PORCN inhibition synergizes with PI3K/mTOR inhibition in Wnt-addicted cancers

Combination Therapy Approach to Overcome the Resistance to PI3K Pathway Inhibitors in Gynecological Cancers

The PI3K signaling pathway plays an essential role in cancer cell proliferation and survival. PI3K pathway inhibitors are now FDA-approved as a single agent treatment or in combination for solid tumors such as renal cell carcinoma or breast cancer. However, despite the high prevalence of PI3K pathway alterations in gynecological cancers and promising preclinical activity in endometrial and ovarian cancer models, PI3K pathway inhibitors showed limited clinical activity in gynecological cancers. In this review, we provide an overview on resistance mechanisms against PI3K pathway inhibitors that limit their use in gynecological malignancies, including genetic alterations that reactivate the PI3K pathway such as PIK3CA mutations and PTEN loss, compensatory signaling pathway activation, and feedback loops causing the reactivation of the PI3K signaling pathway. We also discuss the successes and limitations of recent clinical trials aiming to address such resistance mechanisms through combination therapies.

Wnt/β-catenin signaling pathway in carcinogenesis and cancer therapy

The Wnt/β-catenin signaling pathway plays a crucial role in various physiological processes, encompassing development, tissue homeostasis, and cell proliferation. Under normal physiological conditions, the Wnt/β-catenin signaling pathway is meticulously regulated. However, aberrant activation of this pathway and downstream target genes can occur due to mutations in key components of the Wnt/β-catenin pathway, epigenetic modifications, and crosstalk with other signaling pathways. Consequently, these dysregulations contribute significantly to tumor initiation and progression. Therapies targeting the Wnt/β-catenin signaling transduction have exhibited promising prospects and potential for tumor treatment. An increasing number of medications targeting this pathway are continuously being developed and validated. This comprehensive review aims to summarize the latest advances in our understanding of the role played by the Wnt/β-catenin signaling pathway in carcinogenesis and targeted therapy, providing valuable insights into acknowledging current opportunities and challenges associated with targeting this signaling pathway in cancer research and treatment.

Recurrent mutations in tumor suppressor FBXW7 bypass Wnt/β-catenin addiction in cancer

Pathologic Wnt/β-catenin signaling drives various cancers, leading to multiple approaches to drug this pathway. Appropriate patient selection can maximize success of these interventions. Wnt ligand addiction is a druggable vulnerability in RNF43-mutant/RSPO-fusion cancers. However, pharmacologically targeting the biogenesis of Wnt ligands, e.g., with PORCN inhibitors, has shown mixed therapeutic responses, possibly due to tumor heterogeneity. Here, we show that the tumor suppressor FBXW7 is frequently mutated in RNF43-mutant/RSPO-fusion tumors, and FBXW7 mutations cause intrinsic resistance to anti-Wnt therapies. Mechanistically, FBXW7 inactivation stabilizes multiple oncoproteins including Cyclin E and MYC and antagonizes the cytostatic effect of Wnt inhibitors. Moreover, although FBXW7 mutations do not mitigate β-catenin degradation upon Wnt inhibition, FBXW7-mutant RNF43-mutant/RSPO-fusion cancers instead lose dependence on β-catenin signaling, accompanied by dedifferentiation and loss of lineage specificity. These FBXW7-mutant Wnt/β-catenin-independent tumors are susceptible to multi-cyclin-dependent kinase inhibition. An in-depth understanding of primary resistance to anti-Wnt/β-catenin therapies allows for more appropriate patient selection and use of alternative mechanism-based therapies.

Recent advances in drug delivery and targeting for the treatment of pancreatic cancer

Despite significant treatment efforts, pancreatic ductal adenocarcinoma (PDAC), the deadliest solid tumor, is still incurable in the preclinical stages due to multifacet stroma, dense desmoplasia, and immune regression. Additionally, tumor heterogeneity and metabolic changes are linked to low grade clinical translational outcomes, which has prompted the investigation of the mechanisms underlying chemoresistance and the creation of effective treatment approaches by selectively targeting genetic pathways. Since targeting upstream molecules in first-line oncogenic signaling pathways typically has little clinical impact, downstream signaling pathways have instead been targeted in both preclinical and clinical studies. In this review, we discuss how the complexity of various tumor microenvironment (TME) components and the oncogenic signaling pathways that they are connected to actively contribute to the development and spread of PDAC, as well as the ways that recent therapeutic approaches have been targeted to restore it. We also illustrate how many endogenous stimuli-responsive linker-based nanocarriers have recently been developed for the specific targeting of distinct oncogenes and their downstream signaling cascades as well as their ongoing clinical trials. We also discuss the present challenges, prospects, and difficulties in the development of first-line oncogene-targeting medicines for the treatment of pancreatic cancer patients.

Molecular basis of Wnt biogenesis, secretion, and Wnt7-specific signaling

Wnt proteins are enzymatically lipidated by Porcupine (PORCN) in the ER and bind to Wntless (WLS) for intracellular transport and secretion. Mechanisms governing the transfer of these low-solubility Wnts from the ER to the extracellular space remain unclear. Through structural and functional analyses of Wnt7a, a crucial Wnt involved in central nervous system angiogenesis and blood-brain barrier maintenance, we have elucidated the principles of Wnt biogenesis and Wnt7-specific signaling. The Wnt7a-WLS complex binds to calreticulin (CALR), revealing that CALR functions as a chaperone to facilitate Wnt transfer from PORCN to WLS during Wnt biogenesis. Our structures, functional analyses, and molecular dynamics simulations demonstrate that a phospholipid in the core of Wnt-bound WLS regulates the association and dissociation between Wnt and WLS, suggesting a lipid-mediated Wnt secretion mechanism. Finally, the structure of Wnt7a bound to RECK, a cell-surface Wnt7 co-receptor, reveals how RECKCC4 engages the N-terminal domain of Wnt7a to activate Wnt7-specific signaling.

AUM302, a novel triple kinase PIM/PI3K/mTOR inhibitor, is a potent in vitro pancreatic cancer growth inhibitor

Pancreatic cancer is one of the leading causes of cancer deaths, with pancreatic ductal adenocarcinoma (PDAC) being the most common subtype. Advanced stage diagnosis of PDAC is common, causing limited treatment opportunities. Gemcitabine is a frequently used chemotherapeutic agent which can be used as a monotherapy or in combination. However, tumors often develop resistance to gemcitabine. Previous studies show that the proto-oncogene PIM kinases (PIM1 and PIM3) are upregulated in PDAC compared to matched normal tissue and are related to chemoresistance and PDAC cell growth. The PIM kinases are also involved in the PI3K/AKT/mTOR pathway to promote cell survival. In this study, we evaluate the effect of the novel multikinase PIM/PI3K/mTOR inhibitor, AUM302, and commercially available PIM inhibitor, TP-3654. Using five human PDAC cell lines, we found AUM302 to be a potent inhibitor of cell proliferation, cell viability, cell cycle progression, and phosphoprotein expression, while TP-3654 was less effective. Significantly, AUM302 had a strong impact on the viability of gemcitabine-resistant PDAC cells. Taken together, these results demonstrate that AUM302 exhibits antitumor activity in human PDAC cells and thus has the potential to be an effective drug for PDAC therapy.

The mechanisms of class 1A PI3K and Wnt/β-catenin coupled signaling in breast cancer

The class IA PI3K signaling pathway is activated by growth factor stimulation and regulates a signaling cascade that promotes diverse events including cell growth, proliferation, migration and metabolism. PI3K signaling is one of the most commonly hyperactivated pathways in breast cancer, leading to increased tumor growth and progression. PI3K hyperactivation occurs via a number of genetic and epigenetic mechanisms including mutation or amplification of PIK3CA, the gene encoding the p110α subunit of PI3Kα, as well as via dysregulation of the upstream growth factor receptors or downstream signaling effectors. Over the past decade, extensive efforts to develop therapeutics that suppress oncogenic PI3K signaling have been undertaken. Although FDA-approved PI3K inhibitors are now emerging, their clinical success remains limited due to adverse effects and negative feedback mechanisms which contribute to their reduced efficacy. There is an emerging body of evidence demonstrating crosstalk between the PI3K and Wnt/β-catenin pathways in breast cancer. However, PI3K exhibits opposing effects on Wnt/β-catenin signaling in distinct tumor subsets, whereby PI3K promotes Wnt/β-catenin activation in ER+ cancers, but paradoxically suppresses this pathway in ER- breast cancers. This review discusses the molecular mechanisms for PI3K-Wnt crosstalk in breast cancer, and how Wnt-targeted therapies have the potential to contribute to treatment regimens for breast cancers with PI3K dysregulation.

PORCN promotes hepatocellular carcinogenesis via Wnt/β-catenin-dependent manner

Background

Porcupine O-acyltransferase (PORCN), a membrane-bound O-acyltransferase, is crucial in Wnt ligand palmitoylation. However, the roles of PORCN in the development of hepatocellular carcinoma (HCC) remain unknown.

Methods

Western blot, real-time quantitative polymerase chain reaction (RT-qPCR) assays, and The Cancer Genome Atlas (TCGA) database were used to study the expression and prognostic values of PORCN in patients with HCC. Following this, Cell Counting Kit-8 (CCK-8), wound-healing tests, Transwell assay, and a xenograft mouse model were employed to examine the effect of PORCN on HCC cells. Finally, the underlying molecular mechanisms involved in cell proliferation and migration caused by PORCN were identified.

Results

The protein and messenger RNA (mRNA) levels of PORCN in HCC tissues were higher than those of adjacent normal tissues. The analysis of TCGA database indicated that patients with higher PORCN expression had a lower overall survival (OS) rate. Overexpression of PORCN could promote the proliferation and migration abilities of HCC cells both in vitro and in vivo. Gene set enrichment analysis (GSEA) showed that the effect of PORCN on the biological characteristics of HCC cells mainly centered on the Wnt-β-catenin signaling pathway. Mechanically, immunofluorescence staining and subcellular protein fraction assays showed that PORCN could induce epithelial-mesenchymal transition (EMT) by promoting the translocation of β-catenin from the cytoplasm to nucleus, ultimately promoting the progression of HCC.

Conclusions

The findings of this study suggest that PORCN can promote HCC cell proliferation and migration by stimulating the Wnt-β-catenin signaling pathway. Therefore, PORCN may be a promising therapeutic target for HCC.

Wnt Signaling Inhibitors and Their Promising Role in Tumor Treatment

In a continuous search for the improvement of antitumor therapies, the inhibition of the Wnt signaling pathway has been recognized as a promising target. The altered functioning of the Wnt signaling in human tumors points to the strategy of the inhibition of its activity that would impact the clinical outcomes and survival of patients. Because the Wnt pathway is often mutated or epigenetically altered in tumors, which promotes its activation, inhibitors of Wnt signaling are being intensively investigated. It has been shown that knocking down specific components of the Wnt pathway has inhibitory effects on tumor growth in vivo and in vitro. Thus, similar effects are expected from the application of Wnt inhibitors. In the last decades, molecules acting as inhibitors on the pathway’s specific molecular levels have been identified and characterized. This review will discuss the inhibitors of the canonical Wnt pathway, summarize knowledge on their effectiveness as therapeutics, and debate their side effects. The role of the components frequently mutated in various tumors that are principal targets for Wnt inhibitors is also going to be brought to the reader’s attention. Some of the molecules identified as Wnt pathway inhibitors have reached early stages of clinical trials, and some have only just been discovered. All things considered, inhibition of the Wnt signaling pathway shows potential for the development of future therapies.

The Roles of Secreted Wnt Ligands in Cancer

Wnt ligands are secreted signaling proteins that display a wide range of biological effects. They play key roles in stimulating Wnt signaling pathways to facilitate processes such as tissue homeostasis and regeneration. Dysregulation of Wnt signaling is a hallmark of many cancers and genetic alterations in various Wnt signaling components, which result in ligand-independent or ligand-dependent hyperactivation of the pathway that have been identified. Recently, research is focusing on the impact of Wnt signaling on the interaction between tumor cells and their micro-environment. This Wnt-mediated crosstalk can act either in a tumor promoting or suppressing fashion. In this review, we comprehensively outline the function of Wnt ligands in different tumor entities and their impact on key phenotypes, including cancer stemness, drug resistance, metastasis, and immune evasion. Lastly, we elaborate approaches to target Wnt ligands in cancer therapy.

The role of Evi/Wntless in exporting Wnt proteins

Intercellular communication by Wnt proteins governs many essential processes during development, tissue homeostasis and disease in all metazoans. Many context-dependent effects are initiated in the Wnt-producing cells and depend on the export of lipidated Wnt proteins. Although much focus has been on understanding intracellular Wnt signal transduction, the cellular machinery responsible for Wnt secretion became better understood only recently. After lipid modification by the acyl-transferase Porcupine, Wnt proteins bind their dedicated cargo protein Evi/Wntless for transport and secretion. Evi/Wntless and Porcupine are conserved transmembrane proteins, and their 3D structures were recently determined. In this Review, we summarise studies and structural data highlighting how Wnts are transported from the ER to the plasma membrane, and the role of SNX3-retromer during the recycling of its cargo receptor Evi/Wntless. We also describe the regulation of Wnt export through a post-translational mechanism and review the importance of Wnt secretion for organ development and cancer, and as a future biomarker.

Whole genome sequencing of Malaysian colorectal cancer patients reveals specific druggable somatic mutations

The incidences of colorectal cancer (CRC) are continuously increasing in some areas of the world, including Malaysia. In this study, we aimed to characterize the landscape of somatic mutations using the whole-genome sequencing approach and identify druggable somatic mutations specific to Malaysian patients. Whole-genome sequencing was performed on the genomic DNA obtained from 50 Malaysian CRC patients' tissues. We discovered the top significantly mutated genes were APC, TP53, KRAS, TCF7L2 and ACVR2A. Four novel, non-synonymous variants were identified in three genes, which were KDM4E, MUC16 and POTED. At least one druggable somatic alteration was identified in 88% of our patients. Among them were two frameshift mutations in RNF43 (G156fs and P192fs) predicted to have responsive effects against the Wnt pathway inhibitor. We found that the exogenous expression of this RNF43 mutation in CRC cells resulted in increased cell proliferation and sensitivity against LGK974 drug treatment and G1 cell cycle arrest. In conclusion, this study uncovered our local CRC patients' genomic landscape and druggable alterations. It also highlighted the role of specific RNF43 frameshift mutations, which unveil the potential of an alternative treatment targeting the Wnt/β-Catenin signalling pathway and could be beneficial, especially to Malaysian CRC patients.

Target c-Myc to treat pancreatic cancer

C-Myc overexpression is a common finding in pancreatic cancer and predicts the aggressive behavior of cancer cells. It binds to the promoter of different genes, thereby regulating their transcription. C-Myc is downstream of KRAS and interacts with several oncogenic and proliferative pathways in pancreatic cancer. C-Myc enhances aerobic glycolysis in cancer cells and regulates glutamate biosynthesis from glutamine. It provides enough energy for cancer cells' metabolism and sufficient substrate for the synthesis of organic molecules. C-Myc overexpression is associated with chemoresistance, intra-tumor angiogenesis, epithelial-mesenchymal transition (EMT), and metastasis in pancreatic cancer. Despite its title, c-Myc is not "undruggable" and recent studies unveiled that it can be targeted, directly or indirectly. Small molecules that accelerate c-Myc ubiquitination and degradation have been effective in preclinical studies. Small molecules that hinder c-Myc-MAX heterodimerization or c-Myc/MAX/DNA complex formation can functionally inhibit c-Myc. In addition, c-Myc can be targeted through transcriptional, post-transcriptional, and translational modifications.

Blocking the Wnt/β‑catenin signaling pathway to treat colorectal cancer: Strategies to improve current therapies (Review)

Colorectal cancer (CRC) is one of the most common malignant tumor types occurring in the digestive system. The incidence of CRC has exhibits yearly increases and the mortality rate among patients with CRC is high. The Wnt/β‑catenin signaling pathway, which is associated with carcinogenesis, is abnormally activated in CRC. Most patients with CRC have adenomatous polyposis coli mutations, while half of the remaining patients have β‑catenin gene mutations. Therefore, targeting the Wnt/β‑catenin signaling pathway for the treatment of CRC is of clinical value. In recent years, with in‑depth research on the Wnt/β‑catenin signaling pathway, inhibitors have been developed that are able to suppress or hinder the development and progression of CRC. In the present review, the role of the Wnt/β‑catenin signaling pathway in CRC is summarized, the research status on Wnt/β‑catenin pathway inhibitors is outlined and potential targets for inhibition of this pathway are presented.

Targeting ligand-dependent wnt pathway dysregulation in gastrointestinal cancers through porcupine inhibition

Gastrointestinal cancers are responsible for more cancer deaths than any other system of the body. This review summarises how Wnt pathway dysregulation contributes to the development of the most common gastrointestinal cancers, with a particular focus on the nature and frequency of upstream pathway aberrations. Tumors with upstream aberrations maintain a dependency on the presence of functional Wnt ligand, and are predicted to be tractable to inhibitors of Porcupine, an enzyme that plays a key role in Wnt secretion. We summarise available pre-clinical efficacy data from Porcupine inhibitors in vitro and in vivo, as well as potential toxicities and the data from early phase clinical trials. We appraise the rationale for biomarker-defined targeted approaches, as well as outlining future opportunities for combination with other therapeutics.

Aberrant Cholesterol Metabolism and Wnt/β-Catenin Signaling Coalesce via Frizzled5 in Supporting Cancer Growth

Frizzled (Fzd) proteins are Wnt receptors and play essential roles in development, homeostasis, and oncogenesis. How Wnt/Fzd signaling is coupled to physiological regulation remains unknown. Cholesterol is reported as a signaling molecule regulating morphogen such as Hedgehog signaling. Despite the elusiveness of the in-depth mechanism, it is well-established that pancreatic cancer specially requires abnormal cholesterol metabolism levels for growth. In this study, it is unexpectedly found that among ten Fzds, Fzd5 has a unique capacity to bind cholesterol specifically through its conserved extracellular linker region. Cholesterol-binding enables Fzd5 palmitoylation, which is indispensable for receptor maturation and trafficking to the plasma membrane. In Wnt-addicted pancreatic ductal adenocarcinoma (PDAC), cholesterol stimulates tumor growth via Fzd5-mediated Wnt/β-catenin signaling. A natural oxysterol, 25-hydroxylsterol competes with cholesterol and inhibits Fzd5 maturation and Wnt signaling, thereby alleviating PDAC growth. This cholesterol-receptor interaction and ensuing receptor lipidation uncover a novel mechanism by which Fzd5 acts as a cholesterol sensor and pivotal connection coupling lipid metabolism to morphogen signaling. These findings further suggest that cholesterol-targeting may provide new therapeutic opportunities for treating Wnt-dependent cancers.

Porcn as a novel therapeutic target in cancer therapy: A review

Wingless-related integration site (Wnt) signaling is one of the main oncogenic pathways in different malignancies. Therefore, targeting this pathway has been considered an exciting strategy in cancer treatment. Porcn is among the central enzymes in this pathway that has recently been considered for cancer-targeted therapy. As a membrane-bound O-acyltransferase, Porcn plays a critical role in wnt ligand palmitoylation and its subsequent secretion. In addition to Porcn's role in stem cell signaling and differentiation, recent findings have shown its role in developing and progressing colorectal, pancreatic, liver, head, and neck cancers. Developed small molecule inhibitors have also opened a promising window toward cancer treatment strategies. In this review, the structure and biological role of Porcn in different cancer-related signaling pathways and inhibitors used for inhibiting this enzyme are discussed.

Initial Phase I Safety Study of Gedatolisib plus Cofetuzumab Pelidotin for Patients with Metastatic Triple-Negative Breast Cancer

PURPOSE

The PI3K pathway is dysregulated in the majority of triple-negative breast cancers (TNBC), yet single-agent inhibition of PI3K has been ineffective in TNBC. PI3K inhibition leads to an immediate compensatory upregulation of the Wnt pathway. Dual targeting of both pathways is highly synergistic against TNBC models in vitro and in vivo. We initiated a phase I clinical trial combining gedatolisib, a pan-class I isoform PI3K/mTOR inhibitor, and cofetuzumab pelidotin, an antibody-drug conjugate against the cell-surface PTK7 protein (Wnt pathway coreceptor) with an auristatin payload.

PATIENTS AND METHODS

Participants (pt) had metastatic TNBC or estrogen receptor (ER) low (ER and PgR < 5%, HER2-negative) breast cancer, and had received at least one prior chemotherapy for advanced disease. The primary objective was safety. Secondary endpoints included overall response rate (ORR), clinical benefit at 18 weeks (CB18), progression-free survival (PFS), and correlative analyses.

RESULTS

A total of 18 pts were enrolled in three dose cohorts: gedatolisib 110 mg weekly + cofetuzumab pelidotin 1.4 mg/kg every 3 weeks (n = 4), 180 mg + 1.4 mg/kg (n = 3), and 180 mg + 2.8 mg/kg (n = 11). Nausea, anorexia, fatigue, and mucositis were common but rarely reached ≥grade 3 severity. Myelosuppression was uncommon. ORR was 16.7% (3/18). An additional 3 pts had stable disease (of these 2 had stable disease for >18 weeks); CB18 was 27.8%. Median PFS was 2.0 months (95% confidence interval for PFS: 1.2-6.2). Pts with clinical benefit were enriched with genomic alterations in the PI3K and PTK7 pathways.

CONCLUSIONS

The combination of gedatolisib + cofetuzumab pelidotin was well tolerated and demonstrated promising clinical activity. Further investigation of this drug combination in metastatic TNBC is warranted.

A p300/GATA6 axis determines differentiation and Wnt dependency in pancreatic cancer models

Wnt signaling regulates the balance between stemness and differentiation in multiple tissues and in cancer. RNF43-mutant pancreatic cancers are dependent on Wnt production, and pharmacologic blockade of the pathway, e.g., by PORCN inhibitors, leads to tumor differentiation. However, primary resistance to these inhibitors has been observed. To elucidate potential mechanisms, we performed in vivo CRISPR screens in PORCN inhibitor-sensitive RNF43-mutant pancreatic cancer xenografts. As expected, genes in the Wnt pathway whose loss conferred drug resistance were identified, including APC, AXIN1, and CTNNBIP1. Unexpectedly, the screen also identified the histone acetyltransferase EP300 (p300), but not its paralog, CREBBP (CBP). We found that EP300 is silenced due to genetic alterations in all the existing RNF43-mutant pancreatic cancer cell lines that are resistant to PORCN inhibitors. Mechanistically, loss of EP300 directly downregulated GATA6 expression, thereby silencing the GATA6-regulated differentiation program and leading to a phenotypic transition from the classical subtype to the dedifferentiated basal-like/squamous subtype of pancreatic cancer. EP300 mutation and loss of GATA6 function bypassed the antidifferentiation activity of Wnt signaling, rendering these cancer cells resistant to Wnt inhibition.

Porcupine Inhibition Disrupts Mitochondrial Function and Homeostasis in WNT Ligand-Addicted Pancreatic Cancer

WNT signaling promotes pancreatic ductal adenocarcinoma (PDAC) through diverse effects on proliferation, differentiation, survival, and stemness. A subset of PDAC with inactivating mutations in ring finger protein 43 (RNF43) show growth dependency on autocrine WNT ligand signaling and are susceptible to agents that block WNT ligand acylation by Porcupine O-acyltransferase, which is required for proper WNT ligand processing and secretion. For this study, global transcriptomic, proteomic, and metabolomic analyses were performed to explore the therapeutic response of RNF43-mutant PDAC to the Porcupine inhibitor (PORCNi) LGK974. LGK974 disrupted cellular bioenergetics and mitochondrial function through actions that included rapid mitochondrial depolarization, reduced mitochondrial content, and inhibition of oxidative phosphorylation and tricarboxylic acid cycle. LGK974 also broadly altered transcriptional activity, downregulating genes involved in cell cycle, nucleotide metabolism, and ribosomal biogenesis and upregulating genes involved in epithelial-mesenchymal transition, hypoxia, endocytosis, and lysosomes. Autophagy and lysosomal activity were augmented in response to LGK974, which synergistically inhibited tumor cell viability in combination with chloroquine. Autocrine WNT ligand signaling dictates metabolic dependencies in RNF43-mutant PDAC through a combination of transcription dependent and independent effects linked to mitochondrial health and function. Metabolic adaptations to mitochondrial damage and bioenergetic stress represent potential targetable liabilities in combination with PORCNi for the treatment of WNT ligand-addicted PDAC.

In Vivo Modeling of Patient Genetic Heterogeneity Identifies New Ways to Target Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy of the bile ducts within the liver characterized by high levels of genetic heterogeneity. In the context of such genetic variability, determining which oncogenic mutations drive ICC growth has been difficult, and developing modes of patient stratification and targeted therapies remains challenging. Here we model the interactions between rare mutations with more common driver genes and combine in silico analysis of patient data with highly multiplexed in vivo CRISPR-spCas9 screens to perform a functional in vivo study into the role genetic heterogeneity plays in driving ICC. Novel tumor suppressors were uncovered, which, when lost, cooperate with the RAS oncoprotein to drive ICC growth. Focusing on a set of driver mutations that interact with KRAS to initiate aggressive, sarcomatoid-type ICC revealed that tumor growth relies on Wnt and PI3K signaling. Pharmacologic coinhibition of Wnt and PI3K in vivo impeded ICC growth regardless of mutational profile. Therefore, Wnt and PI3K activity should be considered as a signature by which patients can be stratified for treatment independent of tumor genotype, and inhibitors of these pathways should be levied to treat ICC.

SIGNIFICANCE

This work shows that, despite significant genetic heterogeneity, intrahepatic cholangiocarcinoma relies on a limited number of signaling pathways to grow, suggesting common therapeutic vulnerabilities across patients.

Sequential modulation of the Wnt/β-catenin signaling pathway enhances tumor-intrinsic MHC I expression and tumor clearance

BACKGROUND

Progress in immunotherapy use for gynecologic malignancies is hampered by poor tumor antigenicity and weak T cell infiltration of the tumor microenvironment (TME). Wnt/β-catenin pathway modulation demonstrated patient benefit in clinical trials as well as enhanced immune cell recruitment in preclinical studies. The purpose of this study was to characterize the pathways by which Wnt/β-catenin modulation facilitates a more immunotherapy-favorable TME.

METHODS

Human tumor samples and in vivo patient-derived xenograft and syngeneic murine models were administered Wnt/β-catenin modulating agents DKN-01 and CGX-1321 individually or in sequence. Analytical methods included immunohistochemistry, flow cytometry, multiplex cytokine/chemokine array, and RNA sequencing.

RESULTS

DKK1 blockade via DKN-01 increased HLA/MHC expression in human and murine tissues, correlating with heightened expression of known MHC I regulators: NFkB, IL-1, LPS, and IFNy. PORCN inhibition via CGX-1321 increased production of T cell chemoattractant CXCL10, providing a mechanism for observed increases in intra-tumoral T cells. Diverse leukocyte recruitment was noted with elevations in B cells and macrophages, with increased tumor expression of population-specific chemokines. Sequential DKK1 blockade and PORCN inhibition decreased tumor burden as evidenced by reduced omental weights.

CONCLUSIONS

Wnt/β-catenin pathway modulation increases MHC I expression and promotes tumor leukocytic infiltration, facilitating a pro-immune TME associated with decreased tumor burden. This intervention overcomes common tumor immune-evasion mechanisms and may render ovarian tumors susceptible to immunotherapy.

WNT/β-Catenin Pathway in Soft Tissue Sarcomas: New Therapeutic Opportunities?

Simple Summary

The WNT/β-catenin signaling pathway is involved in fundamental processes for the proliferation and differentiation of mesenchymal stem cells. However, little is known about its relevance for mesenchymal neoplasms, such us soft tissue sarcomas (STS). Chemotherapy based on doxorubicin (DXR) still remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be an unmatched goal. This review covers the most important molecular alterations of the WNT signaling pathway in STS, broadening the current knowledge about STS as well as identifying novel drug targets. Furthermore, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are discussed.

Abstract

Soft tissue sarcomas (STS) are a very heterogeneous group of rare tumors, comprising more than 50 different histological subtypes that originate from mesenchymal tissue. Despite their heterogeneity, chemotherapy based on doxorubicin (DXR) has been in use for forty years now and remains the standard first-line treatment for locally advanced unresectable or metastatic STS, although overall survival could not be improved by combination with other chemotherapeutics. In this sense, the development of new therapeutic approaches continues to be a largely unmatched goal. The WNT/β-catenin signaling pathway is involved in various fundamental processes for embryogenic development, including the proliferation and differentiation of mesenchymal stem cells. Although the role of this pathway has been widely researched in neoplasms of epithelial origin, little is known about its relevance for mesenchymal neoplasms. This review covers the most important molecular alterations of the WNT signaling pathway in STS. The detection of these alterations and the understanding of their functional consequences for those pathways controlling sarcomagenesis development and progression are crucial to broaden the current knowledge about STS as well as to identify novel drug targets. In this regard, the current therapeutic options and drug candidates to modulate WNT signaling, which are usually classified by their interaction site upstream or downstream of β-catenin, and their presumable clinical impact on STS are also discussed.

WNT as a Driver and Dependency in Cancer

The WNT signaling pathway is a critical regulator of development and adult tissue homeostasis and becomes dysregulated in many cancer types. Although hyperactivation of WNT signaling is common, the type and frequency of genetic WNT pathway alterations can vary dramatically between different cancers, highlighting possible cancer-specific mechanisms for WNT-driven disease. In this review, we discuss how WNT pathway disruption contributes to tumorigenesis in different organs and how WNT affects the tumor cell and immune microenvironment. Finally, we describe recent and ongoing efforts to target oncogenic WNT signaling as a therapeutic strategy. SIGNIFICANCE: WNT signaling is a fundamental regulator of tissue homeostasis and oncogenic driver in many cancer types. In this review, we highlight recent advances in our understanding of WNT signaling in cancer, particularly the complexities of WNT activation in distinct cancer types, its role in immune evasion, and the challenge of targeting the WNT pathway as a therapeutic strategy.

Wnt/β-catenin signaling in cancers and targeted therapies

Wnt/β-catenin signaling has been broadly implicated in human cancers and experimental cancer models of animals. Aberrant activation of Wnt/β-catenin signaling is tightly linked with the increment of prevalence, advancement of malignant progression, development of poor prognostics, and even ascendence of the cancer-associated mortality. Early experimental investigations have proposed the theoretical potential that efficient repression of this signaling might provide promising therapeutic choices in managing various types of cancers. Up to date, many therapies targeting Wnt/β-catenin signaling in cancers have been developed, which is assumed to endow clinicians with new opportunities of developing more satisfactory and precise remedies for cancer patients with aberrant Wnt/β-catenin signaling. However, current facts indicate that the clinical translations of Wnt/β-catenin signaling-dependent targeted therapies have faced un-neglectable crises and challenges. Therefore, in this study, we systematically reviewed the most updated knowledge of Wnt/β-catenin signaling in cancers and relatively targeted therapies to generate a clearer and more accurate awareness of both the developmental stage and underlying limitations of Wnt/β-catenin-targeted therapies in cancers. Insights of this study will help readers better understand the roles of Wnt/β-catenin signaling in cancers and provide insights to acknowledge the current opportunities and challenges of targeting this signaling in cancers.

The multidimensional role of the Wnt/β-catenin signaling pathway in human malignancies

Several signaling pathways have been identified as important for developmental processes. One of such important cascades is the Wnt/β-catenin signaling pathway, which can regulate various physiological processes such as embryonic development, tissue homeostasis, and tissue regeneration; while its dysregulation is implicated in several pathological conditions especially cancers. Interestingly, deregulation of the Wnt/β-catenin pathway has been reported to be closely associated with initiation, progression, metastasis, maintenance of cancer stem cells, and drug resistance in human malignancies. Moreover, several genetic and experimental models support the inhibition of the Wnt/β-catenin pathway to answer the key issues related to cancer development. The present review focuses on different regulators of Wnt pathway and how distinct mutations, deletion, and amplification in these regulators could possibly play an essential role in the development of several cancers such as colorectal, melanoma, breast, lung, and leukemia. Additionally, we also provide insights on diverse classes of inhibitors of the Wnt/β-catenin pathway, which are currently in preclinical and clinical trial against different cancers.

Impact of posttranslational modifications in pancreatic carcinogenesis and treatments

Pancreatic cancer (PC) is a highly aggressive cancer, with a 9% 5-year survival rate and a high risk of recurrence. In part, this is because PC is composed of heterogeneous subgroups with different biological and functional characteristics and personalized anticancer treatments are required. Posttranslational modifications (PTMs) play an important role in modifying protein functions/roles and are required for the maintenance of cell viability and biological processes; thus, their dysregulation can lead to disease. Different types of PTMs increase the functional diversity of the proteome, which subsequently influences most aspects of normal cell biology or pathogenesis. This review primarily focuses on ubiquitination, SUMOylation, and NEDDylation, as well as the current understanding of their roles and molecular mechanisms in pancreatic carcinogenesis. Additionally, we briefly summarize studies and clinical trials on PC treatments to advance our knowledge of drugs available to target the ubiquitination, SUMOylation, and NEDDylation PTM types. Further investigation of PTMs could be a critical field of study in relation to PC, as they have been implicated in the initiation and progression of many other types of cancer.

Adrenal cortex renewal in health and disease

Resident progenitor and/or stem cell populations in the adult adrenal cortex enable cortical cells to undergo homeostatic renewal and regeneration after injury. Renewal occurs predominantly in the outer layers of the adrenal gland but newly formed cells undergo centripetal migration, differentiation and lineage conversion in the process of forming the different functional steroidogenic zones. Over the past 10 years, advances in the genetic characterization of adrenal diseases and studies of mouse models with altered adrenal phenotypes have helped to elucidate the molecular pathways that regulate adrenal tissue renewal, several of which are fine-tuned via complex paracrine and endocrine influences. Moreover, the adrenal gland is a sexually dimorphic organ, and testicular androgens have inhibitory effects on cell proliferation and progenitor cell recruitment in the adrenal cortex. This Review integrates these advances, including the emerging role of sex hormones, into existing knowledge on adrenocortical cell renewal. An in-depth understanding of these mechanisms is expected to contribute to the development of novel therapies for severe endocrine diseases, for which current treatments are unsatisfactory.

Determination of the membrane topology of PORCN, an O-acyl transferase that modifies Wnt signalling proteins

Wnt gradients elicit distinct cellular responses, such as proliferation, specification, differentiation and survival in a dose-dependent manner. Porcupine (PORCN), a membrane-bound O-acyl transferase (MBOAT) that resides in the endoplasmic reticulum, catalyses the addition of monounsaturated palmitate to Wnt proteins and is required for Wnt gradient formation and signalling. In humans, PORCN mutations are causal for focal dermal hypoplasia (FDH), an X-linked dominant syndrome characterized by defects in mesodermal and endodermal tissues. PORCN is also an emerging target for cancer therapeutics. Despite the importance of this enzyme, its structure remains poorly understood. Recently, the crystal structure of DltB, an MBOAT family member from bacteria, was solved. In this report, we use experimental data along with homology modelling to DltB to determine the membrane topology of PORCN. Our studies reveal that PORCN has 11 membrane domains, comprising nine transmembrane spanning domains and two reentrant domains. The N-terminus is oriented towards the lumen while the C-terminus is oriented towards the cytosol. Like DltB, PORCN has a funnel-like structure that is encapsulated by multiple membrane-spanning helices. This new model for PORCN topology allows us to map residues that are important for biological activity (and implicated in FDH) onto its three-dimensional structure.

Pharmacological Wnt ligand inhibition overcomes key tumor-mediated resistance pathways to anti-PD-1 immunotherapy

While immune checkpoint blockade is associated with prolonged responses in multiple cancers, most patients still do not benefit from this therapeutic strategy. The Wnt-β-catenin pathway is associated with diminished T cell infiltration; however, activating mutations are rare, implicating a role for autocrine/paracrine Wnt ligand-driven signaling in immune evasion. In this study, we show that proximal mediators of the Wnt signaling pathway are associated with anti-PD-1 resistance, and pharmacologic inhibition of Wnt ligand signaling supports anti-PD-1 efficacy by reversing dendritic cell tolerization and the recruitment of granulocytic myeloid-derived suppressor cells in autochthonous tumor models. We further demonstrate that the inhibition of Wnt signaling promotes the development of a tumor microenvironment that is more conducive to favorable responses to checkpoint blockade in cancer patients. These findings support a rationale for Wnt ligand-focused treatment approaches in future immunotherapy clinical trials and suggest a strategy for selecting those tumors more responsive to Wnt inhibition.

WNT Ligand Dependencies in Pancreatic Cancer

WNT signaling promotes the initiation and progression of pancreatic ductal adenocarcinoma (PDAC) through wide-ranging effects on cellular proliferation, survival, differentiation, stemness, and tumor microenvironment. Of therapeutic interest is a genetically defined subset of PDAC known to have increased WNT/β-catenin transcriptional activity, growth dependency on WNT ligand signaling, and response to pharmacologic inhibitors of the WNT pathway. Here we review mechanisms underlying WNT ligand addiction in pancreatic tumorigenesis, as well as the potential utility of therapeutic approaches that functionally antagonize WNT ligand secretion or frizzled receptor binding.

WNT inhibition creates a BRCA-like state in Wnt-addicted cancer

Wnt signaling maintains diverse adult stem cell compartments and is implicated in chemotherapy resistance in cancer. PORCN inhibitors that block Wnt secretion have proven effective in Wnt-addicted preclinical cancer models and are in clinical trials. In a survey for potential combination therapies, we found that Wnt inhibition synergizes with the PARP inhibitor olaparib in Wnt-addicted cancers. Mechanistically, we find that multiple genes in the homologous recombination and Fanconi anemia repair pathways, including BRCA1, FANCD2, and RAD51, are dependent on Wnt/β-catenin signaling in Wnt-high cancers, and treatment with a PORCN inhibitor creates a BRCA-like state. This coherent regulation of DNA repair genes occurs in part via a Wnt/β-catenin/MYBL2 axis. Importantly, this pathway also functions in intestinal crypts, where high expression of BRCA and Fanconi anemia genes is seen in intestinal stem cells, with further upregulation in Wnt-high APCmin mutant polyps. Our findings suggest a general paradigm that Wnt/β-catenin signaling enhances DNA repair in stem cells and cancers to maintain genomic integrity. Conversely, interventions that block Wnt signaling may sensitize cancers to radiation and other DNA damaging agents.

CrossTORC and WNTegration in Disease: Focus on Lymphangioleiomyomatosis

The mechanistic target of rapamycin (mTOR) and wingless-related integration site (Wnt) signal transduction networks are evolutionarily conserved mammalian growth and cellular development networks. Most cells express many of the proteins in both pathways, and this review will briefly describe only the key proteins and their intra- and extracellular crosstalk. These complex interactions will be discussed in relation to cancer development, drug resistance, and stem cell exhaustion. This review will also highlight the tumor-suppressive tuberous sclerosis complex (TSC) mutated, mTOR-hyperactive lung disease of women, lymphangioleiomyomatosis (LAM). We will summarize recent advances in the targeting of these pathways by monotherapy or combination therapy, as well as future potential treatments.

Pancreatic Cancer: Recent Progress of Drugs in Clinical Trials

Pancreatic cancer is a highly malignant tumor and one of the primary causes of cancer-related death. Because pancreatic cancer is difficult to diagnose in the early course of the disease, most patients present with advanced lesions at the time of diagnosis, and only 20% of patients are eligible for surgery. Consequently, drug treatment has become extremely important. At present, the main treatment regimens for pancreatic cancer are gemcitabine and the FORFIRINOX and MPACT regimens. However, none of these regimens substantially improves the prognosis of patients with pancreatic cancer. Extensive efforts have been dedicated to the study of pancreatic cancer in recent years. With the development and clinical application of biological targeted drugs, the biological targeted treatment of tumors has been widely accepted. Therefore, this article used relevant clinical trial data to summarize the research progress of traditional chemotherapy drugs and biological targeted drugs for the treatment of pancreatic cancer.

Regulation of Wnt Signaling Pathways at the Plasma Membrane and Their Misregulation in Cancer

Wnt signaling is one of the key signaling pathways that govern numerous physiological activities such as growth, differentiation and migration during development and homeostasis. As pathway misregulation has been extensively linked to pathological processes including malignant tumors, a thorough understanding of pathway regulation is essential for development of effective therapeutic approaches. A prominent feature of cancer cells is that they significantly differ from healthy cells with respect to their plasma membrane composition and lipid organization. Here, we review the key role of membrane composition and lipid order in activation of Wnt signaling pathway by tightly regulating formation and interactions of the Wnt-receptor complex. We also discuss in detail how plasma membrane components, in particular the ligands, (co)receptors and extracellular or membrane-bound modulators, of Wnt pathways are affected in lung, colorectal, liver and breast cancers that have been associated with abnormal activation of Wnt signaling. Wnt-receptor complex components and their modulators are frequently misexpressed in these cancers and this appears to correlate with metastasis and cancer progression. Thus, composition and organization of the plasma membrane can be exploited to develop new anticancer drugs that are targeted in a highly specific manner to the Wnt-receptor complex, rendering a more effective therapeutic outcome possible.

Mutations and mechanisms of WNT pathway tumour suppressors in cancer

Mutation-induced activation of WNT-β-catenin signalling is a frequent driver event in human cancer. Sustained WNT-β-catenin pathway activation endows cancer cells with sustained self-renewing growth properties and is associated with therapy resistance. In healthy adult stem cells, WNT pathway activity is carefully controlled by core pathway tumour suppressors as well as negative feedback regulators. Gene inactivation experiments in mouse models unequivocally demonstrated the relevance of WNT tumour suppressor loss-of-function mutations for cancer growth. However, in human cancer, a far more complex picture has emerged in which missense or truncating mutations mediate stable expression of mutant proteins, with distinct functional and phenotypic ramifications. Herein, we review recent advances and challenges in our understanding of how different mutational subsets of WNT tumour suppressor genes link to distinct cancer types, clinical outcomes and treatment strategies.

Pharmacologically Targeting the WNT/β-Catenin Signaling Cascade: Avoiding the Sword of Damocles

WNT/β-catenin signaling plays fundamental roles in numerous developmental processes and in adult tissue homeostasis and repair after injury, by controlling cellular self-renewal, activation, division, differentiation, movement, genetic stability, and apoptosis. As such, it comes as no surprise that dysregulation of WNT/β-catenin signaling is associated with various diseases, including cancer, fibrosis, neurodegeneration, etc. Although multiple agents that specifically target the WNT/β-catenin signaling pathway have been studied preclinically and a number have entered clinical trials, none has been approved by the FDA to date. In this chapter, we provide our insights as to the reason(s) it has been so difficult to safely pharmacologically target the WNT/β-catenin signaling pathway and discuss the significant efforts undertaken towards this goal.

Targeting Wnt Signaling for Gastrointestinal Cancer Therapy: Present and Evolving Views

Wnt signaling governs tissue development, homeostasis, and regeneration. However, aberrant activation of Wnt promotes tumorigenesis. Despite the ongoing efforts to manipulate Wnt signaling, therapeutic targeting of Wnt signaling remains challenging. In this review, we provide an overview of current clinical trials to target Wnt signaling, with a major focus on gastrointestinal cancers. In addition, we discuss the caveats and alternative strategies for therapeutically targeting Wnt signaling for cancer treatment.

Targeting the Wnt/β-catenin signaling pathway in cancer

The aberrant Wnt/β-catenin signaling pathway facilitates cancer stem cell renewal, cell proliferation and differentiation, thus exerting crucial roles in tumorigenesis and therapy response. Accumulated investigations highlight the therapeutic potential of agents targeting Wnt/β-catenin signaling in cancer. Wnt ligand/ receptor interface, β-catenin destruction complex and TCF/β-catenin transcription complex are key components of the cascade and have been targeted with interventions in preclinical and clinical evaluations. This scoping review aims at outlining the latest progress on the current approaches and perspectives of Wnt/β-catenin signaling pathway targeted therapy in various cancer types. Better understanding of the updates on the inhibitors, antagonists and activators of Wnt/β-catenin pathway rationalizes innovative strategies for personalized cancer treatment. Further investigations are warranted to confirm precise and secure targeted agents and achieve optimal use with clinical benefits in malignant diseases.

Widespread Repression of Gene Expression in Cancer by a Wnt/β-Catenin/MAPK Pathway

Aberrant Wnt signaling drives a number of cancers through regulation of diverse downstream pathways. Wnt/β-catenin signaling achieves this in part by increasing the expression of proto-oncogenes such as MYC and cyclins. However, global assessment of the Wnt-regulated transcriptome in vivo in genetically distinct cancers demonstrates that Wnt signaling suppresses the expression of as many genes as it activates. In this study, we examined the set of genes that are upregulated upon inhibition of Wnt signaling in Wnt-addicted pancreatic and colorectal cancer models. Decreasing Wnt signaling led to a marked increase in gene expression by activating ERK and JNK; these changes in gene expression could be mitigated in part by concurrent inhibition of MEK. These findings demonstrate that increased Wnt signaling in cancer represses MAPK activity, preventing RAS-mediated senescence while allowing cancer cells to proliferate. These results shift the paradigm from Wnt/β-catenin primarily as an activator of transcription to a more nuanced view where Wnt/β-catenin signaling drives both widespread gene repression and activation. SIGNIFICANCE: These findings show that Wnt/β-catenin signaling causes widespread gene repression via inhibition of MAPK signaling, thus fine tuning the RAS-MAPK pathway to optimize proliferation in cancer.

Manipulating the Wnt/β-catenin signaling pathway to promote anti-tumor immune infiltration into the TME to sensitize ovarian cancer to ICB therapy

OBJECTIVE

Immune checkpoint blockade (ICB) therapy shows limited efficacy in ovarian cancers due to the "cold" immune phenotype surrounding these tumors. Previous studies have shown that in ovarian cancer Wnt/β-catenin pathway activation contributes to this immune phenotype. Here, we evaluated the anti-tumor and immune-enhancing properties of the Wnt inhibitor, CGX-1321, used alone or in combination with either DKN-01 or anti-PD-1 therapy, in pre-clinical ovarian cancer models.

METHODS

The parental ID8 murine ovarian cancer model harboring a knock-out of p53 (ID8p53^-/-) and MISIIR-Tag spontaneous ovarian cancer models were used to test the effects of CGX-1321 alone or in combination therapies on tumor burden and immune cell landscape in the tumor microenvironment (TME). Flow cytometry and NanoString analyses were used to characterize the changes in tumor-intrinsic signaling and immune-related profiles in the TME of ovarian cancer in response to treatments.

RESULTS

CGX-1321 significantly reduced tumor burden and constrained tumor progression in the ID8p53^-/- and MISIIR-Tag models. Furthermore, CGX-1321 increased infiltrating CD8+ T cells in the TME. Combining CGX-1321 with either DKN-01 or anti-PD-1 therapy also decreased tumor burden and increased CD8+ T cell infiltration in the omentum TME but did not do so to a greater extent that CGX-1321 monotherapy.

CONCLUSIONS

CGX-1321 significantly reduced tumor burden and enhanced CD8+ T cell levels in ovarian cancer, nevertheless the addition of DKN-01 or anti-PD-1 therapies did not enhance these effects of CGX-1321. Further investigation is needed to determine if CGX-1321 + DKN-01 combination treatment sensitizes pre-clinical ovarian cancer to ICB therapy.

Exploring Dysregulated Signaling Pathways in Cancer

Cancer cell biology takes advantage of identifying diverse cellular signaling pathways that are disrupted in cancer. Signaling pathways are an important means of communication from the exterior of cell to intracellular mediators, as well as intracellular interactions that govern diverse cellular processes. Oncogenic mutations or abnormal expression of signaling components disrupt the regulatory networks that govern cell function, thus enabling tumor cells to undergo dysregulated mitogenesis, to resist apoptosis, and to promote invasion to neighboring tissues. Unraveling of dysregulated signaling pathways may advance the understanding of tumor pathophysiology and lead to the improvement of targeted tumor therapy. In this review article, different signaling pathways and how their dysregulation contributes to the development of tumors have been discussed.

Wnt-regulated lncRNA discovery enhanced by in vivo identification and CRISPRi functional validation

BACKGROUND

Wnt signaling is an evolutionarily conserved developmental pathway that is frequently hyperactivated in cancer. While multiple protein-coding genes regulated by Wnt signaling are known, the functional lncRNAs regulated by Wnt signaling have not been systematically characterized.

METHODS

We comprehensively mapped Wnt-regulated lncRNAs from an orthotopic Wnt-addicted pancreatic cancer model and examined the response of lncRNAs to Wnt inhibition between in vivo and in vitro cancer models. We further annotated and characterized these Wnt-regulated lncRNAs using existing genomic classifications (using data from FANTOM5) in the context of Wnt signaling and inferred their role in cancer pathogenesis (using GWAS and expression data from the TCGA). To functionally validate Wnt-regulated lncRNAs, we performed CRISPRi screens to assess their role in cancer cell proliferation both in vivo and in vitro.

RESULTS

We identified 3633 lncRNAs, of which 1503 were regulated by Wnt signaling in an orthotopic Wnt-addicted pancreatic cancer model. These lncRNAs were much more sensitive to changes in Wnt signaling in xenografts than in cultured cells. Our analysis suggested that Wnt signaling inhibition could influence the co-expression relationship of Wnt-regulated lncRNAs and their eQTL-linked protein-coding genes. Wnt-regulated lncRNAs were also implicated in specific gene networks involved in distinct biological processes that contribute to the pathogenesis of cancers. Consistent with previous genome-wide lncRNA CRISPRi screens, around 1% (13/1503) of the Wnt-regulated lncRNAs were found to modify cancer cell growth in vitro. This included CCAT1 and LINC00263, previously reported to regulate cancer growth. Using an in vivo CRISPRi screen, we doubled the discovery rate, identifying twice as many Wnt-regulated lncRNAs (25/1503) that had a functional effect on cancer cell growth.

CONCLUSIONS

Our study demonstrates the value of studying lncRNA functions in vivo, provides a valuable resource of lncRNAs regulated by Wnt signaling, and establishes a framework for systematic discovery of functional lncRNAs.

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.

Fasting inhibits aerobic glycolysis and proliferation in colorectal cancer via the Fdft1-mediated AKT/mTOR/HIF1α pathway suppression

Evidence suggests that fasting exerts extensive antitumor effects in various cancers, including colorectal cancer (CRC). However, the mechanism behind this response is unclear. We investigate the effect of fasting on glucose metabolism and malignancy in CRC. We find that fasting upregulates the expression of a cholesterogenic gene, Farnesyl-Diphosphate Farnesyltransferase 1 (FDFT1), during the inhibition of CRC cell aerobic glycolysis and proliferation. In addition, the downregulation of FDFT1 is correlated with malignant progression and poor prognosis in CRC. Moreover, FDFT1 acts as a critical tumor suppressor in CRC. Mechanistically, FDFT1 performs its tumor-inhibitory function by negatively regulating AKT/mTOR/HIF1α signaling. Furthermore, mTOR inhibitor can synergize with fasting in inhibiting the proliferation of CRC. These results indicate that FDFT1 is a key downstream target of the fasting response and may be involved in CRC cell glucose metabolism. Our results suggest therapeutic implications in CRC and potential crosstalk between a cholesterogenic gene and glycolysis.

The molecular mechanisms underpinning how fasting inhibits tumourigenesis are not completely elucidated. Here, the authors show that fasting upregulates the cholesterogenic gene FDFT1 which leads to decreased AKT/mTOR/HIF1a signalling and glycolysis reduction in colorectal cancer.

An update on Wnt signaling pathway in cancer

Wnt signaling involves many aspects of development, cell biology and physiology. Mutations in the Wnt gene can lead to abnormal embryonic development and cancer formation, including various aspects that affect proliferation, morphogenesis, and differentiation. The occurrence and development of tumors is a complex process involving multiple factors. The Wnt signaling pathway participates in this process as an anti-tumor target by activating multiple gene transcriptions. The emergence of Wnt pathway inhibitors and targeted drugs has opened up a new world of cancer treatment. This review focuses on the mechanism of action of the Wnt signaling pathway in different cancers. Secondly, we have organized and introduced the latest Wnt anti-tumor drugs.

Wnt Signaling and Drug Resistance in Cancer

Wnts are secreted proteins that bind to cell surface receptors to activate downstream signaling cascades. Normal Wnt signaling plays key roles in embryonic development and adult tissue homeostasis. The secretion of Wnt ligands, the turnover of Wnt receptors, and the signaling transduction are tightly regulated and fine-tuned to keep the signaling output "just right." Hyperactivated Wnt signaling due to recurrent genetic alterations drives several human cancers. Elevated Wnt signaling also confers resistance to multiple conventional and targeted cancer therapies through diverse mechanisms including maintaining the cancer stem cell population, enhancing DNA damage repair, facilitating transcriptional plasticity, and promoting immune evasion. Different classes of Wnt signaling inhibitors targeting key nodes of the pathway have been developed and show efficacy in treating Wnt-driven cancers and subverting Wnt-mediated therapy resistance in preclinical studies. Several of these inhibitors have advanced to clinical trials, both singly and in combination with other existing US Food and Drug Administration-approved anti-cancer modalities. In the near future, pharmacological inhibition of Wnt signaling may be a real choice for patients with cancer. SIGNIFICANCE STATEMENT: The latest insights in Wnt signaling, ranging from basic biology to therapeutic implications in cancer, are reviewed. Recent studies extend understanding of this ancient signaling pathway and describe the development and improvement of anti-Wnt therapeutic modalities for cancer.