Guanylate cyclase activator YC-1 potentiates apoptotic effect of licochalcone A on human epithelial ovarian carcinoma cells via activation of death receptor and mitochondrial pathways

Licochalcone A Exerts Anti-Cancer Activity by Inhibiting STAT3 in SKOV3 Human Ovarian Cancer Cells

Licochalcone A (LicA), a major active component of licorice, has been reported to exhibit various pharmacological actions. The purpose of this study was to investigate the anticancer activity of LicA and detail its molecular mechanisms against ovarian cancer. SKOV3 human ovarian cancer cells were used in this study. Cell viability was measured using a cell counting kit-8 assay. The percentages of apoptotic cells and cell cycle arrest were determined by flow cytometry and Muse flow cytometry. The expression levels of proteins regulating cell apoptosis, cell cycle, and the signal transducer and activator of transcription 3 (STAT3) signaling pathways were examined using Western blotting analysis. The results indicated that LicA treatment inhibited the cell viability of SKOV3 cells and induced G2/M phase arrest. Furthermore, LicA induced an increase in ROS levels, a reduction in mitochondrial membrane potential, and apoptosis accompanied by an increase in cleaved caspases and cytoplasmic cytochrome c. Additionally, LicA caused a dramatic decrease in STAT3 protein levels, but not mRNA levels, in SKOV3 cells. Treatment with LicA also reduced phosphorylation of the mammalian target of rapamycin and eukaryotic translation initiation factor 4E-binding protein in SKOV3 cells. The anti-cancer effects of LicA on SKOV3 cells might be mediated by reduced STAT3 translation and activation.

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.

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.

Licochalcone A Promotes the Ubiquitination of c-Met to Abrogate Gefitinib Resistance

Met proto-oncogene (MET) amplification and tyrosine-protein kinase Met (c-Met) overexpression confer gefitinib resistance in non-small cell lung cancer (NSCLC). The natural product Licochalcone A (Lico A) exhibits a broad range of inhibitory effects against various tumors. However, the effects of Lico A on c-Met signaling and gefitinib resistance in NSCLC remain unclear. In the present study, Lico A efficiently overcame gefitinib-acquired resistance in NSCLC cells by suppressing c-Met signaling. Lico A decreased cell viability and colony formation dose-dependently and impaired in vivo tumorigenesis of gefitinib-resistant HCC827 and PC-9 cells. Furthermore, Lico A induced intrinsic apoptosis and upregulated the protein expression levels of cleaved poly (ADP-ribose) polymerase and cleaved caspase 3. Lico A promoted the interaction between c-Met and E3 ligase c-Casitas B-lineage lymphoma (Cbl), which enhanced c-Cbl-mediated c-Met ubiquitination and degradation. Depletion of c-Cbl compromised Lico A-induced c-Met ubiquitination and its inhibitory efficacy in gefitinib-resistant NSCLC cells. Taken together, the results suggest that Lico A is a promising antitumor agent that might be used to overcome c-Met overexpression-mediated gefitinib resistance in NSCLC cells.

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.

Anti-Proliferative and Pro-Apoptotic Effects of Licochalcone A through ROS-Mediated Cell Cycle Arrest and Apoptosis in Human Bladder Cancer Cells

Licochalcone A (LCA) is a chalcone that is predominantly found in the root of Glycyrrhiza species, which is widely used as an herbal medicine. Although previous studies have reported that LCA has a wide range of pharmacological effects, evidence for the underlying molecular mechanism of its anti-cancer efficacy is still lacking. In this study, we investigated the anti-proliferative effect of LCA on human bladder cancer cells, and found that LCA induced cell cycle arrest at G2/M phase and apoptotic cell death. Our data showed that LCA inhibited the expression of cyclin A, cyclin B1, and Wee1, but increased the expression of cyclin-dependent kinase (Cdk) inhibitor p21WAF1/CIP1, and increased p21 was bound to Cdc2 and Cdk2. LCA activated caspase-8 and -9, which are involved in the initiation of extrinsic and intrinsic apoptosis pathways, respectively, and also increased caspase-3 activity, a typical effect caspase, subsequently leading to poly (ADP-ribose) polymerase cleavage. Additionally, LCA increased the Bax/Bcl-2 ratio, and reduced the integrity of mitochondria, which contributed to the discharge of cytochrome c from the mitochondria to the cytoplasm. Moreover, LCA enhanced the intracellular levels of reactive oxygen species (ROS); however, the interruption of ROS generation using ROS scavenger led to escape from LCA-mediated G2/M arrest and apoptosis. Collectively, the present data indicate that LCA can inhibit the proliferation of human bladder cancer cells by inducing ROS-dependent G2/M phase arrest and apoptosis.

ATPase inhibitory factor 1 inhibition improves the antitumor of YC-1 against hepatocellular carcinoma

YC-1 is a synthetic compound, which serves as a hypoxia-inducible factor 1-α inhibitor or sensitizer to enhance the effect of chemotherapy. Previous studies have revealed the anti-cancer effects of YC-1 in various types of cancer, including hepatocellular carcinoma (HCC). ATPase inhibitory factor 1 (IF1) is upregulated in a number of human carcinomas and regulates mitochondrial bioenergetics and structure. However, whether IF1 is involved in the antitumor effects of YC-1 against HCC remains unclear. The present study examined the function of IF1 in HCC and its potential role in YC-1 effects within HCC cells. MTT, colony formation and Transwell assays revealed that IF1 overexpression promoted proliferation, colony formation and invasion of HCC cells, while IF1 downregulation had the opposite effects. Overexpression of IF1 reversed the inhibitory effects of YC-1 on Huh7 cell growth and invasion activities, while downregulation of IF1 increased the sensitivity of HCCLM3 cells to YC-1. YC-1 treatment of HCCLM3 and Huh7 cells reduced the levels of phosphorylated (p-) signal transducer and activator of transcription 3 (STAT3) and IF1, and increased the expression of E-cadherin. IF1 knockdown resulted in decreased p-STAT3 levels and increased E-cadherin expression, while IF1 overexpression increased p-STAT3 levels and reduced the expression of E-cadherin. The present study demonstrated that the inhibition of IF1 improves the antitumor effects of YC-1 in HCC cells. These findings support the clinical strategy of combining YC-1 and an IF1 inhibitor for the treatment of HCC.

Hesperidin inhibits ovarian cancer cell viability through endoplasmic reticulum stress signaling pathways

Hesperidin is a vitamin P flavonoid compound primarily present in citrus fruits. The aim of the present study was to investigate whether hesperidin inhibits ovarian cancer cell viability via endoplasmic reticulum stress signaling pathways. A2780 cells were treated with various doses of hesperidin for 6, 12 or 24 h, and the viability of A2780 cells was assessed using the MTT assay. Hesperidin decreased the viability of A2780 cells and increased cytotoxicity in a dose- and time-dependent manner. In addition, hesperidin induced apoptosis and increased cleaved caspase-3 protein expression levels in A2780 cells. Furthermore, hesperidin markedly increased the protein expression of anti-growth arrest- and DNA damage-inducible gene 153, anti-CCAAT'enhancer-binding protein homologous protein, glucose-regulated protein 78 and cytochrome c in A2780 cells. The results of the present study indicated that hesperidin inhibits cell viability and induces apoptosis in ovarian cancer cells via endoplasmic reticulum stress signaling pathways. Thus, hesperidin may offer a novel therapeutic tool for ovarian carcinoma.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

Licochalcone A Suppresses Specificity Protein 1 as a Novel Target in Human Breast Cancer Cells

Licochalcone A (LCA), isolated from the root of Glycyrrhiza inflata, are known to have medicinal effect such as anti-oxidant, anti-bacterial, anti-viral, and anti-cancer. Though, as a pharmacological mechanism regulator, anti-cancer studies on LCA were not investigated in human breast cancer. We investigated the anti-proliferative and apoptotic effect of LCA in human breast cancer cells MCF-7 and MDA-MB-231 through MTS assay, PI staining, Annexin-V/7-AAD assay, mitochondrial membrane potential assay, multi-caspase assay, RT-PCR, Western blot analysis, and anchorage-independent cell transformation assay. Our results showed the little difference between two cells, as MCF-7 cell is both estrogen/progesterone receptor positive, there were only effect on Sp1 protein level, but not in mRNA level. Adversely, estrogen/progesterone/human epidermal growth factor receptor 2 triple negative, MDA-MB-231 showed decreased Sp1 mRNA, and protein levels. To confirm the participation of Sp1 in breast cancer cell viability, siRNA techniques were introduced. Both cells showed dysfunction of mitochondrial membrane potential and mitochondrial ROS production, which reflects it passed intracellular mitochondrial apoptosis pathway. Additionally, LCA showed the anti-proliferative and apoptotic effect in breast cancer cells through regulating Sp1 and apoptosis-related proteins in a dose- and a time-dependent manner. Consequently, LCA might be a potential anti-breast cancer drug substitute. J. Cell. Biochem. 118: 4652-4663, 2017. © 2017 Wiley Periodicals, Inc.

Soluble guanylate cyclase stimulators increase sensitivity to cisplatin in head and neck squamous cell carcinoma cells

Head and neck squamous cell carcinoma (HNSCC) is an aggressive and often fatal disease. Cisplatin is the most common chemotherapeutic drug in the treatment of HNSCC, but intrinsic and acquired resistance are frequent, and severe side effects occur at high doses. The second messenger cyclic GMP (cGMP) is produced by soluble guanylate cyclase (sGC). We previously reported that activation of the cGMP signaling cascade caused apoptosis in HNSCC cells, while others found that this pathway enhances cisplatin efficacy in some cell types. Here we found that sGC stimulators reduced HNSCC cell viability synergistically with cisplatin, and enhanced apoptosis by cisplatin. Moreover, the sGC stimulators effectively reduced viability in cells with acquired cisplatin resistance, and were synergistic with cisplatin. The sGC stimulator BAY 41-2272 reduced expression of the survival proteins EGFR and β-catenin, and increased pro-apoptotic Bax, suggesting a potential mechanism for the anti-tumorigenic effects of these drugs. The sGC stimulator Riociguat is FDA-approved to treat pulmonary hypertension, and others are being studied for therapeutic use in several diseases. These drugs could provide valuable addition or alternative to cisplatin in the treatment of HNSCC.

Licochalcone A induces T24 bladder cancer cell apoptosis by increasing intracellular calcium levels

Licochalcone A (LCA) has been reported to significantly inhibit cell proliferation, increase reactive oxygen species (ROS) levels, and induce apoptosis of T24 human bladder cancer cells via mitochondria and endoplasmic reticulum (ER) stress-triggered signaling pathways. Based on these findings, the present study aimed to investigate the mechanisms by which LCA induces apoptosis of T24 cells. Cultured T24 cells were treated with LCA, and cell viability was measured using the sulforhodamine B assay. Apoptosis was detected by flow cytometry with Annexin V/propidium iodide staining, and by fluorescent microscopy with Hoechst 33258 staining. The levels of intracellular free calcium ions were determined using Fluo-3 AM dye marker. Intracellular ROS levels were assessed using the 2',7'-dichlorodihydrofluorescein diacetate probe assay. The mitochondrial membrane potential was measured using 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl benzimidazole carbocyanine iodide. Furthermore, the mRNA expression levels of B‑cell lymphoma (Bcl)‑extra large, Bcl‑2‑associated X protein, Bcl‑2‑interacting mediator of cell death, apoptotic protease activating factor‑1 (Apaf‑1), calpain 2, cysteinyl aspartate specific proteinase (caspase)‑3, caspase‑4 and caspase‑9 were determined using reverse transcription semiquantitative and quantitative polymerase chain reaction analyses. Treatment with LCA inhibited proliferation and induced apoptosis of T24 cells, and increased intracellular Ca2+ levels and ROS production. Furthermore, LCA induced mitochondrial dysfunction, decreased mitochondrial membrane potential, and increased the mRNA expression levels of Apaf‑1, caspase‑9 and caspase‑3. Exposure of T24 cells to LCA also triggered calpain 2 and caspase‑4 activation, resulting in apoptosis. These findings indicated that LCA increased intracellular Ca2+ levels, which may be associated with mitochondrial dysfunction. In addition, the ER stress pathway may be considered an important mechanism by which LCA induces apoptosis of T24 bladder cancer cells.

Induction of C/EBP homologous protein-mediated apoptosis and autophagy by licochalcone A in non-small cell lung cancer cells

Licochalcone A (LCA), a flavonoid isolated from the famous Chinese medicinal herb Glycyrrhiza uralensis Fisch, presents obvious anti-cancer effects. In this study, the anti-cancer effects and potential mechanisms of LCA in non-small cell lung cancer (NSCLC) cells were studied. LCA decreased cell viability, increased lactate dehydrogenase release, and induced apoptosis in a concentration-dependent manner in NSCLC cells while not in human embryonic lung fibroblast cells. The expression of phosphatidylethanolamine-modified microtubule-associated protein light-chain 3 (LC3-II) and formation of GFP-LC3 punta, two autophagic markers, were increased after treatment with LCA. LCA-induced LC3-II expression was increased when combined with chloroquine (CQ), while knock-down of autophagy related protein (ATG) 7 or ATG5 reversed LCA-induced LC3-II expression and GFP-LC3 punta formation, suggesting that LCA induced autophagy in NSCLC cells. Inhibition of autophagy could not reverse the LCA-induced cell viability decrease and apoptosis. In addition, LCA increased the expression of endoplasmic reticulum stress related proteins, such as binding immunoglobulin protein and C/EBP homologous protein (CHOP). Knock-down of CHOP reversed LCA-induced cell viability decrease, apoptosis, and autophagy. Taken together, LCA-induced autophagic effect is an accompanied phenomenon in NSCLC cells, and CHOP is critical for LCA-induced cell viability decrease, apoptosis, and autophagy.

Neuroprotective activities of curcumin and quercetin with potential relevance to mitochondrial dysfunction induced by oxaliplatin

Peripheral neurotoxicity is one of the serious dose-limiting side effects of oxaliplatin (Oxa) when used in the treatment of malignant conditions. It is documented that it elicits major side effects specifically neurotoxicity due to oxidative stress forcing the patients to limit its clinical use in long-term treatment. Oxidative stress has been proven to be involved in Oxa-induced toxicity including neurotoxicity. The mitochondria have recently emerged as targets for anticancer drugs in various kinds of toxicity including neurotoxicity that can lead to neoplastic disease. However, there is paucity of literature involving the role of the mitochondria in mediating Oxa-induced neurotoxicity and its underlying mechanism is still debatable. The purpose of this study was to investigate the dose-dependent damage caused by Oxa on isolated brain mitochondria under in vitro conditions. The study was also designed to investigate the neuroprotective effects of nutraceuticals, curcumin (CMN), and quercetin (QR) on Oxa-induced mitochondrial oxidative stress and respiratory chain complexes in the brain of rats. Oxidative stress biomarkers, levels of nonenzymatic antioxidants, activities of enzymatic antioxidants, and mitochondrial complexes were evaluated against the neurotoxicity induced by Oxa. Pretreatment with CMN and QR significantly replenished the mitochondrial lipid peroxidation levels and protein carbonyl content induced by Oxa. CMN and QR ameliorated altered nonenzymatic and enzymatic antioxidants and complex enzymes of mitochondria. We conclude that CMN and QR, by attenuating oxidative stress as evident by mitochondrial dysfunction, hold promise as agents that can potentially reduce Oxa-induced adverse effects in the brain.

Licochalcone A-induced human gastric cancer BGC-823 cells apoptosis by regulating ROS-mediated MAPKs and PI3K/AKT signaling pathways

Both phosphatidylinositol 3-kinase (PI3K)/AKT and mitogen activated protein kinase (MAPK) signaling cascades play an important role in cell proliferation, survival, angiogenesis, and metastasis of tumor cells. In the present report, we investigated the effects of licochalcone A (LA), a flavonoid extracted from licorice root, on the PI3K/AKT/mTOR and MAPK activation pathways in human gastric cancer BGC-823 cells. LA increased reactive oxygen species (ROS) levels, which is associated with the induction of apoptosis as characterized by positive Annexin V binding and activation of caspase-3, and cleavage of poly-ADP-ribose polymerase (PARP). Inhibition of ROS generation by N-acetylcysteine (NAC) significantly prevented LA-induced apoptosis. Interestingly, we also observed that LA caused the activation of ERK, JNK, and p38 MAPK in BGC-823 cells. The antitumour activity of LA-treated BGC-823 cells was significantly distinct in KM mice in vivo. All the findings from our study suggest that LA can interfere with MAPK signaling cascades, initiate ROS generation, induce oxidative stress and consequently cause BGC cell apoptosis.

Licochalcone A induces apoptosis through endoplasmic reticulum stress via a phospholipase Cγ1-, Ca(2+)-, and reactive oxygen species-dependent pathway in HepG2 human hepatocellular carcinoma cells

Licochalcone A (LicA), an estrogenic flavonoid, induces apoptosis in multiple types of cancer cells. In this study, the molecular mechanisms underlying the anti-cancer effects of LicA were investigated in HepG2 human hepatocellular carcinoma cells. LicA induced apoptotic cell death, activation of caspase-4, -9, and -3, and expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP). Inhibition of ER stress by CHOP knockdown or treatment with the ER stress inhibitors, salubrinal and 4-phenylbutyric acid, reduced LicA-induced cell death. LicA also induced reactive oxygen species (ROS) accumulation and the anti-oxidant N-acetylcysteine reduced LicA-induced cell death and CHOP expression. In addition, LicA increased the levels of cytosolic Ca(2+), which was blocked by 2-aminoethoxydiphenyl borate (an antagonist of inositol 1,4,5-trisphosphate receptor) and BAPTA-AM (an intracellular Ca(2+) chelator). 2-Aminoethoxydiphenyl borate and BAPTA-AM inhibited LicA-induced cell death. Interestingly, LicA induced phosphorylation of phospholipase Cγ1 (PLCγ1) and inhibition of PLCγ1 reduced cell death and ER stress. Moreover, the multi-targeted receptor tyrosine kinase inhibitors, sorafenib and sunitinib, reduced LicA-induced cell death, ER stress, and cytosolic Ca(2+) and ROS accumulation. Finally, LicA induced phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) and c-Met receptor and inhibition of both receptors by co-transfection with VEGFR2 and c-Met siRNAs reversed LicA-induced cell death, Ca(2+) increase, and CHOP expression. Taken together, these findings suggest that induction of ER stress via a PLCγ1-, Ca(2+)-, and ROS-dependent pathway may be an important mechanism by which LicA induces apoptosis in HepG2 hepatocellular carcinoma cells.

Chemopreventive Effects of Licorice and Its Components

Cancer is still a major health issue worldwide and identifying novel but safe compounds for prevention and treatment is a high priority. Licorice (Glycyrrhiza) is a perennial plant that is cultivated in many countries and has been reported to exert antioxidant, anti-inflammatory and anticancer effects. However, some components of licorice exert unwanted side effects and therefore identifying safer licorice components would be ideal. The anticancer activities of many of the licorice components appear to include cycle arrest, apoptosis induction, and general antioxidant effects. Commonly reported indirect protein targets important in tumorigenesis include many cell cycle-related proteins, apoptosis-associated proteins, MMP proteins, COX-2, GSK-β, Akt, NF-κB, and MAP kinases. Importantly, several licorice components were reported to directly bind to and inhibit the activities of PI3-K, MKK4, MKK7, JNK1, mTOR, and Cdk2, resulting in decreased carcinogenesis in several cell and mouse models with no obvious toxicity. This review focuses on specific components of licorice for which a direct protein target has been identified.

Licochalcone-A induces intrinsic and extrinsic apoptosis via ERK1/2 and p38 phosphorylation-mediated TRAIL expression in head and neck squamous carcinoma FaDu cells

We investigated Licochalcone-A (Lico-A)-induced apoptosis and the pathway underlying its activity in a pharyngeal squamous carcinoma FaDu cell line. Lico-A purified from root of Glycyrrhiza inflata had cytotoxic effects, significantly increasing cell death in FaDu cells. Using a cell viability assay, we determined that the IC50 value of Lico-A in FaDu cells was approximately 100 µM. Chromatin condensation was observed in FaDu cells treated with Lico-A for 24 h. Consistent with this finding, the number of apoptotic cells increased in a time-dependent manner when FaDu cells were treated with Lico-A. TRAIL was significantly up-regulated in Lico-A-treated FaDu cells in a dose-dependent manner. Apoptotic factors such as caspases and PARP were subsequently activated in a caspase-dependent manner. In addition, levels of pro-apoptotic factors increased significantly in response to Lico-A treatment, while levels of anti-apoptotic factors decreased. Lico-A-induced TRAIL expression was mediated in part by a MAPK signaling pathway involving ERK1/2 and p38. In xenograft mouse model, Lico-A treatment effectively suppressed the growth of FaDu cell xenografts by activating caspase-3, without affecting the body weight of mice. Taken together, these data suggest that Lico-A has potential chemopreventive effects and should therefore be developed as a chemotherapeutic agent for pharyngeal squamous carcinoma.

Licochalcone A, a natural chalconoid isolated from Glycyrrhiza inflata root, induces apoptosis via Sp1 and Sp1 regulatory proteins in oral squamous cell carcinoma

Licochalcone A (LCA), a chalconoid derived from root of Glycyrrhiza inflata, has been known to possess a wide range of biological functions such as antitumor, anti-angiogenesis, antiparasitic, anti-oxidant, antibacterial and anti-inflammatory effects. However, the anticancer effects of LCA on oral squamous cell carcinoma (OSCC) have not been reported. Our data showed that LCA inhibited OSCC cell (HN22 and HSC4) growth in a concentration- and time-dependent manner. Mechanistically, it was mediated via downregulation of specificity protein 1 (Sp1) expression and subsequent regulation of Sp1 downstream proteins such as p27, p21, cyclin D1, Mcl-1 and survivin. Here, we found that LCA caused apoptotic cell death in HSC4 and HN22 cells, as characterized by sub-G1 population, nuclear condensation, Annexin V staining, and multi-caspase activity and apoptotic regulatory proteins such as Bax, Bid, Bcl(-xl), caspase-3 and PARP. Consequently, this study strongly suggests that LCA induces apoptotic cell death of OSCC cells via downregulation of Sp1 expression, prompting its potential use for the treatment of human OSCC.

YC-1 enhances the anti-tumor activity of sorafenib through inhibition of signal transducer and activator of transcription 3 (STAT3) in hepatocellular carcinoma

Background

Traditional systemic chemotherapy does not provide survival benefits in patients with hepatocellular carcinoma (HCC). Molecular targeted therapy shows promise for HCC treatment, however, the duration of effectiveness for targeted therapies is finite and combination therapies offer the potential for improved effectiveness.

Methods

Sorafenib, a multikinase inhibitor, and YC-1, a soluble guanylyl cyclase (sGC) activator, were tested in HCC by proliferation assay, cell cycle analysis and western blot in vitro and orthotopic and ectopic HCC models in vivo.

Results

In vitro, combination of sorafenib and YC-1 synergistically inhibited proliferation and colony formation of HepG2, BEL-7402 and HCCLM3 cells. The combination also induced S cell cycle arrest and apoptosis, as observed by activated PARP and caspase 8. Sorafenib and YC-1 respectively suppressed the expression of phosphorylated STAT3 (p-STAT3) (Y705) in a dose- and time-dependent manner. Combination of sorafenib and YC-1 significantly inhibited the expression of p-STAT3 (Y705) (S727), p-ERK1/2, cyclin D1 and survivin and SHP-1 activity compared with sorafenib or YC-1 used alone in all tested HCC cell lines. In vivo, sorafenib-YC-1 combination significantly suppressed the growth of HepG2 tumor xenografts with decreased cell proliferation and increased apoptosis observed by PCNA and PARP. Similar results were also confirmed in a HCCLM3 orthotopic model. There was a reduction in CD31-positive blood vessels and reduced VEGF expression, which suggested a combinational effect of sorafenib and YC-1 on angiogenesis. The reduced expression of p-STAT3, cyclin D1 and survivin was also observed with the combination of sorafenib and YC-1.

Conclusions

Our data show that sorafenib-YC-1 combination is a novel potent therapeutic agent that can target the STAT3 signaling pathway to inhibit HCC tumor growth.

Licochalcone A induces apoptosis in KB human oral cancer cells via a caspase-dependent FasL signaling pathway

Licochalcone A (Lico-A) is a natural phenol licorice compound with multiple bioactivities, including anti-inflammatory, anti-microbial, anti-fungal and osteogenesis-inducing properties. In the present study, we investigated the Lico-A-induced apoptotic effects and examined the associated apoptosis pathway in KB human oral cancer cells. Lico-A decreased the number of viable KB oral cancer cells. However, Lico-A did not have an effect on primary normal human oral keratinocytes. In addition, the IC₅₀ value of Lico-A was determined to be ~50 μM following dose-dependent stimulation. KB oral cancer cells stimulated with Lico-A for 24 h showed chromatin condensation by DAPI staining, genomic DNA fragmentation by agarose gel electrophoresis and a gradually increased apoptotic cell population by FACS analysis. These data suggest that Lico-A induces apoptosis in KB oral cancer cells. Additionally, Lico-A-induced apoptosis in KB oral cancer cells was mediated by the expression of factor associated suicide ligand (FasL) and activated caspase-8 and −3 and poly(ADP-ribose) polymerase (PARP). Furthermore, in the KB oral cancer cells co-stimulation with a caspase inhibitor (Z-VAD-fmk) and Lico-A significantly abolished the apoptotic phenomena. Our findings demonstrated that Lico-A-induced apoptosis in KB oral cancer cells involves the extrinsic apoptotic signaling pathway, which involves a caspase-dependent FasL-mediated death receptor pathway. Our data suggest that Lico-A be developed as a chemotherapeutic agent for the management of oral cancer.

The NS3 protease and helicase domains of Japanese encephalitis virus trigger cell death via caspase‑dependent and ‑independent pathways

Japanese encephalitis virus (JEV), a mosquito‑borne flavivirus, causes acute encephalitis and nervous damage. Previous studies have demonstrated that JEV induces apoptosis in infected cells. However, to date the mechanisms of JEV‑induced apoptosis are unclear. In order to identify the viral proteins associated with JEV‑induced apoptosis, pEGFP‑non‑structural protein 3 (NS3) 1‑619 (expressing the JEV NS3 intact protein, including the protease and helicase domains), pEGFP‑NS3 1‑180 (expressing the protease domain) and pEGFP‑NS3 163‑619 (expressing the helicase domain) were transfected into target cells to study cell death. Results demonstrate that the JEV NS3 intact protein and protease and helicase domains induce cell death. In addition, cell death was identified to be significantly higher in cells transfected with the NS3 protease domain compared with the intact protein and helicase domain. Caspase activation was also analyzed in the current study. NS3 intact protein and NS3 protease and helicase domains activated caspase‑9/‑3‑dependent and ‑independent pathways. However, caspase‑8 activity was not found to be significantly different in NS3‑transfected cells compared with control. In summary, the present study demonstrates that the NS3 helicase and protease domains of JEV activate caspase‑9/‑3‑dependent and ‑independent cascades and trigger cell death.