Overcoming Oncogenic Mediated Tumor Immunity in Prostate Cancer

The Immunotherapy and Immunosuppressive Signaling in Therapy-Resistant Prostate Cancer

Prostate cancer is one of the most common malignant tumors in men. Initially, it is androgen-dependent, but it eventually develops into castration-resistant prostate cancer (CRPC), which is incurable with current androgen receptor signaling target therapy and chemotherapy. Immunotherapy, specifically with immune checkpoint inhibitors, has brought hope for the treatment of this type of prostate cancer. Approaches such as vaccines, adoptive chimeric antigen receptor-T (CAR-T) cells, and immune checkpoint inhibitors have been employed to activate innate and adaptive immune responses to treat prostate cancer, but with limited success. Only Sipuleucel-T and the immune checkpoint inhibitor pembrolizumab are approved by the US FDA for the treatment of limited prostate cancer patients. Prostate cancer has a complex tumor microenvironment (TME) in which various immunosuppressive molecules and mechanisms coexist and interact. Additionally, prostate cancer is considered a “cold” tumor with low levels of tumor mutational burden, low amounts of antigen-presenting and cytotoxic T-cell activation, and high levels of immunosuppressive molecules including cytokines/chemokines. Thus, understanding the mechanisms of immunosuppressive signaling activation and immune evasion will help develop more effective treatments for prostate cancer. The purpose of this review is to summarize emerging advances in prostate cancer immunotherapy, with a particular focus on the molecular mechanisms that lead to immune evasion in prostate cancer. At the same time, we also highlight some potential therapeutic targets to provide a theoretical basis for the treatment of prostate cancer.

The Relationship between Cancer and Paraoxonase 1

Extensive research has been carried out to understand and elucidate the mechanisms of paraoxonase 1 (PON1) in the development of diseases including cancer, cardiovascular diseases, neurological diseases, and inflammatory diseases. This review focuses on the relationship between PON1 and cancer. The data suggest that PON1, oxidative stress, chronic inflammation, and cancer are closely linked. Certainly, the gene expression of PON1 will remain challenging to study. Therefore, targeting PON1, redox-sensitive pathways, and transcription factors promise prevention and therapy in the development of several diseases, including cancer.

Noninvasive urine metabolomics of prostate cancer and its therapeutic approaches: a current scenario and future perspective

INTRODUCTION

The sensitive, specific, fast, robust and noninvasive biomarkers for the evaluation of prostate cancer (PC) remain elusive in medical research. However, efforts are in full sway to investigate and resolve these puzzles for clinical practice. Advances in modern analytical techniques, sample processing, and the emergence of multiple omics approaches have created a great hope for the development of better detection modalities for PC. The objective of the present review is to provide a concise overview of the PC metabolomics-based potential discriminating molecules in urine samples using nuclear magnetic resonance spectroscopy and mass spectrometry.

AREA COVERED

A literature search was executed to find the studies reporting the noninvasive urine-based biomarkers for the diagnosis and prognosis of underlying disease. Most studies have extensivelyreported PC discriminating molecules with their respective controls. Additionally, pathophysiology and the treatment paradigm of PC are summarized and related to the insights underpinning the therapeutic intervention of PC.

EXPERT OPINION

With multi-centric, global, comprehensive omics approaches via either a non- or least-invasive bio-matrix may open new avenues of research for PC biomarker discovery, backed by a molecular mechanistic outline.

Overcoming Immune Resistance in Prostate Cancer: Challenges and Advances

Simple Summary

Immunotherapy has changed the landscape of treatment modalities available for many different types of malignancies. However, the factors that influence the success of immunotherapeutics have not been as clearly seen in advanced prostate cancer, likely due to immunosuppressive factors that exist within the prostate cancer tumor microenvironment. While there have been many immunotherapeutics used for prostate cancer, the majority have targeted a single immunosuppressive mechanism resulting in limited clinical efficacy. More recent research centered on elucidating the key mechanisms of immune resistance in the prostate tumor microenvironment has led to the discovery of a range of new treatment targets. With that in mind, many clinical trials have now set out to evaluate combination immunotherapeutic strategies in patients with advanced prostate cancer, in the hopes of circumventing the immunosuppressive mechanisms.

Abstract

The use of immunotherapy has become a critical treatment modality in many advanced cancers. However, immunotherapy in prostate cancer has not been met with similar success. Multiple interrelated mechanisms, such as low tumor mutational burden, immunosuppressive cells, and impaired cellular immunity, appear to subvert the immune system, creating an immunosuppressive tumor microenvironment and leading to lower treatment efficacy in advanced prostate cancer. The lethality of metastatic castrate-resistant prostate cancer is driven by the lack of therapeutic regimens capable of generating durable responses. Multiple strategies are currently being tested to overcome immune resistance including combining various classes of treatment modalities. Several completed and ongoing trials have shown that combining vaccines or checkpoint inhibitors with hormonal therapy, radiotherapy, antibody–drug conjugates, chimeric antigen receptor T cell therapy, or chemotherapy may enhance immune responses and induce long-lasting clinical responses without significant toxicity. Here, we review the current state of immunotherapy for prostate cancer, as well as tumor-specific mechanisms underlying therapeutic resistance, with a comprehensive look at the current preclinical and clinical immunotherapeutic strategies aimed at overcoming the immunosuppressive tumor microenvironment and impaired cellular immunity that have largely limited the utility of immunotherapy in advanced prostate cancer.

The Role of Somatic Mutations on the Immune Response of the Tumor Microenvironment in Prostate Cancer

Immunotherapy has improved patient survival in many types of cancer, but for prostate cancer, initial results with immunotherapy have been disappointing. Prostate cancer is considered an immunologically excluded or cold tumor, unable to generate an effective T-cell response against cancer cells. However, a small but significant percentage of patients do respond to immunotherapy, suggesting that some specific molecular subtypes of this tumor may have a better response to checkpoint inhibitors. Recent findings suggest that, in addition to their function as cancer genes, somatic mutations of PTEN, TP53, RB1, CDK12, and DNA repair, or specific activation of regulatory pathways, such as ETS or MYC, may also facilitate immune evasion of the host response against cancer. This review presents an update of recent discoveries about the role that the common somatic mutations can play in changing the tumor microenvironment and immune response against prostate cancer. We describe how detailed molecular genetic analyses of the tumor microenvironment of prostate cancer using mouse models and human tumors are providing new insights into the cell types and pathways mediating immune responses. These analyses are helping researchers to design drug combinations that are more likely to target the molecular and immunological pathways that underlie treatment failure.

N-cadherin inhibitor creates a microenvironment that protect TILs from immune checkpoints and Treg cells

BACKGROUND

Few patients with prostate cancer benefit from current immunotherapies. Therefore, we aimed to explore new strategies to change this paradigm.

METHODS

Human tissues, cell lines and in vivo experiments were used to determine whether and how N-cadherin impacts the production of programmed death ligand-1 (PD-L1) and indole amine 2,3-dioxygenase (IDO-1) and whether N-cadherin can increase the production of effector (e)Treg cells. Then, we used PC3-bearing humanized non-obese diabetic/severe combined immunodeficiency IL2Rγnull (hNSG) mice with an intravenous injection of human CD34+ hematopoietic stem cells into the tail vein to evaluate whether the N-cadherin antagonist N-Ac-CHAVC-NH2 (designated ADH-1) could improve the therapeutic effect of tumor-infiltrating lymphocyte (TIL)-related treatment.

RESULTS

N-cadherin dramatically upregulated the expression of PD-L1 and IDO-1 through IFN-γ (interferongamma) signaling and increasing the production of free fatty acids that could promote the generation of eTreg cells. In preclinical experiments, immune reconstitution mediated by TILs slowed tumor growth and extended the survival time; however, this effect disappeared after immune system suppression by PD-L1, IDO-1 and eTreg cells. Furthermore, ADH-1 effectively reduced immunosuppression and enhanced TIL-related therapy.

CONCLUSIONS

These data show that the N-cadherin antagonist ADH-1 promotes TIL antitumor responses. This important hurdle must be overcome for tumors to respond to immunotherapy.

Integrated Characterization of lncRNA-Immune Interactions in Prostate Cancer

Prostate cancer is among the top mortality factors in male around the world. Long non-coding RNAs (lncRNAs) have been shown to play crucial roles in tumor biology and immunology. However, lncRNA-immune interactions have not yet examined in prostate cancer. Here, we performed integrated analysis to characterize lncRNA-immune interactions in prostate cancer through multidimensional aspects, including immune-related hallmarks, tumor immunogenomic signatures, immune-related biological processes, immune cells, and immune checkpoints. We dissected the dysregulation of lncRNAs and their clinical relevance in prostate cancer, such as RP11-627G23.1 and RP11-465N4.5. Immune-related hallmarks took up the major parts among top significant lncRNA-hallmark interactions. Our analysis revealed that TGF-β signaling pathway was the most frequent to associate with lncRNAs, which is a signature of immune response in cancer. In addition, immune response and its regulation were the most closely connected immunological processes with lncRNA, implying the regulatory roles of lncRNAs on immune response in prostate cancer. We found that memory resting CD4⁺ T cells were the most lncRNA-correlated immune cell. LINC00861 was found to be potentially intervening targets of immunotherapy for prostate cancer patients, which was significantly associated with PD-1 and CTLA4. Collectively, we offered a handy resource to investigate regulatory roles of lncRNAs on tumor immunology and the development of clinical utility of lncRNAs in prostate cancer.

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.

Immune-focused multi-omics analysis of prostate cancer: leukocyte Ig-Like receptors are associated with disease progression

Prostate cancer (PCa) immunotherapy has shown limited efficacy so far, even in advanced-stage cancers. The success rate of PCa immunotherapy might be improved by approaches more adapted to the immunobiology of the disease. The objective of this study was to perform a multi-omics analysis to identify immune genes associated with PCa progression to better characterize PCa immunobiology and propose new immunotherapeutic targets. mRNA, miRNA, methylation, copy number aberration, and single nucleotide variant datasets from The Cancer Genome Atlas PRAD cohort were analyzed after filtering for genes associated with immunity. Sparse partial least squares-discriminant analyses were performed to identify features associated with biochemical recurrence (BCR) in each type of omics data. Selected features predicted BCR with a balanced error rate (BER) of 0.20 to 0.51 in single-omics and of 0.05 in multi-omics analyses. Amongst features associated with BCR were genes from the Immunoglobulin Ig-like Receptor (LILR) family which are immune checkpoints with immunotherapeutic potential. Using Multivariate INTegrative (MINT) analysis, the association of five LILR genes with BCR was quantified in a combination of three RNA-seq datasets and confirmed with Kaplan-Meier analysis in both these and in an independent RNA-seq dataset. Finally, immunohistochemistry showed that a high number of LILRB1 positive cells within the tumors predicted long-term adverse outcomes. Thus, tumors characterized by abnormal expression of LILR genes have an elevated risk of recurring after definitive local therapy. The immunotherapeutic potential of these regulators to stimulate the immune response against PCa should be evaluated in pre-clinical models.

Inflammation as a Driver of Prostate Cancer Metastasis and Therapeutic Resistance

Simple Summary

Prostate cancer is the most common malignancy in men, with a high mortality rate when disease progresses to metastasis and therapeutic resistance. Evidence implicates inflammation as a driver of prostate cancer risk and has a significant impact on processes in the tumor microenvironment that facilitate progression to advanced therapeutically resistant disease. In this review, we discuss the sources of inflammation in the prostate, the functional contribution of the critical inflammatory effectors to prostate cancer initiation and metastatic progression, and the therapeutic challenges that they impose on treatment of advanced disease and overcoming therapeutic resistance. Full understanding of the role of inflammation in prostate cancer progression to advanced metastatic disease and tumor relapse will aid in the development of personalized predictive biomarkers and therapy to reduce the burden and mortality in prostate cancer patients.

Abstract

Prostate cancer is the most common malignancy among men, and progression to metastasis and the emergence of therapeutically resistant disease confers a high mortality rate. Growing evidence implicates inflammation as a driver of prostate cancer development and progression, resulting in increased cancer risk for prostate cancer. Population-based studies revealed that the use of antinflammatory drugs led to a 23% risk reduction prostate cancer occurrence, a negative association that was stronger in men who specifically used COX-2 inhibitors. Furthermore, patients that were taking aspirin had a 21% reduction in prostate cancer risk, and further, long-term users of daily low dose aspirin had a 29% prostate cancer risk reduction as compared to the controls. Environmental exposure to bacterial and viral infections, exposure to mutagenic agents, and genetic variations predispose the prostate gland to inflammation, with a coordinated elevated expression of inflammatory cytokines (IL-6, TGF-β). It is the dynamics within the tumor microenvironment that empower these cytokines to promote survival and growth of the primary tumor and facilitate disease progression by navigating the immunoregulatory network, phenotypic epithelial-mesenchymal transition (EMT), angiogenesis, anoikis resistance, and metastasis. In this review, we discuss the sources of inflammation in the prostate, the functional contribution of the critical inflammatory effectors to prostate cancer initiation and metastatic progression, and the therapeutic challenges that they impose on treatment of advanced disease and overcoming therapeutic resistance. Growing mechanistic evidence supports the significance of inflammation in localized prostate cancer, and the systemic impact of the process within the tumor microenvironment on disease progression to advanced therapeutically-resistant prostate cancer. Rigorous exploitation of the role of inflammation in prostate cancer progression to metastasis and therapeutic resistance will empower the development of precise biomarker signatures and effective targeted therapeutics to reduce the clinical burden and lethal disease in the future.

Intronic TP53 Polymorphisms Are Associated with Increased Δ133TP53 Transcript, Immune Infiltration and Cancer Risk

We investigated the influence of selected TP53 SNPs in exon 4 and intron 4 on cancer risk, clinicopathological features and expression of TP53 isoforms. The intron 4 SNPs were significantly over-represented in cohorts of mixed cancers compared to three ethnically matched controls, suggesting they confer increased cancer risk. Further analysis showed that heterozygosity at rs1042522(GC) and either of the two intronic SNPs rs9895829(TC) and rs2909430(AG) confer a 2.34-5.35-fold greater risk of developing cancer. These SNP combinations were found to be associated with shorter patient survival for glioblastoma and prostate cancer. Additionally, these SNPs were associated with tumor-promoting inflammation as evidenced by high levels of infiltrating immune cells and expression of the Δ133TP53 and TP53β transcripts. We propose that these SNP combinations allow increased expression of the Δ133p53 isoforms to promote the recruitment of immune cells that create an immunosuppressive environment leading to cancer progression.

Prostate cancer cell-intrinsic interferon signaling regulates dormancy and metastatic outgrowth in bone

The latency associated with bone metastasis emergence in castrate-resistant prostate cancer is attributed to dormancy, a state in which cancer cells persist prior to overt lesion formation. Using single-cell transcriptomics and ex vivo profiling, we have uncovered the critical role of tumor-intrinsic immune signaling in the retention of cancer cell dormancy. We demonstrate that loss of tumor-intrinsic type I IFN occurs in proliferating prostate cancer cells in bone. This loss suppresses tumor immunogenicity and therapeutic response and promotes bone cell activation to drive cancer progression. Restoration of tumor-intrinsic IFN signaling by HDAC inhibition increased tumor cell visibility, promoted long-term antitumor immunity, and blocked cancer growth in bone. Key findings were validated in patients, including loss of tumor-intrinsic IFN signaling and immunogenicity in bone metastases compared to primary tumors. Data herein provide a rationale as to why current immunotherapeutics fail in bone-metastatic prostate cancer, and provide a new therapeutic strategy to overcome the inefficacy of immune-based therapies in solid cancers.

Detailed Molecular and Immune Marker Profiling of Archival Prostate Cancer Samples Reveals an Inverse Association between TMPRSS2:ERG Fusion Status and Immune Cell Infiltration

Prostate cancer is a significant global health issue, and limitations to current patient management pathways often result in overtreatment or undertreatment. New ways to stratify patients are urgently needed. We conducted a feasibility study of such novel assessments, looking for associations between genomic changes and lymphocyte infiltration. An innovative workflow using an in-house targeted sequencing panel, immune cell profiling using an image analysis pipeline, RNA sequencing, and exome sequencing in select cases was tested. Gene fusions were profiled by RNA sequencing in 27 of 27 cases, and a significantly higher tumor-infiltrating lymphocyte (TIL) count was noted in tumors without a TMPRSS2:ERG fusion compared with those with the fusion (P = 0.01). Although this finding was not replicated in a larger validation set (n = 436) of The Cancer Genome Atlas images, there was a trend in the same direction. Differential expression analysis of TIL-high and TIL-low tumors revealed the enrichment of both innate and adaptive immune response pathways. Mutations in mismatch repair genes (MLH1 and MSH6 mutations in 1 of 27 cases) were identified. We describe a potential immune escape mechanism in TMPRSS2:ERG fusion-positive tumors. Detailed profiling, as shown herein, can provide novel insights into tumor biology. Likely differences with findings with other cohorts are related to methods used to define region of interest, but this warrants further study in a larger cohort.

Breast cancer: Biology, biomarkers, and treatments

During the past recent years, various therapies emerged in the era of breast cancer. Breast cancer is a heterogeneous disease in which genetic and environmental factors are involved. Breast cancer stem cells (BCSCs) are the main player in the aggressiveness of different tumors and also, these cells are the main challenge in cancer treatment. Moreover, the major obstacle to achieve an effective treatment is resistance to therapies. There are various types of treatment for breast cancer (BC) patients. Therefore, in this review, we present the current treatments, novel approaches such as antibody-drug conjugation systems (ADCs), nanoparticles (albumin-, metal-, lipid-, polymer-, micelle-based nanoparticles), and BCSCs-based therapies. Furthermore, prognostic and predictive biomarkers will be discussed also biomarkers that have been applied by some tests such as Oncotype DX, Mamm αPrint, and uPA/PAI-1 are regarded as suitable prognostic and predictive factors in breast cancer.

Stope M. Gas Plasma-Treated Prostate Cancer Cells Augment Myeloid Cell Activity and Cytotoxicity

Despite recent improvements in cancer treatment, with many of them being related to foster antitumor immunity, tumor-related deaths continue to be high. Novel avenues are needed to complement existing therapeutic strategies in oncology. Medical gas plasma technology recently gained attention due to its antitumor activity. Gas plasmas act via the local deposition of a plethora of reactive oxygen species (ROS) that promote the oxidative cancer cell death. The immunological consequences of plasma-mediated tumor cell death are only poorly understood, however. To this end, we exposed two prostate cancer cell lines (LNCaP, PC3) to gas plasma in vitro, and investigated the immunomodulatory effects of the supernatants in as well as of direct co-culturing with two human myeloid cell lines (THP-1, HL-60). After identifying the cytotoxic action of the kINPen plasma jet, the supernatants of plasma-treated prostate cancer cells modulated myeloid cell-related mitochondrial ROS production and their metabolic activity, proliferation, surface marker expression, and cytokine release. Direct co-culture amplified differentiation-like surface marker expression in myeloid cells and promoted their antitumor-toxicity in the gas plasma over the untreated control conditions. The results suggest that gas plasma-derived ROS not only promote prostate cancer cell death but also augment myeloid cell activity and cytotoxicity.

BRF1 accelerates prostate tumourigenesis and perturbs immune infiltration

BRF1 is a rate-limiting factor for RNA Polymerase III-mediated transcription and is elevated in numerous cancers. Here, we report that elevated levels of BRF1 associate with poor prognosis in human prostate cancer. In vitro studies in human prostate cancer cell lines demonstrated that transient overexpression of BRF1 increased cell proliferation whereas the transient downregulation of BRF1 reduced proliferation and mediated cell cycle arrest. Consistent with our clinical observations, BRF1 overexpression in a Pten-deficient mouse (PtenΔ/Δ BRF1Tg) prostate cancer model accelerated prostate carcinogenesis and shortened survival. In PtenΔ/Δ BRF1Tg tumours, immune and inflammatory processes were altered, with reduced tumoral infiltration of neutrophils and CD4 positive T cells, which can be explained by decreased levels of complement factor D (CFD) and C7 components of the complement cascade, an innate immune pathway that influences the adaptive immune response. We tested if the secretome was involved in BRF1-driven tumorigenesis. Unbiased proteomic analysis on BRF1-overexpresing PC3 cells confirmed reduced levels of CFD in the secretome, implicating the complement system in prostate carcinogenesis. We further identify that expression of C7 significantly correlates with expression of CD4 and has the potential to alter clinical outcome in human prostate cancer, where low levels of C7 associate with poorer prognosis.

Advances of Zinc Signaling Studies in Prostate Cancer

Prostate cancer (PCa) is one of the most common cancers and the second leading cause of cancer-related death among men worldwide. Despite progresses in early diagnosis and therapeutic strategies, prognosis for patients with advanced PCa remains poor. Noteworthily, a unique feature of healthy prostate is its highest level of zinc content among all soft tissues in the human body, which dramatically decreases during prostate tumorigenesis. To date, several reviews have suggested antitumor activities of zinc and its potential as a therapeutic strategy of PCa. However, an overview about the role of zinc and its signaling in PCa is needed. Here, we review literature related to the content, biological function, compounds and clinical application of zinc in PCa. We first summarize zinc content in prostate tissue and sera of PCa patients with their clinical relevance. We then elaborate biological functions of zinc signaling in PCa on three main aspects, including cell proliferation, death and tumor metastasis. Finally, we discuss clinical applications of zinc-containing compounds and proteins involved in PCa signaling pathways. Based on currently available studies, we conclude that zinc plays a tumor suppressive role and can serve as a biomarker in PCa diagnosis and therapies.

CHALLENGES IN MANIPULATING IMMUNE SYSTEM TO TREAT PROSTATE CANCER

First cancer vaccine that was approved for routine therapy was sipuleucel-T for treatment of patients with metastatic castration resistant prostate cancer. However, other immunotherapy drugs evaluated in prostate cancer, particularly immune checkpoint inhibitors, have failed to show therapeutic effect. There are several potential explanations for lack of response of prostate cancer to these drugs. These explanations, which are related to specific genetic (e.g. low mutational burden) and immunological (e.g. immunosuppressive tumor immune microenvironment) background of prostate cancer are discussed in this review. Also, new therapeutic strategies to overcome prostate cancer immunotherapy resistance and to select subgroups of patients that could benefit from immunotherapy are outlined.

Tumor-infiltrating lymphocytes from human prostate tumors reveal anti-tumor reactivity and potential for adoptive cell therapy

Advanced prostate cancer remains incurable and is the second leading cause of mortality in men. Immunotherapy based on the adoptive transfer of tumor-infiltrating lymphocytes (TIL) has demonstrated promising clinical results in patients with metastatic melanoma and lately also in other solid tumors. However, the ability to obtain TIL from patients with prostate cancer, considered poorly immunogenic, remains unknown. In this study, we investigate the feasibility of isolating and expanding TIL from primary prostate tumors. We collected tumor specimens from eight patients with diagnosed prostate adenocarcinoma undergoing radical prostatectomy and were able to successfully expand multiple autologous TIL cultures from all patients. Twenty-eight prostate-TIL cultures were further expanded using a standard rapid expansion procedure under Good Manufacturing Practice conditions. TIL cultures were phenotypically characterized for T cell subset composition, differentiation status and co-inhibitory/stimulatory markers such as PD-1, TIM-3, LAG-3, and CD28 and were found to have in general similarity to TIL obtained from patients with melanoma and lung carcinoma previously treated at our center. All analyzed TIL cultures were functional as determined by the capability to produce high level of IFNγ upon stimuli. Most importantly, co-culture assays of prostate-TIL with autologous tumors demonstrated anti-tumor reactivity. In conclusion, these findings demonstrate that functional and anti-tumor reactive TIL can be obtained, despite the immunosuppressive microenvironment of the cancer, thus this study supports the development of TIL therapy for prostate cancer patients.

The Δ133p53β isoform promotes an immunosuppressive environment leading to aggressive prostate cancer

Prostate cancer is the second most common cancer in men, for which there are no reliable biomarkers or targeted therapies. Here we demonstrate that elevated levels of Δ133TP53β isoform characterize prostate cancers with immune cell infiltration, particularly T cells and CD163+ macrophages. These cancers are associated with shorter progression-free survival, Gleason scores ≥ 7, and an immunosuppressive environment defined by a higher proportion of PD-1, PD-L1 and colony-stimulating factor 1 receptor (CSF1R) positive cells. Consistent with this, RNA-seq of tumours showed enrichment for pathways associated with immune signalling and cell migration. We further show a role for hypoxia and wild-type p53 in upregulating Δ133TP53 levels. Finally, AUC analysis showed that Δ133TP53β expression level alone predicted aggressive disease with 88% accuracy. Our data identify Δ133TP53β as a highly accurate prognostic factor for aggressive prostate cancer.

Utilizing precision medicine to modulate the prostate tumor microenvironment and enhance immunotherapy

The last two decades of cancer research have seen two major advancements in our ability to treat cancer: precision medicine and immunotherapy. While these approaches have shown striking anticancer efficacy in numerous malignancies, they have not shown similar success and applicability in advanced prostate cancer patients. The fields of precision medicine and immunotherapy have come to realize that targeted therapies are capable of not only inhibiting tumor cell growth, but also promoting antitumor immunity by modulating the tumor microenvironment. Here we examine how personalized medicine can be used to target the tumor immune microenvironment in prostate cancer, with the goal of enhancing clinical responses to immunotherapy.

The Tumor Immune Contexture of Prostate Cancer

One in seven men in North America is expected to be diagnosed with prostate cancer (PCa) during their lifetime (1, 2). While a wide range of treatment options including surgery, radiation, androgen deprivation and chemotherapy have been in practice for the last few decades, there are limited treatment options for metastatic and treatment resistant disease. Immunotherapy targeting T-cell associated immune checkpoints such as CTLA-4, PD-L1, and PD-1 have not yet proven to be efficacious in PCa. Tumor mutational burden, mutations in DNA damage repair genes, immune cell composition and density in combination with their spatial organization, and expression of immune checkpoint proteins are some of the factors influencing the success of immune checkpoint inhibitor therapies. The paucity of these features in PCa potentially makes them unresponsive to contemporary immune checkpoint inhibition. In this review, we highlight the hallmark events in the PCa tumor immune microenvironment and provide insights into the current state of knowledge in this field with a focus on the role of tumor cell intrinsic events that potentially regulate immune related events and determine therapeutic outcomes. We surmise that the cumulative impact of factors such as the pre-treatment immune status, PTEN expression, DNA damage repair gene mutations, and the effects of conventionally used treatments on the anti-tumor immune response should be considered in immunotherapy trial design in PCa.

An immunohistochemical study of T and B lymphocyte density in prostatic hyperplasia and prostate carcinoma in dogs

The aim of this study was to characterise T and B lymphocyte density in 6 normal prostates, 15 benign prostatic hyperplasia (BPH) and 24 prostate carcinomas (PCs) in dogs by immunohistochemistry. Results revealed a statistically significant increase of T and B cells in PC compared to normal specimens and BPH. Regarding PC histological variants, lower number of CD3⁺ and CD79⁺ lymphocytes were observed in the most undifferentiated (solid) type. CD3⁺ cell density was positively correlated with survival time. These results may help in understanding the immunological mechanisms regulating BPH and PC development and progression, as well as providing background data for future immunotherapeutic trials.

Advancing therapies in metastatic castration-resistant prostate cancer

INTRODUCTION

Prostate cancer is the second most common cause of cancer worldwide and is the most frequently detected cancer in the European Union in men over 50 years of age. Androgen deprivation therapy remains the cornerstone of treatment for recurrent or metastatic disease. Unfortunately, nearly all patients will develop resistance to androgen blockade leading to castration-resistant prostate cancer (CRPC). Over the last 10 years, new treatments have dramatically improved overall survival of men with mCRPC. Current therapies are based on AR-axis inhibitors and taxane-based chemotherapies, as well as radiopharmaceuticals and Sipuleucel T.

AREAS COVERED

The authors provide a review of the current field of systemic therapy in metastatic CRPC. This is followed by an in-depth analysis of recent developments in treatment, and the biological rationale behind these therapies.

EXPERT OPINION

Since several trials with docetaxel or novel hormonal agents showed improvement in overall survival in metastatic castration-sensitive prostate cancer, as well as in non-metastatic castration-resistant patients, it is expected that a growing subgroup of patients will be exposed earlier to chemotherapy and to AR targeted agents. It becomes then fundamental to find novel strategies to overcome drug resistance and further improve survival.

Recent Advances in Prostate Cancer Treatment and Drug Discovery

Novel drugs, drug sequences and combinations have improved the outcome of prostate cancer in recent years. The latest approvals include abiraterone acetate, enzalutamide and apalutamide which target androgen receptor (AR) signaling, radium-223 dichloride for reduction of bone metastases, sipuleucel-T immunotherapy and taxane-based chemotherapy. Adding abiraterone acetate to androgen deprivation therapy (ADT) in order to achieve complete androgen blockade has proven highly beneficial for treatment of locally advanced prostate cancer and metastatic hormone-sensitive prostate cancer (mHSPC). Also, ADT together with docetaxel treatment showed significant benefit in mHSPC. Ongoing clinical trials for different subgroups of prostate cancer patients include the evaluation of the second-generation AR antagonists enzalutamide, apalutamide and darolutamide, of inhibitors of the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) pathway, of inhibitors of DNA damage response, of targeted alpha therapy and of prostate-specific membrane antigen (PSMA) targeting approaches. Advanced clinical studies with immune checkpoint inhibitors have shown limited benefits in prostate cancer and more trials are needed to demonstrate efficacy. The identification of improved, personalized treatments will be much supported by the major progress recently made in the molecular characterization of early- and late-stage prostate cancer using “omics” technologies. This has already led to novel classifications of prostate tumors based on gene expression profiles and mutation status, and should greatly help in the choice of novel targeted therapies best tailored to the needs of patients.