Immune response to sipuleucel-T in prostate cancer

Bone Health Management in the Continuum of Prostate Cancer Disease

Prostate cancer (PCa) is the second-leading cause of cancer-related deaths in men. PCa cells require androgen receptor (AR) signaling for their growth and survival. Androgen deprivation therapy (ADT) is the preferred treatment for patients with locally advanced and metastatic PCa disease. Despite their initial response to androgen blockade, most patients eventually will develop metastatic castration-resistant prostate cancer (mCRPC). Bone metastases are common in men with mCRPC, occurring in 30% of patients within 2 years of castration resistance and in >90% of patients over the course of the disease. Patients with mCRPC-induced bone metastasis develop lesions throughout their skeleton; the 5-year survival rate for these patients is 47%. Bone-metastasis-induced early changes in the bone that proceed the osteoblastic response in the bone matrix are monitored and detected via modern magnetic resonance and PET/CT imaging technologies. Various treatment options, such as targeting osteolytic metastasis with bisphosphonates, prednisone, dexamethasone, denosumab, immunotherapy, external beam radiation therapy, radiopharmaceuticals, surgery, and pain medications are employed to treat prostate-cancer-induced bone metastasis and manage bone health. However, these diagnostics and treatment options are not very accurate nor efficient enough to treat bone metastases and manage bone health. In this review, we present the pathogenesis of PCa-induced bone metastasis, its deleterious impacts on vital organs, the impact of metastatic PCa on bone health, treatment interventions for bone metastasis and management of bone- and skeletal-related events, and possible current and future therapeutic options for bone management in the continuum of prostate cancer disease.

A Model-Based Framework to Identify Optimal Administration Protocols for Immunotherapies in Castration-Resistance Prostate Cancer

Prostate cancer (PCa) is one of the most frequent cancer in male population. Androgen deprivation therapy is the first-line strategy for the metastatic stage of the disease, but, inevitably, PCa develops resistance to castration (CRPC), becoming incurable. In recent years, clinical trials are testing the efficacy of anti-CTLA4 on CRPC. However, this tumor seems to be resistant to immunotherapies that are very effective in other types of cancers, and, so far, only the dendritic cell vaccine sipuleucel-T has been approved. In this work, we employ a mathematical model of CRPC to determine the optimal administration protocol of ipilimumab, a particular anti-CTLA4, as single treatment or in combination with the sipuleucel-T, by considering both the effect on tumor population and the drug toxicity. To this end, we first introduce a dose-depending function of toxicity, estimated from experimental data, then we define two different optimization problems. We show the results obtained by imposing different constraints, and how these change by varying drug efficacy. Our results suggest administration of high-doses for a brief period, which is predicted to be more efficient than solutions with prolonged low-doses. The model also highlights a synergy between ipilimumab and sipuleucel-T, which leads to a better tumor control with lower doses of ipilimumab. Finally, tumor eradication is also conceivable, but it depends on patient-specific parameters.

Design of Outer Membrane Vesicles as Cancer Vaccines: A New Toolkit for Cancer Therapy

Cancer vaccines have been extensively studied in recent years and have contributed to exceptional achievements in cancer treatment. They are some of the most newly developed vaccines, although only two are currently approved for use, Provenge and Talimogene laherparepvec (T-VEC). Despite the approval of these two vaccines, most vaccines have been terminated at the clinical trial stage, which indicates that although they are effective in theory, concerns still exist, including low antigenicity of targeting antigens and tumor heterogeneity. In recent years, with new understanding of the biological function and vaccine potential of outer membrane vesicles (OMVs), their potential application in cancer vaccine design deserves our attention. Therefore, this review focuses on the mechanisms, advantages, and prospects of OMVs as antigen-carrier vaccines in cancer vaccine development. We believe that OMV-based vaccines present a safe and effective cancer therapeutic option with broad application prospects.

Dihydrotestosterone Increases Cytotoxic Activity of Macrophages on Prostate Cancer Cells via TRAIL

Although androgen deprivation therapy (ADT) and immunotherapy are potential treatment options in men with metastatic prostate cancer (CaP), androgen has conventionally been proposed to be a suppressor of the immune response. However, we herein report that DHT activates macrophages. When the murine macrophage cell line (RAW 264.7), human monocyte cell line (THP-1), and human peripheral blood monocytes were cultured with androgen-resistant CaP cell lines, DHT increased cytotoxicity of macrophages in a concentration-dependent manner. Further studies revealed that DHT induced M1 polarization and increased the expression levels of TNF-related apoptosis-inducing ligand (TRAIL) in macrophages and that this effect was abrogated when TRAIL was neutralized with a blocking antibody or small interfering RNA. Subsequent experiments demonstrated that induction of TRAIL expression was regulated by direct binding of androgen receptor to the TRAIL promoter region. Finally, an in vivo mouse study demonstrated that castration enhanced the growth of an androgen-resistant murine CaP tumor and that this protumorigenic effect of castration was blocked when macrophages were removed with clodronate liposomes. Collectively, these results demonstrate that DHT activates the cytotoxic activity of macrophages and suggest that immunotherapy may not be optimal when combined with ADT in CaP.

Prostate cancer health disparities: An immuno-biological perspective

Prostate cancer (PCa) is the most commonly diagnosed malignancy in males, and, in the United States, is the second leading cause of cancer-related death for men older than 40 years. There is a higher incidence of PCa for African Americans (AAs) than for European-Americans (EAs). Investigations related to the incidence of PCa-related health disparities for AAs suggest that there are differences in the genetic makeup of these populations. Other differences are environmentally induced (e.g., diet and lifestyle), and the exposures are different. Men who immigrate from Eastern to Western countries have a higher risk of PCa than men in their native countries. However, the number of immigrants developing PCa is still lower than that of men in Western countries, suggesting that genetic factors are involved in the development of PCa. Altered genetic polymorphisms are associated with PCa progression. Androgens and the androgen receptor (AR) are involved in the development and progression of PCa. For populations with diverse racial/ethnic backgrounds, differences in lifestyle, diet, and biology, including genetic mutations/polymorphisms and levels of androgens and AR, are risk factors for PCa. Here, we provide an immuno-biological perspective on PCa in relation to racial/ethnic disparities and identify factors associated with the disproportionate incidence of PCa and its clinical outcomes.

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of prostate carcinoma

Prostate cancer is the most commonly diagnosed malignancy and second leading cause of cancer death among men in the United States. In recent years, several new agents, including cancer immunotherapies, have been approved or are currently being investigated in late-stage clinical trials for the management of advanced prostate cancer. Therefore, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel, including physicians, nurses, and patient advocates, to develop consensus recommendations for the clinical application of immunotherapy for prostate cancer patients. To do so, a systematic literature search was performed to identify high-impact papers from 2006 until 2014 and was further supplemented with literature provided by the panel. Results from the consensus panel voting and discussion as well as the literature review were used to rate supporting evidence and generate recommendations for the use of immunotherapy in prostate cancer patients. Sipuleucel-T, an autologous dendritic cell vaccine, is the first and currently only immunotherapeutic agent approved for the clinical management of metastatic castrate resistant prostate cancer (mCRPC). The consensus panel utilized this model to discuss immunotherapy in the treatment of prostate cancer, issues related to patient selection, monitoring of patients during and post treatment, and sequence/combination with other anti-cancer treatments. Potential immunotherapies emerging from late-stage clinical trials are also discussed. As immunotherapy evolves as a therapeutic option for the treatment of prostate cancer, these recommendations will be updated accordingly.

Primer on immuno-oncology and immune response

Advances in the understanding of the immunogenicity of tumors have provided the basis for immuno-oncology, the development of immunotherapeutic agents that augment the patient's antitumor immunity and disrupt the immune-regulatory circuits that allow tumors to evade the immune system. Two immunomodulatory agents recently have been introduced for the treatment of malignancy: sipuleucel-T and ipilimumab. Unlike cytotoxic chemotherapy, immunotherapies stimulate the patient's immune system to mount or augment existing endogenous antitumor immune responses. Both agents have demonstrated significant improvements in long-term overall survival in patients. Like other immunotherapies, sipuleucel-T and ipilimumab also are characterized by adverse events that manifest as immune-related inflammatory conditions that typically are low grade. Management guidelines have been developed and emphasize early recognition of the signs and symptoms of immune-related adverse events and treatment with corticosteroids. Because these events can manifest even after the cessation of therapy, patients treated with immunotherapies should continue to be followed by their oncology team and other healthcare providers.

Anti-CD27 Antibody Potentiates Antitumor Effect of Dendritic Cell-Based Vaccine in Prostate Cancer-Bearing Mice

In the current study, we investigated whether anti-CD27 monoclonal antibody can enhance the antitumor efficacy of a dendritic cell-based vaccine in prostate cancer-bearing mice. The overall therapeutic effect of a dendritic cell-based vaccine for prostate cancer remains moderate. A prostate cancer model was established by subcutaneous injection of RM-1 tumor cells into male C57BL/6 mice on day 0. After 4 days, tumor-bearing mice were treated with RM-1 tumor lysate-pulsed dendritic cells (i.e., dendritic cell-based vaccine), anti-CD27 monoclonal antibody, or a combination of RM-1 tumor lysate-pulsed dendritic cells with anti-CD27 monoclonal antibody. Mice were killed at 21 days after tumor cell implantation. Tumor size was measured for assessment of antitumor effect. Spleens were collected for analysis of antitumor immune responses. The antitumor immune responses were evaluated by measuring the proliferation and activity of T cells, which have the ability to kill tumor cells. The combination therapy with RM-1 tumor lysate-pulsed dendritic cells and anti-CD27 antibody significantly enhanced T-cell proliferation and activity, and significantly reduced tumor growth, compared with monotherapy with RM-1 tumor lysate-pulsed dendritic cells or anti-CD27 antibody. Our results suggest that combined treatment can strengthen antitumor efficacy by improving T-cell proliferation and activity.