Essential requirement for β-arrestin2 in mouse intestinal tumors with elevated Wnt signaling.
β-Arrestins (Arrb) participate in the regulation of multiple signaling pathways, including Wnt/β-catenin, the major actor in human colorectal cancer initiation. To better understand the roles of Arrb in intestinal tumorigenesis, a reverse genetic approach (Arrb(-/-)) and in vivo siRNA treatment were used in Apc(Δ14/+) mice. Mice with Arrb2 depletion (knockout and siRNA) developed only 33% of the tumors detected in their Arrb2-WT littermates, whereas Arrb1 depletion remained without significant effect. These remaining tumors grow normally and are essentially Arrb2-independent. Unsupervised hierarchical clustering analysis showed that they clustered with 25% of Apc(Δ14/+);Arrb2(+/+) tumors. Genes overexpressed in this subset reflect a high interaction with the immune system, whereas those overexpressed in Arrb2-dependent tumors are predominantly involved in Wnt signaling, cell adhesion, migration, and extracellular matrix remodeling. The involvement of Arrb2 in intestinal tumor development via the regulation of the Wnt pathway is supported by ex vivo and in vitro experiments using either tumors from Apc(Δ14/+) mice or murine Apc(Min/+) cells. Indeed, Arrb2 siRNAs decreased the expression of Wnt target genes in cells isolated from 12 of 18 tumors from Apc(Δ14/+) mice. In Apc(Min/+) cells, Arrb2 siRNAs completely reversed the increased Wnt activity and colony formation in soft agar induced by Apc siRNA treatment, whereas they did not affect these parameters in basal conditions or in cells expressing constitutively active β-catenin. We demonstrate that Arrb2 is essential for the initiation and growth of intestinal tumors displaying elevated Wnt pathway activity and identify a previously unsuspected molecular heterogeneity among tumors induced by truncating Apc mutations.
Centre National de la Recherche Scientifique Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, F-34000 Montpellier, France.
Caroline
C
Bonnans
Maud
M
Flacelière
Fanny
F
Grillet
Christelle
C
Dantec
Jean-Pierre
JP
Desvignes
Julie
J
Pannequin
Dany
D
Severac
Emeric
E
Dubois
Frédéric
F
Bibeau
Virginie
V
Escriou
Philippe
P
Crespy
Laurent
L
Journot
Frédéric
F
Hollande
Dominique
D
Joubert
D025601:Adenomatous Polyposis Coli Protein / Q000378:metabolism; D000818:Animals; D019390:Arrestins / Q000378:metabolism*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D049109:Cell Proliferation; D002469:Cell Separation; D002471:Cell Transformation, Neoplastic / Q000473:pathology; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D007414:Intestinal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D000073940:Transcription Factor 4; D014410:Tumor Stem Cell Assay; D060449:Wnt Signaling Pathway; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605253:ARRB1 protein, human; C000605254:ARRB2 protein, human; D025601:Adenomatous Polyposis Coli Protein; C000605255:Arrb1 protein, mouse; C000605258:Arrb2 protein, mouse; D019390:Arrestins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C090743:Tcf4 protein, mouse; D000073940:Transcription Factor 4; D000071559:beta-Arrestin 1; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins