Down-regulation of NF-kappaB activity and NF-kappaB p65 subunit expression by ras and polyoma middle T oncogenes in human colonic Caco-2 cells.
The products of ras and src proto-oncogenes are frequently activated in a constitutive state in human colorectal cancer. In this study we attempted to establish whether the tumorigenic progression induced by oncogenic activation of p21ras or pp60c-src in human colonic cells is associated with alterations of the activity and expression of nuclear factor kappaB (NF-kappaB), a transcription factor suspected to participate in the development of cancer. To this end, we used Caco-2 cells made highly tumorigenic by transfection with an activated Val-12 human Ha-ras gene or with the polyoma middle T (PyMT) oncogene, a constitutive activator of pp60c-src tyrosine kinase activity. Compared with control vector-transfected Caco-2 cells, both oncogene-transfected cell lines exhibited: (i) decreased constitutive NF-kappaB DNA-binding activity and NF-kappaB-mediated reporter gene expression, without alteration of their response to TNF-alpha for activation of these parameters; (ii) reduced NF-kappaB cytosolic stores along with a decreased p65 expression due, at least in part, to destabilization of p65 mRNA; (iii) a decrease in adhesion to extracellular matrix component-coated substrata which was partially corrected when stimulating NF-kappaB transcriptional activity with TNF-alpha. These results indicate that the tumorigenic progression induced by oncogenic p21ras or PyMT/pp60c-src in human colonic Caco-2 cells is associated with a down-regulation of p65 expression and NF-kappaB activity which could be responsible for the reduced adhesive properties of these cells after oncogene transfection.
Cadoret
A
A
INSERM U 402, Laboratoire de Biologie Cellulaire, Faculté de MédecineSaint-Antoine, Paris, France.
Bertrand
F
F
Baron-Delage
S
S
Lévy
P
P
Courtois
G
G
Gespach
C
C
Capeau
J
J
Cherqui
G
G
D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D018938:Caco-2 Cells; D002448:Cell Adhesion; D003600:Cytosol / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D011905:Genes, ras; D006801:Humans; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism*; D009857:Oncogenes; D011493:Protein Kinase C / Q000378:metabolism; D051996:Transcription Factor RelA; D014158:Transcription, Genetic; D014162:Transfection
D000952:Antigens, Polyomavirus Transforming; D004273:DNA, Neoplasm; D016328:NF-kappa B; D051996:Transcription Factor RelA; D011493:Protein Kinase C