Nuclear factor-kappaB mediates angiogenesis and metastasis of human bladder cancer through the regulation of interleukin-8.
OBJECTIVE
Interleukin (IL)-8 is an important mediator of angiogenesis, tumorigenicity, and metastasis in transitional cell carcinoma (TCC) of the bladder. Nuclear factor kappaB (NF-kappaB)/relA regulates IL-8 expression in several neoplasms. The purpose of this study was to determine whether the organ microenvironment (hypoxia, acidosis) regulates the expression of IL-8 in TCC via NF-kappaB, and whether inhibition of NF-kappaB function by mutant IkappaB-alpha prevents induction of IL-8 expression.


METHODS
IL-8 mRNA expression and protein production by human TCC cell lines (UM-UC-14, HTB-9, RT-4, KU-7 and 253J B-V) were measured by Northern blot analysis and ELISA under acidic (pH 7.35-6.0) and hypoxic (1.0% O(2)) conditions. The involvement of NF-kappaB and activator protein 1 in the regulation of IL-8 production was evaluated by electrophoretic mobility shift assay. Furthermore, the tumorigenicity and metastatic potential of UM-UC-14 cells were determined after transfection with mutant IkappaB-alpha.


RESULTS
We found that acidic and hypoxic conditions increased IL-8 mRNA expression and protein production by several, but not all, TCC cell lines evaluated. NF-kappaB, but not activator protein 1, was inducibly activated in UM-UC-14 under both acidic and hypoxic conditions, but not in UM-UC-14 mutant IkappaB-alpha transfectants. Tumor growth and lymph node metastasis were inhibited in UM-UC-14 mutant IkappaB-alpha transfectants compared with UM-UC-14 controls. This effect was associated with the inhibition of IL-8 production, cellular proliferation, and angiogenesis.


CONCLUSIONS
These results suggest that TCCs of the bladder have heterogenic responses to physicochemical changes in the microenvironment and identify NF-kappaB as a potential molecular target for therapy.
Karashima
Takashi
T
Departments of Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Sweeney
Paul
P
Kamat
Ashish
A
Huang
Suyun
S
Kim
Sun J
SJ
Bar-Eli
Menashe
M
McConkey
David J
DJ
Dinney
Colin P N
CP
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002455:Cell Division; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D053938:DNA Fragmentation; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D016209:Interleukin-8 / Q000378:metabolism*; D008207:Lymphatic Metastasis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009154:Mutation; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000502:physiology*; D009362:Neoplasm Metastasis; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation; D001749:Urinary Bladder Neoplasms / Q000378:metabolism*
D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D012333:RNA, Messenger; D000072000:NF-KappaB Inhibitor alpha