EphA2 up-regulation induced by deoxycholic acid in human colon carcinoma cells, an involvement of extracellular signal-regulated kinase and p53-independence.
OBJECTIVE
The EphA2 receptor protein tyrosine kinase gene has been shown to be over-expressed or functionally altered in a number of human tumors, including colon cancer, but little is known about the regulation of this new oncoprotein. In order to explore the mechanism of EphA2 up-regulation in cancer cells, we examined the change of expression of EphA2 gene induced by deoxycholic acid (DCA) and elucidated its possible pathways in human colon cancer cells.


METHODS
Western blot and RT-PCR were used to assess the protein expression and messenger RNA in several colon cancer cell lines, which harbor various p53 status. The inhibition study to interfere the MAPK pathway was performed by using various chemicals and by transfecting dominant negative mutant plasmids.


RESULTS
Up-regulation of EphA2 induced by DCA was observed in a dose- and time-dependent fashion both in mRNA and protein levels. This regulation is constant regardless of p53 status including wild, mutant or knocked out in the colon cell lines used. This induction was in part blocked by either erk1/2 inhibitors or dominant negative mutants erk1/2 plasmids.


CONCLUSIONS
These results suggest that DCA induced up-regulation of EphA2 in colon cancer cells is due to activation of erk1/2 cascade, and is p53-independent. Taken together with the roles of EphA2 and DCA in tumorigenesis, which have been independently reported, our observation will provide a new mechanistic basis of DCA commitment in carcinogenesis.
Li
Zhongyou
Z
The First Department of Pathology, Hamamatsu University School of Medicine, 1-20-1 Handayama, 431-3192 Hamamatsu, Japan.
Tanaka
Masamitsu
M
Kataoka
Hideki
H
Nakamura
Ritsuko
R
Sanjar
Ravshanov
R
Shinmura
Kazuya
K
Sugimura
Haruhiko
H
D015153:Blotting, Western; D002277:Carcinoma / Q000378:metabolism*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D036104:Receptor, EphA2 / Q000187:drug effects* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D016159:Tumor Suppressor Protein p53; D003840:Deoxycholic Acid; D036104:Receptor, EphA2; D020928:Mitogen-Activated Protein Kinases