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Updated: Apr 22, 2026
Modeling Paracrine Noncanonical Wnt Signaling In Vitro
Published on: December 10, 2021
Tripartite interactions between Wnt signaling, Notch and Myb for stem/progenitor cell functions during intestinal
Markus Germann1, Huiling Xu2, Jordane Malaterre3
1Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
Abstract:
Deletion studies confirm Wnt, Notch and Myb transcriptional pathway engagement in intestinal tumorigenesis. Nevertheless, their contrasting and combined roles when activated have not been elucidated. This is important as these pathways are not ablated but rather are aberrantly activated during carcinogenesis. Using ApcMin/+ mice as a source of organoids we documented their transition, on a clone-by-clone basis, to cyst-like spheres with constitutively activated Wnt pathway, increased self-renewal and growth and reduced differentiation. We then looked at this transition when Myb and/or Notch1 are activated. Activated Notch promoted cyst-like organoids. Conversely growth and propagation of cyst-like, but not normal organoids were Notch-independent. Activated Myb promoted normal, but not cyst-like organoids. Interestingly the Wnt, Notch and Myb pathways were all involved in regulating the expression of the intestinal stem cell (ISC) gene Lgr5 in organoids, while ISC gene and Notch target Olfm4 was dominantly repressed by Wnt. These findings parallel mouse intestinal adenoma formation where Notch promoted the initiation, but not growth, of Wnt-driven Olfm4-repressed colon tumors. Also Myb was essential for colon tumor initiation and collateral mouse pathologies. These data reveal the complex interplay and hierarchy of transcriptional networks that operate in ISCs and uncover a shift in pathway-dependencies during tumor initiation.
Insights
Investigating Wnt, Notch, and Myb pathways in intestinal cancer reveals complex interactions. These pathways shift dependencies during tumor initiation, impacting stem cell gene regulation and tumor growth.
Area of Science:
- Molecular biology
- Cancer research
- Genetics
Background:
- Wnt, Notch, and Myb transcriptional pathways are implicated in intestinal tumorigenesis.
- Their specific roles and interactions during aberrant activation in carcinogenesis are not fully understood.
Purpose of the Study:
- To elucidate the contrasting and combined roles of activated Wnt, Notch, and Myb pathways in intestinal organoid transformation and tumorigenesis.
- To investigate the regulatory network of intestinal stem cell (ISC) genes, including Lgr5 and Olfm4, under the influence of these pathways.
Main Methods:
- Utilized ApcMin/+ mouse organoids to study clonal transitions to cyst-like spheres.
- Activated Wnt, Notch1, and Myb pathways individually and in combination.
- Analyzed the expression of ISC genes Lgr5 and Olfm4.
Main Results:
- Constitutively activated Wnt promoted self-renewal and growth while reducing differentiation in organoids.
- Activated Notch promoted cyst-like organoids, but their growth was Notch-independent.
- Activated Myb promoted normal organoids but not cyst-like ones.
- Wnt, Notch, and Myb pathways regulate Lgr5 expression; Wnt dominantly represses Olfm4.
- Notch promoted tumor initiation, while Myb was essential for initiation and associated pathologies in mice.
Conclusions:
- The study reveals a complex interplay and hierarchy among Wnt, Notch, and Myb pathways in intestinal stem cells.
- A shift in pathway dependencies occurs during tumor initiation, impacting stem cell behavior and gene expression.
- Findings provide insights into the molecular mechanisms driving intestinal adenoma formation.
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