Antiproliferative factor decreases Akt phosphorylation and alters gene expression via CKAP4 in T24 bladder carcinoma cells
© Shahjee et al; licensee BioMed Central Ltd. 2010
Received: 8 October 2010
Accepted: 10 December 2010
Published: 10 December 2010
Urinary bladder cancer is a common malignancy worldwide, and outcomes for patients with advanced bladder cancer remain poor. Antiproliferative factor (APF) is a potent glycopeptide inhibitor of epithelial cell proliferation that was discovered in the urine of patients with interstitial cystitis, a disorder with bladder epithelial thinning and ulceration. APF mediates its antiproliferative activity in primary normal bladder epithelial cells via cytoskeletal associated protein 4 (CKAP4). Because synthetic asialo-APF (as-APF) has also been shown to inhibit T24 bladder cancer cell proliferation at nanomolar concentrations in vitro, and because the peptide segment of APF is 100% homologous to part of frizzled 8, we determined whether CKAP4 mediates as-APF inhibition of proliferation and/or downstream Wnt/frizzled signaling events in T24 cells.
T24 cells were transfected with double-stranded siRNAs against CKAP4 and treated with synthetic as-APF or inactive control peptide; cells that did not undergo electroporation and cells transfected with non-target (scrambled) double-stranded siRNA served as negative controls. Cell proliferation was determined by 3H-thymidine incorporation. Expression of Akt, glycogen synthase kinase 3β (GSK3β), β-catenin, p53, and matrix metalloproteinase 2 (MMP2) mRNA was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Akt, GSK-3β, MMP2, β-catenin, and p53 protein expression, plus Akt, GSK-3β, and β-catenin phosphorylation, were determined by Western blot.
T24 cell proliferation, MMP2 expression, Akt ser473 and thr308 phosphorylation, GSK3β tyr216 phosphorylation, and β-catenin ser45/thr41 phosphorylation were all decreased by APF, whereas p53 expression, and β-catenin ser33,37/thr41 phosphorylation, were increased by APF treatment in non-electroporated and non-target siRNA-transfected cells. Neither mRNA nor total protein expression of Akt, GSK3β, or β-catenin changed in response to APF in these cells. In addition, the changes in cell proliferation, MMP2/p53 mRNA and protein expression, and Akt/GSK3β/β-catenin phosphorylation in response to APF treatment were all specifically abrogated following CKAP4 siRNA knockdown.
Synthetic as-APF inhibits cell proliferation in T24 bladder carcinoma cells via the CKAP4 receptor. The mechanism for this inhibition involves regulating phosphorylation of specific cell signaling molecules (Akt, GSK3β, and β-catenin) plus mRNA and protein expression of p53 and MMP2.
Bladder cancer is the second most common genitourinary malignancy and the fourth most common malignancy in men in the United States, causing over 12,000 deaths annually . Although seventy percent of cases are diagnosed in the superficial stage, up to 30% can present with or develop muscle-invasive disease, and long term outcomes for patients with advanced bladder cancer remain poor [2, 3]. Additional treatments that prevent or control the progression of bladder carcinoma are therefore sorely needed.
Altered expression of certain genes commonly found in human carcinomas are also found in bladder cancer, including decreased expression of E-cadherin [4–8] and the tumor suppressors p53 and p21 [9–11], with increased expression of heparin-binding epidermal growth factor-like growth factor (HB-EGF) . Of these abnormalities, decreased E-cadherin and increased HB-EGF expression appear to be particularly closely associated with increased tumor progression, cell proliferation, and/or metastasis [5–8, 12–15]. Therapies aimed at controlling the aberrant expression of genes associated with tumor progression and metastasis in bladder carcinoma cells may be helpful for controlling disease.
Our laboratory previously discovered a natural antiproliferative factor (APF) [16–18] that profoundly inhibits bladder epithelial cell proliferation [19, 20], upregulates E-cadherin , p53 and p21  expression, and inhibits the production of other cell proteins including HB-EGF [17, 20, 21, 23]. APF is secreted specifically by bladder epithelial cells from patients with interstitial cystitis (IC), a chronic bladder disorder characterized by bladder epithelial thinning and/or ulceration [24–26]. APF is a low molecular weight frizzled 8-related glycopeptide that inhibits both normal and IC bladder epithelial cell proliferation via cytoskeleton associated protein 4 (CKAP4, also known as CLIMP-63 and ERGIC-63) , a type II transmembrane receptor  whose palmitoylation appears to be required for mediating APF activity in HeLa cells . Synthetic asialo-APF (as-APF) inhibits T24 bladder carcinoma cell proliferation in vitro at low (nanomolar) concentrations similar to those required for inhibition of normal bladder epithelial cell proliferation . However, neither the role of CKAP4 in regulation of bladder carcinoma cell proliferation, nor its role in mediating APF activity in bladder carcinoma cells, has yet been studied.
Therefore, to better understand the mechanism by which APF regulates T24 bladder carcinoma cell proliferation, we determined the effect of as-APF on the expression or activation of enzymes involved in wingless-int (Wnt)/frizzled signaling (including AKR-transforming enzyme (Akt), glycogen synthase kinase-3 beta (GSK3β), β-catenin, and matrix metalloprotease 2 (MMP2), as well as the role of CKAP4 in mediating as-APF activity in T24 cells.
T24 human urinary bladder cancer cells (ATCC HTB-4) were grown to 60-80% confluence in McCoy's 5A medium (Invitrogen, Carlsbad, CA) containing 10% heat-inactivated fetal bovine serum (FBS), 1% antibiotic/antimycotic solution, 1% L-glutamine (all from Sigma, St. Louis, MO) and 2.2 grams/L sodium bicarbonate (Invitrogen), in a 37°C/5% CO2 atmosphere.
Double-stranded siRNA corresponding to nucleotides 594-616 of CKAP4 (5'-AACUUUUGAGUCCAUCUUGAGAA-3' sense strand) and a scrambled double-stranded negative control siRNA (5'-AAUUCUGUAUGCUACCUGUAGAA-3' sense strand) were prepared by preincubating single-stranded sense and antisense strands prepared with double A overhangs in serum-free McCoy's 5A medium at 37°C for 1 hour. T24 human bladder cancer cells were trypsinized for 10 minutes at room temperature, centrifuged in growth medium (as defined above), and the cell pellet was resuspended in serum-free medium at a density of 1 × 106 cells/ml. Two hundred microliters of the cell suspension were then transferred to a sterile 2-mm cuvette with 14 μg of CKAP4 siRNA, scrambled non-target siRNA, or no siRNA, and electroporated at 160 V/500 microfarad capacitance using a Bio-Rad Gene Pulser Xcell. The cells were then immediately transferred to T75 cell culture flasks (Corning Incorporated, Corning, NY) (for extraction of RNA and protein) or to 96 well tissue culture plates (Corning Incorporated) (for the cell proliferation assay) and incubated in growth medium overnight in a 37°C/5% CO2 atmosphere.
APF Treatment (for RNA and Protein Extraction)
Following overnight incubation in growth medium, transfected T24 human bladder cancer cells were further incubated with serum-free McCoy's 5A medium for the next 24 hours, after which they were treated with 500 nM as-APF or 500 nM inactive nonglycosylated peptide control (both from PolyPeptide Laboratories, Incorporated, San Diego, CA). Cells were then incubated for an additional 48 hrs in a 37°C/5% CO2 atmosphere prior to RNA and protein extraction.
Following cell incubation with as-APF or its control peptide/diluent, the culture medium was removed, T24 cells were washed with 1× PBS, and RNA was extracted using the RNeasy Plus Mini Kit (Qiagen, Valencia, CA) according to the manufacturer's instructions. RNA concentration was measured at 260 nM in a UV/VIS spectrophotometer from Perkin Elmer. Extracted RNA was stored at -80°C.
Cell culture medium was removed from duplicate flasks, T24 cells were scraped into ice-cold PBS, and the cell slurry was centrifuged at 4°C for 5 minutes at 2000 rpm. Supernatant was then removed and the pellet was washed with ice-cold PBS and centrifuged again at 4°C for 5 minutes at 2000 rpm. This pellet was then resuspended in ice-cold RIPA buffer (Upstate Cell Signaling Solutions, Temecula, CA) containing Complete Protease Inhibitor Cocktail (Roche, Indianapolis, IN) and centrifuged at 14,000 rpm for 15 minutes at 4°C. Supernatant containing total cell protein was collected and stored at -80°C.
3H-Thymidine Cell Proliferation Assay
Cell proliferation was measured by 3H-thymidine incorporation into T24 human bladder cancer cells, plating 1.5 ×103 cells/well onto a 96-well cell culture plate (Corning Incorporated), in 150 μL/well McCoy's 5A medium containing 10% heat inactivated FBS, 1% antibiotic/antimycotic solution, 1% L-glutamine, and plus 2.2 grams/L sodium bicarbonate. The next day, cell growth medium was removed and replaced with 100 μl serum-free McCoy's medium. On the third day, synthetic as-APF was resuspended in acetonitrile/distilled water (1:1) and applied to the cells in serum-free McCoy's medium at varying concentrations; cell controls received acetonitrile/distilled water diluted in serum-free McCoy's medium (same final concentration of diluent). Cells were then incubated at 37°C in a 5% CO2 atmosphere for an additional 48 hours, after which they were labeled with 1 μCi per well 3H-thymidine at 37°C in a 5% CO2 atmosphere for 4 hours. The cells were then treated with trypsin-EDTA (Invitrogen), insoluble cell contents harvested and methanol-fixed onto glass fiber filter paper, and the amount of radioactivity incorporated determined using a Beckman scintillation counter. Significant inhibition of 3H-thymidine incorporation was defined as a decrease in cpm of >2 SD from the mean of control cells for each plate.
Gene expression was determined using SYBR® Green based real-time RT-PCR, QuantiTect® primers and reagents (Qiagen) and a Roche 480 LightCycler. Samples were tested in triplicate runs, and specific mRNA levels quantified and compared to mRNA levels for β-actin or GAPDH using Roche LC480 real-time PCR analysis software (version 1.5.0). Predetermined optimal concentrations of RNA were used for each set of primers. p53 (QT00060235), Akt (QT00085379), GSK3β (QT00057134), β-catenin (QT00077882), MMP2 (QT00088396), GAPDH (QT01192646), and β-actin (QT1680476) primer sets were obtained from Qiagen. p53 served as a standard control for APF activity, while GAPDH and β-actin served as standard controls for the qRT-PCR procedure.
SDS Polyacrylamide Gel Electrophoresis and Western Blot Assay
Specific protein expression or phosphorylation was determined by Western blot. Protein concentration was measured using a Folin reagent-based protein assay kit (Bio-Rad, Hercules, CA). Solubilized cell proteins were incubated for 10 min at 70°C in sample reducing buffer, each lane was loaded with 30 μg of protein, and proteins were separated by electrophoresis using 4-12% NuPAGE NOVEX BisTris polyacrylamide gels (Invitrogen) in MOPS/SDS running buffer (Invitrogen), according to the manufacturer's instructions. Proteins were then transferred to nitrocellulose membranes (Invitrogen) according to the NuPAGE gel manufacturer's protocol for Western transfer (30 V constant voltage for 1 h). Following protein transfer, the nitrocellulose membranes were blocked with 5% nonfat dry milk in TBS-T buffer (Tris-buffered saline, pH 7.4, with 0.1% Tween 20) and incubated overnight at 4°C in TBS-T buffer containing mouse monoclonal anti-CKAP4 ("anti-CLIMP-63," clone G1/296) (Alexis Biochemical, Plymouth Meeting, PA), anti-p53 (Calbiochem, San Diego, CA), anti-GSK3β (BD Biosciences, San Jose, CA), anti-phosphoGSK3β (tyr 216) (BD Biosciences), or anti-β actin (Sigma) antibodies; or rabbit polyclonal anti-MMP2, anti-Akt, anti-phosphoAkt (ser473/thr308), anti-phosphoGSK3β (ser9), anti-β-catenin, anti-phosphoβ-catenin (ser 33,37/thr 41), or anti-phosphoβ-catenin (ser 45/thr 41) (all obtained from Cell Signaling Technology, Danvers, MA). When more than one antibody was used for binding to proteins on a single membrane, the membrane was stripped between antibody incubations using Restore PLUS Western blot stripping buffer (Pierce, Rockford, IL) according to the manufacturer's instructions. The membranes were subsequently washed three times with TBS-T, incubated with horseradish peroxidase-conjugated goat anti-mouse or goat anti-rabbit IgG secondary antibodies (Santa Cruz Biotechnology, Santa Cruz, CA) for 1 h at room temperature, and developed with ECL chemiluminescence Reagent (Amersham Biosciences, Piscataway, NJ). p53 expression served as a positive control for APF activity; β-actin expression served as a standard control for the Western blot procedure.
Significant inhibition of 3H-thymidine incorporation was defined as a mean decrease in cpm of ± 2 SD from the mean of control cells for each plate. Crossover point analysis was performed for qRT-PCR data, and mRNA copy number for each gene was quantified relative to β-actin; this value is expressed as mean ± standard error of the mean (SEM) for duplicate runs performed on three separate occasions. The significance of the difference between mean values was determined by an analysis of variance with p < .05 considered significant.
siRNA knockdown of CKAP4 expression inhibits APF antiproliferative activity in T24 bladder carcinoma cells
APF increases p53 tumor suppressor gene expression via CKAP4 in T24 cells
Decreased Akt (serine 473 and threonine 308) phosphorylation following APF treatment of T24 cells
Decreased GSK3β (tyrosine 216) and β-catenin (serine 45/threonine 41) phosphorylation, but increased β-catenin (serine 33, 37/threonine 41) phosphorylation, in response to APF
Downregulation of MMP2 expression by APF in T24 bladder cancer cells via CKAP4
Wnt/frizzled signaling is also known to stimulate cellular production of specific gelatinases including MMP2 [31, 32] which has been implicated in HB-EGF activation and cleavage  as well as the progression and/or occurrence of various cancers including bladder cancer [34–37]. As the expression of MMP2 is also known to be stimulated by HB-EGF in carcinoma cells , we next determined whether as-APF also regulated MMP2 expression in T24 cells.
The current study shows that APF mediates its antiproliferative effects in T24 bladder carcinoma cells via the CKAP4 transmembrane receptor, as found previously for normal bladder epithelial cells . Further, it indicates that the mechanism whereby APF inhibits bladder carcinoma cell proliferation via CKAP4 involves the regulation of phosphorylation (with activation or inactivation) of various cell signaling molecules including Akt, GSK3β, β-catenin, along with mRNA and protein expression of p53 and MMP2.
CKAP4, which was first described as a reversibly palmitoylated type II transmembrane receptor , was previously shown to bind the synthetic form of a natural bladder epithelial cell antiproliferative factor (as-APF) and mediate its effects on normal bladder epithelial cell proliferation . Results from the current study show that the CKAP4 receptor is also required for inhibition of bladder carcinoma cell proliferation by as-APF in vitro. In addition, experiments performed to elucidate the mechanism of APF activity indicate that this frizzled 8-related glycopeptide induces altered expression or phosphorylation of certain proteins that differ in some aspects from those seen in canonical Wnt/frizzled signaling.
Downstream signal transducers for Wnt/frizzled signaling include Akt, GSK3β, and β-catenin . The serine threonine kinase Akt, also known as protein kinase B (PKB), is a central regulator of cell proliferation, motility and survival whose activity is often altered in human malignancies . Akt mediates its downstream effects via phosphorylation/inactivation of GSK3β ser9, with subsequently decreased phosphorylation of the GSK3β target β-catenin, resulting in increased β-catenin nuclear translocation, binding to T-cell factor, and stimulation of gene expression related to cell proliferation and survival [30, 41]. In addition to its association with malignant cell proliferation, increased Akt phosphorylation/activation has also been linked to the invasive properties of bladder cancer cells . The inhibition of Akt ser473 and thr308 phosphorylation by APF suggests that APF may profoundly inhibit bladder epithelial cell Akt activity, and therefore decrease bladder carcinoma cell invasive potential, as well.
GSK3β activity is reduced by phosphorylation of ser9 but stimulated by phosphorylation on tyr216 , and the downstream effects of Akt activation/phosphorylation during Wnt/frizzled signaling include increased ser9 phosphorylation with decreased activity of GSK3β, decreased GSK3β-inducedβ-catenin ser33,37 phosphorylation, and subsequently decreased β-catenin ubiquitination and degradation. If as-APF mediated its activity in T24 cells purely by inhibiting canonical Wnt/frizzled signaling (like other secreted frizzled-related cell growth inhibitors), GSK3β ser9 phosphorylation should have been decreased substantially, while tyr216 phosphorylation (which may be mediated by mitogen-activated protein kinase kinase (MEK) 1/2)  should not have been affected. Our results, which showed only a very minimal decrease in GSK3β ser9 phosphorylation, but a substantial decrease in GSK3β yr216 phosphorylation, indicate that as-APF: 1) does not mediate its activity purely by regulating Wnt/frizzled canonical signaling; 2) may inhibit GSK3β and additional kinases (such as MEK 1/2); and 3) may mediate its antiproliferative effects in T24 cells via inhibition of Akt, GSK3β, and/or MEK1/2 involving downstream effects on targets in addition to β-catenin. Indeed, the modest increase in apparent phosphorylation of β-catenin ser33,37/thr41, along with a decrease in phosphorylation of β-catenin ser45 (which is mediated by autophosphorylation, casein kinase 1, and/or a complex of cyclin D1/cyclin-dependent kinase 6, and which primes ser33,37 for phosphorylation by GSK3β) [42, 44], suggests that the regulation of total β-catenin protein and/or inhibition of canonical Wnt/frizzled signaling may not be the sole mechanism by which APF induces its effects on cell proliferation and gene expression.
Matrix metalloproteinases (MMPs) are a multigene family of zinc-dependent endopeptidases that degrade extracellular matrix components, whose expression is also regulated via Wnt/frizzled signaling pathways [31, 32] and has been shown to correlate with invasive potential of many different tumors . Expression of MMP2 is associated with bladder carcinoma cell invasion and metastasis [34–37]. The ability of as-APF to significantly inhibit MMP2 mRNA and protein expression in T24 cells also suggests that as-APF may be able to decrease the invasive potential of bladder carcinoma cells as well as inhibit their proliferation.
Previous experiments performed by Jayoung Kim showed that p53 mediated the antiproliferative effects of native APF in both normal and T24 bladder carcinoma cells . The current study confirms this result by showing that synthetic as-APF also increases p53 protein and mRNA expression in T24 cells, and it further demonstrates the role of the CKAP4 receptor in APF-induced p53 upregulation.
Although the expression or activation of each of the cell proteins shown to be modified by APF can be regulated via Wnt/frizzled pathways, the specific alterations seen in Akt/GSK3β/β-catenin phosphorylation and the lack of an effect of APF on total cellular β-catenin levels suggest that this secreted frizzled-related peptide does not inhibit T24 bladder cell proliferation solely via inhibition of canonical Wnt/frizzled signaling. Whether the CKAP4 receptor can mediate transmembrane signaling, and/or whether it functions as a chaperone protein for cytoplasmic or nuclear translocation of APF, is unknown [27, 29]. However, the myriad effects of APF on cell protein activation and expression discovered in the current as well as previous studies [19, 21] indicate it may inhibit cell proliferation by regulating the activity of more than one signaling pathway or transcriptional regulatory factor.
The ability of as-APF to inhibit GSK3β tyr216 phosphorylation without inhibiting GSK3β ser9 phosphorylation suggests it may also be a potent GSK3β enzyme inhibitor in T24 cells. Recent studies on natural compound GSK3β inhibitors suggest that this class of drugs may be promising for the regulation of certain cancers . Additional in vitro and in vivo studies with this intriguing natural frizzled 8-related glycopeptide are in progress to elucidate further its important cell regulatory function(s) as well as its potential as a therapeutic agent.
cytoskeleton-associated protein 4
fetal bovine serum
quantitative reverse transcriptase polymerase chain reaction
heparin-binding epidermal growth factor-like growth factor
small interfering ribonucleic acid
glycogen synthase kinase
glyceraldehyde phosphate dehydrogenase
small interfering RNA
The authors thank Eunice Katz for her assistance with the preparation of this manuscript. This material is based upon work supported by the Office of Research and Development (Medical Research Service), Department of Veterans Affairs.
- Jemal A, Siegel R, Ward E, Murray T, Xu J, Thun MJ: Cancer statistics, 2007. CA Cancer J Clin. 2007, 57: 43-66. 10.3322/canjclin.57.1.43.View ArticleGoogle Scholar
- Kaufman DS, Shipley WU, Feldman AS: Bladder cancer. Lancet. 2009, 74: 239-249. 10.1016/S0140-6736(09)60491-8.View ArticleGoogle Scholar
- Sonpavde G, Sternberg CN: Treatment of metastatic urothelial cancer: opportunities for drug discovery and development. BJU Int. 2008, 102: 1354-1360. 10.1111/j.1464-410X.2008.07982.x.View ArticleGoogle Scholar
- Lipponen PK, Eskelinen MJ: Reduced expression of E-cadherin is related to invasive disease and frequent recurrence in bladder cancer. J Cancer Res Clin Oncol. 1995, 121: 303-308. 10.1007/BF01209598.View ArticleGoogle Scholar
- Syrigos KN, Krausz T, Waxman J, Pandha H, Rowlinson-Busza G, Verne J, Epenetos AA, Pignatelli M: E-cadherin expression in bladder cancer using formalin-fixed, paraffin-embedded tissues: correlation with histopathological grade, tumour stage and survival. Int J Cancer. 1995, 64: 367-370. 10.1002/ijc.2910640603.View ArticleGoogle Scholar
- Wakatsuki S, Watanabe R, Saito K, Saito T, Katagiri A, Sato S, Tomita Y: Loss of human E-cadherin (ECD) correlated with invasiveness of transitional cell cancer in renal pelvis, ureter and urinary bladder. Cancer Lett. 1996, 103: 11-17. 10.1016/0304-3835(96)04194-8.View ArticleGoogle Scholar
- Erdemir F, Ozcan F, Kilicaslan I, Parlaktas BS, Uluocak N, Gokce O: The relationship between the expression of E-cadherin and tumor recurrence and progression in high-grade stage T1 bladder urothelial carcinoma. Int Urol Nephrol. 2007, 39: 1031-1037. 10.1007/s11255-006-9159-5.View ArticleGoogle Scholar
- Otto T, Birchmeier W, Schmidt U, Hinke A, Schipper J, Rübben H, Raz A: Inverse relation of E-cadherin and autocrine motility factor receptor expression as a prognostic factor in patients with bladder carcinomas. Cancer Res. 1994, 54: 3120-3123.Google Scholar
- Slaton JW, Benedict WF, Dinney CP: p53 in bladder cancer: mechanism of action, prognostic value, and target for therapy. Urology. 2001, 57: 852-859. 10.1016/S0090-4295(01)00968-2.View ArticleGoogle Scholar
- Nishiyama H, Watanabe J, Ogawa O: p53 and chemosensitivity in bladder cancer. Int J Clin Oncol. 2008, 13: 282-286. 10.1007/s10147-008-0815-x.View ArticleGoogle Scholar
- Stein JP, Ginsberg DA, Grossfeld GD, Chatterjee SJ, Esrig D, Dickinson MG, Groshen S, Taylor CR, Jones PA, Skinner DG, Cote RJ: Effect of p21WAF1/CIP1 expression on tumor progression in bladder cancer. J Natl Cancer Instit. 1998, 90: 1072-1079. 10.1093/jnci/90.14.1072.View ArticleGoogle Scholar
- Thøgersen VB, Sørensen BS, Poulsen SS, Orntoft TF, Wolf H, Nexo E: A subclass of HER1 ligands are prognostic markers for survival in bladder cancer patients. Cancer Res. 2001, 61: 6227-6233.Google Scholar
- Schäfer B, Gschwind A, Ullrich A: Multiple G-protein-coupled receptor signals converge on the epidermal growth factor receptor to promote migration and invasion. Oncogene. 2004, 23: 991-999.View ArticleGoogle Scholar
- Ongusaha PP, Kwak JC, Zwible AJ, Macip S, Higashiyama S, Taniguchi N, Fang L, Lee SW: HB-EGF is a potent inducer of tumor growth and angiogenesis. Cancer Res. 2004, 64: 5283-5290. 10.1158/0008-5472.CAN-04-0925.View ArticleGoogle Scholar
- Adam RM, Danciu T, McLellan DL, Borer JG, Lin J, Zurakowski D, Weinstein MH, Rajjayabun PH, Mellon JK, Freeman MR: A nuclear form of the heparin-binding epidermal growth factor-like growth factor precursor is a feature of aggressive transitional cell carcinoma. Cancer Res. 2003, 63: 484-490.Google Scholar
- Keay S, Zhang C-O, Hise M, Trifillis AL, Hebel JR, Jacobs SC, Warren JW: Decreased 3H-thymidine incorporation by human bladder epithelial cells following exposure to urine from interstitial cystitis patients. J Urol. 1996, 156: 2073-2078. 10.1016/S0022-5347(01)65438-7.View ArticleGoogle Scholar
- Keay S, Kleinberg M, Zhang C-O, Hise MK, Warren JW: Bladder epithelial cells from interstitial cystitis patients produce an inhibitor of HB-EGF production. J Urol. 2000, 164: 2112-2118. 10.1016/S0022-5347(05)66980-7.View ArticleGoogle Scholar
- Keay S, Warren JW, Zhang C-O, Tu LM, Gordon DA, Whitmore KE: Antiproliferative activity is present in bladder but not renal pelvic urine from interstitial cystitis patients. J Urol. 1999, 162: 1487-1489. 10.1016/S0022-5347(05)68345-0.View ArticleGoogle Scholar
- Keay SK, Szekely Z, Conrads TP, Veenstra TD, Barchi JJ, Zhang CO, Koch KR, Michejda CJ: An antiproliferative factor from interstitial cystitis patients is a frizzled 8 protein-related sialoglycopeptide. Proc Natl Acad Sci USA. 2004, 101: 11803-11808. 10.1073/pnas.0404509101.View ArticleGoogle Scholar
- Keay S, Zhang C-O, Shoenfelt JL, Chai TC: Decreased in vitro proliferation of bladder epithelial cells from patients with interstitial cystitis. Urology. 2003, 61: 1278-1284. 10.1016/S0090-4295(03)00005-0.View ArticleGoogle Scholar
- Keay S, Seillier-Moiseiwitsch F, Zhang C-O, Chai TC, Zhang J: Changes in human bladder cell gene expression associated with interstitial cystitis or antiproliferative factor treatment. Physiol Genomics. 2003, 14: 107-115.View ArticleGoogle Scholar
- Kim J, Keay SK, Dimitrakov JD, Freeman MR: p53 mediates interstitial cystitis antiproliferative factor (APF)-induced growth inhibition of human urothelial cells. FEBS Lett. 2007, 581: 3795-3799. 10.1016/j.febslet.2007.06.058.View ArticleGoogle Scholar
- Zhang C-O, Wang JY, Koch KR, Keay S: Regulation of tight junction proteins and bladder epithelial paracellular permeability by an antiproliferative factor from patients with interstitial cystitis. J Urol. 2005, 174: 2382-2387. 10.1097/01.ju.0000180417.11976.99.View ArticleGoogle Scholar
- Johansson SL, Fall M: Clinical features and spectrum of light microscopic changes in interstitial cystitis. J Urol. 1990, 143: 1118-1124.Google Scholar
- Skoluda D, Wegner K, Lemmel EM: Critical Notes: Respective immune pathogenesis of interstitial cystitis (article in German). Urologe A. 1974, 13: 15-23.Google Scholar
- Tomaszewski JE, Landis JR, Russack V, Williams TM, Wang LP, Hardy C, Brensinger C, Matthews YL, Abele ST, Kusek JW, Nyberg LM, Interstitial Cystitis Database Study Group: Biopsy features are associated with primary symptoms in interstitial cystitis: results from the Interstitial Cystitis Database Study Group. Urology. 2001, 57: 67-81. 10.1016/S0090-4295(01)01166-9.View ArticleGoogle Scholar
- Conrads TP, Tocci GM, Hood BL, Zhang CO, Guo L, Koch KR, Michejda CJ, Veenstra TD, Keay SK: CKAP4 is a receptor for the frizzled-8 protein-related antiproliferative factor from interstitial cystitis patients. J Biol Chem. 2006, 281: 37836-37843. 10.1074/jbc.M604581200.View ArticleGoogle Scholar
- Schweizer A, Ericsson M, Bächi T, Griffiths G, Hauri HP: Characterization of a novel 63 kDa membrane protein. Implications for the organization of the ER-to-Golgi pathway. J Cell Sci. 1993, 104: 671-683.Google Scholar
- Planey SL, Keay SK, Zhang C-O, Zacharias DA: Palmitoylation of cytoskeleton associated protein 4 by DHHC2 regulates antiproliferative factor-mediated signaling. Mol Biol Cell. 2009, 20: 1454-1463. 10.1091/mbc.E08-08-0849.View ArticleGoogle Scholar
- Widelitz R: Wnt signaling through canonical and non-canonical pathways: recent progress. Growth Factors. 2005, 23: 111-116. 10.1080/08977190500125746.View ArticleGoogle Scholar
- Zi X, Guo Y, Simoneau AR, Hope C, Xie J, Holcombe RF, Hoang BH: Expression of Frzb/secreted Frizzled-related protein 3, a secreted Wnt antagonist, in human androgen-independent prostate cancer PC-3 cells suppresses tumor growth and cellular invasiveness. Cancer Res. 2005, 65: 9762-9770. 10.1158/0008-5472.CAN-05-0103.View ArticleGoogle Scholar
- Wu B, Crampton SP, Hughes CC: Wnt signaling induces matrix metalloproteinase expression and regulates T cell transmigration. Immunity. 2007, 26: 227-239. 10.1016/j.immuni.2006.12.007.View ArticleGoogle Scholar
- Roelle S, Grosse R, Aigner A, Krell HW, Czubayko F, Gudermann T: Matrix metalloproteinases 2 and 9 mediate epidermal growth factor receptor transactivation by gonadotropin-releasing hormone. J Biol Chem. 2003, 278: 47307-47318. 10.1074/jbc.M304377200.View ArticleGoogle Scholar
- Kanayama H: Matrix metalloproteinases and bladder cancer. J Med Invest. 2001, 48: 31-43.Google Scholar
- Gerhards S, Jung K, Koenig F, Daniltchenko D, Hauptmann S, Schnorr D, Loening SA: Excretion of matrix metalloproteinases 2 and 9 in urine is associated with a high stage and grade of bladder carcinoma. Urology. 2001, 57: 675-679. 10.1016/S0090-4295(00)01087-6.View ArticleGoogle Scholar
- Moses MA, Wiederschain D, Loughlin KR, Zurakowski D, Lamb CC, Freeman MR: Increased incidence of matrix metalloproteinases in urine of cancer patients. Cancer Res. 1998, 58: 1395-1399.Google Scholar
- Papathoma AS, Petraki C, Grigorakis A, Papakonstantinou H, Karavana V, Stefanakis S, Sotsiou F, Pintzas A: Prognostic significance of matrix metalloproteinases 2 and 9 in bladder cancer. Anticancer Res. 2000, 20: 2009-2013.Google Scholar
- Yagi H, Yotsumoto F, Miyamoto S: Heparin-binding epidermal growth factor-like growth factor promotes transcoelomic metastasis in ovarian cancer through epithelial-mesenchymal transition. Mol Cancer Ther. 2008, 7: 3441-10.1158/1535-7163.MCT-08-0417.View ArticleGoogle Scholar
- Li F, Chong ZZ, Maiese K: Winding through the WNT pathway during cellular development and demise. Histol Histopathol. 2006, 21: 103-124.Google Scholar
- Wu X, Obata T, Khan Q, Highshaw RA, DeVere White R, Sweeney C: The phosphatidylinositol-3 kinase pathway regulates bladder cancer cell invasion. BJU Int. 2004, 93: 143-50. 10.1111/j.1464-410X.2004.04574.x.View ArticleGoogle Scholar
- Cheng JQ, Lindsley CW, Cheng GZ, Yang H, Nicosia SV: The Akt/PKB pathway: molecular target for cancer drug discovery. Oncogene. 2005, 24: 7482-7492. 10.1038/sj.onc.1209088.View ArticleGoogle Scholar
- Wang QM, Fiol CJ, DePaoli-Roach AA, Roach PJ: Glycogen synthase kinase-3 beta is a dual specificity kinase differentially regulated by tyrosine and serine/threonine phosphorylation. J Biol Chem. 1994, 269: 14566-14574.Google Scholar
- Takahashi-Yanaga F, Shiraishi F, Hirata M, Miwa Y, Morimoto S, Sasaguri T: Glycogen synthase kinase-3beta is tyrosine-phosphorylated by MEK1 in human skin fibroblasts. Biochem Biophys Res Commun. 2004, 316: 411-415. 10.1016/j.bbrc.2004.02.061.View ArticleGoogle Scholar
- Hagen T, Vidal-Puig A: Characterisation of the phosphorylation of beta-catenin at the GSK-3 priming site Ser45. Biochem Biophys Res Commun. 2002, 294: 324-328. 10.1016/S0006-291X(02)00485-0.View ArticleGoogle Scholar
- Stetler-Stevenson WG: Metalloproteinases and cancer invasion. Semin Cancer Biol. 1990, 1: 99-106.Google Scholar
- Gaisina IN, Gallier F, Ougolkov AV, Kim KH, Kurome T, Guo S, Holzle D, Luchini DN, Blond SY, Billadeau DD, Kozikowski AP: From a natural product lead to the identification of potent and selective benzofuran-3-yl-(indol-3-yl) maleimides as glycogen synthase kinase 3 beta inhibitors that suppress proliferation and survival of pancreatic cancer cells. J Med Chem. 2009, 52: 1853-1863. 10.1021/jm801317h.View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.