Project description:The unfolded protein response (UPR) maintains endoplasmic reticulum (ER) homeostasis by sensing protein-folding stress and orchestrating cellular adaptation via the ER-transmembrane proteins IRE1, PERK and ATF6. Malignant cells can co-opt UPR signaling by IRE1 and PERK to sustain tumor growth; however, the importance of ATF6 in cancer remains poorly deciphered. We observed elevated ATF6 transcriptional activity in several cancers including colorectal carcinoma (CRC). Genetic silencing or small molecule inhibition of ATF6 blocked cell cycle progression and reduced viability of several human CRC cell lines in vitro and disrupted tumor progression in vivo. Unexpectedly, ATF6 interference also disabled Myc and Wnt signaling and reduced stemness. ATF6 inhibition attenuated growth of organoids derived from malignant but not normal human intestinal tissue, reducing Wnt-pathway activity and driving cellular differentiation. Wnt-surrogate agonism rescued the growth inhibitory phenotype of ATF6 interference. Our findings identify ATF6 as an unexpected facilitator of oncogenic Wnt signaling in CRC.
Project description:The unfolded protein response maintains endoplasmic reticulum (ER) homeostasis by sensing protein-folding stress and orchestrating cellular adaptation via the ER-transmembrane proteins IRE1, PERK and ATF6. Malignant cells can co-opt IRE1 and PERK to sustain growth; however, the importance of ATF6 in cancer remains poorly deciphered. We observed elevated ATF6 transcriptional activity in several cancers including colorectal carcinoma (CRC). Genetic silencing or small molecule inhibition of ATF6 blocked cell cycle progression and reduced viability of several human CRC cell lines in vitro and disrupted tumor progression in vivo. Unexpectedly, ATF6 interference disabled Wnt and Myc signaling and reduced stemness. ATF6 inhibition attenuated growth of organoids derived from malignant but not normal human intestinal tissue, decreasing Wnt-pathway activity and driving cellular differentiation. Wnt-surrogate agonism in a Wnt-dependent CRC organoid restored pathway activity and rescued growth under ATF6 blockade. Our findings identify ATF6 as an unexpected facilitator of oncogenic Wnt signaling in CRC.
Project description:The unfolded protein response maintains endoplasmic reticulum (ER) homeostasis by sensing protein-folding stress and orchestrating cellular adaptation via the ER-transmembrane proteins IRE1, PERK and ATF6. Malignant cells can co-opt IRE1 and PERK to sustain growth; however, the importance of ATF6 in cancer remains poorly deciphered. We observed elevated ATF6 transcriptional activity in several cancers including colorectal carcinoma (CRC). Genetic silencing or small molecule inhibition of ATF6 blocked cell cycle progression and reduced viability of several human CRC cell lines in vitro and disrupted tumor progression in vivo. Unexpectedly, ATF6 interference disabled Wnt and Myc signaling and reduced stemness. ATF6 inhibition attenuated growth of organoids derived from malignant but not normal human intestinal tissue, decreasing Wnt-pathway activity and driving cellular differentiation. Wnt-surrogate agonism in a Wnt-dependent CRC organoid restored pathway activity and rescued growth under ATF6 blockade. Our findings identify ATF6 as an unexpected facilitator of oncogenic Wnt signaling in CRC.
Project description:Background & Aims: Hierarchical organization of intestine relies on their stem cells by self-renew and producing committed progenitors. Although signals like Wnt are known to animate the continued renewal by maintaining intestinal stem cells (ISCs) activity, molecular mechanisms especially E3 ubiquitin ligases that modulate ISCs ‘stemness’ and supportive niche have not been well understood. Here, we investigated the role of Cullin 4B (Cul4b) in regulating ISC functions. Methods: We generated mice with intestinal epithelial-specific disruption of Cul4b (pVillin-cre; Cul4bfn/Y), inducible disruption of Cul4b (Lgr5-creERT2; Cul4bfn/Y, CAG-creERT2; Cul4bfn/Y) and their control (Cul4bfn/Y). Intestinal tissues were analyzed by histology, immunofluorescence, RNA sequencing and mass spectrum. Intestinal organoids deprived from mice with pVillin-Cre; Cul4bfn/Y, Lgr5-Cre; Cul4bfn/Y, Tg-Cul4b and their controls were used in assays to measure intestinal self-renewal, proliferation and differentiation. Wnt signaling and intestinal markers were analyzed by immunofluorescence and immunoblot assays. Differential proteins upon Cul4b ablation or Cul4b-interacting proteins were identified by mass spectrometry. Results: Cul4b specifically located at ISCs zone. Block of Cul4b impaired intestinal homeostasis maintenance by reduced self-renewal and proliferation. Transcriptome analysis revealed that Cul4b-null intestine lose ISC characterization and showed disturbed ISC niche. Mechanistically, reactivated Wnt pathway could recover intestinal dysfunction of Cul4b knockout mice. Analysis of differential total and ubiquitylated proteins uncovered the novel targeting substrate of Cullin-Ring ubiquitin ligase 4b (CRL4b), immunity-related GTPase family M member 1 (Irgm1) in intestine. Decreased Irgm1 rescued abnormally interferon signaling, overemphasized autophagy and downstream phosphate proteins in Cul4b knockout mice. Conclusion: We conclude that Cul4b is essential for ISC self-renewal and Paneth cell function by targeting Irgm1 and modulating Wnt signaling. Our results demonstrate that Cul4b is a novel ISC stemness and niche regulator.
Project description:Background and Purpose: Our previous work reported that galaxamide, a cyclopeptide extracted from the seaweed Galaxaura filamentosa, showed antiproliferative activity against HeLa cells by MTT assay. However, the therapeutic effects in vivo and potential mechanisms to eliminate cervical cancer cells remain unknown. Experimental Approach: HeLa cells were obtained as a cervical carcinoma in vitro model. The growth-inhibitory effects of galaxamide in HeLa cells and xenograft mouse models were investigated. RNA-seq was employed to analyse the main target of galaxamide in HeLa cells. Immunostaining, qRT‒PCR and Western blotting were applied to test the pharmacological effects in vitro and in vivo. Key Results: Galaxamide significantly inhibited cell growth, colony formation, migration, and invasion and induced cell apoptosis by inhibiting the Wnt signalling pathway in HeLa cells. RNA sequencing revealed that galaxamide regulated stemness via the Wnt6 signalling pathway in HeLa cells. By analysing The Cancer Genome Atlas database (TCGA), Wnt6 was found to be negatively/positively correlated with stemness- and apoptosis-related genes in human cervical cancer. Cancer stem-like cells (CSCs) isolated and enriched from HeLa cells demonstrated elevated Wnt6 and β-catenin genes compared with nonstem HeLa cells. After galaxamide treatment, CSCs showed abrogation of sphere-forming ability, along with inhibition of stemness-related and Wnt pathway genes. Galaxamide treatment was accompanied by the induction of apoptosis in HeLa cells, which was consistent with the results in BALB/c nude mice. Conclusion and Implications: Our results provide preclinical evidence that suppression of stemness by downregulating the Wnt signalling pathway is the molecular mechanism by which galaxamide effectively inhibits cell growth and induces apoptosis in cervical cancer cells.
Project description:ATF6 encodes a transcription factor that is activated during the Unfolded Protein Response to protect cells from ER stress. Loss of ATF6α and its paralog ATF6β, results in embryonic lethality, notochord dysgenesis, and in people, loss of ATF6α specifically, results in malformed neuroretina and congenital vision loss. These phenotypes implicate an essential role for ATF6 during vertebrate development. We investigated the function of ATF6 in development using human stem cells undergoing differentiation into multipotent germ layers, nascent tissues, and organs. We artificially activated ATF6 in stem cells with a recently identified small molecule ATF6 agonist, and we inhibited ATF6 using iPSCs from patients harboring ATF6 mutations. We discovered that ATF6 suppresses pluripotency, enhances differentiation, and surprisingly, guides stem cells toward mesodermal cell fates. Our findings reveal a novel role for ATF6 during differentiation and identify a new strategy to robustly create mesodermal tissues through modulation of the ATF6 arm of the UPR.
Project description:We previously showed that the combination of markers LNGFR+ and THY-1+ can be used selectively to isolate human mesenchymal stem cells (hMSCs) in bone marrow and several tissues. However, the molecular mechanisms regulating stemness of hMSCs remain to be elucidated. In this study, we found that Frizzled 5 (FZD5) and Receptor tyrosine kinase-like orphan receptor 2 (ROR2) were highly enriched in LNGFR+THY-1+ derived clones that retain a high potential for proliferation (rapidly expanding clones; RECs). WNT5A, the ligand of FZD5, causes FZD5 and ROR2 to co-localize and activates non-canonical Wnt pathway in RECs. Moreover, FZD5 knockdown attenuated proliferation and caused senescence. In contrast, FZD5 overexpression delayed senescence. These results indicate that intrinsic activation of non-canonical Wnt signaling via FZD5 and ROR2 modulates stemness and senescence of RECs. Thus, control of non-canonical Wnt signaling would enable us to regulate hMSC quality and to enhance the efficacy of cell-replacement therapy using hMSCs.