Macrophage inhibitory cytokine-1 (MIC-1/GDF15) slows cancer development but increases metastases in TRAMP prostate cancer prone mice. PLoS One. 2012;7:e43833. [PMID: 22952779 PMCID: PMC3428289 DOI: 10.1371/journal.pone.0043833]

Growth differentiation factor-15 may be a novel biomarker in pancreatic cancer: A review

Pancreatic cancer is a highly malignant and invasive gastrointestinal tumor that is often diagnosed at an advanced stage with a poor prognosis and high mortality. Currently, carbohydrate antigen199(CA199) is the only biomarker approved by the FDA for the diagnosis of pancreatic cancer, but it has great limitations. Growth differentiation factor-15 (GDF-15) is expected to be a novel biomarker for the diagnosis, efficacy prediction, and prognosis assessment of pancreatic cancer patients. In this paper, we searched the keywords GDF-15, macrophage inhibitory cytokine-1 (MIC-1), CA199, pancreatic cancer, and tumor markers in PubMed and Web of Science, searched related articles, and read and analyzed the retrieved papers. Finally, we systematically described the characteristics, mechanism of action, and clinical value of GDF-15, aiming to provide help for the detection and treatment of pancreatic cancer.

Local anesthetic lidocaine-inducible gene, growth differentiation factor-15 suppresses the growth of cancer cell lines

Administration of local anesthetics, such as lidocaine, in the perioperative period improves outcomes of cancer patients. However, its precise mechanism is still unresolved. The growth of human cancer cell lines, including HeLa cells, are suppressed by lidocaine treatment. We identified that growth differentiation factor-15 (GDF-15) was commonly upregulated in lidocaine-treated cancer cell lines. GDF-15 is a divergent member of the transforming growth factor-β (TGF-β) superfamily and it is produced as an unprocessed pro-protein form and then cleaved to generate a mature form. In lidocaine-treated HeLa cells, increased production of GDF-15 in the endoplasmic reticulum (ER) was observed and unprocessed pro-protein form of GDF-15 was secreted extracellularly. Further, lidocaine induced apoptosis and apoptosis-inducible Tribbles homologue 3 (TRIB3) was also commonly upregulated in lidocaine-treated cancer cell lines. In addition, transcription factor C/EBP homologous protein (CHOP), which is a positive regulator of not only GDF-15 but TRIB3 was also induced by lidocaine. Lidocaine-induced growth suppression and apoptosis was suppressed by knockdown of GDF-15 or TRIB3 expression by small interference RNA (siRNA). These observations suggest that lidocaine suppresses the growth of cancer cells through increasing GDF-15 and TRIB3 expression, suggesting its potential application as cancer therapy.

Growth differentiation factor-15 overexpression promotes cell proliferation and predicts poor prognosis in cerebral lower-grade gliomas correlated with hypoxia and glycolysis signature

AIMS

Growth differentiation factor-15 (GDF15) plays complex and controversial roles in cancer. In this study, the prognostic value and the exact biological function of GDF15 in cerebral lower-grade gliomas (LGGs) and its potential molecular targets were examined.

MAIN METHODS

Wilcoxon signed-rank test and logistic regression were applied to analyze associations between GDF15 expression and clinical characteristics using the Cancer Genome Atlas (TCGA) database. Overall survival was analyzed using Kaplan-Meier and Cox analyses. Gene set enrichment analysis (GSEA) and the hypoxia risk model was conducted to identify the potential molecular mechanisms underlying the effects of GDF15 on LGGs tumorigenesis. The biological function of GDF15 was examined using gain- and loss-of-function experiments, and a recombinant hGDF15 protein in LGG SW1783 cells in vitro.

KEY FINDINGS

We found that higher GDF15 expression is associated with poor clinical features in LGG patients, and an independent risk factor for overall survival among LGG patients. GSEA results showed that the poor prognostic role of GDF15 in LGGs is related to hypoxia and glycolysis signatures, which was further validated using the hypoxia risk model. Furthermore, GDF15 overexpression facilitated cell proliferation, while GDF15 siRNA inhibits cell proliferation in LGG SW1783 cells. In addition, GDF15 was upregulated upon CoCl2 treatment which induces hypoxia, correlating with the upregulation of the expressions of HIF-1α and glycolysis-related key genes in SW1783 cells.

SIGNIFICANCE

GDF15 may promote LGG tumorigenesis that is associated with the hypoxia and glycolysis pathways, and thus could serve as a promising molecular target for LGG prevention and therapy.

Bidirectional Relationship Between Cancer and Heart Failure: Insights on Circulating Biomarkers

Cancer and heart failure are the two leading causes of death in developed countries. These two apparently distinct clinical entities share similar risk factors, symptoms, and pathophysiological mechanisms (inflammation, metabolic disturbances, neuro-hormonal and immune system activation, and endothelial dysfunction). Beyond the well-known cardiotoxic effects of oncological therapies, cancer and heart failure are thought to be tied by a bidirectional relationship, where one disease favors the other and vice versa. In this context, biomarkers represent a simple, reproducible, sensitive and cost-effective method to explore such relationship. In this review, we recapitulate the evidence on cardiovascular and oncological biomarkers in the field of cardioncology, focusing on their role in treatment-naïve cancer patients. Cardioncological biomarkers are useful tools in risk stratification, early detection of cardiotoxicity, follow-up, and prognostic assessment. Intriguingly, these biomarkers might contribute to better understand the common pathophysiology of cancer and heart failure, thus allowing the implementation of preventive and treatment strategies in cardioncological patients

Macrophage inhibitory cytokine-1 in cancer: Beyond the cellular phenotype

Despite technological advances in diagnostic abilities and improved treatment methods, the burden of cancers remains high, leading to significant morbidity and mortality. One primary reason is that cancer cell secretory factors modulate the tumor microenvironment, supporting tumor growth and circumvents anticancer activities of conventional therapies. Macrophage inhibitory cytokine-1 (MIC-1) is a pleiotropic cytokine elevated in various cancers. MIC-1 regulates various cancer hallmarks, including sustained proliferation, tumor-promoting inflammation, avoiding immune destruction, inducing invasion, metastasis, angiogenesis, and resisting cell death. Despite these facts, the molecular regulation and downstream signaling of MIC-1 in cancer remain elusive, partly because its receptor (GFRAL) was unknown until recently. Binding of MIC-1 to GFRAL recruits the coreceptor tyrosine kinase RET to execute its downstream signaling. So far, studies have shown that GFRAL expression is restricted to the brain stem and is responsible for MIC-1/GFRAL/RET-mediated metabolic disorders. Nevertheless, abundant levels of MIC-1 expression have been reported in all cancer types and have been proposed as a surrogate biomarker. Given the ubiquitous expression of MIC-1 in cancers, it is crucial to understand both upstream regulation and downstream MIC-1/GFRAL/RET signaling in cancer hallmark traits.

GDF15, an emerging key player in human aging

Growth differentiation factor 15 (GDF15) is recently emerging not only as a stress-related mitokine, but also as a key player in the aging process, being one of the most up-regulated protein with age and associated with a variety of age-related diseases (ARDs). Many data indicate that GDF15 has protective roles in several tissues during different stress and aging, thus playing a beneficial role in apparent contrast with the observed association with many ARDs. A possible detrimental role for this protein is then hypothesized to emerge with age. Therefore, GDF15 can be considered as a pleiotropic factor with beneficial activities that can turn detrimental in old age possibly when it is chronically elevated. In this review, we summarize the current knowledge on the biology of GDF15 during aging. We also propose GDF15 as a part of a dormancy program, where it may play a role as a mediator of defense processes aimed to protect from inflammatory damage and other stresses, according to the life history theory.

Elevated expression of the colony-stimulating factor 1 (CSF1) induces prostatic intraepithelial neoplasia dependent of epithelial-Gp130

Macrophages are increased in human benign prostatic hyperplasia and prostate cancer. We generate a Pb-Csf1 mouse model with prostate-specific overexpression of macrophage colony-stimulating factor (M-Csf/Csf1). Csf1 overexpression promotes immune cell infiltration into the prostate, modulates the macrophage polarity in a lobe-specific manner, and induces senescence and low-grade prostatic intraepithelial neoplasia (PIN). The Pb-Csf1 prostate luminal cells exhibit increased stem cell features and undergo an epithelial-to-mesenchymal transition. Human prostate cancer patients with high CSF-1 expression display similar transcriptional alterations with the Pb-Csf1 model. P53 knockout alleviates senescence but fails to progress PIN lesions. Ablating epithelial Gp130 but not Il1r1 substantially blocks PIN lesion formation. The androgen receptor (AR) is downregulated in Pb-Csf1 mice. ChIP-Seq analysis reveals altered AR binding in 2482 genes although there is no significant widespread change in global AR transcriptional activity. Collectively, our study demonstrates that increased macrophage infiltration causes PIN formation but fails to transform prostate cells.

Pathophysiological role of growth differentiation factor 15 (GDF15) in obesity, cancer, and cachexia

Growth differentiation factor 15 or macrophage inhibitory cytokine-1 (GDF15/MIC-1) is a divergent member of the transforming growth factor β superfamily and has a diverse pathophysiological roles in cancers, cardiometabolic disorders, and other diseases. GDF15 controls hematopoietic growth, energy homeostasis, adipose tissue metabolism, body growth, bone remodeling, and response to stress signals. The role of GDF15 in cancer development and progression is complicated and depends on the specific cancer type, stage, and tumor microenvironment. Recently, research on GDF15 and GDF15-associated signaling has accelerated due to the identification of the GDF15 receptor: glial cell line-derived neurotrophic factor (GDNF) family receptor α-like (GFRAL). Therapeutic interventions to target GDF15 and/or GFRAL revealed the mechanisms that drive its activity and might improve overall outcomes of patients with metabolic disorders and cancer. This review highlights the structure and functions of GDF15 and its receptor, emphasizing the pleiotropic role of GDF15 in obesity, tumorigenesis, metastasis, immunomodulation, and cachexia.

NR5A2 transcriptional activation by BRD4 promotes pancreatic cancer progression by upregulating GDF15

NR5A2 is a transcription factor regulating the expression of various oncogenes. However, the role of NR5A2 and the specific regulatory mechanism of NR5A2 in pancreatic ductal adenocarcinoma (PDAC) are not thoroughly studied. In our study, Western blotting, real-time PCR, and immunohistochemistry were conducted to assess the expression levels of different molecules. Wound-healing, MTS, colony formation, and transwell assays were employed to evaluate the malignant potential of pancreatic cancer cells. We demonstrated that NR5A2 acted as a negative prognostic biomarker in PDAC. NR5A2 silencing inhibited the proliferation and migration abilities of pancreatic cancer cells in vitro and in vivo. While NR5A2 overexpression markedly promoted both events in vitro. We further identified that NR5A2 was transcriptionally upregulated by BRD4 in pancreatic cancer cells and this was confirmed by Chromatin immunoprecipitation (ChIP) and ChIP-qPCR. Besides, transcriptome RNA sequencing (RNA-Seq) was performed to explore the cancer-promoting effects of NR5A2, we found that GDF15 is a component of multiple down-regulated tumor-promoting gene sets after NR5A2 was silenced. Next, we showed that NR5A2 enhanced the malignancy of pancreatic cancer cells by inducing the transcription of GDF15. Collectively, our findings suggest that NR5A2 expression is induced by BRD4. In turn, NR5A2 activates the transcription of GDF15, promoting pancreatic cancer progression. Therefore, NR5A2 and GDF15 could be promising therapeutic targets in pancreatic cancer.

Hepatic Stellate Cells in Hepatocellular Carcinoma Promote Tumor Growth Via Growth Differentiation Factor 15 Production

BACKGROUND & AIMS

Although the tumor microenvironment plays an important role in tumor growth, it is not fully understood what role hepatic stellate cells (HSCs) play in the hepatocellular carcinoma (HCC) microenvironment.

METHODS

A high-fat diet after streptozotocin was administered to HSC-specific Atg7-deficient (GFAP-Atg7 knockout [KO]) or growth differentiation factor 15 (GDF15)-deficient (GFAP-GDF15KO) mice. LX-2 cells, a human HSC cell line, were cultured with human hepatoma cells.

RESULTS

In the steatohepatitis-based tumorigenesis model, GFAP-Atg7KO mice formed fewer and smaller liver tumors than their wild-type littermates. Mixed culture of LX-2 cells and hepatoma cells promoted LX-2 cell autophagy and hepatoma cell proliferation, which were attenuated by Atg7 KO in LX-2 cells. Hepatoma cell xenograft tumors grew rapidly in the presence of LX-2 cells, but Atg7 KO in LX-2 cells abolished this growth. RNA-sequencing revealed that LX-2 cells cultured with HepG2 cells highly expressed GDF15, which was abolished by Atg7 KO in LX-2 cells. GDF15 KO LX-2 cells did not show a growth-promoting effect on hepatoma cells either in vitro or in the xenograft model. GDF15 deficiency in HSCs reduced liver tumor size caused by the steatohepatitis-based tumorigenesis model. GDF15 was highly expressed and GDF15-positive nonparenchymal cells were more abundant in human HCC compared with noncancerous parts. Single-cell RNA sequencing showed that GDF15-positive rates in HSCs were higher in HCC than in background liver. Serum GDF15 levels were high in HCC patients and increased with tumor progression.

CONCLUSIONS

In the HCC microenvironment, an increase of HSCs that produces GDF15 in an autophagy-dependent manner may be involved in tumor progression.

GDF15 serves as a coactivator to enhance KISS-1 gene transcription through interacting with Sp1

GDF15 has been recently recognized as a tumor-suppressive gene. However, the underlying mechanism by which GDF15 affects breast carcinogenesis is not well understood. Here, we showed that the inhibitory effect of GDF15 on cell proliferation was dependent on the nuclear localization of the protein. Dynamic translocation of GDF15 into the nucleus altered expression of a number of genes, including KISS-1, and resulted in inhibition of cell growth and invasive behavior. Using KISS-1 promoter-driven luciferase reporter and chromatin immunoprecipitation assays, we demonstrated that, in highly malignant breast cancer cells, GDF15 directly interacts with specific protein-1 (Sp1) at the Sp1-binding sites of the KISS-1 promoter, leading to upregulated KISS-1 expression. Our study indicates that nuclear GDF15 could serve as a transcriptional coactivator to mediate the expression of particular genes to reduce cell proliferation.

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.

GDF-15 Neutralization Alleviates Platinum-Based Chemotherapy-Induced Emesis, Anorexia, and Weight Loss in Mice and Nonhuman Primates

Platinum-based cancer therapy is restricted by dose-limiting side effects and is associated with elevation of growth differentiation factor 15 (GDF-15). But whether this elevation contributes to such side effects has been unclear. Here, we explored the effects of GDF-15 blockade on platinum-based chemotherapy-induced emesis, anorexia, and weight loss in mice and/or nonhuman primate models. We found that circulating GDF-15 is higher in subjects with cancer receiving platinum-based chemotherapy and is positively associated with weight loss in colorectal cancer (NCT00609622). Further, chemotherapy agents associated with high clinical emetic score induce circulating GDF-15 and weight loss in mice. Platinum-based treatment-induced anorexia and weight loss are attenuated in GDF-15 knockout mice, while GDF-15 neutralization with the monoclonal antibody mAB1 improves survival. In nonhuman primates, mAB1 treatment attenuates anorexia and emesis. These results suggest that GDF-15 neutralization is a potential therapeutic approach to alleviate chemotherapy-induced side effects and improve the quality of life.

The GDF15-GFRAL Pathway in Health and Metabolic Disease: Friend or Foe?

GDF15 is a cell activation and stress response cytokine of the glial cell line-derived neurotrophic factor family within the TGF-β superfamily. It acts through a recently identified orphan member of the GFRα family called GFRAL and signals through the Ret coreceptor. Cell stress and disease lead to elevated GDF15 serum levels, causing anorexia, weight loss, and alterations to metabolism, largely by actions on regions of the hindbrain. These changes restore homeostasis and, in the case of obesity, cause a reduction in adiposity. In some diseases, such as advanced cancer, serum GDF15 levels can rise by as much as 10-100-fold, leading to an anorexia-cachexia syndrome, which is often fatal. This review discusses how GDF15 regulates appetite and metabolism, the role it plays in resistance to obesity, and how this impacts diseases such as diabetes, nonalcoholic fatty liver disease, and anorexia-cachexia syndrome. It also discusses potential therapeutic applications of targeting the GDF15-GFRAL pathway and lastly suggests some potential unifying hypotheses for its biological role.

Folic acid-modified Exosome-PH20 enhances the efficiency of therapy via modulation of the tumor microenvironment and directly inhibits tumor cell metastasis

High accumulation of hyaluronan (HA) in the tumor microenvironment leads to an increase in the interstitial pressure and reduction perfusion of drugs. Furthermore, high molecular-weight (HMW)-HA suppresses M1 macrophage polarization, enhances M2 polarization, and induces immunosuppression. Hyaluronidase treatment have attempted to decrease the quantity of HA in tumors. However, hyaluronidase-driven HA degradation driven accelerates tumor cell metastasis, which is a major cause of mortality in cancer patients. Thus, we designed a novel exosome-based drug delivery system (DDS), named Exos-PH20-FA, using genetic engineering to express human hyaluronidase (PH20) and self-assembly techniques to modify the exosomes with folic acid (FA). Our results show that Exos-PH20-FA degraded HMW-HA to low-molecular-weight (LMW)-HA. Moreover, LMW-HA polarized macrophages to the M1 phenotype and reduced the number of relevant immunosuppressive immunocytes which changed the immune microenvironment from an immunosuppressive to immunosupportive phenotype. Furthermore, we demonstrated Exos-PH20-FA directly reduced hyaluronidase-induced metastasis of tumor cells. This tumor treatment also allowed an enhanced delivery of chemotherapy by tumor-targeting effect with FA modification. Our findings indicate that Exos-PH20-FA improves tumor treatment efficiency and reduces the side effects of hyaluronidase treatment, namely tumor cell metastasis. This all-in-one exosome-based HA targeting DDS maybe a promising treatment that yields more efficient and safer results.

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High molecular-weight hyaluronan is related to tumor progression.

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The degradation of hyaluronan enhance cancer cell migration and metastasis.

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Folic acid can target tumor and inhibit tumor cell migration.

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Exosomes are ideal carriers for chemotherapeutics, folic acid and hyaluronidase.

GDF15: A Hormone Conveying Somatic Distress to the Brain

GDF15 has recently gained scientific and translational prominence with the discovery that its receptor is a GFRAL-RET heterodimer of which GFRAL is expressed solely in the hindbrain. Activation of this receptor results in reduced food intake and loss of body weight and is perceived and recalled by animals as aversive. This information encourages a revised interpretation of the large body of previous research on the protein. GDF15 can be secreted by a wide variety of cell types in response to a broad range of stressors. We propose that central sensing of GDF15 via GFRAL-RET activation results in behaviors that facilitate the reduction of exposure to a noxious stimulus. The human trophoblast appears to have hijacked this signal, producing large amounts of GDF15 from early pregnancy. We speculate that this encourages avoidance of potential teratogens in pregnancy. Circulating GDF15 levels are elevated in a range of human disease states, including various forms of cachexia, and GDF15-GFRAL antagonism is emerging as a therapeutic strategy for anorexia/cachexia syndromes. Metformin elevates circulating GDF15 chronically in humans and the weight loss caused by this drug appears to be dependent on the rise in GDF15. This supports the concept that chronic activation of the GDF15-GFRAL axis has efficacy as an antiobesity agent. In this review, we examine the science of GDF15 since its identification in 1997 with our interpretation of this body of work now being assisted by a clear understanding of its highly selective central site of action.

Genetic Landscape of Prostate Cancer Conspicuity on Multiparametric Magnetic Resonance Imaging: A Systematic Review and Bioinformatic Analysis

Context

Multiparametric magnetic resonance imaging (mpMRI) detects most, but not all, clinically significant prostate cancer. The genetic basis of prostate cancer visibility and invisibility on mpMRI remains uncertain.

Objective

To systematically review the literature on differential gene expression between mpMRI-visible and mpMRI-invisible prostate cancer, and to use bioinformatic analysis to identify enriched processes or cellular components in genes validated in more than one study.

Evidence acquisition

We performed a systematic literature search of the Medline, EMBASE, PubMed, and Cochrane databases up to January 2020 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. The primary endpoint was differential genetic features between mpMRI-visible and mpMRI-invisible tumours. Secondary endpoints were explanatory links between gene function and mpMRI conspicuity, and the prognostic value of differential gene enrichment.

Evidence synthesis

We retrieved 445 articles, of which 32 met the criteria for inclusion. Thematic synthesis from the included studies showed that mpMRI-visible cancer tended towards enrichment of molecular features associated with increased disease aggressivity, including phosphatase and tensin homologue (PTEN) loss and higher genomic classifier scores, such as Oncotype and Decipher. Three of the included studies had accompanying publicly available data suitable for further bioinformatic analysis. An over-representation analysis of these datasets revealed increased expression of genes associated with extracellular matrix components in mpMRI-visible tumours.

Conclusions

Prostate cancer that is visible on mpMRI is generally enriched with molecular features of tumour development and aggressivity, including activation of proliferative signalling, DNA damage, and inflammatory processes. Additionally, there appears to be concordant cellular components and biological processes associated with mpMRI conspicuity, as highlighted by bioinformatic analysis of large genetic datasets.

Patient summary

Prostate cancer that is detected by magnetic resonance imaging (MRI) tends to have genetic features that are associated with more aggressive disease. This suggests that MRI can be used to assess the likelihood of aggressive prostate cancer, based on tumour visibility.

Growth differentiation factor-15 slows the growth of murine prostate cancer by stimulating tumor immunity

Growth Differentiation Factor-15 (GDF15) is a divergent TGF-beta superfamily cytokine that is overexpressed by most cancers and is induced by anticancer therapy. Transgenic and induced animal models suggest that it protects from cancer development but the mechanisms are uncertain. We investigated the role of immunity in GDF15 induced reduction in prostate cancer (PCa) growth. The C57BL/6 transgenic TRAMP prostate cancer prone mice were bred with mice that were immunodeficient and/or systemically overexpressed GDF15. We developed a novel orthotopic TRAMP PCa model in which primary TRAMP tumor cells were implanted into prostates of mice to reduce the study time. These mice were administered recombinant mouse GDF15, antibody to CD8, PD1 or their respective controls. We found that GDF15 induced protection from tumor growth was reversed by lack of adaptive immunity. Flow cytometric evaluation of lymphocytes within these orthotopic tumors showed that GDF15 overexpression was associated with increased CD8 T cell numbers and an increased number and proportion of recently activated CD8⁺CD11c⁺ T cells and a reduced proportion of "exhausted" CD8⁺PD1⁺ T cells. Further, depletion of CD8 T cells in tumor bearing mice abolished the GDF15 induced protection from tumor growth. Infusion of GDF15 into mice bearing orthotopic TRAMP tumor, substantially reduced tumor growth that was further reduced by concurrent PD1 antibody administration. GDF15 overexpression or recombinant protein protects from TRAMP tumor growth by modulating CD8 T cell mediated antitumor immunity and augments the positive effects of anti-PD1 blockers.

Growth/Differentiation Factor-15 (GDF-15): From Biomarker to Novel Targetable Immune Checkpoint

Growth/differentiation factor-15 (GDF-15), also named macrophage inhibitory cytokine-1, is a divergent member of the transforming growth factor β superfamily. While physiological expression is barely detectable in most somatic tissues in humans, GDF-15 is abundant in placenta. Elsewhere, GDF-15 is often induced under stress conditions, seemingly to maintain cell and tissue homeostasis; however, a moderate increase in GDF-15 blood levels is observed with age. Highly elevated GDF-15 levels are mostly linked to pathological conditions including inflammation, myocardial ischemia, and notably cancer. GDF-15 has thus been widely explored as a biomarker for disease prognosis. Mechanistically, induction of anorexia via the brainstem-restricted GDF-15 receptor GFRAL (glial cell-derived neurotrophic factor [GDNF] family receptor α-like) is well-documented. GDF-15 and GFRAL have thus become attractive targets for metabolic intervention. Still, several GDF-15 mediated effects (including its physiological role in pregnancy) are difficult to explain via the described pathway. Hence, there is a clear need to better understand non-metabolic effects of GDF-15. With particular emphasis on its immunomodulatory potential this review discusses the roles of GDF-15 in pregnancy and in pathological conditions including myocardial infarction, autoimmune disease, and specifically cancer. Importantly, the strong predictive value of GDF-15 as biomarker may plausibly be linked to its immune-regulatory function. The described associations and mechanistic data support the hypothesis that GDF-15 acts as immune checkpoint and is thus an emerging target for cancer immunotherapy.

Retracted: Ras-PI3K-AKT signaling promotes the occurrence and development of uveal melanoma by downregulating H3K56ac expression

BACKGROUND

Uveal melanoma (UM) is an intraocular malignant tumor characterized by rapid progression and recurrence. The current conventional treatments are unsatisfactory. Histone acetylation at H3 lysine 56 (H3K56ac) has been reported to be a tumor suppressor in breast cancer. However, whether H3K56ac prevents the occurrence and development of UM remains uninvestigated. The study aimed to explore the regulatory effect of H3K56ac on Ras-PI3K-AKT induced UM cells proliferation and migration.

METHODS

The vectors of pEGFP-Ras^WT , pEGFP-K-Ras ^G12V/Y40C , and pEGFP-N1 were transfected into MP46 cells, and protein levels of phosphorylated AKT ^Ser473 and H3K56ac were examined using western blot analysis. The effect of H3K56ac on cell proliferation and migration were studied using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide, colony formation, and Transwell assays. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and chromatin immunoprecipitation assays were performed to determine the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) downstream genes. Further, the regulatory effects of silent mating type information regulation 2 homolog-1 (SIRT1), general control nonderepressible 5 (GCN5), and mouse double minute 2 homolog (MDM2) on Ras-PI3K-AKT affected H3K56ac expression were also investigated.

RESULTS

H3K56ac expression was specifically downregulated by Ras-PI3K-AKT activation pathway. H3K56ac inhibited the tumorigenic effect of Ras-PI3K-AKT on MP46 cells viability, colony formation, and migration, as well as participated in regulating the transcription of PI3K/AKT downstream genes. SIRT1 silence recovered H3K56ac expression, and reversed the tumorigenic effect of Ras-PI3K-AKT activation on MP46 cells. Downregulation of H3K56ac induced by Ras-PI3K-AKT activation was found to be associated with MDM2-mediated the degradation of GCN5.

CONCLUSIONS

The results demonstrated that Ras-PI3K-AKT signaling promoted UM cells proliferation and migration via downregulation of H3K56ac expression, which might be related to MDM2-mediated the degradation of GCN5.

Competitive inhibition by NAG-1/GDF-15 NLS peptide enhances its anti-cancer activity

Non-steroidal anti-inflammatory drug activated gene-1 (NAG-1), also known as growth differentiation factor 15 (GDF15), is a TGF-β (transforming growth factor beta) superfamily protein with a distinctive secretion pathway. NAG-1 is associated with multiple diseases including cancer, wherein it plays a role in both pro- and anti-cancer activities. We previously reported that NAG-1 is translocated to different subcellular compartments and its activity depends on its localization. In this paper, we report that the transfection of a novel peptide corresponding to the nuclear localization signal (NLS) of NAG-1 blocks its translocation to the nucleus. Further, accumulation of NAG-1 in the cytoplasm decreased mitochondrial membrane potential, thus implying apoptosis induction as a consequence. Overall, our results indicate that the novel peptide derived from NAG-1 NLS sequence is a promising tool for enhancing the anti-tumorigenic activity of NAG-1.

Growth differentiation factor 15 and its role in carcinogenesis: an update

Growth differentiation factor-15 (GDF-15) is a novel cytokine secreted by a variety of cells like macrophages, adipocytes, normally expressed in high amounts by placenta. It is also highly expressed in multiple carcinomas like Colon, Breast, Pancreas, Liver, and Ovarian. Several reports on serum GDF-15 as a potential biomarker for diagnosis and prognosis of cancer are hampered by the lack of robust data, with large sample size and critical patient recruitment. However, experimental accounts on cancer tumors, cell lines, and animal models suggest GDF-15's role in cancer progression via endothelial mesenchymal transition, angiogenesis, metastasis, drug resistance and even stemness of various cancers. GDF-15 could be the point of amalgamation for the various hallmarks of cancer and can prove a useful therapeutic target in cancer. The current review was conceptualized with a thought of critically appraising the existing information of GDF-15 in carcinogenesis.

Growth differentiation factor 15 (GDF15): A survival protein with therapeutic potential in metabolic diseases

Growth Differentiation Factor 15 (GDF15), also known as NSAID activated gene-1 (NAG-1), is associated with a large number of biological processes and diseases, including cancer and obesity. GDF15 is synthesized as pro-GDF15, is dimerized, and is cleaved and secreted into the circulation as a mature dimer GDF15. Both the intracellular GDF15 and the circulating mature GDF15 are implicated in biological processes, such as energy homeostasis and body weight regulation. Although there have been many studies on GDF15, GFRAL, a member of the glial-derived neurotropic factor receptor α family, has only been recently identified as a receptor for mature GDF15. In this review, we focused on cancer and energy homeostasis along with obesity and body weight, and the effect of the identification of the GDF15 receptor in these investigations. In addition, the therapeutic potential of GDF15 as a pharmacological agent in obesity and other metabolic diseases was discussed.

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.

GDF15 and Growth Control

Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor β (TGF-β) superfamily and is widely expressed in multiple mammalian tissues. Its expression is highly regulated and is often induced in response to conditions associated with cellular stress. GDF15 serum levels have a strong association with many diseases, including inflammation, cancer, cardiovascular diseases, and obesity, and potentially serve as reliable predictor of disease progression. A functional role for GDF15 has been suggested in cancer, cardiovascular disease, kidney disease and metabolic disease. However, the knowledge of its pathophysiological function at the molecular level is still limited and requires more investigation. Recent identification of the endogenous receptor for GDF15 may provide additional insight in to its' molecular mechanisms and relationship to disease states.

Effects of non-steroidal anti-inflammatory drug-activated gene-1 on Ganoderma lucidum polysaccharides-induced apoptosis of human prostate cancer PC-3 cells

Ganoderma lucidum polysaccharides (GLP) has been demonstrated to elicit antitumorigenic and proapoptotic activities in cancer; however, the molecular mechanisms underlying the anticancer effects of GLP have yet to be elucidated. Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) has been reported to exert proapoptotic effects and therefore, may serve an important role in cancer prevention. The present study aimed to elucidate the molecular mechanism by which GLP stimulates anticancer activity in human prostate cancer (PCa) PC-3 cells. In addition, the role of NAG-1 in GLP-induced cancer inhibition was examined. The results of the present study demonstrated that GLP significantly inhibited cell viability in a time- and dose-dependent manner in PC-3 cells. Flow cytometry indicated that GLP induced late apoptosis, which was accompanied by poly (ADP-ribose) polymerase 1 (PARP) cleavage, and inhibition of pro-caspase-3, -6 and -9 protein expression. Furthermore, it was observed that the expression levels of NAG-1, and its transcriptional factor early growth response-1, were upregulated in a time- and dose-dependent manner upon GLP treatment. The results of a luciferase assay demonstrated that GLP induced the promoter activity of NAG-1, thus indicating that NAG-1 may be transcriptionally regulated by GLP. The secretion of NAG-1 proteins into the cell culture medium was also upregulated upon GLP treatment. Furthermore, inhibition of NAG-1 expression by small interfering RNA significantly, but not completely, prevented GLP-induced apoptosis, and reversed the effects of GLP on PARP and pro-caspase expression. It was further demonstrated that GLP inhibited the phosphorylation of protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated kinase signaling in PC-3 cells. The present study is the first, to the best of our knowledge, to report that GLP may induce apoptosis of PCa cells, which is partially mediated through NAG-1 induction. The present findings may be helpful in elucidating the anticancer mechanisms of GLP through NAG-1 induction for its chemopreventive potential in PCa.

The MIC-1/GDF15-GFRAL Pathway in Energy Homeostasis: Implications for Obesity, Cachexia, and Other Associated Diseases

MIC-1/GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFb) superfamily, with no close relatives. It acts via a recently identified receptor called glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which is a distant orphan member of the GDNF receptor family that signals through the tyrosine kinase receptor Ret. MIC-1/GDF15 expression and serum levels rise in response to many stimuli that initiate cell stress and as part of a wide variety of disease processes, most prominently cancer and cardiovascular disease. The best documented actions of MIC-1/GDF15 are on regulation of energy homeostasis. When MIC-1/GDF15 serum levels are substantially elevated in diseases like cancer, it subverts a physiological pathway of appetite regulation to induce an anorexia/cachexia syndrome initiated by its actions on hindbrain neurons. These effects make it a potential target for the treatment of both obesity and anorexia/cachexia syndromes, disorders lacking any highly effective, readily accessible therapies.

The PCAT3/PCAT9-miR-203-SNAI2 axis functions as a key mediator for prostate tumor growth and progression

Long non-coding RNAs (lncRNAs) have been reported to be of great importance in the formation and progression of a wide range of human carcinomas including prostate cancer (PCa). Among them, PCAT3 and PCAT9 have been identified as two prostate tissue-specific lncRNAs and are up-regulated in PCa. However, their roles in the biological characteristics of PCa have not been fully elucidated. In the present study, our data revealed that knockdown of PCAT3 and PCAT9 suppressed cellular proliferation, invasion, migration, angiogenesis and stemness in androgen-dependent LNCaP and 22Rv1 cells. Strikingly, bioinformatics analysis predicted that both PCAT3 and PCAT9 transcripts had two conserved binding sties for miR-203. Meanwhile, dual luciferase report assays revealed that miR-203 could suppress the luciferase activities of reporter plasmids carrying the binding site of miR-203 on the mRNA of PCAT3 or PCAT9. Quantitative RT-PCR (qRT-PCR) and RNA fluorescence in situ hybridization (RNA-FISH) showed that miR-203 mimic reduced the expression of PCAT3 and PCAT9 both in LNCaP and 22Rv1 cells. We also noted that both PCAT3 and PCAT9 inhibited miR-203 expression and alleviated repression on the expression of SNAI2, a critical regulator of epithelial-mesenchymal transition directly targeted by miR-203. Functionally, silence of miR-203 or ectopic expression of SNAI2 attenuated the inhibitory effect of PCAT3 and PCAT9 knockdown on cell proliferation and migration in vitro, and xenograft growth in vivo. Taken together, our data suggested that the PCAT3/PCAT9-miR-203-SNAI2 axis may serve as a promising diagnostic and therapeutic target for PCa.

Macrophage inhibitory cytokine-1/growth differentiation factor-15 as a predictor of colonic neoplasia

BACKGROUND

Serum macrophage inhibitory cytokine-1 (MIC-1/GDF15) concentration has been associated with colonic adenomas and carcinoma.

AIMS

To determine whether circulating MIC-1/GDF15 serum concentrations are higher in the presence of adenomas and whether the level decreases after excision.

METHODS

Patients were recruited prospectively from a single centre and stratified into five groups: no polyps (NP); hyperplastic polyps (HP); sessile serrated ademona (SSA); adenomas (AP); and colorectal carcinoma (CRC). Blood samples were collected immediately before and 4 weeks after colonoscopy. MIC-1/GDF15 serum levels were quantified using ELISA.

RESULTS

Participants (n=301) were stratified as: NP; n=116 (52%), HP; n=37 (12%), SSA; n=19 (7%), AP; n=68 (23%); and CRC; n=3 (1%). Patients were excluded from the study due to nondiagnostic pathology (n=9, 3%) and exclusion criteria (n=20, 6%). In the 272 remaining subjects (M=149; F=123), age (P=.005), history of colonic polyps (P=.003) and family history of colonic polyps (P=.002) were associated with presence of adenomas. Baseline median MIC-1/GDF15 serum levels increased significantly from NP 609 (460-797) pg/mL, HP 582 (466-852) pg/mL, SSA 561 (446-837) pg/mL to AP 723 (602-1122) pg/mL and CRC 1107 (897-1107) pg/mL; (P<.001). In the pre- and postpolypectomy paired adenoma samples median MIC-1/GDF15 reduced significantly from 722 (603-1164) pg/mL to 685 (561-944) pg/mL (P=.002). A ROC analysis for serum MIC-1/GDF15 to identify adenomatous polyps indicated an area under the curve of 0.71.

CONCLUSIONS

Our data suggest that serum MIC-1/GDF15 has the diagnostic characteristics to increase the detection of colonic neoplasia and improve screening.

Inflammation in Prostatic Hyperplasia and Carcinoma-Basic Scientific Approach

Chronic inflammation is associated with both benign conditions and cancer. Likewise, inflammatory cells are quite common in benign prostatic hyperplasia (BPH) and prostatic tissue harboring cancer. Triggers that activate inflammatory pathways in the prostate remain a subject of argument and are likely to be multifactorial, some of these being bacterial antigens, different chemical irritations, and metabolic disorders. Acute and chronic inflammation in prostate leads to accumulation of immunocompetent cells, mainly T lymphocytes and macrophages, but also neutrophils, eosinophils, and mast cells, depending on the type of offending agent. Inflammatory processes activate hyperproliferative programs resulting in nodules seen in BPH, but are also important in creating suitable microenvironment for cancer growth and progression. Inflammatory cells have mostly been shown to have a protumoral effect such as tumor-associated macrophages, but some cell types such as mast cells have antitumoral effects. This review outlines the recent findings and theories supporting the role of inflammatory responses as drivers of both benign and malignant epithelial processes in the prostate gland.

High GDF-15 Serum Levels Independently Correlate with Poorer Overall Survival of Patients with Tumor-Free Stage III and Unresectable Stage IV Melanoma

Biomarkers are strongly needed for diagnostic surveillance of patients with metastatic melanoma. On the basis of its known association with tumor metastasis and its ability to induce cancer cachexia, we investigated serum levels of growth and differentiation factor 15 (sGDF-15) as a marker for overall survival (OS). sGDF-15 was retrospectively measured by ELISA in 761 samples obtained at distinct time points during routine clinical care of patients with stage III/IV melanoma. In the entire cohort, sGDF-15 ≥ 1.5 ng/ml was strongly associated with reduced OS after assessment. Subsequent analyses were performed separately for tumor-free stage III, tumor-free stage IV, and unresectable stage IV patients. For patients with unresectable distant metastasis (n = 206), sGDF-15 was independently associated with OS when considered together with the M-category and superior to serum level of lactate dehydrogenase. Analysis in tumor-free stage III patients during routine surveillance (n = 468) revealed sGDF-15 to be associated with OS and an independent factor when considered together with S100B and the pattern of locoregional metastasis. Only in tumor-free stage IV patients (n = 87) sGDF-15 was not associated with OS. sGDF-15 should thus be further validated as a marker for early detection of recurrence in stage III patients and as a prognostic or predictive marker particularly in the context newly available treatments in unresectable stage IV patients.

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.

Exosomes from the tumor microenvironment as reciprocal regulators that enhance prostate cancer progression

Distant organ metastasis of prostate cancer is a puzzle, and various theories have successively arisen to explain the mechanism of lethal cancer progression. While perhaps agreeable to many cancer biologists, the very statement of "seed and soil" proposed by Stephan Paget in 1881 is arguably still the major statement for organ-specific cancer metastasis. Since recent studies showed important correlations of regulation of cancer cells and the microenvironment, exosomes from cancer and stromal cells seem to create another important niche for metastasis. Stromal cells pretreated with exosomes from metastatic cancer cells increase the potential of change stromal cells. The poorly metastatic cancer cells could also enhance malignancy through transfer of proteins, microribonucleic acid and messenger ribonucleic acid to recipient cancer cells. Herein, we reviewed extracellular exosomes as a factor involved in cross-talk between stromal and prostate cancer epithelial cells.

Methods to Study Metastasis in Genetically Modified Mice

Metastasis is often modeled by xenotransplantation of cell lines in immunodeficient mice. A wealth of information about tumor cell behavior in the new environment is obtained from these efforts. Yet by design, this approach is "tumor-centric," as it focuses on cell-autonomous determinants of human tumor dissemination in mouse tissues, in effect using the animal body as a sophisticated "Petri dish" providing nutrients and support for tumor growth. Transgenic or gene knockout mouse models of cancer allow the study of tumor spread as a systemic disease and offer a complimentary approach for studying the natural history of cancer. This introduction is aimed at describing the overall methodological approach to studying metastasis in genetically modified mice, with a particular focus on using animals with regulated expression of potent human oncogenes in the breast.

Anorexia-cachexia and obesity treatment may be two sides of the same coin: role of the TGF-b superfamily cytokine MIC-1/GDF15

Anorexia-cachexia associated with cancer and other diseases is a common and often fatal condition representing a large area of unmet medical need. It occurs most commonly in advanced cancer and is probably a consequence of molecules released by tumour cells, or tumour-associated interstitial or immune cells. These may then act directly on muscle to cause atrophy and/or may cause anorexia, which then leads to loss of both fat and lean mass. Although the aetiological triggers for this syndrome are not well characterized, recent data suggest that MIC-1/GDF15, a transforming growth factor-beta superfamily cytokine produced in large amounts by cancer cells and as a part of other disease processes, may be an important trigger. This cytokine acts on feeding centres in the hypothalamus and brainstem to cause anorexia leading to loss of lean and fat mass and eventually cachexia. In animal studies, the circulating concentrations of MIC-1/GDF15 required to cause this syndrome are similar to those seen in patients with advanced cancer, and at least some epidemiological studies support an association between MIC-1/GDF15 serum levels and measures of nutrition. This article will discuss its mechanisms of central appetite regulation, and the available data linking this action to anorexia-cachexia syndromes that suggest it is a potential target for therapy of cancer anorexia-cachexia and conversely may also be useful for the treatment of severe obesity.

Plasma Inflammatory Markers and Risk of Advanced Colorectal Adenoma in Women

Evidence remains inconclusive about the association of systemic inflammatory markers with colorectal neoplasia. We investigated whether circulating inflammatory markers were associated with risk of advanced colorectal adenoma. We measured plasma macrophage inhibitory cytokine-1 (MIC-1), C-reactive protein (CRP), interleukin-6 (IL6), and soluble TNF receptor 2 (sTNFR-2) in blood samples drawn from 32,826 women in 1989 to 1990 in the Nurses' Health Study. Through 2008, we documented 757 cases of advanced colorectal adenomas (≥1 cm or any size with advanced histology); each case was matched by age and time of blood draw with one control randomly selected from participants who underwent lower endoscopy and did not have neoplasia. Plasma MIC-1 was associated with higher risk of advanced adenoma (Ptrend = 0.04), with an OR of 1.55 (95% confidence interval, 1.03-2.32) comparing extreme quintiles of MIC-1 after adjusting for colorectal cancer-risk factors and other inflammatory markers. Among cases, MIC-1 level was positively associated with the number of adenomas (P < 0.001) and gradually increased from adenomas located in the rectum, distal colon, and up to the proximal colon. There was a strong positive association between MIC-1 and risk of adenomas with multiplicity, ≥1 cm size and location in the proximal colon (all Ptrend < 0.05). CRP, IL6, or sTNFR-2 was not associated with adenoma risk. In conclusion, plasma MIC-1 was associated with higher risk of colorectal adenoma, especially multiple, large, and proximal adenomas. Our results provide further support for a role for MIC-1 in carcinogenesis and the potential for MIC-1 as an adjunctive biomarker for detection of advanced colorectal adenoma.

Growth differentiation factor 15 as a radiation-induced marker in oral carcinoma increasing radiation resistance

BACKGROUND

Growth differentiation factor 15 (GDF15) is involved in tumor pathogenesis of oral squamous cell carcinoma (OSCC). The aim of this study was an investigation of the potential influence of GDF15 on radioresistance of OSCC cells in vitro.

METHODS

Oral squamous cell carcinoma cell lines were irradiated with 0, 2, or 6 Gy, and GDF15 expression in the supernatant per survived cell colony was examined with ELISA. Non-irradiated and OSCC cell lines irradiated with 6 Gy were evaluated for GDF15 expression using immunofluorescent staining. For further investigation of GDF15 effects on radioresistance, a GDF15 knockdown model in a human OSCC cell line was established, and apoptotic activity after radiation was measured using the Caspase-Glo 3/7 system.

RESULTS

ELISA and immunofluorescent staining indicated an increased GDF15 expression in 5 OSCC cell lines compared with human gingival epithelial cells. Irradiation with two and six gray resulted in a significant elevation of GDF15 expression per survived cell colony in the irradiated OSCC cell lines (P < 0.001). Furthermore, a dose-dependent expression of GDF15 was seen. Immunofluorescent staining confirmed an elevated GDF15 expression in irradiated OSCC cell lines (n = 10; P ≤ 0.001). Apoptotic activity was significantly increased after irradiation in the GDF15 knockdown group compared with control cells (n = 24; P < 0.001).

CONCLUSION

This study describes for the first time the vital role of GDF15 both in tumorigenesis and in radioresistance of OSCC cells. With its anti-apoptotic effects, GDF15 possibly promotes tumor progression and might protect carcinoma cells against irradiation effects. Consequently, GDF15 may be a promising therapeutic target in oral cancer.

Circulating levels of GDF15, MMP7 and miR-200c as a poor prognostic signature in gastric cancer

AIM

To analyze GDF15 and MMP7 serum levels as diagnostic biomarkers in gastric cancer (GC) patients. The prognostic value of GDF15 and MMP7 serum levels in combination with miR-200c blood expression was also analyzed.

PATIENTS & METHODS

Fifty-two GC and 23 control samples were included.

RESULTS

GDF15 and MMP7 proved to be powerful tools for GC diagnosis. Increased levels of GDF15 and MMP7 were associated with shorter progression-free survival and overall survival in univariate analysis. In multivariate analysis, the combination of high levels of GDF15, MMP7 and miR-200c was an independent predictor for death (p = 0.033).

CONCLUSION

GDF15 and MMP7 serum levels have diagnostic value for GC. The combination marker formed by GDF15, MMP7 and miR-200c is indicative of adverse evolution in GC patients.

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.

Evasion of anti-growth signaling: A key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting.

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) gene deletion promotes cancer growth in TRAMP prostate cancer prone mice

The divergent TGF-β superfamily member, macrophage inhibitory cytokine-1 (MIC-1/GDF15), is overexpressed by most cancers, including prostate cancer (PCa). Whilst its circulating levels are linked to cancer outcome, the role MIC-1/GDF15 plays in cancer development and progression is incompletely understood. To investigate its effect on PCa development and spread, we have used TRAMP prostate cancer prone mice bearing a germline deletion of MIC-1/GDF15 (TRAMPMIC-/-). On average TRAMPMIC-/- mice died about 5 weeks earlier and had larger prostatic tumors compared with TRAMP mice that were wild type for MIC-1/GDF15 (TRAMPMIC+/+). Additionally, at the time of death or ethical end point, even when adjusted for lifespan, there were no significant differences in the number of mice with metastases between the TRAMPMIC+/+ and TRAMPMIC-/- groups. However, consistent with our previous data, more than twice as many TRAMP mice overexpressing MIC-1/GDF15 (TRAMPfmsmic-1) had metastases than TRAMPMIC+/+ mice (p<0.0001). We conclude that germ line gene deletion of MIC-1/GDF15 leads to increased local tumor growth resulting in decreased survival consistent with an overall protective role for MIC-1/GDF15 in early primary tumor development. However, in advancing disease, as we have previously noted, MIC-1/GDF15 overexpression may promote local invasion and metastatic spread.

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.

The anorectic actions of the TGFβ cytokine MIC-1/GDF15 require an intact brainstem area postrema and nucleus of the solitary tract

Macrophage inhibitory cytokine-1 (MIC-1/GDF15) modulates food intake and body weight under physiological and pathological conditions by acting on the hypothalamus and brainstem. When overexpressed in disease, such as in advanced cancer, elevated serum MIC-1/GDF15 levels lead to an anorexia/cachexia syndrome. To gain a better understanding of its actions in the brainstem we studied MIC-1/GDF15 induced neuronal activation identified by induction of Fos protein. Intraperitoneal injection of human MIC-1/GDF15 in mice activated brainstem neurons in the area postrema (AP) and the medial (m) portion of the nucleus of the solitary tract (NTS), which did not stain with tyrosine hydroxylase (TH). To determine the importance of these brainstem nuclei in the anorexigenic effect of MIC-1/GDF15, we ablated the AP alone or the AP and the NTS. The latter combined lesion completely reversed the anorexigenic effects of MIC-1/GDF15. Altogether, this study identified neurons in the AP and/or NTS, as being critical for the regulation of food intake and body weight by MIC-1/GDF15.

Local and systemic protumorigenic effects of cancer-associated fibroblast-derived GDF15

The tumor stroma is vital to tumor development, progression, and metastasis. Cancer-associated fibroblasts (CAF) are among the abundant cell types in the tumor stroma, but the range of their contributions to cancer pathogenicity has yet to be fully understood. Here, we report a critical role for upregulation of the TGFβ/BMP family member GDF15 (MIC-1) in tumor stroma. GDF15 was found upregulated in situ and in primary cultures of CAF from prostate cancer. Ectopic expression of GDF15 in fibroblasts produced prominent paracrine effects on prostate cancer cell migration, invasion, and tumor growth. Notably, GDF15-expressing fibroblasts exerted systemic in vivo effects on the outgrowth of distant and otherwise indolent prostate cancer cells. Our findings identify tumor stromal cells as a novel source of GDF15 in human prostate cancer and illustrate a systemic mechanism of cancer progression driven by the tumor microenvironment. Further, they provide a functional basis to understand GDF15 as a biomarker of poor prognosis and a candidate therapeutic target in prostate cancer.

Opposing effects of PI3K/Akt and Smad-dependent signaling pathways in NAG-1-induced glioblastoma cell apoptosis

Nonsteroidal anti-inflammatory drug (NSAID) activated gene-1 (NAG-1) is a divergent member of the transforming growth factor-beta (TGF-β) superfamily. NAG-1 plays remarkable multifunctional roles in controlling diverse physiological and pathological processes including cancer. Like other TGF-β family members, NAG-1 can play dual roles during cancer development and progression by negatively or positively modulating cancer cell behaviors. In glioblastoma brain tumors, NAG-1 appears to act as a tumor suppressor gene; however, the precise underlying mechanisms have not been well elucidated. In the present study, we discovered that overexpression of NAG-1 induced apoptosis in U87 MG, U118 MG, U251 MG, and T98G cell lines via the intrinsic mitochondrial pathway, but not in A172 and LN-229 cell lines. NAG-1 could induce the phosphorylation of PI3K/Akt and Smad2/3 in all six tested glioblastoma cell lines, except Smad3 phosphorylation in A172 and LN-229 cell lines. In fact, Smad3 expression and its phosphorylation were almost undetectable in A172 and LN-229 cells. The PI3K inhibitors promoted NAG-1-induced glioblastoma cell apoptosis, while siRNAs to Smad2 and Smad3 decreased the apoptosis rate. NAG-1 also stimulated the direct interaction between Akt and Smad3 in glioblastoma cells. Elevating the level of Smad3 restored the sensitivity to NAG-1-induced apoptosis in A172 and LN-229 cells. In conclusion, our results suggest that PI3K/Akt and Smad-dependent signaling pathways display opposing effects in NAG-1-induced glioblastoma cell apoptosis.