Negative regulation of NF-κB by the ING4 tumor suppressor in breast cancer.
Nuclear Factor kappa B (NF-κB) is a key mediator of normal immune response but contributes to aggressive cancer cell phenotypes when aberrantly activated. Here we present evidence that the Inhibitor of Growth 4 (ING4) tumor suppressor negatively regulates NF-κB in breast cancer. We surveyed primary breast tumor samples for ING4 protein expression using tissue microarrays and a newly generated antibody. We found that 34% of tumors expressed undetectable to low levels of the ING4 protein (n = 227). Tumors with low ING4 expression were frequently large in size, high grade, and lymph node positive, suggesting that down-regulation of ING4 may contribute to breast cancer progression. In the same tumor set, we found that low ING4 expression correlated with high levels of nuclear phosphorylated p65/RelA (p-p65), an activated form of NF-κB (p = 0.018). Fifty seven percent of ING4-low/p-p65-high tumors were lymph node-positive, indicating a high metastatic tendency of these tumors. Conversely, ectopic expression of ING4 inhibited p65/RelA phosphorylation in T47D and MCF7 breast cancer cells. In addition, ING4 suppressed PMA-induced cell invasion and NF-κB-target gene expression in T47D cells, indicating that ING4 inhibited NF-κB activity in breast cancer cells. Supportive of the ING4 function in the regulation of NF-κB-target gene expression, we found that ING4 expression levels inversely correlated with the expression of NF-κB-target genes in primary breast tumors by analyzing public gene expression datasets. Moreover, low ING4 expression or high expression of the gene signature composed of a subset of ING4-repressed NF-κB-target genes was associated with reduced disease-free survival in breast cancer patients. Taken together, we conclude that ING4 negatively regulates NF-κB in breast cancer. Consequently, down-regulation of ING4 leads to activation of NF-κB, contributing to tumor progression and reduced disease-free patient survival in breast cancer.
Cancer and Cell Biology Division, Translational Genomics Research Institute, Phoenix, Arizona, United States of America.
Sara A
SA
Byron
Elizabeth
E
Min
Tanya S
TS
Thal
Galen
G
Hostetter
Aprill T
AT
Watanabe
David O
DO
Azorsa
Tanya H
TH
Little
Coya
C
Tapia
Suwon
S
Kim
D000911:Antibodies, Monoclonal / Q000276:immunology; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018797:Cell Cycle Proteins / Q000276:immunology / Q000378:metabolism*; D045744:Cell Line, Tumor; D018450:Disease Progression; D018572:Disease-Free Survival; D015536:Down-Regulation / Q000187:drug effects; D018398:Homeodomain Proteins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D009361:Neoplasm Invasiveness; D010766:Phosphorylation / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D025521:Tumor Suppressor Proteins / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D018797:Cell Cycle Proteins; D018398:Homeodomain Proteins; C483230:ING4 protein, human; C498143:RELA protein, human; D051996:Transcription Factor RelA; D025521:Tumor Suppressor Proteins; D013755:Tetradecanoylphorbol Acetate