Reduced expression of beta-catenin inhibitor Chibby in colon carcinoma cell lines.
OBJECTIVE
To analyse the Chibby expression and its function in colon carcinoma cell lines and colorectal carcinoma (CRC).


METHODS
Chibby expression levels were investigated by quantitative RT-PCR in a panel of seven different colon carcinoma cell lines. By sequencing, we analysed mutational status of Chibby. To test whether Chibby exhibited effects on beta-catenin signalling in colon carcinoma cells, we transfected SW480 cells with Chibby expression plasmid and, subsequently, analysed activity of beta-catenin and tested for alterations in cellular phenotype. In addition, we examined Chibby mRNA levels in samples of colorectal carcinomas and adjacent normal tissues by using quantitative RT-PCR and hybridised gene chips with samples from CRC and normal tissues.


RESULTS
Chibby mRNA expression was strongly down-regulated in colon carcinoma cell lines in comparison to normal colon epithelial cells and no mutation in any of the examined colon carcinoma cell lines was found. Further, we could show that Chibby inhibited beta-catenin activity in TOPflash assays when over-expressed in SW480 cells. Proliferation and invasion assays with Chibby transfected SW480 cells did not reveal profound differences compared to control cells. In contrast to these in vitro data, quantitative RT-PCR analyses of Chibby mRNA levels in CRC tumor samples did not show significant differences to specimens in adjacent non-cancerous tissue. Consistent with these findings, gene chips analysing tissue samples of tumors and corresponding normal tissue did not show altered Chibby expression.


CONCLUSIONS
Altered Chibby expression might be observed in vitro in different colon carcinoma cell lines. However, this finding could not be confirmed in vitro in CRC tumors, indicating that Chibby is not likely to promote CRC tumor development or progression. As Chibby is an important inhibitor of beta-catenin signalling, our data implicate that the usability of colon carcinoma cell lines for in vitro studies analysing the Wnt/beta-catenin pathway in colorectal carcinoma needs extensive verification.
University of Regensburg, Institute of Pathology, Franz-Josef-Straus-Allee 11, 93053 Regensburg, Germany.
Marion M
MM
Schuierer
Elisabeth
E
Graf
Ken-Ichi
K
Takemaru
Wolfgang
W
Dietmaier
Anja-Katrin
AK
Bosserhoff
D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D066298:In Vitro Techniques; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction; D014162:Transfection; D051153:Wnt Proteins; D051176:beta Catenin / Q000037:antagonists & inhibitors* / Q000502:physiology
C473750:CBY1 protein, human; D002352:Carrier Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D051153:Wnt Proteins; D051176:beta Catenin