NF-kappaB is constitutively activated in high-grade squamous intraepithelial lesions and squamous cell carcinomas of the human uterine cervix.
We demonstrate, for the first time, that the transcription factor NF-kappaB is constitutively activated during human cervical cancer progression. Immunohistochemical analysis was done using 106 paraffin-embedded cervical tissue specimens of different histological grades. In normal cervical tissue and low-grade squamous intraepithelial lesions, p50, RelA and IkappaB-alpha were mainly localized in the cytosol, whereas in high-grade lesions and squamous cell carcinomas, p50-RelA heterodimers translocated into the nucleus with a concurrent decrease in IkappaB-alpha protein. By Western blot analysis, p50 and RelA were detectable mainly in the cytosolic and nuclear extracts in normal and cancer tissues, respectively, and cytosolic IkappaB-alpha expression was detectable in normal but not in cancer cervical tissues. NF-kappaB DNA-binding activity increased during cervical cancer progression and the binding complex was mainly composed of the p50-RelA heterodimers as revealed by electrophoretic mobility shift assays. Semiquantitative RT-PCR analysis, however, showed increased levels of IkappaB-alpha mRNA in cancer samples presumably because of feedback regulation as a result of enhanced NF-kappaB DNA-binding activity and a consequent functional activation of NF-kappaB. Further immunohistochemical analysis with an antibody to phospho IkappaB-alpha revealed that phosphorylation occurs mainly in squamous intraepithelial lesions, suggesting that the IkappaB-alpha gets phosphorylated initially and degraded as the tumor progressed.
Nair
Asha
A
Division of Cancer Biology, Rajiv Gandhi Center for Biotechnology, Thiruvananthapuran, Kerala, India.
Venkatraman
Manickam
M
Maliekal
Tessy T
TT
Nair
Balaraman
B
Karunagaran
Devarajan
D
D001483:Base Sequence; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D017931:DNA Primers; D018450:Disease Progression; D005260:Female; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics; D007150:Immunohistochemistry; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D002583:Uterine Cervical Neoplasms / Q000378:metabolism*; D002578:Uterine Cervical Dysplasia / Q000378:metabolism*
D017931:DNA Primers; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha