and emerging clinical data, radiation therapy, anti-androgen therapy, and chemotherapy can be used with immunotherapies to obtain synergistic results. Current and future clinical trials will further investigate these principles as immunotherapeutics are combined with each other and standard therapies for optimal clinical utility.

Opposing effects of androgen ablation on immune function in prostate cancer

Although it is recognized that immune function is modulated by androgen ablation therapy for prostate cancer, the long-term consequences are not completely understood. We recently showed that both effector and inhibitory immune mechanisms are amplified by androgen ablation, providing one explanation for only transient increases in immune function after castration.

Preclinical and clinical development of DNA vaccines for prostate cancer

Prostate cancer is the most commonly diagnosed cancer in the United States. It is also the second leading cause of cancer-related death in men, making it one of the largest public health concerns today. Prostate cancer is an ideal disease for immunotherapies because of the generally slow progression, the dispensability of the target organ in the patient population, and the availability of several tissue-specific antigens. As such, several therapeutic vaccines have entered clinical trials, with one autologous cellular vaccine (sipuleucel-T) recently gaining Food and Drug Administration approval after demonstrating overall survival benefit in randomized phase III clinical trials. DNA-based vaccines are safe, economical, alternative "off-the-shelf" approaches that have undergone extensive evaluation in preclinical models. In fact, the first vaccine approved in the United States for the treatment of cancer was a DNA vaccine for canine melanoma. Several prostate cancer-specific DNA vaccines have been developed in the last decade and have shown promising results in early phase clinical trials. This review summarizes anticancer human DNA vaccine trials, with a focus on those conducted for prostate cancer. We conclude with an outline of special considerations important for the development and successful translation of DNA vaccines from the laboratory to the clinic.

T cells localized to the androgen-deprived prostate are TH1 and TH17 biased

BACKGROUND

T cells infiltrate the prostates of prostate cancer patients undergoing neoadjuvant androgen deprivation. These prostate-infiltrating T cells have an oligoclonal phenotype, suggesting the development of an antigen-specific T-cell response. We hypothesized that androgen deprivation might elicit a prostate tissue-specific T-cell response that could potentially be combined with other immune-active therapies, and consequently sought to investigate the nature and timing of this T-cell response following castration.

METHODS

We investigated the phenotype and cytokine expression of T cells at various time points in the prostates of Lewis rats following surgical castration, and used adoptive transfer of prostate-infiltrating lymphocytes (PILs) to determine whether the infiltration by T cells was mediated by effects of castration on the prostate or lymphocytes.

RESULTS

Prostate T-cell infiltration shortly after castration was T(H) 1 biased up to approximately 30 days, followed by a predominance of T(H) 17-type cells, which persisted until at least 90 days post castration. PILs from sham-treated or castrate rats localized to the prostates of castrate animals.

CONCLUSIONS

These observations suggest castration elicits a time-dependent prostate-specific T-cell infiltration, and this infiltration is likely mediated by effects of castration on prostate tissue rather than T-cells. These findings have implications for the timing of immunotherapies combined with androgen deprivation as treatments for prostate cancer.

Increased CD8+ T-cell function following castration and immunization is countered by parallel expansion of regulatory T cells

Although androgen ablation therapy is effective in treating primary prostate cancers, a significant number of patients develop incurable castration-resistant disease. Recent studies have suggested a potential synergy between vaccination and androgen ablation, yet the enhanced T-cell function is transient. Using a defined tumor antigen model, UV-8101-RE, we found that concomitant castration significantly increased the frequency and function of antigen-specific CD8(+) T cells early after the immunization of wild-type mice. However, at a late time point after immunization, effector function was reduced to the same level as noncastrated mice and was accompanied by a concomitant amplification in CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) following immunization. We investigated whether Treg expansion occurred following castration of prostate tumor-bearing mice. In the prostate-specific Pten(-/-) mouse model of prostate cancer, we observed an accelerated Treg expansion in mice bearing the castration-resistant endogenous prostate tumor, which prevented effector responses to UV-8101-RE. Treg depletion together with castration elicited a strong CD8(+) T-cell response to UV-8101-RE in Pten(-/-) mice and rescued effector function in castrated and immunized wild-type mice. In addition, Treg expansion in Pten(-/-) mice was prevented by in vivo interleukin (IL)-2 blockade suggesting that increased IL-2 generated by castration and immunization promotes Treg expansion. Our findings therefore suggest that although effector responses are augmented by castration, the concomitant expansion of Tregs is one mechanism responsible for only transient immune potentiation after androgen ablation.

Regulatory T-cell depletion synergizes with gp96-mediated cellular responses and antitumor activity

Despite its potent immunostimulatory properties, vaccination with autologous tumor-derived gp96 has relatively modest antitumor effect in a range of clinical trials. Based on our previous study showing a gp96-mediated immune balance between CTL and Tregs, here we investigated possible synergy between gp96 vaccine and systemic Treg depletion on induction of antitumor T-cell immunity and the mechanisms accounting for synergistic efficacy. In gp96-peptide complex immunized BALB/c mice, anti-CD25 mAb treatment significantly increased IFN-γ-producing CD8(+) and CD4(+) T cells by about 1-2-fold in spleen and 40-50% in lymph node. A significantly higher number of peptide-specific CTL were observed under anti-CD25 mAb treatment compared with no treatment. Moreover, Treg depletion synergistically improved the anticancer activity of tumor-derived gp96 vaccine in the poorly immunogenic and highly tumorigenic B16 melanoma model in C57BL/6 J mice. While gp96 immunization alone led to the modest enhancement of CTL activities in spleen, the combination with Treg depletion dramatically increased tumor-specific CTL responses. In addition, the combination resulted in a significant increase of CD8(+) T-cell infiltration in tumor, which correlated with an enhanced inhibition of tumor growth. Our results provide evidence that targeting Tregs may provide a more efficient strategy to potentiate gp96-mediated T-cell responses and enhance the antitumor efficiency of gp96-based therapeutic vaccine.

The PCa Tumor Microenvironment

The tumor microenvironment (TME) is a very complex niche that consists of multiple cell types, supportive matrix and soluble factors. Cells in the TME consist of both host cells that are present at tumor site at the onset of tumor growth and cells that are recruited in either response to tumor- or host-derived factors. PCa (PCa) thrives on crosstalk between tumor cells and the TME. Crosstalk results in an orchestrated evolution of both the tumor and microenvironment as the tumor progresses. The TME reacts to PCa-produced soluble factors as well as direct interaction with PCa cells. In return, the TME produces soluble factors, structural support and direct contact interactions that influence the establishment and progression of PCa. In this review, we focus on the host side of the equation to provide a foundation for understanding how different aspects of the TME contribute to PCa progression. We discuss immune effector cells, specialized niches, such as the vascular and bone marrow, and several key protein factors that mediate host effects on PCa. This discussion highlights the concept that the TME offers a potentially very fertile target for PCa therapy.

Slow disease progression in a C57BL/6 pten-deficient mouse model of prostate cancer

Prostate-specific deletion of Pten in mice has been reported to recapitulate histological progression of human prostate cancer. To improve on this model, we introduced the conditional ROSA26 luciferase reporter allele to monitor prostate cancer progression via bioluminescence imaging and extensively backcrossed mice onto the albino C57BL/6 genetic background to address variability in tumor kinetics and to enhance imaging sensitivity. Bioluminescence signal increased rapidly in Pten(p-/-) mice from 3 to 11 weeks, but was much slower from 11 to 52 weeks. Changes in bioluminescence signal were correlated with epithelial proliferation. Magnetic resonance imaging revealed progressive increases in prostate volume, which were attributed to excessive fluid retention in the anterior prostate and to expansion of the stroma. Development of invasive prostate cancer in 52-week-old Pten(p-/-) mice was rare, indicating that disease progression was slowed relative to that in previous reports. Tumors in these mice exhibited a spontaneous inflammatory phenotype and were rapidly infiltrated by myeloid-derived suppressor cells. Although Pten(p-/-) tumors responded to androgen withdrawal, they failed to exhibit relapsed growth for up to 1 year. Taken together, these data identify a mild prostate cancer phenotype in C57BL/6 prostate-specific Pten-deficient mice, reflecting effects of the C57BL/6 genetic background on cancer progression. This model provides a platform for noninvasive assessment of how genetic and environmental risk factors may affect disease progression.

Increased liver-infiltrating CD8+FoxP3+ regulatory T cells are associated with tumor stage in hepatocellular carcinoma patients

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver, and patients who are diagnosed with this tumor typically have a poor prognosis. The suppressive effects of CD4(+)FoxP3(+) regulatory T cells on antitumor immune response in HCC have been studied in great detail. CD8(+)FoxP3(+) regulatory T cells have recently been detected in tumors; however, the role of CD8(+)FoxP3(+) regulatory T cells in HCC is still unknown. Here, the frequency and phenotype of CD8(+)FoxP3(+) regulatory T cells were analyzed by multicolor flow cytometry in liver of HCC patients and healthy donors. We observed that the percentage of these cells in HCC patients was significantly higher than that observed in healthy control donors (p = 0.0155); their phenotype was close to that of CD4(+) regulatory T cells. Furthermore, we show that CD8(+)FoxP3(+) regulatory T cells are activated and act as effector memory cells (EM, CD45RA(-)CCR7(-)CD27(+/-)CD28(+)). Most importantly, a higher percentage of intrahepatic CD8(+)FoxP3(+) regulatory T cells was found in patients with advanced HCC than in those with early HCC in terms of tumor-node-metastasis (TNM) stage (stage I vs III, p = 0.0007). These data suggest that CD8(+)FoxP3(+) regulatory T cells may contribute to HCC immune escape and disease progression.