Autocrine growth mechanism by transforming growth factor (TGF)-beta 1 and TGF-beta 1-receptor regulation by epidermal growth factor in a human endometrial cancer cell line IK-90

Mesangial cell hypertrophy by high glucose is mediated by downregulation of the tumor suppressor PTEN

Diabetic nephropathy is characterized early in its course by glomerular hypertrophy and, importantly, mesangial hypertrophy, which correlate with eventual glomerulosclerosis. The mechanism of hypertrophy, however, is not known. Gene disruption of the tumor suppressor PTEN, a negative regulator of the phosphatidylinositol 3-kinase/Akt pathway, in fruit flies and mice demonstrated its role in size control in a cell-specific manner. Here, we investigated the mechanism of mesangial hypertrophy in response to high extracellular glucose. We link early renal hypertrophy with significant reduction in PTEN expression in the streptozotocin-induced diabetic kidney cortex and glomeruli, concomitant with activation of Akt. Similarly, exposure of mesangial cells to high concentrations of glucose also decreased PTEN expression and its phosphatase activity, resulting in increased Akt activity. Expression of PTEN inhibited high-glucose-induced mesangial cell hypertrophy, and expression of dominant-negative PTEN was sufficient to induce hypertrophy. In diabetic nephropathy, the hypertrophic effect of hyperglycemia is thought to be mediated by transforming growth factor-beta (TGF-beta). TGF-beta significantly reduced PTEN expression in mesangial cells, with a reduction in its phosphatase activity and an increase in Akt activation. PTEN and dominant-negative Akt attenuated TGF-beta-induced hypertrophy of mesangial cells. Finally, we show that inhibition of TGF-beta signal transduction blocks the effect of high glucose on PTEN downregulation. These data identify a novel mechanism placing PTEN as a key regulator of diabetic mesangial hypertrophy involving TGF-beta signaling.

Expression of TGF-beta type II receptors in the olfactory epithelium and their regulation in TGF-alpha transgenic mice

Numerous in vitro studies of neurogenesis of olfactory receptor neurons (ORNs) suggest that transforming growth factor (TGF)-beta promotes the maturation/differentiation of olfactory progenitors. We demonstrate that in vivo both mature and immature ORNs, and possibly a basal neuronal progenitor cell, express the TGF-beta type II receptor (TGF-betaRII), suggesting that these cells are targets for TGF-beta signaling. In a previous study of neurogenesis in the OE of TGF-alpha overexpressing transgenic (T) mice, we observed an apparent reduction in the expression of olfactory marker protein (OMP), a marker of terminal differentiation in ORNs in T mice compared to nontransgenic (NT) littermate controls; this was confirmed by Western blotting and immunohistochemistry. In contrast, there was no apparent difference between T and NT mice in the intensity of immunoreactivity for a neuronal marker, protein gene product 9.5. Because TGF-alpha overexpression has been reported to affect TGF-beta signaling in other epithelia, we compared the expression of the TGF-beta type II receptor (TGF-betaRII) in T and NT mice. The intensity of TGF-betaRII immunoreactivity on ORNs was substantially reduced in T compared to NT mice. Similar reductions in TGF-betaRII expression in vomeronasal receptor neurons and in other epithelia in the nasal cavity of T mice were also observed. Taken together, these results indicate that TGF-beta signaling regulates terminal differentiation of ORNs in vivo and suggest ways in which interactions between TGF-alpha and TGF-beta signaling pathways may interact in the OE.

Production of activin A in hyperplasia and adenocarcinoma of the human endometrium

OBJECTIVES

To examine the possible localization and production of activin A in human normal endometrium, endometrial hyperplasia, and adenocarcinoma tissues.

METHODS

Human endometrial tissues were collected from 45 patients who were undergoing abdominal hysterectomy. Tissue sections were stained with monoclonal antibodies against the inhibin/activin alpha- and beta A-subunits and activin A using an avidin-biotin-peroxidase complex technique. Concentrations of activin A and inhibin A in tissue extracts of the endometrial tissues were measured using enzyme-linked immunosorbent assays (ELISAs). The expressions of the inhibin alpha-subunit and activin beta A-subunit messenger RNA (mRNA) in the endometrial tissues were demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) analysis.

RESULTS

No immunostaining with an antibody against the inhibin alpha-subunit was observed in human normal endometrium, endometrial hyperplasia, and adenocarcinoma. By contrast, immunostaining for the activin beta A-subunit and activin A was observed in the cytoplasm of glandular cells in normal endometrium, endometrial hyperplasia, and tumor cells of endometrial adenocarcinoma. The percentages of stained cells in endometrial adenocarcinoma were higher than those in normal endometrium. Also, the percentages of stained tumor cells with poor differentiation were higher than those with good and moderate differentiation of the endometrium. The stromal cells in normal endometrium, endometrial hyperplasia, and adenocarcinoma were weakly immunoreactive with antibodies against the beta A-subunit and activin A. Immunoreactivity of activin A in tissue extracts from normal endometrium and endometrial adenocarcinoma was detected by the two-site ELISA. Immunoreactivity of activin A was significantly higher in adenocarcinoma than in normal endometrium. On the other hand, the immunoreactive inhibin A was not detected. The expression of the alpha-subunit mRNA in endometrial tissues was demonstrated as the RT-PCR products migrated at 905 bp and the PCR products of the beta A-subunit showed a band at 366 bp.

CONCLUSIONS

It is suggested that activin A, but not inhibins, are produced by endometrial tissues. The amounts of produced activin A were higher in adenocarcinoma tissues than in normal endometrium. Activin A might be involved in human endometrial tumorigenesis.

The association of transforming growth factor-beta 1 with myometrial invasion of endometrial carcinomas through effects on matrix metalloproteinase

OBJECTIVE

The association of transforming growth factor-beta 1 (TGF-beta 1) with a matrix metalloproteinase (MMP) and a tissue inhibitor of metalloproteinase (TIMP), as well as myometrial invasion of endometrial cancer was studied.

METHODS

The effects of TGF-beta 1 on cellular invasiveness, gelatinase activity, and expression of TIMP-1 were examined in 2 endometrial adenocarcinoma cell lines, KLE and Ishikawa. Plasma was obtained from 8 endometrial cancer patients with Stage-Ia disease, from 6 with Stage-Ib disease, and from 4 with Stage-Ic disease, and the levels of TGF-beta 1 were measured by enzyme immunoassays. The immunohistochemical expression of MMP-9, TIMP-1, TGF-beta 1, and TGF-beta receptor Type I in tumor tissue from the same patients also was detected.

RESULTS

Invasiveness, gelatinase activity, and the expression of TIMP-1 were higher in KLE cells than in Ishikawa cells, and they were increased by treatment with rTGF-beta 1. The expression of TGF-beta receptor Type I was higher in KLE cells than in Ishikawa cells, which were unresponsive to exogenous TGF-beta 1. The plasma levels of TGF-beta 1 were greater in Stage-Ib and Stage-Ic patients than in Stage-Ia patients. MMP-9 and TGF-beta receptor Type I were expressed mainly in tumor cells, while TIMP-1 and TGF-beta 1 were localized in both tumor epithelial cells and stromal cells. MMP-9 and TIMP-1 were expressed only in Stage-Ib and Stage-Ic patients, although TGF-beta 1 and TGF-beta receptor Type I were ubiquitous.

CONCLUSIONS

Myometrial invasion of endometrial cancers involves an increase in gelatinase activity, regulated to some extent by TGF-beta 1 in an autocrine or paracrine fashion.

Stimulation of TGF-beta type II receptor by high glucose in mouse mesangial cells and in diabetic kidney

Transforming growth factor-beta (TGF-beta) is important in the pathogenesis of diabetic nephropathy, but little is known about the regulation of the ligand-binding TGF-beta type II signaling receptor (TbetaIIR). There were significant increases in TbetaIIR protein and mRNA levels in kidney cortex after 1-6 wk of streptozotocin-induced diabetes. Mouse mesangial cells cultured in high glucose demonstrated significantly increased TbetaIIR protein and mRNA levels compared with normal glucose. This effect was independent of stimulation of TGF-beta bioactivity by high glucose. Consistent with transcriptional activation by high glucose, the half-life ( approximately 4 h) of TbetaIIR mRNA was not affected by glucose concentration. Moreover, mouse mesangial cells transiently transfected with reporter constructs containing the first 47- or 274-bp promoter fragments of TbetaIIR demonstrated significantly increased reporter activity in high glucose. Cells grown in high glucose demonstrated increased responsiveness to a relatively small dose of exogenous TGF-beta(1) (0.5 ng/ml): [(3)H]proline incorporation and alpha(1)(IV) collagen mRNA were significantly greater in cells cultured in high than in normal glucose. Hence, the expression of TbetaIIR is increased in the diabetic kidney and in mesangial cells cultured in high glucose, primarily because of stimulation of gene transcription. TbetaIIR upregulation by high ambient glucose may contribute to the increased sensitivity of mesangial cells to the profibrogenic action of TGF-beta(1).

Messenger RNA differential display reverse-transcriptase-polymerase-chain-reaction analysis of a progestogen-suppressive gene in a human endometrial-cancer cell line

Progestogen suppresses the progression of endometrial cancer and has an important effect on the secretory change of human endometrium. We characterized the progestogen-induced alterations of gene expression in a human endometrial-cancer cell line using a mRNA differential-display reverse-transcriptase-polymerase-chain-reaction (DDRT-PCR) method. After 5-day incubation of Ishikawa endometrial-cancer cells, with or without 100 nM medroxyprogesterone acetate (M PA), total RNA was isolated from confluent cells. We identified 8 candidate genes by mRNA differential display by screening up to approximately 3,000 mRNA species. Among these, 2 genes named T21A and T21B showed a decrease in mRNA by MPA treatment when analyzed by Northern blot. Nucleotide sequence showed that clone T21A was part of human mitochondrial short-chain enoyl-CoA hydratase cDNA. The other clone, T21B, showed no homology with any known nucleotide sequences. Northern-blot analysis using T21A and T21B clones as probes showed a decrease in mRNA in human endometrium from the luteal stage, with high serum estradiol and progesterone levels, as compared with that from the early follicular stage, with low serum estradiol and progesterone levels, and that from the pre-ovulatory stage with high serum estradiol and low progesterone levels. These findings suggest that mRNA DDRT-PCR could be used to identify the candidate genes regulated by progestogen in human endometrial cancer and in normal human endometrium.

Inhibitory effects of tranilast on expression of transforming growth factor-beta isoforms and receptors in injured arteries

Tranilast (N(3,4-dimethoxycinnamoyl)anthranilic acid), an agent which in cell culture inhibits transforming growth factor-beta (TGF-beta) secretion and antagonises the effects of TGF-beta and platelet-derived growth factor (PDGF) on cell migration and proliferation, has been reported to reduce the incidence of restenosis after angioplasty in angiographically validated human clinical trials. We investigated in a rat model of balloon angioplasty whether tranilast's effects in vivo could be attributed to inhibition of expression of TGF-beta and/or its receptor types. Using a standardised reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we examined the effects of three doses of tranilast (25, 50 and 100 mg/kg) on the expression of two TGF-beta isoforms, the types I and II TGF-beta receptors and two putative TGF-beta responses, induction of integrins alpha(v) and beta3 mRNA, 2 h after oral administration and 26 h after vessel injury. Tranilast attenuated in a dose-dependent and reversible manner the injury-induced increases in mRNA levels encoding TGF-beta1, TGF-beta3, two type I TGF-beta receptors ALK-5 and ALK-2, and the type II receptor TbetaRII. At the highest dose mRNA levels encoding TGF-beta1 and TbetaRII were attenuated to levels approaching or below those observed in uninjured vessels. Messenger RNAs encoding TGF-beta3, ALK-5 and ALK-2 were all attenuated by between 70 and 74% (all P < 0.05). Tranilast also attenuated in a reversible manner the elevations in mRNA levels for integrins alpha(v) and beta3 observed after vessel injury, by 90 and 72%, respectively. We also investigated, in cultured smooth muscle cells derived from injured carotid arteries, the extent to which tranilast (300 mg/l) attenuated any increases in expression of type I and type II receptors stimulated by PDGF-BB and TGF-beta1, growth factors implicated in smooth muscle cell migration and proliferation in injured vessels. Increases in mRNA levels of the type I receptors ALK-5 and ALK-2 induced by PDGF-BB and TGF-beta1 were almost completely prevented by tranilast. Tranilast also prevented the PDGF-BB induced increases in TbetaRII but only partially inhibited the TGF-beta1 induced upregulation of TbetaRII. We conclude that tranilast can inhibit transcriptional mechanisms associated with the upregulation of TGF-beta and its receptor types in balloon catheter injured vessels. It is possible that these mechanisms contribute to its ability to reduce the frequency of restenosis after angioplasty.

Discordant regulation of transforming growth factor-beta receptors by prostaglandin E2

The effect of PGE2 on TGF-beta receptor binding was assessed for both signaling (type I and type II) and non-signaling (type III) TGF-beta receptors. We found in cross-linking studies that PGE2 treatment (24 h) decreased binding of TGF-beta to the type I and type II receptors by approx. 50% and markedly increased binding of TGF-beta to type III receptors nearly 10-fold. Northern analyses indicated that PGE2 decreased type I receptor mRNA levels by approximately 30-50%, decreased type II receptor mRNA levels by approximately 60%, and markedly increased type III receptor mRNA levels. Coincubation with cycloheximide partially blocked the PGE2-induced inhibition of type II receptor mRNA. In contrast, cycloheximide minimally affected PGE2-induced type III receptor mRNA levels. Activation of protein kinase C by phorbol esters had no apparent effect on TGF-beta receptor mRNA levels. Our data suggest that alterations in TGF-beta receptor expression could modify the response of tissues to TGF-beta during injury.