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Diegel CR, Michalski MN, Williams BO. β-catenin-dependent High Bone Mass Induced by Loss of APC in Osteoblasts Does Not Require Lrp5 or Lrp6. MicroPubl Biol 2023; 2023:10.17912/micropub.biology.001000. [PMID: 37908496 PMCID: PMC10613880 DOI: 10.17912/micropub.biology.001000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/09/2023] [Accepted: 10/13/2023] [Indexed: 11/02/2023]
Abstract
The requirement for LRP5 and LRP6 to prevent β-catenin degradation in the absence of the tumor suppressor APC is unclear because cell culture models have yielded conflicting results. We previously established that osteoblast-specific loss of APC causes β-catenin accumulation and increased bone mass, while loss of both LRP5 and LRP6 reduces bone mass. We report here that the simultaneous loss of APC, LRP5, and LRP6 in osteoblasts in mice phenocopies the APC osteoblast-specific knockout. Thus, β-catenin stabilization and increased bone mass after loss of APC in osteoblasts in vivo are not dependent on LRP5 and LRP6.
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Affiliation(s)
| | | | - Bart O. Williams
- Department of Cell Biology and Director, Core Technologies and Services, Van Andel Institute
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2
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Erazo-Oliveras A, Muñoz-Vega M, Mlih M, Thiriveedi V, Salinas ML, Rivera-Rodríguez JM, Kim E, Wright RC, Wang X, Landrock KK, Goldsby JS, Mullens DA, Roper J, Karpac J, Chapkin RS. Mutant APC reshapes Wnt signaling plasma membrane nanodomains by altering cholesterol levels via oncogenic β-catenin. Nat Commun 2023; 14:4342. [PMID: 37468468 PMCID: PMC10356786 DOI: 10.1038/s41467-023-39640-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 06/21/2023] [Indexed: 07/21/2023] Open
Abstract
Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly dynamic nano-assemblies at the plasma membrane. However, little is known regarding the role of oncogenic APC in reshaping Wnt nanodomains. This is noteworthy, because oncogenic APC does not act autonomously and requires activation of Wnt effectors upstream of APC to drive aberrant Wnt signaling. Here, we demonstrate the role of oncogenic APC in increasing plasma membrane free cholesterol and rigidity, thereby modulating Wnt signaling hubs. This results in an overactivation of Wnt signaling in the colon. Finally, using the Drosophila sterol auxotroph model, we demonstrate the unique ability of exogenous free cholesterol to disrupt plasma membrane homeostasis and drive Wnt signaling in a wildtype APC background. Collectively, these findings provide a link between oncogenic APC, loss of plasma membrane homeostasis and CRC development.
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Affiliation(s)
- Alfredo Erazo-Oliveras
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Mónica Muñoz-Vega
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Mohamed Mlih
- Department of Cell Biology and Genetics, Texas A&M University, School of Medicine, Bryan, TX, 77807, USA
| | - Venkataramana Thiriveedi
- Department of Medicine, Division of Gastroenterology, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Michael L Salinas
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Jaileen M Rivera-Rodríguez
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Eunjoo Kim
- Division of Pulmonary Sciences and Critical Care Medicine, School of Medicine, University of Colorado Anschutz Medical Campus, Denver, CO, 80045, USA
| | - Rachel C Wright
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
| | - Xiaoli Wang
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
| | - Kerstin K Landrock
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
| | - Jennifer S Goldsby
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Destiny A Mullens
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA
| | - Jatin Roper
- Department of Medicine, Division of Gastroenterology, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Jason Karpac
- Department of Cell Biology and Genetics, Texas A&M University, School of Medicine, Bryan, TX, 77807, USA
| | - Robert S Chapkin
- Program in Integrative Nutrition and Complex Diseases, Texas A&M University, College Station, TX, 77843, USA.
- Department of Nutrition, Texas A&M University, College Station, TX, 77843, USA.
- CPRIT Regional Center of Excellence in Cancer Research, Texas A&M University, College Station, TX, 77843, USA.
- Center for Environmental Health Research, Texas A&M University, College Station, TX, 77843, USA.
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Shishido A, Miyo M, Oishi K, Nishiyama N, Wu M, Yamamoto H, Kouda S, Wu X, Shibata S, Yokoyama Y, Yamamoto H. The Relationship between LRP6 and Wnt/β-Catenin Pathway in Colorectal and Esophageal Cancer. Life (Basel) 2023; 13:life13030615. [PMID: 36983771 PMCID: PMC10057833 DOI: 10.3390/life13030615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 02/21/2023] [Accepted: 02/21/2023] [Indexed: 02/25/2023] Open
Abstract
High expression of low-density lipoprotein receptor-related protein 6 (LRP6), a key component of the Wnt/β-catenin signaling pathway, is reported to be associated with malignant potential in some solid tumors including breast cancer and hepatocellular carcinoma. Few reports, however, have examined its function and clinical significance in colorectal cancers (CRC) demonstrating constitutive activation of Wnt signaling. Here, we compared the expression level and function of LRP6 in CRC with that of esophageal squamous cell carcinoma (ESCC) bearing few Wnt/β-catenin pathway mutations. On immunohistochemical staining, high LRP6 expression was noted in three of 68 cases (4.4%), and high β-catenin in 38 of 67 cases (56.7%) of CRC. High LRP6 expression was found in 21 of 82 cases (25.6%), and high β-catenin expression in 29 of 73 cases (39.7%) of ESCC. In our in vitro studies, LRP6 knockdown hardly changed Wnt signaling activity in CRC cell lines with mutations in Wnt signaling downstream genes. In contrast, in ESCC cell lines without Wnt signaling-related mutations, LRP6 knockdown significantly decreased Wnt signaling activity. LRP6 function may depend on constitutive activation of Wnt signaling.
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Affiliation(s)
- Akemi Shishido
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Masaaki Miyo
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
- Department of Surgery, Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Yamadaoka 2-2, Suita City 565-0871, Japan
| | - Kazuki Oishi
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Natsumi Nishiyama
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Meiqiao Wu
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Hiroyuki Yamamoto
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Shihori Kouda
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Xin Wu
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Satoshi Shibata
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Yuhki Yokoyama
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
| | - Hirofumi Yamamoto
- Department of Molecular Pathology, Division of Health Sciences, Graduate School of Medicine, Osaka University, Yamadaoka 1-7, Suita City 565-0871, Japan
- Department of Surgery, Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Yamadaoka 2-2, Suita City 565-0871, Japan
- Correspondence: ; Tel.: +81-6-6879-2591
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Kassel S, Hanson AJ, Benchabane H, Saito-Diaz K, Cabel CR, Goldsmith L, Taha M, Kanuganti A, Ng VH, Xu G, Ye F, Picker J, Port F, Boutros M, Weiss VL, Robbins DJ, Thorne CA, Ahmed Y, Lee E. USP47 deubiquitylates Groucho/TLE to promote Wnt-β-catenin signaling. Sci Signal 2023; 16:eabn8372. [PMID: 36749823 PMCID: PMC10038201 DOI: 10.1126/scisignal.abn8372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The Wnt-β-catenin signal transduction pathway is essential for embryonic development and adult tissue homeostasis. Wnt signaling converts TCF from a transcriptional repressor to an activator in a process facilitated by the E3 ligase XIAP. XIAP-mediated monoubiquitylation of the transcriptional corepressor Groucho (also known as TLE) decreases its affinity for TCF, thereby allowing the transcriptional coactivator β-catenin to displace it on TCF. Through a genome-scale screen in cultured Drosophila melanogaster cells, we identified the deubiquitylase USP47 as a positive regulator of Wnt signaling. We found that USP47 was required for Wnt signaling during Drosophila and Xenopus laevis development, as well as in human cells, indicating evolutionary conservation. In human cells, knockdown of USP47 inhibited Wnt reporter activity, and USP47 acted downstream of the β-catenin destruction complex. USP47 interacted with TLE3 and XIAP but did not alter their amounts; however, knockdown of USP47 enhanced XIAP-mediated ubiquitylation of TLE3. USP47 inhibited ubiquitylation of TLE3 by XIAP in vitro in a dose-dependent manner, suggesting that USP47 is the deubiquitylase that counteracts the E3 ligase activity of XIAP on TLE. Our data suggest a mechanism by which regulated ubiquitylation and deubiquitylation of TLE enhance the ability of β-catenin to cycle on and off TCF, thereby helping to ensure that the expression of Wnt target genes continues only as long as the upstream signal is present.
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Affiliation(s)
- Sara Kassel
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Alison J. Hanson
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Hassina Benchabane
- Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Kenyi Saito-Diaz
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Carly R. Cabel
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, AZ 85724, USA
| | - Lily Goldsmith
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Muhammad Taha
- Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Aksheta Kanuganti
- Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Victoria H. Ng
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - George Xu
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Fei Ye
- Department of Biostatistics, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Julia Picker
- Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Fillip Port
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany
| | - Michael Boutros
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics and Department of Cell and Molecular Biology, Medical Faculty Mannheim, Heidelberg University, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany
| | - Vivian L. Weiss
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - David J. Robbins
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC, USA
| | - Curtis A. Thorne
- Department of Cellular and Molecular Medicine, University of Arizona Cancer Center, Tucson, AZ 85724, USA
| | - Yashi Ahmed
- Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
- Corresponding authors. (Y.A.), (E.L.)
| | - Ethan Lee
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA
- Vanderbilt Ingram Cancer Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
- Corresponding authors. (Y.A.), (E.L.)
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5
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Cantoria MJ, Alizadeh E, Ravi J, Varghese RP, Bunnag N, Pond KW, Kettenbach AN, Ahmed Y, Paek AL, Tyson JJ, Doubrovinski K, Lee E, Thorne CA. Feedback in the β-catenin destruction complex imparts bistability and cellular memory. Proc Natl Acad Sci U S A 2023; 120:e2208787120. [PMID: 36598937 DOI: 10.1073/pnas.2208787120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Wnt ligands are considered classical morphogens, for which the strength of the cellular response is proportional to the concentration of the ligand. Herein, we show an emergent property of bistability arising from feedback among the Wnt destruction complex proteins that target the key transcriptional co-activator β-catenin for degradation. Using biochemical reconstitution, we identified positive feedback between the scaffold protein Axin and the kinase glycogen synthase kinase 3 (GSK3). Theoretical modeling of this feedback between Axin and GSK3 suggested that the activity of the destruction complex exhibits bistable behavior. We experimentally confirmed these predictions by demonstrating that cellular cytoplasmic β-catenin concentrations exhibit an "all-or-none" response with sustained memory (hysteresis) of the signaling input. This bistable behavior was transformed into a graded response and memory was lost through inhibition of GSK3. These findings provide a mechanism for establishing decisive, switch-like cellular response and memory upon Wnt pathway stimulation.
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Raisch J, Côté-Biron A, Langlois MJ, Leblanc C, Rivard N. Unveiling the Roles of Low-Density Lipoprotein Receptor-Related Protein 6 in Intestinal Homeostasis, Regeneration and Oncogenesis. Cells 2021; 10:1792. [PMID: 34359960 DOI: 10.3390/cells10071792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 07/05/2021] [Accepted: 07/12/2021] [Indexed: 12/26/2022] Open
Abstract
Intestinal epithelial self-renewal is tightly regulated by signaling pathways controlling stem cell proliferation, determination and differentiation. In particular, Wnt/β-catenin signaling controls intestinal crypt cell division, survival and maintenance of the stem cell niche. Most colorectal cancers are initiated by mutations activating the Wnt/β-catenin pathway. Wnt signals are transduced through Frizzled receptors and LRP5/LRP6 coreceptors to downregulate GSK3β activity, resulting in increased nuclear β-catenin. Herein, we explored if LRP6 expression is required for maintenance of intestinal homeostasis, regeneration and oncogenesis. Mice with an intestinal epithelial cell-specific deletion of Lrp6 (Lrp6IEC-KO) were generated and their phenotype analyzed. No difference in intestinal architecture nor in proliferative and stem cell numbers was found in Lrp6IEC-KO mice in comparison to controls. Nevertheless, using ex vivo intestinal organoid cultures, we found that LRP6 expression was critical for crypt cell proliferation and stem cell maintenance. When exposed to dextran sodium sulfate, Lrp6IEC-KO mice developed more severe colitis than control mice. However, loss of LRP6 did not affect tumorigenesis in ApcMin/+ mice nor growth of human colorectal cancer cells. By contrast, Lrp6 silencing diminished anchorage-independent growth of BRafV600E-transformed intestinal epithelial cells (IEC). Thus, LRP6 controls intestinal stem cell functionality and is necessary for BRAF-induced IEC oncogenesis.
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Zhong ZA, Michalski MN, Stevens PD, Sall EA, Williams BO. Regulation of Wnt receptor activity: Implications for therapeutic development in colon cancer. J Biol Chem 2021; 296:100782. [PMID: 34000297 PMCID: PMC8214085 DOI: 10.1016/j.jbc.2021.100782] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 05/05/2021] [Accepted: 05/10/2021] [Indexed: 12/13/2022] Open
Abstract
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.
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Affiliation(s)
- Zhendong A Zhong
- Department of Cell Biology, Van Andel Institute, Grand Rapids, Michigan, USA
| | - Megan N Michalski
- Department of Cell Biology, Van Andel Institute, Grand Rapids, Michigan, USA
| | - Payton D Stevens
- Department of Cell Biology, Van Andel Institute, Grand Rapids, Michigan, USA
| | - Emily A Sall
- Department of Cell Biology, Van Andel Institute, Grand Rapids, Michigan, USA
| | - Bart O Williams
- Department of Cell Biology, Van Andel Institute, Grand Rapids, Michigan, USA.
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Shen C, Nayak A, Melendez RA, Wynn DT, Jackson J, Lee E, Ahmed Y, Robbins DJ. Casein Kinase 1α as a Regulator of Wnt-Driven Cancer. Int J Mol Sci 2020; 21:E5940. [PMID: 32824859 DOI: 10.3390/ijms21165940] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 08/10/2020] [Accepted: 08/14/2020] [Indexed: 12/13/2022] Open
Abstract
Wnt signaling regulates numerous cellular processes during embryonic development and adult tissue homeostasis. Underscoring this physiological importance, deregulation of the Wnt signaling pathway is associated with many disease states, including cancer. Here, we review pivotal regulatory events in the Wnt signaling pathway that drive cancer growth. We then discuss the roles of the established negative Wnt regulator, casein kinase 1α (CK1α), in Wnt signaling. Although the study of CK1α has been ongoing for several decades, the bulk of such research has focused on how it phosphorylates and regulates its various substrates. We focus here on what is known about the mechanisms controlling CK1α, including its putative regulatory proteins and alternative splicing variants. Finally, we describe the discovery and validation of a family of pharmacological CK1α activators capable of inhibiting Wnt pathway activity. One of the important advantages of CK1α activators, relative to other classes of Wnt inhibitors, is their reduced on-target toxicity, overcoming one of the major impediments to developing a clinically relevant Wnt inhibitor. Therefore, we also discuss mechanisms that regulate CK1α steady-state homeostasis, which may contribute to the deregulation of Wnt pathway activity in cancer and underlie the enhanced therapeutic index of CK1α activators.
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Raisch J, Côté-Biron A, Rivard N. A Role for the WNT Co-Receptor LRP6 in Pathogenesis and Therapy of Epithelial Cancers. Cancers (Basel) 2019; 11:E1162. [PMID: 31412666 DOI: 10.3390/cancers11081162] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 08/08/2019] [Accepted: 08/09/2019] [Indexed: 02/06/2023] Open
Abstract
The WNT/β-catenin signaling pathway controls stem and progenitor cell proliferation, survival and differentiation in epithelial tissues. Aberrant stimulation of this pathway is therefore frequently observed in cancers from epithelial origin. For instance, colorectal and hepatic cancers display activating mutations in the CTNNB1 gene encoding β-catenin, or inactivating APC and AXIN gene mutations. However, these mutations are uncommon in breast and pancreatic cancers despite nuclear β-catenin localization, indicative of pathway activation. Notably, the low-density lipoprotein receptor-related protein 6 (LRP6), an indispensable co-receptor for WNT, is frequently overexpressed in colorectal, liver, breast and pancreatic adenocarcinomas in association with increased WNT/β -catenin signaling. Moreover, LRP6 is hyperphosphorylated in KRAS-mutated cells and in patient-derived colorectal tumours. Polymorphisms in the LRP6 gene are also associated with different susceptibility to developing specific types of lung, bladder and colorectal cancers. Additionally, recent observations suggest that LRP6 dysfunction may be involved in carcinogenesis. Indeed, reducing LRP6 expression and/or activity inhibits cancer cell proliferation and delays tumour growth in vivo. This review summarizes current knowledge regarding the biological function and regulation of LRP6 in the development of epithelial cancers—especially colorectal, liver, breast and pancreatic cancers.
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