Overexpression of Members of the AP-1 Transcriptional Factor Family from an Early Stage of Renal Carcinogenesis and Inhibition of Cell Growth by AP-1 Gene Antisense Oligonucleotides in theTsc2Gene Mutant (Eker) Rat Model

Abstract

We previously isolated subtracted cDNA clones for genes having increased expression inTsc2gene mutant (Eker) rat renal carcinomas (RCs). Among them,fra-1encoding a transcriptional factor activator protein 1 (AP-1) was identified. We have therefore investigated whether other members of the AP-1 transcription factor family might also be involved in renal carcinogenesis in the Eker rat model. In the present study, overexpression offra-1, fra-2, c-jun, junB,andjunDmRNAs was demonstrated in RCs by Northern blot analysis. Interestingly, AP-1 proteins were highly expressed even in the earliest preneoplastic lesions (e.g., phenotypically altered tubules) as suggested by immunohistochemistry. Moreover, 12-O-tetradecanoylphorbol-13-acetate-responsive element (TRE)-binding activity of AP-1 proteins was observed in RC cell extracts by electrophoretic mobility shift assay. As a next step, we transfected antisense oligonucleotides targeting AP-1 genes into RC cells and demonstrated that their growth was strongly inhibited. Thus, the data suggest that overexpression of AP-1 genes might play a crucial role in renal carcinogenesis in the Eker rat model.