Isoliquiritigenin Inhibits Gastric Cancer Stemness, Modulates Tumor Microenvironment, and Suppresses Tumor Growth through Glucose-Regulated Protein 78 Downregulation

Deciphering drug resistance in gastric cancer: Potential mechanisms and future perspectives

Gastric cancer (GC) is a malignant tumor that originates from the epithelium of the gastric mucosa. The latest global cancer statistics show that GC ranks fifth in incidence and fourth in mortality among all cancers, posing a serious threat to public health. While early-stage GC is primarily treated through surgery, chemotherapy is the frontline option for advanced cases. Currently, commonly used chemotherapy regimens include FOLFOX (oxaliplatin + leucovorin + 5-fluorouracil) and XELOX (oxaliplatin + capecitabine). However, with the widespread use of chemotherapy, an increasing number of cases of drug resistance have emerged. This article primarily explores the potential mechanisms of chemotherapy resistance in GC patients from five perspectives: cell death, tumor microenvironment, non-coding RNA, epigenetics, and epithelial-mesenchymal transition. Additionally, it proposes feasibility strategies to overcome drug resistance from four angles: cancer stem cells, tumor microenvironment, natural products, and combined therapy. The hope is that this article will provide guidance for researchers in the field and bring hope to more GC patients.

Notum enhances gastric cancer stem-like cell properties through upregulation of Sox2 by PI3K/AKT signaling pathway

PURPOSE

Considerable evidence suggests that tumor cells with stemness features contribute to initiation, progression, recurrence of gastric cancer (GC) and resistance to therapy, but involvement of underlying regulators and mechanisms remain largely unclear. However, the clinical significance and biological function of Notum in GC tumor sphere formation and tumorigenesis remain unclear.

METHODS

Bioinformatics analysis, RT-qPCR, western blot and imunohistochemistry staining were applied to characterize Notum expression in GC specimens. The early diagnostic value of Notum was analyzed by logistic regression analysis method. Cancer stemness assays were used in Notum knockdown and overexpressing cells in vitro and in vivo. RNA-seq was employed to reveal the downstream effectors of Notum.

RESULTS

Notum is highly expressed in early stage of GC patients and stem-like GC cells. For discriminating the early-stage and advanced GC patients, the joint analysis had a better diagnostic value. Overexpression of Notum markedly increased stemness features of GC cells to promote tumor sphere formation and tumorigenesis. Conversely, Notum knockdown attenuated the stem-like cell properties in vitro and in vivo. Mechanically, Notum upregulates Sox2 through activating the PI3K/AKT signaling pathway. Notum inhibitor Caffeine exhibited a potent inhibitory effect on stemness features by impairing the PI3K/AKT signaling pathway activity and targeting Sox2.

CONCLUSION

Our findings confer a comprehensive and mechanistic function of Notum in GC tumor sphere formation and tumorigenesis that may provide a novel and promising target for early diagnosis and clinical therapy of GC.

Glucose-Regulated Protein 78 Targeting ICG and DOX Loaded Hollow Fe3O4 Nanoparticles for Hepatocellular Carcinoma Diagnosis and Therapy

Purpose

Liver cancer is considered as the third leading cause of cancer-related deaths, with hepatocellular carcinoma (HCC) accounting for approximately 90% of liver cancers. Improving the treatment of HCC is a serious challenge today. The primary objective of this study was to construct SP94-Fe3O4@ICG&DOX nanoparticles and investigate their potential diagnosis and treatment effect benefits on HCC.

Methods

Firstly, we synthesized and characterized SP94-Fe3O4@ICG&DOX nanoparticles and confirmed their in vitro release behavior, photothermal and photodynamic performance. Moreover, the in vivo imaging capability was also observed. Finally, the inhibitory effects on Hepa1-6 in vitro and in vivo were observed as well as biosafety.

Results

SP94-Fe3O4@ICG&DOX nanoparticles have a size of ~22.1 nm, with an encapsulation efficiency of 45.2% for ICG and 42.7% for DOX, showing excellent in vivo MPI and fluorescence imaging capabilities for precise tumor localization, and synergistic photo-chemotherapy (pH- and thermal-sensitive drug release) against tumors under irradiation. With the assistance of a fluorescence molecular imaging system or MPI scanner, the location and contours of the tumor were clearly visible. Under a constant laser irradiation (808 nm, 0.6 W/cm2) and a set concentration (50 µg/mL), the temperature of the solution could rapidly increase to ~45 °C, which could effectively kill the tumor cells. It could be effectively uptaken by HCC cells and significantly inhibit their proliferation under the laser irradiation (100% inhibition rate for HCC tumors). And most importantly, our nanoparticles exhibited favorable biocompatibility with normal tissues and cells.

Conclusion

This versatile agent can serve as an intelligent and promising nanoplatform that integrates multiple accurate diagnoses, precise positioning of cancer tissue, and effective coordination with synergistic tumor photodynamic therapy.

Isoliquiritigenin inhibits apoptosis and ameliorates oxidative stress in rheumatoid arthritis chondrocytes through the Nrf2/HO-1-mediated pathway

Rheumatoid arthritis (RA) is a chronic inflammatory condition known for its irreversible destructive impact on the joints. Chondrocytes play a pivotal role in the production and maintenance of the cartilage matrix. However, the presence of inflammatory cytokines can hinder chondrocyte proliferation and promote apoptosis. Isoliquiritigenin (ISL), a flavonoid, potentially exerts protective effects against various inflammatory diseases. However, its specific role in regulating the nuclear factor E2-associated factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway in chondrocytes in RA remains unclear. To investigate this, this study used human chondrocytes and Sprague-Dawley rats to construct in vitro and in vivo RA models, respectively. The study findings reveal that cytokines markedly induced oxidative stress, the activation of matrix metalloproteinases, and apoptosis both in vitro and in vivo. Notably, ISL treatment significantly mitigated these effects. Moreover, Nrf2 or HO-1 inhibitors reversed the protective effects of ISL, attenuated the expression of Nrf2/HO-1 and peroxisome proliferator-activated receptor gamma-coactivator-1α, and promoted chondrocyte apoptosis. This finding indicates that ISL primarily targets the Nrf2/HO-1 pathway in RA chondrocytes. Moreover, ISL treatment led to improved behavior scores, reduced paw thickness, and mitigated joint damage as well as ameliorated oxidative stress in skeletal muscles in an RA rat model. In conclusion, this study highlights the pivotal role of the Nrf2/HO-1 pathway in the protective effects of ISL and demonstrates the potential of ISL as a treatment option for RA.

Recent advances in small molecule and peptide inhibitors of glucose-regulated protein 78 for cancer therapy

Glucose-regulated protein 78 (GRP78) is one of key endoplasmic reticulum (ER) chaperone proteins that regulates the unfolded protein response (UPR) to maintain ER homeostasis. As a core factor in the regulation of the UPR, GRP78 takes a critical part in the cellular processes required for tumorigenesis, such as proliferation, metastasis, anti-apoptosis, immune escape and chemoresistance. Overexpression of GRP78 is closely correlated with tumorigenesis and poor prognosis in various malignant tumors. Targeting GRP78 is regarded as a potentially promising therapeutic strategy for cancer therapy. Although none of the GRP78 inhibitors have been approved to date, there have been several studies of GRP78 inhibitors. Herein, we comprehensively review the structure, physiological functions of GRP78 and the recent progress of GRP78 inhibitors, and discuss the structures, in vitro and in vivo efficacies, and merits and demerits of these inhibitors to inspire further research. Additionally, the feasibility of GRP78-targeting proteolysis-targeting chimeras (PROTACs), disrupting GRP78 cochaperone interactions, or covalent inhibition are also discussed as novel strategies for drugs discovery targeting GRP78, with the hope that these strategies can provide new opportunities for targeted GRP78 antitumor therapy.

Isoliquiritigenin inhibits gastric cancer growth through suppressing GLUT4 mediated glucose uptake and inducing PDHK1/PGC-1α mediated energy metabolic collapse

BACKGROUND

Isoliquiritigenin (ISL), a natural flavonoid, has anti-tumor activity. But, the understanding of the impact and molecular mechanism of ISL on the growth of gastric cancer (GC) remains limited.

PURPOSE

The study was to explore the tumor suppressive effect of ISL on GC growth both in vitro and in vivo, meanwhile, clarify its molecular mechanisms.

METHODS

Cell viability was detected by cell counting kit-8 (CCK-8) assay. Apoptotic cells in vitro were monitored by Hoechst 33,342 solution. Protein expression was assessed by Western blot. Reactive oxygen species (ROS) level was evaluated by utilizing 2',7'- dichlorofluorescin diacetate (DCFH-DA). Lactic acid level was detected with L-lactate assay kit. Glucose uptake was monitored with fluorescently tagged glucose 2-[N-(7-nitrobenz-2-oxa-1,3-diaxol-4-yl)amino]-2-deoxyglucose (2-NBDG). Glycolytic proton efflux rate (GlycoPER) was evaluated by glycolytic rate assay kit. Oxygen consumption rate (OCR) was conducted by mito stress test kit. A nude mouse model of gastric cancer cell xenograft was established by subcutaneous injection with MGC803 cells. Pathological changes were evaluated by using H&E staining. Cell apoptosis in vivo was evaluated by terminal deoxy-nucleotide transferase mediated dUTP nick end labeling (TUNEL) assay.

RESULTS

ISL remarkably suppressed GC growth and increased cell apoptosis. It regulated apoptosis-related and metabolism-related protein expression both in vitro and in vivo. ISL blocked glucose uptake and suppressed production and secretion of lactic acid, which was accompanied with suppressed mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis but increased ROS accumulation. Overexpression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), cellular-myelocytomatosis viral oncogene (c-Myc), hypoxia inducible factor-1α (HIF-1α), glucose transporter 4 (GLUT4) or pyruvate dehydrogenase kinase 1 (PDHK1), could abolish ISL-induced inhibition of cell viability in GC cells.

CONCLUSION

These findings implicated that ISL inhibits GC growth by decreasing GLUT4 mediated glucose uptake and inducing PDHK1/PGC-1α-mediated energy metabolic collapse through depressing protein expression of c-Myc and HIF-1α in GC, suggesting its potential application for GC treatment.

The signaling pathways and targets of natural products from traditional Chinese medicine treating gastric cancer provide new candidate therapeutic strategies

Gastric cancer (GC) is one of the severe malignancies with high incidence and mortality, especially in Eastern Asian countries. Significant advancements have been made in diagnosing and treating GC over the past few decades, resulting in tremendous improvements in patient survival. In recent years, traditional Chinese medicine (TCM) has garnered considerable attention as an alternative therapeutic approach for GC due to its multicomponent and multitarget characteristics. Consequently, natural products found in TCM have attracted researchers' attention, as growing evidence suggests that these natural products can impede GC progression by regulating various biological processes. Nevertheless, their molecular mechanisms are not systematically uncovered. Here, we review the major signaling pathways involved in GC development. Additionally, clinical GC samples were analyzed. Moreover, the anti-GC effects of natural products, their underlying mechanisms and potential targets were summarized. These summaries are intended to facilitate further relevant research, and accelerate the clinical applications of natural products in GC treatment.

Pharmacological Mechanisms and Adjuvant Properties of Licorice Glycyrrhiza in Treating Gastric Cancer

Licorice is a remarkable traditional Chinese medicine obtained from the dried root and rhizomes of the Glycyrrhiza genus, and t has been utilized in China for many centuries. It consists of more than 300 compounds that are mainly divided into triterpene saponins, flavonoids, polysaccharides, and phenolic components. The active compounds of licorice have been found to possess multiple biological activities, including antitumor, anti-inflammatory, antiviral, antimicrobial, immunoregulatory, cardioprotective, and neuroprotective functions. In addition to providing a brief overview of licorice's adjuvant properties, this review describes and analyzes the pharmacological mechanisms by which licorice components function to treat gastric cancer. Furthermore, licorice compounds are also found to be potent adjuvant chemotherapy agents, as they can improve the quality of life of cancer patients and alleviate chemotherapy-induced adverse effects.

Betulinic Acid Inhibits the Stemness of Gastric Cancer Cells by Regulating the GRP78-TGF-β1 Signaling Pathway and Macrophage Polarization

Cancer stemness is the process by which cancer cells acquire chemoresistance and self-renewal in the tumor microenvironment. Glucose-regulated protein 78 (GRP78) is a biomarker for gastric cancer and is involved in cancer stemness. By inducing cancer stemness in various types of cancer, the polarization of macrophages into tumor-associated macrophages (TAMs) controls tumor progression. Betulinic acid (BA) is a bioactive natural compound with anticancer properties. However, whether GRP78 regulates TAM-mediated cancer stemness in the tumor microenvironment and whether BA inhibits GRP78-mediated cancer stemness in gastric cancer remain unknown. In this study, we investigated the role of GRP78 in gastric cancer stemness in a tumor microenvironment regulated by BA. The results indicated that BA inhibited not only GRP78-mediated stemness-related protein expression and GRP78-TGF-β-mediated macrophage polarization into TAMs, but also TAM-mediated cancer stemness. Therefore, BA is a promising candidate for clinical application in combination-chemotherapy targeting cancer stemness.

Gastric Cancer Cell-Derived Exosomal GRP78 Enhances Angiogenesis upon Stimulation of Vascular Endothelial Cells

Exosomes containing glucose-regulated protein 78 (GRP78) are involved in cancer malignancy. GRP78 is thought to promote the tumor microenvironment, leading to angiogenesis. No direct evidence for this role has been reported, however, mainly because of difficulties in accurately measuring the GRP78 concentration in the exosomes. Recently, exosomal GRP78 concentrations were successfully measured using an ultrasensitive ELISA. In the present study, GRP78 concentrations in exosomes collected from gastric cancer AGS cells with overexpression of GRP78 (OE), knockdown of GRP78 (KD), or mock GRP78 (mock) were quantified. These three types of exosomes were then incubated with vascular endothelial cells to examine their effects on endothelial cell angiogenesis. Based on the results of a tube formation assay, GRP78-OE exosomes accelerated angiogenesis compared with GRP78-KD or GRP78-mock exosomes. To investigate the mechanisms underlying this effect, we examined the Ser473 phosphorylation state ratio of AKT, which is involved in the angiogenesis process, and found that AKT phosphorylation was increased by GRP78-OE exosome application to the endothelial cells. An MTT assay showed that GRP78-OE exosome treatment increased the proliferation rate of endothelial cells, and a wound healing assay showed that this treatment increased the migration capacity of the endothelial cells. These findings demonstrated that GRP78-containing exosomes promote the tumor microenvironment and induce angiogenesis.

Targeting Gastric Cancer Stem Cells to Enhance Treatment Response

Gastric cancer (GC) was the fourth deadliest cancer in the world in 2020, and about 770,000 people died from GC that year. The death of patients with GC is mainly caused by the metastasis, recurrence, and chemotherapy resistance of GC cells. The cancer stem cell theory defines cancer stem cells (CSCs) as a key factor in the metastasis, recurrence, and chemotherapy resistance of cancer. It considers targeting gastric cancer stem cells (GCSCs) to be an effective method for the treatment of GC. For GCSCs, genes or noncoding RNAs are important regulatory factors. Many experimental studies have found that some drugs can target the stemness of gastric cancer by regulating these genes or noncoding RNAs, which may bring new directions for the clinical treatment of gastric cancer. Therefore, this review mainly discusses related genes or noncoding RNAs in GCSCs and drugs that target its stemness, thereby providing some information for the treatment of GC.

Ultrasensitive Detection of GRP78 in Exosomes and Observation of Migration and Proliferation of Cancer Cells by Application of GRP78-Containing Exosomes

Simple Summary

Cancer cells release exosomes to their surrounding cells, and it is believed that trace amounts of proteins included in exosomes promote cancer stemness. In the present study, we note 78-kDa glucose-regulated protein (GRP78), which is involved in cancer progression, and present the protocol for measurements of trace amounts of GRP78 in exosomes released from cultured gastric cancer cells using an ultrasensitive ELISA with thio-NAD cycling. We found that when high-GRP78-containing exosomes were incubated with cultured cancer cells, these cells increased their stemness, for example, an increase in indices of both an MTT assay and a wound healing assay. The technique for quantifying proteins in exosomes described here will advance our understanding of cancer stemness progression via exosomes.

Abstract

Cancer cells communicate with each other via exosomes in the tumor microenvironment. However, measuring trace amounts of proteins in exosomes is difficult, and thus the cancer stemness-promoting mechanisms of exosomal proteins have not been elucidated. In the present study, we attempted to quantify trace amounts of 78-kDa glucose-regulated protein (GRP78), which is involved in cancer progression, in exosomes released from cultured gastric cancer cells using an ultrasensitive ELISA combined with thio-NAD cycling. We also evaluated the cancer stemness-promoting effects by the application of high-GRP78-containing exosomes to cultured gastric cancer cells. The ultrasensitive ELISA enabled the detection of GRP78 at a limit of detection of 0.16 pg/mL. The stemness of cancer cultured cells incubated with high-GRP78-containing exosomes obtained from GRP78-overexpressed cells was increased on the basis of both an MTT assay and a wound healing assay. Our results demonstrated that the ultrasensitive ELISA has strong potential to measure trace amounts of proteins in exosomes. Further, exosomes with a high concentration of GRP78 promote the cancer stemness of surrounding cells. The technique for quantifying proteins in exosomes described here will advance our understanding of cancer stemness progression via exosomes.

Isoliquiritigenin Nanoemulsion Preparation by Combined Sonication and Phase-Inversion Composition Method: In Vitro Anticancer Activities

Isoliquiritigenin (ILQ) has a number of biological activities such as antitumor and anti-inflammatory effects. However, biomedical applications of ILQ are impeded by its poor aqueous solubility. Therefore, in this research, we prepared a novel ILQ-loaded nanoemulsion, i.e., ILQ-NE, which consisted of Labrafil® M 1944 CS (oil), Cremophor® EL (surfactant), ILQ, and phosphate-buffered saline, by employing a combined sonication (high-energy) and phase-inversion composition (low-energy) method (denoted as the SPIC method). The ILQ-NE increased the ILQ solubility ~1000 times more than its intrinsic solubility. It contained spherical droplets with a mean diameter of 44.10 ± 0.28 nm and a narrow size distribution. The ILQ loading capacity was 4%. The droplet size of ILQ-NE remained unchanged during storage at 4 °C for 56 days. Nanoemulsion encapsulation effectively prevented ILQ from degradation under ultraviolet light irradiation, and enhanced the ILQ in vitro release rate. In addition, ILQ-NE showed higher cellular uptake and superior cytotoxicity to 4T1 cancer cells compared with free ILQ formulations. In conclusion, ILQ-NE may facilitate the biomedical application of ILQ, and the SPIC method presents an attractive avenue for bridging the merits and eliminating the shortcomings of traditional high-energy methods and low-energy methods.