Increased cell migration and plasticity in Nrf2-deficient cancer cell lines.
Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression is deregulated in many cancers. Genetic and biochemical approaches coupled with functional assays in cultured cells were used to explore the consequences of Nrf2 repression. Nrf2 suppression by Keap1-directed ubiquitylation or the expression of independent short hairpin RNA (shRNA)/siRNA sequences enhanced cellular levels of reactive oxygen species, Smad-dependent tumor cell motility and growth in soft agar. Loss of Nrf2 was accompanied by concomitant Smad linker region/C-terminus phosphorylation, induction of the E-cadherin transcriptional repressor Slug and suppression of the cell-cell adhesion protein E-cadherin. Ectopic expression of the wildtype but not dominant-negative Nrf2 suppressed the activity of a synthetic transforming growth factor-beta1-responsive CAGA-directed luciferase reporter. shRNA knock-down of Nrf2 enhanced the activity of the synthetic CAGA reporter, as well as the expression of the endogenous Smad target gene plasminogen activator inhibitor-1. Finally, we found that Nrf2/Smad3/Smad4 formed an immunoprecipitable nuclear complex. Thus, loss of Nrf2 increased R-Smad phosphorylation and R-Smad signaling, supporting the hypothesis that loss of Nrf2 in an oncogenic context-dependent manner can enhance cellular plasticity and motility, in part by using transforming growth factor-beta/Smad signaling.
Rachakonda
G
G
Department of Radiation Oncology, Nashville, TN, USA.
Sekhar
K R
KR
Jowhar
D
D
Samson
P C
PC
Wikswo
J P
JP
Beauchamp
R D
RD
Datta
P K
PK
Freeman
M L
ML
D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D006801:Humans; D055029:Inverted Repeat Sequences; D051267:NF-E2-Related Factor 2 / Q000172:deficiency* / Q000235:genetics* / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology*; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D051785:Smad Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D018631:ras Proteins / Q000378:metabolism
D051267:NF-E2-Related Factor 2; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D051785:Smad Proteins; D018631:ras Proteins