Non-cell-autonomous suppression of tumor growth by RECK in immunocompetent mice.

RECK is a candidate tumor suppressor gene isolated as a gene that induces flat reversion in a cell line transformed by the KRAS oncogene. Since RECK knockout mice die in utero, they are not suitable for studying the effects of RECK on tumor formation. In this study, we found an increased incidence of spontaneous pulmonary adenomas in mice with reduced RECK expression (RECK-Hypo mice). To evaluate the effects of RECK expressed by either tumor cells or host cells on tumor growth, we established a tumorigenic cell line (MKER) from the kidney of a C57BL/6 mouse and performed syngeneic transplantation experiments. Our results indicate that when RECK expression is low in host cells, transplanted MKER cells grow faster and kill the animal more rapidly. Since RECK is required for the formation of proper fibrillin fibers that serve as a tissue reservoir for precursors of TGFß-family cytokines, we assessed the levels of TGFß1 in the peripheral blood. We found a significant increase in TGFß1 in RECK-Hypo mice compared to wild-type mice. We also found that the proportion of FOXP3-positive regulatory T (Treg) cells among splenocytes was higher in RECK-Hypo mice compared to the control mice. Furthermore, the number of FOXP3-positive cells in spontaneous hematopoietic neoplasms in the lungs as well as tumors that formed after MKER transplantation was significantly higher in RECK-Hypo mice compared to the control mice. These findings indicate that RECK-mediated tumor suppression involves a non-cell-autonomous mechanism and that possible roles of TGFß1 and Treg cells in such a mechanism warrant further study.

Reversion-inducing cysteine-rich protein with Kazal motifs and MT1-MMP promote the formation of robust fibrillin fibers.

Fibrillins (FBNs) form mesh-like structures of microfibrils in various elastic tissues. RECK and FBN1 are co-expressed in many human tissues, suggesting a functional relationship. We found that dermal FBN1 fibers show atypical morphology in mice with reduced RECK expression (RECK-Hypo mice). Dermal FBN1 fibers in mice-lacking membrane-type 1-matrix metalloproteinase (MT1-MMP) show a similar atypical morphology, despite the current notion that MT1-MMP (a membrane-bound protease) and RECK (a membrane-bound protease inhibitor) have opposing functions. Our experiments using dermal fibroblasts indicated that RECK promotes pro-MT1-MMP activation, increases cell-associated gelatinase/collagenase activity, and decreases diffusible gelatinase/collagenase activity, while MT1-MMP stabilizes RECK in these cells. Experiments using purified proteins indicate that RECK and its binding partner ADAMTS10 keep the proteolytic activity of MT1-MMP within a certain range. These findings suggest that RECK, ADAMTS10, and MT1-MMP cooperate to support the formation of robust FBN1 fibers.

RECK suppresses interleukin-17/TRAF3IP2-mediated MMP-13 activation and human aortic smooth muscle cell migration and proliferation.

Sustained inflammation and matrix metalloproteinase (MMP) activation contribute to vascular occlusive/proliferative disorders. Interleukin-17 (IL-17) is a proinflammatory cytokine that signals mainly via TRAF3 Interacting Protein 2 (TRAF3IP2), an upstream regulator of various critical transcription factors, including AP-1 and NF-κB. Reversion inducing cysteine rich protein with kazal motifs (RECK) is a membrane-anchored MMP inhibitor. Here we investigated whether IL-17A/TRAF3IP2 signaling promotes MMP-13-dependent human aortic smooth muscle cell (SMC) proliferation and migration, and determined whether RECK overexpression blunts these responses. Indeed, IL-17A treatment induced (a) JNK, p38 MAPK, AP-1, NF-κB, and CREB activation, (b) miR-21 induction, (c) miR-27b and miR-320 inhibition, (d) MMP-13 expression and activation, (e) RECK suppression, and (f) SMC migration and proliferation, all in a TRAF3IP2-dependent manner. In fact, gain of TRAG3IP2 function, by itself, induced MMP-13 expression and activation, and RECK suppression. Furthermore, treatment with recombinant MMP-13 stimulated SMC migration in part via ERK activation. Importantly, RECK gain-of-function attenuated MMP-13 activity without affecting its mRNA or protein levels, and inhibited IL-17A- and MMP-13-induced SMC migration. These results indicate that increased MMP-13 and decreased RECK contribute to IL-17A-induced TRAF3IP2-dependent SMC migration and proliferation, and suggest that TRAF3IP2 inhibitors or RECK inducers have the potential to block the progression of neointimal thickening in hyperplastic vascular diseases.

Generation and characterization of a mouse line carrying Reck-CreERT2 knock-in allele.

Reck encodes a membrane-anchored glycoprotein implicated in the regulation of extracellular metalloproteinases, Notch-signaling, and Wnt7-signaling and shown to play critical roles in embryogenesis and tumor suppression. Precise mechanisms of its actions in vivo, however, remain largely unknown. By homologous recombination, we generated a new Reck allele, ReckCreERT2 (MGI symbol: Reck). This allele is defective in terms of Reck function but expected to induce loxP-mediated recombination in the cells committed to express Reck. Similarity in the expression patterns of the ReckCreERT2 transgene and the endogenous Reck gene was confirmed in five tissues. In the adult hippocampus, induction of Reck expression after transient cerebral ischemia could be demonstrated using this allele. These results indicate the utility of this Cre-driver allele in further studies.

Cleavage of ß-dystroglycan occurs in sarcoglycan-deficient skeletal muscle without MMP-2 and MMP-9.

BACKGROUND: The dystroglycan complex consists of two subunits: extracellular α-dystroglycan and membrane-spanning ß-dystroglycan, which provide a tight link between the extracellular matrix and the intracellular cytoskeleton. Previous studies showed that 43 kDa ß-dystroglycan is proteolytically cleaved into the 30 kDa fragment by matrix metalloproteinases (MMPs) in various non-muscle tissues, whereas it is protected from cleavage in muscles by the sarcoglycan complex which resides close to the dystroglycan complex. It is noteworthy that cleaved ß-dystroglycan is detected in muscles from patients with sarcoglycanopathy, sarcoglycan-deficient muscular dystrophy. In vitro assays using protease inhibitors suggest that both MMP-2 and MMP-9 contribute to the cleavage of ß-dystroglycan. However, this has remained uninvestigated in vivo. METHODS: We generated triple-knockout (TKO) mice targeting MMP-2, MMP-9 and γ-sarcoglycan to examine the status of ß-dystroglycan cleavage in the absence of the candidate matrix metalloproteinases in sarcoglycan-deficient muscles. RESULTS: Unexpectedly, ß-dystroglycan was cleaved in muscles from TKO mice. Muscle pathology was not ameliorated but worsened in TKO mice compared with γ-sarcoglycan single-knockout mice. The gene expression of MMP-14 was up-regulated in TKO mice as well as in γ-sarcoglycan knockout mice. In vitro assay showed MMP-14 is capable to cleave ß-dystroglycan. CONCLUSIONS: Double-targeting of MMP-2 and MMP-9 cannot prevent cleavage of ß-dystroglycan in sarcoglycanopathy. Thus, matrix metalloproteinases contributing to ß-dystroglycan cleavage are redundant, and MMP-14 could participate in the pathogenesis of sarcoglycanopathy.

Prognostic importance of sodium level trajectory in acute heart failure.

Low sodium levels are strongly associated with poor prognosis in acute heart failure (AHF); however, the prognostic impact of the sodium level trajectory overtime has not been determined. A secondary analysis of the AQUAMARINE study in which patients with AHF and renal impairment were randomized to receive either tolvaptan or conventional treatment was performed. Sodium levels were evaluated at the baseline and at 6, 12, 24, and 48 h. We defined 'sodium dipping' as sodium level falling below the baseline level at any time point. The primary endpoint was the combined event of all-cause death and heart failure rehospitalization during follow-up. The analysis included 184 patients with a median follow-up of 21.1 months. Sodium levels more steeply increased during the 48 h in patients without events as compared to sodium levels in patients with events (P = 0.018 in linear-mixed effect model). The sodium dipping group (n = 100; 54.3%) demonstrated significantly less urine output, less body weight reduction, and poorer diuretic response within 48 h compared to the non-dipping group. The sodium dipping group was also significantly associated with a low combined-event-free survival after adjustment for other prognostic factors (HR 1.97; 95% CI 1.06-3.38; P = 0.033). The trajectory of sodium levels during the acute phase is associated with the prognosis of patients with AHF independently of the baseline sodium level.

The Wnt7's Tale: A story of an orphan who finds her tie to a famous family.

The transformation suppressor gene RECK was isolated by cDNA expression cloning (1998), and GPR124/TEM5 was detected as a tumor endothelial marker by differential screening (2000). The importance of Wnt7a/b and Gpr124 in brain angiogenesis was demonstrated by reverse genetics in mice (2008-2010). A series of recent studies using genetically engineered mice and zebrafish as well as luciferase reporter assays in cultured cells led to the discovery of functional interactions among Reck, Gpr124, and Wnt7a/b in triggering canonical Wnt signaling with relevance to embryonic brain angiogenesis and blood-brain barrier formation.

Clinical Effectiveness of Tolvaptan in Patients With Acute Heart Failure and Renal Dysfunction.

BACKGROUND: More efficacious and/or safer decongestive therapy is clearly needed in acute heart failure (AHF) patients complicated by renal dysfunction. We tested the hypothesis that adding tolvaptan, an oral vasopressin-2 receptor antagonist, to conventional therapy with loop diuretics would be more effective treatment in this population. METHODS AND RESULTS: A multicenter, open-label, randomized control trial was performed, and 217 AHF patients with renal dysfunction (estimated glomerular filtration rate 15-60 mL • min(-1) • 1.73 m(-2)) were randomized 1:1 to treatment with tolvaptan (n=108) or conventional treatment (n=109). The primary end point was 48-hour urine volume. The tolvaptan group showed more diuresis than the conventional treatment group (6464.4 vs 4999.2 mL; P <.001) despite significantly lower amounts of loop diuretic use (80 mg vs 120 mg; P <.001). Dyspnea relief was achieved significantly more frequently in the tolvaptan group at all time points within 48 hours except 6 hours after enrollment. The rate of worsening of renal function (≥0.3 mg/dL increase from baseline) was similar between the tolvaptan and conventional treatment groups (24.1% vs 27.8%, respectively; P =.642). CONCLUSIONS: Adding tolvaptan to conventional treatment achieved more diuresis and relieved dyspnea symptoms in AHF patients with renal dysfunction. CLINICAL TRIAL REGISTRATION: URL: http://www.umin.ac.jp/ctr/index/htm/ Unique identifier: UMIN000007109.

Nras loss induces metastatic conversion of Rb1-deficient neuroendocrine thyroid tumor.

Mutations in the gene encoding the retinoblastoma tumor suppressor predispose humans and mice to tumor development. Here we have assessed the effect of Nras loss on tumor development in Rb1 heterozygous mice. Loss of one or two Nras alleles is shown to significantly reduce the severity of pituitary tumors arising in Rb1(+/-) animals by enhancing their differentiation. By contrast, C-cell thyroid adenomas occurring in Rb1(+/-) mice progress to metastatic medullary carcinomas after loss of Nras. In Rb1(+/-)Nras(+/-) animals, distant medullary thyroid carcinoma metastases are associated with loss of the remaining wild-type Nras allele. Loss of Nras in Rb1-deficient C cells results in elevated Ras homolog family A (RhoA) activity, and this is causally linked to the invasiveness and metastatic behavior of these cells. These findings suggest that the loss of the proto-oncogene Nras in certain cellular contexts can promote malignant tumor progression.

[Isolation and applications of transformation suppressor genes].

A common strategy to identify tumor suppressor genes has been positional cloning, taking advantages of chromosomal abnormalities, linkage to polymorphic markers, etc. We have been taking another approach, based on shotgun cloning with cDNA-expression library, to isolate genes suppressing an aspect of transformed phenotypes. Genes identified in such an artificial system, however, require subsequent validation for their clinical relevance through independent approaches, such as finding mutations and altered expression in human cancers. Whether the parental genes act as oncogenes or tumor suppressors needs to be deduced from available annotations and/or new experimental data. Once validated, such genes, being isolated by virtue of their biological activities, are likely to be useful in developing new strategies for tumor prognosis, tumor stratification, and drug discovery.