A Review of Preclinical Experiments Toward Targeting M2 Macrophages in Prostate Cancer

Sialic acid blockade inhibits the metastatic spread of prostate cancer to bone

BACKGROUND

Bone metastasis is a common consequence of advanced prostate cancer. Bisphosphonates can be used to manage symptoms, but there are currently no curative treatments available. Altered tumour cell glycosylation is a hallmark of cancer and is an important driver of a malignant phenotype. In prostate cancer, the sialyltransferase ST6GAL1 is upregulated, and studies show ST6GAL1-mediated aberrant sialylation of N-glycans promotes prostate tumour growth and disease progression.

METHODS

Here, we monitor ST6GAL1 in tumour and serum samples from men with aggressive prostate cancer and using in vitro and in vivo models we investigate the role of ST6GAL1 in prostate cancer bone metastasis.

FINDINGS

ST6GAL1 is upregulated in patients with prostate cancer with tumours that have spread to the bone and can promote prostate cancer bone metastasis in vivo. The mechanisms involved are multi-faceted and involve modification of the pre-metastatic niche towards bone resorption to promote the vicious cycle, promoting the development of M2 like macrophages, and the regulation of immunosuppressive sialoglycans. Furthermore, using syngeneic mouse models, we show that inhibiting sialylation can block the spread of prostate tumours to bone.

INTERPRETATION

Our study identifies an important role for ST6GAL1 and α2-6 sialylated N-glycans in prostate cancer bone metastasis, provides proof-of-concept data to show that inhibiting sialylation can suppress the spread of prostate tumours to bone, and highlights sialic acid blockade as an exciting new strategy to develop new therapies for patients with advanced prostate cancer.

FUNDING

Prostate Cancer Research and the Mark Foundation For Cancer Research, the Medical Research Council and Prostate Cancer UK.

Regulation of the tumor immune microenvironment by the Hippo Pathway: Implications for cancer immunotherapy

The tumor immune microenvironment (TIME) is a dynamic and complex ecosystem consisting of immune cells, stromal cells, and tumor cells. It plays a crucial role in shaping cancer progression and treatment outcomes. Notably, tumor-associated immune cells are key regulators within the TIME, influencing immune responses and therapeutic efficacy. The Hippo pathway is a critical signaling pathway involved in the TIME and cancer progression. In this review, we provide an overview of the Hippo pathway's role in the TIME, focusing on its interactions with immune cells and their implications in cancer biology and therapy. Specifically, we discuss the involvement of the Hippo pathway in regulating T-cell function, macrophage polarization, B-cell differentiation, MDSC activity, and dendritic cell-mediated immune responses. Furthermore, we explore its influence on PD-L1 expression in lymphocytes and its potential as a therapeutic target. While recent progress has been made in understanding the Hippo pathway's molecular mechanisms, challenges remain in deciphering its context-dependent effects in different cancers and identifying predictive biomarkers for targeted therapies. By elucidating the intricate crosstalk between the Hippo pathway and the TME, we aim to contribute to the development of innovative strategies for cancer treatment.

Immunotherapy in Prostate Cancer: State of Art and New Therapeutic Perspectives

Prostate cancer (PC) is the most common type of tumor in men. In the early stage of the disease, it is sensitive to androgen deprivation therapy. In patients with metastatic castration-sensitive prostate cancer (mHSPC), chemotherapy and second-generation androgen receptor therapy have led to increased survival. However, despite advances in the management of mHSPC, castration resistance is unavoidable and many patients develop metastatic castration-resistant disease (mCRPC). In the past few decades, immunotherapy has dramatically changed the oncology landscape and has increased the survival rate of many types of cancer. However, immunotherapy in prostate cancer has not yet given the revolutionary results it has in other types of tumors. Research into new treatments is very important for patients with mCRPC because of its poor prognosis. In this review, we focus on the reasons for the apparent intrinsic resistance of prostate cancer to immunotherapy, the possibilities for overcoming this resistance, and the clinical evidence and new therapeutic perspectives regarding immunotherapy in prostate cancer with a look toward the future.

Establishing a Proteomics-Based Signature of AKR1C3-Related Genes for Predicting the Prognosis of Prostate Cancer

Aldo-keto reductase family 1 member C3 (AKR1C3) plays an important role in prostate cancer (PCa) progression, particularly in castration-resistant prostate cancer (CRPC). It is necessary to establish a genetic signature associated with AKR1C3 that can be used to predict the prognosis of PCa patients and provide important information for clinical treatment decisions. AKR1C3-related genes were identified via label-free quantitative proteomics of the AKR1C3-overexpressing LNCaP cell line. A risk model was constructed through the analysis of clinical data, PPI, and Cox-selected risk genes. Cox regression analysis, Kaplan-Meier (K-M) curves, and receiver operating characteristic (ROC) curves were used to verify the accuracy of the model, and two external datasets were used to verify the reliability of the results. Subsequently, the tumor microenvironment and drug sensitivity were explored. Moreover, the roles of AKR1C3 in the progression of PCa were verified in LNCaP cells. MTT, colony formation, and EdU assays were conducted to explore cell proliferation and drug sensitivity to enzalutamide. Migration and invasion abilities were measured using wound-healing and transwell assays, and qPCR was used to assess the expression levels of AR target genes and EMT genes. CDC20, SRSF3, UQCRH, INCENP, TIMM10, TIMM13, POLR2L, and NDUFAB1 were identified as AKR1C3-associated risk genes. These risk genes, established using the prognostic model, can effectively predict the recurrence status, immune microenvironment, and drug sensitivity of PCa. Tumor-infiltrating lymphocytes and several immune checkpoints that promote cancer progression were higher in high-risk groups. Furthermore, there was a close correlation between the sensitivity of PCa patients to bicalutamide and docetaxel and the expression levels of the eight risk genes. Moreover, through in vitro experiments, Western blotting confirmed that AKR1C3 enhanced SRSF3, CDC20, and INCENP expression. We found that PCa cells with a high expression of AKR1C3 have high proliferation ability and high migration ability and were insensitive to enzalutamide. AKR1C3-associated genes had a significant role in the process of PCa, immune responses, and drug sensitivity and offer the potential for a novel model for prognostic prediction in PCa.

Dissecting the immune suppressive human prostate tumor microenvironment via integrated single-cell and spatial transcriptomic analyses

The treatment of low-risk primary prostate cancer entails active surveillance only, while high-risk disease requires multimodal treatment including surgery, radiation therapy, and hormonal therapy. Recurrence and development of metastatic disease remains a clinical problem, without a clear understanding of what drives immune escape and tumor progression. Here, we comprehensively describe the tumor microenvironment of localized prostate cancer in comparison with adjacent normal samples and healthy controls. Single-cell RNA sequencing and high-resolution spatial transcriptomic analyses reveal tumor context dependent changes in gene expression. Our data indicate that an immune suppressive tumor microenvironment associates with suppressive myeloid populations and exhausted T-cells, in addition to high stromal angiogenic activity. We infer cell-to-cell relationships from high throughput ligand-receptor interaction measurements within undissociated tissue sections. Our work thus provides a highly detailed and comprehensive resource of the prostate tumor microenvironment as well as tumor-stromal cell interactions.

Efficacy of immunotherapy in obese patients with cancer

Obesity is a condition of excessive fat tissue and high body mass index (BMI ≥30), which is increasing worldwide. Excess body weight is associated with poorer results in cancer treatments; however, recent studies emphasized that elevated BMI was associated with improved outcomes in cases treated by immune checkpoint inhibitor (ICI) therapies, which is called the obesity paradox. In this review, we discuss the correlation between obesity and cancer immunotherapy, especially ICIs, the underlying mechanisms, and the outcomes in different types of cancers. In addition, we describe the occurrence of immune-related adverse events (irAE) and the effect of gender in obese patients during immunotherapy using all relevant studies with available full texts.

Immunotherapy in Advanced Prostate Cancer-Light at the End of the Tunnel?

Immunotherapeutic treatment approaches are now an integral part of the treatment of many solid tumors. However, attempts to integrate immunotherapy into the treatment of prostate cancer have been disappointing so far. This is due to a highly immunosuppressive, "cold" tumor microenvironment, which is characterized, for example, by the absence of cytotoxic T cells, an increased number of myeloid-derived suppressor cells or regulatory T cells, a decreased number of tumor antigens, or a defect in antigen presentation. The consequence is a reduced efficacy of many established immunotherapeutic treatments such as checkpoint inhibitors. However, a growing understanding of the underlying mechanisms of tumor-immune system interactions raises hopes that immunotherapeutic strategies can be optimized in the future. The aim of this review is to provide an overview of the current status and future directions of immunotherapy development in prostate cancer. Background information on immune response and tumor microenvironment will help to better understand current therapeutic strategies under preclinical and clinical development.

Subversion of infiltrating prostate macrophages to a mixed immunosuppressive tumor-associated macrophage phenotype

Tumor-associated macrophages (TAMs) support tumor progression within the tumor microenvironment (TME). Many questions remain as to the origin, development, and function of TAMs within the prostate TME. Evaluation of TAMs in prostate cancer (PCa) patients identified the immunosuppressive TAM marker CD163 in adjacent normal epithelium as an independent predictor of metastases or PCa death. Flow cytometry analyses identified prostate TAMs as frequently expressing both proinflammatory M1 (CCR7+) and immunosuppressive M2 (CD163+) markers. In vitro, we demonstrate PCa cells similarly subvert human M1 macrophages toward a mixed M1/M2 macrophage phenotype favoring tumor growth. Further the cytokine milieu-induced transition between immunosuppressive M2 to proinflammatory M1 (M2→M1) macrophages is abrogated by the presence of PCa cells. RNA sequencing suggests alterations in chemokine expression in prostate TAMs due to the presence of PCa cells. Together, our results suggest that prostate TAMs originate from inflammatory infiltrating macrophages, which are then reprogrammed mainly by PCa cells, but also the cytokine milieu. A better understanding of this subversion of macrophages within the prostate may lead to novel treatment strategies.

M2 subtype tumor associated macrophages (M2-TAMs) infiltration predicts poor response rate of immune checkpoint inhibitors treatment for prostate cancer

BACKGROUND

Prostate cancer (PCa) is poor response to the immunotherapy for its high heterogeneity of immune microenvironment. In this study, we aim to introduce a new immune subtype for PCa involving M2 tumour associated macrophages (M2-TAMs).

METHODS

Three hundred and sixty-two PCa patients and matched normal prostate tissues were selected from the Cancer Genome Atlas and Gene Expression Omnibus databases. Patients' immune infiltration characters were then analyzed based on the gene expressions. The immune subtypes were identified by the method of unsupervised hierarchical clustering. Finally, the relationship between the M2-TAMs infiltration and anti-programmed death-ligand-1 (PD-L1) therapy was investigated in the IMvigor210 cohort.

RESULTS

PCa expressed lower immune-related genes levels compared with the adjacent normal tissues. Based on the proved immunosuppressive mechanisms in PCa, tumour patients were classified into three independent subclasses with high infiltrated cytolytic activity (CYT), M2-TAMs and regulatory T cell (Tregs), respectively. Among these subtypes, M2-TAMs infiltration subtype showed the worst clinicopathological features and prognosis compared with the other two subtypes. The results of the IMvigor210 cohort demonstrated poor response of anti-PD-L1 therapy for patients with high M2-TAMs infiltration.

CONCLUSION

Prostate tumours involved in significant immunosuppression, and high infiltration of M2-TAMs can be applied to predict the effect of anti-PD-L1 therapy.Key MessagesPCa patients can be classified into three immunotypes of high infiltrated CYT, M2-TAMS, and Tregs according to the immunosuppressive mechanisms.High M2-TAMs infiltration subtype reflected the worst clinical characters, immune infiltration, and lowest expression of immune checkpoint inhibitors among the three subclasses in PCa.High M2-TAMs infiltration predicts the low response rate of anti-PD-L1 therapy.

Evaluation of G2013 (α-L-guluronic acid) efficacy on PC-3 cells through inhibiting the expression of inflammatory factors

Given multiple treatment strategies for prostate cancer, its mortality rate is still high; therefore, novel treatment strategies seem necessary. G2013 or α-L-guluronic acid is a new patented drug with immunomodulatory and anti-inflammatory properties. This study aimed to evaluate the property of G2013 on inflammatory molecules involved in tumorigenesis of prostate cancer. MTT assay was used to assess the effect of the drug on the proliferation of PC-3 cells. Expression of interleukin 8 (IL-8), Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), myeloid differentiation factor 88 (MYD-88), cyclooxygenase 2 (COX-2), matrix metalloproteinase-2 (MMP-2), and MMP-9 genes were studied in the PC-3 cells treated with 25 (low dose) or 50 (high dose) µg/mL of G2013 for 24 h using quantitative real-time polymerase chain reaction (qRT-PCR) technique. Protein expression of NF-κB and protein activities of MMP-2 and MMP-9 were assayed using flow cytometry and gelatin zymography, respectively. The expression of COX-2 (p = 0.007 at low dose), MMP-2 (p = 0.023 at low dose, p = 0.002 at high dose), NF-κB (p = 0.004 at low dose) and IL-8 (p < 0.0001 in both doses) genes, NF-κB protein (p < 0.0001 in both doses), and MMP-2 activity (p < 0.0001 in both doses) were significantly reduced in the presence of G2013 as compared to the control group. Cancer cell proliferation was also inhibited under 10-500 µg/mL G2013 treatment. Our results revealed that G2013 has the potential to inhibit PC-3 cell proliferation and reduce the expression of tumour-promoting mediators, COX-2, MMP-2, NF-κB, and IL-8 involved in the progression and metastasis of prostate cancer.

Transcriptome sequencing and multi-plex imaging of prostate cancer microenvironment reveals a dominant role for monocytic cells in progression

BACKGROUND

Prostate cancer is caused by genomic aberrations in normal epithelial cells, however clinical translation of findings from analyses of cancer cells alone has been very limited. A deeper understanding of the tumour microenvironment is needed to identify the key drivers of disease progression and reveal novel therapeutic opportunities.

RESULTS

In this study, the experimental enrichment of selected cell-types, the development of a Bayesian inference model for continuous differential transcript abundance, and multiplex immunohistochemistry permitted us to define the transcriptional landscape of the prostate cancer microenvironment along the disease progression axis. An important role of monocytes and macrophages in prostate cancer progression and disease recurrence was uncovered, supported by both transcriptional landscape findings and by differential tissue composition analyses. These findings were corroborated and validated by spatial analyses at the single-cell level using multiplex immunohistochemistry.

CONCLUSIONS

This study advances our knowledge concerning the role of monocyte-derived recruitment in primary prostate cancer, and supports their key role in disease progression, patient survival and prostate microenvironment immune modulation.

The interplay of growth differentiation factor 15 (GDF15) expression and M2 macrophages during prostate carcinogenesis

M2 (tumor-supportive) macrophages may upregulate growth differentiation factor 15 (GDF15), which is highly expressed in prostate tumors, but the combined utility of these markers as prognostic biomarkers are unclear. We retrospectively studied 90 prostate cancer cases that underwent radical prostatectomy as their primary treatment and were followed for biochemical recurrence (BCR). These cases also had a benign prostate biopsy at least 1 year or more before their prostate cancer surgery. Using computer algorithms to analyze digitalized immunohistochemically stained slides, GDF15 expression and the presence of M2 macrophages based on the relative density of CD204- and CD68-positive macrophages were measured in prostate: (i) benign biopsy, (ii) cancer and (iii) tumor-adjacent benign (TAB) tissue. Both M2 macrophages (P = 0.0004) and GDF15 (P < 0.0001) showed significant inter-region expression differences. Based on a Cox proportional hazards model, GDF15 expression was not associated with BCR but, in men where GDF15 expression differences between cancer and TAB were highest, the risk of BCR was significantly reduced (hazard ratio = 0.26; 95% confidence interval = 0.09-0.94). In addition, cases with high levels of M2 macrophages in prostate cancer had almost a 5-fold increased risk of BCR (P = 0.01). Expression of GDF15 in prostate TAB was associated with M2 macrophage levels in both prostate cancer and TAB and appeared to moderate M2-macrophage-associated BCR risk. In summary, the relationship of GDF15 expression and CD204-positive M2 macrophage levels is different in a prostate tumor environment compared with an earlier benign biopsy and, collectively, these markers may predict aggressive disease.

SFMBT2-Mediated Infiltration of Preadipocytes and TAMs in Prostate Cancer

Infiltration of diverse cell types into tumor microenvironment plays a critical role in cancer progression including metastasis. We previously reported that SFMBT2 (Scm-like with four mbt domains 2) regulates the expression of matrix metalloproteinases (MMPs) and migration and invasion of cancer cells in prostate cancer. Here we investigated whether the down-regulation of SFMBT2 regulates the infiltration of preadipocytes and tumor-associated macrophages (TAMs) in prostate cancer. We found that the down-regulation of SFMBT2 promotes the infiltration of preadipocytes and TAMs through up-regulation of CXCL8, CCL2, CXCL10, and CCL20 expression in prostate cancer. Expression of CXCL8, CCL2, CXCL10, and CCL20 was also elevated in prostate cancer patients having a higher Gleason score (≥8), which had substantially lower SFMBT2 expression. We also found that the up-regulation of CXCL8, CCL2, CXCL10, and CCL20 expression is dependent on NF-κB activation in prostate cancer cells expressing a low level of SFMBT2. Moreover, increased IL-6 from infiltrated preadipocytes and TAMs promoted migration and invasion of prostate cancer cells expressing a low level of SFMBT2. Our study may suggest that SFMBT2 a critical regulator for the infiltration of preadipocytes and TAMs into the prostate tumor microenvironment. Thus, the regulation of SFMBT2 may provide a new therapeutic strategy to inhibit prostate cancer metastasis, and SFMBT2 could be used as a potential biomarker in prostate cancer metastasis.

A review of the effects of the anesthetic gas nitrous oxide on the immune system; a starting point for future experiences

Nitrous oxide is a common gas used as an anesthetic agent and analgesic medication in operating rooms. The gas inhibits vitamin B₁₂ dependent-methionine synthase, which converts L-homocysteine and 5-methyltetrahydrofolate to L-methionine and tetrahydrofolate, respectively, via a methylation process. The immune system has been frequently reported to be suppressed in anesthetized subjects during the postoperative period. Although previous reviews have focused on the pathophysiologic role of nitrous oxide, none of them has considered the harmful effects of nitrous oxide on the Defense system of the host. In this article, the authors review current studies on the effects of nitrous oxide on the immune system of both patients undergoing surgery and occupational exposure, as well as preclinical studies. Moreover, this paper opens a new horizon for future studies in the context of underlying mechanisms of nitrous oxide actions on the immune system.

A review on the role of M2 macrophages in bladder cancer; pathophysiology and targeting

Tumor-associated macrophages (TAMs) which are often referred to as immunosuppressive cells (M2 macrophage), constitute a subset of tumor microenvironment cells and affect tumor progression in solid tumors. Recently, these cells have gained remarkable importance as therapeutic candidates for solid tumors. In bladder cancer, major studies have focused on evaluating TAMs in response to Bacillus Calmette-Guerin (BCG) therapy. M2 macrophages may directly impact the BCG-induced immune responses against tumor in bladder cancer. They are the main inhibitors of the tumor microenvironment that promotes growth and metastasis of the tumor. However, the clinical significance of M2 macrophages in bladder cancer is controversial. In this review, we will discuss the clinical significance of M2 macrophages in prognosis of bladder cancer as well as worth of their potential targeting in bladder cancer treatment. In the following, we will introduce important factors resulting in M2 macrophage promotion and also experimental therapeutic agents that may cause the inhibition of bladder cancer tumor growth.