Growth/differentiation factor-15: prostate cancer suppressor or promoter?

Phthalate exposure induces microRNA-5010/Nrf2-EGR1/GDF15 signaling expression in prostate cancer

Phthalate exposure is linked to prostate enlargement through sex hormonal changes and oxidative stress. However, its role and action mechanism in prostate cancer remain unclear. This study examined two patient cohorts: 204 patients undergoing prostate biopsy (24 benign and 180 malignancies) and 85 with confirmed prostate cancer receiving robotic-assisted radical prostatectomy. Urine samples, collected with informed consent, were analyzed for urinary DEHP metabolites using HPLC-MS and ELISA. Patients with prostate cancer exhibited significantly higher urinary MEOHP and ΣDEHP metabolite levels than those who underwent benign biopsy (unpaired t-test, p = 0.027 and 0.039, respectively). MIR-5010 upregulation and MIR-205 downregulation were observed in two paired small RNA sequencing analyses (urine pellets of benign vs. malignant patients and PC3 cells without or with DEHP treatment), correlating with tumor staging in the TCGA prostate cancer cohort. Unlike MIR-205, a known tumor suppressor gene in prostate cancer, gene set enrichment analysis revealed that higher MIR-5010 expression was linked to increased Nrf-2 downstream signaling (enriched score: 0.35; p = 0.17). In vitro assays in prostate cancer cells showed that DEHP enhanced Nrf-2 protein expression and its downstream signaling molecules (i.e., SOD2, Heme oxygenase-1, and EGR-1) while increasing GDF15 mRNA expression via EGR-1 regulation in a dose- and time-dependent manner. Furthermore, urinary GDF15 levels were positively associated with urinary MEOHP and MEHP metabolites in the biopsy cohort (p = 0.0007 and 0.011, respectively) and with urinary oxidative stress marker 8-OHdG, aggressive marker VEGF, and CCL2/MCP-1 levels in the prostatectomy cohort (p = 0.0004, 0.006, and 0.0034, respectively). These findings suggest that phthalate exposure induces Nrf-2 and its downstream signaling (i.e., EGR-1/GDF-15) through microRNA regulation, contributing to prostate cancer aggressiveness.

Compression force promotes glioblastoma progression through the Piezo1‑GDF15‑CTLA4 axis

Glioma, a type of brain tumor, is influenced by mechanical forces in its microenvironment that affect cancer progression. However, our understanding of the contribution of compression and its associated mechanisms remains limited. The objective of the present study was to create an environment in which human brain glioma H4 cells experience pressure and thereby investigate the compressive mechanosensors and signaling pathways. Subsequent time‑lapse imaging and wound healing assays confirmed that 12 h of compression significantly increased cell migration, thereby linking compression with enhanced cell motility. Compression upregulated the expression of Piezo1, a mechanosensitive ion channel, and growth differentiation factor 15 (GDF15), a TGF‑β superfamily member. Knockdown experiments targeting PIEZO1 or GDF15 using small interfering RNA resulted in reduced cell motility, with Piezo1 regulating GDF15 expression. Compression also upregulated CTLA4, a critical immune checkpoint protein. The findings of the present study therefore suggest that compression enhances glioma progression by stimulating Piezo1, promoting GDF15 expression and increasing CTLA4 expression. Thus, these findings provide important insights into the influence of mechanical compression on glioma progression and highlight the involvement of the Piezo1‑GDF15 signaling pathway. Understanding tumor responses to mechanical forces in the brain microenvironment may guide the development of targeted therapeutic strategies to mitigate tumor progression and improve patient outcomes.

Proteomic Analysis of Microsomal Proteins Reveals That MVP Is Crucial for the Secretion of GDF-15, Which in Turn Promotes the Neuroendocrine Differentiation of PCa Cells

Neuroendocrine prostate cancer (NEPC) is an aggressive androgen-independent PCa (AIPC) that tends to resist treatment. Understanding its progression and resistance could improve survival outcomes. Previous studies on PCa cells highlighted microsomal proteins' role in PCa progression, but their role in the progression of NEPC remains unclear. Thus, we investigated microsomal proteins in in vitro differentiated NE-LNCaP cells and their role in NED of PCa. Microsomal proteomics revealed two cancer-associated proteins GDF-15 and MVP as elevated in NE-LNCaP cells with GDF-15 among the top 5 upregulated proteins. MVP is elevated in NE-LNCaP and is also increased in NCI-H660 microsomes compared to LNCaP. GO and protein network analysis showed that different molecular networks are affected by microsomal protein enrichment, and MVP and GDF-15 are mapped to functional subnetworks associated with cancer. Remarkably, GDF-15 and MVP are essential for LNCaP cell differentiation when stimulated with Forskolin. Interestingly, AKT and MAPK/ERK signaling pathways are significantly upregulated in NE-LNCaP and NCI-H660 cells with the direct involvement of GDF-15. In summary, we have uncovered that GDF-15 and MVP are involved in NED, with MVP being essential for GDF-15 secretion, promoting NED in PCa cells. These findings provide insights into NED mechanisms and suggest potential therapeutic targets or biomarkers for NEPC.

Racial disparity in prostate cancer: an outlook in genetic and molecular landscape

Prostate cancer (PCa) incidence, morbidity, and mortality rates are significantly impacted by racial disparities. Despite innovative therapeutic approaches and advancements in prevention, men of African American (AA) ancestry are at a higher risk of developing PCa and have a more aggressive and metastatic form of the disease at the time of initial PCa diagnosis than other races. Research on PCa has underlined the biological and molecular basis of racial disparity and emphasized the genetic aspect as the fundamental component of racial inequality. Furthermore, the lower enrollment rate, limited access to national-level cancer facilities, and deferred treatment of AA men and other minorities are hurdles in improving the outcomes of PCa patients. This review provides the most up-to-date information on various biological and molecular contributing factors, such as the single nucleotide polymorphisms (SNPs), mutational spectrum, altered chromosomal loci, differential gene expression, transcriptome analysis, epigenetic factors, tumor microenvironment (TME), and immune modulation of PCa racial disparities. This review also highlights future research avenues to explore the underlying biological factors contributing to PCa disparities, particularly in men of African ancestry.

Diagnostic value of serum GDF-15 in patients with pseudomyxoma peritonei

BACKGROUND AND AIMS

Pseudomyxoma peritonei (PMP) is a rare malignancy that lacks a highly sensitive and specific biomarker for its diagnosis. Identifying reliable serum markers is crucial for improving the diagnostic accuracy and management of PMP. This study aims to explore the diagnostic value of serum growth differentiation factor 15 (GDF-15) in patients with PMP.

MATERIAL AND METHODS

We carried on a 1:1 matched case-control study. 44 patients with PMP hospitalized in Aerospace Center Hospital were recruited as cases, and 44 sex- and age-matched apparently healthy participants were selected as controls. The serum GDF-15 concentrations were tested using an ELISA method. The diagnostic value of GDF-15 in PMP patients was assessed by receiver operating characteristic (ROC) curve analysis.

RESULTS

The median serum GDF-15 level in PMP patients was 1192.77 (843.03-1879.06) pg/mL, notably higher than that in healthy controls [533.27 (410.46-641.47) pg/mL] (P<0.001). The area under the curve (AUC) of serum GDF-15 for PMP diagnosis was 0.907, the optimal diagnostic threshold value was 644.58 pg/mL, the sensitivity was 93.18 %, and the specificity was 77.27 %. The AUC of GDF-15 combined with carbohydrate antigen 125 (CA125) was larger than that of GDF-15 alone (P=0.027), and the sensitivity and specificity achieved 86.36 % and 95.45 %. GDF-15 levels showed a significant correlation with age (P=0.042), with younger PMP patients exhibiting notably lower concentrations of GDF-15 compared to older patients.

CONCLUSION

Serum GDF-15 could become a new marker for the PMP diagnosis. The combination of GDF-15 and CA125 demonstrated superior diagnostic performance for PMP compared to GDF-15 alone, achieving a sensitivity of 86.36% and a specificity of 95.45%.

GDF15: Immunomodulatory Role in Hepatocellular Carcinoma Pathogenesis and Therapeutic Implications

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths globally and the sixth most common cancer worldwide. Evidence shows that growth differentiation factor 15 (GDF15) contributes to hepatocarcinogenesis through various mechanisms. This paper reviews the latest insights into the role of GDF15 in the development of HCC, its role in the immune microenvironment of HCC, and its molecular mechanisms in metabolic dysfunction associated steatohepatitis (MASH) and metabolic associated fatty liver disease (MAFLD)-related HCC. Additionally, as a serum biomarker for HCC, diagnostic and prognostic value of GDF15 for HCC is summarized. The article elaborates on the immunological effects of GDF15, elucidating its effects on hepatic stellate cells (HSCs), liver fibrosis, as well as its role in HCC metastasis and tumor angiogenesis, and its interactions with anticancer drugs. Based on the impact of GDF15 on the immune response in HCC, future research should identify its signaling pathways, affected immune cells, and tumor microenvironment interactions. Clinical studies correlating GDF15 levels with patient outcomes can aid personalized treatment. Additionally, exploring GDF15-targeted therapies with immunotherapies could improve anti-tumor responses and patient outcomes.

Utility of the Growth Differentiation Factor-15 in the Differential Diagnosis of Follicular-Patterned Lesions of the Thyroid on Cytopathologic and Histopathologic Samples

Background Follicular-patterned lesions are a major gray zone in thyroid cytopathology. The recently introduced 2022 World Health Organization (WHO) classification emphasizes the importance of genetic alterations in thyroid neoplasms with the introduction of certain newer terminologies that are expected to cause remarkable changes in cytopathologic and histopathologic reporting. Although molecular assays such as the Afirma gene expression classifier and the ThyroSeq are already in use, there has been an ongoing search for further reliable molecular markers. The growth differentiation factor-15 (GDF-15) is one among them. This study aimed to determine the diagnostic utility of GDF-15 mRNA expression in frozen tissue and fine-needle aspiration (FNA) samples from follicular-patterned thyroid lesions and neoplasms. Methodology The real-time quantitative polymerase chain reaction was performed on 75 frozen tissue and FNA samples each from 19 cases of follicular thyroid hyperplasia (FTH), 10 nodular goiters (NGs), 17 follicular thyroid adenomas (FTAs), eight follicular thyroid carcinomas (FTCs), 12 follicular variant of papillary thyroid carcinomas (FVPTCs), and nine classic papillary thyroid carcinomas (CPTCs) that were diagnosed according to the 2017 WHO classification of thyroid neoplasms. The GDF-15 mRNA expression in all these cases was assessed and compared with the control thyroid tissue samples. One-way analysis of variance and the Kruskal-Wallis test were performed using GraphPad Prism 8 software to determine the significance of differences in the GDF-15 mRNA levels among various thyroid lesions. Results A higher GDF-15 mRNA expression was noted in the malignant thyroid neoplasms including FTC, FVPTC, and CPTC in comparison to FTA, with a fold change between the malignant and benign groups being more than 244.18 times. A difference in the fold change was noted between FTH and FTA with an increase in GDF-15 mRNA level in the latter, which was statistically not significant. Conclusions The fact that GDF-15 mRNA was studied both on fine-needle aspiration cytologic and the frozen tissue material and that the majority of the lesions studied were follicular-patterned establishes the GDF-15 as a potential marker not only for diagnosing malignant thyroid neoplasms of the follicular epithelium but also in distinguishing benign and malignant follicular-patterned neoplasms of the thyroid.

Significance of localized expression of full-length growth differentiation factor-15 in cachexia of advanced non-small cell lung cancer

PURPOSE

Growth differentiation factor-15 (GDF-15) is one of the key cachexia-inducing factors. Clinical trials on therapies targeting GDF-15 for cancer and cancer cachexia are underway. While the role of circulating GDF-15 in cachexia has been clarified, the effects of GDF-15 expression within cancer cells remain to be fully elucidated. Hence, the objective of this study was to investigate the expression of GDF-15 in advanced lung cancer tissues and to understand its role in cachexia.

METHODS

We retrospectively examined the expression level of full-length GDF-15 in advanced non-small cell lung cancer tissues and analyzed the relationship between the staining intensity and clinical data in 53 samples.

RESULTS

We found that 52.8% of the total samples were GDF-15 positive, and GDF-15 expression significantly correlated with improved C-reactive protein/albumin ratio (p = 0.008). It did not correlate with the existence of cancer cachexia and overall survival (p = 0.43).

CONCLUSION

Our findings show that GDF-15 expression significantly correlated with improved C-reactive protein/albumin ratio, but not the existence of cancer cachexia in advanced NSCLC patients.

Mass Spectrometry-Based Assessment of Prostate Cancer-Associated Crystalloids Reveals Enrichment for Growth & Differentiation Factor 15 (GDF15)

Intraluminal crystalloids are a common finding within malignant prostatic acini and are infrequently identified within benign glands. The proteomic composition of these crystalloids remains poorly understood and may provide insight regarding prostate cancer pathogenesis. Laser microdissection assisted liquid chromatography tandem mass spectrometry (LMD-LC-MS/MS) was performed to compare proteomic composition of corpora amylacea within benign acini (n=9), prostatic adenocarcinoma-associated crystalloids (n=8), benign (n=8), and malignant prostatic acini (n=6). The expression of candidate biomarkers was then measured in urine specimens from patients with (n=8) and without prostate cancer (n=10) using ELISA; and immunohistochemistry-based expression in adjacent prostate cancer and benign glands was assessed in 56 whole-slide sections from radical prostatectomy specimens. LMD-LC-MS/MS revealed enrichment for the C-terminal portion of growth and differentiation factor 15 (GDF15) in prostatic crystalloids. Although urinary GDF15 levels were higher in patients with prostatic adenocarcinoma compared to those without (median: 1561.2 vs 1101.3, arbitrary units), this did not meet statistical significance (p=0.07). Immunohistochemistry for GDF15 revealed occasional positivity in benign glands (median H-score: 30, n=56), and diffuse positivity in prostatic adenocarcinoma (median H-score: 200, n=56, p<0.0001). No significant difference was identified within different prognostic grade groups of prostatic adenocarcinoma, or within malignant glands with large cribriform morphology. Our results show that the C-terminal portion of GDF15 is enriched in prostate cancer-associated crystalloids, and higher GDF15 expression is seen in malignant rather than benign prostatic acini. Improved understanding of the proteomic composition of prostate cancer-associated crystalloids provides the rationale for evaluating GDF15 as a urine-based biomarker of prostate cancer.

Increased Density of Growth Differentiation Factor-15+ Immunoreactive M1/M2 Macrophages in Prostate Cancer of Different Gleason Scores Compared with Benign Prostate Hyperplasia

Simple Summary

Prostate cancer (PCa) is the second most diagnosed cancer and cause of death in men worldwide. The main challenge is to discover biomarkers for malignancy to guide the physician towards optimized diagnosis and therapy. There is recent evidence that growth differentiation factor-15 (GDF-15) is elevated in cancer patients. Therefore, we aimed to decipher GDF-15+ cell types and their density in biopsies of human PCa patients with Gleason score (GS)6–9 and benign prostate hyperplasia (BPH). Here we show that the density of GDF-15+ cells, mainly identified as interstitial macrophages (MΦ), was higher in GS6–9 than in BPH, and, thus, GDF-15 is intended to differentiate patients with high GS vs. BPH, as well as GS6 vs. GS7 (or even with higher malignancy). Some GDF-15+ MΦ showed a transepithelial migration into the glandular lumen and, thus, might be used for measurement in urine/semen. Taken together, GDF-15 is proposed as a novel tool to diagnose PCa vs. BPH or malignancy (GS6 vs. higher GS) and as a potential target for anti-tumor therapy. GDF-15 in seminal plasma and/or urine could be utilized as a non-invasive biomarker of PCa as compared to BPH.

Abstract

Although growth differentiation factor-15 (GDF-15) is highly expressed in PCa, its role in the development and progression of PCa is unclear. The present study aims to determine the density of GDF-15+ cells and immune cells (M1-/M2 macrophages [MΦ], lymphocytes) in PCa of different Gleason scores (GS) compared to BPH. Immunohistochemistry and double immunofluorescence were performed on paraffin-embedded human PCa and BPH biopsies with antibodies directed against GDF-15, CD68 (M1 MΦ), CD163 (M2 MΦ), CD4, CD8, CD19 (T /B lymphocytes), or PD-L1. PGP9.5 served as a marker for innervation and neuroendocrine cells. GDF-15+ cell density was higher in all GS than in BPH. CD68+ MΦ density in GS9 and CD163+ MΦ exceeded that in BPH. GDF-15+ cell density correlated significantly positively with CD68+ or CD163+ MΦ density in extratumoral areas. Double immunoreactive GDF-15+/CD68+ cells were found as transepithelial migrating MΦ. Stromal CD68+ MΦ lacked GDF-15+. The area of PGP9.5+ innervation was higher in GS9 than in BPH. PGP9.5+ cells, occasionally copositive for GDF-15+, also occurred in the glandular epithelium. In GS6, but not in BPH, GDF-15+, PD-L1+, and CD68+ cells were found in epithelium within luminal excrescences. The degree of extra-/intra-tumoral GDF-15 increases in M1/M2Φ is proposed to be useful to stratify progredient malignancy of PCa. GDF-15 is a potential target for anti-tumor therapy.

Diltiazem inhibits breast cancer metastasis via mediating growth differentiation factor 15 and epithelial-mesenchymal transition

Migration and metastasis commonly happen to triple-negative breast cancer (TNBC) patients with advanced diseases. In many studies, it has been suggested that epithelial-mesenchymal transition (EMT) is one of the key mechanisms triggering cancer metastasis. Accumulating evidence has proven that calcium channel blockers mediate cell motility. Therefore, we attempt to investigate the effects of diltiazem, which has been selected from several FDA-approved clinical calcium channel blockers, on EMT in TNBC. By using both mouse and human TNBC cell lines, we found that diltiazem decreases colony formation and cell migration in breast cancer cells. The expression of epithelial markers such as E-cadherin and ZO-1 were increased dose-dependently by diltiazem, while mesenchymal markers such as Snail and Twist were decreased. In addition, we found that the expression of growth differentiation factor-15 (GDF-15) was also increased by diltiazem. Administering recombinant GDF-15 also reverses EMT, inhibits colony formation and migration in breast cancer cells. Moreover, treatment with diltiazem in tumor-bearing mice also decreases cancer metastasis and nodule formation, with more GDF-15 expression in diltiazem-treated mice than saline-treated mice, respectively. These findings suggest that diltiazem regulates EMT and cell motility through elevating GDF-15 expression in breast cancers in vitro and in vivo.

N-glycosylation of GDF15 abolishes its inhibitory effect on EGFR in AR inhibitor-resistant prostate cancer cells

Castration-resistance of prostate cancer is one of the most challenging clinical problems. In the present study, we have performed proteomics and glycomics using LNCaP model. Growth differentiation factor-15 (GDF15) level is increased in androgen receptor (AR) inhibitor-resistant cells and the inhibitory effect of GDF15 on epithelial growth factor receptor (EGFR) pathway is relieved by GDF15 N70 glycosylation. Interference of GDF15 (siRNA or N70Q dominant negative) or EGFR pathway (inhibitor or siRNA for EGFR, SRC or ERK) decreases the resistant-cell survival in culture and tumor growth in mice. Our study reveals a novel regulatory mechanism of prostate cancer AR inhibitor resistance, raises the possibility of AR/SRC dual-targeting of castration-resistance of prostate cancer, and lays foundation for the future development of selective inhibitors of GDF15 glycosylation.

Proteomics, Phosphoproteomics and Mirna Analysis of Circulating Extracellular Vesicles through Automated and High-Throughput Isolation

Extracellular vesicles (EVs) play an important role in the diagnosis and treatment of diseases because of their rich molecular contents involved in intercellular communication, regulation, and other functions. With increasing efforts to move the field of EVs to clinical applications, the lack of a practical EV isolation method from circulating biofluids with high throughput and good reproducibility has become one of the biggest barriers. Here, we introduce a magnetic bead-based EV enrichment approach (EVrich) for automated and high-throughput processing of urine samples. Parallel enrichments can be performed in 96-well plates for downstream cargo analysis, including EV characterization, miRNA, proteomics, and phosphoproteomics analysis. We applied the instrument to a cohort of clinical urine samples to achieve reproducible identification of an average of 17,000 unique EV peptides and an average of 2800 EV proteins in each 1 mL urine sample. Quantitative phosphoproteomics revealed 186 unique phosphopeptides corresponding to 48 proteins that were significantly elevated in prostate cancer patients. Among them, multiple phosphoproteins were previously reported to associate with prostate cancer. Together, EVrich represents a universal, scalable, and simple platform for EV isolation, enabling downstream EV cargo analyses for a broad range of research and clinical applications.

Tumor microenvironment heterogeneity an important mediator of prostate cancer progression and therapeutic resistance

Prostate cancer is characterized by a high degree of heterogeneity, which poses a major challenge to precision therapy and drug development. In this review, we discuss how nongenetic factors contribute to heterogeneity of prostate cancer. We also discuss tumor heterogeneity and phenotypic switching related to anticancer therapies. Lastly, we summarize the challenges targeting the tumor environments, and emphasize that continued exploration of tumor heterogeneity is needed in order to offer a personalized therapy for advanced prostate cancer patients.

Extracellular Vesicles from 3D Engineered Microtissues Harbor Disease-Related Cargo Absent in EVs from 2D Cultures

Engineered microtissues that recapitulate key properties of the tumor microenvironment can induce clinically relevant cancer phenotypes in vitro. However, their effect on molecular cargo of secreted extracellular vesicles (EVs) has not yet been investigated. Here, the impact of hydrogel-based 3D engineered microtissues on EVs secreted by benign and malignant prostate cells is assessed. Compared to 2D cultures, yield of EVs per cell is significantly increased for cancer cells cultured in 3D. Whole transcriptome sequencing and proteomics of 2D-EV and 3D-EV samples reveal stark contrasts in molecular cargo. For one cell type in particular, LNCaP, enrichment is observed exclusively in 3D-EVs of GDF15, FASN, and TOP1, known drivers of prostate cancer progression. Using imaging flow cytometry in a novel approach to validate a putative EV biomarker, colocalization in single EVs of GDF15 with CD9, a universal EV marker, is demonstrated. Finally, in functional assays it is observed that only 3D-EVs, unlike 2D-EVs, confer increased invasiveness and chemoresistance to cells in 2D. Collectively, this study highlights the value of engineered 3D microtissue cultures for the study of bona fide EV cargoes and their potential to identify biomarkers that are not detectable in EVs secreted by cells cultured in standard 2D conditions.

Ionizing Radiation-Induced GDF15 Promotes Angiogenesis in Human Glioblastoma Models by Promoting VEGFA Expression Through p-MAPK1/SP1 Signaling

Glioblastoma multiforme (GBM), the most aggressive cancer type that has a poor prognosis, is characterized by enhanced and aberrant angiogenesis. In addition to surgical resection and chemotherapy, radiotherapy is commonly used to treat GBM. However, radiation-induced angiogenesis in GBM remains unexplored. This study examined the role of radiation-induced growth/differentiation factor-15 (GDF15) in regulating tumor angiogenesis by promoting intercellular cross-talk between brain endothelial cells (ECs) and glioblastoma cells. Radiation promoted GDF15 secretion from human brain microvascular endothelial cells (HBMVECs). Subsequently, GDF15 activated the transcriptional promoter VEGFA in the human glioblastoma cell line U373 through p-MAPK1/SP1 signaling. Upregulation of vascular endothelial growth factor (VEGF) expression in U373 cells resulted in the activation of angiogenic activity in HBMVECs via KDR phosphorylation. Wound healing, tube formation, and invasion assay results revealed that the conditioned medium of recombinant human GDF15 (rhGDF15)-stimulated U373 cell cultures promoted the angiogenic activity of HBMVECs. In the HBMVEC-U373 cell co-culture, GDF15 knockdown mitigated radiation-induced VEGFA upregulation in U373 cells and enhanced angiogenic activity of HBMVECs. Moreover, injecting rhGDF15-stimulated U373 cells into orthotopic brain tumors in mice promoted angiogenesis in the tumors. Thus, radiation-induced GDF15 is essential for the cross-talk between ECs and GBM cells and promotes angiogenesis. These findings indicate that GDF15 is a putative therapeutic target for patients with GBM undergoing radio-chemotherapy.

GDF15: a potential therapeutic target for type 1 diabetes

INTRODUCTION

Current treatment for type 1 diabetes (T1D) is centered around insulin supplementation to manage the effects of pancreatic β cell loss. GDF15 is a potential preventative therapy against T1D progression that could work to curb increasing disease incidence.

AREAS COVERED

This paper discusses the known actions of GDF15, a pleiotropic protein with metabolic, feeding, and immunomodulatory effects, connecting them to highlight the open opportunities for future research. The role of GDF15 in the prevention of insulitis and protection of pancreatic β cells against pro-inflammatory cytokine-mediated cellular stress are examined and the pharmacological promise of GDF15 and critical areas of future research are discussed.

EXPERT OPINION

GDF15 shows promise as a potential intervention but requires further development. Preclinical studies have shown poor efficacy, but this result may be confounded by the measurement of gross GDF15 instead of the active form. Additionally, the effect of GDF15 in the induction of anorexia and nausea-like behavior and short-half-life present significant challenges to its deployment, but a systems pharmacology approach paired with chronotherapy may provide a possible solution to therapy for this currently unpreventable disease.

Phenotypic characterization of two novel cell line models of castration-resistant prostate cancer

BACKGROUND

Resistance to androgen deprivation therapies is a major driver of mortality in advanced prostate cancer. Therefore, there is a need to develop new preclinical models that allow the investigation of resistance mechanisms and the assessment of drugs for the treatment of castration-resistant prostate cancer.

METHODS

We generated two novel cell line models (LAPC4-CR and VCaP-CR) which were derived by passaging LAPC4 and VCaP cells in vivo and in vitro under castrate conditions. We performed detailed transcriptomic (RNA-seq) and proteomic analyses (SWATH-MS) to delineate expression differences between castration-sensitive and castration-resistant cell lines. Furthermore, we characterized the in vivo and in vitro growth characteristics of these novel cell line models.

RESULTS

The two cell line derivatives LAPC4-CR and VCaP-CR showed castration-resistant growth in vitro and in vivo which was only minimally inhibited by AR antagonists, enzalutamide, and bicalutamide. High-dose androgen treatment resulted in significant growth arrest of VCaP-CR but not in LAPC4-CR cells. Both cell lines maintained AR expression, but exhibited distinct expression changes on the mRNA and protein level. Integrated analyses including data from LNCaP and the previously described castration-resistant LNCaP-abl cells revealed an expression signature of castration resistance.

CONCLUSIONS

The two novel cell line models LAPC4-CR and VCaP-CR and their comprehensive characterization on the RNA and protein level represent important resources to study the molecular mechanisms of castration resistance.

Profiling of Androgen-Dependent Enhancer RNAs Expression in Human Prostate Tumors: Search for Malignancy Transition Markers

Introduction

Although the ability of androgens to promote prostate cancer development has been known for decades, the molecular mechanisms of androgen receptor (AR) signaling in the tumorigenesis remain unclear. Enhancer RNAs (eRNAs) transcribed from strong enhancers, or super-enhancers (SEs), have recently emerged as a novel class of regulatory non-coding RNAs (ncRNAs) that facilitate transcription, including that of androgen target genes, through chromatin looping to position enhancers proximate to the promoters. The aim of this study was to assess androgen-dependent transcription in prostate tumors of eRNAs (designated as KLK3eRNAs) from the SE of the KLK3 gene encoding the prostate-specific antigen (PSA) protein, a clinical marker of prostate carcinogenesis.

Materials and Methods

The androgen-induced KLK3eRNAs were identified in the LNCaP human prostate cancer cell line. The expressions of these KLK3eRNAs together with KLK3 and AR mRNA transcripts were assessed by qRT-PCR in prostate tumor samples from five prostate cancer patients.

Results

Androgen-induced KLK3eRNAs have been identified in the LNCaP cells, and their expression was further analyzed in tumors of prostate cancer patients. Transcripts of the tested KLK3eRNAs have been detected in all clinical samples, but their expression patterns differed between individual tumor specimens. We found a statistically significant correlation between the levels of the KLK3 and AR mRNAs with those of the previously reported KLK3eRNAs, while such correlation was not observed for novel KLK3eRNAs described in our recent report.

Conclusion

Presented data suggest that prostate tumor development may associate with epigenetic reorganization in the KLK3 genomic regulatory elements reflected by changes of the KLK3eRNA expression. Our findings support a potential of eRNAs profiling to be used as diagnostic marker.

Roles and Regulation of Growth differentiation factor-15 in the Immune and tumor microenvironment

Growth differentiation factor-15 (GDF-15), a member of the TGF-β superfamily, plays multiple roles in a wide variety of cellular processes. It is expressed at low levels under normal conditions but is highly expressed in tumor and tumor microenvironment (TME)-related cells, such as fibroblasts and immune cells. The TME consists of the noncancerous cells present in the tumor, including immune cells, fibroblasts, blood vessel signaling molecules and extracellular matrix, which play a key role in tumor development. GDF-15 affects both stromal cells and immune cells in the TME. It also acts on immune checkpoints, such as PD-1/PDL-1 that regulate stemness of cancer cells, indicating that GDF-15 plays a prominent role in cancer, exhibiting both protumorigenic and antitumorigenic effects, although the latter are reported much less often than the former. The present review addresses novel ideas regarding communication between GDF-15 and stromal cells, immune cells, and cancer cells in the TME. In addition, it discusses the possibility of GDF-15's clinical application as a diagnostic biomarker and therapeutic target in cancer.

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.

Inferring biologically relevant molecular tissue substructures by agglomerative clustering of digitized spatial transcriptomes with multilayer

Spatially resolved transcriptomics (SrT) can investigate organ or tissue architecture from the angle of gene programs that define their molecular complexity. However, computational methods to analyze SrT data underexploit their spatial signature. Inspired by contextual pixel classification strategies applied to image analysis, we developed MULTILAYER to stratify maps into functionally relevant molecular substructures. MULTILAYER applies agglomerative clustering within contiguous locally defined transcriptomes (gene expression elements or "gexels") combined with community detection methods for graphical partitioning. MULTILAYER resolves molecular tissue substructures within a variety of SrT data with superior performance to commonly used dimensionality reduction strategies and still detects differentially expressed genes on par with existing methods. MULTILAYER can process high-resolution as well as multiple SrT data in a comparative mode, anticipating future needs in the field. MULTILAYER provides a digital image perspective for SrT analysis and opens the door to contextual gexel classification strategies for developing self-supervised molecular diagnosis solutions. A record of this paper's transparent peer review process is included in the supplemental information.

Growth Differentiation Factor 15 is a Cancer Cell-Induced Mitokine That Primes Thyroid Cancer Cells for Invasiveness

Background: Mitochondrial stress is known to activate the mitochondrial unfolded protein response (UPR^mt). The UPR^mt results in the secretion of mitochondrial cytokines (mitokines), which can promote a hormetic response cell nonautonomously, and has been reported to be protumorigenic. Growth differentiation factor 15 (GDF15) is a well-characterized mitokine, which is reported to have a mitohormetic effect. Thus, we investigated whether GDF15 induction could prime a subpopulation of thyroid cancer cells to provide invasive advantages. Methods: The UPR^mt, including mitokine expression, was assessed in the context of thyroid cancer in vitro and in vivo. GDF15 expression in 266 patients with papillary thyroid carcinoma (PTC) was determined by immunohistochemistry. The serum levels of GDF15 were measured in healthy subjects and PTC patients. In addition, our own and The Cancer Genome Atlas data were analyzed to determine the expression level of GDF15 in thyroid cancers. The role of GDF15 in tumor aggressiveness was investigated by observing the effects of GDF15 knockdown in BCPAP, TPC-1, 8505C, and FRO cells. Results: Pharmacological inhibition of mitochondrial oxidative phosphorylation function in thyroid cancer cells robustly increased GDF15 expression. The expression of GDF15 was associated with activation of the mitochondrial integrated stress response pathway in PTC patients. Circulating GDF15 levels were significantly higher in PTC patients than in the controls, and tumor expression of GDF15 was related to tumor aggressiveness. In vitro and in vivo knockdown of GDF15 in a thyroid cancer model showed decreased viability, migration, and invasion compared with the control cells via regulation of STAT3. Conclusions: In this study, we demonstrated that GDF15 is a mitokine induced in thyroid cancer cells upon mitochondrial stress. GDF15-induced STAT3 activation determined tumor progression in thyroid cancer. The GDF15-STAT3 signaling axis may be a target in aggressiveness of thyroid cancer.

Growth and differentiation factor 15 and NF-κB expression in benign prostatic biopsies and risk of subsequent prostate cancer detection

Growth and differentiation factor 15 (GDF‐15), also known as macrophage inhibitory cytokine 1 (MIC‐1), may act as both a tumor suppressor and promotor and, by regulating NF‐κB and macrophage signaling, promote early prostate carcinogenesis. To determine whether expression of these two inflammation‐related proteins affect prostate cancer susceptibility, dual immunostaining of benign prostate biopsies for GDF‐15 and NF‐κB was done in a study of 503 case‐control pairs matched on date, age, and race, nested within a historical cohort of 10,478 men. GDF‐15 and NF‐κB expression levels were positively correlated (r = 0.39; p < 0.0001), and both were significantly lower in African American (AA) compared with White men. In adjusted models that included both markers, the odds ratio (OR) for NF‐κB expression was statistically significant, OR =0.87; p = 0.03; 95% confidence interval (CI) =0.77–0.99, while GDF‐15 expression was associated with a nominally increased risk, OR =1.06; p = 0.27; 95% CI =0.96–1.17. When modeling expression levels by quartiles, the highest quartile of NF‐κB expression was associated with almost a fifty percent reduction in prostate cancer risk (OR =0.51; p = 0.03; 95% CI =0.29–0.92). In stratified models, NF‐κB had the strongest negative association with prostate cancer in non‐aggressive cases (p = 0.03), older men (p = 0.03), and in case‐control pairs with longer follow‐up (p = 0.02). Risk associated with GDF‐15 expression was best fit using nonlinear regression modeling where both first (p = 0.02) and second (p = 0.03) order GDF‐15 risk terms were associated with significantly increased risk. This modeling approach also revealed significantly increased risk associated with GDF‐15 expression for subsamples defined by AA race, aggressive disease, younger age, and in case‐control pairs with longer follow‐up. Therefore, although positively correlated in benign prostatic biopsies, NF‐κB and GDF‐15 expression appear to exert opposite effects on risk of prostate tumor development.

GDF15 promotes glioma stem cell-like phenotype via regulation of ERK1/2-c-Fos-LIF signaling

Growth differentiation factor 15 (GDF15), a member of the transforming growth factor β family, is associated with tumor progression, metastasis, and cell apoptosis. However, controversy persists regarding the role of GDF15 in different tumor types, and its function in glioma stem cells (GSCs) remains unknown. Here, we report that GDF15 promotes the GSC-like phenotype in GSC-like cells (GSCLCs) through the activation of leukemia inhibitor factor (LIF)–STAT3 signaling. Mechanistically, GDF15 was found to upregulate expression of the transcription factor c-Fos, which binds to the LIF promoter, leading to enhanced transcription of LIF in GSCLCs. Furthermore, GDF15 may activate the ERK1/2 signaling pathway in GSCLCs, and the upregulation of LIF expression and the GSC-like phenotype was dependent on ERK1/2 signaling. In addition, the small immunomodulator imiquimod induced GDF15 expression, which in turn activated the LIF–STAT3 pathway and subsequently promoted the GSC-like phenotype in GSCLCs. Thus, our results demonstrate that GDF15 can act as a proliferative and pro-stemness factor for GSCs, and therefore, it may represent a potential therapeutic target in glioma treatment.

Levels of plasma glycan-binding auto-IgG biomarkers improve the accuracy of prostate cancer diagnosis

Strategies to improve the early diagnosis of prostate cancer will provide opportunities for earlier intervention. The blood-based prostate-specific antigen (PSA) assay is widely used for prostate cancer diagnosis but specificity of the assay is not satisfactory. An algorithm based on serum levels of PSA combined with other serum biomarkers may significantly improve prostate cancer diagnosis. Plasma glycan-binding IgG/IgM studies suggested that glycan patterns differ between normal and tumor cells. We hypothesize that in prostate cancer glycoproteins or glycolipids are secreted from tumor tissues into the blood and induce auto-immunoglobulin (Ig) production. A 24-glycan microarray and a 5-glycan subarray were developed using plasma samples obtained from 35 prostate cancer patients and 54 healthy subjects to identify glycan-binding auto-IgGs. Neu5Acα2-8Neu5Acα2-8Neu5Acα (G81)-binding auto-IgG was higher in prostate cancer samples and, when levels of G81-binding auto-IgG and growth differentiation factor-15 (GDF-15 or NAG-1) were combined with levels of PSA, the prediction rate of prostate cancer increased from 78.2% to 86.2% than with PSA levels alone. The G81 glycan-binding auto-IgG fraction was isolated from plasma samples using G81 glycan-affinity chromatography and identified by N-terminal sequencing of the 50 kDa heavy chain variable region of the IgG. G81 glycan-binding 25 kDa fibroblast growth factor-1 (FGF1) fragment was also identified by N-terminal sequencing. Our results demonstrated that a multiplex diagnostic combining G81 glycan-binding auto-IgG, GDF-15/NAG-1 and PSA (≥ 2.1 ng PSA/ml for cancer) increased the specificity of prostate cancer diagnosis by 8%. The multiplex assessment could improve the early diagnosis of prostate cancer thereby allowing the prompt delivery of prostate cancer treatment.

Growth Differentiation Factor 15 Promotes Progression of Esophageal Squamous Cell Carcinoma via TGF-β Type II Receptor Activation

OBJECTIVES

Growth differentiation factor 15 (GDF15), which is derived from tumor-associated macrophages (TAM) and cancer cells, promotes progression of esophageal squamous cell carcinomas (ESCC). However, its role in the ESCC microenvironment remains unclear. Here, we examined the effects of GDF15 on ESCC cell lines and tissues.

METHODS

Western blotting, MTS, and Transwell migration/invasion assays were used to evaluate cell signaling, proliferation, and migration/invasion, respectively, in ESCC cell lines treated with recombinant human GDF15 (rhGDF15). ESCC cell lines were administered a TGF-βRI/II inhibitor (LY2109761), small interfering RNA against TGF-β type II receptor (TGF-βRII), or neutralizing antibody against TGF-βRII to study the role of TGF-βRII in mediating the effects of rhGDF15. The localization of GDF15 and TGF-βRII in ESCC cell lines was observed by immunofluorescence. TGF-βRII expression in ESCC tissues was analyzed by immunohistochemistry, and the relationship between clinicopathological factors and prognosis in ESCC patients was evaluated.

RESULTS

rhGDF15 increased levels of phosphorylated Akt, Erk1/2, and TGF-βRII in ESCC cell lines. Inhibition/knockdown of TGF-βRII suppressed rhGDF15-induced activation of Akt and Erk1/2 and enhancement of cellular proliferation, migration, and invasion. Immunofluorescence revealed that TGF-βRII and GDF15 were colocalized in ESCC cell lines. High TGF-βRII expression in ESCC tissues, as determined by immunohistochemistry, correlated with depth of invasion and increased number of infiltrating TAMs. ESCC patients with high TGF-βRII expression showed a tendency toward poor prognosis.

CONCLUSIONS

GDF15 promotes ESCC progression by increasing cellular proliferation, migration, and invasion via TGF-βRII signaling.

Role of GDF15 in methylseleninic acid-mediated inhibition of cell proliferation and induction of apoptosis in prostate cancer cells

The growth inhibitory efficacy of methylseleninic acid (MSA) in prostate cancer cells has been documented extensively. However, our understanding of the immediate targets that are key to the growth inhibitory effects of MSA remains limited. Here, using multiple preclinical prostate cancer models, we demonstrated in vitro and in vivo that GDF15 is a most highly induced, immediate target of MSA. We further showed that knockdown of GDF15 mitigates MSA inhibition of cell proliferation and induction of apoptosis. Analysis of gene expression data from over 1000 primary and 200 metastatic prostate cancer samples revealed that GDF15 expression is decreased in metastatic prostate cancers compared to primary tumors and that lower GDF15 levels in primary tumors are associated with higher Gleason scores and shorter survival of the patients. Additionally, pathways that are negatively correlated with GDF15 levels in clinical samples are also negatively correlated with MSA treatment in cultured cells. Since most, if not all, of these pathways have been implicated in prostate cancer progression, suppressing their activities by inducing GDF15 is consistent with the anticancer effects of MSA in prostate cancer. Overall, this study provides support for GDF15 as an immediate target of MSA in prostate cancer cells.

Prostate cancer promotes a vicious cycle of bone metastasis progression through inducing osteocytes to secrete GDF15 that stimulates prostate cancer growth and invasion

Bone is the most frequent site of prostate cancer (PCa) metastasis; however, little is known about the role of the most common cell in bone, the osteocyte (OCy), in cancer biology. In this study we explored the crosstalk between PCa cells and OCys to determine if it contributes to PCa progression. PCa cells induced OCys to promote PCa proliferation, migration and invasion. A chemokine screen revealed that PCa cell induced OCys to produce growth-derived factor 15 (GDF15). Knockdown of GDF15 in OCys demonstrated that PCa cells conferred the ability on OCys to promote PCa proliferation, migration and invasion through GDF15. Consistent with this finding was the observation that the GDF15 receptor, GFRAL, was expressed on multiple PCa cell lines. Transcription factor array screening of PCa cells exposed to OCys with or without knockdown of GDF15 revealed that GDF15 in OCys promoted early growth response 1 (EGR1) expression in the PCa cells. Knockdown of EGR1 expression in PCa cells revealed it was required for the OCy-derived GDF15-mediated induction of in vitro PCa cell proliferation, migration and invasion. Subcutaneous co-injection of PCa cells and OCys into mice revealed that OCys promoted tumor growth in vivo, which was diminished by knockdown of GDF15 in the OCys. Knockdown of GDF15 in the tibiae diminished growth of PCa cancer cells injected into the tibiae, which was accompanied by decreased tumor cell proliferation and EGR1 expression. These results shed light on a novel mechanism through which PCa cells educate OCys to promote progression of PCa bone metastasis. They also suggest that targeting of GDF15-based and EGR1-based signaling pathways should be further explored for their potential to diminish progression of PCa bone metastasis.

Serum Hepcidin and GDF-15 levels as prognostic markers in urothelial carcinoma of the upper urinary tract and renal cell carcinoma

Background

Cancer is a life-threatening disease that causes every fourth death. It is often hard to determine the time point of progression. Therefore, biomarkers for cancer entities that indicate disease progression or aggressiveness and thereby guide therapeutic decisions are required. Unfortunately, reliable biomarkers are rare. In this study, the potential of serum hepcidin and serum GDF-15 as biomarkers that correlate with patient’s survival in the two entities upper urinary tract urothelial carcinomas (UUTUC) and renal cell carcinoma (RCC) were analyzed.

Methods

In this retrospective study n = 38 patients suffering from UUTUC, n = 94 patients suffering from RCC and n = 21 patients without infections or cancer, all hospitalized at the University Hospital Muenster, were included. Serum samples of patients were retrospectively analyzed. Serum hepcidin and GDF-15 levels were measured and correlated to aggressiveness and progression of the disease as well as patient’s outcome.

Results

For both entities, UUTUC and RCC, serum hepcidin levels as well as serum GDF-15 levels were increased compared to sera of controls. High serum hepcidin and GDF-15 levels were associated with metastases and cancer relapse. Also, in both entities, the overall survival was decreased in patients with increased serum hepcidin and GDF-15 levels. Hence, high serum hepcidin and GDF-15 levels correlated with patient’s outcome.

Conclusion

To conclude, the data of this study show a correlation of high serum hepcidin and GDF-15 levels with aggressiveness and progression of the disease and demonstrate potential prognostic properties of serum hepcidin and GDF-15 levels. The data support the further assessment of serum hepcidin and GDF-15 as prognostic markers in RCC and UUTUC.

Uniting GDF15 and GFRAL: Therapeutic Opportunities in Obesity and Beyond

Growth differentiation factor-15 (GDF15) is a circulating protein that has been implicated in multiple biological processes, including energy homeostasis, body weight regulation, and cachexia driven by cancer and chronic disease. The potential to target GDF15 in the treatment of energy-intake disorders, including obesity and anorexia, is an area of intense investigation, but has been limited by the lack of an identified receptor, signaling mechanism, and target tissue. GDNF family receptor α-like (GFRAL) was recently identified as the neuronal brainstem receptor responsible for mediating the anorectic actions of GDF15. Herein, we provide a brief overview of GDF15 biology with a focus on energy homeostasis, and highlight the implications of the recent receptor identification to this field and beyond.

Single-nucleotide polymorphisms of stemness genes predicted to regulate RNA splicing, microRNA and oncogenic signaling are associated with prostate cancer survival

Prostate cancer (PCa) is a clinically and molecularly heterogeneous disease, with variation in outcomes only partially predicted by grade and stage. Additional tools to distinguish indolent from aggressive disease are needed. Phenotypic characteristics of stemness correlate with poor cancer prognosis. Given this correlation, we identified single-nucleotide polymorphisms (SNPs) of stemness-related genes and examined their associations with PCa survival. SNPs within stemness-related genes were analyzed for association with overall survival of PCa in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Significant SNPs predicted to be functional were selected for linkage disequilibrium analysis and combined and stratified analyses. Identified SNPs were evaluated for association with gene expression. SNPs of CD44 (rs9666607), ABCC1 (rs35605 and rs212091) and GDF15 (rs1058587) were associated with PCa survival and predicted to be functional. A role for rs9666607 of CD44 and rs35605 of ABCC1 in RNA splicing regulation, rs212091 of ABCC1 in miRNA binding site activity and rs1058587 of GDF15 in causing an amino acid change was predicted. These SNPs represent potential novel prognostic markers for overall survival of PCa and support a contribution of the stemness pathway to PCa patient outcome.

Multi-region proteome analysis quantifies spatial heterogeneity of prostate tissue biomarkers

Application of pressure cycling technology and Sequential Windowed Acquisition of all THeoretical mass spectrometry allows quantifying the degree of intra-tumor heterogeneity of protein expression in prostate tumors. The data show that protein intra-tumor heterogeneity, if not characterized, may distort protein biomarker suitability in tumor tissues.

It remains unclear to what extent tumor heterogeneity impacts on protein biomarker discovery. Here, we quantified proteome intra-tissue heterogeneity (ITH) based on a multi-region analysis of prostate tissues using pressure cycling technology and Sequential Windowed Acquisition of all THeoretical fragment ion mass spectrometry. We quantified 6,873 proteins and analyzed the ITH of 3,700 proteins. The level of ITH varied depending on proteins and tissue types. Benign tissues exhibited more complex ITH patterns than malignant tissues. Spatial variability of 10 prostate biomarkers was validated by immunohistochemistry in an independent cohort (n = 83) using tissue microarrays. Prostate-specific antigen was preferentially variable in benign prostatic hyperplasia, whereas growth/differentiation factor 15 substantially varied in prostate adenocarcinomas. Furthermore, we found that DNA repair pathways exhibited a high degree of variability in tumorous tissues, which may contribute to the genetic heterogeneity of tumors. This study conceptually adds a new perspective to protein biomarker discovery: it suggests that recent technological progress should be exploited to quantify and account for spatial proteome variation to complement biomarker identification and utilization.

Identification of novel host biomarkers in plasma as candidates for the immunodiagnosis of tuberculosis disease and monitoring of tuberculosis treatment response

There is an urgent need for new tools for the rapid diagnosis of tuberculosis disease. We evaluated the potentials of 74 host markers as biomarkers for the immunological diagnosis of tuberculosis and monitoring of treatment response. Fifty-five individuals that presented with signs and symptoms requiring investigation for tuberculosis disease were prospectively recruited prior to clinical diagnosis, at a health centre in Cape Town, South Africa. Patients were later classified as having tuberculosis disease or other respiratory diseases (ORD) using a combination of clinical, radiological and laboratory findings. Out of 74 host markers that were evaluated in plasma samples from study participants using a multiplex platform, 18 showed potential as tuberculosis diagnostic candidates with the most promising being NCAM, CRP, SAP, IP-10, ferritin, TPA, I-309, and MIG, which diagnosed tuberculosis disease individually, with area under the ROC curve ≥0.80. Six-marker biosignatures containing NCAM diagnosed tuberculosis disease with a sensitivity of 100% (95%CI, 86.3-100%) and specificity of 89.3% (95%CI, 67.6-97.3%) irrespective of HIV status, and 100% accuracy in the absence of HIV infection. Furthermore, the concentrations of 11 of these proteins changed with treatment, thereby indicating that they may be useful in monitoring of the response to tuberculosis treatment. Our findings have potential to be translated into a point-of-care screening test for tuberculosis, after future validation studies.

NF-κB regulates GDF-15 to suppress macrophage surveillance during early tumor development

Macrophages are attracted to developing tumors and can participate in immune surveillance to eliminate neoplastic cells. In response, neoplastic cells utilize NF-κB to suppress this killing activity, but the mechanisms underlying their self-protection remain unclear. Here, we report that this dynamic interaction between tumor cells and macrophages is integrally linked by a soluble factor identified as growth and differentiation factor 15 (GDF-15). In vitro, tumor-derived GDF-15 signals in macrophages to suppress their proapoptotic activity by inhibiting TNF and nitric oxide (NO) production. In vivo, depletion of GDF-15 in Ras-driven tumor xenografts and in an orthotopic model of pancreatic cancer delayed tumor development. This delay correlated with increased infiltrating antitumor macrophages. Further, production of GDF-15 is directly regulated by NF-κB, and the colocalization of activated NF-κB and GDF-15 in epithelial ducts of human pancreatic adenocarcinoma supports the importance of this observation. Mechanistically, we found that GDF-15 suppresses macrophage activity by inhibiting TGF-β-activated kinase (TAK1) signaling to NF-κB, thereby blocking synthesis of TNF and NO. Based on these results, we propose that the NF-κB/GDF-15 regulatory axis is important for tumor cells in evading macrophage immune surveillance during the early stages of tumorigenesis.

Hypoxia Downregulates MAPK/ERK but Not STAT3 Signaling in ROS-Dependent and HIF-1-Independent Manners in Mouse Embryonic Stem Cells

Hypoxia is involved in the regulation of stem cell fate, and hypoxia-inducible factor 1 (HIF-1) is the master regulator of hypoxic response. Here, we focus on the effect of hypoxia on intracellular signaling pathways responsible for mouse embryonic stem (ES) cell maintenance. We employed wild-type and HIF-1α-deficient ES cells to investigate hypoxic response in the ERK, Akt, and STAT3 pathways. Cultivation in 1% O₂ for 24 h resulted in the strong dephosphorylation of ERK and its upstream kinases and to a lesser extent of Akt in an HIF-1-independent manner, while STAT3 phosphorylation remained unaffected. Downregulation of ERK could not be mimicked either by pharmacologically induced hypoxia or by the overexpression. Dual-specificity phosphatases (DUSP) 1, 5, and 6 are hypoxia-sensitive MAPK-specific phosphatases involved in ERK downregulation, and protein phosphatase 2A (PP2A) regulates both ERK and Akt. However, combining multiple approaches, we revealed the limited significance of DUSPs and PP2A in the hypoxia-mediated attenuation of ERK signaling. Interestingly, we observed a decreased reactive oxygen species (ROS) level in hypoxia and a similar phosphorylation pattern for ERK when the cells were supplemented with glutathione. Therefore, we suggest a potential role for the ROS-dependent attenuation of ERK signaling in hypoxia, without the involvement of HIF-1.

Growth differentiation factor 15 is a myomitokine governing systemic energy homeostasis

Reduced mitochondrial electron transport chain activity promotes longevity and improves energy homeostasis via cell-autonomous and -non-autonomous factors in multiple model systems. This mitohormetic effect is thought to involve the mitochondrial unfolded protein response (UPRmt), an adaptive stress-response pathway activated by mitochondrial proteotoxic stress. Using mice with skeletal muscle-specific deficiency of Crif1 (muscle-specific knockout [MKO]), an integral protein of the large mitoribosomal subunit (39S), we identified growth differentiation factor 15 (GDF15) as a UPRmt-associated cell-non-autonomous myomitokine that regulates systemic energy homeostasis. MKO mice were protected against obesity and sensitized to insulin, an effect associated with elevated GDF15 secretion after UPRmt activation. In ob/ob mice, administration of recombinant GDF15 decreased body weight and improved insulin sensitivity, which was attributed to elevated oxidative metabolism and lipid mobilization in the liver, muscle, and adipose tissue. Thus, GDF15 is a potent mitohormetic signal that safeguards against the onset of obesity and insulin resistance.

Khan F, Schmitz U, Wolkenhauer O, Gupta SK. MicroRNA and Transcription Factor Gene Regulatory Network Analysis Reveals Key Regulatory Elements Associated with Prostate Cancer Progression

Technological and methodological advances in multi-omics data generation and integration approaches help elucidate genetic features of complex biological traits and diseases such as prostate cancer. Due to its heterogeneity, the identification of key functional components involved in the regulation and progression of prostate cancer is a methodological challenge. In this study, we identified key regulatory interactions responsible for primary to metastasis transitions in prostate cancer using network inference approaches by integrating patient derived transcriptomic and miRomics data into gene/miRNA/transcription factor regulatory networks. One such network was derived for each of the clinical states of prostate cancer based on differentially expressed and significantly correlated gene, miRNA and TF pairs from the patient data. We identified key elements of each network using a network analysis approach and validated our results using patient survival analysis. We observed that HOXD10, BCL2 and PGR are the most important factors affected in primary prostate samples, whereas, in the metastatic state, STAT3, JUN and JUNB are playing a central role. Benefiting integrative networks our analysis suggests that some of these molecules were targeted by several overexpressed miRNAs which may have a major effect on the dysregulation of these molecules. For example, in the metastatic tumors five miRNAs (miR-671-5p, miR-665, miR-663, miR-512-3p and miR-371-5p) are mainly responsible for the dysregulation of STAT3 and hence can provide an opportunity for early detection of metastasis and development of alternative therapeutic approaches. Our findings deliver new details on key functional components in prostate cancer progression and provide opportunities for the development of alternative therapeutic approaches.

Opposite regulation of MDM2 and MDMX expression in acquisition of mesenchymal phenotype in benign and cancer cells

Plasticity of cancer cells, manifested by transitions between epithelial and mesenchymal phenotypes, represents a challenging issue in the treatment of neoplasias. Both epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are implicated in the processes of metastasis formation and acquisition of stem cell-like properties. Mouse double minute (MDM) 2 and MDMX are important players in cancer progression, as they act as regulators of p53, but their function in EMT and metastasis may be contradictory. Here, we show that the EMT phenotype in multiple cellular models and in clinical prostate and breast cancer samples is associated with a decrease in MDM2 and increase in MDMX expression. Modulation of EMT-accompanying changes in MDM2 expression in benign and transformed prostate epithelial cells influences their migration capacity and sensitivity to docetaxel. Analysis of putative mechanisms of MDM2 expression control demonstrates that in the context of defective p53 function, MDM2 expression is regulated by EMT-inducing transcription factors Slug and Twist. These results provide an alternative context-specific role of MDM2 in EMT, cell migration, metastasis, and therapy resistance.

Association and regulation of protein factors of field effect in prostate tissues

Field effect or field cancerization denotes the presence of molecular aberrations in structurally intact cells residing in histologically normal tissues adjacent to solid tumors. Currently, the etiology of prostate field‑effect formation is unknown and there is a prominent lack of knowledge of the underlying cellular and molecular pathways. We have previously identified an upregulated expression of several protein factors representative of prostate field effect, i.e., early growth response-1 (EGR‑1), platelet-derived growth factor‑A (PDGF‑A), macrophage inhibitory cytokine‑1 (MIC‑1), and fatty acid synthase (FASN) in tissues at a distance of 1 cm from the visible margin of intracapsule prostate adenocarcinomas. We have hypothesized that the transcription factor EGR‑1 could be a key regulator of prostate field‑effect formation by controlling the expression of PDGF‑A, MIC‑1, and FASN. Taking advantage of our extensive quantitative immunofluorescence data specific for EGR‑1, PDGF‑A, MIC‑1, and FASN generated in disease‑free, tumor‑adjacent, and cancerous human prostate tissues, we chose comprehensive correlation as our major approach to test this hypothesis. Despite the static nature and sample heterogeneity of association studies, we show here that sophisticated data generation, such as by spectral image acquisition, linear unmixing, and digital quantitative imaging, can provide meaningful indications of molecular regulations in a physiologically relevant in situ environment. Our data suggest that EGR‑1 acts as a key regulator of prostate field effect through induction of pro‑proliferative (PDGF‑A and FASN), and suppression of pro‑apoptotic (MIC‑1) factors. These findings were corroborated by computational promoter analyses and cell transfection experiments in non‑cancerous prostate epithelial cells with ectopically induced and suppressed EGR‑1 expression. Among several clinical applications, a detailed knowledge of pathways of field effect may lead to the development of targeted intervention strategies preventing progression from pre-malignancy to cancer.

Characterization of Gene Expression Patterns among Artificially Developed Cancer Stem Cells Using Spherical Self-Organizing Map

We performed gene expression microarray analysis coupled with spherical self-organizing map (sSOM) for artificially developed cancer stem cells (CSCs). The CSCs were developed from human induced pluripotent stem cells (hiPSCs) with the conditioned media of cancer cell lines, whereas the CSCs were induced from primary cell culture of human cancer tissues with defined factors (OCT3/4, SOX2, and KLF4). These cells commonly expressed human embryonic stem cell (hESC)/hiPSC-specific genes (POU5F1, SOX2, NANOG, LIN28, and SALL4) at a level equivalent to those of control hiPSC 201B7. The sSOM with unsupervised method demonstrated that the CSCs could be divided into three groups based on their culture conditions and original cancer tissues. Furthermore, with supervised method, sSOM nominated TMED9, RNASE1, NGFR, ST3GAL1, TNS4, BTG2, SLC16A3, CD177, CES1, GDF15, STMN2, FAM20A, NPPB, CD99, MYL7, PRSS23, AHNAK, and LOC152573 genes commonly upregulating among the CSCs compared to hiPSC, suggesting the gene signature of the CSCs.

The oncogene EVI1 enhances transcriptional and biological responses of human myeloid cells to all-trans retinoic acid

The product of the ecotropic virus integration site 1 (EVI1) gene, whose overexpression is associated with a poor prognosis in myeloid leukemias and some epithelial tumors, regulates gene transcription both through direct DNA binding and through modulation of the activity of other sequence specific transcription factors. Previous results from our laboratory have shown that EVI1 influenced transcription regulation in response to the myeloid differentiation inducing agent, all-trans retinoic acid (ATRA), in a dual manner: it enhanced ATRA induced transcription of the RARβ gene, but repressed the ATRA induction of the EVI1 gene itself. In the present study, we asked whether EVI1 would modulate the ATRA regulation of a larger number of genes, as well as biological responses to this agent, in human myeloid cells. U937 and HL-60 cells ectopically expressing EVI1 through retroviral transduction were subjected to microarray based gene expression analysis, and to assays measuring cellular proliferation, differentiation, and apoptosis. These experiments showed that EVI1 modulated the ATRA response of several dozens of genes, and in fact reinforced it in the vast majority of cases. A particularly strong synergy between EVI1 and ATRA was observed for GDF15, which codes for a member of the TGF-β superfamily of cytokines. In line with the gene expression results, EVI1 enhanced cell cycle arrest, differentiation, and apoptosis in response to ATRA, and knockdown of GDF15 counteracted some of these effects. The potential clinical implications of these findings are discussed.

Growth differentiation factor-15: a p53- and demethylation-upregulating gene represses cell proliferation, invasion, and tumorigenesis in bladder carcinoma cells

Growth differentiation factor-15 (GDF15), a member of the TGF-β superfamily, affects tumor biology of certain cancers, but remains poorly understood in bladder cancer cells. This study determined the expression, regulation, function, and potential downstream target genes of GDF15 in bladder carcinoma cells. The transitional papilloma carcionoma cells (RT4) expressed higher levels of GDF15 as compared with the bladder carcinoma cells (HT1376 and T24). Treatments of recombinant human GDF15 (rhGDF15) reduced the proliferations of HT1376 and T24 cells. Expression of GDF15 was upregulated via DNA demethylation and p53. The cell proliferation, invasion, and tumorigenesis were reduced in ectopic overexpression of GDF15, while enhanced in GDF15 knockdown. The expressions of mammary serine protease inhibitor (MASPIN) and N-myc downstream-regulated family genes (NDRG1, NDRG2, and NDRG3) were upregulated by GDF15 overexpressions and rhGDF15 treatments in bladder carcinoma cells. GDF15 knockdown induced epithelial-mesenchymal transition (EMT) and F-actin polarization in HT1376 cells. Our results suggest that enhanced expressions of MASPIN and N-myc downstream-regulated family genes and the modulation of EMT may account for the inhibitory functions of GDF15 in the cell proliferation, invasion, and tumorigenesis of bladder carcinoma cells. The GDF15 should be considered as a tumor suppressor in human bladder carcinoma cells.

Growth Differentiation Factor-15 (GDF-15) is a potential marker of radiation response and radiation sensitivity

We have investigated the importance of GDF-15 (secreted cytokine belonging to the TGF-β superfamily) in low and high dose radiation-induced cellular responses. A telomerase immortalized human fibroblast cell line (F11hT) was used in the experiments. A lentiviral system encoding small hairpin RNAs (shRNA) was used to establish GDF-15 silenced cells. Secreted GDF-15 levels were measured in culture medium by ELISA. Cell cycle analysis was performed by flow cytometry. The experiments demonstrated that in irradiated human fibroblasts GDF-15 expression increased with dose starting from 100mGy. Elevated GDF-15 expression was not detected in bystander cells. The potential role of GDF-15 in radiation response was investigated by silencing GDF-15 in immortalized human fibroblasts with five different shRNA encoded in lentiviral vectors. Cell lines with considerably reduced GDF-15 levels presented increased radiation sensitivity, while a cell line with elevated GDF-15 was more radiation resistant than wild type cells. We have investigated how the reduced GDF-15 levels alter the response of several known radiation inducible genes. In F11hT-shGDF-15 cells the basal expression level of CDKN1A was unaltered relative to F11hT cells, while GADD45A and TGF-β1 mRNA levels were slightly higher, and TP53INP1 was considerably reduced. The radiation-induced expression of TP53INP1 was lower in the silenced than in wild type fibroblast cells. Cell cycle analysis indicated that radiation-induced early G2/M arrest was abrogated in GDF-15 silenced cells. Moreover, radiation-induced bystander effect was less pronounced in GDF-15 silenced fibroblasts. In conclusion, the results suggest that GDF-15 works as a radiation inducible radiation resistance increasing factor in normal human fibroblast cells, acts by regulating the radiation-induced transcription of several genes and might serve as a radiation-induced early biomarker in exposed cells.

Inflammation and prostate cancer: friends or foe?

INTRODUCTION

Prostate cancer is the most common non-cutaneous malignancy diagnosed in men. Moving from histological observations since a long time, it has been recognized that innate and adaptive immunity actively participates in the pathogenesis, surveillance, and progression of prostate cancer.

MATERIALS AND METHODS

A PubMed and Web of Science databases search was performed for studies providing evidence on the roles of the innate and adaptive immunity during the development and progression of prostate cancer.

CONCLUSIONS

There are growing evidences that chronic inflammation is involved in the regulation of cellular events in prostate carcinogenesis, including disruption of the immune response and regulation of the tumor microenvironment. This review discusses the role played by the innate and adaptive immune system in the local progression of prostate cancer, and the prognostic information that we can currently understand and exploit.

Prostate field cancerization: deregulated expression of macrophage inhibitory cytokine 1 (MIC-1) and platelet derived growth factor A (PDGF-A) in tumor adjacent tissue

Prostate field cancerization denotes molecular alterations in histologically normal tissues adjacent to tumors. Such alterations include deregulated protein expression, as we have previously shown for the key transcription factor early growth response 1 (EGR-1) and the lipogenic enzyme fatty acid synthase (FAS). Here we add the two secreted factors macrophage inhibitory cytokine 1 (MIC-1) and platelet derived growth factor A (PDGF-A) to the growing list of protein markers of prostate field cancerization. Expression of MIC-1 and PDGF-A was measured quantitatively by immunofluorescence and comprehensively analyzed using two methods of signal capture and several groupings of data generated in human cancerous (n = 25), histologically normal adjacent (n = 22), and disease-free (n = 6) prostate tissues. A total of 208 digitized images were analyzed. MIC-1 and PDGF-A expression in tumor tissues were elevated 7.1x to 23.4x and 1.7x to 3.7x compared to disease-free tissues, respectively (p<0.0001 to p = 0.08 and p<0.01 to p = 0.23, respectively). In support of field cancerization, MIC-1 and PDGF-A expression in adjacent tissues were elevated 7.4x to 38.4x and 1.4x to 2.7x, respectively (p<0.0001 to p<0.05 and p<0.05 to p = 0.51, respectively). Also, MIC-1 and PDGF-A expression were similar in tumor and adjacent tissues (0.3x to 1.0x; p<0.001 to p = 0.98 for MIC-1; 0.9x to 2.6x; p<0.01 to p = 1.00 for PDGF-A). All analyses indicated a high level of inter- and intra-tissue heterogeneity across all types of tissues (mean coefficient of variation of 86.0%). Our data shows that MIC-1 and PDGF-A expression is elevated in both prostate tumors and structurally intact adjacent tissues when compared to disease-free specimens, defining field cancerization. These secreted factors could promote tumorigenesis in histologically normal tissues and lead to tumor multifocality. Among several clinical applications, they could also be exploited as indicators of disease in false negative biopsies, identify areas of repeat biopsy, and add molecular information to surgical margins.

Secretome analysis of an osteogenic prostate tumor identifies complex signaling networks mediating cross-talk of cancer and stromal cells within the tumor microenvironment

A distinct feature of human prostate cancer (PCa) is the development of osteoblastic (bone-forming) bone metastases. Metastatic growth in the bone is supported by factors secreted by PCa cells that activate signaling networks in the tumor microenvironment that augment tumor growth. To better understand these signaling networks and identify potential targets for therapy of bone metastases, we characterized the secretome of a patient-derived xenograft, MDA-PCa-118b (PCa-118b), generated from osteoblastic bone lesion. PCa-118b induces osteoblastic tumors when implanted either in mouse femurs or subcutaneously. To study signaling molecules critical to these unique tumor/microenvironment-mediated events, we performed mass spectrometry on conditioned media of isolated PCa-118b tumor cells, and identified 26 secretory proteins, such as TGF-β2, GDF15, FGF3, FGF19, CXCL1, galectins, and β2-microglobulin, which represent both novel and previously published secreted proteins. RT-PCR using human versus mouse-specific primers showed that TGFβ2, GDF15, FGF3, FGF19, and CXCL1 were secreted from PCa-118b cells. TGFβ2, GDF15, FGF3, and FGF19 function as both autocrine and paracrine factors on tumor cells and stromal cells, that is, endothelial cells and osteoblasts. In contrast, CXCL1 functions as a paracrine factor through the CXCR2 receptor expressed on endothelial cells and osteoblasts. Thus, our study reveals a complex PCa bone metastasis secretome with paracrine and autocrine signaling functions that mediate cross-talk among multiple cell types within the tumor microenvironment.

Mechanism of action and clinical activity of tasquinimod in castrate-resistant prostate cancer

Castrate-resistant prostate cancer (CRPC) is a disease where survival is poor and treatment is challenging. Over the past 3 years, significant advances in the field have been made with US Food and Drug Administration approval of new drugs for patients with CRPC. However, despite the presence of new approved drugs such as enzalutamide, abiraterone, sipuleucel-T, cabazitaxel, and alpharadin, there is still an unmet need for novel agents with different mechanisms of action to target CRPC. Based on earlier studies demonstrating therapeutic potential of a quinoline-3-carboxamide agent roquinimex as an anticancer drug, efforts were directed to identify other useful members in this class. Tasquinimod is a second-generation quinoline-3-carboxamide agent that is currently in final stages of clinical development as a treatment for CRPC. The preclinical studies of tasquinimod have formed the basis for its success as an antiangiogenic and immunomodulatory agent in this disease. Tasquinimod is an orally available agent that has shown efficacy and favorable safety profile as deduced by the results of Phase I and II clinical trials of this drug in prostate cancer. The place of tasquinimod in the treatment of CRPC patients is currently under examination in an ongoing Phase III clinical trial. In this review, we will discuss tasquinimod, starting from its discovery and current knowledge on potential mechanisms of action to its clinical potential in CRPC.

RNPC1, an RNA-binding protein and a p53 target, regulates macrophage inhibitory cytokine-1 (MIC-1) expression through mRNA stability

Macrophage inhibitory cytokine-1 (MIC-1), a secreted cytokine, is a direct target of p53 and known to play a role in cell proliferation, apoptosis, cell metastasis, and angiogenesis through autocrine and paracrine signaling. Previous studies have shown that serum levels of MIC-1 closely parallel cancer progression and are being explored as a diagnostic tool. MIC-1 has also shown potential as a therapeutic agent as it has exhibited several anti-carcinogenic activities. Thus, MIC-1 displays two opposing effects: tumor suppression versus promotion. However, it remains unclear whether MIC-1 is regulated by a mechanism other than transcription and how MIC-1 exerts its tumor suppression. In this study, we show that overexpression of RNA-binding protein RNPC1 can increase, whereas knockdown or knock-out of RNPC1 decreases, MIC-1 transcript and protein levels. Additionally, we demonstrate that RNPC1 can bind to MIC-1 mRNA via an AU-rich element within MIC-1 3'-UTR and then enhances MIC-1 mRNA stability. Finally, to explore the functional significance of MIC-1, we showed that knockdown of MIC-1 can decrease RNPC1-induced cell growth suppression. Altogether, we uncover a novel mechanism by which MIC-1 can be regulated through RNPC1 via mRNA stability.