Magnitude of PD-1, PD-L1 and T Lymphocyte Expression on Tissue from Castration-Resistant Prostate Adenocarcinoma: An Exploratory Analysis

Peptides-functionalized gold nanostars enhanced degradation of PD-L1 for improved prostate cancer immunotherapy

Blockage of the interaction between programmed death receptor-1 (PD-1) and programmed death ligand-1 (PD-L1) can restore T-cell activity and enhance antitumor immunity. PD-1/PD-L1 pathway inhibitors have promising applications in the treatment of advanced prostate cancer (PCa). We successfully developed a peptides-functionalized gold nanoconstruct (P-AuNS) consisted of PD-L1-binding peptide (PD-L1pep, P) and gold nanostar (AuNS), which could bind to cell-surface PD-L1 specifically and deliver PD-L1 into PCa cells with high efficiency. In PCa cells, P-AuNS can efficiently degrade PD-L1 in a lysosomal-dependent manner. In the co-culture system of Jurkat cells and DU145 cells, P-AuNS restored the proliferative capacity and interferon-gamma (IFN-γ) secretion level of Jurkat cells inhibited by co-cultured DU145 cells, indicating that P-AuNS effectively hampered the interaction between PD-1 and PD-L1. In addition, in PCa-bearing mice, P-AuNS can effectively inhibit tumor growth and down-regulate PD-L1 protein levels, and in vivo experimental results show that P-AuNS has no systemic toxicity. P-AuNS block the interaction between PD-1 and PD-L1 by efficiently degrading PD-L1, thus restoring the antitumor activity of T cells and inhibiting tumor progression of PCa. In all, P-AuNS has great promise as a potential immunotherapy strategy in the treatment of advanced PCa and even other solid tumors.

T cell landscape in the microenvironment of human solid tumors

T cells are the main effectors involved in anti-tumor immunity, mediating most of the adaptive response towards cancer. After priming in lymph nodes, tumor antigens-specific naïve T lymphocytes proliferate and differentiate into effector CD4+ and CD8+ T cells that migrate from periphery into tumor sites aiming to eliminate cancer cells. Then while most effector T cells die, a small fraction persists and recirculates as long-lived memory T cells which generate enhanced immune responses when re-encountering the same antigen. A number of T (and non-T) cell subsets, stably resides in non-lymphoid peripheral tissues and may provide rapid immune response independently of T cells recruited from blood, against the reemergence of cancer cells. When tumor grows, however, tumor cells have evaded immune surveillance of effector cells (NK and CTL cells) which are exhausted, thus favoring the local expansion of T (and non-T) regulatory cells. In this review, the current knowledge of features of T cells present in the tumor microenvironment (TME) of solid adult and pediatric tumors, the mechanisms upregulating immune-checkpoint molecules and transcriptional and epigenetic landscapes leading to dysfunction and exhaustion of T effector cells are reviewed. The interaction of T cells with cancer- or TME non-neoplastic cells and their secreted molecules shape the T cell profile compromising the intrinsic plasticity of T cells and, therefore, favoring immune evasion. In this phase regulatory T cells contribute to maintain a high immunosuppressive TME thus facilitating tumor cell proliferation and metastatic spread. Despite the advancements of cancer immunotherapy, many tumors are unresponsive to immune checkpoint inhibitors, or therapeutical vaccines or CAR T cell-based adoptive therapy: some novel strategies to improve these T cell-based treatments are lastly proposed.

Advances in metastatic prostate cancer circulating tumor cell enrichment technologies and clinical studies

Circulating tumor cells (CTCs) have emerged as a pivotal tool that enables molecular interrogation of patient tumor cells and association with clinical outcomes. In prostate cancer specifically, where tumor biopsies from patients with bone metastasis are extremely challenging, CTCs offer a viable and established source of tumor "biopsy". While the prognostic value of CTC enumeration in metastatic prostate cancer is established, there is a compelling need for molecular CTC characterization for effective patient stratification and disease management. The clinical utility of CTCs has been advanced by the evolution of enrichment technologies and their molecular characterization. Enrichment technologies have evolved from strictly EpCAM-based enrichment to antigen-agnostic enrichment, while their clinical utility has evolved from enumeration to advanced downstream analyses including CTC proteomics, transcriptomics and genomics. This chapter offers a comprehensive overview of recent advancements in CTC enrichment and analytical technologies while highlighting pivotal clinical studies in prostate cancer, that utilize CTCs to determine the molecular basis of clinical response and resistance, to assist in disease management and treatment customization.

Molecular Mechanisms of Prostate Cancer Development in the Precision Medicine Era: A Comprehensive Review

The progression of prostate cancer (PCa) relies on the activation of the androgen receptor (AR) by androgens. Despite efforts to block this pathway through androgen deprivation therapy, resistance can occur through several mechanisms, including the abnormal activation of AR, resulting in castration-resistant PCa following the introduction of treatment. Mutations, amplifications, and splicing variants in AR-related genes have garnered attention in this regard. Furthermore, recent large-scale next-generation sequencing analysis has revealed the critical roles of AR and AR-related genes, as well as the DNA repair, PI3K, and cell cycle pathways, in the onset and progression of PCa. Moreover, research on epigenomics and microRNA has increasingly become popular; however, it has not translated into the development of effective therapeutic strategies. Additionally, treatments targeting homologous recombination repair mutations and the PI3K/Akt pathway have been developed and are increasingly accessible, and multiple clinical trials have investigated the efficacy of immune checkpoint inhibitors. In this comprehensive review, we outline the status of PCa research in genomics and briefly explore potential future developments in the field of epigenetic modifications and microRNAs.

Recent advances and future perspectives in the therapeutics of prostate cancer

Prostate cancer (PC) is one of the most common cancers in males and the fifth leading reason of death. Age, ethnicity, family history, and genetic defects are major factors that determine the aggressiveness and lethality of PC. The African population is at the highest risk of developing high-grade PC. It can be challenging to distinguish between low-risk and high-risk patients due to the slow progression of PC. Prostate-specific antigen (PSA) is a revolutionary discovery for the identification of PC. However, it has led to an increase in over diagnosis and over treatment of PC in the past few decades. Even if modifications are made to the standard PSA testing, the specificity has not been found to be significant. Our understanding of PC genetics and proteomics has improved due to advances in different fields. New serum, urine, and tissue biomarkers, such as PC antigen 3 (PCA3), have led to various new diagnostic tests, such as the prostate health index, 4K score, and PCA3. These tests significantly reduce the number of unnecessary and repeat biopsies performed. Chemotherapy, radiotherapy, and prostatectomy are standard treatment options. However, newer novel hormone therapy drugs with a better response have been identified. Androgen deprivation and hormonal therapy are evolving as new and better options for managing hormone-sensitive and castration-resistant PC. This review aimed to highlight and discuss epidemiology, various risk factors, and developments in PC diagnosis and treatment regimens.

Potential of Personalized Dendritic Cell-Based Immunohybridoma Vaccines to Treat Prostate Cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer and the second most common cause of death due to cancer. About 30% of patients with PCa who have been castrated develop a castration-resistant form of the disease (CRPC), which is incurable. In the last decade, new treatments that control the disease have emerged, slowing progression and spread and prolonging survival while maintaining the quality of life. These include immunotherapies; however, we do not yet know the optimal combination and sequence of these therapies with the standard ones. All therapies are not always suitable for every patient due to co-morbidities or adverse effects of therapies or both, so there is an urgent need for further work on new therapeutic options. Advances in cancer immunotherapy with an immune checkpoint inhibition mechanism (e.g., ipilimumab, an anti-CTLA-4 inhibitor) have not shown a survival benefit in patients with CRPC. Other immunological approaches have also not given clear results, which has indirectly prevented breakthrough for this type of therapeutic strategy into clinical use. Currently, the only approved form of immunotherapy for patients with CRPC is a cell-based medicine, but it is only available to patients in some parts of the world. Based on what was gained from recently completed clinical research on immunotherapy with dendritic cell-based immunohybridomas, the aHyC dendritic cell vaccine for patients with CRPC, we highlight the current status and possible alternatives that should be considered in the future.

Development and validation of novel inflammatory response-related gene signature to predict prostate cancer recurrence and response to immune checkpoint therapy

The aim of this study is to construct an inflammatory response-related genes (IRRGs) signature to monitor biochemical recurrence (BCR) and treatment effects in prostate cancer patients (PCa). A gene signature for inflammatory responses was constructed on the basis of the data from the Cancer Genome Atlas (TCGA) database, and validated in external datasets. It was analyzed using receiver operating characteristic curve, BCR-free survival, Cox regression, and nomogram. Distribution analysis and external model comparison were utilized. Then, enrichment analysis, tumor mutation burden, tumor immune microenvironment, and immune cell infiltration signatures were investigated. The role of the signature in immunotherapy was evaluated. The expression patterns of core genes were verified by RNA sequencing. We identified an IRRGs signature in the TCGA-PRAD cohort and verified it well in two other independent external datasets. The signature was a robust and independent prognostic index for predicting the BCR of PCa. The high-risk group of our signature predicted a shortened BCR time and an aggressive disease progression. A nomogram was constructed to predict BCR-free time in clinical practices. Neutrophils and CD8+ T cells were in higher abundance among the low-risk individuals. Immune functions varied significantly between the two groups and immune checkpoint therapy worked better for the low-risk patients. The expression of four IRRGs showed significant differences between PCa and surrounding benign tissues, and were validated in BPH-1 and DU145 cell lines by RNA sequencing. Our signature served as a reliable and promising biomarker for predicting the prognosis and evaluating the efficacy of immunotherapy, facilitating a better outcome for PCa patients.

Risk of colon cancer-related death in people who had cancer in the past

BACKGROUND

The rate of second primary malignancies (SPM) is gradually increasing. Yet, the risk of death from primary cancer vs. SPM is still not well understood. In this study, we investigated the survival of patients with colorectal cancer (as SPM) who had cancer in the past (prior cancer) and the risk factors of SPM death in this population.

MATERIALS AND METHODS

Based on the Surveillance, Epidemiology, and End Results (SEER) database, we identified 1866 colon cancer patients with prior cancer in our main cohort and 43,959 colon cancer patients, including 37,440 patients with colon cancer as only malignancy and 6519 patients with colon cancer as subsequent colon cancer (SCC), in a second cohort and 3429 colon cancer patients, including 2371 patients with prior colon cancer (PCC) and 1058 patients with colon cancer as SPM, in a third cohort. After propensity score matching, 6519 pairs of subjects were identified in second cohort.

RESULTS

Patients with prior prostate and breast cancer had a higher risk of developing colon cancer compared to those with gastrointestinal cancer. Also, colon cancer patients with different prior cancer had different survival rates. Furthermore, except for prior lung cancer (52.78 vs. 25.93%), most subjects died due to colon cancer complications. The ratio of colon cancer deaths to prior cancer deaths in patients with a low stage and high stage was 1.51 and 6.64, respectively. In addition, colon cancer-specific survival (CSS) and OS rates were significantly lower in subjects with colon cancer as the SPM than in those with PCC. Also, compared with PCC, SPM was associated with OS and CSS with HR 1.59 (95 CI 1.43-1.78) and HR 2.00 (95% CI 1.70-2.36). Furthermore, compared with only colon cancer, SCC was associated with OS and CSS with HR 1.23 (95 CI 1.17-1.29) and HR 1.13 (95% CI 1.06-1.21).

CONCLUSIONS

Prior cancer was found to have an adverse impact on OS in patients with colon cancer (secondary cancer), most of whom died due to colon cancer as secondary cancer itself rather than prior cancer. Early detection and treatment strategies should be investigated in this population.

Traditional Chinese medicine CFF-1 exerts a potent anti-tumor immunity to hinder tumor growth and metastasis in prostate cancer through EGFR/JAK1/STAT3 pathway to inhibit PD-1/PD-L1 checkpoint signaling

BACKGROUND

Traditional Chinese Medicine (TCM) CFF-1 has been used in clinic for prostate cancer therapy in China. We reported before CFF-1 induced cell apoptosis via suppressing EGFR-related pathways, reminding us its potential role associated with antitumor immunity.

PURPOSE

The study was aimed to investigate the regulatory mechanism of CFF-1 on PD-L1/PD-1-mediated tumor immune escape.

METHODS

Prostate-specific antigen (PSA) test and the functional assessment of cancer therapy-prostate (FACT-P) and karnosky performance status (KPS) questionnaires were carried out to evaluate patient' condition before and after therapy. Flow cytometry (FCM) was used for analyzing cell apoptosis, T lymphocyte subsets and cell cycle. Western blotting and Immunohistochemistry (IHC) were performed to measure protein expressions. The synergy of drug combination was assessed by calculating combination index (CI).

RESULTS

CFF-1 obviously decreased PSA and improved the quality of life in patients with advanced prostate cancer. PD-L1 was highly expressed in prostate cancer cells including LNCaP, 22Rv1, PC-3, DU145 and RM-1. PD-1/PD-L1 was upregulated in tumorigenesis and tumor progression of subcutaneous homograft mouse model with immune response, where CD3+ T cell subsets were declined. CFF-1 inhibited PD-L1 expression in prostate cancer cells in a time/dose-dependent manner and blocked tumor growth by suppressing PD-1/PD-L1 upregulation to promote the recovery of CD3+ T lymphocytes, especially CD4+ T cell subset, accompanied by the downregulation of CD4+ FOXP3+ T cell subset. CFF-1 also prolonged the survival and inhibited lung metastasis in tail vein prostate cancer mouse model while repressing PD-1/PD-L1. CFF-1 in combination with docetaxol (DTX) produced a synergistic effects by sensitizing the inhibitory effect of DTX on JAK1/STAT3 pathway targeting PD-L1 blockade.

CONCLUSION

CFF-1 inhibited tumor growth and lung metastasis by blocking PD-1/PD-L1 to ameliorate T lymphocyte immune response through EGFR/JAK1/STAT3 pathway, suggesting that CFF-1 might be a promising treatment to resist tumor immunosuppression for prostate cancer patients.

Immunotherapy in Advanced Prostate Cancer: Current Knowledge and Future Directions

The advent of immunotherapy has revolutionized cancer treatment. Unfortunately, this has not been the case for metastatic castration-resistant prostate cancer (mCRPC), likely due to the heterogeneous and immune-suppressive microenvironment present in prostate cancer. The identification of molecular biomarkers that could predict response to immunotherapy represents one of the current challenges in this clinical scenario. The management of advanced castration-resistant prostate cancer is rapidly evolving and immunotherapy treatments, mostly consisting of immune checkpoint inhibitors combinations, BiTE® (bispecific T-cell engager) immune therapies, and chimeric antigen receptors (CAR) are in development with promising results. This review analyses the current evidence of immunotherapy treatments for mCRPC, evaluating past failures and promising approaches and discussing the directions for future research.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review (Part 6): Correlation of PD-L1 Expression with the Status of Mismatch Repair System, BRCA, PTEN, and Other Genes

Pembrolizumab (anti-PD-1) is allowed in selected metastatic castration-resistant prostate cancer (PC) patients showing microsatellite instability/mismatch repair system deficiency (MSI-H/dMMR). BRCA1/2 loss-of-function is linked to hereditary PCs and homologous recombination DNA-repair system deficiency: poly-ADP-ribose-polymerase inhibitors can be administered to BRCA-mutated PC patients. Recently, docetaxel-refractory metastatic castration-resistant PC patients with BRCA1/2 or ATM somatic mutations had higher response rates to pembrolizumab. PTEN regulates cell cycle/proliferation/apoptosis through pathways including the AKT/mTOR, which upregulates PD-L1 expression in PC. Our systematic literature review (PRISMA guidelines) investigated the potential correlations between PD-L1 and MMR/MSI/BRCA/PTEN statuses in PC, discussing few other relevant genes. Excluding selection biases, 74/677 (11%) PCs showed dMMR/MSI; 8/67 (12%) of dMMR/MSI cases were PD-L1+. dMMR-PCs included ductal (3%) and acinar (14%) PCs (all cases tested for MSI were acinar-PCs). In total, 15/39 (39%) PCs harbored BRCA1/2 aberrations: limited data are available for PD-L1 expression in these patients. 13/137 (10%) PTEN- PCs were PD-L1+; 10/29 (35%) PD-L1+ PCs showed PTEN negativity. SPOP mutations may increase PD-L1 levels, while the potential correlation between PD-L1 and ERG expression in PC should be clarified. Further research should verify how the efficacy of PD-1 inhibitors in metastatic castration-resistant PCs is related to dMMR/MSI, DNA-damage repair genes defects, or PD-L1 expression.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 7: PD-L1 Expression in Liquid Biopsy

Liquid biopsy is an accessible, non-invasive diagnostic tool for advanced prostate cancer (PC) patients, potentially representing a real-time monitoring test for tumor evolution and response to treatment through the analysis of circulating tumor cells (CTCs) and exosomes. We performed a systematic literature review (PRISMA guidelines) to describe the current knowledge about PD-L1 expression in liquid biopsies of PC patients: 101/159 (64%) cases revealed a variable number of PD-L1+ CTCs. Outcome correlations should be investigated in larger series. Nuclear PD-L1 expression by CTCs was occasionally associated with worse prognosis. Treatment (abiraterone, enzalutamide, radiotherapy, checkpoint-inhibitors) influenced PD-L1+ CTC levels. Discordance in PD-L1 status was detected between primary vs. metastatic PC tissue biopsies and CTCs vs. corresponding tumor tissues. PD-L1 is also released by PC cells through soluble exosomes, which could inhibit the T cell function, causing immune evasion. PD-L1+ PC-CTC monitoring and genomic profiling may better characterize the ongoing aggressive PC forms compared to PD-L1 evaluation on primary tumor biopsies/prostatectomy specimens (sometimes sampled a long time before recurrence/progression). Myeloid-derived suppressor cells and dendritic cells (DCs), which may have immune-suppressive effects in tumor microenvironment, have been found in PC patients circulation, sometimes expressing PD-L1. Occasionally, their levels correlated to clinical outcome. Enzalutamide-progressing castration-resistant PC patients revealed increased PD-1+ T cells and circulating PD-L1/2+ DCs.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 5: Epigenetic Regulation of PD-L1

Epigenetic alterations (including DNA methylation or miRNAs) influence oncogene/oncosuppressor gene expression without changing the DNA sequence. Prostate cancer (PC) displays a complex genetic and epigenetic regulation of cell-growth pathways and tumor progression. We performed a systematic literature review (following PRISMA guidelines) focused on the epigenetic regulation of PD-L1 expression in PC. In PC cell lines, CpG island methylation of the CD274 promoter negatively regulated PD-L1 expression. Histone modifiers also influence the PD-L1 transcription rate: the deletion or silencing of the histone modifiers MLL3/MML1 can positively regulate PD-L1 expression. Epigenetic drugs (EDs) may be promising in reprogramming tumor cells, reversing epigenetic modifications, and cancer immune evasion. EDs promoting a chromatin-inactive transcriptional state (such as bromodomain or p300/CBP inhibitors) downregulated PD-L1, while EDs favoring a chromatin-active state (i.e., histone deacetylase inhibitors) increased PD-L1 expression. miRNAs can regulate PD-L1 at a post-transcriptional level. miR-195/miR-16 were negatively associated with PD-L1 expression and positively correlated to longer biochemical recurrence-free survival; they also enhanced the radiotherapy efficacy in PC cell lines. miR-197 and miR-200a-c positively correlated to PD-L1 mRNA levels and inversely correlated to the methylation of PD-L1 promoter in a large series. miR-570, miR-34a and miR-513 may also be involved in epigenetic regulation.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 3: PD-L1, Intracellular Signaling Pathways and Tumor Microenvironment

The tumor microenvironment (TME) includes immune (T, B, NK, dendritic), stromal, mesenchymal, endothelial, adipocytic cells, extracellular matrix, and cytokines/chemokines/soluble factors regulating various intracellular signaling pathways (ISP) in tumor cells. TME influences the survival/progression of prostate cancer (PC), enabling tumor cell immune-evasion also through the activation of the PD-1/PD-L1 axis. We have performed a systematic literature review according to the PRISMA guidelines, to investigate how the PD-1/PD-L1 pathway is influenced by TME and ISPs. Tumor immune-escape mechanisms include suppression/exhaustion of tumor infiltrating cytotoxic T lymphocytes, inhibition of tumor suppressive NK cells, increase in immune-suppressive immune cells (regulatory T, M2 macrophagic, myeloid-derived suppressor, dendritic, stromal, and adipocytic cells). IFN-γ (the most investigated factor), TGF-β, TNF-α, IL-6, IL-17, IL-15, IL-27, complement factor C5a, and other soluble molecules secreted by TME components (and sometimes increased in patients' serum), as well as and hypoxia, influenced the regulation of PD-L1. Experimental studies using human and mouse PC cell lines (derived from either androgen-sensitive or androgen-resistant tumors) revealed that the intracellular ERK/MEK, Akt-mTOR, NF-kB, WNT and JAK/STAT pathways were involved in PD-L1 upregulation in PC. Blocking the PD-1/PD-L1 signaling by using immunotherapy drugs can prevent tumor immune-escape, increasing the anti-tumor activity of immune cells.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 1: Focus on Immunohistochemical Results with Discussion of Pre-Analytical and Interpretation Variables

Immunotherapy targeting the PD-1-PD-L1 axis yielded good results in treating different immunologically ''hot'' tumors. A phase II study revealed good therapeutic activity of pembrolizumab in selected prostatic carcinoma (PC)-patients. We performed a systematic literature review (PRISMA guidelines), which analyzes the immunohistochemical expression of PD-L1 in human PC samples and highlights the pre-analytical and interpretation variables. Interestingly, 29% acinar PCs, 7% ductal PCs, and 46% neuroendocrine carcinomas/tumors were PD-L1+ on immunohistochemistry. Different scoring methods or cut-off criteria were applied on variable specimen-types, evaluating tumors showing different clinic-pathologic features. The positivity rate of different PD-L1 antibody clones in tumor cells ranged from 3% (SP142) to 50% (ABM4E54), excluding the single case tested for RM-320. The most tested clone was E1L3N, followed by 22C3 (most used for pembrolizumab eligibility), SP263, SP142, and 28-8, which gave the positivity rates of 35%, 11-41% (depending on different scoring systems), 6%, 3%, and 15%, respectively. Other clones were tested in <200 cases. The PD-L1 positivity rate was usually higher in tumors than benign tissues. It was higher in non-tissue microarray specimens (41-50% vs. 15%), as PC cells frequently showed heterogenous or focal PD-L1-staining. PD-L1 was expressed by immune or stromal cells in 12% and 69% cases, respectively. Tumor heterogeneity, inter-institutional preanalytics, and inter-observer interpretation variability may account for result biases.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 4: Experimental Treatments in Pre-Clinical Studies (Cell Lines and Mouse Models)

In prostate cancer (PC), the PD-1/PD-L1 axis regulates various signaling pathways and it is influenced by extracellular factors. Pre-clinical experimental studies investigating the effects of various treatments (alone or combined) may discover how to overcome the immunotherapy-resistance in PC-patients. We performed a systematic literature review (PRISMA guidelines) to delineate the landscape of pre-clinical studies (including cell lines and mouse models) that tested treatments with effects on PD-L1 signaling in PC. NF-kB, MEK, JAK, or STAT inhibitors on human/mouse, primary/metastatic PC-cell lines variably down-modulated PD-L1-expression, reducing chemoresistance and tumor cell migration. If PC-cells were co-cultured with NK, CD8+ T-cells or CAR-T cells, the immune cell cytotoxicity increased when PD-L1 was downregulated (opposite effects for PD-L1 upregulation). In mouse models, radiotherapy, CDK4/6-inhibitors, and RB deletion induced PD-L1-upregulation, causing PC-immune-evasion. Epigenetic drugs may reduce PD-L1 expression. In some PC experimental models, blocking only the PD-1/PD-L1 pathway had limited efficacy in reducing the tumor growth. Anti-tumor effects could be increased by combining the PD-1/PD-L1 blockade with other approaches (inhibitors of tyrosine kinase, PI3K/mTOR or JAK/STAT3 pathways, p300/CBP; anti-RANKL and/or anti-CTLA-4 antibodies; cytokines; nitroxoline; DNA/cell vaccines; radiotherapy/Radium-223).

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 2: Clinic-Pathologic Correlations

Many studies have investigated the potential prognostic and predictive role of PD-L1 in prostatic carcinoma (PC). We performed a systematic literature review (PRISMA guidelines) to critically evaluate human tissue-based studies (immunohistochemistry, molecular analysis, etc.), experimental research (cell lines, mouse models), and clinical trials. Despite some controversial results and study limitations, PD-L1 expression by tumor cells may be related to clinic-pathologic features of adverse outcome, including advanced tumor stage (high pT, presence of lymph node, and distant metastases), positivity of surgical margins, high Grade Group, and castration resistance. Different PD-L1 positivity rates may be observed in matched primary PCs and various metastatic sites of the same patients. Over-fixation, type/duration of decalcification, and PD-L1 antibody clone may influence the immunohistochemical analysis of PD-L1 on bone metastases. PD-L1 seemed expressed more frequently by castration-resistant PCs (49%) as compared to hormone-sensitive PCs (17%). Some series found that PD-L1 positivity was associated with decreased time to castration resistance. Treatment with ipilimumab, cyclophosphamide/GVAX/degarelix, or degarelix alone may increase PD-L1 expression. Correlation of PD-L1 positivity with overall survival and outcomes related to tumor recurrence were rarely investigated; the few analyzed series produced conflicting results and sometimes showed limitations. Further studies are required. The testing and scoring of PD-L1 should be standardized.

ATM/NEMO signaling modulates the expression of PD-L1 following docetaxel chemotherapy in prostate cancer

Background

The efficacy of docetaxel-based chemotherapy is limited by the development of drug resistance. Recent studies demonstrated the efficacy of anti-programmed death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) immunotherapies in metastatic prostate cancer. The ataxia telangiectasia mutation (ATM) protein plays a crucial role in maintaining genome stability and function of mitosis. Here, we aimed to determine whether PD-1/PD-L1 signaling contributes to the resistance to DTX and to elucidate the mechanism underlying DTX-induced PD-L1 expression.

Methods

In this retrospective study, PD-L1 expression was analyzed in 33 tumor tissue samples from prostate cancer patients. Prostate cell lines were used to perform functional assays and examine underlying mechanisms in vitro. A fully mouse prostate cancer model and a humanized chimeric mouse bearing human prostate tumors and peripheral blood mononuclear cells were used for in vivo assays.

Results

We have shown that DTX, a chemotherapeutic drug which causing microtubule interference, could significantly induce the expression of PD-L1 in prostate cancer cells. This effect is blocked by the inhibition of ATM, suggesting that it plays an essential role in PD-L1 expression upregulated by DTX. Mechanistic studies have shown that ATM activity in cancer cells enhances the stability of the NF-κB essential modulator (NEMO), which leading to an increase in the NF-κB activity and PD-L1 expression. Using the mouse model, it was further demonstrated that a combination of ATM and NEMO inhibitors along with DTX augmented the antitumor efficacy of chemotherapy, which are comparable to that of PD-L1 antibody.

Conclusions

Our findings have revealed that a previously unrecognized ATM-NEMO signaling which induced by DTX is capable of suppressing tumor immunity by activating the expression of PD-L1, suggesting that the ATM-NEMO-NF-κB axis can be exploited to restore the immune balance and overcome cancer resistance triggered by DTX.

Graphic Abstract: supplementary file 1

The immune checkpoint regulator PD-L1 expression are associated with clinical progression in prostate cancer

Background

The programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) have shown positive efficacy in several solid cancers due to their targeted antitumour effects. However, the frequency and clinical implication value in prostate cancer still remain unclear.

Methods

The PD-1/PD-L1 expression was detected by immunohistochemical (IHC) analysis in 96 retrospectively collected cases of prostatic cancer and 44 controls of benign prostatic hyperplasia (BPH). Its correlation with clinicopathological features including age, PSA level, Gleason score, lymph node metastasis, clinical T stage and risk factor grade in prostate cancer was also assessed.

Results

The PD-L1-positive expression was significantly higher in cancer cases compared with benign tissues, whereas no difference in PD-1 positive expression was found. Moreover, the PD-L1 expression in tumour cells or lymphocytes was associated with Gleason score, but not related to age, preoperative PSA level, clinical T-stage, lymph node metastasis and grade of risk factors. In addition, no association between the positive expression of PD-1 and PD-L1 in tumour cells and lymphocytes was found.

Conclusions

The expression of PD-L1 not PD-1 is highly prevalent in prostate cancer. PD-L1 is closely related to Gleason score and may be a co-factor associated with the progression of prostate cancer.

A Subset of Localized Prostate Cancer Displays an Immunogenic Phenotype Associated with Losses of Key Tumor Suppressor Genes

PURPOSE

A subset of primary prostate cancer expresses programmed death-ligand 1 (PD-L1), but whether they have a unique tumor immune microenvironment or genomic features is unclear.

EXPERIMENTAL DESIGN

We selected PD-L1-positive high-grade and/or high-risk primary prostate cancer, characterized tumor-infiltrating lymphocytes with multiplex immunofluorescence, and identified genomic alterations in immunogenic and nonimmunogenic tumor foci.

RESULTS

One quarter of aggressive localized prostate cancer cases (29/115) had tumor PD-L1 expression more than 5%. This correlated with increased density of CD8⁺ T cells, a large fraction coexpressing PD-1, versus absent PD-1 expression on sparse CD8 T cells in unselected cases. Most CD8⁺PD-1⁺ cells did not express terminal exhaustion markers (TIM3 or LAG3), while a subset expressed TCF1. Consistent with these CD8⁺PD-1⁺TCF1⁺ cells being progenitors, they were found in antigen-presenting cell niches in close proximity to MHC-II⁺ cells. CD8 T-cell density in immunogenic prostate cancer and renal cell carcinoma (RCC) was nearly identical. Shallow RB1 and BRCA2 losses, and deep deletions of CHD1, were prevalent, the latter being strongly associated with a dendritic cell gene set in The Cancer Genome Atlas. Tumor mutation burden was variable; neither high microsatellite instability nor CDK12 alterations were present.

CONCLUSIONS

A subset of localized prostate cancer is immunogenic, manifested by PD-L1 expression and CD8⁺ T-cell content comparable with RCC. The CD8⁺ T cells include effector cells and exhausted progenitor cells, which may be expanded by immune checkpoint inhibitors (ICI). Genomic losses of RB1, BRCA2, and CHD1 may be drivers of this phenotype. These findings indicate that immunotherapies may be effective in biomarker-selected subpopulations of patients with localized prostate cancer.

Immune Checkpoint Inhibitors in Prostate Cancer

Simple Summary

Metastatic prostate cancer is an incurable disease with limited treatment options. Immunotherapy has demonstrated significant success in multiple cancer types but efforts to harness its benefit in prostate cancer have so far largely been unsuccessful. In this review, we analyze the preclinical rationale for the use of immunotherapy and underlying barriers preventing responses to it. We summarize clinical studies evaluating checkpoint inhibitors in prostate cancer. In the end, we review ongoing trials exploring combination immune checkpoint inhibitors in combination with other agents with the intent to modulate the immune system to improve treatment outcomes.

Abstract

Metastatic prostate cancer is a lethal disease with limited treatment options. Immune checkpoint inhibitors have dramatically changed the treatment landscape of multiple cancer types but have met with limited success in prostate cancer. In this review, we discuss the preclinical studies providing the rationale for the use of immunotherapy in prostate cancer and underlying biological barriers inhibiting their activity. We discuss the predictors of response to immunotherapy in prostate cancer. We summarize studies evaluating immune checkpoint inhibitors either as a single agent or in combination with other checkpoint inhibitors or with other agents such as inhibitors of androgen axis, poly ADP-ribose polymerase (PARP), radium-223, radiotherapy, cryotherapy, tumor vaccines, chemotherapy, tyrosine kinase inhibitors, and granulocyte-macrophage colony-stimulating factor. We thereafter review future directions including the combination of immune checkpoint blockade with inhibitors of adenosine axis, bispecific T cell engagers, PSMA directed therapies, adoptive T-cell therapy, and multiple other miscellaneous agents.

Treating Prostate Cancer by Antibody-Drug Conjugates

Prostate cancer is the most frequent malignancy in the worldwide male population; it is also one of the most common among all the leading cancer-related death causes. In the last two decades, the therapeutic scenario of metastatic castration-resistant prostate cancer has been enriched by the use of chemotherapy and androgen receptor signaling inhibitors (ARSI) and, more recently, by immunotherapy and poly(ADP–ribose) polymerase (PARP) inhibitors. At the same time, several trials have shown the survival benefits related to the administration of novel ARSIs among patients with non-castration-resistant metastatic disease along with nonmetastatic castration-resistant cancer too. Consequently, the therapeutic course of this malignancy has been radically expanded, ensuring survival benefits never seen before. Among the more recently emerging agents, the so-called “antibody–drug conjugates” (ADCs) are noteworthy because of their clinical practice changing outcomes obtained in the management of other malignancies (including breast cancer). The ADCs are novel compounds consisting of cytotoxic agents (also known as the payload) linked to specific antibodies able to recognize antigens expressed over cancer cells’ surfaces. As for prostate cancer, researchers are focusing on STEAP1, TROP2, PSMA, CD46 and B7-H3 as optimal antigens which may be targeted by ADCs. In this paper, we review the pivotal trials that have currently changed the therapeutic approach to prostate cancer, both in the nonmetastatic castration-resistant and metastatic settings. Therefore, we focus on recently published and ongoing trials designed to investigate the clinical activity of ADCs against prostate malignancy, characterizing these agents. Lastly, we briefly discuss some ADCs-related issues with corresponding strategies to overwhelm them, along with future perspectives for these promising novel compounds.

Critical review of Epstein-Barr virus microRNAs relation with EBV-associated gastric cancer

Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC) is regarded as the most prevalent malignant tumor triggered by EBV infection. In recent years, increasing attention has been considered to recognize more about the disease process's exact mechanisms. There is accumulating evidence that showing epigenetic modifications play critical roles in the EBVaGC pathogenesis. MicroRNAs (miRNAs), as critical epigenetic modulators, are single-strand short noncoding RNA (length ~ <200 bp), which regulate gene expression through binding to the 3'-untranslated region (3'-UTR) of target RNA transcripts and either degrade or repress their activities. In the latest research on EBV, it was found that this virus could encode miRNAs. Mechanistically, EBV-encoded miRNAs are involved in carcinogenesis and the progression of EBV-associated malignancies. Moreover, these miRNAs implicated in immune evasion, identification of pattern recognition receptors, regulation of lymphocyte activation and lethality, modulation of infected host cell antigen, maintain of EBV infection status, promotion of cell proliferation, invasion and migration, and reduction of apoptosis. As good news, not only has recent data demonstrated the crucial function of EBV-encoded miRNAs in the pathogenesis of EBVaGC, but it has also been revealed that aberrant expression of exosomal miRNAs in EBVaGC has made them biomarkers for detection of EBVaGC. Regarding these substantial characterizes, the critical role of EBV-encoded miRNAs has been a hot topic in research. In this review, we will focus on the multiple mechanisms involved in EBVaGC caused by EBV-encoded miRNAs and briefly discuss their potential application in the clinic as a diagnostic biomarker.

Immunotherapy and Immunotherapy Combinations in Metastatic Castration-Resistant Prostate Cancer

Although most prostate cancers are localized, and the majority are curable, recurrences occur in approximately 35% of men. Among patients with prostate-specific antigen (PSA) recurrence and PSA doubling time (PSADT) less than 15 months after radical prostatectomy, prostate cancer accounted for approximately 90% of the deaths by 15 years after recurrence. An immunosuppressive tumor microenvironment (TME) and impaired cellular immunity are likely largely responsible for the limited utility of checkpoint inhibitors (CPIs) in advanced prostate cancer compared with other tumor types. Thus, for immunologically "cold" malignancies such as prostate cancer, clinical trial development has pivoted towards novel approaches to enhance immune responses. Numerous clinical trials are currently evaluating combination immunomodulatory strategies incorporating vaccine-based therapies, checkpoint inhibitors, and chimeric antigen receptor (CAR) T cells. Other trials evaluate the efficacy and safety of these immunomodulatory agents' combinations with standard approaches such as androgen deprivation therapy (ADT), taxane-based chemotherapy, radiotherapy, and targeted therapies such as tyrosine kinase inhibitors (TKI) and poly ADP ribose polymerase (PARP) inhibitors. Here, we will review promising immunotherapies in development and ongoing trials for metastatic castration-resistant prostate cancer (mCRPC). These novel trials will build on past experiences and promise to usher a new era to treat patients with mCRPC.

The clinicopathological significance and prognostic value of programmed death-ligand 1 in prostate cancer: a meta-analysis of 3133 patients

Background: Programmed death-ligand 1 (PD-L1) is considered an adverse factor predicting poor prognosis in various cancers, but the significance of PD-L1 expression for the prognosis of prostate cancer (PCa) is still unclear. We aimed to investigate the clinicopathological significance and prognostic value of PD-L1 expression in PCa.

Methods: Studies were retrieved from PubMed, Web of Science, Cochrane Library and Embase before March 23, 2020. Odds ratios (ORs) and hazard ratios (HRs) with 95% confidence intervals (CIs) were obtained to assess the results. Begg’s test was applied to evaluate publication bias.

Results: Fourteen studies involving 3133 cases were analyzed. The pooled data showed that both PD-L1 protein expression and PD-L1 DNA methylation (mPD-L1) were negatively associated with biochemical recurrence-free survival, with HRs of 1.67 (95% CI = 1.38-2.06, p < 0.001) and 2.23 (95% CI = 1.51-3.29, p < 0.001), respectively. In addition, PD-L1 overexpression was significantly related to advanced tumor stage (OR = 1.40, 95% CI= 1.13-1.75, p = 0.003), positive surgical margin (OR = 1.36, 95% CI = 1.03-1.78, p = 0.028), higher Gleason score (OR = 1.81, 95% CI = 1.35-2.42, p < 0.001) and androgen receptor positivity (OR = 2.20, 95% CI = 1.61-3.01, p < 0.001), while no significant correlation with age (p = 0.122), preoperative PSA (p = 0.796) or nodal status (p = 0.113) was observed.

Conclusions: The study revealed that high expression of PD-L1 was related to unfavorable prognosis and advanced clinicopathological factors in PCa patients.

The Potential Role for Immunotherapy in Biochemically Recurrent Prostate Cancer

Biochemically recurrent prostate cancer represents a stage of prostate cancer where conventional (continued on next page) computed tomography and technetium Tc 99m bone scan imaging are unable to detect disease after curative intervention despite rising prostate-specific antigen. There is no clear standard of care and no systemic therapy has been shown to improve survival. Immunotherapy-based treatments potentially are attractive options relative to androgen deprivation therapy due to the generally more favorable side-effect profile. Biochemically recurrent prostate cancer patients have a low tumor burden and likely lymph node-based disease, which may make them more likely to respond to immunotherapy.

Immunotherapy in prostate cancer: current state and future perspectives

Metastatic castrate resistant prostate cancer (PCa) remains an incurable entity. In the era of immunotherapy, the complex PCa microenvironment poses a unique challenge to the successful application of this class of agents. However, in the last decade, a tremendous effort has been made to explore this field of therapeutics. In this review, the physiology of the cancer immunity cycle is highlighted in the context of the prostate tumor microenvironment, and the current evidence for use of various classes of immunotherapy agents including vaccines (dendritic cell based, viral vector based and DNA/mRNA based), immune checkpoint inhibitors, Chimeric antigen receptor T cell therapy, antibody-mediated radioimmunotherapy, antibody drug conjugates, and bispecific antibodies, is consolidated. Finally, the future directions for combinatorial approaches to combat PCa are discussed.

PD-L1 Expression in De Novo Metastatic Castration-sensitive Prostate Cancer

De novo metastatic castration-sensitive prostate cancer (mCSPC) is small subgroup of prostate cancer associated with poor prognosis. The aim of our study was to assess the expression of programmed death-ligand 1 (PD-L1) in tumor cells of de novo mCSPC patients. Patients referred to our institution from January 2007 to October 2017 with de novo mCSPC and available diagnostic tissue were included. We tested the PD-L1 pharmaDx qualitative immunohistochemical assay, a monoclonal rabbit anti-PD-L1, clone 28-8 intended for use in the detection of PD-L1 protein in formalin-fixed paraffin-embedded. Kaplan-Meier method was used to estimate survivals according to the expression of PD-L1. The study population included 32 de novo mCSPC patients, analyzed for PD-L1 expression using 2 cut-off values (1% and 5%) to define the positivity. Total of 46.9% of cases had tumor PD-L1 expression ≥1%, and 31.3% had expression ≥5%. No differences were found between the PD-L1 expression ≥1% and the involvement of liver, lung, and number of bone metastases, and the disease volume based on CHAARTED classification. PD-L1 tumors had higher incidence of Gleason score ≥8 compared with PD-L1 tumors (P=0.037), while the incidence of lymph node metastases was higher in PD-L1 tumors (P=0.044). No difference in the median overall survival (mOS) was observed between the PD-L1 population and the PD-L1 patients (43.8 vs. 29.6 mo; P=0.88). The tumor PD-L1 expression cannot be considered a prognostic factor for de novo mCSPC, even if its prognostic and predictive significance have to be thoroughly investigated to better define the selected group of prostate cancer patients that might benefit from checkpoint blockade immunotherapy.

p300/CBP inhibition enhances the efficacy of programmed death-ligand 1 blockade treatment in prostate cancer

Blockade of programmed death-ligand 1 (PD-L1) by therapeutic antibodies has shown to be a promising strategy in cancer therapy, yet clinical response in many types of cancer, including prostate cancer (PCa), is limited. Tumor cells secrete PD-L1 through exosomes or splice variants, which has been described as a new mechanism for the resistance to PD-L1 blockade therapy in multiple cancers, including PCa. This suggests that cutting off the secretion or expression of PD-L1 might improve the response rate of PD-L1 blockade therapy in PCa treatment. Here we report that p300/CBP inhibition by a small molecule p300/CBP inhibitor dramatically enhanced the efficacy of PD-L1 blockade treatment in a syngeneic model of PCa by blocking both the intrinsic and interferon gamma (IFN-γ)-induced PD-L1 expression. Mechanistically, p300/CBP could be recruited to the promoter of CD274 (encoding PD-L1) by the transcription factor IRF-1, which induced the acetylation of Histone H3 at CD274 promoter followed by the transcription of CD274. A485, a p300/CBP inhibitor, abrogated this process and cut off the secretion of exosomal PD-L1 by blocking the transcription of CD274, which combined with the anti-PD-L1 antibody to reactivate T cells function for tumor attack. This finding reports a new mechanism of how cancer cells regulate PD-L1 expression through epigenetic factors and provides a novel therapeutic approach to enhance the efficacy of immune checkpoint inhibitors treatment.

Immunotherapy in Metastatic Castration-Resistant Prostate Cancer: Past and Future Strategies for Optimization

PURPOSE OF REVIEW

To date, prostate cancer has been poorly responsive to immunotherapy. In the current review, we summarize and discuss the current literature on the use of vaccine therapy and checkpoint inhibitor immunotherapy in metastatic castration-resistant prostate cancer (mCRPC).

RECENT FINDINGS

Sipuleucel-T currently remains the only FDA-approved immunotherapeutic agent for prostate cancer. Single-agent phase 3 vaccine trials with GVAX and PROSTVAC have failed to demonstrate survival benefit to date. Clinical trials using combination approaches, including combination PROSTVAC along with a neoantigen vaccine and checkpoint inhibitor immunotherapy, are ongoing. Checkpoint inhibitor monotherapy clinical trials have demonstrated limited efficacy in advanced prostate cancer, and combination approaches and molecular patient selection are currently under investigation. The optimal use of vaccine therapy and checkpoint inhibitor immunotherapy in metastatic castration-resistant prostate cancer remains to be determined. Ongoing clinical trials will continue to inform future clinical practice.

PD-L1 expression and deficient mismatch repair in ductal adenocarcinoma of the prostate

This study aimed to investigate the expression of programmed death receptor ligand 1 (PD-L1) and deficient mismatch repair (dMMR) in ductal adenocarcinoma of the prostate. A tissue microarray of 32 ductal and 42 grade-matched acinar adenocarcinomas was used. Slides were stained for PD-L1, PD-L2, MMR proteins, CD4 and CD8. PD-L1 expression in tumor cells was only seen in 3% (1/34) of ductal and 5% (2/42) of acinar adenocarcinomas (p = 1.0), while PD-L1 expression in tumor-infiltrating immune cells was seen in 29% (10/34) of ductal and 14% (6/42) of acinar adenocarcinomas (p = 0.16). dMMR, as defined by loss of one or more of the MMR proteins, was identified in 5% (4/73) of cases, including 1 ductal and 3 acinar adenocarcinomas. There was a suggested association between infiltration of CD8+ lymphocytes and ductal subtype (p = 0.04) but not between CD4+ lymphocytes and tumor type (p = 0.28). The study shows that both dMMR and PD-L1 expression is uncommon in tumor cells of both ductal and acinar adenocarcinoma of the prostate, while PD-L1 expression in tumor-infiltrating immune cells is a more common finding.

Clinical implications of mismatch repair deficiency in prostate cancer

Immune checkpoint blockade holds great promise in the treatment of solid tumors but has not yet been approved for use in advanced prostate cancer. This is largely due to the relatively modest response in clinical trials in unselected patients and the lack of available biomarkers to predict clinical benefit. Germline and somatic mismatch repair (MMR) gene deficiencies are more prevalent than previously thought, especially in the metastatic setting, in patients with high-grade Gleason scores and in patients with variant histologies. An early signal suggests that patients with deficiency in MMR may respond well to immunotherapy. Both germline and somatic genetic testing are recommended, yet questions remain on the best modality for testing given lack of standardization and false-negative results in patients with complex genomic structural rearrangements. Expanded panels, such as next generation sequencing may increase the sensitivity without compromising specificity. Future studies are still needed to explore the relationships of hypermutation, tumor mutational burden, tumor-infiltrating lymphocytes and microsatellite instability-H status as predictors of response to immunotherapy. The drivers of variable response is largely unknown, and a more mature understanding of the mechanisms of resistance in deficiencies in MMR tumors may help to more precisely inform use of immunotherapy in prostate cancer.

The Immune Checkpoint Regulator PDL1 is an Independent Prognostic Biomarker for Biochemical Recurrence in Prostate Cancer Patients Following Adjuvant Hormonal Therapy

Background: The programmed death 1 (PD1)/programmed death ligand 1 (PDL1) targeted therapies have gained positive outcomes in several tumors, but the evidence of the expression and prognosis value of PD1/PDL1 in high risk prostate cancer was rare.

Methods: Immunohistochemical analysis of PDL1/PD1 expression by a validated antibody was performed in a retrospectively collected high risk prostate cancer cohort who received adjuvant hormonal therapy (AHT) after radical prostatectomy (RP). The association between PDL1/PD1 expression and prognosis was determined.

Results: In total, 127 patients were enrolled. 49.6% patients were considered PDL1-high expression while the PD1-positive expression proportion was 24.4%. High PDL1 and negative PD1 expression were significantly associated with lower prostate specific antigen (PSA) density (p=0.010 and p=0.033, respectively). Compared with the PDL1-low expression patients, the PDL1-high expression patients had significantly shorter time to PSA nadir (TTN) (P=0.001) and biochemical recurrence (BCR) (P=0.004). In Kaplan-Meier analysis, the PDL1-high expression group (p<0.0001) and the PDL1-high/PD1-negative expression group (p<0.0001) showed markedly lower BCR-free survival in localized disease. Univariate cause-specific Cox proportional hazard regression model concluded total PSA (p=0.047), PDL1-high-expression (p<0.001), PDL1-high/PD1-negative expression (p<0.001) were significant risk factors of shorter progression time to BCR in localized disease. PDL1-high-expression was the independent predictor of time to BCR in multiple Cox regression of all patients (Hazard ratio [HR]: 3.901; 95% Confidence interval [CI]: 1.287-11.824; p=0.016).

Conclusions: PDL1 expression is not only highly prevalent in high-risk prostate cancer, but is also an independent biomarker in the prognosis of high-risk prostate cancer received AHT after RP. PDL1/PD1 targeted therapy might be a potentially adjuvant treatment option for high-risk prostate cancer after RP.

The Clinicopathologic and Prognostic Significance of Programmed Cell Death Ligand 1 (PD-L1) Expression in Patients With Prostate Cancer: A Systematic Review and Meta-Analysis

Background: Programmed cell death ligand 1 (PD-L1) expression has been shown to correlate with poor prognosis in diverse human cancers. However, limited data exist on the prognostic and clinicopathologic significance of PD-L1 expression in prostate cancers (PCa), and the curative effect of anti-PD-1/PD-L1 therapy remains controversial. In this systematic review and meta-analysis, we aimed to evaluate the prognostic and clinicopathologic value of PD-L1 in PCa. Methods: We performed a systematic literature search in the PubMed, Cochrane Library, EMBASE, Web of Science, and SCOPUS databases up to July 21st, 2018. Pooled prevalence of PD-L1 in PCa was calculated using Freeman-Tukey double arcsine transformation by R software version 3.5.0. The data from the studies were examined by a meta-analysis using Review Manager software 5.3 to calculate pooled hazard ratios (HRs) and pooled odds ratios (ORs) with 95% confidence intervals (CIs) to estimate the prognostic and clinicopathologic value of PD-L1 in PCa. Heterogeneity was tested by the Chi-squared test and I ² statistic. Results: Five studies with 2,272 patients were included in this meta-analysis. The pooled prevalence of PD-L1 in PCa was 35% (95% CI 0.32 to 0.37). Both PD-L1 expression (HR = 1.78; 95% CI 1.39 to 2.27; p < 0.00001) and PD-L1 DNA methylation (HR = 2.23; 95% CI 1.51 to 3.29; p < 0.0001) were significantly associated with poor biochemical recurrence-free survival (BCR-FS). PD-L1 tended to have high expression levels in high Gleason score cases (OR = 1.54; 95% CI, 1.17 to 2.03; P = 0.002) and androgen receptor-positive cases (OR = 2.42, 95% CI 1.31 to 4.50; P = 0.005). However, PD-L1 had relatively weak correlation with age, pathologic stage, lymph node metastasis and preoperative PSA level. Conclusions: This meta-analysis confirms the negative prognostic significance of PD-L1 expression and mPD-L1 in PCa patients. Additionally, PD-L1 has a statistically significant correlation with Gleason score and androgen receptor status, while the correlations with age, pathologic stage, lymph node metastasis, and preoperative PSA level were not statistically significant. However, the number of included studies is too small to make the conclusions more convincing, so more retrospective large-cohort studies are expected for the further confirmation of these findings.

Expression of PD-L1 in tumor-associated nerves correlates with reduced CD8+ tumor-associated lymphocytes and poor prognosis in prostate cancer

To investigate immune profile consisting of stromal PD-L1 expression, inhibitory or non-T-cell inflamed tumor microenvironment that may predict response to anti-PD-L1/PD-1 immunotherapy in prostate cancer, we validated the specificity of a PD-L1 monoclonal antibody (E1L3N) and identified PD-L1 specific expression in prostatic stromal nerve cells. PD-L1 expression was analyzed in 73 primary prostate cancers and 7 castration-resistant prostate cancers (CRPC) by immunohistochemistry (IHC) and resulting data from primary prostate cancers were correlated with tumor-associated lymphocytes (TALs), clinicopathological characteristics and clinical outcome. PD-L1 was expressed in the tumor cells in only one primary prostate cancer case and none of the CRPC. However, PD-L1 was frequently observed in the nerve branches in the tumor-associated stroma (69 of 73 cases, 94.5%), supported by colocalization with axonal marker PGP9.5. FoxP3-, CD3- and CD8-positive T lymphocytes were observed in 74.6% (47/63), 98.4% (62/63) and 100% (61/61) of the cases, respectively. The density of PD-L1⁺ tumor-associated nerves (TANs) was inversely correlated with that of CD8⁺ TALs. Higher density of PD-L1⁺ TANs was significantly associated with biochemical recurrence (BCR) in Kaplan-Meier survival analysis (p = 0.016). In both univariate and multivariate Cox analysis, the density of PD-L1⁺ TANs was independently prognostic of BCR. In conclusion, PD-L1 expression is rare in prostate tumor cells but prevalent in TANs and negatively correlated with CD8⁺ TALs. Neuro-immunological interaction may be a contribution to immune-suppressive microenvironment. Combinatorial treatment regimen designs to neural PD-L1 and TALs should be warranted in future clinical application of anti-PD-L1/PD-1 immunotherapy in prostate cancer.

Phosphorylated RB Promotes Cancer Immunity by Inhibiting NF-κB Activation and PD-L1 Expression

Aberrant expression of programmed death ligand-1 (PD-L1) in tumor cells promotes cancer progression by suppressing cancer immunity. The retinoblastoma protein RB is a tumor suppressor known to regulate the cell cycle, DNA damage response, and differentiation. Here, we demonstrate that RB interacts with nuclear factor κB (NF-κB) protein p65 and that their interaction is primarily dependent on CDK4/6-mediated serine-249/threonine-252 (S249/T252) phosphorylation of RB. RNA-seq analysis shows a subset of NF-κB pathway genes including PD-L1 are selectively upregulated by RB knockdown or CDK4/6 inhibitor. S249/T252-phosphorylated RB inversely correlates with PD-L1 expression in patient samples. Expression of a RB-derived S249/T252 phosphorylation-mimetic peptide suppresses radiotherapy-induced upregulation of PD-L1 and augments therapeutic efficacy of radiation in vivo. Our findings reveal a previously unrecognized tumor suppressor function of hyperphosphorylated RB in suppressing NF-κB activity and PD-L1 expression and suggest that the RB-NF-κB axis can be exploited to overcome cancer immune evasion triggered by conventional or targeted therapies.

Prostate cancer immunotherapy: the path forward

PURPOSE OF REVIEW

To provide an overview of current strategies being investigated in the development of immunotherapy in prostate cancer.

RECENT FINDINGS

Development of immunotherapy in prostate cancer actually began in 2010 with FDA approval of sipuleucel-T. Given that immune checkpoint inhibitor trials have either been negative at the phase III level or underwhelming in smaller studies, it is likely that combination strategies will be required to further maximize the impact immune-based therapies on the clinical course of the disease. Emerging data suggests the presence of multiple checkpoint inhibitors in the prostate cancer tumor microenvironment highlighting the need for combination immunotherapy platforms that would potentially include androgen deprivation, chemotherapy, or radiation.

SUMMARY

Preclinical and clinical data support immune-based combinations in prostate cancer and several trials are underway to better define the future of immunotherapy in prostate cancer.

PD-1/PD-L1 pathway inhibitors in advanced prostate cancer

INTRODUCTION

Pharmacological inhibition of immune checkpoint receptors or their ligands represents a transformative breakthrough in the management of multiple cancers. However, immune checkpoint inhibitors have yet to be FDA-approved for the management of metastatic prostate cancer (PCa), the commonest non-cutaneous malignancy in men. Areas covered: We review our current understanding of the PD-1/PD-L1 pathway in cancer, the use of anti-PD-1/PD-L1 therapeutics in PCa, and potential subgroups of PCa patients who may derive the greatest benefit from these agents (such as men with tumors that have expression of PD-L1 and/or high mutational load). We also review the prior and current clinical trials evaluating the blockade of PD-1/PD-L1 in PCa, highlighting some of the key ongoing studies of greatest relevance to the field. Expert commentary: Clinical trials investigating PD-1/PD-L1 inhibitors should be encouraged in patients with PCa. While it is unlikely that immune checkpoint monotherapies will produce long-lasting responses in a substantial proportion of patients, there is early evidence of activity in some patient subsets. These subgroups may include those with high PD-L1 expression, those with hypermutated or microsatellite-unstable tumors, and those enriched for germline and/or somatic DNA-repair gene mutations (e.g. intraductal/ductal histology, primary Gleason pattern 5, and perhaps AR-V7-positive tumors).

The prognostic role of immune checkpoint markers programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) in a large, multicenter prostate cancer cohort

Programmed cell death protein 1 (PD-1) and its ligand Programmed death ligand 1 (PD-L1) have gained massive attention in cancer research due to recent availability and their targeted antitumor effects. Their role in prostate cancer is still undetermined. We constructed tissue microarrays from prostatectomy specimens from 535 prostate cancer patients. Following validation of antibodies, immunohistochemistry was used to evaluate the expression of PD-1 in lymphocytes and PD-L1 in epithelial and stromal cells of primary tumors. PD-L1 expression was commonly seen in tumor epithelial cells (92% of cases). Univariate survival analysis revealed a positive association between a high density of PD-1+ lymphocytes and worse clinical failure-free survival, limited to a trend (p = 0.084). In subgroups known to indicate unfavorable prostate cancer prognosis (Gleason grade 9, age < 65, preoperative PSA > 10, pT3) patients with high density of PD-1+ lymphocytes had a significantly higher risk of clinical failure (p = < 0.001, p = 0.025, p = 0.039 and p = 0.011, respectively). In the multivariate analysis, high density of PD-1+ lymphocytes was a significant negative independent prognostic factor for clinical failure-free survival (HR = 2.48, CI 95% 1.12-5.48, p = 0.025).

Nonsmall cell lung cancer from HIV-infected patients expressed programmed cell death-ligand 1 with marked inflammatory infiltrates

OBJECTIVE

Immunotherapies targeting the programmed cell death-1 (PD-1)/PD-ligand 1 (PD-L1) checkpoint improved prognosis in lung cancer. PD-1/PD-L1 status, however, has not been investigated in human immunodeficiency virus (HIV)-positive patients. This study assessed PD-L1 status and tumor immune-cell infiltration in nonsmall cell lung cancer (NSCLC) in HIV patients.

METHODS

Consecutive HIV patients treated between 1996 and 2014 were enrolled. PD-L1 tumor expression was assessed using immunohistochemistry with two antibodies (clones 5H1 and E1L3N), and tumor immune-cell infiltration with CD3, CD4, CD8, CD20, CD163, and MPO. PD-L1 expression and immune infiltration results were compared with those of 54 NSCLCs from unknown HIV status patients.

RESULTS

Thirty-four HIV-positive patients were evaluated: predominantly men (88.2%) (median age: 51.1 years) presenting stage IV (38.2%) adenocarcinomas (76.5%). The median blood CD4 count was 480 cells/μL (86-1120) and 64% exhibited undetectable viral load. The PD-L1 score (percentage of positive cells × intensity) was higher in HIV-positive than HIV-undetermined patients with the E1L3N clone [median (range) 0 (0-150) versus 0 (0-26.7), P = 0.047], yet not with the 5H1 clone [0 (0-120) versus 0 (0-26.7) P = 0.07, respectively]. PD-L1 expression frequency did not differ between both cohorts (18.7 versus 9.3% using E1L3N and 10 versus 5.6% using 5H1 clone, respectively). There were significantly greater cytotoxic T-cell (P < 0.001), B-lymphocyte (P = 0.005), and activated macrophage (P < 0.001) infiltrations in the HIV-positive patients, but no differences for CD4 T cells.

CONCLUSION

Tumors in HIV-positive patients seem to express higher PD-L1 levels with increased immune infiltration, supporting their inclusion in clinical trials assessing immune checkpoint inhibitors.

Comprehensive immunohistochemical analysis of PD-L1 shows scarce expression in castration-resistant prostate cancer

BACKGROUND

We aimed to analyze the frequency and distribution of PD-L1 expression in specimens from prostate cancer (PC) patients using two different anti-PD-L1 antibodies (E1L3N, SP263).

MATERIALS AND METHODS

PD-L1 immunohistochemistry was performed in a tissue microarray consisting of 82 castration-resistant prostate cancer (CRPC) specimens, 70 benign prostate hyperplasia (BPH) specimens, 96 localized PC cases, and 3 PC cell lines, using two different antibodies (clones E1L3N, and SP263). Staining images for CD4, CD8, PD-L1, and PanCK of a single PD-L1 positive case were compared, using a newly developed dot-wise correlation method for digital images to objectively test for co-expression.

RESULTS

Depending on the antibody used, in tumor cells (TC) only five (E1L3N: 6%) and three (SP263: 3.7%) samples were positive. In infiltrating immune cells (IC) 12 (SP263: 14.6%) and 8 (E1L3N: 9.9%) specimens showed PD-L1 expression. Two PC cell lines (PC3, LnCaP) also displayed membranous immunoreactivity. All localized PCs or BPH samples tested were negative. Dot-wise digital correlation of expression patterns revealed a moderate positive correlation between PD-L1 and PanCK expression, whereas both PanCK and PD-L1 showed a weak negative Pearson correlation coefficient between CD4 and CD8.

CONCLUSIONS

PD-L1 was not expressed in localized PC or BPH, and was only found in a minority of CRPC tumors and infiltrating immune cells. Protein expression maps and systematic dot-wise comparison could be a useful objective way to describe the relationship between immuno- and tumor-related proteins in the future, without the need to develop multiplex staining methods.

Tumor infiltrating T lymphocytes expressing FoxP3, CCR7 or PD-1 predict the outcome of prostate cancer patients subjected to salvage radiotherapy after biochemical relapse

Tumor immunologic microenvironment is strongly involved in tumor progression and the presence of tumor infiltrating lymphocytes (TIL) with different phenotypes has been demonstrated to be of prognostic relevance in different malignancies. We investigated whether TIL infiltration of tumor tissues could also predict the outcome of prostate cancer patients. To this end, we carried out a retrospective analysis correlating the outcome of locally advanced prostate cancer patients undergone salvage radiotherapy upon relapse after radical surgery with the infiltration by different TIL populations. Twenty-two patients with resectable prostate cancer, with a mean age of 67 (+/-3.93) years, who received salvage radiotherapy with a mean of 69.66 (+/- 3.178) Gy in 8 weeks, between June 1999 and January 2009 and with a median follow up of 123 (+/- 55.82) months, were enrolled in this study. We evaluated, by immunohistochemistry, the intratumoral (^t) and peripheral stroma (^p) infiltration by CD45, CD3, CD4, CD8, CCR7, FoxP3 or PD-1-positive cells on tumor samples taken at the diagnosis (^d) and relapse times (^R). We correlated these variables with patients' biochemical progression free survival (bPFS), post-radiotherapy progression free survival (PFS), and overall survival (OS). Substantial changes in the rate of TIL subsets were found between the first and the second biopsy with progressive increase in CD4, CCR7, FoxP3, PD-1⁺ cells. Our analysis revealed that higher CD8^p,R+ and lower PD-1^R+ TIL scores correlated to a longer bPFS. Higher CD8^p,R+ and CCR7^t,R+ TIL scores and lower CD45^p,R+ and FoxP3^p,R+ TIL scores correlated to a prolonged PFS and OS. These results suggest that the immunological microenvironment of primary tumor is strictly correlated with patient outcome and provide the rationale for immunological treatment of prostate cancer.

Expression of PD-L1 in Hormone-naïve and Treated Prostate Cancer Patients Receiving Neoadjuvant Abiraterone Acetate plus Prednisone and Leuprolide

Purpose: Programmed cell death ligand-1 (PD-L1)/programmed cell death-1 (PD-1) blockade has been unsuccessful in prostate cancer, with poor immunogenicity and subsequent low PD-L1 expression in prostate cancer being proposed as an explanation. However, recent studies indicate that a subset of prostate cancer may express significant levels of PD-L1. Furthermore, the androgen antagonist enzalutamide has been shown to upregulate PD-L1 expression in prostate cancer preclinical models. In this study, we evaluated the effect of neoadjuvant androgen deprivation therapy with abiraterone acetate plus prednisone and leuprolide (Neo-AAPL) on PD-L1 expression in prostate cancer.Experimental Design: Radical prostatectomy (RP) tissues were collected from 44 patients with intermediate- to high-risk prostate cancer who underwent RP after Neo-AAPL treatment. Untreated prostate cancer tissues were collected from 130 patients, including 44 matched controls for the Neo-AAPL cases. Tumor PD-L1 expression was detected by IHC using validated anti-PD-L1 antibodies. Tumor-infiltrating CD8⁺ cells were analyzed in trial cases and matched controls. Expression of DNA mismatch repair genes was examined in PD-L1-positive tumors.Results: Neo-AAPL-treated tumors showed a trend toward decreased PD-L1 positivity compared with matched controls (7% vs. 21% having ≥1% positive tumor cells; P = 0.062). Treated tumors also harbored significantly fewer tumor-infiltrating CD8⁺ cells (P = 0.029). In 130 untreated prostate cancers, African American ethnicity, elevated serum PSA, and small prostate independently predicted tumor PD-L1 positivity. Loss of MSH2 expression was observed in 1 of 21 PD-L1-positive tumors.Conclusions: A subset of prostate cancer expresses PD-L1, which is not increased by Neo-AAPL treatment, indicating that combining Neo-AAPL treatment with PD-L1/PD-1 blockade may not be synergistic. Clin Cancer Res; 23(22); 6812-22. ©2017 AACR.

Sensitive detection of PD-L1 expression on circulating epithelial tumor cells (CETCs) could be a potential biomarker to select patients for treatment with PD-1/PD-L1 inhibitors in early and metastatic solid tumors

BACKGROUND

The current cancer research strongly focuses on immune therapies, where the PD-1, with its ligands plays an important role. It is known that PD-L1 is frequently up-regulated in a number of different cancers and the relevance of this pathway has been extensively studied and therapeutic approaches targeting PD-1 and PD-L1 have been developed. We used a non-invasive, real-time biopsy for determining PD-L1 and PD-L2 expression in CETCs of solid cancer patients.

METHODS

CETCs were determined from blood of 128 patients suffering from breast (72), prostate (27), colorectal (18) and lung (11) cancer. The number of vital CETCs and the expression of PD-L1 and PD-L2 were investigated using the maintrac^® method.

RESULTS

PD-L1 expressing CETCs were detected in 94.5% of breast, 100% of prostate, 95.4% of colorectal and 82% of lung cancer patients whereas only 75% of breast cancer patients had PD-L2 positive CETCs. In the PD-L1 and PD-L2 expressing patients the cell fraction of PD-L1 positive CETCs is significantly higher than the fraction of PD-L2 positive CETCs (54.6% vs. 28.7%; p<0.001). Breast cancer patients with metastatic disease had significantly more PD-L1 positive CETCs as compared to patients without metastasis (median 75% vs. 61.1%; p<0.05).

CONCLUSION

PD-L1 seems to be a major factor in immune evasion and is highly expressed on CETCs regardless of the type of cancer. Monitoring the frequency of PD-L1 positive CETCs could reflect individual patient's response for an anti-PD-1/PD-L1 therapy and may be a promising target of anticancer treatment.

Treatment strategies for DNA repair-deficient prostate cancer

INTRODUCTION

Common recurrent genetic alterations have been identified in prostate cancer through comprehensive sequencing efforts, and the prevalence of mutations in DNA repair pathway genes in patients with advanced and metastatic disease approaches 20-25%. Identification of these underlying DNA repair defects may present unique treatment opportunities for patients, both in terms of standard-of-care treatments and selected investigational agents. Areas covered: We review our current understanding of the genomic landscape of prostate cancer, with special attention to alterations in DNA repair pathway genes in metastatic castration-resistant disease. For patients with tumors deficient in homologous recombination repair, potential opportunities for treatment include platinum chemotherapy, poly(ADP) ribose polymerase (PARP) inhibitors, bipolar androgen therapy, and maybe immune checkpoint blockade therapy. In addition, tumors with mismatch repair defects (i.e. microsatellite instability) may be particularly susceptible to checkpoint blockade immunotherapy. Expert commentary: We anticipate that genomic profiling of tumors will become necessary to guide treatment of advanced prostate cancer in the coming years. Work is needed to define the optimal tissue to test, and to define the natural history of tumors with specific genetic defects. The prognostic and therapeutic importance of germline vs somatic DNA repair alterations, and mono-allelic vs bi-allelic inactivation, also remains unclear. Finally, optimal strategies to sequence or combine targeted agents for these patients with 'actionable' mutations are now needed.

Inflammatory cytokines IL-17 and TNF-α up-regulate PD-L1 expression in human prostate and colon cancer cells

Programmed cell death protein 1 (PD-1) acts on PD-1 ligands (PD-L1 and PD-L2) to suppress activation of cytotoxic T lymphocytes. Interleukin-17 (IL-17) and tumor necrosis factor-α (TNF-α) are co-expressed by T helper 17 (T_H17) cells in many tumors. The purpose of this study was to test if IL-17 and TNF-α may synergistically induce PD-L1 expression in human prostate cancer LNCaP and human colon cancer HCT116 cell lines. We found that IL-17 did not induce PD-L1 mRNA expression, but up-regulated PD-L1 protein expression in HCT116 and LNCaP cells. TNF-α induced PD-L1 mRNA and protein expression in both cell lines. Neither IL-17 nor TNF-α induced PD-L2 mRNA or protein expression. IL-17 and TNF-α acted individually rather than cooperatively in induction of PD-L1 expression. IL-17 and/or TNF-α activated AKT, nuclear factor-κB (NF-κB), and extracellular signal-regulated kinases 1/2 (ERK1/2) signaling pathways in HCT116 cells, whereas only NF-κB signaling was activated in LNCaP cells. NF-κB inhibitor could diminish PD-L1 protein expression induced by IL-17 and/or TNF-α in both HCT116 and LNCaP cell lines. ERK1/2 inhibitor could also reduce PD-L1 protein expression induced by IL-17 and/or TNF-α in HCT116 cells, while AKT inhibitor could abolish PD-L1 protein expression induced by IL-17 and/or TNF-α in LNCaP cells. These results suggest that IL-17 and TNF-α act individually rather than cooperatively through activation of NF-κB and ERK1/2 signaling to up-regulate PD-L1 expression in HCT116 cells, while the two inflammatory cytokines act through activation of NF-κB signaling, in the presence of AKT activity, to up-regulate PD-L1 expression in LNCaP cells.

The immune infiltrate in prostate, bladder and testicular tumors: An old friend for new challenges

In genito-urinary tumors immunotherapy has been administered for a long time: Calmette-Guèrin Bacillus as adjuvant treatment in high risk patients with non muscle invasive urothelial bladder cancer and interleukin-2 and interferon-α in metastatic kidney cancer. The vaccine Sipuleucel-T has been approved by United States Food and Drug Administration for the treatment of castration resistant prostate cancer patients with asymptomatic or minimally symptomatic disease, given the 22% reduction of mortality risk in this group. Recently immunotherapeutic agents targeting inhibitory immune checkpoint molecules lead to improved outcomes and lasting anti-tumor effects in a variety of hematological and solid malignancies, including urogenital tumors. The benefit from these treatments has been observed only in a proportion of subjects, raising a need in optimizing patients' selection for immune checkpoint blockade. The composition and activity of a pre-existing immune infiltrate may aid in identifying ideal candidates to immunotherapy, with possible implications for the clinical management of neoplastic diseases from earlier to later stages.

Immune phenotypes of prostate cancer cells: Evidence of epithelial immune cell-like transition?

Prostate cancers (PCa) have been reported to actively suppress antitumor immune responses by creating an immune-suppressive microenvironment. There is mounting evidence that PCas may undergo an ''Epithelial Immune Cell-like Transition'' (EIT) by expressing molecules conventionally associated with immune cells (e.g., a variety of cytokines/receptors, immune transcription factors, Ig motifs, and immune checkpoint molecules), which subsequently results in the suppression of anti-cancer immune activity within the tumor microenvironment. Recent progress within the field of immune therapy has underscored the importance of immune checkpoint molecules in cancer development, thus leading to the development of novel immunotherapeutic approaches. Here, we review the expression of select immune checkpoint molecules in PCa epithelial and associated immune cells, with particular emphasis on clinical data supporting the concept of an EIT-mediated phenotype in PCa. Furthermore, we summarize current advances in anti-immune checkpoint therapies, and provide perspectives on their potential applicability.