Possible involvement of transforming growth factor-beta 1 and transforming growth factor-beta receptor type II during luteinization in the marmoset ovary

The expression of transforming growth factor-beta 1 (TGF-beta 1), and transforming growth factor-beta receptor type II (T beta R-II), were evaluated in periovulatory marmoset ovaries. Histochemical methods were used, in particular double-labelling techniques, in order to correlate growth factor/receptor expression with proliferation (Ki 67), apoptosis (TUNEL method) and luteinization (3 beta-hydroxysteroid dehydrogenase (3 beta-HSD)). The latter was used as a luteinization marker. Periovulatory ovaries are especially suited for studying all aspects since they typically consist of small non-luteinized follicles, large luteinizing follicles and corpora lutea accessoria (Clas), which have developed from large luteinizing follicles. TGF-beta 1 and T beta R-II expression was found in luteinizing theca cells of large periovulatory follicles and in all luteal cells of Clas. Non-luteinized theca cells, including those of small follicles were always devoid of any immunostaining. Granulosa cells of small follicles were immunopositive for T beta R-II. Large follicles with granulosa cell immunoreactivity of both antibodies coexisted with non-reactive follicles of comparable size. The highest activity of the luteal marker enzyme 3 beta-HSD was co-localized in the same cells that expressed TGF-beta 1 and T beta R-II. The double-labelling experiments revealed that TGF-beta 1 and T beta R-II expression is not correlated with proliferation or apoptosis of follicular cells. Our results indicate that TGF-beta 1 and T beta R-II participate in differentiation processes, i.e. luteinization, rather than proliferation. In particular, the dynamics of T beta R-II expression appear highly related to the process of luteinization.     

Induction of angiogenesis by expression of soluble type II transforming growth factor-beta receptor in mouse hepatoma.

The biological effect of transforming growth factor-beta (TGF-beta) is cell type-specific and complex. The precise role of TGF-beta is not clear in vivo. To elucidate the regulation mechanism of endogenous TGF-beta on hepatoma progression, we modified the MH129F mouse hepatoma cell with a retroviral vector encoding the extracellular region of type II TGF-beta receptor (TRII). Soluble TRII (TRIIs) blocked TGF-beta binding to TRII on the membrane of hepatoma cells. Growth of MH129F cells was inhibited by TGF-beta1 treatment; however, soluble TRII-overexpressing cells (MH129F/TRIIs) did not show any change in proliferation after TGF-beta1 treatment. MH129F/TRIIs cells also increased vascular endothelial growth factor (VEGF) expression, endothelial cell migration, and tube formation. Implantation of MH129F/TRIIs cells into C3H/He mice showed the significantly enhanced tumor formation. According to Western blot and protein kinase C assay, the expression of VEGF, KDR/flk-1 receptor, and endothelial nitric-oxide synthase was enhanced, and the phosphorylation activity of protein kinase C was increased up to 3.7-fold in MH129F/TRIIs tumors. Finally, a PECAM-1-stained intratumoral vessel was shown to be 4.2-fold higher in the MH129F/TRIIs tumor. These results indicate that VEGF expression is up-regulated by a blockade of endogenous TGF-beta signaling in TGF-beta-sensitive hepatoma cells and then stimulates angiogenesis and tumorigenicity. Therefore, we suggest that endogenous TGF-beta is a major regulator of the VEGF/flk-1-mediated angiogenesis pathway in hepatoma progression.     

Inhibition of transforming growth factor-beta type II receptor signaling accelerates tooth formation in mouse first branchial arch explants.

Members of the transforming growth factor-beta (TGF-beta) superfamily signal through their cognate receptors to determine cell phenotypes during embryogenesis. Our previous studies on the regulation of first branchial arch morphogenesis have identified critical components of a hierarchy of different TGF-beta isoforms and their possible functions in regulating tooth and cartilage formation during mandibular morphogenesis. Here we tested the hypothesis that TGF-beta type II receptor (TGF-beta IIR) is a critical component in the TGF-beta signaling pathway regulating tooth formation. To establish the precise location of TGF-beta ligand and its cognate receptor, we first performed detailed analyses of the localization of both TGF-beta2 and TGF-beta IIR during initiation and subsequent morphogenesis of developing embryonic mouse tooth organs. A possible autocrine functional role for TGF-beta and its cognate receptor (TGF-beta IIR) was inferred due to the temporal and spatial localization patterns during the early inductive stages of tooth morphogenesis. Second, loss of function of TGF-beta IIR in a mandibular explant culture model resulted in the acceleration of tooth formation to the cap stage while the mandibular explants in the control group only showed bud stage tooth formation. In addition, there was a significant increase in odontogenic epithelial cell proliferation following TGF-beta IIR abrogation. These results demonstrate, for the first time, that abrogation of the TGF-beta IIR stimulates embryonic tooth morphogenesis in culture and reverses the negative regulation of endogenous TGF-beta signaling upon enamel organ epithelial cell proliferation.     

Predominant intracellular localization of the type I transforming growth factor-beta receptor and increased nuclear accumulation after growth arrest

Transforming growth factor-beta (TGF-beta) signaling requires the functional interaction of two distinct receptors, type I (RI) and type II (RII), at the cell surface. Exposure of cells to TGF-beta results in receptor internalization and down-regulation (Zwaagstra et al., 1999, Exp. Cell Res. 252, 352362); however, little is known about the subsequent fate of RI or RII. In this study the cellular distribution of RI was examined in cells before and after treatment with ligand. RI was localized by immunocytochemistry and confocal microscopy using two polyclonal antisera directed against two different epitopes, one in the C-terminal region and one in the N-terminal region of the cytoplasmic domain. The majority of RI molecules in untreated MvlLu and A549 cells were found to be intracellular. Treatment of MvlLu and A549 cells with 100 pM TGF-beta1 for 24 h at 37 degrees C caused a redistribution of surface RI on MvlLu cells, as evidenced by surface RI aggregation. Unexpectedly, this TGF-beta1 treatment also caused redistribution and accumulation of intracellular RI in and around the nucleus for both MvlLu and A549 cells. Nuclear accumulation of RI was also promoted independently of ligand receptor activation by treatment of MvlLu cells with olomoucine, an agent that results in growth arrest. The capacity of RI to localize in the nucleus was confirmed by microscopic examination of 293 cells transiently expressing RI fused to green fluorescent protein (RI-GFP). Olomoucine treatment of these cells resulted in the movement of RI-GFP into the nucleus. Our results indicate that growth arrest alters intracellular transport/routing of RI and may indicate that RI functions not only at the cell surface but inside the cell as well.     

Epithelium-dependent extracellular matrix synthesis in transforming growth factor-beta 1-growth-inhibited mouse mammary gland

Exogenous transforming growth factor beta (TGF-beta 1) was shown in earlier studies to reversibly inhibit mouse mammary ductal growth. Using small plastic implants to treat regions of developing mammary glands in situ, we now report that TGF-beta 1 growth inhibition is associated with an ectopic accumulation of type I collagen messenger RNA and protein, as well as the glycosaminoglycan, chondroitin sulfate. Both macromolecules are normal components of the ductal extracellular matrix, which, under the influence of exogenous TGF-beta 1, became unusually concentrated immediately adjacent to the epithelial cells at the tip of the ductal growth points, the end buds. Stimulation of extracellular matrix was confined to aggregations of connective tissue cells around affected end buds and was not present around the TGF-beta 1 implants themselves, indicating that the matrix effect was epithelium dependent. Ectopic matrix synthesis was specific for TGF-beta 1 insofar as it was absent at ducts treated with other growth inhibitors, or at ducts undergoing normal involution in response to endogenous regulatory processes. These findings are consistent with the matrix-stimulating properties of TGF-beta 1 reported for other systems, but differ in their strict dependence upon epithelium. A possible role for endogenous TGF-beta 1 in modulating a mammary epithelium-stroma interaction is suggested.     

Cellular distribution of type I and type II receptors for transforming growth factor-beta

Affinity labeling of target cells for transforming growth factor-beta (TGF beta) by cross-linking with 125I-TGF beta via disuccinimidyl suberate or by the photoreactive analogue 4-azidobenzoyl-125I-TGF beta has revealed the presence of multiple TGF beta receptor forms. Two distinct types of TGF beta receptors can be distinguished based on structural analysis of the 125I-TGF beta-labeled species by peptide mapping. Type I TGF beta receptors include the 280-kilodalton labeled receptor form previously found to be the subunit of a disulfide-linked TGF beta receptor complex. (Massagué, J. (1985) J. Biol. Chem. 260, 7059-7066), as well as a 65-kDa labeled receptor form present in all cell lines examined, and a 130-140-kDa labeled receptor form detected only in 3T3-L1 cells. The 280-kDa form is the major TGF beta receptor species in most cell lines examined, but is apparently absent in rat skeletal muscle myoblasts. Type I TGF beta receptors bind TGF beta with an apparent Kd of 50-500 pM. Type II TGF beta receptors include an 85-kDa labeled receptor form present in all mammalian cells examined and a 110-kDa labeled receptor form present in chick embryo fibroblasts. Type II TGF beta receptors bind TGF beta with an apparent Kd of about 50 pM. Except for the 280-kDa type I TGF beta receptor form, none of the TGF beta receptor forms described here is found as part of a disulfide-linked receptor complex. All the TGF beta receptor forms described here behave as intrinsic membrane proteins exposed on the surface of intact cells.     

Interactions of high affinity insulin-like growth factor-binding proteins with the type V transforming growth factor-beta receptor in mink lung epithelial cells

High affinity insulin-like growth factor-binding proteins (IGFBP-1 to -6) are a family of structurally homologous proteins that induce cellular responses by insulin-like growth factor (IGF)-dependent and -independent mechanisms. The IGFBP-3 receptor, which mediates the IGF-independent growth inhibitory response, has recently been identified as the type V transforming growth factor-beta receptor (TbetaR-V) (Leal, S. M., Liu, Q. L., Huang, S. S., and Huang, J. S. (1997) J. Biol. Chem. 272, 20572-20576). To characterize the interactions of high affinity IGFBPs with TbetaR-V, mink lung epithelial cells (Mv1Lu cells) were incubated with 125I-labeled recombinant human IGFBPs (125I-IGFBP-1 to -6) in the presence of the cross-linking agent disuccinimidyl suberate and analyzed by 5% SDS-polyacrylamide gel electrophoresis and autoradiography. 125I-IGFBP-3, -4, and -5 but not 125I-IGFBP-1, -2, and -6 bound to TbetaR-V as demonstrated by the detection of the approximately 400-kDa 125I-IGFBP.TbetaR-V cross-linked complex in the cell lysates and immunoprecipitates. The analyses of 125I-labeled ligand binding competition and DNA synthesis inhibition revealed that IGFBP-3 was a more potent ligand for TbetaR-V than IGFBP-4 or -5. Most of the high affinity 125I-IGFBPs formed dimers at the cell surface. The cell-surface dimer of 125I-IGFBP-3 preferentially bound to and was cross-linked to TbetaR-V in the presence of disuccinimidyl suberate. IGFBP-3 did not stimulate the cellular phosphorylation of Smad2 and Smad3, key transducers of the transforming growth factor-beta type I/type II receptor (TbetaR-I.TbetaR-II) heterocomplex-mediated signaling. These results suggest that IGFBP-3, -4, and -5 are specific ligands for TbetaR-V, which mediates the growth inhibitory response through a signaling pathway(s) distinct from that mediated by the TbetaR-I and TbetaR-II heterocomplex.     

A unique element in the cytoplasmic tail of the type II transforming growth factor-beta receptor controls basolateral delivery

Transforming growth factor (TGF)-beta receptors stimulate diverse signaling processes that control a wide range of biological responses. In polarized epithelia, the TGFbeta type II receptor (T2R) is localized at the basolateral membranes. Sequential cytoplasmic truncations resulted in receptor missorting to apical surfaces, and they indicated an essential targeting element(s) near the receptor's C terminus. Point mutations in the full-length receptor confirmed this prediction, and a unique basolateral-targeting region was elucidated between residues 529 and 538 (LTAxxVAxxR) that was distinct, but colocalized within a clinically significant signaling domain essential for TGFbeta-dependent activation of the Smad2/3 cascade. Transfer of a terminal 84 amino-acid fragment, containing the LTAxxVAxxR element, to the apically sorted influenza hemagglutinin (HA) protein was dominant and directed basolateral HA expression. Although delivery to the basolateral surfaces was direct and independent of any detectable transient apical localization, fluorescence recovery after photobleaching demonstrated similar mobility for the wild-type receptor and a missorted mutant lacking the targeting motif. This latter finding excludes the possibility that the domain acts as a cell membrane retention signal, and it supports the hypothesis that T2R sorting occurs from an intracellular compartment.     

Bone morphogenetic proteins signal through the transforming growth factor-beta type III receptor

The bone morphogenetic protein (BMP) family, the largest subfamily of the structurally conserved transforming growth factor-beta (TGF-beta) superfamily of growth factors, are multifunctional regulators of development, proliferation, and differentiation. The TGF-beta type III receptor (TbetaRIII or betaglycan) is an abundant cell surface proteoglycan that has been well characterized as a TGF-beta and inhibin receptor. Here we demonstrate that TbetaRIII functions as a BMP cell surface receptor. TbetaRIII directly and specifically binds to multiple members of the BMP subfamily, including BMP-2, BMP-4, BMP-7, and GDF-5, with similar kinetics and ligand binding domains as previously identified for TGF-beta. TbetaRIII also enhances ligand binding to the BMP type I receptors, whereas short hairpin RNA-mediated silencing of endogenous TbetaRIII attenuates BMP-mediated Smad1 phosphorylation. Using a biologically relevant model for TbetaRIII function, we demonstrate that BMP-2 specifically stimulates TbetaRIII-mediated epithelial to mesenchymal cell transformation. The ability of TbetaRIII to serve as a cell surface receptor and mediate BMP, inhibin, and TGF-beta signaling suggests a broader role for TbetaRIII in orchestrating TGF-beta superfamily signaling.     

Isolation and characterization of a transforming growth factor-beta Type II receptor cDNA from Xenopus laevis

Transforming Growth Factor-beta (TGF-beta) and their receptors have been characterized from many organisms. Two TGF-beta signaling receptors called Type I and II have been described for various ligands of the superfamily from organisms ranging from Drosophila to humans. In Xenopus laevis, TGF-beta2 and 5 have been reported and presumably, play important roles during early development. Several Type I and type II receptors for many ligands of the TGF-beta superfamily except TGF-beta type II receptor (TbetaIIR), have been characterized in Xenopus laevis. A chemical cross linking experiment using iodinated TGF-beta1 and -beta5, revealed four specific binding proteins on XTC cells. In order to understand the TGF-beta involvement during Xenopus development, a TGF-beta type II receptor (XTbetaIIR) has been isolated from a XTC cDNA library. XTbetaIIR was a partial cDNA lacking a portion of the signal peptide. The sequence analysis and homology comparison with the human TbetaIIR revealed 67% amino acid similarity in the extra cellular domain, 60% similarity in the transmembrane domain and 87% similarity in the cytoplasmic kinase domain, suggesting that XTbetaIIR is a putative TGF-beta type II receptor. In addition, the consensus amino acid motif for serine threonine receptor kinases was also present. Further, a dominant negative expression construct lacking the cytoplasmic kinase domain (engineered with the signal peptide from human TGF-beta type II receptor), was able to abolish TGF-beta mediated induction of a luciferase reporter plasmid, in a transient cell transfection assay. This substantiates the notion that XTbetaIIR cDNA can act as a receptor for TGF-beta. RT-PCR analysis using RNA isolated from various developmental stages of Xenopus laevis revealed expression of this gene in all the early stages of development and in the adult organs, except in stages 46/48.     

Adenovirus-mediated transmission of a dominant negative transforming growth factor-beta receptor inhibits in vitro mouse cranial suture fusion

Recent studies have implicated the transforming growth factor (TGF)-beta family in the regulation of pathological sporadic cranial suture fusion. In addition, these studies have shown that TGF-beta is highly expressed by the dura mater underlying fusing murine cranial sutures. The purpose of the present experiments was to analyze the effects of disrupting TGF-beta signaling during programmed mouse cranial suture fusion. Using recombinant DNA technology, a replication-deficient adenovirus encoding a defective TGF-beta receptor (Ad.DN-TbetaRII) capable of blocking TGF-beta biological activity was constructed. Mouse posterior frontal sutures were harvested before the initiation of suture fusion (postnatal day 25), and the dura mater underlying the suture was infected with vehicle, Ad.DN-TbetaRII, or control virus (Ad.LacZ; n = 10 each). Sutures were cultured for 14 or 30 days in an organ culture system and analyzed macroscopically and histologically.X-gal staining of Ad.LacZ-infected sutures 14 days after culture revealed strong staining of cells localized to the dura mater. Macroscopic analysis revealed complete sutural fusion in vehicle and Ad.LacZ-infected sutures. In contrast, Ad.DN-TBRII-infected sutures demonstrated nearly complete patency. Histological analysis confirmed our macroscopic observations with sutural fusion in 81.3 +/- 10 percent and 74.5 +/- 9 percent of vehicle and Ad.LacZ-infected sutures, respectively, versus 38.1 +/- 12 percent (p < 0.001) in Ad.DN-TbetaRII-infected sutures. In addition, transfection with the Ad.DN-TbetaRII virus resulted in a significant attenuation of anterior-to-posterior suture fusion, with the majority of fused sections localized to anterior sections. These data strongly implicate TGF-beta biological activity in the dura mater underlying the posterior frontal suture in the regulation of programmed sutural fusion. In addition, this study demonstrates the utility of adenovirus-mediated gene transfer in preventing programmed sutural fusion.     

The mannose 6-phosphate/insulin-like growth factor-II receptor is a substrate of type V transforming growth factor-beta receptor.

The type V transforming growth factor beta (TGF-beta) receptor (TbetaR-V) is a ligand-stimulated acidotropic Ser-specific protein kinase that recognizes a motif of SXE/S(P)/D. This motif is present in the cytoplasmic domain of the mannose 6-phosphate/insulin-like growth factor-II (Man-6-P/IGF-II) receptor. We have explored the possibility that the Man-6-P/IGF-II receptor is a substrate of TbetaR-V. Purified bovine Man-6-P/IGF-II receptor was phosphorylated by purified bovine TbetaR-V in the presence of [gamma-32P]ATP and MnCl2 with an apparent Km of 130 nM. TGF-beta stimulated the phosphorylation of the Man-6-P/IGF-II receptor at 0 degrees C in mouse L cells overexpressing the Man-6-P/IGF-II receptor and in wild-type mink lung epithelial (Mv1Lu cells) metabolically labeled with [32P]orthophosphate. The in vitro and in vivo phosphorylation of the Man-6-P/IGF-II receptor occurred at the putative phosphorylation sites as revealed by phosphopeptide mapping and amino acid sequence analysis. TGF-beta stimulated Man-6-P/IGF-II receptor-mediated uptake (approximately 2-fold after 12 h treatment) of exogenous beta-glucuronidase in Mv1Lu cells and type II TGF-beta receptor (TbetaR-II)-defective mutant cells (DR26 cells) but not in type I TGF-beta receptor (TbetaR-I)-defective mutant cells (R-1B cells) and human colorectal carcinoma cells (RII-37 cells) expressing TbetaR-I and TbetaR-II but lacking TbetaR-V. These results suggest the Man-6-P/IGF-II receptor serves as an in vitro and in vivo substrate of TbetaR-V and that both TbetaR-V and TbetaR-I may play a role in mediating the TGF-beta-stimulated uptake of exogenous beta-glucuronidase.     

Epidermal growth factor up-regulates transforming growth factor-beta receptor type II in human dermal fibroblasts via p38 mitogen-activated protein kinase pathway

TGF-beta receptors (TbetaRs) are serine/threonine kinase receptors that bind to TGF-beta and propagate intracellular signaling through Smad proteins. TbetaRs are repressed in some human cancers and expressed at high levels in several fibrotic diseases. We demonstrated that epidermal growth factor (EGF) up-regulates type II TGF-beta receptor (TbetaRII) expression in human dermal fibroblasts. EGF-mediated induction of TbetaRII expression was inhibited by the treatment of fibroblasts with a specific p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580, whereas MEK inhibitor PD98059 did not block the up-regulation of TbetaRII by EGF. EGF induced the TbetaRII promoter activity, and this induction was significantly blocked by SB203580, but not by PD98059. The overexpression of the dominant negative form of p38alpha or p38beta significantly reduced the induction of TbetaRII promoter activity by EGF. These results indicate that the EGF-mediated induction of TbetaRII expression involves the p38 MAPK signaling pathway. The EGF-mediated induction of TbetaRII expression may participate in a synergistic interplay between EGF and TGF-beta signaling pathway.     

Altered structure of the hybrid cell surface proteoglycan of mammary epithelial cells in response to transforming growth factor-beta

Transforming growth factor beta (TGF-beta) is a polypeptide growth factor that affects the accumulation of extracellular matrix by many cell types. We have examined the ability of mouse mammary epithelial (NMuMG) cells to respond to TGF-beta and assessed the effect of the growth factor on the expression of their cell surface heparan sulfate/chondroitin sulfate hybrid proteoglycan. NMuMG cells respond maximally to 3 ng/ml TGF-beta and the response is consistent with occupancy of the type III receptor. However, cells that are polarized, as shown by sequestration of the cell surface PG at their basolateral surfaces, must have the growth factor supplied to that site for maximal response. Immunological quantification of proteoglycan core protein on treated cells suggests that the cells have an unchanging number of this proteoglycan at their cell surface. Nonetheless, metabolic labeling with radiosulfate shows a approximately 2.5-fold increase in 35SO4-glycosaminoglycans in this proteoglycan fraction, defined either by its lipophilic, antigenic, or cell surface properties. Kinetic studies indicate that the enhanced radiolabeling is due to augmented synthesis, rather than slower degradation. Analysis of the glycosaminoglycan composition of the proteoglycan shows an increased amount of chondroitin sulfate, suggesting that the increased labeling per cell may be attributed to an augmented synthesis of chondroitin sulfate glycosaminoglycan on the core protein that also bears heparan sulfate, thus altering the proportions of these two glycosaminoglycans on this hybrid proteoglycan. We conclude that TGF-beta may affect NMuMG cell behavior by altering the structure and thus the activity of this proteoglycan.     

Overexpression of human transforming growth factor-beta1 using a recombinant CHO cell expression system

Transforming growth factor-beta1 (TGF-beta1) is secreted by most cells as a high molecular weight latent complex, which consists of latent TGF-beta1 disulfide bonded to latent TGF-beta1-binding protein (LTBP). Current recombinant expression systems yield less than 1-2 mg of the mature TGF-beta1 per liter of cell culture medium. In an effort to produce large quantities of the recombinant cytokine for structural studies, we have constructed a mammalian expression system based on a modified pcDNA3.1(+) vector with a glutamine synthetase gene inserted for gene amplification. The leader peptide of TGF-beta1 was replaced with that of rat serum albumin, and an eight-histidine tag was inserted immediately after the leader sequence to facilitate protein purification. In addition, Cys 33 of TGF-beta1, which forms a disulfide bond with LTBP, was replaced by a serine residue. The resulting expression construct produced a stable clone expressing 30 mg of mature TGF-beta1 per liter of spent medium. Purified TGF-beta1 bound with high affinity to its type II receptor with a solution dissociation constant of approximately 70 nM, and was fully active in both a Mv1Lu cell growth inhibition assay and in a PAI-1 luciferase reporter assay. Owing to similarities in the synthesis, secretion, and structure of TGF-beta family members, this recombinant expression system may also be applied to the overexpression of other TGF-beta isomers and even to members of the TGF-beta superfamily to facilitate their preparation.     

Mesodermal deletion of transforming growth factor-beta receptor II disrupts lung epithelial morphogenesis: cross-talk between TGF-beta and Sonic hedgehog pathways

In vertebrates, Sonic hedgehog (Shh) and transforming growth factor-beta (TGF-beta) signaling pathways occur in an overlapping manner in many morphogenetic processes. In vitro data indicate that the two pathways may interact. Whether such interactions occur during embryonic development remains unknown. Using embryonic lung morphogenesis as a model, we generated transgenic mice in which exon 2 of the TbetaRII gene, which encodes the type II TGF-beta receptor, was deleted via a mesodermal-specific Cre. Mesodermal-specific deletion of TbetaRII (TbetaRII(Delta/Delta)) resulted in embryonic lethality. The lungs showed abnormalities in both number and shape of cartilage in trachea and bronchi. In the lung parenchyma, where epithelial-mesenchymal interactions are critical for normal development, deletion of mesenchymal TbetaRII caused abnormalities in epithelial morphogenesis. Failure in normal epithelial branching morphogenesis in the TbetaRII(Delta/Delta) lungs caused cystic airway malformations. Interruption of the TbetaRII locus in the lung mesenchyme increased mRNA for Patched and Gli-1, two downstream targets of Shh signaling, without alterations in Shh ligand levels produced in the epithelium. Therefore, we conclude that TbetaRII-mediated signaling in the lung mesenchyme modulates transduction of Shh signaling that originates from the epithelium. To our knowledge, this is the first in vivo evidence for a reciprocal and novel mode of cross-communication between Shh and TGF-beta pathways during embryonic development.     

Restoration of transforming growth factor-beta type II receptor reduces tumorigenicity in the human adrenocortical carcinoma SW-13 cell line.

Transforming growth factor-beta (TGF-beta) is a potent growth suppressor. Acquisition of TGF-beta resistance has been reported in many tumors, and has been associated with reduced TGF-beta receptor expression. In this study, we examined TGF-beta 1, TGF-beta type I receptor (TbetaRI) and TGF-beta type II receptor (TbetaRII) expression in SW-13 adrenocortical carcinoma cells by Northern and Western blot analysis. SW-13 cells did not express TbetaRII mRNA or protein. We have investigated the role of TbetaRII in modulating tumorigenic potential using stably transfected SW-13 cells with TbetaRII expression plasmid. TbetaRII-positive SW-13 cell growth was inhibited by exogenous human TGF-beta1 (hTGF-beta1) in a dose-dependent manner. In contrast, SW-13 cells and control clones transfected with empty vector remained hTGF-beta1-insensitive. Xenograft examination in athymic nude mice demonstrated that TbetaRII-positive SW-13 cells reduced tumor-forming activity. Reconstructing the TbetaRII can lead to reversion of the malignant phenotype of TbetaRII-negative human adrenocortical carcinoma, which contains SW-13 cells. Reduced TbetaRII expression may play a critical role in determining the malignant phenotype of human adrenocortical carcinoma.