Overexpression of JunB in undifferentiated malignant rat oral keratinocytes enhances the malignant phenotype in vitro without altering cellular differentiation.
Our study examined the expression of AP-1 family members in keratinocytes derived from the rat-4NQO model of oral carcinogenesis in which extremes of epithelial differentiation and tumour cell aggressiveness are evident. The constitutive expression of JunB was diminished in the undifferentiated, more aggressive tumour phenotype compared with the well-differentiated, less aggressive keratinocytes, whereas the expression of other AP-1 family members (c-jun, junD, c-fos, fra1, fra2 and fosB) was either very weak or variable. After transfection of the undifferentiated keratinocytes with junB cDNA, clonal populations were isolated that expressed similar levels of JunB protein as the well-differentiated cells. Both untransfected and transfected cell lines were keratin negative and vimentin positive. Increased expression of JunB in the transfected cells resulted in up-regulation of c-Jun and Fra1 and an enhanced AP-1 activity as demonstrated by transcriptional activation of the prototypic AP-1 dependent promoter, MMP-1. JunB transfected cells grew more quickly than vector-only controls and were refractory to the growth inhibitory effects of TGF-beta1. Over-expression of JunB resulted in the elevated expression of the AP-1 dependent proteinase, MMP-9, whereas the expression of the AP-1 independent enzyme, MMP-2, was unaffected. JunB transfected keratinocytes were highly invasive in an in vitro assay of tumour cell invasion compared with vector controls. The results indicate that increased expression of JunB above baseline levels in undifferentiated rat keratinocytes does not alter epithelial differentiation but enhances the malignant phenotype in vitro, possibly by altering the dynamics of the AP-1 complex.
Department of Oral and Dental Science, University of Bristol, Bristol, United Kingdom. max.robinson@bristol.ac.uk
C M
CM
Robinson
S S
SS
Prime
S
S
Huntley
A M
AM
Stone
M
M
Davies
J W
JW
Eveson
I C
IC
Paterson
D016475:3T3 Cells; D015112:4-Nitroquinoline-1-oxide; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis; D015152:Blotting, Northern; D015153:Blotting, Western; D002273:Carcinogens; D002454:Cell Differentiation; D002455:Cell Division; D002465:Cell Movement; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D051921:Fos-Related Antigen-2; D017930:Genes, Reporter; D005822:Genetic Vectors; D015603:Keratinocytes / Q000378:metabolism*; D007633:Keratins / Q000096:biosynthesis; D008156:Luciferases / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D051379:Mice; D009062:Mouth Neoplasms / Q000378:metabolism*; D009374:Neoplasms, Experimental / Q000139:chemically induced; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis*; D051381:Rats; D013997:Time Factors; D018808:Transcription Factor AP-1 / Q000096:biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism; D053773:Transforming Growth Factor beta1; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014746:Vimentin / Q000096:biosynthesis; D000099169:Fos-Related Antigen 1
D015112:4-Nitroquinoline-1-oxide; D001426:Bacterial Proteins; D002273:Carcinogens; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D051921:Fos-Related Antigen-2; D007633:Keratins; D008156:Luciferases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014746:Vimentin; D000099169:Fos-Related Antigen 1; C483819:Fosb protein, mouse; C483820:Fosb protein, rat; C497873:Fosl2 protein, mouse; C497874:Fosl2 protein, rat; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat