Endogenous AP-1 Levels Necessary for Oncogenic Activity Are Higher Than Those Sufficient to Support Normal Growth

• Published in: Biochemical and biophysical research communications 2000-11, Vol.278 (1), p.97-105
• Main Authors: Ui, Motoyasu, Mizutani, Taketoshi, Takada, Mizuho, Arai, Tohru, Ito, Taiji, Murakami, Masao, Koike, Chika, Watanabe, Tatsuo, Yoshimatsu, Kentaro, Iba, Hideo
• Format: Article
• Language: English
• Subjects: 3T3 Cells; anchorage-independent growth; Animals; AP-1; Blotting, Western; Cadherins - biosynthesis; Cell Division; cervical carcinomas; DNA - metabolism; dominant-negative mutants; Dose-Response Relationship, Drug; E-cadherin; Electrophoresis, Polyacrylamide Gel; Fra-1 protein; Genes, Dominant; human tumor cell lines; Humans; Hyaluronan Receptors - biosynthesis; Membrane Glycoproteins; Mice; Neoplasms - metabolism; non-small cell lung carcinomas; osteosarcomas; p53; Plasmids - metabolism; Proto-Oncogene Proteins c-fos - biosynthesis; Proto-Oncogene Proteins c-jun - biosynthesis; Retroviridae - genetics; SupJunD gene; Time Factors; Transcription Factor AP-1 - genetics; Transcription Factor AP-1 - metabolism; Transcription Factor AP-1 - physiology; Transfection; Tumor Cells, Cultured; Tumor Suppressor Protein p53 - biosynthesis; Viral Envelope Proteins - metabolism; VSV-G pseudotyped retrovirus
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.2000.3777

We investigated the role of endogenous AP-1 in human tumor cell lines by introducing SupJunD-1, a dominant-negative mutant of AP-1, using vesicular stomatitis virus G protein (VSV-G)-pseudotyped retrovirus vectors. Single inoculation of six human tumor cell lines, originating from osteosarcomas, non-small cell lung carcinomas or cervical carcinomas, with recombinant SupJunD-1 virus at a high multiplicity of infection readily inhibited colony formation in soft agar. We detected no significant changes in expression levels of AP-1 components c-Jun or Fra-1, adhesion molecules CD44 or E-cadherin, or cell cycle regulator p53, which are encoded by genes previously reported to be under the control of AP-1 in some mouse or human cell lines. By varying the dosage of VSV-G-pseudotyped retrovirus, we were able to change the proviral copy number of supjunD-1 from 1 to approximately 10 and monitor suppression of endogenous AP-1 function as assessed by growth characteristics of the tumor cell lines, we found a SupJunD-1 dosage which significantly suppressed anchorage-independent growth without affecting the cellular growth in monolayer cultures at all. We conclude that endogenous AP-1 levels necessary for oncogenic activity are much higher than those sufficient to support normal growth.