Tumor suppressor Pdcd4 inhibits invasion/intravasation and regulates urokinase receptor (u-PAR) gene expression via Sp-transcription factors.
Tumor suppressor Pdcd4 has recently been shown to inhibit invasion by activating activator protein-1 (AP-1); however, little is known of the functionally significant Pdcd4-target genes. The urokinase receptor (u-PAR) promotes invasion/metastasis, and is associated with poor cancer-patient survival. The present study was conducted (1) to investigate a role for Pdcd4 in intravasation, invasion and u-PAR regulation, and (2) to describe mechanisms by which this is achieved. Fourteen cell lines showed reciprocal expression of u-PAR/Pdcd4. Resected tumor/normal tissues of 29 colorectal cancer patients demonstrated a significant inverse correlation between Pdcd4/u-PAR. siRNA-Pdcd4-transfected GEO cells significantly increased endogenous u-PAR mRNA/protein. A u-PAR-promoter-chloramphenicol acetyl transferase (CAT)-reporter was reduced in activity with increasing Pdcd4 expression in RKO. Deletion of a putative Sp-1-binding site (-402/-350) inhibited u-PAR promoter regulation by Pdcd4, this being paralleled by a reduction of Sp1 binding to this region in pdcd4-transfected cells. Pdcd4-transfected cells showed an increase in Sp3 binding to u-PAR promoter region -152/-135, the deletion of which reduces the ability of Pdcd4 to suppress u-PAR promoter activity. Surprisingly, the u-PAR-AP-1 site was not targeted by Pdcd4. Finally, RKO cells overexpressing Pdcd4 showed an inhibition of invasion/intravasation (chicken embryo metastasis assay). These data suggest Pdcd4 as a new negative regulator of intravasation, and qas the invasion-related gene u-PAR. It is the first study to implicate Pdcd4 regulation of gene expression via Sp1/Sp3.
Leupold
J H
JH
The Department of Experimental Surgery and Molecular Oncology of Solid Tumors, Medical Faculty Mannheim, University Heidelberg and DKFZ Heidelberg, Germany.
Yang
H-S
HS
Colburn
N H
NH
Asangani
I
I
Post
S
S
Allgayer
H
H
D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology*; D001665:Binding Sites; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics / Q000473:pathology; D018450:Disease Progression; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009361:Neoplasm Invasiveness / Q000235:genetics*; D009362:Neoplasm Metastasis; D016601:RNA-Binding Proteins / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000235:genetics*; D055293:Receptors, Urokinase Plasminogen Activator; D051703:Sp Transcription Factors / Q000494:pharmacology*; D016329:Sp1 Transcription Factor / Q000494:pharmacology; D051705:Sp3 Transcription Factor / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; C114487:PDCD4 protein, human; C524898:PLAUR protein, human; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; C497121:SP3 protein, human; D051703:Sp Transcription Factors; D016329:Sp1 Transcription Factor; D025521:Tumor Suppressor Proteins; D051705:Sp3 Transcription Factor