Targeting XBP1-mediated β-catenin expression associated with bladder cancer with newly synthetic Oridonin analogues

Correlation Between Low Cytoplasmic Expression of XBP1 and the Likelihood of Surviving Hepatocellular Carcinoma

BACKGROUND/AIM

Our objectives in this study were to (i) evaluate the clinical significance of X-box-binding protein 1 (XBP1) expression in cases of hepatocellular carcinoma (HCC) and (ii) assess the potential of XBP1 to be used as a prognostic biomarker.

PATIENTS AND METHODS

The expression of XBP1 protein in 267 HCC tissue specimens was measured using immunohistochemistry in order to characterize the associations among XBP1 expression, clinicopathological factors and survival outcomes. Survival analysis using follow-up data was used to assess the prognostic value of XBP1 in cases of HCC. Immunohistochemistry revealed a significant decrease in cytoplasmic XBP1 protein expression in HCC tumor tissue.

RESULTS

Immunoreactivity results showed that low cytoplasmic XBP1 expression was significantly associated with vascular invasion, as well as poor 5-year overall survival and long-term disease-specific (DSS) and disease-free (DFS) survival rates. Kaplan-Meier survival curves further confirmed a significant association between low cytoplasmic XBP1 protein expression and poor DSS and DFS. Univariate and multivariate analyses revealed that XBP1 expression, tumor differentiation, vascular invasion, tumor stage, and the rate of recurrence were linked to DSS, while low cytoplasmic XBP1 expression remained an independent predictor of poor DSS. Our analysis also revealed that XBP1 expression, tumor differentiation, vascular invasion, and T classification were linked to DFS, while low cytoplasmic XBP1 expression remained an independent predictor of poor DFS.

CONCLUSION

Low cytoplasmic XBP1 protein expression may play an important role in the pathogenesis of HCC, which suggests that XBP1 could potentially be targeted to benefit therapeutic strategies for HCC.

Anticancer mechanisms on pyroptosis induced by Oridonin: New potential targeted therapeutic strategies

Pyroptosis is a type of inflammatory cell death that is triggered by the formation of pores on the cell membrane by gasdermin (GSDM) family proteins. This process activates inflammasomes and leads to the maturation and release of proinflammatory cytokines such as interleukin-1β (IL-1β) and interleukin-18 (IL-18). Pyroptosis, a form of programmed cell death, has been found to be associated with various biomolecules such as caspases, granzymes, non-coding RNA (lncRNA), reactive oxygen species (ROS), and NOD-like receptor protein 3 (NLRP3). These biomolecules have been shown to play a dual role in cancer by affecting cell proliferation, metastasis, and the tumor microenvironment (TME), resulting in both tumor promotion and anti-tumor effects. Recent studies have found that Oridonin (Ori) has anti-tumor effects by regulating pyroptosis through various pathways. Ori can inhibit pyroptosis by inhibiting caspase-1, which is responsible for activating pyroptosis of the canonical pathway. Additionally, Ori can inhibit pyroptosis by inhibiting NLRP3, which is responsible for activating pyroptosis of the noncanonical pathway. Interestingly, Ori can also activate pyroptosis by activating caspase-3 and caspase-8, which are responsible for activating pyroptosis of the emerging pathway; Ori has been found to be effective in inhibiting pyroptosis by blocking the action of perforin, which is responsible for facilitating the entry of granzyme into cells and activating pyroptosis. Additionally, Ori plays a crucial role in regulating pyroptosis by promoting the accumulation of ROS while inhibiting the ncRNA and NLRP3 pathways. It is worth noting that all of these pathways ultimately regulate pyroptosis by influencing the cleavage of GSDM, which is a key factor in the process. These studies concludes that Ori has extensive anti-cancer effects that are related to its potential regulatory function on pyroptosis. The paper summarizes several potential ways in which Ori participates in the regulation of pyroptosis, providing a reference for further study on the relationship between Ori, pyroptosis, and cancer.

Comprehensive characterization of endoplasmic reticulum stress in bladder cancer revealing the association with tumor immune microenvironment and prognosis

Background: This study constructs a molecular subtype and prognostic model of bladder cancer (BLCA) through endoplasmic reticulum stress (ERS) related genes, thus helping to clinically guide accurate treatment and prognostic assessment. Methods: The Bladder Cancer (BLCA) gene expression data was downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. We clustered by ERS-related genes which obtained through GeneCards database, results in the establishment of a new molecular typing of bladder cancer. Further, we explored the characteristics of each typology in terms of immune microenvironment, mutations, and drug screening. By analyzing the ERS-related genes with univariate Cox, LASSO and multivariate Cox analyses, we also developed the four-gene signature, while validating the prognostic effect of the model in GSE32894 and GSE13507 cohorts. Finally, we evaluated the prognostic value of the clinical data in the high and low ERS score groups and constructed a prognostic score line graph by Nomogram. Results: We constructed four molecular subtypes (C1- C4) of bladder cancer, in which patients with C2 had a poor prognosis and those with C3 had a better prognosis. The C2 had a high degree of TP53 mutation, significant immune cell infiltration and high immune score. In contrast, C3 had a high degree of FGFR3 mutation, insignificant immune cell infiltration, and reduced immune checkpoint expression. After that, we built ERS-related risk signature to calculate ERS score, including ATP2A3, STIM2, VWF and P4HB. In the GSE32894 and GSE13507, the signature also had good predictive value for prognosis. In addition, ERS scores were shown to correlate well with various clinical features. Finally, we correlated the ERS clusters and ERS score. Patients with high ERS score were more likely to have the C2 phenotype, while patients with low ERS score were C3. Conclusion: In summary, we identified four novel molecular subtypes of BLCA by ERS-related genes which could provide some new insights into precision medicine. Prognostic models constructed from ERS-related genes can be used to predict clinical outcomes. Our study contributes to the study of personalized treatment and mechanisms of BLCA.

Spliced or Unspliced, That Is the Question: The Biological Roles of XBP1 Isoforms in Pathophysiology

X-box binding protein 1 (XBP1) is a member of the CREB/ATF basic region leucine zipper family transcribed as the unspliced isoform (XBP1-u), which, upon exposure to endoplasmic reticulum stress, is spliced into its spliced isoform (XBP1-s). XBP1-s interacts with the cAMP response element of major histocompatibility complex class II gene and plays critical role in unfolded protein response (UPR) by regulating the transcriptional activity of genes involved in UPR. XBP1-s is also involved in other physiological pathways, including lipid metabolism, insulin metabolism, and differentiation of immune cells. Its aberrant expression is closely related to inflammation, neurodegenerative disease, viral infection, and is crucial for promoting tumor progression and drug resistance. Meanwhile, recent studies reported that the function of XBP1-u has been underestimated, as it is not merely a precursor of XBP1-s. Instead, XBP-1u is a critical factor involved in various biological pathways including autophagy and tumorigenesis through post-translational regulation. Herein, we summarize recent research on the biological functions of both XBP1-u and XBP1-s, as well as their relation to diseases.

Silencing circ‑BIRC6 inhibits the proliferation, invasion, migration and epithelial‑mesenchymal transition of bladder cancer cells by targeting the miR‑495‑3p/XBP1 signaling axis

Circular RNAs (circRNAs) regulate gene expression by acting as a 'sponge' for microRNAs (miRs) and play crucial roles in tumorigenesis, including in bladder cancer (BC). circRNA‑baculoviral IAP repeat‑containing 6 (circ‑BIRC6) has been reported to participate in the pathogenesis of several cancer types. The present study aimed to elucidate the roles and potential mechanisms of circ‑BIRC6 in the progression of BC. circ‑BIRC6 expression levels in BC cell lines were determined using reverse transcription‑quantitative PCR. Following circ‑BIRC6 knockdown, cell proliferation, invasion and migration were detected using Cell Counting Kit‑8, colony formation, Transwell and wound healing assays, respectively. Western blotting was also conducted to evaluate the expression levels of X‑box binding protein 1 (XBP1) and epithelial‑mesenchymal transition (EMT)‑associated proteins. In addition, rescue experiments were performed using by transfecting a miR‑495‑3p inhibitor into T24 cells following circ‑BIRC6 knockdown. The interactions between circ‑BIRC6, miR‑495‑3p and XBP1 was verified using dual luciferase reporter assays. Moreover, T24 cells with circ‑BIRC6 knockdown and miR‑495‑3p inhibitor transfection were used for the tumor‑bearing experiment. Tumor growth was observed and Ki‑67 expression was determined using immunohistochemistry. The results demonstrated that circ‑BIRC6 expression was upregulated in BC cell lines. Moreover, circ‑BIRC6 knockdown notably attenuated the proliferation, invasion, migration and EMT of BC cells, which was blocked by the miR‑495‑3p inhibitor. It was also identified that circ‑BIRC6 sponged miR‑495‑3p to regulate XBP1 expression. In addition, results from the xenograft experiments indicated that the knockdown of circ‑BIRC6 and miR‑495‑3p expression significantly inhibited tumor growth. It was also found that the expression levels of XBP1, Ki‑67 and EMT‑associated proteins in tumor tissues of the co‑transfection group were markedly restored compared with the circ‑BIRC6 knockdown group. In conclusion, these findings demonstrated that circ‑BIRC6 knockdown suppressed BC tumorigenesis and progression via regulation of the miR‑495‑3p/XBP1 signaling axis, offering a promising therapeutic target for the treatment of BC.

Endoplasmic Reticulum Stress and Tumor Microenvironment in Bladder Cancer: The Missing Link

Bladder cancer is a common malignant tumor of the urinary system. Despite recent advances in treatments such as local or systemic immunotherapy, chemotherapy, and radiotherapy, the high metastasis and recurrence rates, especially in muscle-invasive bladder cancer (MIBC), have led to the evaluation of more targeted and personalized approaches. A fundamental understanding of the tumorigenesis of bladder cancer along with the development of therapeutics to target processes and pathways implicated in bladder cancer has provided new avenues for the management of this disease. Accumulating evidence supports that the tumor microenvironment (TME) can be shaped by and reciprocally act on tumor cells, which reprograms and regulates tumor development, metastasis, and therapeutic responses. A hostile TME, caused by intrinsic tumor attributes (e.g., hypoxia, oxidative stress, and nutrient deprivation) or external stressors (e.g., chemotherapy and radiation), disrupts the normal synthesis and folding process of proteins in the endoplasmic reticulum (ER), culminating in a harmful situation called ER stress (ERS). ERS is a series of adaptive changes mediated by unfolded protein response (UPR), which is interwoven into a network that can ultimately mediate cell proliferation, apoptosis, and autophagy, thereby endowing tumor cells with more aggressive behaviors. Moreover, recent studies revealed that ERS could also impede the efficacy of anti-cancer treatment including immunotherapy by manipulating the TME. In this review, we discuss the relationship among bladder cancer, ERS, and TME; summarize the current research progress and challenges in overcoming therapeutic resistance; and explore the concept of targeting ERS to improve bladder cancer treatment outcomes.

Oridonin and its derivatives for cancer treatment and overcoming therapeutic resistance

Cancer is one of the diseases with high morbidity and mortality on a global scale. Chemotherapy remains the primary treatment option for most cancer patients, including patients with progressive, metastatic, and recurrent diseases. To date, hundreds of chemotherapy drugs are used to treat various cancers, however, the anti-cancer efficacy and outcomes are largely hampered by chemotherapy-associated toxicity and acquired therapeutic resistance. The natural product (NP) oridonin has been extensively studied for its anti-cancer efficacy. More recently, oridonin has been shown to overcome drug resistance through multiple mechanisms, with yet-to-be-defined bona fide targets. Hundreds of oridonin derivative analogs (oridonalogs) have been synthesized and screened for improved potency, bioavailability, and other drug properties. Particularly, many of these oridonalogs have been tested against oridonin for tumor growth inhibition, potential for overcoming therapeutic resistance, and immunity modulation. This concise review seeks to summarize the advances in this field in light of identifying clinical-trial level drug candidates with the promise for treating progressive cancers and reversing chemoresistance.

The emerging role of XBP1 in cancer

X-box binding protein 1 (XBP1) is a unique basic-region leucine zipper (bZIP) transcription factor whose dynamic form is controlled by an alternative splicing response upon disturbance of homeostasis in the endoplasmic reticulum (ER) and activation of the unfolded protein response (UPR). XBP1 was first distinguished as a key regulator of major histocompatibility complex (MHC) class II gene expression in B cells. XBP1 communicates with the foremost conserved signalling component of the UPR and is essential for cell fate determination in response to ER stress (ERS). Here, we review recent advances in our understanding of this multifaceted translation component in cancer. In this review, we briefly discuss the role of XBP1 mediators in the UPR and the transcriptional function of XBP1. In addition, we describe how XBP1 operates as a key factor in tumour progression and metastasis. We mainly review XBP1's expression, function and prognostic value in research on solid tumours. Finally, we discuss multiple approaches, especially those involving XBP1, that overcome the immunosuppressive effect of the UPR in cancer that could potentially be useful as antitumour therapies.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

WNT/β-catenin signaling in urothelial carcinoma of bladder

Urothelial carcinoma of bladder is the second most prevalent genitourinary disease. It is a highly heterogeneous disease as it represents a spectrum of neoplasms, including non-muscle invasive bladder cancer (NMIBC), muscle invasive bladder cancer (MIBC) and metastatic lesions. Genome-wide approaches and candidate gene analysis suggest that malignant transformation of the bladder is multifactorial and a multitude of genes are involved in the development of MIBC or NMIBC phenotypes. Wnt signaling is being examined to control and maintain balance between stemness and differentiation in adult stem cell niches. Owing to its participation in urothelial development and maintenance of adult urothelial tissue homeostasis, the components of Wnt signaling are reported as an important diagnostic and prognostic markers as well as novel therapeutic targets. Mutations/epigenetic alterations in the key molecules of Wnt/β-catenin canonical pathway have been linked with tumorigenesis, development of drug resistance and enhanced survival. Present review extends our understanding on the functions of key regulatory molecules of canonical Wnt/β-catenin pathway in urothelial tumorigenesis by inducing cancer stem cell phenotype (UCSCs). UCSCs may be responsible for tumor heterogeneity, high recurrence rates and complex biological behavior of bladder cancer. Therefore, understanding the role of UCSCs and the regulatory mechanisms that are responsible for high relapse rates and metastasis could help to develop pathway inhibitors and augment current therapies. Potential implications in the treatment of urothelial carcinoma of bladder by targeting this pathway primarily in UCSCs as well as in bulk tumor population that are responsible for high relapse rates and metastasis may facilitate potential therapeutic avenues and better prognosis.

Unravel the molecular mechanism of XBP1 in regulating the biology of cancer cells

Cancer cells are usually exposed to stressful environments, such as hypoxia, nutrient deprivation, and other metabolic dysfunctional regulation, leading to continuous endoplasmic reticulum (ER) stress. As the most conserved branch among the three un-folded protein response (UPR) pathways, Inositol-requiring enzyme 1α (IRE1α)-X-box-binding protein 1 (XBP1) signaling has been implicated in cancer development and progression. Active XBP1 with transactivation domain functions as a transcription factor to regulate the expression of downstream target genes, including many oncogenic factors. The regulatory activity of XBP1 in cell proliferation, apoptosis, metastasis, and drug resistance promotes cell survival, leading to tumorigenesis and tumor progression. In addition, the XBP1 peptides-based vaccination and/or combination with immune-modulatory drug administration have been developed for effective management for several cancers. Potentially, XBP1 is the biomarker of cancer development and progression and the strategy for clinical cancer management.

Bioactive Natural Spirolactone-Type 6,7-seco-ent-Kaurane Diterpenoids and Synthetic Derivatives

Diterpenoids are widely distributed natural products and have caused considerable interest because of their unique skeletons and antibacterial and antitumor activities and so on. In light of recent discoveries, ent-kaurane diterpenoids, which exhibit a wide variety of biological activities, such as anticancer and anti-inflammatory activities, pose enormous potential to serve as a promising candidate for drug development. Among them, spirolactone-type 6,7-seco-ent-kaurane diterpenoids, with interesting molecular skeleton, complex oxidation patterns, and bond formation, exhibit attractive activities. Furthermore, spirolactone-type diterpenoids have many modifiable sites, which allows for linking to various substituents, suitable for further medicinal study. Hence, some structurally modified derivatives with improved cytotoxicity activities are also achieved. In this review, natural bioactive spirolactone-type diterpenoids and their synthetic derivatives were summarized.

Regio- and Stereospecific Synthesis of Oridonin D-Ring Aziridinated Analogues for the Treatment of Triple-Negative Breast Cancer via Mediated Irreversible Covalent Warheads

Covalent drug discovery has undergone a resurgence in recent years due to comprehensive optimization of the structure-activity relationship (SAR) and the structure-reactivity relationship (SRR) for covalent drug candidates. The natural product oridonin maintains an impressive pharmacological profile through its covalent enone warhead on the D-ring and has attracted substantial SAR studies to characterize its potential in the development of new molecular entities for the treatment of various human cancers and inflammation. Herein, for the first time, we report the excessive reactivity of this covalent warhead and mediation of the covalent binding capability through a Rh₂(esp)₂-catalyzed mild and concise regio- and stereospecific aziridination approach. Importantly, aziridonin 44 (YD0514), with a more-druglike irreversible covalent warhead, has been identified to significantly induce apoptosis and inhibit colony formation against triple-negative breast cancer with enhanced antitumor effects in vitro and in vivo while displaying lower toxicity to normal human mammary epithelial cells in comparison to oridonin.

Induction of the mitochondria-mediated apoptosis in human esophageal cancer cells by DS2, a newly synthetic diterpenoid analog, is regulated by Bax and caused by generation of reactive oxygen species

Ent-kaurane diterpene compounds have attracted considerable attention in recent years due to its antitumor, antibacterial, and antiviral activities. However, the clinical development of natural kaurane diterpenes, for example, oridonin for cancer therapy has been hampered by its relatively moderate potency, limited bioavailability. Herein, we report a newly synthetic analog of natural ent-kaurane diterpene, DS2, which exhibits significantly improved activity of antiproliferation against various cancer cell lines relative to oridonin. DS2 treatment triggers the mitochondria-mediated apoptosis and cell cycle arrest in human esophageal cancer cell lines (EC9706, EC109). Interestingly, normal human esophageal epithelial cells (HEECs) and normal human liver cells (HL-7702) are both significantly more resistant to the growth inhibition by DS2 compared with esophageal cancer cells. The DS2-induced apoptosis in EC9706 cells correlated with the drop of mitochondrial membrane potential (MMP), release of cytochrome c into the cytosol and activation of caspase-9 and -3. The induction of proapoptotic proteins p21 and Bax were also observed in DS2-treated cells. The DS2-induced apoptosis was significantly attenuated by knockdown of Bax proteins. Meanwhile, the DS2 treatment caused generation of reactive oxygen species (ROS) in human esophageal cancer cells, but not in HEECs, which was attenuated by pretreatment with ROS scavenger N-acetylcysteine (NAC). More interestingly, the antioxidants pretreatment completely attenuated DS2 mediated loss of the MMP and apoptosis, as well as Bax expression and growth inhibition. In conclusion, the present study reveals that the mitochondria-mediated cell death by DS2 is associated with Bax regulation and ROS generation, and understanding the function and mechanism of DS2 will help us to design better anti-cancer drugs.

Therapeutic Potential of Oridonin and Its Analogs: From Anticancer and Antiinflammation to Neuroprotection

Oridonin, a diterpenoid natural product commonly used in East Asian herbal medicine, is garnering increased attention in the biomedical community due to its extensive biological activities that include antitumor, anti-inflammatory, antimicrobial, hepatic fibrosis prevention, and neurological effects. Over the past decade, significant progress has been made in structure activity relationship and mechanism of action studies of oridonin for the treatment of cancer and other diseases. This review provides a brief summary on oridonin and its analogs in cancer drug discovery and antiinflammation and highlights its emerging therapeutic potential in neuroprotection applications.

Expression of miR-149-3p inhibits proliferation, migration, and invasion of bladder cancer by targeting S100A4

MicroRNAs play key roles during various crucial cell processes, such as proliferation, migration, and invasion. In addition, microRNAs have been shown to possess oncogenic and tumor suppressive functions in human cancers. Increasing evidence has clarified that miR-149-3p, a novel cancer-related microRNA, plays an important role in suppression of proliferation, migration, and invasion; however, the effect and mechanisms underlying the miR-149-3p effect in bladder cancer (BCa) remain unclear. In the current study we found that the increased expression of miR-149-3p significantly suppressed cell proliferation, migration, and invasion ability in BCa. The suppressive effect was related to S100A4. A further investigation showed that miR-149-3p negatively regulated S100A4, as verified by the luciferase reporter assay. Furthermore, our study showed that S100A4 mediated the anti-metastatic effects of miR-149-3p on proliferation, migration, and invasion of BCa cells. Analysis of a xenograft mouse model showed that miR-149-3p expression significantly decreased tumor growth by targeting S100A4. Taken together, these data indicate that S100A4 promotes cell growth, migration, and invasion and can by reversed by miR-149-3p in BCa.

6,7-Seco-ent-Kauranoids Derived from Oridonin as Potential Anticancer Agents

Structurally unique 6,7-seco-ent-kaurenes, which are widely distributed in the genus Isodon, have attracted considerable attention because of their antitumor activities. Previously, a convenient conversion of commercially available oridonin (1) to 6,7-seco-ent-kaurenes was developed. Herein, several novel spiro-lactone-type ent-kaurene derivatives bearing various substituents at the C-1 and C-14 positions were further designed and synthesized from the natural product oridonin. Moreover, a number of seven-membered C-ring-expanded 6,7-seco-ent-kaurenes were also identified for the first time. It was observed that most of the spiro-lactone-type ent-kaurenes tested markedly inhibited the proliferation of cancer cells, with an IC₅₀ value as low as 0.55 μM. An investigation on its mechanism of action showed that the representative compound 7b affected the cell cycle and induced apoptosis at a low micromolar level in MCF-7 human breast cancer cells. Furthermore, compound 7b inhibited liver tumor growth in an in vivo mouse model and exhibited no observable toxic effects. Collectively, the results warrant further preclinical investigations of these spiro-lactone-type ent-kaurenes as potential novel anticancer agents.

Discovery and development of natural product oridonin-inspired anticancer agents

Natural products have historically been, and continue to be, an invaluable source for the discovery of various therapeutic agents. Oridonin, a natural diterpenoid widely applied in traditional Chinese medicines, exhibits a broad range of biological effects including anticancer and anti-inflammatory activities. To further improve its potency, aqueous solubility and bioavailability, the oridonin template serves as an exciting platform for drug discovery to yield better candidates with unique targets and enhanced drug properties. A number of oridonin derivatives (e.g. HAO472) have been designed and synthesized, and have contributed to substantial progress in the identification of new agents and relevant molecular mechanistic studies toward the treatment of human cancers and other diseases. This review summarizes the recent advances in medicinal chemistry on the explorations of novel oridonin analogues as potential anticancer therapeutics, and provides a detailed discussion of future directions for the development and progression of this class of molecules into the clinic.