Licochalcone A Suppresses the Proliferation of Osteosarcoma Cells through Autophagy and ATM-Chk2 Activation

Autophagy Modulation as a Potential Therapeutic Strategy in Osteosarcoma: Current Insights and Future Perspectives

Autophagy, the process that enables the recycling and degradation of cellular components, is essential for homeostasis, which occurs in response to various types of stress. Autophagy plays an important role in the genesis and evolution of osteosarcoma (OS). The conventional treatment of OS has limitations and is not always effective at controlling the disease. Therefore, numerous researchers have analyzed how controlling autophagy could be used as a treatment or strategy to reverse resistance to therapy in OS. They highlight how the inhibition of autophagy improves the efficacy of chemotherapeutic treatments and how the promotion of autophagy could prove positive in OS therapy. The modulation of autophagy can also be directed against OS stem cells, improving treatment efficacy and preventing cancer recurrence. Despite promising findings, future studies are needed to elucidate the molecular mechanisms of autophagy and its relationship to OS, as well as the mechanisms underlying the functioning of autophagic modulators. Careful evaluation is required as autophagy modulation may have adverse effects on normal cells, and the optimization of autophagic modulators for use as drugs in OS is imperative.

Oxidative stress, free radicals and antioxidants: potential crosstalk in the pathophysiology of human diseases

Introduction: Free radicals are reactive oxygen species that constantly circulate through the body and occur as a side effect of many reactions that take place in the human body. Under normal conditions, they are removed from the body by antioxidant processes. If these natural mechanisms are disrupted, radicals accumulate in excess and contribute to the development of many diseases. Methodology: Relevant recent information on oxidative stress, free radicals, reactive oxidative species, and natural and synthetic antioxidants was collected by researching electronic databases such as PubMed / Medline, Web of Science, and Science Direct. Results: According to the analysed studies, this comprehensive review provided a recent update on oxidative stress, free radicals and antioxidants and their impact on the pathophysiology of human diseases. Discussion: To counteract the condition of oxidative stress, synthetic antioxidants must be provided from external sources to supplement the antioxidant defense mechanism internally. Because of their therapeutic potential and natural origin, medicinal plants have been reported as the main source of natural antioxidants phytocompounds. Some non-enzymatic phytocompounds such as flavonoids, polyphenols, and glutathione, along with some vitamins have been reported to possess strong antioxidant activities in vivo and in vitro studies. Thus, the present review describes, in brief, the overview of oxidative stress-directed cellular damage and the unction of dietary antioxidants in the management of different diseases. The therapeutic limitations in correlating the antioxidant activity of foods to human health were also discussed.

Acute generation of reactive oxygen species that induced by doxycycline pretreatment results in rapid cell death in polyphyllin G-treated osteosarcoma cell lines

Polyphyllin G, a pennogenyl saponin extracted from Paris polyphylla, has been shown to possess antitumor effects. In this study, we demonstrated that doxycycline, an antibiotic medicine, could significantly enhance the sensitivities of osteosarcoma cell lines to polyphyllin G. As the cells were pretreated with doxycycline at non-toxic concentrations and then co-exposed to polyphyllin G, this combination could induce a rapid cell death distinct from apoptosis. The non-apoptotic cell death was characterized by a loss of integrity of plasma membrane without externalization of phosphatidyl serine. Furthermore, this combined treatment resulted in suppression of cell viability and colony-forming ability, and increased the level of γ-H2A.X, a critical marker for DNA damage, in osteosarcoma cell lines. When examining the underlying mechanism, it was revealed combination of polyphyllin G and doxycycline triggered an enhanced generation of reactive oxygen species (ROS), and up-regulated mitochondrial oxidative stress within 0.5 h. Co-administration of the ROS inhibitor NAC reversed the suppressed cell viability and colony-forming ability, and abolished the increased level of γ-H2A.X in the cells with the combined treatment, indicating that the enhanced ROS was involved in the anti-proliferative effect of the combined treatment. Overall, the results demonstrated that doxycycline may function as chemosensitizers by inducing an acute and lethal ROS production to enhance cytotoxic of polyphyllin G in osteosarcoma cell lines, and the combined use of drugs may provide an alternative thinking for the development of new therapeutic agents.

Induction of immunogenic cell death effect of licoricidin in cervical cancer cells by enhancing endoplasmic reticulum stress-mediated high mobility group box 1 expression

Licoricidin (LCD) is an activity compound of the roots of Glycyrrhiza uralensis, which has therapeutic efficacy, including anti-virus, anti-cancer, and enhanced immunity in Traditional Chinese Medicine. Herein, this study aimed to clarify the effect of LCD on cervical cancer cells. In the present study, we found that LCD significantly inhibited cell viability via inducing cell apoptosis and companies with cleaved-PARP protein expression and caspase-3/-9 activity. Cell viability was markedly reversed these effects by pan-caspase inhibitor Z-VAD-FMK treatment. Furthermore, we showed that LCD-induced ER (endoplasmic reticulum) stress triggers upregulating the protein level of GRP78 (Bip), CHOP, and IRE1α, and subsequently confirmed the mRNA level by quantitative real-time polymerase chain reaction. In addition, LCD exhibited the release of danger-associated molecular patterns from cervical cancer cells, such as the release of high-mobility group box 1 (HMGB1), secretion of ATP, and exposure of calreticulin (CRT) on the cell surface, which led to immunogenic cell death (ICD). These results provide a novel foundation that LCD induces ICD via triggering ER stress in human cervical cancer cells. LCD might be an ICD inducer of immunotherapy in progressive cervical cancer.

Anticancer effects of licochalcones: A review of the mechanisms

Cancer is a disease with a high fatality rate representing a serious threat to human health. Researchers have tried to identify effective anticancer drugs. Licorice is a widely used traditional Chinese medicine with various pharmacological properties, and licorice-derived flavonoids include licochalcones like licochalcone A, licochalcone B, licochalcone C, licochalcone D, licochalcone E, and licochalcone H. By regulating the expression in multiple signaling pathways such as the EGFR/ERK, PI3K/Akt/mTOR, p38/JNK, JAK2/STAT3, MEK/ERK, Wnt/β-catenin, and MKK4/JNK pathways, and their downstream proteins, licochalcones can activate the mitochondrial apoptosis pathway and death receptor pathway, promote autophagy-related protein expression, inhibit the expression of cell cycle proteins and angiogenesis factors, regulate autophagy and apoptosis, and inhibit the proliferation, migration, and invasion of cancer cells. Among the licochalcones, the largest number of studies examined licochalcone A, far more than other licochalcones. Licochalcone A not only has prominent anticancer effects but also can be used to inhibit the efflux of antineoplastic drugs from cancer cells. Moreover, derivatives of licochalcone A exhibit strong antitumor effects. Currently, most results of the anticancer effects of licochalcones are derived from cell experiments. Thus, more clinical studies are needed to confirm the antineoplastic effects of licochalcones.

A ferroptosis-related gene signature associated with immune landscape and therapeutic response in osteosarcoma

BACKGROUND

The role of ferroptosis in tumor progression and immune microenvironment is extensively investigated. However, the potential value of ferroptosis regulators in predicting prognosis and therapeutic strategies for osteosarcoma (OS) patients remains to be elucidated.

METHODS

Here, we extracted transcriptomic and survival data from Therapeutically Applicable Research to Generate Effective Treatments (TARGET) and Gene Expression Omnibus (GEO) to investigate the expression and prognostic value of ferroptosis regulators in OS patients. After comprehensive analyses, including Gene set variation analysis (GSVA), single-sample gene-set enrichment analysis (ssGSEA), Estimated Stromal and Immune cells in Malignant Tumor tissues using Expression (ESTIMATE), single-cell RNA sequencing, and biological experiments, our constructed 8-ferroptosis-regulators prognostic signature effectively predicted the immune landscape, prognosis, and chemoradiotherapy strategies for OS patients.

RESULTS

We constructed an 8-ferroptosis-regulators signature that could predict the survival outcome of OS. The signature algorithm scored samples, and high-scoring patients were more prone to worse prognoses. The tumor immune landscape suggested the positive relevance between risk score and immunosuppression. Interfering HILPDA and MUC1 expression would inhibit tumor cell proliferation and migration, and MUC1 might improve the ferroptosis resistance of OS cells. Moreover, we predicted chemoradiotherapy strategies of cancer patients following ferroptosis-risk-score groups.

CONCLUSION

Dysregulated ferroptosis gene expression can affect OS progression by affecting the tumor immune landscape and ferroptosis resistance. Our risk model can predict OS survival outcomes, and we propose that HILPDA and MUC1 are potential targets for cancer therapy.

In vitro activities of licochalcone A against planktonic cells and biofilm of Enterococcus faecalis

This study aims to evaluate the in vitro antibacterial and anti-biofilm activities of licochalcone A on Enterococcus faecalis and to investigate the possible target genes of licochalcone A in E. faecalis. This study found that licochalcone A had antibacterial activities against E. faecalis, with the MIC50 and MIC90 were 25 μM. Licochalcone A (at 4 × MIC) indicated a rapid bactericidal effect on E. faecalis planktonic cells, and killed more E. faecalis planktonic cells (at least 3-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 2, 4, and 6 h of the time-killing test. Licochalcone A (at 10 × MIC) significantly reduced the production of E. faecalis persister cells (at least 2-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 24, 48, 72, and 96 h of the time-killing test. Licochalcone A (at 1/4 × MIC) significantly inhibited the biofilm formation of E. faecalis. The RNA levels of biofilm formation-related genes, agg, esp, and srtA, markedly decreased when the E. faecalis isolates were treated with licochalcone A at 1/4 × MIC for 6 h. To explore the possible target genes of licochalcone A in E. faecalis, the licochalcone A non-sensitive E. faecalis clones were selected in vitro by induction of wildtype strains for about 140 days under the pressure of licochalcone A, and mutations in the possible target genes were detected by whole-genome sequencing. This study found that there were 11 nucleotide mutations leading to nonsynonymous mutations of 8 amino acids, and among these amino acid mutations, there were 3 mutations located in transcriptional regulator genes (MarR family transcriptional regulator, TetR family transcriptional regulator, and MerR family transcriptional regulator). In conclusion, this study found that licochalcone A had an antibacterial effect on E. faecalis, and significantly inhibited the biofilm formation of E. faecalis at subinhibitory concentrations.

Natural-like Chalcones with Antitumor Activity on Human MG63 Osteosarcoma Cells

Osteosarcoma (OS) is a malignant disease characterized by poor prognosis due to a high incidence of metastasis and chemoresistance. Recently, Licochalcone A (Lic-A) has been reported as a promising agent against OS. Starting from chalcones selected from a wide in-house library, a new series was designed and synthetized. The antitumor activity of the compounds was tested on the MG63 OS cell line through the innovative Quantitative Phase Imaging technique and MTT assay. To further investigate the biological profile of active derivatives, cell cycle progression and apoptosis induction were evaluated. An earlier and more consistent arrest in the G2-M phase with respect to Lic-A was observed. Moreover, apoptosis was assessed by Annexin V staining as well as by the detection of typical morphological features of apoptotic cells. Among the selected compounds, 1e, 1q, and 1r proved to be the most promising antitumor molecules. This study pointed out that an integrated methodological approach may constitute a valuable platform for the rapid screening of large series of compounds.

Role of Licochalcone A in Potential Pharmacological Therapy: A Review

Licochalcone A (LA), a useful and valuable flavonoid, is isolated from Glycyrrhiza uralensis Fisch. ex DC. and widely used clinically in traditional Chinese medicine. We systematically updated the latest information on the pharmacology of LA over the past decade from several authoritative internet databases, including Web of Science, Elsevier, Europe PMC, Wiley Online Library, and PubMed. A combination of keywords containing “Licochalcone A,” “Flavonoid,” and “Pharmacological Therapy” was used to help ensure a comprehensive review. Collected information demonstrates a wide range of pharmacological properties for LA, including anticancer, anti-inflammatory, antioxidant, antibacterial, anti-parasitic, bone protection, blood glucose and lipid regulation, neuroprotection, and skin protection. LA activity is mediated through several signaling pathways, such as PI3K/Akt/mTOR, P53, NF-κB, and P38. Caspase-3 apoptosis, MAPK inflammatory, and Nrf2 oxidative stress signaling pathways are also involved with multiple therapeutic targets, such as TNF-α, VEGF, Fas, FasL, PI3K, AKT, and caspases. Recent studies mainly focus on the anticancer properties of LA, which suggests that the pharmacology of other aspects of LA will need additional study. At the end of this review, current challenges and future research directions on LA are discussed. This review is divided into three parts based on the pharmacological effects of LA for the convenience of readers. We anticipate that this review will inspire further research.

Different Cell Responses to Hinokitiol Treatment Result in Senescence or Apoptosis in Human Osteosarcoma Cell Lines

Hinokitiol is a tropolone-related compound isolated from the heartwood of cupressaceous plants. It is known to exhibit various biological functions including antibacterial, antifungal, and antioxidant activities. In the study, we investigated the antitumor activities of hinokitiol against human osteosarcoma cells. The results revealed that hinokitiol treatment inhibited cell viability of human osteosarcoma U-2 OS and MG-63 cells in the MTT assay. Further study revealed that hinokitiol exposure caused cell cycle arrest at the S phase and a DNA damage response with the induction of γ-H2AX foci in both osteosarcoma cell lines. In U-2 OS cells with wild-type tumor suppressor p53, we found that hinokitiol exposure induced p53 expression and cellular senescence, and knockdown of p53 suppressed the senescence. However, in MG-63 cells with mutated p53, a high percentage of cells underwent apoptosis with cleaved-PARP expression and Annexin V staining after hinokitiol treatment. In addition, up-regulated autophagy was observed both in hinokitiol-exposed U-2 OS and MG-63 cells. As the autophagy was suppressed through the autophagy inhibitor chloroquine, hinokitiol-induced senescence in U-2 OS cells was significantly enhanced accompanying more abundant p53 expression. In MG-63 cells, co-treatment of chloroquine increased hinokitiol-induced apoptosis and decreased cell viability of the treated cells. Our data revealed that hinokitiol treatment could result in different cell responses, senescence or apoptosis in osteosarcoma cell lines, and suppression of autophagy could promote these effects. We hypothesize that the analysis of p53 status and co-administration of autophagy inhibitors might provide more precise and efficacious therapies in hinokitiol-related trials for treating osteosarcoma.

Targeting autophagy in ethnomedicine against human diseases

ETHNOPHARMACOLOGICAL RELEVANCE

In the past five years, ethnopharmacy-based drugs have been increasingly used in clinical practice. It has been reported that hundreds of ethnopharmacy-based drugs can modulate autophagy to regulate physiological and pathological processes, and ethnomedicines also have certain therapeutic effects on illnesses, revealing the important roles of these medicines in regulating autophagy and treating diseases.

AIM OF THE STUDY

This study reviews the regulatory effects of natural products on autophagy in recent years, and discusses their pharmacological effects and clinical applications in the process of diseases. It provides a preliminary literature basis and reference for the research of plant drugs in the regulation of autophagy.

MATERIALS AND METHODS

A comprehensive systematic review in the fields of relationship between autophagy and ethnomedicine in treating diseases from PubMed electronic database was performed. Information was obtained from documentary sources.

RESULTS

We recorded some illnesses associated with autophagy, then classified them into different categories reasonably. Based on the uses of these substances in different researches of diseases, a total of 80 active ingredients or compound preparations of natural drugs were searched. The autophagy mechanisms of these substances in the treatments of divers diseases have been summarized for the first time, we also looked forward to the clinical application of some of them.

CONCLUSIONS

Autophagy plays a key function in lots of illnesses, the regulation of autophagy has become one of the important means to prevent and treat these diseases. About 80 compounds and preparations involved in this review have been proved to have therapeutic effects on related diseases through the mechanism of autophagy. Experiments in vivo and in vitro showed that these compounds and preparations could treat these diseases by regulating autophagy. The typical natural products curcumin and tripterine have powerful roles in regulating autophagy and show good and diversified curative effects.

Anti-Inflammatory Effect of Licochalcone A via Regulation of ORAI1 and K+ Channels in T-Lymphocytes

Calcium signaling plays a vital role in the regulation of various cellular processes, including activation, proliferation, and differentiation of T-lymphocytes, which is mediated by ORAI1 and potassium (K⁺) channels. These channels have also been identified as highly attractive therapeutic targets for immune-related diseases. Licochalcone A is a licorice-derived chalconoid known for its multifaceted beneficial effects in pharmacological treatments, including its anti-inflammatory, anti-asthmatic, antioxidant, antimicrobial, and antitumorigenic properties. However, its anti-inflammatory effects involving ion channels in lymphocytes remain unclear. Thus, the present study aimed to investigate whether licochalcone A inhibits ORAI1 and K⁺ channels in T-lymphocytes. Our results indicated that licochalcone A suppressed all three channels (ORAI1, Kv1.3, and KCa3.1) in a concentration-dependent matter, with IC₅₀ values of 2.97 ± 1.217 µM, 0.83 ± 1.222 µM, and 11.21 ± 1.07 µM, respectively. Of note, licochalcone A exerted its suppressive effects on the IL-2 secretion and proliferation in CD3 and CD28 antibody-induced T-cells. These results indicate that the use of licochalcone A may provide an effective treatment strategy for inflammation-related immune diseases.

Uvangoletin, extracted from Sarcandra glabra, exerts anticancer activity by inducing autophagy and apoptosis and inhibiting invasion and migration on hepatocellular carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Uvangoletin is a dihydrochalcone extracted from the traditional Chinese medicinal plant Sarcandra glabra. Previous research has showed that uvangoletin could induce leukemia cell death. However, the anticancer effect of uvangoletin on hepatocellular carcinoma (HCC) has not been clarified.

AIM OF THE STUDY

This study aimed to investigate the anti-cancer effects of uvangoletin on HCC and to explore its underlying mechanisms.

MATERIALS AND METHODS

We measured the anticancer activities of uvangoletin both in vitro and in vivo by MTT assay and HepG2 xenograft model. The effects of uvangoletin on apoptosis, autophagy, migration and invasion were also determined. Apoptosis was evaluated by flow cytometry method. Autophagy was assessed by immunofluorescence assay. Cell migration and invasion ability were validated by wound healing assay and cultrex® 96 well cell migration/invasion assay. The expression level of relevant proteins and pathways were examined by western blot.

RESULTS

The results of MTT assay and HepG2 xenograft model showed that uvangoletin could inhibit HCC cells proliferation in vitro and in vivo. Uvangoletin could induce HepG2 cell apoptosis as evidence by the increased expression of cleaved caspase 3, caspase 8 and Bax while decreased Bcl-2 expression. Wound healing assay and transwell assay showed that uvangoletin inhibited HepG2 cells migration and invasion and reduced vimentin, MMP9, MMP2 expression. Uvangoletin also promoted autophagy in HepG2 cells as confirmed by the accumulation of GFP-LC3 puncta. Autophagy inhibitors like 3-MA or CQ could suppress uvangoletin-induced apoptosis. Importantly, uvangoletin-induced anti-EMT effect was also attenuated after autophagy inhibitors added in. Mechanistically, the expressions of p-JNK, p-ERK, p-p38, p-AKT, p-p70S6k and p-mTOR were significantly decreased after uvangoletin treatment.

CONCLUSION

Our results showed that uvangoletin could induce apoptotic and autophagic cell death, inhibit cell proliferation and metastasis on HepG2 cells through Akt/mTOR, MAPK and TGFβ/Smad2 signal pathways.

Liquiritigenin exerts the anti-cancer role in oral cancer via inducing autophagy-related apoptosis through PI3K/AKT/mTOR pathway inhibition in vitro and in vivo

Operative treatment on oral cancer greatly damages the chewing and language function of the patient, we aim to find better solution with fewer side effects. The anti-tumor effects of Liquiritigenin (LQ) have been explored in kinds of cancers, but not in oral cancer. In this study, our purpose is to reveal the effects of LQ on oral cancer and the associated mechanism.Cell proliferation was examined through 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 5-Ethynyl-2'- deoxyuridine (EDU) staining. Cell apoptosis in cells and tissues were assessed by flow cytometry and terminal dexynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, respectively. Expressions of AKT and light chain 3 (LC3) were detected through Immunofluorescence. In addition, xenograft model was established by injecting the CAL-27 cells (2 × 10⁶) subcutaneously into the right flanks of mice. Expression of Ki67 and Beclin1 in tissues was valued by Immunohistochemistry (IHC).We found that cell viability of CAL-27 and SCC-9 was effectively inhibited by LQ. Besides, obvious cell apoptosis and cell autophagy were induced by LQ. In addition, PI3K/AKT/mTOR pathway was sharply inactivated by LQ in oral cancer cells. Corresponding in vivo experiments demonstrated that tumor growth was largely restricted, cell apoptosis was augmented and autophagy was enhanced by LQ. What is more, phosphorylation of AKT in tumor tissues could also be inhibited by LQ. LQ inhibited the progression of oral cancer through inducing autophagy-associated apoptosis via PI3K/AKT/mTOR pathway inhibition, revealing a new possible scheme for the treatment of oral cancer.

Molecular Mechanisms of Antiproliferative Effects of Natural Chalcones

Simple Summary

Despite the important progress in cancer treatment in the past decades, the mortality rates in some types of cancer have not significantly decreased. Therefore, the search for novel anticancer drugs has become a topic of great interest. Chalcones, precursors of flavonoid synthesis in plants, have been documented as natural compounds with pleiotropic biological effects including antiproliferative/anticancer activity. This article focuses on the knowledge on molecular mechanisms of antiproliferative action of chalcones and draws attention to this group of natural compounds that may be of importance in the treatment of cancer disease.

Abstract

Although great progress has been made in the treatment of cancer, the search for new promising molecules with antitumor activity is still one of the greatest challenges in the fight against cancer due to the increasing number of new cases each year. Chalcones (1,3-diphenyl-2-propen-1-one), the precursors of flavonoid synthesis in higher plants, possess a wide spectrum of biological activities including antimicrobial, anti-inflammatory, antioxidant, and anticancer. A plethora of molecular mechanisms of action have been documented, including induction of apoptosis, autophagy, or other types of cell death, cell cycle changes, and modulation of several signaling pathways associated with cell survival or death. In addition, blockade of several steps of angiogenesis and proteasome inhibition has also been documented. This review summarizes the basic molecular mechanisms related to the antiproliferative effects of chalcones, focusing on research articles from the years January 2015–February 2021.

DNA damage response and repair in osteosarcoma: Defects, regulation and therapeutic implications

Osteosarcoma (OS) is the most common primary bone malignancy in children and adolescents which has the survival rate of 20% in its advanced stages. Osteosarcomas are mostly resistance to our common treatments. DNA damage response (DDR) is a specialized multistep process containing abundant proteins which are necessary for the survival of any cell and organism. DDR machinery detects a diversity of DNA lesions and inhibits the cell cycle progression if these lesions are not repairable. DDR is involved in aging, age-related diseases, and cancer. In recent years, DDR inhibitors have gained the attention of researches due to their potentials in offering novel therapeutic targets and improving the response of many cancers to either chemo- or radio-therapy. In this regard, we tried to gather a great body of evidence about the role of DDR ingredients in osteosarcoma's initiation/progression, prognosis, and treatment.

Perspectives and controversies regarding the use of natural products for the treatment of lung cancer

Lung cancer is the leading cause of cancer‐related mortality both in men and women and accounts for 18.4% of all cancer‐related deaths. Although advanced therapy methods have been developed, the prognosis of lung cancer patients remains extremely poor. Over the past few decades, clinicians and researchers have found that chemical compounds extracted from natural products may be useful for treating lung cancer. Drug formulations derived from natural compounds, such as paclitaxel, doxorubicin, and camptothecin, have been successfully used as chemotherapeutics for lung cancer. In recent years, hundreds of new natural compounds that can be used to treat lung cancer have been found through basic and sub‐clinical research. However, there has not been a corresponding increase in the number of drugs that have been used in a clinical setting. The probable reasons may include low solubility, limited absorption, unfavorable metabolism, and severe side effects. In this review, we present a summary of the natural compounds that have been proven to be effective for the treatment of lung cancer, as well as an understanding of the mechanisms underlying their pharmacological effects. We have also highlighted current controversies and have attempted to provide solutions for the clinical translation of these compounds.

ERK Activation-Mediated Autophagy Induction Resists Licochalcone A-Induced Anticancer Activities in Lung Cancer Cells in vitro

Introduction

The incidence and mortality rates of lung cancer rank top in the different types of cancers in China. Licochalcone A (LA) is a flavonoid extracted from the roots of licorice with antitumor effects in various cancers in vitro and in vivo. However, the role of LA in non-small cell lung cancer (NSCLC) remains largely unclear.

Methods

The cell viability was measured by MTT assay, Edu staining and colony formation assay. Apoptosis was investigated using Annexin V/PI double-stained assays with flow cytometry. Real-time quantitative RT-PCR was carried out to investigate the expression of mRNA of related proteins. Western blotting was used to investigate the expression of related proteins.

Results

The results show that LA inhibits the proliferation of NSCLC cells in a dose-dependent manner and induces apoptotic cell death. Moreover, LA significantly suppresses the expression of c-IAP1, c-IAP2, XIAP, Survivin, c-FLIP_L and RIP1 without influencing the level of mRNA. Cycloheximide chase assay demonstrates that LA greatly decreases the stability of Survivin, XIAP and RIP1. Mechanistic studies indicate that LA induces cytoprotective autophagy since block of autophagy with CQ greatly enhances LA-induced anticancer activities. Furthermore, LA rapidly induces ERK and p38 activation in a time-dependent manner in both A549 and H460 cells, but suppresses the activities of c-Jun N-terminal kinase (JNK); suppression of ERK not p38 with inhibitor attenuates LA-induced autophagy, while it remarkably enhances LA-induced cytotoxicity in lung cancer cells and further promotes the degradation of apoptosis-related proteins.

Discussion

The results of this study provide novel insights on the role of apoptosis-related proteins and the MAPKs pathway in the anticancer activities of LA.

Licochalcone A inhibits EGFR signalling and translationally suppresses survivin expression in human cancer cells

Dysfunction of epidermal growth factor receptor (EGFR) signalling plays a critical role in the oncogenesis of non–small‐cell lung cancer (NSCLC). Here, we reported the natural product, licochalcone A, exhibited a profound anti‐tumour efficacy through directly targeting EGFR signalling. Licochalcone A inhibited in vitro cell growth, colony formation and in vivo tumour growth of either wild‐type (WT) or activating mutation EGFR‐expressed NSCLC cells. Licochalcone A bound with L858R single‐site mutation, exon 19 deletion, L858R/T790M mutation and WT EGFR ex vivo, and impaired EGFR kinase activity both in vitro and in NSCLC cells. The in silico docking study further indicated that licochalcone A interacted with both WT and mutant EGFRs. Moreover, licochalcone A induced apoptosis and decreased survivin protein robustly in NSCLC cells. Mechanistically, we found that treatment with licochalcone A translationally suppressed survivin through inhibiting EGFR downstream kinases ERK1/2 and Akt. Depletion of the translation initiation complex by eIF4E knockdown effectively inhibited survivin expression. In contrast, knockdown of 4E‐BP1 showed the opposite effect and dramatically enhanced survivin protein level. Overall, our data indicate that targeting survivin might be an alternative strategy to sensitize EGFR‐targeted therapy.

Licochalcone A is a Natural Selective Inhibitor of Arginine Methyltransferase 6

Arginine methylation is a post-translational modification that is implicated in multiple biological functions including transcriptional regulation. The expression of protein arginine methyltransferases (PRMT) has been shown to be upregulated in various cancers. PRMTs have emerged as attractive targets for the development of new cancer therapies. Here, we describe the identification of a natural compound, licochalcone A, as a novel, reversible and selective inhibitor of PRMT6. Since expression of PRMT6 is upregulated in human breast cancers and is associated with oncogenesis, we used the human breast cancer cell line system to study the effect of licochalcone A treatment on PRMT6 activity, cell viability, cell cycle, and apoptosis. We demonstrated that licochalcone A is a non-S-adenosyl L-methionine (SAM) binding site competitive inhibitor of PRMT6. In MCF-7 cells, it inhibited PRMT6-dependent methylation of histone H3 at arginine 2 (H3R2), which resulted in a significant repression of estrogen receptor activity. Licochalcone A exhibited cytotoxicity towards human MCF-7 breast cancer cells, but not MCF-10A human breast epithelial cells, by upregulating p53 expression and blocking cell cycle progression at G2/M, followed by apoptosis. Thus, licochalcone A has potential for further development as a therapeutic agent against breast cancer.

Betulin inhibits mTOR and induces autophagy to promote apoptosis in human osteosarcoma cell lines

Betulin is a lupane type pentacyclic triterpenoid, and commonly found in the bark of birch trees. It displays various pharmacological properties, such as antibacterial, anti-inflammation, antitumor, and antiviral. In this report, we attempted to investigate the anti-proliferative and pro-apoptotic effects of betulin on osteosarcoma cell lines. Our results revealed that betulin significantly decreased cell viability and colony formation in osteosarcoma cell lines. Dose-dependent induction of Annexin V positive cells, activated caspase 8, activated caspase 9, activated caspase 3, and the cleavage of poly (ADP-ribose) polymerase were observed after the treatment with betulin, indicating betulin induces apoptosis in osteosarcoma cell lines. mTOR has been identified as a key modulator of autophagy in response to different stresses. In this study, we found that the treatment with betulin suppressed the activation of mTOR, and increased the level of LC 3-II, the autophagy marker, in osteosarcoma cell lines. Co-administration of the autophagy inhibitor chloroquine significantly rescued the cell viability and the clonogenic activity in betulin-treated osteosarcoma cell lines. Our data showed that betulin induced autophagy, and the up-regulated autophagy positively contributed to the apoptosis. Taken together, our findings suggested that betulin may serve as a promising anti-proliferative agent for treating osteosarcoma.

Microbial Transformation of Licochalcones

Microbial transformation of licochalcones B (1), C (2), D (3), and H (4) using the filamentous fungi Aspergillus niger and Mucor hiemalis was investigated. Fungal transformation of the licochalcones followed by chromatographic separations led to the isolation of ten new compounds 5–14, including one hydrogenated, three dihydroxylated, three expoxidized, and three glucosylated metabolites. Their structures were elucidated by combined analyses of UV, IR, MS, NMR, and CD spectroscopic data. Absolute configurations of the 2″,3″-diols in the three dihydroxylated metabolites were determined by ECD experiments according to the Snatzke’s method. The trans-cis isomerization was observed for the metabolites 7, 11, 13, and 14 as evidenced by the analysis of their ¹H-NMR spectra and HPLC chromatograms. This could be useful in better understanding of the trans-cis isomerization mechanism of retrochalcones. The fungal transformation described herein also provides an effective method to expand the structural diversity of retrochalcones for further biological studies.

Licochalcone A-Induced Apoptosis Through the Activation of p38MAPK Pathway Mediated Mitochondrial Pathways of Apoptosis in Human Osteosarcoma Cells In Vitro and In Vivo

BACKGROUND

Licochalcone A (LicA) is isolated from the roots of Glycyrrhiza glabra and possesses antitumor and anti-invasive activities against several tumor cells. However, the antitumor effects of LicA on human osteosarcoma cells have yet to be demonstrated either in vitro or in vivo.

METHODS

Cell viability was measured by MTT assay. Apoptosis and mitochondrial dysfunction were detected with Annexin V/PI staining and JC-1 staining by flow cytometry. The expressions of caspase- or mitochondrial-related proteins were demonstrated by western blotting. Antitumor effect of LicA on 143B xenograft mice in vivo.

RESULTS

LicA could inhibit cell proliferation and induce apoptosis in human osteosarcoma cells, as evidenced by a decrease in cell viability, loss of mitochondrial membrane potentials, and activation of caspases. LicA treatment substantially reduced the expression of Bcl-2 and Mcl-1 and increased the expression of cleaved-caspase-3, cleaved-caspase-9, cleaved-PARP, and Bax in HOS and U2OS cells. Moreover, mitochondrial membrane potential and apoptosis suppression mediated by Z-VAD or tauroursodeoxycholic acid significantly reduced LicA-induced mitochondria-dependent apoptosis. The study also determined that LicA treatment induced p38MAPK phosphorylation, but siRNA-p38 or BIRB796 substantially reversed cell viability through the inhibition of mitochondria-dependent apoptosis pathways. Finally, an in vivo study revealed that LicA significantly inhibited 143B xenograft tumor growth.

CONCLUSIONS

These findings demonstrate that LicA has antitumor activities against human osteosarcoma cells through p38MAPK regulation of mitochondria-mediated intrinsic apoptotic pathways in vitro and in vivo.