Samuel N. Breit

Large-scale delineation of secreted protein biomarkers overexpressed in cancer tissue and serum

Genetic alterations in tumor cells often lead to the emergence of growth-stimulatory autocrine and paracrine signals, involving overexpression of secreted peptide growth factors, cytokines, and hormones. Increased levels of these soluble proteins may be exploited for cancer diagnosis and management or as points of therapeutic intervention. Here, we combined the use of controlled vocabulary terms and sequence-based algorithms to predict genes encoding secreted proteins from among ≈12,500 sequences represented on oligonucleotide microarrays. Expression of these genes was queried in 150 carcinomas from 10 anatomic sites of origin and compared with 46 normal tissues derived from the corresponding sites of tumor origin and other body tissues and organs. Of 74 different genes identified as overexpressed in cancer tissues, several encode proteins with demonstrated clinical diagnostic application, such as α-fetoprotein in liver carcinoma, and kallikreins 6 and 10 in ovarian cancer, or therapeutic utility, such as gastrin-releasing peptide/bombesin in lung carcinomas. We show that several of the other candidate genes encode proteins with high levels of tumor-associated expression by immunohistochemistry on tissue microarrays and further demonstrate significantly elevated levels of another novel candidate protein, macrophage inhibitory cytokine 1, a distant member of the tranforming growth factor-β superfamily, in the serum of patients with metastatic prostate, breast, and colorectal carcinomas. Our results suggest that the combination of annotation/protein sequence analysis, transcript profiling, immunohistochemistry, and immunoassay is a powerful approach for delineating candidate biomarkers with potential clinical significance and may be broadly applicable to other human diseases.

GDF15/MIC-1 Functions As a Protective and Antihypertrophic Factor Released From the Myocardium in Association With SMAD Protein Activation

Here we identified growth-differentiation factor 15 (GDF15) (also known as MIC-1), a secreted member of the transforming growth factor (TGF)-&bgr; superfamily, as a novel antihypertrophic regulatory factor in the heart. GDF15 is not expressed in the normal adult heart but is induced in response to conditions that promote hypertrophy and dilated cardiomyopathy. To elucidate the function of GDF15 in the heart, we generated transgenic mice with cardiac-specific overexpression. GDF15 transgenic mice were normal but were partially resistant to pressure overload-induced hypertrophy. Expression of GDF15 in neonatal cardiomyocyte cultures by adenoviral-mediated gene transfer antagonized agonist-induced hypertrophy in vitro. Transient expression of GDF15 outside the heart by intravenous adenoviral delivery, or by direct injection of recombinant GDF15 protein, attenuated ventricular dilation and heart failure in muscle lim protein gene–targeted mice through an endocrine effect. Conversely, examination of Gdf15 gene-targeted mice showed enhanced cardiac hypertrophic growth following pressure overload stimulation. Gdf15 gene-targeted mice also demonstrated a pronounced loss in ventricular performance following only 2 weeks of pressure overload stimulation, whereas wild-type controls maintained function. Mechanistically, GDF15 stimulation promoted activation of SMAD2/3 in cultured neonatal cardiomyocytes. Overexpression of SMAD2 attenuated cardiomyocyte hypertrophy similar to GDF15 treatment, whereas overexpression of the inhibitory SMAD proteins, SMAD6/7, reversed the antihypertrophic effects of GDF15. These results identify GDF15 as a novel autocrine/endocrine factor that antagonizes the hypertrophic response and loss of ventricular performance, possibly through a mechanism involving SMAD proteins.

Tumor-induced anorexia and weight loss are mediated by the TGF-beta superfamily cytokine MIC-1.

Anorexia and weight loss are part of the wasting syndrome of late-stage cancer, are a major cause of morbidity and mortality in cancer, and are thought to be cytokine mediated. Macrophage inhibitory cytokine-1 (MIC-1) is produced by many cancers. Examination of sera from individuals with advanced prostate cancer showed a direct relationship between MIC-1 abundance and cancer-associated weight loss. In mice with xenografted prostate tumors, elevated MIC-1 levels were also associated with marked weight, fat and lean tissue loss that was mediated by decreased food intake and was reversed by administration of antibody to MIC-1. Additionally, normal mice given systemic MIC-1 and transgenic mice overexpressing MIC-1 showed hypophagia and reduced body weight. MIC-1 mediates its effects by central mechanisms that implicate the hypothalamic transforming growth factor-β receptor II, extracellular signal–regulated kinases 1 and 2, signal transducer and activator of transcription-3, neuropeptide Y and pro-opiomelanocortin. Thus, MIC-1 is a newly defined central regulator of appetite and a potential target for the treatment of both cancer anorexia and weight loss, as well as of obesity.

Serum Macrophage Inhibitory Cytokine 1 as a Marker of Pancreatic and Other Periampullary Cancers

Purpose: Patients with pancreatic ductal adenocarcinoma usually present with advanced-stage disease and a dismal prognosis. One effective strategy likely to improve the morbidity and mortality from pancreatic cancer would be the identification of accurate, noninvasive diagnostic markers that would enable earlier diagnosis of symptomatic patients and earlier detection of cancer in asymptomatic individuals at high risk for developing pancreatic cancer. In this study, we evaluated serum macrophage inhibitory cytokine-1 (MIC-1) as a marker of pancreatic cancer. Experimental Design: MIC-1 expression in primary pancreatic cancers, intraductal papillary mucinous neoplasms, and pancreatic cancer cell lines was determined using the National Center for Biotechnology Information serial analysis of gene expression database, oligonucleotide microarrays analysis, in situ hybridization, and immunohistochemistry. Serum MIC-1 levels were determined by ELISA in 80 patients with pancreatic adenocarcinomas, in 30 patients with ampullary and cholangiocellular carcinomas, in 42 patients with benign pancreatic tumors, in 76 patients with chronic pancreatitis, and in 97 healthy control subjects. The diagnostic performance of serum MIC-1 as a marker of pancreatic cancer was compared with that of serum CA19–9. Results: Oligonucleotide microarray and serial analysis of gene expression data demonstrated that MIC-1 RNA levels were higher in primary pancreatic cancers, intraductal papillary mucinous neoplasms, and pancreatic cancer cell lines than in nonneoplastic pancreatic ductal epithelium. MIC-1 expression was localized to the malignant epithelium in pancreatic adenocarcinomas by in situ hybridization. MIC-1 protein was expressed in 14 of 16 primary pancreatic adenocarcinomas (88%) by immunohistochemistry and was also expressed in some pancreata affected by pancreatitis but not in normal pancreas. Serum MIC-1 levels were significantly higher in patients with pancreatic ductal adenocarcinoma (mean ± SD, 2428 ± 2324 pg/ml) and in patients with ampullary and cholangiocellular carcinomas (2123 ± 2387 pg/ml) than in those with benign pancreatic neoplasms (940 ± 469 pg/ml), chronic pancreatitis (1364 ± 1236 pg/ml), or in healthy controls (546 ± 262 pg/ml). An elevated serum MIC-1 (defined as 2 SD above the mean for healthy controls) performed as well as CA19–9 (area under the receiver operating characteristic curve, 0.81 and 0.77, respectively), and the combination of MIC-1 and CA19–9 significantly improved diagnostic accuracy (P < 0.05; area under the receiver operating characteristic curve, 0.87; sensitivity, 70%; specificity, 85%). Conclusion: Serum MIC-1 measurement can aid in the diagnosis of pancreatic adenocarcinoma.

Concentration in plasma of macrophage inhibitory cytokine-1 and risk of cardiovascular events in women: a nested case-control study.

BACKGROUND Macrophage inhibitory cytokine-1 (MIC-1) is part of the TGF-beta superfamily. Raised concentrations of MIC-1 in serum arise in several disease states, can be detected in normal individuals, and can partly be genetically determined. We aimed to investigate whether MIC-1 has a role in atherothrombosis. METHODS We did a prospective, nested, case-control study in 27628 initially healthy women. Of these women, we established baseline concentrations of MIC-1 in 257 who subsequently had myocardial infarction, stroke, or died from a cardiovascular event (cases) and in 257 matched for age and smoking status, who did not report cardiovascular disease during 4-year follow-up (controls). We also assessed polymorphisms in the MIC-1 gene (MIC-1 H and MIC-1 D) in all 514 women. FINDINGS MIC-1 concentrations were higher at baseline in women who subsequently had cardiovascular events than in those who did not (618 vs 538 pg/mL, p=0.0002). Concentrations above the 90th percentile (>856 pg/mL) were associated with a 2.7-fold increase in risk (95% CI 1.6-4.9, p=0.001). This effect was independent of traditional cardiovascular risk factors and at least additive to that of C-reactive protein. There was no significant association between MIC-1 polymorphism and vascular events. INTERPRETATION MIC-1 could be a novel target for cardiovascular disease prevention.

Role of Macrophage Inhibitory Cytokine-1 in Tumorigenesis and Diagnosis of Cancer

Macrophage inhibitory cytokine-1 (MIC-1), a transforming growth factor-beta superfamily cytokine, is involved in tumor pathogenesis, and its measurement can be used as a clinical tool for the diagnosis and management of a wide range of cancers. Although generally considered to be part of the cells antitumorigenic repertoire, MIC-1 secretion, processing, and latent storage suggest a complex, dynamic variability in MIC-1 bioavailability in the tumor microenvironment, potentially modulating tumor progression and invasiveness.

Serum Markers in Patients with Resectable Pancreatic Adenocarcinoma: Macrophage Inhibitory Cytokine 1 versus CA19-9

Purpose: More accurate serum markers of pancreatic cancer could improve the early detection and prognosis of this deadly disease. We compared the diagnostic utility of a panel of candidate serum markers of pancreatic cancer. Experimental Design: We collected preoperative serum from 50 patients with resectable pancreatic adenocarcinoma, as well as sera from 50 patients with chronic pancreatitis and 50 age/sex-matched healthy controls from our institution. Sera were analyzed for the following candidate markers of pancreatic cancer: CA19-9, macrophage inhibitory cytokine 1 (MIC-1), osteopontin, tissue inhibitor of metalloproteinase 1, and hepatocarcinoma-intestine-pancreas protein levels. Results: By logistic regression analysis, MIC-1 and CA19-9 were significant independent predictors of diagnosis. Receiver operating characteristic curve analysis showed that MIC-1 was significantly better than CA19-9 in differentiating patients with pancreatic cancer from healthy controls (area under the curve is 0.99 and 0.78, respectively; P = 0.003), but not in distinguishing pancreatic cancer from chronic pancreatitis (area under the curve of 0.81 and 0.74, respectively; P = 0.63). Hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein, osteopontin, and tissue inhibitor of metalloproteinase 1 serum levels did not provide additional diagnostic power. Conclusion: In the differentiation of patients with resectable pancreatic cancer from controls, serum MIC-1 outperforms other markers including CA19-9.

MIC‐1 is a novel TGF‐β superfamily cytokine associated with macrophage activation

As part of a study to identify novel genes associated with macrophage activation, we have cloned a new member of the transforming growth factor β (TGF‐β) superfamily designated macrophage inhibitory cytokine 1 (MIC‐1). MIC‐1 is synthesized as a 62‐kDa intracellular protein, which, after cleavage by a furin like protease, is secreted as a 25‐kDa disulfide‐linked dimeric protein. Sequence analysis indicates that it does not cluster within any existing TGF‐β families, suggesting it may be the first member of a new grouping within the TGF‐β superfamily. Tissue Northern blots show that MIC‐1 transcripts are only found abundantly in placenta, although smaller amounts are seen in a limited number of other adult and fetal tissues. MIC‐1 is not expressed in resting macrophages but is induced by a number of different activation agents, including phorbol myristate acetate, interleukin 1, tumor necrosis factor α, and macrophage colony‐stimulating factor but not by lipopolysaccharide or interferon‐γ. We have hypothesized that it may be an autocrine inhibitor of macrophage activation but its major biological role is still uncertain. J. Leukoc. Biol. 65: 2–5; 1999.

Anoxia induces macrophage inhibitory cytokine-1 (MIC-1) in glioblastoma cells independently of p53 and HIF-1.

Human astrocytic brain tumors select for mutations in the p53 tumor suppressor gene early in malignant progression. p53 is activated upon various kinds of cellular stress leading to apoptosis or cell cycle arrest, but is also implicated in complex biological processes such as inhibition of angiogenesis and metastasis. In an effort to shed light on consequences mediated by p53 inactivation in gliomas, we established the Tet-On system for p53 in the LN-Z308 glioblastoma cell line. The macrophage inhibitory cytokine-1 (MIC-1) gene was identified as a most prominent p53 target gene upon gene expression profiling. Oxygen deprivation, an important cellular stress, revealed MIC-1 as an anoxia responsive gene in glioblastoma cell lines. MIC-1 up-regulation by anoxia is mediated through an alternative, p53 and hypoxia inducible factor 1 (HIF-1) independent pathway. Furthermore, ectopic expression of MIC-1 in LN-Z308 cell line completely abolished its inherent tumorigenicity in nude mice, while proliferation in vitro was not affected. In the present experimental model MIC-1 may exert its anti-tumorigenic properties via a paracrine mechanism mediated by host cells in vivo. Taken together, these data suggest that MIC-1 is an important downstream mediator of p53 function, while acting itself as an intercessor of cellular stress signaling and exerting anti-tumorigenic activities.

The Intracellular Chloride Ion Channel Protein CLIC1 Undergoes a Redox-controlled Structural Transition*

Most proteins adopt a well defined three-dimensional structure; however, it is increasingly recognized that some proteins can exist with at least two stable conformations. Recently, a class of intracellular chloride ion channel proteins (CLICs) has been shown to exist in both soluble and integral membrane forms. The structure of the soluble form of CLIC1 is typical of a soluble glutathione S-transferase superfamily protein but contains a glutaredoxin-like active site. In this study we show that on oxidation CLIC1 undergoes a reversible transition from a monomeric to a non-covalent dimeric state due to the formation of an intramolecular disulfide bond (Cys-24–Cys-59). We have determined the crystal structure of this oxidized state and show that a major structural transition has occurred, exposing a large hydrophobic surface, which forms the dimer interface. The oxidized CLIC1 dimer maintains its ability to form chloride ion channels in artificial bilayers and vesicles, whereas a reducing environment prevents the formation of ion channels by CLIC1. Mutational studies show that both Cys-24 and Cys-59 are required for channel activity.