Heparin-binding epidermal growth factor-like growth factor functionally antagonizes interstitial cystitis antiproliferative factor via mitogen-activated protein kinase pathway activation.
OBJECTIVE
To delineate the mechanism underlying the potential functional relationship between interstitial cystitis antiproliferative factor (APF) and heparin-binding epidermal growth factor-like growth factor (HB-EGF), as APF has previously been shown to decrease the proliferation rate of normal bladder epithelial cells and the amount of HB-EGF produced by these cells.


METHODS
APF-responsive T24 transitional carcinoma bladder cells were treated with high-pressure liquid chromatography-purified native APF with or without HB-EGF to determine the involvement of signalling pathways and proliferation by Western blot analysis, p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (Erk)/MAPK assays, and 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay.


RESULTS
Cyclic stretch induced the secretion of HB-EGF from T24 cells overexpressing the HB-EGF precursor, resulting in enhanced proliferation. T24 cells treated with APF had increased p38MAPK activity and suppressed cell growth, events that were both reversed by treatment with a p38MAPK-selective inhibitor. Activation of Erk/MAPK by HB-EGF was inhibited by APF, and APF did not stimulate p38MAPK in the presence of soluble HB-EGF or when cells overexpressed constitutively secreted HB-EGF. Lastly, APF inhibitory effects on cell growth were attenuated by HB-EGF.


CONCLUSIONS
These results indicate that HB-EGF and APF are functionally antagonistic and signal through parallel MAPK signalling pathways in bladder cells.
Kim
Jayoung
J
The Urological Diseases Research Center, Children's Hospital Boston, Boston, MA, USA. ja.kim@childrens.harvard.edu
Keay
Susan K
SK
Freeman
Michael R
MR
D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D018856:Cystitis, Interstitial / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects; D006023:Glycoproteins / Q000037:antagonists & inhibitors*; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D001743:Urinary Bladder / Q000187:drug effects
D006023:Glycoproteins; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; C490708:antiproliferative factor APF, human; D020928:Mitogen-Activated Protein Kinases