The Synthetic Small Molecule FL3 Combats Intestinal Tumorigenesis via Axin1-Mediated Inhibition of Wnt/beta-Catenin Signaling
Authors: Jackson, Dakota N.; Alula, Kibrom M.; Delgado-Deida, Yaritza; Tabti, Redouane; Turner, Kevin; Wang, Xuan; Venuprasad, K.; Souza, Rhonda F.; Desaubry, Laurent; Theiss, Arianne L.
Colorectal cancer exhibits aberrant activation of Wnt/beta-catenin signaling. Many inhibitors of the Wnt/beta-catenin pathway have been tested for Wnt-dependent cancers including colorectal cancer, but are unsuccessful due to severe adverse reactions. FL3 is a synthetic derivative of natural products called flavaglines, which exhibit anti-inflammatory and cytoprotective properties in intestinal epithelial cells, but has not been previously tested in cell or preclinical models of intestinal tumorigenesis. In vitro studies suggest that flavaglines target prohibitin 1 (PHB1) as a ligand, but this has not been established in the intestine. PHB1 is a highly conserved protein with diverse functions that depend on its posttranslational modifications and subcellular localization. Here, we demonstrate that FL3 combats intestinal tumorigenesis in the azoxymethane-dextran sodium sulfate and Apc(Min/+) mouse models and in human colorectal cancer tumor organoids (tumoroids) by inhibiting Wnt/beta-catenin signaling via induction of Axin1 expression. FL3 exhibited no change in cell viability in normal intestinal epithelial cells or human matched-normal colonoids. FL3 response was diminished in colorectal cancer cell lines and human colorectal cancer tumoroids harboring a mutation at S45 of beta-catenin. PHB1 deficiency in mice or in human colorectal cancer tumoroids abolished FL3-induced expression of Axin1 and drove tumoroid death. In colorectal cancer cells, FL3 treatment blocked phosphorylation of PHB1 at Thr258, resulting in its nuclear translocation and binding to the Axin1 promoter. These results suggest that FL3 inhibits Wnt/beta-catenin signaling via PHB1-dependent activation of Axin1. FL3, therefore, represents a novel compound that combats Wnt pathway-dependent cancers, such as colorectal cancer. Significance: Targeting of PHB1 by FL3 provides a novel mechanism to combat Wnt-driven cancers, with limited intestinal toxicity.
In VivoImaging of Local Inflammation: Monitoring LPS-Induced CD80/CD86 Upregulation by PET
MOLECULAR IMAGING AND BIOLOGY
Authors: Taddio, Marco F.; Castro Jaramillo, Claudia A.; Runge, Peter; Blanc, Alain; Keller, Claudia; Talip, Zeynep; Behe, Martin; van der Meulen, Nicholas P.; Halin, Cornelia; Schibli, Roger; Kramer, Stefanie D.
Purpose The co-stimulatory molecules CD80 and CD86 are upregulated on activated antigen-presenting cells (APC). We investigated whether local APC activation, induced by subcutaneous (s.c.) inoculation of lipopolysaccharides (LPS), can be imaged by positron emission tomography (PET) with CD80/CD86-targeting(64)Cu-labelled abatacept. Procedures Mice were inoculated s.c. with extracellular-matrix gel containing either LPS or vehicle (PBS). Immune cell populations were analysed by flow cytometry and marker expression by RT-qPCR.Cu-64-NODAGA-abatacept distribution was analysed using PET/CT andex vivobiodistribution. Results The number of CD80(+)and CD86(+)immune cells at the LPS inoculation site significantly increased a few days after inoculation. CD68 and CD86 expression were higher at the LPS than the PBS inoculation site, and CD80 was only increased at the LPS inoculation site. CTLA-4 was highest 10 days after LPS inoculation, when CD80/CD86 decreased again. A few days after inoculation,Cu-64-NODAGA-abatacept distribution to the inoculation site was significantly higher for LPS than PBS (4.2-fold). Co-administration of unlabelled abatacept or human immunoglobulin reduced tracer uptake. The latter reduced the number of CD86(+)immune cells at the LPS inoculation site. Conclusions CD80 and CD86 are upregulated in an LPS-induced local inflammation, indicating invasion of activated APCs.Cu-64-NODAGA-abatacept PET allowed following APC activation over time.