Biological and therapeutic advances in the pursuit of effective immunotherapy for prostate cancer

Randomized Phase II Study Evaluating the Addition of Pembrolizumab to Radium-223 in Metastatic Castration-resistant Prostate Cancer

The checkpoint immunotherapeutic pembrolizumab induces responses in a small minority of patients with metastatic castration-resistant prostate cancer (mCRPC). Radium-223 (R223) may increase immunogenicity of bone metastases and increase pembrolizumab (P) activity. In a randomized phase II study, we assessed the effect of R223+P compared with R223 on tumor immune infiltration, safety, and clinical outcomes in patients with mCRPC. The primary endpoint was differences in CD4+ and CD8+ T-cell infiltrate in 8-week versus baseline bone metastasis biopsies; secondary endpoints were safety, radiographic progression-free survival (rPFS), and overall survival (OS). Of the 42 treated patients (29 R223+P, 13 R223), 18 R223+P and 8 R223 patients had evaluable paired tumor biopsies. Median fold-change of CD4+ T cells was -0.7 (range: -9.3 to 4.7) with R223+P and 0.1 (-11.1 to 3.7) with R223 (P = 0.66); for CD8+ T cells, median fold-change was -0.6 (-7.4 to 5.3) with R223+P and -1.3 (-3.1 to 4.8) with R223 (P = 0.66). Median rPFS and OS was 6.1 (95% confidence interval: 2.7-11.0) and 16.9 months [12.7-not reached (NR)], respectively, with R223+P and 5.7 (2.6-NR) and 16.0 (9.0-NR), respectively, with R223. Although R223+P was well tolerated with no unexpected toxicity, the combination did not improve efficacy. High-dimensional flow cytometry demonstrated minimal immune modulation with R223, whereas R223+P induced CTLA-4 expression on circulating CD4+ T cells. Clinical responders possessed lower circulating frequencies of Ki67+ T and myeloid cells at baseline and higher circulating frequencies of TIM-3+ T and myeloid cells by week 9. Although R223+P did not induce T-cell infiltration into the tumor microenvironment, exhaustion of induced peripheral T-cell immune responses may dampen the combination's clinical activity.

Precision medicine for prostate cancer: An international perspective

Greater personalization of cancer medicine continues to shape therapy development and patient selection accordingly. The treatment of prostate cancer has evolved considerably since the discovery of androgen deprivation therapy. The comprehensive profiling of the prostate cancer genome has mapped the targetable molecular landscape of the disease and identified opportunities for the implementation of novel and combination therapies. In this review, we provide an overview of the molecular biology of prostate cancer and tools developed to aid prognostication and prediction of therapy benefit. Modern treatment of advanced prostate cancer is reviewed as a paradigm of increasing precision-informed approach to patient care, and must be considered on a global scale with respect to the state of science and care delivery.

Immune microenvironment infiltration landscape and immune-related subtypes in prostate cancer

Background

The tumor microenvironment (TME) primarily comprises cancer cells, cancer-infiltrating immune cells, and stromal cells. The tumor cells alter the TME by secreting signaling molecules to induce immune tolerance. The immune cell infiltrating the TME influences the prognosis of patients with cancers. However, immune cell infiltration (ICI) in the TME of patients with prostate cancer (PC) has not yet been studied.

Methods

In this study, we used Cell-type Identification by Estimating Relative Subsets of RNA Transcripts (CIBERSORT) and Estimation of Stromal and Immune cells in Malignant Tumors using Expression data (ESTIMATE) algorithms to identify three ICI clusters based on 1,099 genes associated with ICI in the TME. The patients were classified into three distinct ICI gene clusters based on overlapping differentially expressed genes in ICI clusters. Furthermore, the ICI scores were calculated using principal component analysis.

Results

The results revealed that patients with high ICI scores had poor prognoses and reduced expression of immune-checkpoint genes and immune-related genes. Furthermore, the transforming growth factor-beta (TGF-β) and WNT-β signaling pathways were enriched in the high ICI score subgroup, which suggests that suppression of T cells could contribute to poor prognosis of patients with PC. A positive correlation was observed between the high-ICI-score subgroup and the high tumor mutation burden (TMB) value. Patients with low ICI scores could benefit from immunotherapy, indicating that the ICI score could be used to predict the efficacy of immunotherapeutic response.

Conclusions

In summary, we provide a comprehensive overview of the landscape of ICI in PC, which could aid in designing the strategies for immunotherapy for patients with PC.

Knowledge mapping and current trends of immunotherapy for prostate cancer: A bibliometric study

BACKGROUND

Prostate cancer (PCa) is the second most common malignancy in men worldwide. Growing evidence substantiates the important role of immunotherapy in human tumors. Given that immunotherapy is often unsatisfactory on PCa, many studies have been conducted on PCa immunotherapy to improve treatment efficacy. However, no relevant bibliometric study of PCa immunotherapy has hitherto been reported. A bibliometric analysis was performed to evaluate the global scientific production of PCa immunotherapy research and characterize the development trends for future studies in this article.

METHODS

The publications related to PCa immunotherapy were extracted from the Web of Science Core Collection. The contribution and co-occurrence relationships of countries/regions, institutions, journals, references, authors, and keywords were assessed and visualized by VOSviewer and CiteSpace to identify research hotspots and potential future trends.

RESULTS

A total of 3,583 publications related to PCa immunotherapy from 1999 to 2021 were collected. The results of annual publications and citations exhibited a steady increase over the past 22 years. The National Cancer Institute in the USA published far more papers during the study than any institute. Accordingly, the USA had the most publications (n = 1,954, 54.54%). Gulley, James L. had the most number of published papers, and Small, Eric J. was the most co-cited authors in this field. Cancer Immunology Immunotherapy was the most productive journal, with 145 publications on PCa immunotherapy. Keyword cluster and keyword burst analyses showed that research in PCa immunotherapy shifted from "t cell infiltration" and "sipuleucel t" to "immune checkpoint inhibitor", "CTLA-4", and "PD-L1 expression".

CONCLUSION

PCa immunotherapy has attracted much attention, reflected by the increasing number of annual publications and citations. Much emphasis has been placed on exploring the complex immunogenicity and tumor microenvironment for PCa and identifying the patient population who can benefit from immunotherapy. Combining immune checkpoint inhibitors with other therapeutic options and cancer vaccines represents the future development trends in PCa immunotherapy.

Prostate cancer immunotherapy

INTRODUCTION

Medical treatment for prostate cancer (PC) targets hormonal pathways used by malignant cells. Research advances aided in gaining knowledge about implicated molecular pathways and opened the way for establishment of new types of therapies by modifying immunological mechanisms. The aim of this review is to present completed and ongoing research projects regarding PC immunotherapy.

AREAS COVERED

A literature search was conducted in PubMed/MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, and https://www.clinicaltrials.gov/ from inception until 07/2021, to identify completed or ongoing Phase III trials regarding several immunotherapies against PC. Studies on vaccine therapies, CTLA-4 inhibitors, PD-1/PD-L1 inhibitors, PARP inhibitors, PSMA-targeted therapies, and tyrosine kinase inhibitors were considered eligible.

EXPERT OPINION

Although many molecules are being tested against PC cells, only sipuleucel-T has gain approval in the USA. The main reason for this delay in establishing immunotherapy as a standard option for managing PC is the heterogeneity and tumor immune microenvironment complexities. Ipilimumab and olaparib were proved to prolong overall survival significantly against placebo, but a lot of research is going on to identify which patients and at what stage of disease will benefit the most before incorporating them in clinical practice. More recent options such as PSMA-targeted treatments are currently evaluated.

ARTICLE HIGHLIGHTS

Intense research performed on immunotherapy for prostate cancer.Vaccine therapy with sipuleucel-T, the only approved immunotherapy for prostate cancer.Ipilimumab shows survival benefits.Olaparib shows survival benefits.Findings should be confirmed on further trials to identify target population characteristics and proper disease stage.Immunotherapy is not yet a standard due to tumor environment complex interaction between immune system and malignant cells.