TGF-beta downregulates PTEN via activation of NF-kappaB in pancreatic cancer cells.
TGF-beta utilizes receptor-activated SMAD signaling to mediate growth suppression; however, non-SMAD signaling that modulates the TGF-beta response in epithelial cells become apparent when the SMAD signaling is abrogated, a common occurrence in pancreatic cancers. Here, we examined whether TGF-beta utilized NF-kappaB to downregulate PTEN, a gene that is rarely mutated in pancreatic cancers. SMAD4-null BxPc3 and CAPAN-1 pancreatic cancer cells were treated with TGF-beta (10 ng/ml) and lysed, and cellular proteins were analyzed by Western blots using p-IkappaB, p65, and PTEN antibodies. PTEN promoter and NF-kappaB activities were assessed by PTEN-luc and p-NF-luc constructs, respectively. Dominant negative p-IkappaB-alpha-M (NF-kappaB superrepressor) was used to block activation of NF-kappaB. Cell motility was assessed by Boyden chamber migration assay. TGF-beta induced IkappaB-alpha phosphorylation followed by NF-kappaB p65 subunit nuclear translocation and increased NF-kappaB activity. IkappaB-alpha-M blocked TGF-beta-induced NF-kappaB activity, reversed downregulated PTEN promoter activity and PTEN expression, and prevented augmentation of cell motility induced by TGF-beta. SMAD4 restoration, but not knockdown of SMAD2 and/or 3, reversed TGF-beta-induced NF-kappaB activity. Thus TGF-beta suppresses PTEN in pancreatic cancer cells through NF-kappaB activation and enhances cell motility and invasiveness in a SMAD4-independent manner that can be counteracted when TGF-beta-SMAD signaling is restored. The TGF-beta/NF-kappaB/PTEN cascade may be a critical pathway for pancreatic cancer cells to proliferate and metastasize.
Chow
Jimmy Y C
JY
Division of Gastroenterology, Department of Medicine, University of California-San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093-0063, USA. ycchow@ucsd.edu
Ban
Makiko
M
Wu
Helen L
HL
Nguyen
Flang
F
Huang
Mei
M
Chung
Heekyung
H
Dong
Hui
H
Carethers
John M
JM
D000230:Adenocarcinoma / Q000473:pathology* / Q000503:physiopathology; D021441:Carcinoma, Pancreatic Ductal / Q000473:pathology* / Q000503:physiopathology; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000502:physiology; D017930:Genes, Reporter / Q000502:physiology; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D051901:Smad4 Protein / Q000378:metabolism; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology
D020672:I-kappa B Proteins; C000606204:NFKBIA protein, human; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D051996:Transcription Factor RelA; D016212:Transforming Growth Factor beta; D000072000:NF-KappaB Inhibitor alpha; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human