Mutant E-cadherin breast cancer cells do not display constitutive Wnt signaling.
Participation of E-cadherin in the Wnt signaling pathway was suggested because of the dual role of beta-catenin in cell adhesion and the Wnt signaling cascade. Whereas beta-catenin interacts at the cell membrane with the cell adhesion protein E-cadherin, in the nucleus it activates Wnt target genes through formation of transcriptionally active complexes with members of the Tcf/Lef family of transcription factors. Here, we analyzed by PCR and direct cycle sequencing 26 human breast cancer cell lines for alterations in the E-cadherin gene. Genetic alterations were identified in eight cell lines. Five cell lines had truncating mutations, whereas three cell lines had in-frame deletions in the gene transcript and expressed mutant E-cadherin proteins at the cell membrane. Involvement of E-cadherin in the Wnt pathway was evaluated through determination of the activity of a Tcf reporter gene, which had been transiently transfected into 15 breast cancer cell lines. None of six E-cadherin mutant cell lines and four cell lines that exhibit transcriptional silencing of the E-cadherin gene showed Tcf-mediated transcriptional activation. E-cadherin wild-type cell line DU4475 exhibited constitutive Tcf-beta-catenin signaling activity and was found to express truncated APC proteins. These results indicate that if cellular transformation occurred through mutation of E-cadherin, it is not mediated via constitutive activation of the Wnt signaling pathway.
van de Wetering
M
M
Department of Immunology, University Medical Center Utrecht, The Netherlands.
Barker
N
N
Harkes
I C
IC
van der Heyden
M
M
Dijk
N J
NJ
Hollestelle
A
A
Klijn
J G
JG
Clevers
H
H
Schutte
M
M
D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics; D015870:Gene Expression; D020868:Gene Silencing; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics; D051821:Lymphoid Enhancer-Binding Factor 1; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics; D015533:Transcriptional Activation / Q000502:physiology; D014407:Tumor Cells, Cultured; D051153:Wnt Proteins; D029961:Zebrafish Proteins
D015820:Cadherins; D004268:DNA-Binding Proteins; D051821:Lymphoid Enhancer-Binding Factor 1; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D008156:Luciferases