| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
ARTICLE |
The Urologic Laboratory, Department of Urology, Children’s Hospital Boston and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115
Address all correspondence and requests for reprints to: Michael R. Freeman, Ph.D., John F. Enders Research Laboratories, Room 1161, Children’s Hospital Boston, 300 Longwood Avenue, Boston, Massachusetts 02115. E-mail: michael.freeman{at}TCH.harvard.edu.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Alternatively, the AR may be activated by stimuli other than exogenous steroid ligands [reviewed by Feldman and Feldman (7)]. Culig et al. (8) demonstrated that expression of prostate-specific antigen could be stimulated in a low androgen environment following treatment of PCa cells with specific peptide growth factors. In that study, growth factor-stimulated prostate-specific antigen expression was ablated in the presence of the antiandrogen, Casodex (bicalutamide), confirming involvement of the AR. This was the first demonstration of the potential for androgen-independent, AR-dependent regulation of AR-regulated genes. Subsequently, AR-dependent gene expression in PCa cells has been observed following activation of various signaling pathways, such as protein kinase A (9, 10), MAPK (11) (12), and phosphatidylinositiol-3 kinase/Akt (13, 14). In these situations, the AR remains functional under androgen-depleted conditions.
A third possibility is that the AR becomes dispensable for survival and proliferation of PCa cells. Under these circumstances, cell survival might be mediated by pathways other than the androgen-AR axis, such as those activated by growth factors and cytokines or by increased activity of antiapoptotic molecules, e.g. Bcl-2. Peptide growth factors are often proposed as potential mediators of PCa progression to an androgen-independent state (15, 16, 17, 18, 19, 20); however, a causal link between the action of a single growth factor and acquisition of either androgen independence or AR independence has yet to be established.
Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is an ErbB1/EGF receptor ligand and PCa cell mitogen that is expressed primarily by interstitial and vascular smooth muscle cells (SMC) of the human prostatic stroma (21). HB-EGF and the related peptide growth factor, amphiregulin, also a product of stromal SMC (22), may function as diffusible mediators of stromal-epithelial interactions through activation of the EGF receptor expressed by basal epithelial cells of the prostatic ducts and by adenocarcinoma cells. Recent data from our laboratory (23) demonstrate that HB-EGF, acting through the Erk-MAPK pathway, can also promote neuroendocrine (NE) differentiation in the PCa cell line, LNCaP, including induction of a neuron-like morphology and expression of the NE marker, neuron-specific enolase (NSE).
In this study, we assessed the extent to which androgen-responsive LNCaP cells become independent of the androgen-AR axis in vitro and in vivo in response to continuous exposure to HB-EGF.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Generation of LNCaP transfectants
To generate the constitutively secreted HB-EGF isoform, a fragment encoding the mature soluble form of HB-EGF was amplified by PCR from a previously engineered HB-EGF construct (24) using the primers: 5'-GGATCCATGAAGCTGCTGCCGTCGGTGGTG-3' and 5'-AAGTCTGGGCCCTTCCACTGGGAGGCTCAG-3', which incorporated recognition sites for BamHI and ApaI, respectively. The PCR product encodes soluble HB-EGF, in which the C-terminal amino acid is Glu151 as described previously (25). The PCR product was ligated into pcDNA3.1MycHis (Invitrogen Corp., Carlsbad, CA), and subcloned into pIRES2Hyg (CLONTECH Laboratories, Inc., Palo Alto, CA) to create pIRES/sHB-EGF. LNCaP cells were transfected with pIRES/sHB-EGF using FuGENE 6 transfection reagent (Roche Molecular Biochemicals, Indianapolis, IN) according to the manufacturer’s protocol and a stable population (hereafter LNCaP/sHB) was isolated following selection in 200 µg/ml hygromycin. Cells transfected with empty vector (LNCaP/VO) served as control. The expression of soluble HB-EGF was confirmed by immunoblot analysis of heparin-binding proteins in conditioned medium from control LNCaP/VO or LNCaP/sHB populations. Soluble HB-EGF was detected using goat polyclonal antibody to the HB-EGF ectodomain (R&D Systems, Minneapolis, MN). Protein was visualized using SuperSignal enhanced chemiluminescent reagent (Pierce Chemical Co., Rockford, IL).
Growth of LNCaP transfectants in vitro
LNCaP/sHB and LNCaP/VO cells were seeded in six-well plates at 5 x 104 cells/well in RPMI/10% FBS and incubated for 2 wk at 37 C. At the end of the assay, 0.2 ml/well methylthiazoletetrazolium (MTT) (5 mg/ml) was added, and cells were incubated for a further 4 h. Cells were triturated, pelleted by low-speed centrifugation, and the cell pellet solubilized with isopropanol/0.1 N HCl to elute incorporated dye. Absorbance was measured at 570 nm with background correction at 655 nm.
To determine the effects of androgen depletion on growth of LNCaP transfectants, cells were plated at 2 x 105 cells/well in 24-well plates in RPMI/10% FBS. Twenty-four hours after plating, cells were switched into RPMI supplemented with 10% charcoal/dextran-stripped serum (CSS) and incubated for a further 5 d. In selected experiments, the effect of Casodex (bicalutamide) on proliferation was determined. Twenty-four hours after cells were plated, vehicle [dimethylsulfoxide (DMSO)] or Casodex at 1 or 10 µM in RPMI/10% CSS was added every day for 5 d. Cells were processed as described above.
Survival, growth, and NE differentiation of LNCaP transfectants in vivo
LNCaP/VO and LNCaP/sHB cells were assayed for tumor-forming ability and growth in intact or castrated severe combined immunodeficient (SCID) mice in vivo. Castration, by a lower abdominal approach, was performed 1 wk before implantation of 2 x 106 cells in 150 µl Matrigel (Collaborative Bioscience, Becton Dickinson and Co., Bedford, MA) under the skin. Tumor growth was monitored weekly and palpable tumors were measured with calipers according to the formula length x width x height x 0.5236 (26). At the indicated time points, tumors were harvested and divided into two fragments; one fragment was fixed in 10% buffered formalin and embedded in paraffin for histological analysis, and the other fragment was snap frozen in liquid nitrogen and stored at –80 C. All animal experiments were performed in accordance with accepted standards of humane animal care and with the approval of the Institutional Animal Care and Use Committee, Children’s Hospital Boston.
Immunoblot analysis of tumor tissue
Snap-frozen tumor tissue was resuspended in 50 mM Tris-HCl (pH 7.4), 150 mM NaCl, 1 mM EDTA, 1% Triton X-100, and protease inhibitors at a ratio of 3 ml/g tissue, and dispersed mechanically using a Dounce homogenizer (VWR Scientific, West Chester, PA). Samples were incubated on ice for 30 min and insoluble material pelleted by centrifugation at 15,000 x g, 4 C for 10 min. The protein content of tissue extracts was determined using the Bio-Rad DC (detergent-compatible) protein assay (Bio-Rad Laboratories, Inc., Hercules, CA). Equal amounts of protein were fractionated by SDS-PAGE and electroblotted to polyvinylidenedifluoride membrane. Following transfer, membranes were stained with Ponceau S (Sigma, St. Louis, MO) to confirm equal protein loading, blocked with PBS-Tween/10% dried milk and incubated with antibodies to NSE (Ab-3, clone E27), chromogranin A (Ab-1, clone LK2H10 (both from Labvision Corp., Fremont, CA), or the AR (clone G122–434, BD Biosciences, San Diego, CA). Membranes were incubated with SuperSignal reagent (Pierce Chemical Co., Rockford, IL), and proteins were visualized by enhanced chemi-luminescence.
Assessment of neuroendocrine differentiation in PC-3
PC-3 PCa cells were seeded at 1 x 105 cells/well in six-well dishes and left to plate overnight. Cells were switched to RPMI/5% CSS for 12–16 h and then treated with recombinant HB-EGF (R&D Systems, Minneapolis, MN) in RPMI/5% CSS for up to 5 d, with growth factor replenished each day. At 0, 3, and 5 d total cell lysates were prepared in 62.5 mM Tris-Cl (pH 6.8), 2% sodium dodecyl sulfate, 10% glycerol. Equal amounts of protein were fractionated by SDS-PAGE, electroblotted to polyvinylidenedifluoride, and probed with anti-NSE antibody as described above.
Functional analysis of the androgen receptor in vitro
LNCaP/sHB and LNCaP/VO cells were seeded at a density of 5 x 106 cells/10-cm dish in RPMI/10% CSS and incubated for 36 h. Medium was changed to OptiMEM medium (Invitrogen Corp.), and cells were cotransfected with 30 µg mouse mammary tumor virus-long terminal repeat (MMTV-LTR) luciferase plasmid and 3 µg ß-Gal plasmid per dish using Lipofectamine 2000 (Invitrogen Corp.) according to the manufacturer’s protocol. After 6 h, cells were switched to RPMI/10% CSS for a further 18 h and then seeded in poly-L-lysine-coated six-well plates in RPMI/5% CSS and allowed to plate overnight. Cells were treated with medium alone, 1 µM Casodex, 10 nM dihydrotestosterone (DHT), or 10 nM DHT/1 µM Casodex all prepared in RPMI/5% CSS for 3 d, with reagents replenished daily. At the end of the treatment period, medium was removed and cells were lysed with 100 µl/well reporter lysis buffer (Promega Corp., Madison, WI). Lysates were subjected to three freeze-thaw cycles and insoluble material pelleted with high-speed centrifugation. Lysates were assayed for luciferase and ß-galactosidase activity according to standard protocols and normalized to protein content as determined using the Micro BCA protein assay (Pierce Chemical Co., Rockford, IL).
Statistical and image analysis
Where appropriate, experimental groups were compared using Student’s two-tailed t test, with significance defined as P < 0.05. For quantitation of immunoblot data, images were analyzed using Scion Image software, version 1.62 (Scion Corp., Frederick, MD).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
PCa) ErbB1-activating signal on PCa cell behavior, we engineered the LNCaP cell line to constitutively secrete a soluble form of HB-EGF (LNCaP/sHB). This model system allows LNCaP cells to be studied under conditions of constant exposure to the stromal growth factor, a situation that permits in vivo experiments and which cannot be completely mimicked in vitro by addition of the soluble growth factor into the medium. The construct encoding processed HB-EGF was subcloned into a bicistronic expression vector, pIRESHyg2, in which expression of HB-EGF is obligatorily coupled to expression of the hygromycin resistance gene. This expression strategy results in the creation of a stably modified cell population, while avoiding potential artifacts associated with isolation of single-cell clones. LNCaP/sHB cells were confirmed to secrete HB-EGF into the extracellular space by immunoblot analysis of conditioned medium from HB-EGF-transfected and control [vector only (VO)] cells using an antibody against the HB-EGF ectodomain (Fig. 1A
). The blot was reprobed with peptide-absorbed antibody to confirm the specificity of the signal (data not shown). No signal was detected in medium from control cells consistent with our previous observation that LNCaP parent cells express very low levels of the HB-EGF precursor, proHB-EGF (21).
|
, P < 0.05 at all time points). These findings are consistent with our previous identification of HB-EGF as a mitogen for LNCaP (21), and further demonstrate that HB-EGF confers a growth advantage under androgen-depleted conditions. To assess the involvement of the AR in HB-EGF-stimulated proliferation, the growth assay was performed in the absence or presence of the antiandrogen Casodex (bicalutamide). Casodex binds to the AR, thereby preventing dissociation of the heat-shock protein complex that maintains the AR in an inactive conformation in the absence of ligand (27). In contrast to the antiandrogen hydroxyflutamide, which has agonist activity for the mutated AR present in LNCaP (3), Casodex behaves as an AR antagonist in this cell background (4, 28). As shown in Fig. 1C, Casodex inhibited HB-EGF-stimulated LNCaP proliferation in a dose-dependent manner (*, P = 0.017; **, P = 0.0008), suggesting that the proliferative response to HB-EGF under these conditions requires AR transcriptional activity.
Expression of soluble HB-EGF promotes androgen-independent growth in vivo
The ability of LNCaP/sHB and LNCaP/VO cells to form androgen-independent tumors was evaluated by sc implantation of cells in a Matrigel suspension into intact SCID mice, or 1 wk following castration. The most dramatic difference between HB-EGF-expressing cells and control cells was in the extent of tumor take, i.e. the number of tumors formed from the number of sites injected (Fig. 2A). LNCaP/sHB cells displayed 75% tumor take compared with 25% take for control tumors (P = 0.0066) at 5 wk post implantation, with a similar pattern observed at the 6 (P = 0.014) and 7 wk (P = 0.022) time points. Comparable results were obtained in intact animals (data not shown) with 91% take in the LNCaP/sHB group compared with 51% for LNCaP/VO (P = 0.0002). The mean tumor volume of LNCaP/sHB tumors in castrates did not differ significantly from those of LNCaP/VO tumors at 5 wk post implantation. However, at the 6- and 7-wk time points, the mean tumor volume (Fig. 2B) was significantly higher in LNCaP/sHB tumors compared with LNCaP/VO tumors (P < 0.0001 for tumor burden; P < 0.03 for tumor volume).
|
). In castrated animals, NSE expression was also higher in LNCaP/sHB tumors compared with LNCaP/VO tumors (Fig. 3B), with the effect observed in several tumors per animal. A subset of tumors was also analyzed for expression of another NE marker, chromogranin A. As shown in Fig. 3C, the expression pattern of chromogranin A in these tumors was comparable to that of NSE, confirming up-regulation of the NE phenotype in LNCaP xenografts.
|
), suggested that testicular androgens are not required for induction of the NE phenotype. Furthermore, LNCaP/sHB tumors from castrated hosts displayed reduced AR expression when compared with LNCaP/VO tumors (Fig. 3B), suggesting that the AR axis may be dispensable for NSE expression.
To evaluate the possibility that a functional AR was not required for NSE expression, LNCaP/sHB cells were grown under androgen-depleted conditions in vitro in the absence and presence of the specific AR inhibitor, Casodex, and assayed for NSE expression over time. As shown in Fig. 4A, NSE expression in LNCaP/sHB cells was not blocked by Casodex, indicating that expression of this NE marker is not dependent on the DNA-binding activity of the AR. In addition, PC-3 PCa cells, which do not express the AR, nevertheless show robust expression of NSE (Fig. 4B), the level of which could be modestly up-regulated in a dose- and time-dependent manner by addition of HB-EGF.
|
, LNCaP/sHB cells cultured either in serum-free medium or in medium supplemented with 1% CSS consistently expressed less AR protein than LNCaP/VO control cells. To confirm this finding, LNCaP cells were treated with exogenous recombinant HB-EGF, which resulted in a time-dependent down-regulation of the AR (Fig. 5B). Taken together, these data indicate that the HB-EGF-stimulated increase in NE marker expression in PCa cells occurs independently of the AR and, further, that HB-EGF can actively decrease levels of AR protein, suggesting that the growth factor has the ability to antagonize AR function.
|
), the response of LNCaP/sHB cells to 10 nM DHT was dramatically decreased compared with that of LNCaP/VO cells under the same conditions. As shown in Fig. 6, LNCaP/sHB cells displayed on average approximately 2.4-fold stimulation of luciferase activity over baseline in response to DHT compared with approximately 6-fold stimulation of luciferase activity in DHT-treated LNCaP/VO control cells (P = 0.0097 for HB-EGFa and P = 0.0024 for HB-EGFb). In all cases, DHT-stimulated luciferase activity was reduced to baseline with 1 µM Casodex. These data, along with the above results that HB-EGF lowers levels of AR protein, indicate that the AR can be functionally antagonized under conditions of continuous exposure to HB-EGF.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In a recent study with striking parallels to our own, Russell and co-workers (29) transfected LNCaP cells with an expression construct encoding the potent mitogen, fibroblast growth factor-2 (FGF-2), to evaluate a potential role for this protein in acquisition of androgen independence. Surprisingly, LNCaP/FGF-2 transfectants displayed only a modest increase in proliferation rate relative to controls in vitro. In vivo, LNCaP/FGF-2 transfectants implanted in intact males showed no difference in growth rate or tumor volume relative to controls; cells implanted into female mice failed to form tumors (29). In contrast to our study, where HB-EGF promoted androgen-independent growth in LNCaP cells and xenografts, overexpression of FGF-2 did not render LNCaP cells androgen independent or enhance their tumorigenicity, suggesting that FGF-2 is unlikely to mediate acquisition of androgen independence in LNCaP cells (29). Interestingly FGF-2 was shown previously to decrease AR protein levels and to reduce sensitivity to DHT in LNCaP cells (30), in support of our assertion that a soluble growth factor can mediate signals that bypass the AR. An important distinction between these two factors, however, is that HB-EGF-induced AR down-regulation was associated in our study with a more aggressive phenotype.
FGF-7/keratinocyte growth factor (KGF) has also been tested for its ability to promote androgen independence in PCa cells. KGF was shown to stimulate the AR in the absence of androgen in PCa cells in culture (8), suggesting that it may elicit androgen-independent effects in prostate tumor cells. Prostate epithelial cells engineered to overexpress KGF displayed increased proliferation, anchorage-independent growth and increased invasive potential (31); however, these cells were not tumorigenic in mice. Although KGF expression is increased in hormone-insensitive prostate tumors, there is as yet no association with tumor grade or stage (32), and serum KGF levels are higher in patients with benign prostatic hyperplasia than with PCa (33). Thus, the precise role of KGF in PCa progression remains unclear.
Recent epidemiologic evidence has established a link between elevated plasma levels of IGF-1, and PCa (34), and increases in IGF-1 and IGF1-receptor mRNA have been described in androgen-independent tumors relative to their androgen-dependent counterparts (35). Although these data indicate an association between components of the IGF signaling axis and progression of PCa to androgen independence, the ability of IGF-1 to promote acquisition of androgen independence remains undemonstrated. It should be noted, however, that when the IGF binding molecule, IGF binding protein-5 (IGFBP-5), was overexpressed in LNCaP, the resulting tumors progressed to androgen independence more rapidly than control tumors following castration of host animals (36). Furthermore, antisense oliognucleotides to IGFBP-5 inhibited IGFBP-5-stimulated androgen-independent tumor growth (37), suggesting an important role for this protein in disease progression.
At 5 wk post implantation in castrated hosts, LNCaP/sHB xenografts showed significantly higher tumor take than controls, but essentially no difference in tumor volume. This suggests that the primary in vivo function of HB-EGF expressed in this model system was to promote cell survival. This conclusion is consistent with our previous demonstration that several EGF-like growth factors, including HB-EGF, can exert a survival function in LNCaP cells (38). In time, however, LNCaP/sHB xenografts displayed increased growth, with the mean volume of LNCaP/sHB tumors significantly greater than that of controls at the 6- and 7-wk time points of our study, suggesting an additional contribution of this growth factor to cell growth control independent of its effects on cell survival.
LNCaP/sHB tumors also expressed higher levels of the NE marker, NSE, compared with control tumors in both castrated and intact hosts, consistent with previous in vitro findings (23). Although the significance of NE differentiation in prostate adenocarcinoma is not clear, the NE phenotype has been associated with androgen-independent, aggressive disease (39, 40, 41). Interestingly, NE cells typically do not express the AR (39, 40, 41, 42, 43), suggesting one reason for failure of hormonal therapy in PCa treatment (44, 45, 46). We found that LNCaP/sHB tumors in castrated mice expressed reduced amounts of AR protein compared with control tumors, consistent with published findings describing low or absent AR expression by NE cells. Similarly, in vitro, AR expression was decreased in LNCaP/sHB cells compared with controls, and likewise in LNCaP parent cells treated with recombinant HB-EGF. Neither constitutive nor HB-EGF-stimulated NSE expression was blocked by Casodex, suggesting that the NE phenotype is independent of the transcriptional activity of the AR. Our finding here that increased tumor growth coincides with promotion of an NE phenotype confirms the results of our previous study, which demonstrated that, unlike IL-6-induced NE differentiation, the HB-EGF-induced NE phenotype in LNCaP was not associated with cell-cycle arrest (23). This finding indicates that stimulating the ErbB axis may provoke a more aggressive, AR-inhibited phenotype that coincides with continued expansion of the tumor compartment.
The HER2 (neu/ErbB2) receptor tyrosine kinase has been proposed to mediate progression to androgen independence through modulation of AR function (47). That study demonstrated that overexpression of HER2 in LNCaP increased androgen-independent proliferation in vitro, promoted tumor take and growth in castrated hosts in vivo and up-regulated the activity of an AR-responsive promoter-reporter construct in an AR-dependent manner. Other studies (12) have suggested that AR-dependent signaling downstream of the ErbB receptor family may be pivotal in tumor progression, a concept supported by our demonstration that HB-EGF, an ErbB1 ligand, promotes androgen-independent growth. Based on its ability to activate ErbB/HER heterodimers, HB-EGF may mediate activation of HER2, thereby contributing to modulation of AR function. Importantly, however, we have also identified additional activities contributed by HB-EGF in LNCaP cells that are distinct from those reported for HER2. These include up-regulation of NSE in vitro and in vivo, as well as functional down-regulation of the AR. Thus, despite the widespread belief that the AR may be necessary for and/or involved in continued tumor cell survival and growth in hormone-refractory PCa (48) (49, 50, 51, 52), our data strongly suggest that growth factor-induced signals may bypass the androgen-AR axis altogether to promote survival, tumor expansion, and a more aggressive phenotype in an androgen-depleted host.
In summary, we have presented a new model of stromal-epithelial signaling by subjecting the PCa cell line, LNCaP, to sustained stimulation by soluble HB-EGF, a factor synthesized predominantly by the stroma SMC in the human prostate. Using this approach we asked whether continuous exposure to HB-EGF could alter the dependence of LNCaP on the androgen-AR axis for survival and proliferation. Our findings demonstrate that HB-EGF is capable of promoting a more aggressive phenotype in vivo and exerts effects that bypass both androgen- and AR-dependent signaling. These observations emphasize the potential importance of stroma-derived signals in the progression of PCa to an androgen-independent state and suggest that therapeutic benefit may be achieved by targeting the ErbB-ligand axis in hormone refractory PCa.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
Abbreviations: AR, Androgen receptor; CSS, charcoal-stripped serum; DHT, dihydrotestosterone; DMSO, dimethylsulfoxide; Erk, extracellular signal regulated kinase; FBS, fetal bovine serum; FGF, fibroblast growth factor; HB-EGF, heparin-binding epidermal growth factor-like growth factor; IGFBP-5, IGF binding protein-5; KGF, keratinocyte growth factor; MMTV-LTR, mouse mammary tumor virus-long terminal repeat; MTT, methylthiazoletetrazolium; NE, neuroendocrine; NSE, neuron-specific enolase; PCa, prostate cancer; RPMI, Roswell Park Memorial Institute; SCID, severe combined immunodeficient; sHB, soluble, processed form of HB-EGF; SMC, smooth muscle cells; VO, vector only.
Received May 29, 2002.
Accepted for publication September 4, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
 |
|
 |
|
  D. Di Vizio, J. Kim, M. H. Hager, M. Morello, W. Yang, C. J. Lafargue, L. D. True, M. A. Rubin, R. M. Adam, R. Beroukhim, et al. Oncosome Formation in Prostate Cancer: Association with a Region of Frequent Chromosomal Deletion in Metastatic Disease Cancer Res., July 1, 2009; 69(13): 5601 - 5609. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Cai, D. C. Portnoy, H. Wang, X. Jiang, S. Chen, and S. P. Balk Androgen Receptor Expression in Prostate Cancer Cells Is Suppressed by Activation of Epidermal Growth Factor Receptor and ErbB2 Cancer Res., June 15, 2009; 69(12): 5202 - 5209. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. K. Mukhopadhyay, J. Kim, B. Cinar, A. Ramachandran, M. H. Hager, D. Di Vizio, R. M. Adam, M. A. Rubin, P. Raychaudhuri, A. De Benedetti, et al. Heterogeneous Nuclear Ribonucleoprotein K Is a Novel Regulator of Androgen Receptor Translation Cancer Res., March 15, 2009; 69(6): 2210 - 2218. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T.-C. Yuan, S. Veeramani, and M.-F. Lin Neuroendocrine-like prostate cancer cells: neuroendocrine transdifferentiation of prostate adenocarcinoma cells Endocr. Relat. Cancer, September 1, 2007; 14(3): 531 - 547. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Wu and J. Huang Phosphatidylinositol 3-Kinase-AKT-Mammalian Target of Rapamycin Pathway Is Essential for Neuroendocrine Differentiation of Prostate Cancer J. Biol. Chem., February 9, 2007; 282(6): 3571 - 3583. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Mimeault and S. K. Batra Recent advances on multiple tumorigenic cascades involved in prostatic cancer progression and targeting therapies Carcinogenesis, January 1, 2006; 27(1): 1 - 22. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z Culig, H Steiner, G Bartsch, and A Hobisch Mechanisms of endocrine therapy-responsive and -unresponsive prostate tumours Endocr. Relat. Cancer, June 1, 2005; 12(2): 229 - 244. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. R. Stewart and C. A. O'Brian Protein kinase C-{alpha} mediates epidermal growth factor receptor transactivation in human prostate cancer cells Mol. Cancer Ther., May 1, 2005; 4(5): 726 - 732. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Cinar, A. De Benedetti, and M. R. Freeman Post-Transcriptional Regulation of the Androgen Receptor by Mammalian Target of Rapamycin Cancer Res., April 1, 2005; 65(7): 2547 - 2553. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Kim, R. M. Adam, K. R. Solomon, and M. R. Freeman Involvement of Cholesterol-Rich Lipid Rafts in Interleukin-6-Induced Neuroendocrine Differentiation of LNCaP Prostate Cancer Cells Endocrinology, February 1, 2004; 145(2): 613 - 619. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Bookout, A. E. Finney, R. Guo, K. Peppel, W. J. Koch, and Y. Daaka Targeting G{beta}{gamma} Signaling to Inhibit Prostate Tumor Formation and Growth J. Biol. Chem., September 26, 2003; 278(39): 37569 - 37573. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
