Creation of a Peptide Antagonist of the GFRAL-RET Receptor Complex for the Treatment of GDF15-Induced Malaise.

Growth differentiation factor 15 (GDF15) is a contributor to nausea, emesis, and anorexia following chemotherapy via binding to the GFRAL-RET receptor complex expressed in hindbrain neurons. Therefore, GDF15-mediated GFRAL-RET signaling is a promising target for improving treatment outcomes for chemotherapy patients. We developed peptide-based antagonists of GFRAL that block GDF15-mediated RET recruitment. Our initial library screen led to five novel peptides. Surface plasmon resonance and flow cytometric analyses of the most efficacious of this group, termed GRASP, revealed its capacity to bind to GFRAL. In vivo studies in rats revealed that GRASP could attenuate GDF15-induced nausea and anorexia resulting from cisplatin. Combined with Ondansetron, GRASP led to an even greater attenuation of the anorectic effects of cisplatin compared to either agent alone. Our results highlight the beneficial effects of GRASP as an agent to combat chemotherapy-induced malaise. GRASP may also be effective in other conditions associated with elevated levels of GDF15.

Neutralization of GDF15 Prevents Anorexia and Weight Loss in the Monocrotaline-Induced Cardiac Cachexia Rat Model.

Growth and differentiation factor 15 (GDF15) is a cytokine reported to cause anorexia and weight loss in animal models. Neutralization of GDF15 was efficacious in mitigating cachexia and improving survival in cachectic tumor models. Interestingly, elevated circulating GDF15 was reported in patients with pulmonary arterial hypertension and heart failure, but it is unclear whether GDF15 contributes to cachexia in these disease conditions. In this study, rats treated with monocrotaline (MCT) manifested a progressive decrease in body weight, food intake, and lean and fat mass concomitant with elevated circulating GDF15, as well as development of right-ventricular dysfunction. Cotreatment of GDF15 antibody mAb2 with MCT prevented MCT-induced anorexia and weight loss, as well as preserved lean and fat mass. These results indicate that elevated GDF15 by MCT is causal to anorexia and weight loss. GDF15 mAb2 is efficacious in mitigating MCT-induced cachexia in vivo. Furthermore, the results suggest GDF15 inhibition is a potential therapeutic approach to alleviate cardiac cachexia in patients.

Aldehyde-driven transcriptional stress triggers an anorexic DNA damage response.

Endogenous DNA damage can perturb transcription, triggering a multifaceted cellular response that repairs the damage, degrades RNA polymerase II and shuts down global transcription1-4. This response is absent in the human disease Cockayne syndrome, which is caused by loss of the Cockayne syndrome A (CSA) or CSB proteins5-7. However, the source of endogenous DNA damage and how this leads to the prominent degenerative features of this disease remain unknown. Here we find that endogenous formaldehyde impedes transcription, with marked physiological consequences. Mice deficient in formaldehyde clearance (Adh5-/-) and CSB (Csbm/m; Csb is also known as Ercc6) develop cachexia and neurodegeneration, and succumb to kidney failure, features that resemble human Cockayne syndrome. Using single-cell RNA sequencing, we find that formaldehyde-driven transcriptional stress stimulates the expression of the anorexiogenic peptide GDF15 by a subset of kidney proximal tubule cells. Blocking this response with an anti-GDF15 antibody alleviates cachexia in Adh5-/-Csbm/m mice. Therefore, CSB provides protection to the kidney and brain against DNA damage caused by endogenous formaldehyde, while also suppressing an anorexic endocrine signal. The activation of this signal might contribute to the cachexia observed in Cockayne syndrome as well as chemotherapy-induced anorectic weight loss. A plausible evolutionary purpose for such a response is to ensure aversion to genotoxins in food.

GDF15: emerging biology and therapeutic applications for obesity and cardiometabolic disease.

Growth differentiation factor 15 (GDF15) is a member of the TGFß superfamily whose expression is increased in response to cellular stress and disease as well as by metformin. Elevations in GDF15 reduce food intake and body mass in animal models through binding to glial cell-derived neurotrophic factor family receptor alpha-like (GFRAL) and the recruitment of the receptor tyrosine kinase RET in the hindbrain. This effect is largely independent of other appetite-regulating hormones (for example, leptin, ghrelin or glucagon-like peptide 1). Consistent with an important role for the GDF15-GFRAL signalling axis, some human genetic studies support an interrelationship with human obesity. Furthermore, findings in both mice and humans have shown that metformin and exercise increase circulating levels of GDF15. GDF15 might also exert anti-inflammatory effects through mechanisms that are not fully understood. These unique and distinct mechanisms for suppressing food intake and inflammation makes GDF15 an appealing candidate to treat many metabolic diseases, including obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease, cardiovascular disease and cancer cachexia. Here, we review the mechanisms regulating GDF15 production and secretion, GDF15 signalling in different cell types, and how GDF15-targeted pharmaceutical approaches might be effective in the treatment of metabolic diseases.

Silencing of lncRNA PVT1 by miR-214 inhibits the oncogenic GDF15 signaling and suppresses hepatocarcinogenesis.

The prognosis for hepatocellular carcinoma (HCC) is dismal. Long noncoding RNA PVT1 has been linked to malignancies and might be a deleterious therapy target. However, the key events controlling its expression in HCC remain undetermined. Here, we address how PVT1 is fine-regulated and its downstream signaling in hepatoma cells. Interestingly, we found that c-Myc and P53 could divergently regulate PVT1 transcription. Oncoprotein c-Myc enhances PVT1 expression, whereas P53 suppresses its expression. We also identified miR-214 as a crucial, negative regulator of PVT1. Consistently, high miR-214 levels were significantly correlated with diminished PVT1 expression in HCC specimens. Silencing of PVT1 by ectopic miR-214 or siRNAs markedly inhibited viability and invasion of HCC cells. In opposition, inhibition of endogenous miR-214 promoted PVT1 expression and enhanced cell proliferation. Notably, oncogenic GDF15 is a potential downstream target of the miR-214-PVT1 signaling. Collectively, our results show that the c-Myc/P53/miR-214-PVT1-GDF15 axis is implicated in HCC development, shedding light on the mechanistic actions of PVT1 and representing potential targets for HCC clinical intervention.

Targeting the divergent TGFß superfamily cytokine MIC-1/GDF15 for therapy of anorexia/cachexia syndromes.

PURPOSE OF REVIEW: To review recent finding on MIC-1/GDF15 and re-evaluate it as a potential target for the therapy of anorexia/cachexia syndromes. RECENT FINDINGS: MIC-1/GDF15 consistently induces anorexia/cachexia in animal models. Its actions on brainstem feeding centers leads to anorexia, inducing prolonged undernutrition and consequent loss of both lean and fat mass. Epidemiological studies by multiple groups have linked substantially elevated serum levels of this cytokine to anorexia/cachexia syndromes in diverse diseases such as cancer, chronic renal and cardiac failure, and chronic obstructive lung disease. These elevated serum levels are similar to those required to induce this syndrome in animals. Recent identifications of its previously elusive receptor as GFRAL, has enhanced understanding of its biology and suggests that modulating the MIC-1/GDF15-GFRAL pathway may be a therapeutic target for anorexia/cachexia syndrome. SUMMARY: Inhibiting MIC-1/GDF15 or its receptor GFRAL are high-value potential targets for treatment of anorexia/cachexia syndrome in patients whose elevated serum levels may justify its use.

Long noncoding RNA LINC01133 inhibits oral squamous cell carcinoma metastasis through a feedback regulation loop with GDF15.

BACKGROUND AND OBJECTIVES: Long noncoding RNAs (lncRNAs) play key roles in carcinoma metastasis. We aimed to investigate lncRNA LINC01133 in oral squamous cell carcinoma (OSCC) metastasis. METHODS: The RNA levels of LINC01133 and growth and differentiation factor 15 (GDF15) in tissue samples from OSCC patients, and OSCC cell lines were tested by real-time quantitative polymerase chain reaction (RT-qPCR). SPSS20.0 was used to perform statistical analysis of LINC01133 expression in clinical samples and correlate expression of LINC01133 and GDF15. Cell migration/invasion was assessed via transwell assays. Downstream genes of LINC01133 were screened using RNA-seq and validated by RT-qPCR. GDF15 protein levels were evaluated via Western blot analysis. RESULTS: LINC01133 was downregulated in OSCCs; higher expression of LINC01133 in OSCCs was correlated with less metastasis and better prognosis. LINC01133 inhibited OSCC cell migration and invasion. RNA-seq data showed that LINC01133 inhibited GDF15, and GDF15 could rescue inhibition of OSCC cell migration and invasion caused by LINC01133. Interestingly, GDF15 also inhibited LINC01133. Furthermore, a significant negative correlation between expression of LINC01133 and GDF15 was validated in the clinical study. CONCLUSIONS: Collectively, these data indicate that LINC01133 inhibited OSCC metastasis via a feedback regulation loop of reciprocal inhibition with GDF15, suggesting a new diagnostic and therapeutic target for OSCC.

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.

Potentiation of hypericin-mediated photodynamic therapy cytotoxicity by MK-886: focus on ABC transporters, GDF-15 and redox status.

BACKGROUND: Pretreatment with 5-LOX pathway inhibitor MK-886 potentiates cytotoxic effects of photodynamic therapy mediated by natural photosensitizer, hypericin. In this study, we focused on elucidating mechanisms beyond the increased efficacy of combined treatment. METHODS: Metabolic activity/viability, caspase-3 activation/mitochondrial membrane potential dissipation, intracellular hypericin level, glutathione level and redox status (NAD(P)H/oxidized flavins ratio) analyses, as well as drug efflux assays, were performed by flow cytometry. Changes in protein expression of ATP-binding cassette transporters, GDF-15 and other selected proteins were evaluated by Western blotting. Silencing of gdf-15 was carried out to verify its role in response to treatment. RESULTS: MK-886 pretreatment led to a concentration-dependent increase in intracellular hypericin content, accompanied by changes in ATP-binding cassette transporters levels and efflux efficiency. Intracellular accumulation of cytokine GDF-15 correlated with increased cell death markers; however, the impact of gdf-15 silencing on the evaluated markers was negligible. A marked decrease in the glutathione level of a majority of cells was observed after more toxic combination treatment. CONCLUSION: The significant increase in cell death markers after combination treatment confirms the potentiating effect of MK-886 on hypericin-mediated photodynamic therapy in HT-29 and MCF-7 cells. Although BCRP downregulation was not confirmed as leading mechanism responsible for elevated levels of hypericin content, changes in expression and efflux activity of ABC transporters caused by MK-886 suggest its potential in combination treatment with drugs that are substrates of these transporters, predominantly MRP1. However, complex cellular response to MK-886 pretreatment needs to be considered and further elucidated.

Emerging targets to monitor and overcome docetaxel resistance in castration resistant prostate cancer (review).

Drug development for castration resistant prostate cancer (CRPC) is challenging, since this cancer is still associated with high mortality and limited therapeutic options. In 2004, docetaxel became the first-line chemotherapy for CRPC improving survival by a few months and remains the standard of care in CRPC patients. However, existing or developing resistance to docetaxel in patients is the main limitation of its efficacy. The present review presents the molecular mechanisms involved in docetaxel toxicity and in docetaxel resistance in prostate cancer cells. We outlined the endogenous mechanisms of resistance and the role of tumor microenvironment in the resistance of CRPC to docetaxel. This has led us to focus on molecules associated with resistance, such as the molecular chaperones heat shock proteins (HSPs) and clusterin (CLU), and the cytokines interleukin-6 (IL-6) and the divergent member of the tumor growth factor family MIC-1 (macrophage inhibitory cytokine-1 also named GDF-15). We discuss their interest as blood-based markers to monitor docetaxel resistance. Finally, new therapies intended to overcome docetaxel resistance of CRPC targeted on these molecular resistance pathways are present.

Tolfenamic acid induces apoptosis and growth inhibition in anaplastic thyroid cancer: Involvement of nonsteroidal anti-inflammatory drug-activated gene-1 expression and intracellular reactive oxygen species generation.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are usually used for the treatment of inflammatory diseases. However, certain NSAIDs also have antitumor activities in various cancers, including head and neck cancer, through cyclooxygenase-dependent or independent pathways. Nonsteroidal anti-inflammatory drug-activated gene-1 (NAG-1), a TGF-ß superfamily protein, is induced by NSAIDs and has been shown to be induced by several antitumorigenic compounds and to exhibit proapoptotic and antitumorigenic activities. In this report, we demonstrate for the first time that tolfenamic acid (TA) transcriptionally induced the expression of NAG-1 during TA-induced apoptosis of anaplastic thyroid cancer (ATC) cells. TA reduced the viability of ATC cells in a dose-dependent manner and induced apoptosis, findings that were coincident with NAG-1 expression. Overexpression of the NAG-1 gene using cDNA enhanced the apoptotic effect of TA, whereas suppression of NAG-1 expression by small interfering RNA attenuated TA-induced apoptosis. Subsequently, we found that intracellular ROS generation plays an important role in activating the proapoptotic protein NAG-1. Then, we confirmed antitumorigenic effects of TA in a nude mouse orthotopic ATC model, and this result accompanied the augmentation of NAG-1 expression and ROS generation in tumor tissue. Taken together, these results demonstrate that TA induces apoptosis via NAG-1 expression and ROS generation in in vitro and in vivo ATC models, providing a novel mechanistic explanation and indicating a potential chemotherapeutic approach for treatment of ATC.

Inhibitory Effects of Salinomycin on Cell Survival, Colony Growth, Migration, and Invasion of Human Non-Small Cell Lung Cancer A549 and LNM35: Involvement of NAG-1.

A major challenge for oncologists and pharmacologists is to develop more potent and less toxic drugs that will decrease the tumor growth and improve the survival of lung cancer patients. Salinomycin is a polyether antibiotic used to kill gram-positive bacteria including mycobacteria, protozoans such as plasmodium falciparum, and the parasites responsible for the poultry disease coccidiosis. This old agent is now a serious anti-cancer drug candidate that selectively inhibits the growth of cancer stem cells. We investigated the impact of salinomycin on survival, colony growth, migration and invasion of the differentiated human non-small cell lung cancer lines LNM35 and A549. Salinomycin caused concentration- and time-dependent reduction in viability of LNM35 and A549 cells through a caspase 3/7-associated cell death pathway. Similarly, salinomycin (2.5-5 µM for 7 days) significantly decreased the growth of LNM35 and A549 colonies in soft agar. Metastasis is the main cause of death related to lung cancer. In this context, salinomycin induced a time- and concentration-dependent inhibition of cell migration and invasion. We also demonstrated for the first time that salinomycin induced a marked increase in the expression of the pro-apoptotic protein NAG-1 leading to the inhibition of lung cancer cell invasion but not cell survival. These findings identify salinomycin as a promising novel therapeutic agent for lung cancer.

Positive regulation of osteoclastic differentiation by growth differentiation factor 15 upregulated in osteocytic cells under hypoxia.

Osteocytes are thought to play a role as a mechanical sensor through their communication network in bone. Although osteocytes are the most abundant cells in bone, little attention has been paid to their physiological and pathological functions in skeletogenesis. Here, we have attempted to delineate the pivotal functional role of osteocytes in regulation of bone remodeling under pathological conditions. We first found markedly increased osteoclastic differentiation by conditioned media (CM) from osteocytic MLO-Y4 cells previously exposed to hypoxia in vitro. Using microarray and real-time PCR analyses, we identified growth differentiation factor 15 (GDF15) as a key candidate factor secreted from osteocytes under hypoxia. Recombinant GDF15 significantly promoted osteoclastic differentiation in a concentration-dependent manner, with concomitant facilitation of phosphorylation of both p65 and inhibitory-κB in the presence of receptor activator of nuclear factor-κB ligand. To examine the possible functional significance of GDF15 in vivo, mice were subjected to ligation of the right femoral artery as a hypoxic model. A significant increase in GDF15 expression was specifically observed in tibias of the ligated limb but not in tibias of the normally perfused limb. Under these experimental conditions, in cancellous bone of proximal tibias in the ligated limb, a significant reduction was observed in bone volume, whereas a significant increase was seen in the extent of osteoclast surface/bone surface when determined by bone histomorphometric analysis. Finally, the anti-GDF15 antibody prevented bone loss through inhibiting osteoclastic activation in tibias from mice with femoral artery ligation in vivo, in addition to suppressing osteoclastic activity enhanced by CM from osteocytes exposed to hypoxia in vitro. These findings suggest that GDF15 could play a pivotal role in the pathogenesis of bone loss relevant to hypoxia through promotion of osteoclastogenesis after secretion from adjacent osteocytes during disuse and/or ischemia in bone.

Wild-type p53 attenuates cancer cell motility by inducing growth differentiation factor-15 expression.

A major function of the p53 tumor suppressor is the regulation of the cell cycle and apoptosis. In addition to its well-documented functions in malignant cancer cells, p53 can also regulate cell migration and invasion, which contribute to metastasis. Growth differentiation factor-15 (GDF-15), a member of the TGF-ß superfamily, has been shown to be a downstream target of p53 and is associated with diverse human diseases and cancer progression. In this study, we examined the potential role of GDF-15 in p53-regulated cancer cell motility. We show that overexpression of wild-type p53 in two highly invasive p53-null human cancer cell lines, SKOV3 and PC3, attenuated cell migration and the movement through Matrigel. Using wild-type p53 and DNA-binding-deficient p53 mutants, we found that the transcriptional activity of p53 is required in the induction of GDF-15 expression. Cell movement through uncoated and Matrigel-coated transwell decreased in response to treatment with recombinant GDF-15, whereas the cell proliferation was not affected by GDF-15 treatment. Moreover, the induction of GDF-15 expression and secretion by p53 and the reduction in cell movement through Matrigel were diminished by treatment with GDF-15 small interfering RNA. This study demonstrates a mechanism by which p53 attenuates cancer cell motility through GDF-15 expression. In addition, our results indicate that GDF-15 mediates the functions of p53 by autocrine/paracrine action.

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1/GDF15) expression is increased by the histone deacetylase inhibitor trichostatin A.

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) is a putative tumor suppressor whose expression can be increased by drug treatment. Glioblastoma is the most common central nervous system tumor, is associated with high morbidity and mortality, and responds poorly to surgical, chemical, and radiation therapy. The histone deacetylase inhibitors are under current consideration as therapeutic agents in treating glioblastoma. We investigated whether trichostatin A (TSA) would alter the expression of NAG-1 in glioblastoma cells. The DNA demethylating agent 5-aza-dC did not increase NAG-1 expression, but TSA up-regulated NAG-1 expression and acted synergistically with 5-aza-dC to induce NAG-1 expression. TSA indirectly increases NAG-1 promoter activity and increases NAG-1 mRNA and protein expression in the T98G human glioblastoma cell line. TSA also increases the expression of transcription factors Sp-1 and Egr-1. Small interfering RNA experiments link NAG-1 expression to apoptosis induced by TSA. Reporter gene assays, specific inhibition by small interfering RNA transfections, and chromatin immunoprecipitation assays indicate that Egr-1 and Sp-1 mediate TSA-induced NAG-1 expression. TSA also increases the stability of NAG-1 mRNA. TSA-induced NAG-1 expression involves multiple mechanisms at the transcriptional and post-transcriptional levels.