Significance: The Wnt pathway is implicated in multiple cancers, but to date no pharmacologically acceptable Wnt inhibitors have been introduced into the clinic. Analogs of the natural product prodigiosin are in early leukemia trials, but their mechanisms of action have not been established. We report that prodigiosin and its analog obatoclax block Wnt signaling at nanomolar concentrations by preventing the phosphorylation of Dishevelled. Cyclin D is an established target of Wnt signaling, and elevated cyclin D levels are characteristic of advanced breast cancer. In a Wnt-driven murine transgenic model of breast cancer, prodigiosin potently diminished cyclin D levels and blocked the growth of tumors. These results provide a rationale for the introduction of prodigiosin analogs into clinical trials of advanced breast cancer.

Gigantol is a bibenzyl compound derived from several medicinal orchids. This biologically active compound has been shown to have promising therapeutic potential against cancer cells, but its mechanism of action remains unclear. The inhibitory effect of gigantol on Wnt/β-catenin signaling was evaluated with the SuperTOPFlash reporter system. The levels of phosphorylated low-density lipoprotein receptor related protein 6 (LRP6), total LRP6 and cytosolic β-catenin were determined by Western blot analysis. The expression of Wnt target genes was analyzed using real-time PCR. Cell viability was measured with a MTT assay. The effect of gigantol on cell migration was examined using scratch wound-healing and transwell migration assays. Gigantol decreased the level of phosphorylated LRP6 and cytosolic β-catenin in HEK293 cells. In breast cancer MDA-MB-231 and MDA-MB-468 cells, treatment with gigantol reduced the level of phosphorylated LRP6, total LRP6 and cytosolic β-catenin in a dose-dependent manner, resulting in a decrease in the expression of Wnt target genes Axin2 and Survivin. We further demonstrated that gigantol suppressed the viability and migratory capacity of breast cancer cells. Gigantol is a novel inhibitor of the Wnt/β-catenin pathway. It inhibits Wnt/β-catenin signaling through downregulation of phosphorylated LRP6 and cytosolic β-catenin in breast cancer cells.

Background and Purpose: Salinomycin is a well‐known inhibitor of human cancer stem cells ( CSCs ). However, the molecular mechanism(s) by which salinomycin targets colorectal CSCs is poorly understood. Here, we have investigated underlying antitumour mechanisms of salinomycin in colorectal cancer cells and three tumour models. Experimental Approach: The inhibitory effect of salinomycin on the Wnt/β‐catenin pathway was analysed with the SuperTopFlash reporter system. The mRNA expression of Wnt target genes was evaluated with real‐time PCR. Effects of salinomycin on β‐catenin/TCF4E interaction were examined using co‐immunoprecipitation and an in vitro GST pull‐down assay. Cell proliferation was determined by BrdU incorporation and soft agar colony formation assay. The stemness of the cells was assessed by sphere formation assay. Antitumour effects of salinomycin on colorectal cancers was evaluated with colorectal CSC xenografts, APC ^min/+ transgenic mice, and patient‐derived colorectal tumour xenografts. Key Results: Salinomycin blocked β‐catenin/TCF4E complex formation in colorectal cancer cells and in an in vitro GST pull‐down assay, thus decreasing expression of Wnt target genes. Salinomycin also suppressed the transcriptional activity mediated by β‐catenin/LEF1 or β‐catenin/TCF4E complex and exhibited an inhibitory effect on the sphere formation, proliferation, and anchorage‐independent growth of colorectal cancer cells. In colorectal tumour xenografts and APC ^min/+ transgenic mice, administration of salinomycin significantly reduced tumour growth and the expression of CSC‐related Wnt target genes including LGR5. Conclusions and Implications: Our study suggested that salinomycin could suppress the growth of colorectal cancer by disrupting the β‐catenin/TCF complex and thus may be a promising agent for colorectal cancer treatment.

Ribosome-inactivating proteins (RIPs) belong to a family of enzymes that attack eukaryotic ribosomes and potently inhibit cellular protein synthesis. RIPs possess several biomedical properties, including anti-viral and anti-tumor activities. Multiple RIPs are known to inhibit tumor cell proliferation through inducing apoptosis in a variety of cancers, such as breast cancer, leukemia/lymphoma, and hepatoma. This review focuses on the anti-tumor activities of RIPs and their apoptotic effects through three closely related pathways: mitochondrial, death receptor, and endoplasmic reticulum pathways.

Significance: The phorbol ester 12- O -tetra-decanoylphorbol-13-acetate (TPA) is a well-known tumor promoter in two-stage mouse skin carcinogenesis, but the exact mechanism by which TPA promotes tumorigenesis remains elusive. This study discovered that TPA could stabilize CK1ε, enhance its kinase activity, and induce phosphorylation of LRP6, resulting in the formation of CK1ε–LRP6–axin1 complex, which may bypass the requirement of Wnt–Fzd–Dvl complex. TPA also increased the interaction between β-catenin and TCF4E in a CK1ε/δ-dependent way, and finally led to activation of the Wnt/β-catenin pathway. Our findings reveal a pathway by which TPA activates the Wnt/β-catenin signaling cascade. This pathway may represent a common mechanism for the tumor-promoting activity of some carcinogenic agents.

Background: The kinesin-13 family member 2C (KIF2C) is a versatile protein participating in many biological processes. KIF2C is frequently up-regulated in multiple types of cancer and is associated with cancer development. However, the role of KIF2C in immune cell infiltration of tumor microenvironment and immunotherapy in breast cancer remains unclear.Methods: The expression of KIF2C was analyzed using Tumor Immune Estimation Resource (TIMER) database and further verified by immunohistochemical staining in human breast cancer tissues. The correlation between KIF2C expression and clinical parameters, the impact of KIF2C on clinical prognosis and independent prognostic factors were analyzed by using TCGA database, the Kaplan-Meier plotter, and Univariate and multivariate Cox analyses, respectively. The nomograms were constructed according to independent prognostic factors and validated with C-index, calibration curves, ROC curves, and decision curve analysis. A gene set enrichment analysis (GSEA) was performed to explore the underlying molecular mechanisms of KIF2C. The degree of immune infiltration was assessed by the Estimation of Stromal and Immune cells in Malignant Tumor tissues using the Expression (ESTIMATE) algorithm and the single sample GSEA (ssGSEA). The Tumor mutational burden and Tumor Immune Dysfunction and Rejection (TIDE) were used to analyze immunotherapeutic efficiency. Finally, the KIF2C-related competing endogenous RNA (ceRNA) network was constructed to predict the putative regulatory mechanisms of KIF2C.Results: KIF2C was remarkably up-regulated in 18 different types of cancers, including breast cancer. Kaplan-Meier survival analysis showed that high KIF2C expression was associated with poor overall survival (OS). KIF2C expression was associated with clinical parameters such as age, TMN stage, T status, and molecular subtypes. We identified age, stage, estrogen receptor (ER) and KIF2C expression as OS-related independent prognosis factors for breast cancer. An OS-related nomogram was developed based on these independent prognosis factors and displayed good predicting ability for OS of breast cancer patients. Finally, our results revealed that KIF2C was significantly related to immune cell infiltration, tumor mutational burden, and immunotherapy in patients with breast cancer.Conclusion: KIF2C was overexpressed in breast cancer and was positively correlated with immune cell infiltration and immunotherapy response. Therefore, KIF2C can serve as a potential biomarker for prognosis and immunotherapy in breast cancer.