Restoration of epithelial cell polarity in a colorectal cancer cell line by suppression of beta-catenin/T-cell factor 4-mediated gene transactivation.
Beta-catenin acts as a transcriptional coactivator by forming a complex with T-cell factor/lymphoid enhancer factor (TCF/LEF) DNA-binding proteins. Aberrant transactivation of a certain set of target genes by beta-catenin and TCF4 complexes has been implicated in familial and sporadic colorectal tumorigenesis. A colorectal cancer cell line, DLD-1, becomes irregularly multilayered, when maintained confluent for 2-3 weeks, and forms numerous dome-like polypoid foci piled-up over the surface of cell sheets. By the use of a strict tetracycline-regulation system, we found that the continuous suppression of beta-catenin/TCF4-mediated gene transactivation by dominant-negative TCF4B (deltaN30) reduced these piled-up foci and restored a simple monolayer of polarized columnar cells resembling normal intestinal epithelium. The restoration of epithelial cell polarity was evident in two ways: (a) the formation of microvilli over the apical surface; and (b) the distribution of a tight junction protein, ZO-1, to the lateral plasma membrane. Retroviral expression of stabilized beta-catenin (deltaN89) induced the formation of similar piled-up foci in untransformed IEC6 intestinal epithelial cells. Sulindac, a nonsteroidal antiinflammatory drug effective against colorectal tumorigenesis in familial adenomatous polyposis syndrome, suppressed the formation of foci. The loss of epithelial cell polarity may be a critical cellular event driving beta-catenin/TCF4-mediated intestinal tumorigenesis.
Naishiro
Y
Y
Pathology Division, National Cancer Center Research Institute, Tokyo, Japan.
Yamada
T
T
Takaoka
A S
AS
Hayashi
R
R
Hasegawa
F
F
Imai
K
K
Hirohashi
S
S
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000595:Amino Acid Sequence; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D003598:Cytoskeletal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004318:Doxycycline / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D019450:Genes, MDR; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D051381:Rats; D012190:Retroviridae / Q000235:genetics; D013467:Sulindac / Q000494:pharmacology; D051820:TCF Transcription Factors; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology*; D014407:Tumor Cells, Cultured; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin
D000894:Anti-Inflammatory Agents, Non-Steroidal; C495270:CTNNB1 protein, human; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C569042:TJP1 protein, human; C553059:Tcf7l2 protein, rat; C569044:Tjp1 protein, rat; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D013467:Sulindac; D004318:Doxycycline