APC Moonlights to Prevent Wnt Signalosome Assembly

Comparative Analysis of Commercial and Home-Made Media on RSPO1/S6R Axis in Organoids with Different Wnt Backgrounds: A Methodological Guide for the Selection of Intestinal Patient-Derived Organoids Culture Media

WNT3A is an intestinal ligand triggering the Wnt/β-catenin (Wnt) pathway, which can be enhanced by R-spondin 1 (RSPO1) through the RSPO1-LGR axis or antagonized by the adenomatous polyposis coli (APC) protein supporting β-catenin-degradation. Wnt interplays with several pathways including PI3K/mTOR (mTOR). In this study, we evaluated the influence of WNT3A-commercial and home-made culture media and RSPO1 protein on the Wnt and mTOR interplay in non-APC and APC-mutated intestinal patient-derived organoids (PDOs). Normal mucosa (NM) of sporadic CRC and FAP PDOs were cultured with: WNT3A-lacking/containing commercial (A/A+B) or home-made (BASAL/WNT3A-conditioned medium (CM)±RSPO1) media. In non-APC-mutated-PDOs (CRC-NM), WNT3A-CM, over commercial A+B, strongly activated Wnt-target-genes CCND1 and c-MYC. Most importantly, the addition of RSPO1 to home-made WNT3A-CM or A+B led to the downregulation of the mTOR-downstream-effector phospho-S6 ribosomal protein (p-S6R), highlighting the activation of the RSPO1-pS6R in both non-APC (CRC-NM) and APC-mutated (FAP-NM) PDOs, independently from LGR5 gene expression modulation. Our work demonstrates that home-made WNT3A-CM strongly impacts the crosstalk between Wnt and mTOR over commercial media, and proposes RSPO1 as a key regulator of the RSPO1-p-S6R axis in both non-APC and APC-mutated PDOs. Together, these findings represent an important methodological guide for scientists working in these fields to select the most appropriate intestinal PDO media.

APC and ZBTB2 May Mediate M2 Macrophage Infiltration to Promote the Development of Renal Fibrosis: A Bioinformatics Analysis

Background and Purpose: The continuous accumulation of M2 macrophages may potentially contribute to the development of kidney fibrosis in chronic kidney disease (CKD). The purpose of this study was to analyze the infiltration of M2 macrophages in uremic patients and to seek new strategies to slow down the progression of renal fibrosis. Methods: We conducted a comprehensive search for expression data pertaining to uremic samples within the Gene Expression Omnibus (GEO) database, encompassing the time frame from 2010 to 2022. Control and uremic differentially expressed genes (DEGs) were identified. Immune cell infiltration was investigated by CIBERSORT and modules associated with M2 macrophage infiltration were identified by weighted gene coexpression network analysis (WGCNA). Consistent genes were identified using the least absolute shrinkage and selection operator (LASSO) and selection and visualization of the most relevant features (SVM-RFE) methods to search for overlapping genes. Receiver operating characteristic (ROC) curves were examined for the diagnostic value of candidate genes. Quantitative real-time PCR (qPCR) examined the expression levels of candidate genes obtained from uremic patients in M2 macrophage. Results: A total of 1298 DEGs were identified within the GSE37171 dataset. Significant enrichment of DEGs was observed in 20 biological processes (BP), 19 cellular components (CC), 6 molecular functions (MF), and 70 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. CIBERSORT analysis observed a significant increase in B-cell memory, dendritic cell activation, M0, M1, M2, and plasma cell numbers in uremic samples. We identified the 10 most interrelated genes. In particular, adenomatous polyposis coli (APC) and zinc finger and BTB structural domain 2 (ZBTB2) were adversely associated with the infiltration of M2 macrophages. Importantly, the expression levels of APC and ZBTB2 were far lower in M2 macrophages from uremic patients than those in healthy individuals. Conclusion: The development of renal fibrosis may be the result of M2 macrophage infiltration promoted by APC and ZBTB2.

GATA4 regulates mesenchymal stem cells via direct transcriptional regulation of the WNT signalosome

GATA4 is a transcription factor that regulates osteoblast differentiation. However, GATA4 is expressed at a higher level in mesenchymal stem cells (MSCs) than in osteoblasts. Therefore, the role of GATA4 in limb bud mesenchyme differentiation was investigated in mice by knocking out Gata4 using Cre-recombinase controlled by the Prx1 promoter (herein called Gata4 Prx-cKO mice). μCT analysis of the Gata4 Prx-cKO mice showed a decrease in trabecular bone properties compared with wildtype (Gata4^fl/fl) littermates. Gata4 Prx-cKO mice have fewer MSCs as measured by CFU-F assays, mesenchymal progenitor cells (MPC2) (flow cytometry of Sca1⁺/CD45^-/CD34^-/CD44^hi) and nestin immunofluorescence. Gata4 Prx-cKO bone marrow-derived MSCs have a significant reduction in WNT ligands, including WNT10B, and WNT signalosome components compared to control cells. Chromatin immunoprecipitation demonstrates that GATA4 is recruited to enhancers near Wnt3a, Wnt10b, Fzd6 and Dkk1. GATA4 also directly represses YAP in wildtype cells, and the absence of Gata4 leads to increased YAP expression. Together, we show that the decrease in MSCs is due to loss of Gata4 and a WNT10B-dependent positive autoregulatory loop. This leads to a concurrent increase of YAP and less activated β-catenin. These results explain the decreased trabecular bone in Gata4 Prx-cKO mice. We suggest that WNT signalosome activity in MSCs requires Gata4 and Wnt10b expression for lineage specification.

Regulation of Wnt receptor activity: Implications for therapeutic development in colon cancer

Hyperactivation of Wnt/β-catenin (canonical) signaling in colorectal cancers (CRCs) was identified in the 1990s. Most CRC patients have mutations in genes that encode components of the Wnt pathway. Inactivating mutations in the adenomatous polyposis coli (APC) gene, which encodes a protein necessary for β-catenin degradation, are by far the most prevalent. Other Wnt signaling components are mutated in a smaller proportion of CRCs; these include a FZD-specific ubiquitin E3 ligase known as ring finger protein 43 that removes FZDs from the cell membrane. Our understanding of the genetic and epigenetic landscape of CRC has grown exponentially because of contributions from high-throughput sequencing projects such as The Cancer Genome Atlas. Despite this, no Wnt modulators have been successfully developed for CRC-targeted therapies. In this review, we will focus on the Wnt receptor complex, and speculate on recent discoveries about ring finger protein 43regulating Wnt receptors in CRCs. We then review the current debate on a new APC-Wnt receptor interaction model with therapeutic implications.

Are Wnt/β-Catenin and PI3K/AKT/mTORC1 Distinct Pathways in Colorectal Cancer?

Wnt/β-catenin and phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin complex 1 (PI3K/AKT/mTORC1) pathways both are critically involved in colorectal cancer (CRC) development, although they are implicated in the modulation of distinct oncogenic mechanisms. In homeostatic and pathologic conditions, these pathways show a fine regulation based mainly on feedback mechanisms, and are connected at multiple levels involving both upstream and downstream common effectors. The ability of the Wnt/β-catenin and PI3K/AKT/mTORC1 pathways to reciprocally control themselves represents one of the main resistance mechanisms to selective inhibitors in CRC, leading to the hypothesis that in specific settings, particularly in cancer driven by genetic alterations in Wnt/β-catenin signaling, the relationship between Wnt/β-catenin and PI3K/AKT/mTORC1 pathways could be so close that they should be considered as a unique therapeutic target. This review provides an update on the Wnt/β-catenin and PI3K/AKT/mTORC1 pathway interconnections in CRC, describing the main molecular players and the potential implications of combined inhibitors as an approach for CRC chemoprevention and treatment.

Wingless/Wnt Signaling in Intestinal Development, Homeostasis, Regeneration and Tumorigenesis: A Drosophila Perspective

In mammals, the Wnt/β-catenin signal transduction pathway regulates intestinal stem cell maintenance and proliferation, whereas Wnt pathway hyperactivation, resulting primarily from the inactivation of the tumor suppressor Adenomatous polyposis coli (APC), triggers the development of the vast majority of colorectal cancers. The Drosophila adult gut has recently emerged as a powerful model to elucidate the mechanisms by which Wingless/Wnt signaling regulates intestinal development, homeostasis, regeneration, and tumorigenesis. Herein, we review recent insights on the roles of Wnt signaling in Drosophila intestinal physiology and pathology.