Nuclear factor-kappaB signature of inflammatory breast cancer by cDNA microarray validated by quantitative real-time reverse transcription-PCR, immunohistochemistry, and nuclear factor-kappaB DNA-binding.
OBJECTIVE
Inflammatory breast cancer (IBC) is the most aggressive form of locally advanced breast cancer with high metastatic potential. In a previous study, we showed that IBC is a different form of breast cancer compared with non-IBC by cDNA microarray analysis. A list of 756 genes with significant expression differences between IBC and non-IBC was identified. In-depth functional analysis revealed the presence of a high number of nuclear factor-kappaB (NF-kappaB) target genes with elevated expression in IBC versus non-IBC. This led to the hypothesis that NF-kappaB contributes to the phenotype of IBC. The aim of the present study was to further investigate the role of NF-kappaB in IBC.


METHODS
Immunohistochemistry and NF-kappaB DNA-binding experiments were done for all NF-kappaB subunits (RelA, RelB, cRel, NFkB1, and NFkB2) using IBC and non-IBC specimens. Transcriptionally active NF-kappaB dimers were identified by means of coexpression analysis. In addition, quantitative real-time reverse transcription-PCR for eight NF-kappaB target genes, selected upon a significant, 3-fold gene expression difference between IBC and non-IBC by cDNA microarray analysis, was done.


RESULTS
We found a significant overexpression for all of eight selected NF-kappaB target genes in IBC compared with non-IBC by quantitative real-time reverse transcription-PCR. In addition, we found a statistically elevated number of immunostained nuclei in IBC compared with non-IBC for RelB (P = 0.038) and NFkB1 (P < 0.001). Immunohistochemical data were further validated by NF-kappaB DNA-binding experiments. Significant correlations between immunohistochemical data and NF-kappaB DNA binding for RelA, RelB, NFkB1, and NFkB2 were found. Transcriptionally active NF-kappaB dimers, composed of specific combinations of NF-kappaB family members, were found in 19 of 44 IBC specimens compared with 2 of 45 non-IBC specimens (P < 0.001). In addition, we found evidence for an estrogen receptor (ER)-mediated inhibition of the NF-kappaB signaling pathway. NF-kappaB target genes were significantly elevated in ER- versus ER+ breast tumors. Also, the amount of immunostained nuclei for RelB (P = 0.025) and NFkB1 (P = 0.031) was higher in ER- breast tumors versus ER+ breast tumors.


CONCLUSIONS
The NF-kappaB transcription factor pathway probably contributes to the phenotype of IBC and possibly offers new options for treatment of patients diagnosed with this aggressive form of breast cancer.
Van Laere
Steven J
SJ
Translational Cancer Research Group (Laboratory of Pathology, University of Antwerp and Oncology Center, General Hospital Sint-Augustinus), Wilrijk, Belgium.
Van der Auwera
Ilse
I
Van den Eynden
Gert G
GG
Elst
Hilde J
HJ
Weyler
Joost
J
Harris
Adrian L
AL
van Dam
Peter
P
Van Marck
Eric A
EA
Vermeulen
Peter B
PB
Dirix
Luc Y
LY
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007249:Inflammation / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000235:genetics
D016328:NF-kappa B