Involvement of deregulated epiregulin expression in tumorigenesis in vivo through activated Ki-Ras signaling pathway in human colon cancer cells.
To identify the genes located downstream of the activated Ki-Ras signaling pathways in human colon cancer cells, a PCR-based cDNA subtraction library was constructed between HCT116 cells and HCT116-derived activated Ki-ras-disrupted cells (HKe3). One of the genes in HCT116 that was evidently up-regulated was epiregulin, a member of the epidermal growth factor family that is expressed in many kinds of human cancer cells. HKe3-stable transfectants expressing activated Ki-Ras regained over-expression of epiregulin. To further elucidate the biochemical structure and significance of epiregulin expression in tumorigenesis, HKe3-stable transfectants expressing epiregulin (e3-pSE cells) were established. Epiregulin existed as highly glycosylated membrane-bound forms, and TPA rapidly induced ectodomain shedding of epiregulin. Furthermore, the conditioned medium of e3-pSE cells showed more DNA synthesis for 32D cells expressing epidermal growth factor receptor (DER) cells than that of HKe3. Although anchorage-independent growth in soft agar was not observed for e3-pSE cells, tumorigenicity in nude mice was observed evidently, and their growth rate was correlated with each amount of exogenous epiregulin expression. These results suggested that activated Ki-Ras will be one of the factors contributing to the overexpression of epiregulin in human colon cancer cells, and that epiregulin will play a critical role in human tumorigenesis in vivo.
Baba
I
I
Department of Genetics, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
Shirasawa
S
S
Iwamoto
R
R
Okumura
K
K
Tsunoda
T
T
Nishioka
M
M
Fukuyama
K
K
Yamamoto
K
K
Mekada
E
E
Sasazuki
T
T
D000818:Animals; D019921:Biotinylation; D015152:Blotting, Northern; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066260:Epiregulin; D015723:Gene Library; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008024:Ligands; D051379:Mice; D008819:Mice, Nude; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D017077:Culture Media, Conditioned; D018076:DNA, Complementary; C587880:EREG protein, human; D066260:Epiregulin; C587881:Ereg protein, mouse; D008024:Ligands; D004815:Epidermal Growth Factor; D004247:DNA; D015689:Oncogene Protein p21(ras); D013755:Tetradecanoylphorbol Acetate