Amlexanox and UPF1 Modulate Wnt Signaling and Apoptosis in HCT-116 Colorectal Cancer Cells

Advances in molecular function of UPF1 in Cancer

It is known that more than 10 % of genetic diseases are caused by a mutation in protein-coding mRNA (premature termination codon; PTC). mRNAs with an early stop codon are degraded by the cellular surveillance process known as nonsense-mediated mRNA decay (NMD), which prevents the synthesis of C-terminally truncated proteins. Up-frameshift-1 (UPF1) has been reported to be involved in the downregulation of various cancers, and low expression of UPF1 was shown to correlate with poor prognosis. It is known that UPF1 is a master regulator of nonsense-mediated mRNA decay (NMD). UPF1 may also function as an E3 ligase and degrade target proteins without using mRNA decay mechanisms. Increasing evidence indicates that UPF1 could serve as a good biomarker for cancer diagnosis and treatment for future therapeutic applications. Long non-coding RNAs (lncRNAs) have the ability to bind different proteins and regulate gene expression; this role in cancer cells has already been identified by different studies. This article provides an overview of the aberrant expression of UPF1, its functional properties, and molecular processes during cancer for clinical applications in cancer. We also discussed the interactions of lncRNA with UPF1 for cell growth during tumorigenesis.

Amlexanox: Readthrough Induction and Nonsense-Mediated mRNA Decay Inhibition in a Charcot-Marie-Tooth Model of hiPSCs-Derived Neuronal Cells Harboring a Nonsense Mutation in GDAP1 Gene

Nonsense mutations are involved in multiple peripheral neuropathies. These mutations induce the presence of a premature termination codon (PTC) at the mRNA level. As a result, a dysfunctional or truncated protein is synthesized, or even absent linked to nonsense-mediated mRNA degradation (NMD) system activation. Readthrough molecules or NMD inhibitors could be innovative therapies in these hereditary neuropathies, particularly molecules harboring the dual activity as amlexanox. Charcot-Marie-Tooth (CMT) is the most common inherited pathology of the peripheral nervous system, affecting 1 in 2500 people worldwide. Nonsense mutations in the GDAP1 gene have been associated with a severe form of CMT, prompting us to investigate the effect of readthrough and NMD inhibitor molecules. Although not clearly defined, GDAP1 could be involved in mitochondrial functions, such as mitophagy. We focused on the homozygous c.581C>G (p.Ser194*) mutation inducing CMT2H using patient human induced pluripotent stem cell (hiPSC)-derived neuronal cells. Treatment during 20 h with 100 µM of amlexanox on this cell model stabilized GDAP1 mRNAs carrying UGA-PTC and induced a restoration of the mitochondrial morphology. These results highlight the potential of readthrough molecules associated to NMD inhibitors for the treatment of genetic alterations in CMT, opening the way for future investigations and a potential therapy.

Oncogenic and Receptor-Mediated Wnt Signaling Influence the Sensitivity of Colonic Cells to Butyrate

Deregulated Wnt signaling is responsible for most cases of colorectal cancer (CRC). Dietary fiber is protective against CRC and this activity is likely mediated by butyrate, a breakdown product of dietary fiber that hyperactivates Wnt signaling, repressing CRC proliferation and inducing apoptosis. Receptor-mediated Wnt signaling and oncogenic Wnt signaling, which is typically initiated by mutation in more downstream elements of the pathway, activate non-overlapping patterns of gene expression. Receptor-mediated signaling is associated with a poor prognosis for CRC while oncogenic signaling is associated with a relatively good prognosis. We have compared the expression of genes differentially expressed in receptor-mediated vs. oncogenic Wnt signaling to microarray data generated in our laboratory. Most importantly we evaluated these gene expression patterns comparing the early stage colon microadenoma line LT97 with the metastatic CRC cell line SW620. LT97 cells exhibit a gene expression pattern more strongly associated with that observed with oncogenic Wnt signaling, while SW620 cells exhibit a gene expression pattern moderately associated with that observed with receptor-mediated Wnt signaling. Given that SW620 cells are more advanced and malignant compared to LT97 cells, these findings are generally consistent with the better prognosis observed with tumors exhibiting a more oncogenic Wnt gene expression pattern. Importantly, LT97 cells are more sensitive to the effects of butyrate on proliferation and apoptosis that are CRC cells. We further examine these gene expression patterns in butyrate-resistant vs. butyrate-sensitive CRC cells. Based upon all of these observations, we hypothesize that colonic neoplastic cells exhibiting a more oncogenic as compared to receptor-mediated Wnt signaling gene expression pattern would be more sensitive to the effects of butyrate, and, hence, fiber, than are those cells exhibiting a more receptor-mediated Wnt signaling pattern of expression. Diet-derived butyrate may affect the differential patient outcomes resulting from the two types of Wnt signaling. We further posit that development of butyrate resistance and concomitant changes in Wnt signaling patterns, including associations with CBP and p300, disrupts the association between the two major types of Wnt signaling (receptor-mediated and oncogenic) and neoplastic progression/prognosis. Ideas about testing the hypothesis and therapeutic implications are briefly considered.

Nonsense-mediated RNA decay: an emerging modulator of malignancy

Nonsense-mediated RNA decay (NMD) is a highly conserved RNA turnover pathway that selectively degrades RNAs harbouring truncating mutations that prematurely terminate translation, including nonsense, frameshift and some splice-site mutations. Recent studies show that NMD shapes the mutational landscape of tumours by selecting for mutations that tend to downregulate the expression of tumour suppressor genes but not oncogenes. This suggests that NMD can benefit tumours, a notion further supported by the finding that mRNAs encoding immunogenic neoantigen peptides are typically targeted for decay by NMD. Together, this raises the possibility that NMD-inhibitory therapy could be of therapeutic benefit against many tumour types, including those with a high load of neoantigen-generating mutations. Complicating this scenario is the evidence that NMD can also be detrimental for many tumour types, and consequently tumours often have perturbed NMD. NMD may suppress tumour generation and progression by degrading subsets of specific normal mRNAs, including those encoding stress-response proteins, signalling factors and other proteins beneficial for tumours, as well as pro-tumour non-coding RNAs. Together, these findings suggest that NMD-modulatory therapy has the potential to provide widespread therapeutic benefit against diverse tumour types. However, whether NMD should be stimulated or repressed requires careful analysis of the tumour to be treated.

The Emerging Roles of Human Gut Microbiota in Gastrointestinal Cancer

The gut microbiota is composed of a large number of microorganisms with a complex structure. It participates in the decomposition, digestion, and absorption of nutrients; promotes the development of the immune system; inhibits the colonization of pathogens; and thus modulates human health. In particular, the relationship between gut microbiota and gastrointestinal tumor progression has attracted widespread concern. It was found that the gut microbiota can influence gastrointestinal tumor progression in independent ways. Here, we focused on the distribution of gut microbiota in gastrointestinal tumors and further elaborated on the impact of gut microbiota metabolites, especially short-chain fatty acids, on colorectal cancer progression. Additionally, the effects of gut microbiota on gastrointestinal tumor therapy are outlined. Finally, we put forward the possible problems in gut microbiota and the gastrointestinal oncology field and the efforts we need to make.

Therapeutic targeting of TANK-binding kinase signaling towards anticancer drug development: Challenges and opportunities

TANK-binding kinase 1 (TBK1) plays a fundamental role in regulating the cellular responses and controlling several signaling cascades. It regulates inflammatory, interferon, NF-κB, autophagy, and Akt pathways. Post-translational modifications (PTM) of TBK1 control its action and subsequent cellular signaling. The dysregulation of the TBK1 pathway is correlated to many pathophysiological conditions, including cancer, that implicates the promising therapeutic advantage for targeting TBK1. The present study summarizes current updates on the molecular mechanisms and cancer-inducing roles of TBK1. Designed inhibitors of TBK1 are considered a potential therapeutic agent for several diseases, including cancer. Data from pre-clinical tumor models recommend that the targeting of TBK1 could be an attractive strategy for anti-tumor therapy. This review further highlighted the therapeutic potential of potent and selective TBK1 inhibitors, including Amlexanox, Compound II, BX795, MRT67307, SR8185 AZ13102909, CYT387, GSK8612, BAY985, and Domainex. These inhibitors may be implicated to facilitate therapeutic management of cancer and TBK1-associated diseases in the future.

Processing body (P-body) and its mediators in cancer

In recent years, processing bodies (P-bodies) formed by liquid-liquid phase separation, have attracted growing scientific attention due to their involvement in numerous cellular activities, including the regulation of mRNAs decay or storage. These cytoplasmic dynamic membraneless granules contain mRNA storage and decay components such as deadenylase and decapping factors. In addition, different mRNA metabolic regulators, including m⁶A readers and gene-mediated miRNA-silencing, are also associated with such P-bodies. Cancerous cells may profit from these mRNA decay shredders by up-regulating the expression level of oncogenes and down-regulating tumor suppressor genes. The main challenges of cancer treatment are drug resistance, metastasis, and cancer relapse likely associated with cancer stem cells, heterogeneity, and plasticity features of different tumors. The mRNA metabolic regulators based on P-bodies play a great role in cancer development and progression. The dysregulation of P-bodies mediators affects mRNA metabolism. However, less is known about the relationship between P-bodies mediators and cancerous behavior. The current review summarizes the recent studies on P-bodies mediators, their contribution to tumor development, and their potential in the clinical setting, particularly highlighting the P-bodies as potential drug-carriers such as exosomes to anticancer in the future.

The potential value of amlexanox in the treatment of cancer: Molecular targets and therapeutic perspectives

Amlexanox (AMX) is an azoxanthone drug used for decades for the treatment of mouth aphthous ulcers and now considered for the treatment of diabetes and obesity. The drug is usually viewed as a dual inhibitor of the non-canonical IκB kinases IKK-ɛ (inhibitor-kappaB kinase epsilon) and TBK1 (TANK-binding kinase 1). But a detailed target profile analysis indicated that AMX binds directly to twelve protein targets, including different enzymes (IKK-ɛ, TBK1, GRK1, GRK5, PDE4B, 5- and 12-lipoxygenases) and non-enzyme proteins (FGF-1, HSP90, S100A4, S100A12, S100A13). AMX has been demonstrated to have marked anticancer effects in multiple models of xenografted tumors in mice, including breast, colon, lung and gastric cancers and in onco-hematological models. The anticancer potency is generally modest but largely enhanced upon combination with cytotoxic (temozolide, docetaxel), targeted (selumetinib) or biotherapeutic agents (anti-PD-1 and anti-CTLA4 antibodies). The multiple targets participate in the anticancer effects, chiefly IKK-ɛ/TBK1 but also S100A proteins and PDE4B. The review presents the molecular basis of the antitumor effects of AMX. The capacity of the drug to block nonsense-mediated mRNA decay (NMD) is also discussed, as well as AMX-induced reduction of cancer-related pain. Altogether, the analysis provides a survey of the anticancer action of AMX, with the implicated protein targets. The use of this well-tolerated drug to treat cancer should be further considered and the design of newer analogues encouraged.

Analysis of the resistance of small peptides from Periplaneta americana to hydrogen peroxide-induced apoptosis in human ovarian granular cells based on RNA-seq

Apoptosis of ovarian granular cells is closely related with weakening fertility of women. Hence, resisting apoptosis of human ovarian granular cells is of important significance. According to previous studies, DAPI fluorescence staining experiment and Western Blot test of Caspase-3 demonstrate that small peptides from Periplaneta americana (SPPA) can improve hydrogen peroxide (H₂O₂) -induced apoptosis of human ovarian granular cells (KGN cells). However, the molecular mechanism of SPPA resistance against apoptosis of granular cells still remains unknown. In this study, key genes and signaling pathways for SPPA to resist H₂O₂-induced apoptosis of KGN cells were determined through transcriptome sequencing (RNA-seq). Experiments were divided into three groups, namely, the control group, H₂O₂ group and H₂O₂ + SPPA group. A total of 1196 differentially expressed genes (DEGs) were screened by comparing the control group and the H₂O₂ group, and 2805 DEGs were screened by comparing the H₂O₂ group and H₂O₂ + SPPA group. It is important to note that 87 overlapping genes were identified upregulating in H₂O₂ exposure, but downregulating in SPPA repair. Another 151 overlapping genes were identified downregulating in H₂O₂ exposure, but upregulating in SPPA repair. These 238 overlapping genes have significant enrichment in multiple KEGG pathways. Among them, 13 genes play significant roles in SPPA resistance process of cell apoptosis: EIF3D, RAN, UPF1 and EIF2B4 participate in RNA transport; ACTG1, SIPA1 and CTNND1 participate in Leukocyte transendothelial migration; S100A7, S100A9, RELA and IL17RE participate in IL-17 signaling pathway; BCL2L13, EIF2AK3 and RELA participate in Mitophapy-animal. Ten genes were selected for florescence quantitative PCR (qPCR) verification and the expression level was consistent with sequencing results. Finally, a control network of SPPA resistance against the H₂O₂-induced KGN cell apoptosis was built based on the target genes screened by the RNA-seq technology. This study provides a direction and some references to further understand the molecular mechanism of SPPA resistance against the H₂O₂-induced KGN cell apoptosis.

A drug screen with approved compounds identifies amlexanox as a novel Wnt/β-catenin activator inducing lung epithelial organoid formation

Background and Purpose:

Emphysema is an incurable disease characterized by loss of lung tissue leading to impaired gas exchange. Wnt/β-catenin signalling is reduced in emphysema, and exogenous activation of the pathway in experimental models in vivo and in human ex vivo lung tissue improves lung function and structure. We sought to identify a pharmaceutical able to activate Wnt/β-catenin signalling and assess its potential to activate lung epithelial cells and repair.

Experimental Approach:

We screened 1216 human-approved compounds for Wnt/β-catenin signalling activation using luciferase reporter cells and selected candidates based on their computationally predicted protein targets. We further performed confirmatory luciferase reporter and metabolic activity assays. Finally, we studied the regenerative potential in murine adult epithelial cell-derived lung organoids and in vivo using a murine elastase-induced emphysema model.

Key Results:

The primary screen identified 16 compounds that significantly induced Wnt/β-catenin-dependent luciferase activity. Selected compounds activated Wnt/β-catenin signalling without inducing cell toxicity or proliferation. Two compounds were able to promote organoid formation, which was reversed by pharmacological Wnt/β-catenin inhibition, confirming the Wnt/β-catenin-dependent mechanism of action. Amlexanox was used for in vivo evaluation, and preventive treatment resulted in improved lung function and structure in emphysematous mouse lungs. Moreover, gene expression of Hgf, an important alveolar repair marker, was increased, whereas disease marker Eln was decreased, indicating that amlexanox induces proregenerative signalling in emphysema.

Conclusion and Implications:

Using a drug screen based on Wnt/β-catenin activity, organoid assays and a murine emphysema model, amlexanox was identified as a novel potential therapeutic agent for emphysema.

Targeting TANK-binding kinase 1 (TBK1) in cancer

INTRODUCTION

TANK-binding kinase 1 (TBK1) is a Ser/Thr kinase with a central role in coordinating the cellular response to invading pathogens and regulating key inflammatory signaling cascades. While intact TBK1 signaling is required for successful anti-viral signaling, dysregulated TBK1 signaling has been linked to a variety of pathophysiologic conditions, including cancer. Several lines of evidence support a role for TBK1 in cancer pathogenesis, but the specific roles and regulation of TBK1 remain incompletely understood. A key challenge is the diversity of cellular processes that are regulated by TBK1, including inflammation, cell cycle, autophagy, energy homeostasis, and cell death. Nevertheless, evidence from pre-clinical cancer models suggests that targeting TBK1 may be an effective strategy for anti-cancer therapy in specific settings.

AREAS COVERED

This review provides an overview of the roles and regulation of TBK1 with a focus on cancer pathogenesis and drug targeting of TBK1 as an anti-cancer strategy. Relevant literature was derived from a PubMed search encompassing studies from 1999 to 2020.

EXPERT OPINION

TBK1 is emerging as a potential target for anti-cancer therapy. Inhibition of TBK1 alone may be insufficient to restrain the growth of most cancers; hence, combination strategies will likely be necessary. Improved understanding of tumor-intrinsic and tumor-extrinsic TBK1 signaling will inform novel therapeutic strategies.

Molecular Characterization and Clinical Relevance of RNA Binding Proteins in Colorectal Cancer

Abnormal expression of RNA binding proteins (RBPs) has been reported across various cancers. However, the potential role of RBPs in colorectal cancer (CRC) remains unclear. In this study, we performed a systematic bioinformatics analysis of RBPs in CRC. We downloaded CRC data from The Cancer Genome Atlas (TCGA) database. Our analysis identified 242 differentially expressed RBPs between tumor and normal tissues, including 200 upregulated and 42 downregulated RBPs. Next, we found eight RBPs (RRS1, PABPC1L, TERT, SMAD6, UPF3B, RP9, NOL3, and PTRH1) related to the prognoses of CRC patients. Among these eight prognosis-related RBPs, four RBPs (NOL3, PTRH1, UPF3B, and SMAD6) were selected to construct a prognostic risk score model. Furthermore, our results indicated that the prognostic risk score model accurately predicted the prognosis of CRC patients [area under the receiver operating characteristic curve (AUC)for 3- and 5-year overall survival (OS) and was 0.645 and 0.672, respectively]. Furthermore, we developed a nomogram based on a prognostic risk score model. The nomogram was able to demonstrate the wonderful performance in predicting 3- and 5-year OS. Additionally, we validated the clinical value of four risk genes in the prognostic risk score model and identified that these risk genes were associated with tumorigenesis, lymph node metastasis, distant metastasis, clinical stage, and prognosis. Finally, we used the TIMER and Human Protein Atlas (HPA)database to validate the expression of four risk genes at the transcriptional and translational levels, respectively, and used a clinical cohort to validate the roles of NOL3 and UPF3B in predicting the prognosis of CRC patients. In summary, our study demonstrated that RBPs have an effect on CRC tumor progression and might be potential prognostic biomarkers for CRC patients.

The C/D box small nucleolar RNA SNORD52 regulated by Upf1 facilitates Hepatocarcinogenesis by stabilizing CDK1

Rationale: Understanding the roles of small nucleolar RNAs (snoRNAs) in hepatocarcinogenesis will provide new avenues to identify diagnostic and therapeutic targets for hepatocellular carcinoma (HCC). Our previous research confirmed the tumor-suppressive effect of Up-frameshift 1 (Upf1) in HCC. Herein, we examined the expression profiles of snoRNAs regulated by Upf1 in hepatoma cells.

Methods: We examined the expression profiles of snoRNAs regulated by Upf1 in hepatoma cells using RNA-sequencing analysis and then investigated the expression and significance of SNORD52 in HCC tissue and different cell lines. The protumorigenic effects of SNORD52 on HCC cells were confirmed both in vitro and in vivo by gain-of-function and loss-of-function assays. RNA pull-down assays and mass spectrometry were used to identify the RNA-binding protein that binds to SNORD52.

Results: Many snoRNAs were identified; one of which, the human C/D box small nucleolar RNA SNORD52, was upregulated in HCC tissues and negatively correlated with Upf1 expression, and patients with higher SNORD52 expression had a poor clinical prognosis. SNORD52 promoted HCC tumorigenesis both in vitro and in vivo. Mechanistically, KEGG analysis showed that SNORD52 upregulated a series of cell cycle genes in HCC cells. We further confirmed that SNORD52 upregulated CDK1 by enhancing the stability of CDK1 proteins and that the function of SNORD52 depends on the presence of CDK1.

Conclusion: Overall, the present study indicates that SNORD52 could be a potential biomarker for HCC. Targeting the Upf1/SNORD52/CDK1 pathway might have therapeutic potential for HCC.

Effects of Intestinal Microbial⁻Elaborated Butyrate on Oncogenic Signaling Pathways

The intestinal microbiota is well known to have multiple benefits on human health, including cancer prevention and treatment. The effects are partially mediated by microbiota-produced short chain fatty acids (SCFAs) such as butyrate, propionate and acetate. The anti-cancer effect of butyrate has been demonstrated in cancer cell cultures and animal models of cancer. Butyrate, as a signaling molecule, has effects on multiple signaling pathways. The most studied effect is its inhibition on histone deacetylase (HDAC), which leads to alterations of several important oncogenic signaling pathways such as JAK2/STAT3, VEGF. Butyrate can interfere with both mitochondrial apoptotic and extrinsic apoptotic pathways. In addition, butyrate also reduces gut inflammation by promoting T-regulatory cell differentiation with decreased activities of the NF-κB and STAT3 pathways. Through PKC and Wnt pathways, butyrate increases cancer cell differentiation. Furthermore, butyrate regulates oncogenic signaling molecules through microRNAs and methylation. Therefore, butyrate has the potential to be incorporated into cancer prevention and treatment regimens. In this review we summarize recent progress in butyrate research and discuss the future development of butyrate as an anti-cancer agent with emphasis on its effects on oncogenic signaling pathways. The low bioavailability of butyrate is a problem, which precludes clinical application. The disadvantage of butyrate for medicinal applications may be overcome by several approaches including nano-delivery, analogue development and combination use with other anti-cancer agents or phytochemicals.