Src activation of Stat3 is an independent requirement from NF-kappaB activation for constitutive IL-8 expression in human pancreatic adenocarcinoma cells.
Human pancreatic tumors often overexpress the angiogenesis-promoting factor Interleukin 8 (IL-8), in part due to overexpression of NF-kappaB, a frequent occurrence in pancreatic adenocarcinoma. In this study, we demonstrate that reducing c-Src kinase activity, through either pharmacologic inhibition or small interfering RNA-targeted reduction of Src expression, significantly decreased IL-8 expression (P < 0.05) without affecting NF-kappaB-mediated transcription, but by decreasing phosphorylation of STAT3. To ascertain whether Src-mediated expression of IL-8 was dependent on STAT3, we used stable clones expressing a dominant-negative isoform of STAT3 that inhibits endogenous STAT3 phosphorylation and subsequent DNA binding and STAT3-mediated gene expression or a constitutively activated isoform of STAT3. IL-8 expression was significantly lower in clones expressing the dominant-negative isoform and significantly increased in clones expressing the activated isoform (P < 0.05 for both). Pharmacologic inhibition of NF-kappaB activity significantly reduced basal IL-8 expression and tumor necrosis factor-induced IL-8 expression (P < 0.05 for both), yet NF-kappaB activity was not dependent on Src. We therefore suggest that Src activation, through phosphorylation of STAT3, and NF-kappaB are all required for expression of IL-8 a critical angiogenic-promoting factor in pancreatic adenocarcinomas.
Trevino
Jose G
JG
Department of Cancer Biology, Unit 179, The University of Texas M D Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Gray
Michael J
MJ
Nawrocki
Steffan T
ST
Summy
Justin M
JM
Lesslie
Donald P
DP
Evans
Douglas B
DB
Sawyer
Tomi K
TK
Shakespeare
William C
WC
Watowich
Stephanie S
SS
Chiao
Paul J
PJ
McConkey
David J
DJ
Gallick
Gary E
GE
D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D017930:Genes, Reporter; D006801:Humans; D007150:Immunohistochemistry; D016209:Interleukin-8 / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*
D016209:Interleukin-8; D016328:NF-kappa B; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; D008156:Luciferases; D016392:Proto-Oncogene Proteins pp60(c-src)