STEAP4 knockdown inhibits the proliferation of prostate cancer cells by activating the cGMP-PKG pathway under lipopolysaccharide-induced inflammatory microenvironment

PTTG1 promotes M2 macrophage polarization via the cGMP-PKG signaling pathway and facilitates EMT progression in human epithelial ovarian cancer cells

Epithelial Ovarian Cancer (EOC) is complex and heterogeneous, making accurate prognosis and treatment prediction difficult. New therapeutic targets and their mechanisms are urgently needed. This study explored the role of PTTG1 in ovarian cancer via the cGMP-PKG signaling pathway, focusing on its effects on M2 macrophage polarization and EMT progression in EOC cells. Using the GSE135886 database, we performed differential gene expression, pathway enrichment, and immune infiltration analyses to identify key targets influencing EMT and macrophage polarization. We then constructed PTTG1 knockdown and overexpression cell lines to assess the impact of PTTG1 on cell proliferation, migration, invasion, EMT, and macrophage polarization in vitro. Analysis revealed that differentially expressed genes were enriched in the cGMP-PKG pathway and correlated with M2 macrophages. PTTG1 overexpression in A2780 and SK-OV-3 ovarian cancer cells promoted proliferation, invasion, and migration, while enhancing sGC, PKG1, and PKG2 expression to activate the cGMP-PKG pathway and induce M2 macrophage polarization. PTTG1 knockdown produced opposite results, reinforcing our conclusions. This study uncovers a novel mechanism of PTTG1 in ovarian cancer development and suggests it as a potential therapeutic target.

STEAP Proteins: Roles in disease biology and potential for therapeutic intervention

Iron and copper are essential metal ions, and maintaining their metabolic balance is critical for organismal health. The Six-Transmembrane Epithelial Antigen of the Prostate (STEAP) protein family, comprising STEAP1, STEAP2, STEAP3, and STEAP4, plays a vital role in cellular metal homeostasis. These proteins are located on the cell membrane and are characterized by six transmembrane domains. With the exception of STEAP1, the STEAP proteins function as metal oxidoreductases due to their F420H2:NADP+ oxidoreductase (FNO)-like domain. However, STEAP1 contributes to metal metabolism through its heme group and interaction with other STEAP proteins. Beyond metal metabolism, STEAP proteins are involved in critical cellular processes, including the regulation of the cell cycle, proliferation, differentiation, and apoptosis. Notably, STEAP proteins are recognized as potential biomarkers and therapeutic targets in human cancers, particularly prostate cancer. This review outlines the structural features and functional roles of STEAP proteins in various diseases, including cancers, insulin resistance, non-alcoholic fatty liver disease (NAFLD), and benign prostatic hyperplasia, with a focus on their potential for therapeutic intervention.

STEAP4 facilitates growth, migration, and invasion of prostate carcinoma through upregulation of NOTCH4

STEAP4 manifested differential expression and aberrant methylation in prostate cancer (PCa). Therefore, this study proposed to explore the effect of STEAP4 on the PCa malignant phenotype in vivo and in vitro and the possible molecular mechanisms using RNA-seq. The expression of STEAP4 in PCa and its prognostic and diagnostic value was identified using bioinformatics. After exogenous modulation of STEAP4, the effect of STEAP4 on the malignant phenotype of PCa cells was examined using functional assays and nude mouse tumor models. The STEAP4-related differentially expressed genes (DEGs) and the hub genes were characterized using RNA-seq in conjunction with bioinformatics. STEAP4 exhibited high expression in PCa tissues from TCGA-PRAD and GEO datasets (GSE179321, GSE229904, and GSE237995), which predicted lower survival of patients. The STEAP4-associated nomogram model and diagnostic ROC curve had excellent predictive performance (AUC = 0.814). STEAP4 was overexpressed in PCa tissues and cells. Knockdown of STEAP4 effectively decreased the viability, number of invading cells, and wound healing of PCa cells and increased apoptosis. Overexpression of STEAP4 showed the opposite pattern. RNA-seq revealed that knockdown of STEAP4 resulted in 234 DEGs in PCa cells. FGF17, KCNQ2, PDGFRB, and NOTCH4 are hub genes in DEGs. Notably, NOTCH4 was likewise overexpressed in PCa tissues and cells and was regulated by STEAP4. In in vitro experiments, overexpression of NOTCH4 facilitated PCa cell proliferation, migration, and invasion, which was limited by knockdown of STEAP4. In in vivo experiments, overexpression of STEAP4 exacerbated PCa tumor burden, which was rescued by knockdown of NOTCH4. STEAP4 is a valid biomarker for predicting prognosis and diagnosis of PCa patients. STEAP4 contributes to PCa growth, migration, and invasion by upregulating NOTCH4.

Computational inference of co-regulatory modules from transcription factors, MicroRNAs, and their targets using CanMod2

Gene regulators such as Transcription Factors (TFs) and microRNAs (miRNAs) regulate genes at the transcriptional and post-transcriptional levels, respectively. There is a complex interplay of regulatory patterns of TFs and miRNAs. Some TFs and miRNAs regulate the activity of their target genes individually, some co-regulate the activity of the same set of genes, some TFs regulate miRNA activity, and some miRNAs regulate TFs. As dysregulation in gene regulation can lead to various diseases like cancer, it is a significant problem to find the interplay among TFs, miRNAs, and their target genes. Here, we propose a computational pipeline, CanMod2, which infers modules of TFs, miRNAs, and their co-regulatory targets that are involved in a common biological process. In this work, we have introduced several algorithmic enhancements to the earlier version of CanMod2. We applied CanMod2 to five cancer types and analyzed the inferred modules extensively. Our results show that the inferred modules were enriched in cancer-related biological processes and pathways. The hub regulators that occur in many modules were among cancer-related genes and miRNAs. The inferred regulator-target interactions were significantly enriched in ground truth interactions. CanMod2 source code and documentation are publicly available at https://github.com/bozdaglab/CanMod2 .

EDNRB negatively regulates glycolysis to exhibit anti-tumor functions in prostate cancer by cGMP/PKG pathway

Prostate cancer (PCa) is the most prevalent cancer in men and the leading cause of cancer-related mortality. Recent studies have highlighted the pivotal role of glycolysis in tumor progression. This study aimed to investigate the involvement of the EDNRB gene and its ligand endothelin 3 (EDN3) in glycolysis in PCa and to elucidate its underlying molecular mechanism. Quantitative reverse transcription PCR (RT-qPCR) and methylation-specific PCR (MSP) were used to probe EDNRB expression and methylation in PCa tissues. Cell proliferation and glycolysis in PCa cells were evaluated using Cell Counting Kit-8 (CCK-8), EDU staining, Seahorse assay, and biochemical kits to analyze the effects of EDN3/EDNRB. The underlying molecular mechanism was further explored through Western blotting. The in vivo effect of EDNRB on tumor growth was examined using a xenograft tumor model. Our findings revealed that EDNRB was hypermethylated and downregulated in PCa tissues and cell lines. Overexpression of EDNRB or EDN3 led to reduced cell proliferation and downregulation of glycolytic markers. EDNRB also decreased the extracellular acidification rate (ECAR) baseline and increased the oxygen consumption rate (OCR) baseline, indicating a shift away from glycolysis. Additionally, the anticancer effects of EDNRB or EDN3 was reversed upon inhibition of the cGMP/PKG pathway. In vivo, enhanced EDNRB expression significantly suppressed tumor growth. Therefore, EDNRB or EDN3 possess anticancer potential in PCa, primarily through the regulation of glycolysis via the cGMP/PKG pathway.

Diabetes-Mediated STEAP4 Enhances Retinal Oxidative Stress and Impacts the Development of Diabetic Retinopathy

Diabetic retinopathy is the most common diabetic complication of the microvasculature and one of the leading causes of acquired vision loss worldwide. Yet, the current treatments for this blinding disease are futile to many diabetics. Accordingly, new biomarkers and therapeutics for diabetic retinopathy are needed. We discovered that STEAP4 (Six-Transmembrane Epithelial Antigen of the Prostate 4) is significantly increased in peripheral blood mononuclear cells of diabetics. STEAP4 expression was gradiently increased from low levels in diabetics without retinopathy to successively higher levels in diabetics with more severe disease. Although the role of STEAP4 in the diabetic retina is unclear, these results provide strong evidence that this metabolic enzyme could be a potential biomarker for diabetic retinopathy progression. Thus, the central goal of this study was to evaluate if this potential biomarker impacts the intrinsic pathologies that lead to the development of diabetic retinopathy. In diabetic mice, STEAP4 was significantly increased and co-localized with 4-Hydroxy-2-nonenal in the Müller glia and photoreceptor layers of the retina. STEAP4 inhibition significantly decreased reactive oxygen species in murine photoreceptor cells, human Müller glia, and retinas of diabetic mice. Administering an intravitreal injection of anti-STEAP4 to diabetic mice halted Occludin degradation in the retinal vasculature. Similarly, anti-STEAP4 treatment of human retina endothelial cells halted cell death mediated by diabetic donor sera. Collectively, our findings provide strong evidence that STEAP4 impacts the intrinsic pathologies that initiate the development of diabetic retinopathy. Suggesting that STEAP4 could be a novel biomarker and clinically relevant therapeutic target for this diabetic complication and blinding disease.

Disulfidptosis-related gene signatures as prognostic biomarkers and predictors of immunotherapy response in HNSCC

Background

Disulfidptosis is a newly discovered form of cell death associated with tumorigenesis, particularly under oxidative stress and metabolic disorder conditions. Currently, the biological mechanisms of disulfidptosis-related genes (DRGs) in head and neck squamous cell carcinoma (HNSCC) remain unclear.

Methods

The study includes sections on methodologies, data sources, clinical data collection, subtype establishment, identification and analysis of differentially expressed genes, genetic variation, and the construction and validation of a DRG prognostic model. Various analyses are conducted, including the relationship between the risk scores model and clinicopathological features, immune status, immune checkpoints, tumor mutational burden (TMB), microsatellite instability (MSI), ESTIMATE, mRNAsi, and drug sensitivity. The study also covers single-cell analysis and DNA methylation analysis of DRGs, and the prediction of potential microRNA and long non-coding RNA target genes. Prognostic DRGs expression in HNSCC is validated through RT-qPCR and immunohistochemistry. The model's predictive capability is confirmed using external validation cohorts from GEO datasets and clinical tissue samples. The role of DSTN in HNSCC is further validated through gene knockout experiments.

Results

We identified four valuable genes (SLC3A2, NUBPL, ACTB, DSTN) and constructed a prognostic model, along with identifying two DRG-related subtypes. Analysis of the DRG risk score revealed that the low-risk group had a better prognosis compared to the high-risk group. Significant correlations were found between the DRG risk score and clinical features, immunotherapy response, drug sensitivity, and genes related to RNA epigenetic modifications. Low-risk HNSCC patients were identified as potential beneficiaries of immune checkpoint inhibitor (ICI) therapy. A regulatory axis involving DSTN, hsa-miR-181c-5p, LUCAT1, and IGFL2-AS1 was constructed for HNSCC. RT-qPCR and IHC data further validated the upregulation of prognostic DRGs in HNSCC. The prognostic model demonstrated excellent predictive performance for the prognosis of HNSCC patients. Additionally, DSTN was significantly overexpressed in tumor cells; its knockdown inhibited tumor cell proliferation, migration, and invasion.

Conclusion

The prognostic model effectively predicts HNSCC outcomes, with better prognosis in the low-risk group. DSTN upregulation promotes tumor growth, and its knockout inhibits proliferation, migration, and invasion.

Characterizing adipocytokine-related signatures for prognosis prediction in prostate cancer

Background

Prostate cancer (PCa) is a prevalent malignant tumor in males, with a significant incidence of biochemical recurrence (BCR) despite advancements in treatment. Adipose tissue surrounding the prostate, known as periprostatic adipose tissue (PPAT), contributes to PCa invasion through adipocytokine production. However, the relationship between adipocytokine-related genes and PCa prognosis remains understudied. This study was conducted to provide a theoretical basis and serve as a reference for the use of adipocytokine-related genes as prognostic markers in PCa.

Methods

Transcriptome and survival data of PCa patients from The Cancer Genome Atlas (TCGA) database were analyzed. Differential gene expression analysis was conducted using the DESeq2 and limma packages. Prognostic genes were identified through univariate Cox regression and least absolute shrinkage and selection operator (LASSO) regression. A prognostic model was developed and validated utilizing receiver operating characteristic (ROC) and Kaplan-Meier (K-M) curves. Assessments of immune cell infiltration and drug sensitivity were also carried out. Subsequently, the function of BNIP3L gene in PCa was verified.

Results

A total of 47 adipocytokine-related differentially expressed genes (DEGs) were identified. Five genes (PPARGC1A, APOE, BNIP3L, STEAP4, and C1QTNF3) were selected as prognostic markers. The prognostic model demonstrated significant predictive accuracy in both training and validation cohorts. Patients with higher risk scores exhibited poorer survival outcomes. Immune cell infiltration analysis revealed that the high-risk group had increased immune and ESTIMATE scores, while the low-risk group had higher tumor purity. In vitro experiments confirmed the suppressive effects of BNIP3L on PCa cell proliferation, migration, and invasion.

Conclusion

The prognostic model independently predicts the survival of patients with PCa, aiding in prognostic prediction and therapeutic efficacy. It expands the study of adipocytokine-related genes in PCa, presenting novel targets for treatment.

Anti-NSCLC role of SCN4B by negative regulation of the cGMP-PKG pathway: Integrated utilization of bioinformatics analysis and in vitro assay validation

Non-small cell lung cancer (NSCLC) is a malignant tumor with low overall cure and survival rates. Uncovering abnormally expressed genes is significantly important for developing novel targeted therapies in NSCLC. This study aimed to discover new differentially expressed genes (DEGs) of NSCLC. The DEGs of NSCLC were identified in eight data sets from Gene Expression Omnibus (GEO) database. The expression profiles and the prognostic significance of SCN4B in LUAD and LUSC were analyzed using GEPIA database. LinkedOmics was used to identify co-expressed genes with SCN4B, which were further subjected to KEGG pathway enrichment analysis. SCN4B-overexpressing plasmid (pcDNA/SCN4B) was transfected into A549 and NCI-H2170 cells to elevate the expression of SCN4B. MTT and TUNEL assays were performed to evaluate cell viability and apoptosis. Relying on the screened DEGs from GEO database, we identified that SCN4B was significantly downregulated in LUAD and LUSC. We confirmed the downregulation of SCN4B in NSCLC tissues using GEPIA database. SCN4B has a prognostic value in LUAD, but not LUSC. KEGG pathway enrichment analysis of SCN4B-related genes showed that cGMP-PKG signaling pathway might be involved in the role of SCN4B in NSCLC. Overexpression of SCN4B in A549 and NCI-H2170 cells inhibited the cell viability. Besides, SCN4B overexpression induced apoptosis of A549 and NCI-H2170 cells. SCN4B inhibited the expression of PKG1 and p-CREB in NSCLC cells. Moreover, the inhibitory effects of SCN4B on tumor malignancy were attenuated by the activator of PKG. In conclusion, integrated bioinformatical analysis proved that SCN4B was downregulated and had a prognostic significance in NSCLC. In vitro experimental studies demonstrated that SCN4B regulated NSCLC cells viability and apoptosis via inhibiting cGMP-PKG signaling pathway.

Correlation analysis of disulfidptosis-related gene signatures with clinical prognosis and immunotherapy response in sarcoma

Disulfidptosis, a newly discovered type of programmed cell death, could be a mechanism of cell death controlled by SLC7A11. This could be closely associated with tumor development and advancement. Nevertheless, the biological mechanism behind disulfidptosis-related genes (DRGs) in sarcoma (SARC) is uncertain. This study identified three valuable genes (SLC7A11, RPN1, GYS1) associated with disulfidptosis in sarcoma (SARC) and developed a prognostic model. The multiple databases and RT-qPCR data confirmed the upregulated expression of prognostic DRGs in SARC. The TCGA internal and ICGC external validation cohorts were utilized to validate the predictive model capacity. Our analysis of DRG riskscores revealed that the low-risk group exhibited a more favorable prognosis than the high-risk group. Furthermore, we observed a significant association between DRG riskscores and different clinical features, immune cell infiltration, immune therapeutic sensitivity, drug sensitivity, and RNA modification regulators. In addition, two external independent immunetherapy datasets and clinical tissue samples were collected, validating the value of the DRGs risk model in predicting immunotherapy response. Finally, the SLC7A11/hsa-miR-29c-3p/LINC00511, and RPN1/hsa-miR-143-3p/LINC00511 regulatory axes were constructed. This study provided DRG riskscore signatures to predict prognosis and response to immunotherapy in SARC, guiding personalized treatment decisions.

A novel prognostic signature and therapy guidance for hepatocellular carcinoma based on STEAP family

BACKGROUND

The six-transmembrane epithelial antigen of prostate (STEAP) family members are known to be involved in various tumor-related biological processes and showed its huge potential role in tumor immunotherapy.

METHODS

Biological differences were investigated through Gene set enrichment analysis (GSEA) and tumor microenvironment analysis by CIBERSORT. Tumor mutation burden (TMB), immunotherapy response and chemotherapeutic drugs sensitivity were estimated in R.

RESULTS

We established a prognostic signature with the formula: risk score = STEAP1 × 0.3994 + STEAP4 × (- 0.7596), which had a favorable concordance with the prediction. The high-risk group were enriched in cell cycle and RNA and protein synthesis related pathways, while the low-risk group were enriched in complement and metabolic related pathways. And the risk score was significantly correlated with immune cell infiltration. Most notably, the patients in the low-risk group were characterized with increased TMB and decreased tumor immune dysfunction and exclusion (TIDE) score, indicating that these patients showed better immune checkpoint blockade response. Meanwhile, we found the patients with high-risk were more sensitive to some drugs related to cell cycle and apoptosis.

CONCLUSIONS

The novel signature based on STEAPs may be effective indicators for predicting prognosis, and provides corresponding clinical treatment recommendations for HCC patients based on this classification.

EDNRB inhibits the growth and migration of prostate cancer cells by activating the cGMP-PKG pathway

Prostate cancer (PCa) represents a substantial global health concern and a prominent contributor to male cancer-related mortality. The aim of this study is to explore the role of B-type endothelin receptor (EDNRB) in PCa and evaluate its therapeutic potential. The investigation employed predictive methodologies encompassing data acquisition from the GEO and TCGA databases, gene screening, enrichment analysis, in vitro experiments involving PCR, Western blotting, wound healing, and Transwell assays, as well as animal experiments. Analysis revealed a significant downregulation of EDNRB expression in PCa cells. Overexpression of EDNRB demonstrated inhibitory effects on tumor cell growth, migration, and invasion, likely mediated through activation of the cGMP-Protein Kinase G pathway. In vivo experiments further confirmed the tumor-suppressive properties of EDNRB overexpression. These findings underscore the prospect of EDNRB as a therapeutic target for PCa, offering novel avenues for PCa treatment strategies.

Cucurbitacin C suppresses the progression of pancreatic ductal adenocarcinoma via inhibition of the cGMP-PKG-VASP axis

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most devastating diseases; it has a considerably poor prognosis and may become the second most lethal malignancy in the next 10 years. Chemotherapeutic resistance is common in PDAC; thus, it is necessary to exploit effective alternative drugs. In recent years, traditional folk medicines and their extracts have shown great potential in cancer treatment. The seed of Lagenaria siceraria (Molina) Standl. is a traditional medicine in Asia. Because of its analgesic effects and ability to reduce swelling, it is often used as an adjuvant treatment for abdominal tumors. Cucurbitacin compounds are extracts abundant in Lagenaria siceraria (Molina) Standl. Here, we found that cucurbitacin C (CuC), a member of the cucurbitacin family, has apparent anti-PDAC therapeutic properties. CuC decreased the viability and suppressed the proliferation of PDAC cells in a time- and dose-dependent manner. Further studies revealed that CuC inhibited cell migration and invasion by inhibiting epithelial-mesenchymal transition (EMT). In addition, G2/M arrest was induced, and the apoptotic pathway was activated. Transcriptomic and bioinformatic analyses showed that CuC inhibited the cGMP-PKG-VASP axis, increasing the content of cGMP to restore tumor characteristics. The antitumor activity of CuC in vivo was verified through animal experiments, and no obvious side effects were observed. Overall, our study indicates a candidate therapeutic compound for PDAC that is worthy of further development.

Pyrroline-5-carboxylate reductase 1 reprograms proline metabolism to drive breast cancer stemness under psychological stress

Cancer stem-like cells (CSCs) contribute to cancer metastasis, drug resistance and tumor relapse, yet how amino acid metabolism promotes CSC maintenance remains exclusive. Here, we identify that proline synthetase PYCR1 is critical for breast cancer stemness and tumor growth. Mechanistically, PYCR1-synthesized proline activates cGMP-PKG signaling to enhance cancer stem-like traits. Importantly, cGMP-PKG signaling mediates psychological stress-induced cancer stem-like phenotypes and tumorigenesis. Ablation of PYCR1 markedly reverses psychological stress-induced proline synthesis, cGMP-PKG signaling activation and cancer progression. Clinically, PYCR1 and cGMP-PKG signaling components are highly expressed in breast tumor specimens, conferring poor survival in breast cancer patients. Targeting proline metabolism or cGMP-PKG signaling pathway provides a potential therapeutic strategy for breast patients undergoing psychological stress. Collectively, our findings unveil that PYCR1-enhanced proline synthesis displays a critical role in maintaining breast cancer stemness.

ScRNA-seq revealed an immunosuppression state and tumor microenvironment heterogeneity related to lymph node metastasis in prostate cancer

BACKGROUND

Metastasis is a crucial aspect of disease progression leading to death in patients with prostate cancer (PCa). However, its mechanism remains unclear. We aimed to explore the mechanism of lymph node metastasis (LNM) by analyzing the heterogeneity of tumor microenvironment (TME) in PCa using scRNA-seq.

METHODS

A total of 32,766 cells were obtained from four PCa tissue samples for scRNA-seq, annotated, and grouped. InferCNV, GSVA, DEG functional enrichment analysis, trajectory analysis, intercellular network evaluation, and transcription factor analysis were carried out for each cell subgroup. Furthermore, validation experiments targeting luminal cell subgroups and CXCR4 + fibroblast subgroup were performed.

RESULTS

The results showed that only EEF2 + and FOLH1 + luminal subgroups were present in LNM, and they appeared at the initial stage of luminal cell differentiation, which were comfirmed by verification experiments. The MYC pathway was enriched in the EEF2 + and FOLH1 + luminal subgroups, and MYC was associated with PCa LNM. Moreover, MYC did not only promote the progression of PCa, but also led to immunosuppression in TME by regulating PDL1 and CD47. The proportion of CD8 + T cells in TME and among NK cells and monocytes was lower in LNM than in the primary lesion, while the opposite was true for Th and Treg cells. Furthermore, these immune cells in TME underwent transcriptional reprogramming, including CD8 + T subgroups of CCR7 + and IL7R+, as well as M2-like monocyte subgroups expressing tumor-associated signature genes, like CCR7, SGKI, and RPL31. Furthermore, STEAP4+, ADGRF5 + and CXCR4+, and SRGNC + fibroblast subgroups were closely related to tumor progression, tumor metabolism, and immunosuppression, indicating their contributions in PCa metastasis. Meanwhile, The presence of CXCR4 + Fibroblasts in PCa was confirmed by polychromatic immunofluorescence.

CONCLUSIONS

The significant heterogeneity of luminal, immune, and interstitial cells in PCa LNM may not only directly contribute to tumor progression, but also indirectly result in TME immunosuppression, which may be the cause of metastasis in PCa and in which MYC played an role.

Six-Transmembrane Epithelial Antigen of Prostate 4: An Indicator of Prognosis and Tumor Immunity in Hepatocellular Carcinoma

Purpose

The six-transmembrane epithelial antigen of prostate 4 (STEAP4) has been linked to tumor progression via its involvement in inflammatory responses, oxidative stress, and metabolism. However, STEAP4 has rarely been studied in hepatocellular carcinoma (HCC). We explored STEAP4 expression associated with tumor prognosis to understand its role in tumor biology in HCC.

Patients and Methods

STEAP4 mRNA and protein expressions were primarily analyzed using bioinformatics tools based on The Cancer Genome Atlas database to understand the expression pattern, molecular mechanism, prognostic impact, and association with immune cell infiltration. We further investigated the association between STEAP4 protein expression and clinicopathological parameters and their predictive value in HCC patients using immunohistochemical staining of tissue microarrays.

Results

The expression of STEAP4 mRNA and protein in HCC tissues was significantly lower than in normal liver tissues. Reduced expression of STEAP4 was linked to advanced HCC stages, poor recurrence-free survival (RFS), and overall survival. Furthermore, reduced STEAP4 expression was a significant predictor of worse RFS in univariate and multivariate analyses in the immunohistochemical cohort. GO, KEGG, and GSEA analyses revealed that STEAP4 is related to numerous biological processes and pathways, including drug metabolism, DNA replication, RNA metabolism, and immune response. In terms of the immune system, the decreased level of STEAP4 was correlated with the immunosuppressive microenvironment.

Conclusion

Our data indicated that reduced STEAP4 expression was significantly associated with tumor aggressiveness and poor prognosis, possibly because of its link to various biological processes and induction of HCC immune evasion. Therefore, STEAP4 expression may serve as a potential prognostic biomarker for cancer progression and immunity, as well as a therapeutic target in HCC.

The Role of STAMP2 in Pathogenesis of Chronic Diseases Focusing on Nonalcoholic Fatty Liver Disease: A Review

Nonalcoholic fatty liver disease (NAFLD) is a major health issue. NAFLD can progress from simple hepatic steatosis to nonalcoholic steatohepatitis (NASH). NASH can progress to cirrhosis or hepatocellular carcinoma. Unfortunately, there is no currently approved pharmacologic therapy for NAFLD patients. The six transmembrane protein of prostate 2 (STAMP2), a metalloreductase involved in iron and copper homeostasis, is well known for its critical role in the coordination of glucose/lipid metabolism and inflammation in metabolic tissues. We previously demonstrated that hepatic STAMP2 could be a suitable therapeutic target for NAFLD. In this review, we discuss the emerging role of STAMP2 in the dysregulation of iron metabolism events leading to NAFLD and suggest therapeutic strategies targeting STAMP2.

STEAP1-4 (Six-Transmembrane Epithelial Antigen of the Prostate 1-4) and Their Clinical Implications for Prostate Cancer

Simple Summary

Despite recent therapeutic advances in the treatment of prostate cancer, metastatic castration-resistant prostate cancer continues to cause significant morbidity and mortality. New research into highly expressed proteins in metastatic castration-resistant prostate cancer shows that Six-Transmembrane Epithelial Antigen of the Prostate 1–4 (STEAP1–4) are significant drivers of prostate cancer aggressiveness and metastasis. STEAP1, in particular, is highly expressed on the plasma membrane of prostate cancer cells and has received significant attention as a potential therapeutic target. This review highlights what is known about STEAP1–4 and identifies knowledge gaps that require further research.

Abstract

Six-Transmembrane Epithelial Antigen of the Prostate 1–4 (STEAP1–4) compose a family of metalloproteinases involved in iron and copper homeostasis and other cellular processes. Thus far, five homologs are known: STEAP1, STEAP1B, STEAP2, STEAP3, and STEAP4. In prostate cancer, STEAP1, STEAP2, and STEAP4 are overexpressed, while STEAP3 expression is downregulated. Although the metalloreductase activities of STEAP1–4 are well documented, their other biological functions are not. Furthermore, the properties and expression levels of STEAP heterotrimers, homotrimers, heterodimers, and homodimers are not well understood. Nevertheless, studies over the last few decades have provided sufficient impetus to investigate STEAP1–4 as potential biomarkers and therapeutic targets for prostate cancer. In particular, STEAP1 is the target of many emerging immunotherapies. Herein, we give an overview of the structure, physiology, and pathophysiology of STEAP1–4 to provide context for past and current efforts to translate STEAP1–4 into the clinic.

Comprehensive Landscape of STEAP Family Members Expression in Human Cancers: Unraveling the Potential Usefulness in Clinical Practice Using Integrated Bioinformatics Analysis

The human Six-Transmembrane Epithelial Antigen of the Prostate (STEAP) family comprises STEAP1-4. Several studies have pointed out STEAP proteins as putative biomarkers, as well as therapeutic targets in several types of human cancers, particularly in prostate cancer. However, the relationships and significance of the expression pattern of STEAP1-4 in cancer cases are barely known. Herein, the Oncomine database and cBioPortal platform were selected to predict the differential expression levels of STEAP members and clinical prognosis. The most common expression pattern observed was the combination of the over- and underexpression of distinct STEAP genes, but cervical and gastric cancer and lymphoma showed overexpression of all STEAP genes. It was also found that STEAP genes’ expression levels were already deregulated in benign lesions. Regarding the prognostic value, it was found that STEAP1 (prostate), STEAP2 (brain and central nervous system), STEAP3 (kidney, leukemia and testicular) and STEAP4 (bladder, cervical, gastric) overexpression correlate with lower patient survival rate. However, in prostate cancer, overexpression of the STEAP4 gene was correlated with a higher survival rate. Overall, this study first showed that the expression levels of STEAP genes are highly variable in human cancers, which may be related to different patients’ outcomes.