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Biomedical subjects

D Danielpour

Publications and source records attributed to D Danielpour.

At least 19 recordsLinked to original sources
PubMed2006

ELAC2, a putative prostate cancer susceptibility gene product, potentiates TGF-beta/Smad-induced growth arrest of prostate cells.

Transforming growth factor-beta (TGF-beta) elicits a potent growth inhibitory effect on many normal cells by binding to specific serine/threonine kinase receptors and activating specific Smad proteins, which regulate the expression of cell cycle genes, including the p21 cyclin-dependent kinase (CDK) inhibitor gene. Interestingly, cancer cells are often insensitive to the anti-mitogenic effects of TGF-beta for which the molecular mechanisms are not well understood. In this study, we found that the candidate prostate cancer susceptibility gene ELAC2 potentiates TGF-beta/Smad-induced transcriptional responses. ELAC2 associates with activated Smad2; the C-terminal MH2 domain of Smad2 interacts with the N-terminal region of ELAC2. Small interfering siRNA-mediated knock-down of ELAC2 in prostate cells suppressed TGF-beta-induced growth arrest. Moreover, ELAC2 was shown to specifically associate with the nuclear Smad2 partner, FAST-1 and to potentiate the interaction of activated Smad2 with transcription factor Sp1. Furthermore, activation of the p21 CDK inhibitor promoter by TGF-beta is potentiated by ELAC2. Taken together our data indicate an important transcriptional scaffold function for ELAC2 in TGF-beta/Smad signaling mediated growth arrest.

Animals↗
PubMed2006

Cited2 modulates TGF-beta-mediated upregulation of MMP9.

Cited (CBP/p300-interacting transactivators with glutamic acid (E)/aspartic acid (D)-rich C-terminal domain) 2, which is a CBP/p300-binding transcription co-activator without typical DNA-binding domains, has been implicated in control of cell growth and malignant transformation in Rat1 cells. In this report, we provide evidence that Cited2 is an important regulator of transforming growth factor (TGF)-beta signaling. Overexpression of Cited2 enhanced TGF-beta-mediated transcription of a Smad-Binding Element-containing luciferase reporter construct, SBE4-Luc. This may occur through a direct physical association of Cited2 with Smads 2 and 3, as supported by co-immunoprecipitation, mammalian two-hybrid and glutathione S-transferase-pull down assays. The transcription factor p300, which binds to Smad3, was shown to further enhance the interaction between Cited2 and Smad3, and the transcriptional responses of Smad3 by Cited2 in reporter assays. Cited2 enhances TGF-beta-mediated upregulation of matrix metalloproteinase 9 (MMP9) in Cited2 inducible mouse embryo fibroblasts. Overexpression of Cited2 enhanced TGF-beta-mediated MMP9 promoter reporter activity. Moreover, knockdown of Cited2 in MDA-MB-231 cells attenuated TGF-beta-mediated upregulation of MMP9 and TGF-beta-mediated cell invasion. Chromatin immunoprecipitation showed that Cited2 and Smad3 were recruited to MMP9 promoter upon TGF-beta stimulation. This is the first demonstration that Cited2 functions as a Smad3/p300-interacting transcriptional co-activator in modulating the expression of MMP9, which could affect tumor cell invasion mediated by TGF-beta.

Animals↗
PubMed2001

Bcl-xL blocks transforming growth factor-beta 1-induced apoptosis by inhibiting cytochrome c release and not by directly antagonizing Apaf-1-dependent caspase activation in prostate epithelial cells.

The mechanism by which transforming growth factor-beta1 (TGF-beta1) induces apoptosis of prostate epithelial cells was studied in the NRP-154 rat prostate epithelial cell line. TGF-beta 1 down-regulates expression of Bcl-xL and poly(ADP-ribosyl)polymerase (PARP), promotes cytochrome c release, up-regulates expression of latent caspase-3, and activates caspases 3 and 9. We tested the role of Bcl-xL in this cascade by stably overexpressing Bcl-xL to prevent loss by TGF-beta 1. Clones overexpressing Bcl-xL are resistant to TGF-beta 1 with respect to induction of apoptosis, cytochrome c release, activation of caspases 9 and 3, and cleavage of PARP; yet they remain sensitive to TGF-beta 1 by cell cycle arrest, induction of both fibronectin and latent caspase-3 expression, and loss of PARP expression. We show that Bcl-xL associates with Apaf-1 in NRP-154 cells; but this association does not inhibit the activation of caspases 9 and 3 by cytochrome c. Together, our data suggest that TGF-beta1 induces apoptosis through loss of Bcl-xL, leading to cytochrome c release and the subsequent activation of caspases 9 and 3. Moreover, our data demonstrate that the antiapoptotic effect of Bcl-xL occurs by inhibition of mitochondrial cytochrome c release and not through antagonizing Apaf-1-dependent processing of caspases 9 and 3.

Apoptosis↗
PubMed2000

Ski acts as a co-repressor with Smad2 and Smad3 to regulate the response to type beta transforming growth factor.

The c-ski protooncogene encodes a transcription factor that binds DNA only in association with other proteins. To identify co-binding proteins, we performed a yeast two-hybrid screen. The results of the screen and subsequent co-immunoprecipitation studies identified Smad2 and Smad3, two transcriptional activators that mediate the type beta transforming growth factor (TGF-beta) response, as Ski-interacting proteins. In Ski-transformed cells, all of the Ski protein was found in Smad3-containing complexes that accumulated in the nucleus in the absence of added TGF-beta. DNA binding assays showed that Ski, Smad2, Smad3, and Smad4 form a complex with the Smad/Ski binding element GTCTAGAC (SBE). Ski repressed TGF-beta-induced expression of 3TP-Lux, the natural plasminogen activator inhibitor 1 promoter and of reporter genes driven by the SBE and the related CAGA element. In addition, Ski repressed a TGF-beta-inducible promoter containing AP-1 (TRE) elements activated by a combination of Smads, Fos, and/or Jun proteins. Ski also repressed synergistic activation of promoters by combinations of Smad proteins but failed to repress in the absence of Smad4. Thus, Ski acts in opposition to TGF-beta-induced transcriptional activation by functioning as a Smad-dependent co-repressor. The biological relevance of this transcriptional repression was established by showing that overexpression of Ski abolished TGF-beta-mediated growth inhibition in a prostate-derived epithelial cell line.

Cell Nucleus↗
PubMed2000

A novel mitochondrial septin-like protein, ARTS, mediates apoptosis dependent on its P-loop motif.

Here we describe a protein product of the human septin H5/PNUTL2/CDCrel2b gene, which we call ARTS (for apoptosis-related protein in the TGF-beta signalling pathway). ARTS is expressed in many cells and acts to enhance cell death induced by TGF-beta or, to a lesser extent, by other apoptotic agents. Unlike related septin gene products, ARTS is localized to mitochondria and translocates to the nucleus when apoptosis occurs. Mutation of the P-loop of ARTS abrogates its competence to activate caspase 3 and to induce apoptosis. Taken together, these observations expand the functional attributes of septins previously described as having roles in cytokinesis and cellular morphogenesis.

Amino Acid Motifs↗
PubMed2000

Selective loss of the transforming growth factor-beta apoptotic signaling pathway in mutant NRP-154 rat prostatic epithelial cells.

Retroviral insertional mutagenesis was used to select mutant NRP-154 rat prostate carcinoma cells resistant to transforming growth factor (TGF)-beta-induced cell death. Similar to the parental cells, a mutant clone, M-NRP1, expressed TGF-beta receptors and was still responsive to induction both of direct target genes by TGF-beta and of apoptosis by staurosporine or okadaic acid. In contrast, indicators of cell growth, strongly suppressed by TGF-beta in the parental cells, were unaffected in M-NRP1 cells. M-NRP1 cells overexpress the antiapoptotic protein, Bcl-xL, and show dysregulated expression and localization of a protein related to a novel human septin, ARTS (designation of apoptotic response to TGF-beta signals), cloned by homology to an exonic sequence flanked by the viral long terminal repeats in M-NRP1 cells and shown to make cells competent to undergo apoptosis in response to TGF-beta. We propose that ARTS might operate within the same apoptotic pathway as Bcl-xL and that M-NRP1 cells could serve as a useful model for characterization of this pathway.

Animals↗
PubMed1999

Loss of responsiveness to transforming growth factor beta induces malignant transformation of nontumorigenic rat prostate epithelial cells.

Transforming growth factor (TGF)-betas are multifunctional growth factors, the properties of which include the potent inhibition of epithelial cell growth. Expression patterns of TGF-betas and TGF-beta receptors in the normal prostate indicate that these growth regulators play key roles in prostatic development and proliferative homeostasis. Importantly, TGF-beta receptor levels are frequently diminished in malignant human prostate tissue. To test the hypothesis that loss of TGF-beta responsiveness is causally involved in the tumorigenic process, we have used retroviral transduction to introduce a dominant-negative mutant type II TGF-beta receptor (DNR) into the premalignant rat prostatic epithelial cell line, NRP-152. High-level expression of the DNR abolished the ability of TGF-beta to inhibit cell growth, to promote cell differentiation, and to induce apoptosis, and it partially blocked the induction of extracellular matrix gene expression. When injected into nude mice, NRP-152-DNR cells formed carcinomas at 13 of 34 sites, compared with 0 of 30 sites for parental and control cells (P = 0.0001). We conclude that the type II TGF-beta receptor is an important tumor suppressor in the prostate, and furthermore, that loss of TGF-beta responsiveness can contribute early in the tumorigenic process by causing the malignant transformation of preneoplastic cells.

Animals↗
PubMed1999

Retinoid and androgen regulation of cell growth, epidermal growth factor and retinoic acid receptors in normal and carcinoma rat prostate cells.

Recent in vivo and in vitro studies suggest that retinoic acid receptor (RAR)-mediated processes may be involved in androgen regulation of prostate cells in a manner that may be altered during prostatic carcinogenesis. We tested this hypothesis in the newly established carcinoma and non-carcinoma rat prostate epithelial cell lines, NRP-154 and NRP-152, respectively. In DMEM/F-12 medium supplemented with 10% charcoal stripped fetal calf serum (cFCS), the number of both NRP-152 and NRP-154 cells were stimulated by testosterone (T), with a 4-fold greater effect in NRP-152 than in NRP-154 cells. Retinoic acid (RA) alone also stimulated the growth of NRP-152 cells, but failed to induce cell growth of NRP-154 cells. Importantly, the level of RAR alpha mRNA was elevated whereas the levels of RAR gamma and androgen receptor (AR) mRNA were lower in NRP-154 cells compared to those in NRP-152 cells. Treatment of NRP-152 cells with increasing doses of T resulted in a dose-dependent decrease and rebound of the level of RAR alpha and gamma mRNA in NRP-152 cells; these effects were not apparent, if not reversed, in NRP-154 cells. Both ligand binding and Western blot analyses revealed that epidermal growth factor receptor (EGF-R) was stimulated by 20 nM T but was suppressed by 0.1 microM RA, which also attenuated the stimulating effects of T on EGF-R in NRP-152 and to a lesser extent in NRP-154 cells. The differences in the level and androgen regulation of RAR mRNAs and reciprocal regulation of EGF-R expression by T and RA between NRP-154 and NRP-152 cells suggest that variations in the EGF-R and RAR signal events may contribute to differences in growth rate between these two cell lines.

Animals↗
PubMed1999

The rat prostatic epithelial cell line NRP-152 can differentiate in vivo in response to its stromal environment.

BACKGROUND: The clonally derived rat prostatic epithelial cell line NRP-152 was examined to determine its ability to differentiate in a tissue recombination model. METHODS: NRP-152 cells alone, or combined with urogenital mesenchyme (UGM) or 10T1/2 fibroblasts, were grafted beneath the renal capsule of athymic rodent hosts. After 1 and 3 months, grafts were examined grossly and immunohistochemically. RESULTS: NRP-152 cells grafted alone formed small (10-25 mg) grafts without recognizable architecture. NRP-152 cells recombined with UGM formed larger grafts (50-100 mg after 28 days) containing glandular epithelium. Columnar luminal cells expressed cytokeratins 8 and 18 and rat prostatic secretory markers (DP-1 and DP-2). The epithelial ducts were surrounded by well-differentiated smooth muscle. The glandular epithelial cells were shown to be of rat origin. NRP-152 + 10T1/2 tissue recombinants formed small grafts (10-40 mg wet weight) after 1 month. The epithelial component of these grafts formed solid unbranched cords expressing cytokeratins 5 and 14; no glandular epithelial structures were observed. The stromal matrix was densely packed with a few cells expressing alpha-actin. CONCLUSIONS: A clonally derived prostatic epithelial cell line can form structurally and functionally normal prostatic tissue. This suggests that prostatic basal and luminal epithelial cells can be derived from a common progenitor.

Animals↗
PubMed1999

Transdifferentiation of NRP-152 rat prostatic basal epithelial cells toward a luminal phenotype: regulation by glucocorticoid, insulin-like growth factor-I and transforming growth factor-beta.

The role of basal epithelial cells in prostatic function, development and carcinogenesis is unknown. The ability of basal prostatic epithelial cells to acquire a luminal phenotype was explored in vitro using the NRP-152 rat dorsal-lateral prostate epithelial cell line as a model system. NRP-152, which was spontaneously immortalized and clonally derived, is an androgen-responsive and nontumorigenic cell line that has a basal cell phenotype under normal growth conditions. However, when placed in mitogen-deficient media, these cells undergo a dramatic morphological change to a luminal phenotype. Under these growth-restrictive conditions, immunocytochemical analysis shows that NRP-152 cells acquire the luminal markers Z0-1 (a tight-junction associated protein), occludin (integral tight-junction protein), and cytokeratin 18, and lose the basal markers cytokeratins 5 and 14. Total protein and mRNA levels of cytokeratins 8, 18, c-CAM 105 (the calcium-independent cell adhesion molecule) and Z0-1, as detected by western and/or northern blot analyses, respectively, are induced, while cytokeratin 5 and 15 are lost, and occludin is unchanged. Concomitant with this differentiation, expression of transforming growth factor-beta2 (TGF-beta2), TGF-beta3, and TGF-beta receptor type II (TbetaRII) is induced, while those of TGF-beta1 and TbetaRI remain essentially unchanged. Mitogens, such as insulin-like growth factor-I and dexamethasone inhibit luminal differentiation, while exogenous TGF-beta induces such differentiation. These data together with TGF-beta neutralization experiments using pan-specific antibody implicate an important role for autocrine TGF-beta in the induction of the luminal differentiation.

Animals↗
PubMed1998

The role of transforming growth factor-beta1, -beta2, and -beta3 in androgen-responsive growth of NRP-152 rat prostatic epithelial cells.

We have investigated the role of autocrine/paracrine TGF-beta secretion in the regulation of cell growth by androgens as demonstrated by its inhibition by two androgen response modifiers; the nonsteroidal antiandrogen hydroxyflutamide (OHF), believed to act by inhibiting androgen binding to androgen receptors, or finasteride, an inhibitor of 5alpha-reductase, the enzyme necessary for the conversion of testosterone to 5alpha-dihydrotestosterone (DHT), using the nontumorigenic rat prostatic epithelial cell line NRP-152. Growth of these cells was stimulated three- to sixfold over control by either testosterone or DHT under serum-free culture conditions. This was accompanied by a two- to threefold decrease in the secretion rate of TGF-beta1, -beta2, and -beta3. Finasteride reversed the ability of testosterone but not DHT to stimulate growth and downregulate expression of TGF-beta1, -beta2, and -beta3 in a dose-dependent fashion, suggesting that this activity of testosterone required its conversion to DHT. OHF antagonized the stimulatory effects of DHT on NRP-152 cell growth but could reverse the inhibitory effects of DHT only on TGF-beta2 and TGF-beta3 and not TGF-beta1 secretion. This suggests that either TGF-beta1 regulation by DHT or the androgen antagonism of OHF occurs independent of androgen receptor binding. Neutralizing antibodies to TGF-beta (pantropic and isoform-specific) were able to block the ability of finasteride to antagonize the effects of testosterone nearly completely while only partially inhibiting the antiandrogenic effects of OHF. Thus, the ability of androgens to stimulate growth of NRP-152 cells involves the downregulation of the production of TGF-beta1, -beta2, and -beta3 in addition to other growth-stimulatory mechanisms.

Androgen Antagonists↗
PubMed1997

Qualitative and quantitative analysis of DNA fragmentation using digital imaging.

Apoptosis is an important and common pathway of cellular death. Differentiation from cellular necrosis and quantitation of apoptosis within the milieu of necrosis are analytical challenges. We describe the use of the RIT120 digital imaging software package for quantitative and qualitative analysis of apoptotic DNA ladders induced by a variety of agents, such as serum, tumor necrosis factor-alpha, transforming growth factor-beta1, and nitric oxide. Autoradiographs of DNA ladders are densitometrically scanned to yield a set of curves with peaks corresponding to specific DNA fragments, thereby allowing quantitative subtraction of concurrent DNA degradation from necrotic death. Integration of the areas specifically under the peaks yields a quantitative measure of apoptosis. We provide a useful, rapid, and objective means to quantitate apoptosis, using relatively inexpensive hardware and software.

Animals↗
PubMed1996

Regulation of apoptosis induced by transforming growth factor-beta1 in nontumorigenic rat prostatic epithelial cell lines.

Transforming growth factor-beta1 (TGF-beta1), which is induced in the prostate following castration, has been speculated to mediate apoptosis of epithelial cells during prostatic involution. Here, we report the first evidence of a direct effect of TGF-beta on induction of apoptosis in prostatic epithelial cells in vitro, using NRP-152 nontumorigenic and NRP-154 tumorigenic rat prostatic epithelial cell lines. TGF-beta1 induces apoptosis of both cell lines within 24 h, as shown by a decrease in cell viability, in situ DNA nick-end labeling, and internucleosomal DNA fragmentation. Moreover, the ability of TGF-beta to induce apoptosis of NRP-152 is strictly dependent on culture conditions, because dexamethasone enhances while insulin and insulin-like growth factor-I specifically block apoptosis induced by TGF-beta. We suggest that TGF-betas are direct physiological regulators of apoptosis of prostatic epithelial cells.

Animals↗
PubMed1996

Induction of transforming growth factor-beta autocrine activity by all-trans-retinoic acid and 1 alpha,25-dihydroxyvitamin D3 in NRP-152 rat prostatic epithelial cells.

Retinoids and vitamin D analogues are known to inhibit the proliferation of a variety of cells in culture and prevent the formation of certain tumors in mammals. Although it is well established that these hormones control the transcription of many genes upon binding to and activating specific nuclear receptors, the mechanisms by which they prevent cancer are as yet poorly understood. In this study the role of the transforming growth factor-beta (TGF-beta) growth inhibitors, in promoting the biological activities of all-trans-retinoic acid (RA) and 1 alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3) was studied in NRP-152 cells, a nontumorigenic epithelial line derived from rat dorsal-lateral prostate. Inhibition of growth by nanomolar concentrations of RA was associated with an increase in both mRNA and protein for all three TGF-beta isoforms, with greater and much earlier increases for TGF-beta s 2 and 3 (5.5 h) than for TGF-beta 1 (24 h). A monoclonal antibody against TGF-beta and TGF-beta 1 latency associated peptide (LAP), both of which neutralize all three TGF-beta isoforms, each block the ability of RA to inhibit growth of NRP-152 cells by > 95%. Neutralization of growth inhibition by isoform-specific antibodies suggested that all three TGF-beta s are involved in this effect. The ability of RA to upregulate fibronectin and thrombospondin expression in NRP-152 cells was also blocked by the monoclonal antibody. 1,25-(OH)2D3, which also induced TGF-beta s 2 and 3 but not TGF-beta 1, and their respective mRNAs, also induced fibronectin and thrombospondin through induction of TGF-beta. Thus, autocrine production of TGF-beta s may be a significant part of the mechanisms by which RA and 1,25-(OH)2D3 promote cellular differentiation.

Animals↗
PubMed1996

Radiation-induced lung injury in vivo: expression of transforming growth factor-beta precedes fibrosis.

Cytokine release from irradiated cells has been postulated to start soon after irradiation preceding detectable clinical and pathological manifestation of lung injury. The expression of transforming growth factor beta (TGF beta), a fibrogenic and radiation-inducible cytokine, was studied from 1-16 weeks after the 15 and 30 Gray (Gy) of thoracic irradiation to rats. Thoracic irradiation caused an increase in TGF beta protein in bronchoalveolar lavage (BAL) fluid peaking at 3-6 weeks as compared to sham-irradiated control rats. Steady state TGF beta mRNA expression as shown by whole lung northern blot assay paralleled the TGF beta protein expression in BAL fluid. The peak of TGF beta protein increase in BAL fluid between 3 and 6 weeks coincided with the initial influx of inflammatory cells in BAL fluid, but preceded histologically discernable pulmonary fibrosis that was not apparent until 8-10 weeks after irradiation. In conclusion. TGF beta and mRNA and protein upregulation preceded the radiation-induced pulmonary fibrosis, suggesting a pathogenetic role in the development of radiation fibrosis.

Animals↗
PubMed1995

Regulation of transforming growth factor-beta 1 and its receptor by cyclosporine in human T lymphocytes.

Scarring, fibrosis, and immunosuppression occurs with chronic cyclosporine (CsA) administration. We postulated that CsA may induce transforming growth factor (TGF)-beta 1 secretion from human T lymphocytes, a cytokine with immunoregulatory effects that has been implicated in the pathogenesis of wound healing and scarring. TGF-beta 1 was measured in serum-free supernatants harvested from T lymphocytes stimulated in the presence of CsA by a specific sandwich ELISA. CsA (10-1000 ng/ml) enhanced TGF-beta 1 secretion by approximately 40-80% in a dose-dependent manner. Increased TGF-beta 1 secretion in the presence of CsA was accompanied by a 2- to 4-fold increase in TGF-beta 1 mRNA levels due to both enhancement of its nuclear transcription as well as prolongation of TGF-beta 1 mRNA half-life. To determine whether the increase in TGF-beta 1 secretion was also accompanied by a concomitant change in its receptor, TGF-beta 1 receptor expression was analyzed by cross-linking of radioiodinated TGF-beta 1. Unactivated T lymphocytes expressed both a 105-kDa and a 65-kDa TGF-beta receptor. Upon stimulation, a transient increase in receptor density was seen at 12 hr, followed by a decline at later time points. Cells treated with CsA exhibited at least 2-fold higher levels of TGF-beta receptors in a dose-dependent manner. Thus, CsA enhances the production of TGF-beta 1 protein as well as the expression of its receptor in activated T lymphocytes. Enhanced TGF-beta 1 production and binding may contribute to the immunosuppressive and fibrosis-promoting effects of CsA therapy.

Adult↗