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

Sequence of androgen receptor-targeted vaccination with androgen deprivation therapy affects anti-prostate tumor efficacy

RATIONALE

Androgen deprivation therapy (ADT) is the primary treatment for recurrent and metastatic prostate cancer. In addition to direct antitumor effects, ADT has immunomodulatory effects such as promoting T-cell infiltration and enhancing antigen processing/presentation. Previous studies in our laboratory have demonstrated that ADT also leads to increased expression of the androgen receptor (AR) and increased recognition of prostate tumor cells by AR-specific CD8+T cells. We have also demonstrated that ADT combined with a DNA vaccine encoding the AR significantly slowed tumor growth and improved the survival of prostate tumor-bearing mice. The current study aimed to investigate the impact of the timing and sequencing of ADT with vaccination on the tumor immune microenvironment in murine prostate cancer models to further increase the antitumor efficacy of vaccines.

METHODS

Male FVB mice implanted with Myc-CaP tumor cells, or male C57BL/6 mice implanted with TRAMP-C1 prostate tumor cells, were treated with a DNA vaccine encoding AR (pTVG-AR) and ADT. The sequence of administration was evaluated for its effect on tumor growth, and tumor-infiltrating immune populations were characterized.

RESULTS

Vaccination prior to ADT (pTVG-AR → ADT) significantly enhanced antitumor responses and survival. This was associated with increased tumor infiltration by CD4+ and CD8+ T cells, including AR-specific CD8+T cells. Depletion of CD8+T cells prior to ADT significantly worsened overall survival. Following ADT treatment, however, Gr1+ myeloid-derived suppressor cells (MDSCs) increased, and this was associated with fewer infiltrating T cells and reduced tumor growth. Inhibiting Gr1+MDSCs recruitment, either by using a CXCR2 antagonist or by cycling androgen deprivation with testosterone replacement, improved antitumor responses and overall survival.

CONCLUSION

Vaccination prior to ADT significantly improved antitumor responses, mediated in part by increased infiltration of CD8+T cells following ADT. Targeting MDSC recruitment following ADT further enhanced antitumor responses. These findings suggest logical directions for future clinical trials to improve the efficacy of prostate cancer vaccines.

Cancer Cell-Extrinsic Roles for the Androgen Receptor in Prostate Cancer

Given the central role of the androgen receptor (AR) in prostate cancer cell biology, AR-targeted therapies have been the backbone of prostate cancer treatment for over 50 years. New data indicate that AR is expressed in additional cell types within the tumor microenvironment. Moreover, targeting AR for the treatment of prostate cancer has established side effects such as bone complications and an increased risk of developing cardiometabolic disease, indicating broader roles for AR. With the advent of novel technologies, such as single-cell approaches and advances in preclinical modeling, AR has been identified to have clinically significant functions in other cell types. In this mini-review, we describe new cancer cell-extrinsic roles for AR within the tumor microenvironment as well as systemic effects that collectively impact prostate cancer progression and patient outcomes.

Immune checkpoint therapy-current perspectives and future directions

Immune checkpoint therapy (ICT) has dramatically altered clinical outcomes for cancer patients and conferred durable clinical benefits, including cure in a subset of patients. Varying response rates across tumor types and the need for predictive biomarkers to optimize patient selection to maximize efficacy and minimize toxicities prompted efforts to unravel immune and non-immune factors regulating the responses to ICT. This review highlights the biology of anti-tumor immunity underlying response and resistance to ICT, discusses efforts to address the current challenges with ICT, and outlines strategies to guide the development of subsequent clinical trials and combinatorial efforts with ICT.

Next Generation of Androgen Deprivation Therapy Combined With Radiotherapy for N0 M0 Prostate Cancer

Androgen deprivation therapy in combination with definitive radiation therapy is a standard of care for both intermediate-/high-risk localized prostate, locally advanced prostate cancer. Newer hormonal therapies have shown promising results in patients with castration-resistant disease and are now being investigated in early stages, in combination with radiation therapy. In this section, we review the body of evidence elucidating the mechanism of synergy and immune modulation effect of androgen deprivation therapy and radiation therapy, summarize the pivotal studies supporting its use in the nonmetastatic setting, and present the ongoing studies who will likely shape the management of locally advanced disease, in the upcoming years.

Treatment Combinations with DNA Vaccines for the Treatment of Metastatic Castration-Resistant Prostate Cancer (mCRPC)

Simple Summary

The only vaccine approved by FDA as a treatment for cancer is sipuleucel-T, a therapy for patients with metastatic castration-resistant prostate cancer (mCRPC). Most investigators studying anti-tumor vaccines believe they will be most effective as parts of combination therapies, rather than used alone. Unfortunately, the cost and complexity of sipuleucel-T makes it difficult to feasibly be used in combination with many other agents. In this review article we discuss the use of DNA vaccines as a simpler vaccine approach that has demonstrated efficacy in several animal species. We discuss the use of DNA vaccines in combination with traditional treatments for mCRPC, and other immune-modulating treatments, in preclinical and early clinical trials for patients with mCRPC.

Abstract

Metastatic castration-resistant prostate cancer (mCRPC) is a challenging disease to treat, with poor outcomes for patients. One antitumor vaccine, sipuleucel-T, has been approved as a treatment for mCRPC. DNA vaccines are another form of immunotherapy under investigation. DNA immunizations elicit antigen-specific T cells that cause tumor cell lysis, which should translate to meaningful clinical responses. They are easily amenable to design alterations, scalable for large-scale manufacturing, and thermo-stable for easy transport and distribution. Hence, they offer advantages over other vaccine formulations. However, clinical trials with DNA vaccines as a monotherapy have shown only modest clinical effects against tumors. Standard therapies for CRPC including androgen-targeted therapies, radiation therapy and chemotherapy all have immunomodulatory effects, which combined with immunotherapies such as DNA vaccines, could potentially improve treatment. In addition, many investigational drugs are being developed which can augment antitumor immunity, and together with DNA vaccines can further enhance antitumor responses in preclinical models. We reviewed the literature available prior to July 2020 exploring the use of DNA vaccines in the treatment of prostate cancer. We also examined various approved and experimental therapies that could be combined with DNA vaccines to potentially improve their antitumor efficacy as treatments for mCRPC.

A review on the interactions between the tumor microenvironment and androgen receptor signaling in prostate cancer

Prostate cancer growth is controlled by androgen receptor signaling via both androgen-dependent and androgen-independent pathways. Furthermore, the prostate is an immune competent organ with inflammatory changes both within the systemic and local environment contributing to the reprogramming of the prostatic epithelium with consistently elevated lymphocyte infiltration and proinflammatory cytokines being found in prostate cancer. The crosstalk between the tumor microenvironment and androgen receptor signaling is complex with both protumorigenic and antitumorigenic roles observed. However, despite an increase in immune checkpoint inhibitors and inflammatory signaling blockades available for a range of cancer types, we are yet to see substantial progress in the treatment of prostate cancer. Therefore, this review aims to summarize the tumor microenvironment and its impact on androgen receptor signaling in prostate cancer.

Androgen deprivation therapy for prostate cancer and the risk of autoimmune diseases

BACKGROUND

Androgen deprivation therapy (ADT) has been a mainstay of treatment for advanced prostate cancer (PCa), but limited studies have been performed to investigate the association between ADT and autoimmune diseases.

METHODS

We conducted a population-based nationwide cohort study of 17,168 patients newly diagnosed with PCa between 1996 and 2013 using the National Health Insurance Research Database (NHIRD) of Taiwan. Cox proportional hazards models with 1:1 propensity score-matched analysis were used to investigate the association between ADT use and the risk of autoimmune diseases. The autoimmune diseases included Graves' disease, Crohn's disease, psoriasis, systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, Guillain-Barre syndrome, Sjogren's syndrome, myasthenia gravis, pernicious anemia, hereditary hemolytic anemia, polyarteritis nodosa, Celiac disease, uveitis, polymyalgia rheumatica, dermatomyositis, Hashimoto's thyroiditis, hypersensitivity vasculitis, Behcet's disease, polymyositis, alopecia areata, Wegener's granulomatosis, ulcerative colitis, autoimmune hemolytic anemia, pemphigus, multiple sclerosis, systemic sclerosis, Goodpasture syndrome, giant cell arteritis, thromboangitis obliterans, arteritis obliterans, and Kawasaki disease. The duration of ADT use as a time-dependent variable was also examined for its association with autoimmune diseases. We also performed six secondary analyses.

RESULTS

Of the 17,168 selected PCa patients, 14,444 patients met all the inclusion and exclusion criteria. After propensity score matching, 5590 ADT users and 5590 non-ADT users were included in the study cohort. A propensity score-matched analysis (adjusted hazard ratio (aHR), 0.619, 95% confidence interval (CI), 0.51-0.75, P < 0.001) demonstrated a significantly decreased risk of autoimmune diseases in ADT users. A significant decrease in the risk of autoimmune diseases with increasing ADT duration was also demonstrated (P < 0.001).

CONCLUSIONS

We observed that ADT use in patients with PCa was associated with a decreased risk of autoimmune diseases. These novel findings provide a potential role for androgen deprivation therapy in the modification of inflammation and autoimmunity in Asian patients with prostate cancer.

Immune infiltrates and PD-L1 expression in treatment-naïve acinar prostatic adenocarcinoma: an exploratory analysis

Tumour-induced immunosuppression plays a role in the development and progression of cancer. Of interest is the interaction between programmed death-1 and programmed death ligand-1 (PD-L1) which can be targeted through immune checkpoint blockade; however, there are limited data surrounding the composition of the immune milieu in prostate cancer. We preliminarily assessed 21 radical prostatectomies in therapy-naïve patients for immune markers and PD-L1 expression. The immune infiltrates were higher in adenocarcinoma than benign prostate (lymphocytes p<0.001, macrophages p=0.010) with 5% of cases being PD-L1 high (≥5% expression). Increased peritumoural CD68 and CD163 expression correlated with lower grade group (GG) (p=0.024 and p=0.014, respectively) with a trend towards increased CD68 expression in lower stage cases (p=0.086). There was also increased CD45 expression in lower GGs (p=0.063). We found the immune infiltrate in acinar prostate cancer to be extremely heterogeneous with an overall immunophenotype unlikely to respond to immune checkpoint blockade.

Sex steroids in the tumor microenvironment and prostate cancer progression

Prostate cancer is uniquely dependent on androgens. Despite years of research on the relationship between androgens and prostate cancer, many questions remain as to the biological effects of androgens and other sex steroids during prostate cancer progression. This article reviews the clinical and basic research on the influence of sex steroids such as androgens, estrogens and progesterone within the prostate tumor microenvironment on the progression of prostate cancer. We review clinical studies to date evaluating serum sex steroids as prognostic biomarkers and discuss their respective biological effects within the prostate tumor microenvironment. We also review the link between genomic alterations and sex steroid levels within prostate tumors. Finally, we highlight the links between sex steroid levels and the function of the immune system within the tumor microenvironment. As the context of treatment of lethal prostate cancer evolves over time, an understanding of this underlying biology remains central to developing optimal treatment approaches.

Potentiating prostate cancer immunotherapy with oncolytic viruses

The clinical effectiveness of immunotherapies for prostate cancer remains subpar compared with that for other cancers. The goal of most immunotherapies is the activation of immune effectors, such as T cells and natural killer cells, as the presence of these activated mediators positively correlates with patient outcomes. Clinical evidence shows that prostate cancer is immunogenic, accessible to the immune system, and can be targeted by antitumour immune responses. However, owing to the detrimental effects of prostate-cancer-associated immunosuppression, even the newest immunotherapeutic approaches fail to initiate the clinically desired antitumour immune reaction. Oncolytic viruses, originally used for their preferential cancer-killing activity, are now being recognized for their ability to overturn cancer-associated immune evasion and promote otherwise absent antitumour immunity. This oncolytic-virus-induced subversion of tumour-associated immunosuppression can potentiate the effectiveness of current immunotherapeutics, including immune checkpoint inhibitors (for example, antibodies against programmed cell death protein 1 (PD1), programmed cell death 1 ligand 1 (PDL1), and cytotoxic T lymphocyte antigen 4 (CTLA4)) and chemotherapeutics that induce immunogenic cell death (for example, doxorubicin and oxaliplatin). Importantly, oncolytic-virus-induced antitumour immunity targets existing prostate cancer cells and also establishes long-term protection against future relapse. Hence, the strategic use of oncolytic viruses as monotherapies or in combination with current immunotherapies might result in the next breakthrough in prostate cancer immunotherapy.

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.

Immune Modulation by Androgen Deprivation and Radiation Therapy: Implications for Prostate Cancer Immunotherapy

Prostate cancer patients often receive androgen deprivation therapy (ADT) in combination with radiation therapy (RT). Recent evidence suggests that both ADT and RT have immune modulatory properties. First, ADT can cause infiltration of lymphocytes into the prostate, although it remains unclear whether the influx of lymphocytes is beneficial, particularly with the advent of new classes of androgen blockers. Second, in rare cases, radiation can elicit immune responses that mediate regression of metastatic lesions lying outside the field of radiation, a phenomenon known as the abscopal response. In light of these findings, there is emerging interest in exploiting any potential synergy between ADT, RT, and immunotherapy. Here, we provide a comprehensive review of the rationale behind combining immunotherapy with ADT and RT for the treatment of prostate cancer, including an examination of the current clinical trials that employ this combination. The reported outcomes of several trials demonstrate the promise of this combination strategy; however, further scrutiny is needed to elucidate how these standard therapies interact with immune modulators. In addition, we discuss the importance of synchronizing immune modulation relative to ADT and RT, and provide insight into elements that may impact the ability to achieve maximum synergy between these treatments.

Interleukin-17 promotes development of castration-resistant prostate cancer potentially through creating an immunotolerant and pro-angiogenic tumor microenvironment

BACKGROUND

Interleukin-17 (IL-17) has been demonstrated to promote formation and growth of hormone-naïve prostate adenocarcinoma in mice. IL-17's role in development of castration-resistant prostate cancer is unknown. In the present study, we investigated IL-17's role in castration-resistant prostate cancer in a mouse model.

METHODS

IL-17 receptor C (IL-17RC) deficient mice were interbred with Pten conditional mutant mice to produce RC(+) mice that maintained IL-17RC expression and RC(-) mice that were IL-17RC deficient. Male RC(+) and RC(-) mice were Pten-null and were castrated at 16 weeks of age when invasive prostate cancer had already formed. At 30 weeks of age, all male mice were analyzed for the prostate phenotypes.

RESULTS

RC(-) mice displayed prostates that were smaller than RC(+) mice. Approximately 23% of prostatic glands in RC(-) mice, in contrast to 65% of prostatic glands in RC(+) mice, developed invasive adenocarcinomas. Compared to castrate RC(+) mice, castrate RC(-) mouse prostate had lower rates of cellular proliferation and higher rates of apoptosis as well as lower levels of MMP7, YBX1, MTA1, and UBE2C proteins. In addition, castrate RC(-) mouse prostate had less angiogenesis, which was associated with decreased levels of COX-2 and VEGF. Moreover, castrate RC(-) mouse prostate had fewer inflammatory cells including lymphocytes, myeloid-derived suppressor cells, and macrophages.

CONCLUSIONS

Taken together, our findings suggest that IL-17 promotes development of invasive prostate adenocarcinomas under castrate conditions, potentially through creating an immunotolerant and pro-angiogenic tumor microenvironment.

A randomized phase II trial evaluating different schedules of zoledronic acid on bone mineral density in patients with prostate cancer beginning androgen deprivation therapy

OBJECTIVE

To assess the effects of timing and schedule of zoledronic acid (ZA) administration on bone mineral density (BMD) in patients beginning androgen deprivation therapy (ADT) for the treatment of recurrent prostate cancer.

PATIENTS AND METHODS

In this randomized, 3-arm trial, we evaluated changes in BMD after 3 different ZA administration schedules in men with recurrent prostate cancer who were beginning ADT. Forty-four patients were enrolled and randomized to receive a single dose of ZA given 1 week before beginning ADT (arm 1), a single dose of ZA given 6 months after beginning ADT (arm 2), or monthly administration of ZA starting 6 months after beginning ADT, for a total of 6 doses (arm 3).

RESULTS

Patients who received ZA before ADT had a significant improvement in BMD at the total proximal femur and trochanter after 6 months compared with the other groups. In addition, only patients in the arm that received multiple doses improved lumbar spine BMD while on ADT, with these findings persisting to 24 months. However, this group also experienced more grade 1 adverse events.

CONCLUSIONS

Analysis of these data suggests that ZA administration before initiation of ADT was superior to treatment 6 months after starting ADT in maintaining BMD. In addition, monthly ZA administration can increase BMD above baseline but is associated with more adverse events. Further study is needed to examine whether the timing and frequency of ZA therapy in patients on ADT can reduce fracture risk.

Combining T-cell immunotherapy and anti-androgen therapy for prostate cancer

BACKGROUND

Prostate cancer remains a significant health problem for men in the Western world. Although treatment modalities are available, these do not confer long-term benefit and are accompanied by substantial side effects. Adoptive immunotherapy represents an attractive alternative to conventional treatments as a means to control tumor growth.

METHODS

To selectively target the tumor-expressed form of Muc1 we constructed a retroviral vector encoding a chimeric antigen receptor (CAR) directed against the aberrantly-expressed extracellular portion of Muc1 called the 'variable number of tandem repeats'.

RESULTS

We now demonstrate that T cells can be genetically engineered to express a CAR targeting the tumor-associated antigen Muc1. CAR-Muc1 T cells were able to selectively kill Muc1-expressing human prostate cancer cells. However, we noted that heterogeneous expression of the Muc1 antigen on tumor cells facilitated immune escape and the outgrowth of target-antigen loss variants of the tumor. Given the importance of androgen ablation therapy in the management of metastatic prostate cancer, we therefore also tested the value of combining conventional (anti-androgen) and experimental (CAR-Muc1 T cells) approaches. We show that CAR-Muc1 T cells were not adversely impacted by anti-androgen therapy and subsequently demonstrate the feasibility of combining the approaches to produce additive anti-tumor effects in vitro.

CONCLUSIONS

Adoptive transfer of CAR-Muc1 T cells alone or in combination with other luteinizing hormone-releasing hormone analogs or antagonists should be tested in human clinical trials.