A "scoping" review of prostate brachytherapy and immune responses.

PURPOSE: Whether prostate brachytherapy (BT) results in opportunistic biological changes that can improve clinical outcomes is not well studied. We sought to investigate the impact of prostate BT on the immune system. MATERIALS AND METHODS: A scoping review was performed using PubMed/Scopus for papers published between 2011-2021. Search terms were "brachytherapy" AND "immune" AND "prostate". A total of 81 records were identified and 6 were selected for further review. RESULTS: 2 low-dose-rate BT papers (n=68) evaluated changes in the peripheral blood following I-125 monotherapy. Both showed significant increases in peripheral CD3+ and CD4+ T cells post-BT. One also demonstrated significant increases in Treg subsets up to 150 days post-BT. 4 high-dose-rate (HDR) studies (n=37) were identified, and all were done in combination with EBRT. The largest study (n=24) showed a single 10 Gy fraction of HDR converted 80% of "cold" tumors into an "intermediate" or "hot" state, based on a tumor inflammation signature when comparing a pre-BT biopsy to one prior to a second HDR fraction. CONCLUSION: Prostate BT can invoke an immune activating phenotype; however, changes in immunosuppressive cells are also seen. Additional data is needed to understand how to promote synergy between BT and the immune system.

A Perspective on Withania somnifera Modulating Antitumor Immunity in Targeting Prostate Cancer.

Medicinal plants serve as a lead source of bioactive compounds and have been an integral part of day-to-day life in treating various disease conditions since ancient times. Withaferin A (WFA), a bioactive ingredient of Withania somnifera, has been used for health and medicinal purposes for its adaptogenic, anti-inflammatory, and anticancer properties long before the published literature came into existence. Nearly 25% of pharmaceutical drugs are derived from medicinal plants, classified as dietary supplements. The bioactive compounds in these supplements may serve as chemotherapeutic substances competent to inhibit or reverse the process of carcinogenesis. The role of WFA is appreciated to polarize tumor-suppressive Th1-type immune response inducing natural killer cell activity and may provide an opportunity to manipulate the tumor microenvironment at an early stage to inhibit tumor progression. This article signifies the cumulative information about the role of WFA in modulating antitumor immunity and its potential in targeting prostate cancer.

Using ex vivo culture to assess dynamic phenotype changes in human prostate macrophages following exposure to therapeutic drugs.

Within the prostate tumor microenvironment (TME) there are complex multi-faceted and dynamic communication occurring between cancer cells and immune cells. Macrophages are key cells which infiltrate and surround tumor cells and are recognized to significantly contribute to tumor resistance and metastases. Our understanding of their function in the TME is commonly based on in vitro and in vivo models, with limited research to confirm these model observations in human prostates. Macrophage infiltration was evaluated within the TME of human prostates after 72 h culture of fresh biopsies samples in the presence of control or enzalutamide. In addition to immunohistochemistry, an optimized protocol for multi-parametric evaluation of cellular surface markers was developed using flow cytometry. Flow cytometry parameters were compared to clinicopathological features. Immunohistochemistry staining for 19 patients with paired samples suggested enzalutamide increased the expression of CD163 relative to CD68 staining. Techniques to validate these results using flow cytometry of dissociated biopsies after 72 h of culture are described. In a second cohort of patients with Gleason grade group ≥ 3 prostate cancer, global macrophage expression of CD163 was unchanged with enzalutamide treatment. However, exploratory analyses of our results using multi-parametric flow cytometry for multiple immunosuppressive macrophage markers suggest subgroup changes as well as novel associations between circulating biomarkers like the neutrophil to lymphocyte ratio (NLR) and immune cell phenotype composition in the prostate TME. Further, we observed an association between B7-H3 expressing tumor-associated macrophages and the presence of intraductal carcinoma. The use of flow cytometry to evaluate ex vivo cultured prostate biopsies fills an important gap in our ability to understand the immune cell composition of the prostate TME. Our results highlight novel associations for further investigation.

Quo Vadis Advanced Prostate Cancer Therapy? Novel Treatment Perspectives and Possible Future Directions.

Prostate cancer is a very common disease, which is, unfortunately, often the cause of many male deaths. This is underlined by the fact that the early stages of prostate cancer are often asymptomatic. Therefore, the disease is usually detected and diagnosed at late advanced or even metastasized stages, which are already difficult to treat. Hence, it is important to pursue research and development not only in terms of novel diagnostic methods but also of therapeutic ones, as well as to increase the effectiveness of the treatment by combinational medicinal approach. Therefore, in this review article, we focus on recent approaches and novel potential tools for the treatment of advanced prostate cancer; these include not only androgen deprivation therapy, antiandrogen therapy, photodynamic therapy, photothermal therapy, immunotherapy, multimodal therapy, but also poly(ADP-ribose) polymerase, Akt and cyclin-dependent kinase inhibitors.

2D exfoliated black phosphorus influences healthy and cancer prostate cell behaviors.

Nowadays, prostate cancer is the most widespread tumour in worldwide male population. Actually, brachytherapy is the most advanced radiotherapy strategy for the local treatment of prostate cancer. It consists in the placing of radioactive sources closed to the tumour side thus killing cancer cells. However, brachytherapy causes the same adverse effects of external-beam radiotherapy. Therefore, alternative treatment approaches are required for enhancing radiotherapy effectiveness and reducing toxic symptoms. Nanostructured exfoliated black phosphorus (2D BP) may represent a strategic tool for local cancer therapy because of its capability to induce singlet oxygen production and act as photosensitizer. Hence, we investigated 2D BP in vitro effect on healthy and cancer prostate cell behavior. 2D BP was obtained through liquid exfoliation. 2D BP effect on healthy and cancer prostate cell behaviors was analyzed by investigating cell viability, oxidative stress and inflammatory marker expression. 2D BP inhibited prostate cancer cell survival, meanwhile promoted healthy prostate cell survival in vitro by modulating oxidative stress and immune response with and without near-infrared light (NIR)-irradiation. Nanostructured 2D BP is able to inhibit in vitro prostate cancer cells survival and preserve healthy prostate cell vitality through the control of oxidative stress and immune response, respectively.

High intratumoral CD8+ T-cell infiltration is associated with improved survival in prostate cancer patients undergoing radical prostatectomy.

BACKGROUND: A high density of CD8+ tumor infiltrating lymphocytes (TILs) is associated with improved survival in multiple cancers, but its prognostic role in prostate cancer remains controversial. The aim of our study was to evaluate the prognostic value of CD8+ TILs in prostate cancer patients undergoing radical prostatectomy (RP). We hypothesized that elevated density of CD8+ TILs in the RP specimen would correlate with improved clinical outcomes. This information may be helpful for future immunotherapy clinical trial design and treatment selection. METHODS: Tumor microarrays constructed from 230 patients with localized prostate cancers who underwent RP from 2006 to 2012 at Roswell Park Comprehensive Cancer Center were analyzed retrospectively using immunohistochemistry. CD8+ cell density was evaluated using a computerized scoring system. The cohorts were separated by CD8+ TIL density at the 25th percentile (i.e., low 7 or pT3/4). The median follow-up time was 8.4 years. High CD8+ TIL density was associated with improved 5-year overall survival (98% vs. 91%, p = .01) and prostate cancer-specific survival (99% vs. 95%, p = .04) compared with patients with low CD8+ TIL density. There was a trend toward higher 5-year biochemical recurrence-free survival and metastasis-free survival in the cohort of patients with high CD8+ TIL density (52% vs. 38% and 86% vs. 73%, respectively), although the difference did not reach statistical significance (p = .18 and p = .05, respectively). In a multivariate analysis high CD8+ TIL density was an independent favorable prognostic factor for overall survival (hazards ratio = 0.38; 95% confidence interval: 0.17-0.87; p = .02). In contrast to the prognostic value of CD8+ TIL density, the CD8+ cell density in the matched normal prostate tissue was not associated with any clinical outcomes. CONCLUSION: Intratumoral CD8+ T-cell infiltration in the RP specimen is independently associated with improved survival after RP in this high-risk prostate cancer cohort. Pre-RP immunomodulation that promotes intratumoral CD8+ cytotoxic T-cell infiltration may be beneficial for this population.

Harnessing Natural Killer Cell Function for Genitourinary Cancers.

Natural killer (NK) cells are potently cytolytic innate lymphocytes involved in the immune surveillance of tumors and virally infected cells. Although much progress has been made in manipulating the ability of T cells to recognize and eliminate tumors, a comprehensive understanding of NK-cell infiltration into solid tumors, and their amenability to immunomodulation, remains incomplete. This article discusses recent studies showing that urologic tumors are infiltrated by NK cells and that these NK cells are often dysfunctional, but that strategies interfering with inhibitory axes have significant potential to alleviate this dysfunction.

Preclinical Efficacy of a PSMA-Targeted Thorium-227 Conjugate (PSMA-TTC), a Targeted Alpha Therapy for Prostate Cancer.

PURPOSE: Prostate-specific membrane antigen (PSMA) is an attractive target for radionuclide therapy of metastatic castration-resistant prostate cancer (mCRPC). PSMA-targeted alpha therapy (TAT) has shown early signs of activity in patients with prostate cancer refractory to beta radiation. We describe a novel, antibody-based TAT, the PSMA-targeted thorium-227 conjugate PSMA-TTC (BAY 2315497) consisting of the alpha-particle emitter thorium-227 complexed by a 3,2-HOPO chelator covalently linked to a fully human PSMA-targeting antibody. EXPERIMENTAL DESIGN: PSMA-TTC was characterized for affinity, mode of action, and cytotoxic activity in vitro. Biodistribution, pharmacokinetics, and antitumor efficacy were investigated in vivo using cell line and patient-derived xenograft (PDX) models of prostate cancer. RESULTS: PSMA-TTC was selectively internalized into PSMA-positive cells and potently induced DNA damage, cell-cycle arrest, and apoptosis in vitro. Decrease in cell viability was observed dependent on the cellular PSMA expression levels. In vivo, PSMA-TTC showed strong antitumor efficacy with T/C values of 0.01 to 0.31 after a single injection at 300 to 500 kBq/kg in subcutaneous cell line and PDX models, including models resistant to standard-of-care drugs such as enzalutamide. Furthermore, inhibition of both cancer and cancer-induced abnormal bone growth was observed in a model mimicking prostate cancer metastasized to bone. Specific tumor uptake and efficacy were demonstrated using various PSMA-TTC doses and dosing schedules. Induction of DNA double-strand breaks was identified as a key mode of action for PSMA-TTC both in vitro and in vivo. CONCLUSIONS: The strong preclinical antitumor activity of PSMA-TTC supports its clinical evaluation, and a phase I trial is ongoing in mCRPC patients (NCT03724747).

Selenium-containing ruthenium complex synergizes with natural killer cells to enhance immunotherapy against prostate cancer via activating TRAIL/FasL signaling.

Natural killer (NK) cells-based therapy has been used widely for cancer treatment in clinic trails. However, the immunotherapeutic efficacy of this method has been greatly hindered by tumor evasion and diminished activities of NK cells. In the present study, a selenium (Se)-bearing ruthenium (Ru) complex (RuSe) was designed that could synergistically potentiate NK cell-mediated killing against prostate cancer cells. As expected, pretreatment of cancer cells with subtoxic doses of RuSe effectively augmented the lysis potency of NK cells, with up to 2.46-fold enhancement than NK cells alone, against PC3 cells. More importantly, low concentrations of RuSe could augment the tumor destroying potency of NK cells derived from 10 clinical patients, with the enhancement range from 0.78- to 11.9-fold against PC3 cells and 0.67- to 3.8-fold against LNCAP cells. Mechanistic studies revealed that the sensitizing effect of RuSe primarily depended on TRAIL/TRAIL-R and Fas/FasL-mediated signaling. Furthermore, the increased expression level of these ligands highly relied on ROS overproduction-triggered DNA damage and the downstream ATM and ATR pathways. Furthermore, RuSe potently activated and synergized with NK cells to restrain tumor growth in vivo without causing toxic side effects on major organs. Taken together, the current study not only provides a strategy for application of metal complexes in chemo-immunotherapy but also sheds light on the potential roles and mechanisms of action on such Se-containing drugs as efficient immune-sensitizing agents for NK cell-based immunotherapy.

Supplemental estrogen and caloric restriction reduce obesity-induced periprostatic white adipose inflammation in mice.

Obesity is associated with an increased incidence of high-grade prostate cancer (PC) and worse prognosis for PC patients. Recently, we showed in men that obesity-related periprostatic white adipose tissue (WAT) inflammation, characterized by macrophages surrounding dead or dying adipocytes forming crown-like structures, was associated with high-grade PC. Possibly, interventions that suppress periprostatic WAT inflammation will improve outcomes for men with PC. Here, we tested the hypothesis that supplemental 17ß-estradiol (E2) could decrease periprostatic WAT inflammation in obese male mice. Mice were fed a high-fat diet to induce periprostatic WAT inflammation before being treated with supplemental E2. E2 supplementation suppressed caloric intake, induced weight loss, decreased periprostatic WAT inflammation and downregulated the expression of genes linked to inflammation including Cd68, Mcp1 and Tnf. Similar to the effects of E2 supplementation, treatment with diethylstilbestrol, a synthetic estrogen, also suppressed caloric intake and reduced periprostatic WAT inflammation. To determine whether the observed effects of supplemental estrogen could be reproduced by caloric restriction (CR) alone, obese mice were put on a 30% CR diet. Like estrogen treatment, CR was effective in reducing body weight, periprostatic WAT inflammation and the expression of pro-inflammatory genes. Transcriptomic analyses of periprostatic fat showed that obesity was associated with enrichment in inflammatory response pathways, which were normalized by both supplemental E2 and CR. Taken together, these findings strengthen the rationale for future efforts to determine whether either CR or supplemental estrogen will decrease periprostatic WAT inflammation and thereby improve outcomes for men with PC.

Omega-3 fatty acids decrease prostate cancer progression associated with an anti-tumor immune response in eugonadal and castrated mice.

BACKGROUND: Several lines of evidence suggest effects of dietary fat on prostate cancer (PCa) development and progression. Targeting omega (ω)-3:ω6 fatty acids (FA) ratio could be beneficial against PCa by favorably modulating inflammation. Here, we studied the effects of ω3- and ω6-enriched diets on prostate tumor growth and inflammatory response in androgen-deprived and non-deprived conditions. METHODS: Immune-competent eugonadal and castrated C57BL/6 mice were injected with TRAMP-C2 prostate tumor cells and daily fed with ω3- or ω6-enriched diet. FA and cytokine profiles were measured in blood and tumors using gas chromatography and multiplex immunoassay, respectively. Immune cell infiltration in tumors was profiled by multicolor flow cytometry. RESULTS: ω3-enriched diet decreased prostate TRAMP-C2 tumor growth in immune-competent eugonadal and castrated mice. Cytokines associated with Th1 immune response (IL-12 [p70], IFN-γ, GM-CSF) and eosinophil recruitment (eotaxin-1, IL-5, and IL-13) were significantly elevated in tumors of ω3-fed mice. Using in vitro experiments, we confirmed ω3 FA-induced eotaxin-1 secretion by tumor cells and that eotaxin-1 secretion was regulated by androgens. Analysis of immune cell infiltrating tumors showed no major difference of immune cells' abundance between ω3- and ω6-enriched diets. CONCLUSIONS: ω3-enriched diet reduces prostate tumor growth independently of androgen levels. ω3 FA can inhibit tumor cell growth and induce a local anti-tumor inflammatory response. These findings warrant further examination of dietary ω3's potential to slow down the progression of androgen-sensitive and castrate-resistant PCa by modulating immune cell function in tumors.

M2 macrophages and regulatory T cells in lethal prostate cancer.

BACKGROUND: Prostate cancer (PCa) is one of the most frequently diagnosed cancers in the world. Emerging evidence suggests that inflammatory cells such as M2 macrophages and regulatory T cells (Tregs ) can contribute to cancer progression by suppressing the anti-tumor immune response. This study investigated the number of CD163-positive M2 macrophages in PCa tissue. It also investigated the correlation and interaction of M2 macrophages and Tregs . METHODS: This nested case-control study included subjects from a cohort of men diagnosed with PCa as an incidental finding during transurethral resection of the prostate. The cases were 225 men who died from PCa, and the controls were 367 men who survived more than 10 years after PCa diagnosis without disease progression. Infiltrating CD163-positive M2 macrophages and FOXP3/CD4-positive Tregs in PCa tissue were identified using immunohistochemistry. The correlation and interaction of M2 macrophages and Tregs were assessed using Spearman's rank-order correlation and a likelihood test, respectively. Logistic regression was used to estimate odds ratios (ORs) for lethal PCa and macrophage counts. RESULTS: The number of M2 macrophages and Tregs showed a significant correlation (P < 0.001) but no interactions. The OR for lethal PCa was 1.93 (95%CI: 1.23-3.03) for men with high numbers of M2 macrophages. Also for cases with uncertain outcome (GS categories 3 + 4 and 4 + 3) high numbers of M2 macrophages does predict a poorer prognosis. CONCLUSIONS: Our data showed that men with high numbers of M2 macrophages in the prostate tumor environment had increased odds of dying of PCa. It is possible that M2 macrophages, together with other suppressor cells such as Tregs , promote an immunosuppressive environment.

[Effects of curcumin on tumor growth and immune function in prostate cancer-bearing mice].

OBJECTIVE: To explore the effects of curcumin (CCM) on tumor growth and immune function in mice bearing RM-1 prostate cancer cells. METHODS: A prostate cancer model was established in 50 C57BL/6 mice by subcutaneous inoculation of RM-1 cells. The model mice were randomly assigned to intraperitoneal injection of 10% dimethyl sulfoxide at 0.2 ml (the model control group), cyclophosphamide at 20 mg/kg (the CTX group), or CCM at 50 mg/kg (the low-dose CCM group), 100 mg/kg (the medium-dose CCM group) or 200 mg/kg (the high-dose CCM group), respectively, all once a day for 14 successive days, followed by measurement of the tumor weight, calculation of the tumor-inhibition rate, and detection of immunological indicators. RESULTS: The tumor weight was significantly decreased in the CTX (ï¼»1.32 ± 0.06ï¼½ g), low-dose CCM (ï¼»1.1.54 ± 0.08ï¼½ g), medium-dose CCM (ï¼»1.48 ± 0.08ï¼½ g), and high-dose CCM groups (ï¼»1.42 ± 0.07ï¼½ g) as compared with that in the model control group (ï¼»2.09 ± 0.10ï¼½ g) (P < 0.05 or P < 0.01), with no statistically significant differences among the former four groups (P > 0.05). The tumor-inhibition rates in the CTX and low-, medium- and high-dose CCM groups were 36.84%, 27.27%, 29.18% and 32.06%, respectively. All the immunological indicators except the CD4+/CD8+ ratio were remarkably reduced in the CTX group as compared with those in the model control (P < 0.01), but increased in the CCM groups in comparison with those in the CTX group (P < 0.01). CONCLUSIONS: Curcumin has an anti-tumor effect and enhances immune function in prostate cancer-bearing mice.

Antitumor Activity of MEDI3726 (ADCT-401), a Pyrrolobenzodiazepine Antibody-Drug Conjugate Targeting PSMA, in Preclinical Models of Prostate Cancer.

Prostate-specific membrane antigen (PSMA) is a membrane-bound glutamate carboxypeptidase that is highly expressed in nearly all prostate cancers with the highest expression in metastatic castration-resistant prostate cancer (mCRPC). The prevalence of increased surface expression and constitutive internalization of PSMA make it an attractive target for an antibody-drug conjugate (ADC) approach to treating patients with mCRPC. MEDI3726 (previously known as ADCT-401) is an ADC consisting of an engineered version of the anti-PSMA antibody J591 site specifically conjugated to the pyrrolobenzodiazepine (PBD) dimer tesirine. MEDI3726 specifically binds the extracellular domain of PSMA and, once internalized, releases the PBD dimer to crosslink DNA and trigger cell death. In vitro, MEDI3726 demonstrated potent and specific cytotoxicity in a panel of PSMA-positive prostate cancer cell lines, consistent with internalization and DNA interstrand crosslinking. In vivo, MEDI3726 showed robust antitumor activity against the LNCaP and the castration-resistant CWR22Rv1 prostate cancer cell line xenografts. MEDI3726 also demonstrated durable antitumor activity in the PSMA-positive human prostate cancer patient-derived xenograft (PDX) LuCaP models. This activity correlated with increased phosphorylated Histone H2AX in tumor xenografts treated with MEDI3726. MEDI3726 is being evaluated in a phase I clinical trial as a treatment for patients with metastatic castrate-resistant prostate cancer (NCT02991911). Mol Cancer Ther; 17(10); 2176-86. ©2018 AACR.

Hyperthermic treatment at 56 °C induces tumour-specific immune protection in a mouse model of prostate cancer in both prophylactic and therapeutic immunization regimens.

Most active cancer immunotherapies able to induce a long-lasting protection against tumours are based on the activation of tumour-specific cytotoxic T lymphocytes (CTLs). Cell death by hyperthermia induces apoptosis followed by secondary necrosis, with the production of factors named "danger associated molecular pattern" (DAMP) molecules (DAMPs), that activate dendritic cells (DCs) to perform antigen uptake, processing and presentation, followed by CTLs cross priming. In many published studies, hyperthermia treatment of tumour cells is performed at 42-45 °C; these temperatures mainly promote cell surface expression of DAMPs. Treatment at 56 °C of tumour cells was shown to induce DAMPs secretion rather than their cell surface expression, improving DC activation and CTL cross priming in vitro. Thus we tested the relevance of this finding in vivo on the generation of a tumour-specific memory immune response, in the TRAMP-C2 mouse prostate carcinoma transplantable model. TRAMP-C2 tumour cells treated at 56 °C were able not only to activate DCs in vitro but also to trigger a tumour-specific CTL-dependent immune response in vivo. Prophylactic vaccination with 56 °C-treated TRAMP-C2 tumour cells alone provided protection against TRAMP-C2 tumour growth in vivo, whilst in the therapeutic regimen, control of tumour growth was achieved combining immunization with adjuvant chemotherapy.

Surface engineering tumor cells with adjuvant-loaded particles for use as cancer vaccines.

Cell surface engineering is an expanding field and whilst extensive research has been performed decorating cell surfaces with biomolecules, the engineering of cell surfaces with particles has been a largely unexploited area. This study reports on the assembly of cell-particle hybrids where irradiated tumor cells were surface engineered with adjuvant-loaded, biodegradable, biocompatible, polymeric particles, with the aim of generating a construct capable of functioning as a therapeutic cancer vaccine. Successfully assembled cell-particle hybrids presented here comprised either melanoma cells or prostate cancer cells stably adorned with Toll-like receptor-9 ligand-loaded particles using streptavidin-biotin cross-linking. Both cell-particle assemblies were tested in vivo for their potential as therapeutic cancer vaccines yielding promising therapeutic results for the prostate cancer model. The ramifications of results obtained for both tumor models are openly discussed.

CPA-7 influences immune profile and elicits anti-prostate cancer effects by inhibiting activated STAT3.

BACKGROUND: Platinum-based chemotherapy is emerging as the first line of treatment for castration resistant prostate cancer. Among the family of platinum (IV)-based compounds, a member known as CPA-7 inhibits the growth of multiple cancer cell lines. However, how and to what extent CPA-7 elicits its anti-prostate cancer effects in vivo is largely unknown. METHODS: In this study, we firstly assessed the potential toxicity of the synthesized CPA-7 in a prostate cancer model as well as in normal mice. Next, we evaluated the in vitro effects of CPA-7 on the growth of prostate cancer cells using cell counting assay, and calculated the tumor sizes and cumulative survival rate of the tumor bearing mice by Kaplan-Meier method during CPA-7 treatment. Then we measured the expression level of the activated form of STAT3 (one targets of CPA-7) and its transcriptive activity post CPA-7 treatment by synergistically using western blot, IHC, and firefly luciferase reporter assays. Finally, effects of CPA-7 on immune cell trafficking in the tumor draining lymph nodes and in the spleens are evaluated with flow cytometry. RESULTS: Treatment with CPA-7 significantly inhibited growth of prostate cancer cells in vitro, and also in mice resulting in a prolonged survival and a decreased recurrence rate. These therapeutic effects are due, at least in part, to functional depletion of STAT3 in prostate tumor tissue as well as in the surrounding areas of tumor cell invasion. CPA-7 treatment also resulted in a reduced level of regulatory T cells and increased levels of cytotoxic T and T helper cells in the spleen and in tumor infiltrating lymph nodes. This favorable effect on immune cell trafficking may account for the amnestic immune response against recurrent prostate cancer. CONCLUSIONS: CPA-7 is a promising new therapeutic agent for prostate cancer that both inhibits tumor cell proliferation and stimulates anti-tumor immunity. It has potential as first line treatment and/or as an adjuvant for refractory prostate cancer.

Effect of radiochemical modification on biodistribution of scFvD2B antibody fragment recognising prostate specific membrane antigen.

Antibody-based reagents represent a promising strategy as clinical diagnostic tools. Prostate cancer (PCa) is the second-leading cause of death in males in the Western population. There is a presently unmet need for accurate diagnostic tool to localize and define the extent of both primary PCa and occult recurrent disease. One of the most suitable targets for PCa is the prostate-specific membrane antigen (PSMA) recognised by the monoclonal antibody D2B that we re-shaped into the single chain Fv (scFv format). Aim of this study was to evaluate in preclinical in vivo models the target specificity of scFvD2B after labelling with different radionuclides. (111)In radiolabelling was performed via the chelator Bz-NOTA, and (131)I radioiodination was performed using iodogen. The potential for molecular imaging and the biological behaviour of the radiolabelled scFvD2B were evaluated in mice bearing two subcutaneous PCa isogenic cell lines that differed only in PSMA expression. Biodistribution studies were performed at 3, 9, 15 and 24h after injection to determine the optimal imaging time point. A significant kidney accumulation, as percentage of injected dose of tissue (%ID/g), was observed for (111)In-scFvD2B at 3h after injection (45%ID/g) and it was maintained up to 24h (26%ID/g). By contrast, kidney accumulation of (131)I-scFvD2B was only marginally (0.3%ID/g at 24h). At the optimal time point defined between 15h and 24h, regardless of the radionuclide used, the scFvD2B was able to localize significantly better in the PSMA expressing tumours compared to the negative control; with (131)I-scFvD2B yielding a significantly better target/background ratio compared to (111)In-scFvD2B. These data suggest that, besides antigen specificity, chemical modification may affect antibody fragment biodistribution.

Immunotherapeutic approaches in prostate cancer: combinations and clinical integration.

Despite multiple immunologic approaches with peptide, protein, and DNA vaccines, no single therapy has induced complete remission or maintained durability of response in patients with castration-resistant prostate cancer (CRPC). Historically, immunotherapy has had limited effect on solid tumors with the exception of melanoma and renal cell carcinomas, which have been deemed as immunologic cancers given their potential for remissions either spontaneously or after removal of the primary lesion. There is considerable excitement about using an immunotherapy in combination with biologic agents such as checkpoint inhibitors, cytokines, other vaccines, or chemotherapy. Sipuleucel-T represents one of several novel immunologic therapeutic approaches to treat prostate cancer in addition to other solid tumors. It is the first in its class of autologous cellular therapies to demonstrate safety and an overall survival benefit in patients with asymptomatic or minimally symptomatic CRPC and represents a unique treatment method that may be further enhanced with other agents. Although sipuleucel-T can be used as a foundation on which to build and enhance future immunologic clinical trials, other exciting strategies are in development that may be easily integrated into the algorithm of current care.

Tasquinimod modulates suppressive myeloid cells and enhances cancer immunotherapies in murine models.

A major barrier for cancer immunotherapy is the presence of suppressive cell populations in patients with cancer, such as myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM), which contribute to the immunosuppressive microenvironment that promotes tumor growth and metastasis. Tasquinimod is a novel antitumor agent that is currently at an advanced stage of clinical development for treatment of castration-resistant prostate cancer. A target of tasquinimod is the inflammatory protein S100A9, which has been demonstrated to affect the accumulation and function of tumor-suppressive myeloid cells. Here, we report that tasquinimod provided a significant enhancement to the antitumor effects of two different immunotherapeutics in mouse models of cancer: a tumor vaccine (SurVaxM) for prostate cancer and a tumor-targeted superantigen (TTS) for melanoma. In the combination strategies, tasquinimod inhibited distinct MDSC populations and TAMs of the M2-polarized phenotype (CD206(+)). CD11b(+) myeloid cells isolated from tumors of treated mice expressed lower levels of arginase-1 and higher levels of inducible nitric oxide synthase (iNOS), and were less immunosuppressive ex vivo, which translated into a significantly reduced tumor-promoting capacity in vivo when these cells were coinjected with tumor cells. Tumor-specific CD8(+) T cells were increased markedly in the circulation and in tumors. Furthermore, T-cell effector functions, including cell-mediated cytotoxicity and IFNγ production, were potentiated. Taken together, these data suggest that pharmacologic targeting of suppressive myeloid cells by tasquinimod induces therapeutic benefit and provide the rationale for clinical testing of tasquinimod in combination with cancer immunotherapies.