Alantolactone Induces Apoptosis and Cell Cycle Arrest on Lung Squamous Cancer SK-MES-1 Cells

Sesquiterpene lactones as emerging biomolecules to cease cancer by targeting apoptosis

Apoptosis is a programmed cell death comprising two signaling cascades including the intrinsic and extrinsic pathways. This process has been shown to be involved in the therapy response of different cancer types, making it an effective target for treating cancer. Cancer has been considered a challenging issue in global health. Cancer cells possess six biological characteristics during their developmental process known as cancer hallmarks. Hallmarks of cancer include continuous growth signals, unlimited proliferation, resistance to proliferation inhibitors, apoptosis escaping, active angiogenesis, and metastasis. Sesquiterpene lactones are one of the large and diverse groups of planet-derived phytochemicals that can be used as sources for a variety of drugs. Some sesquiterpene lactones possess many biological activities such as anti-inflammatory, anti-viral, anti-microbial, anti-malarial, anticancer, anti-diabetic, and analgesic. This review article briefly overviews the intrinsic and extrinsic pathways of apoptosis and the interactions between the modulators of both pathways. Also, the present review summarizes the potential effects of sesquiterpene lactones on different modulators of the intrinsic and extrinsic pathways of apoptosis in a variety of cancer cell lines and animal models. The main purpose of the present review is to give a clear picture of the current knowledge about the pro-apoptotic effects of sesquiterpene lactones on various cancers to provide future direction in cancer therapeutics.

Alantolactone Induced Apoptosis and DNA Damage of Cervical Cancer through ATM/CHK2 Signaling Pathway

Traditional Chinese Medicine, known for its minimal side effects and significant clinical efficacy, has attracted considerable interest for its potential in cancer therapy. In particular, Inula helenium L. has demonstrated effectiveness in inhibiting a variety of cancers. This study focuses on alantolactone (ALT), a prominent compound from Inula helenium L., recognized for its anti-cancer capabilities across multiple cancer types. The primary objective of this study is to examine the influence of ALT on the proliferation, apoptosis, cell cycle, and tumor growth of cervical cancer (CC) cells, along with its associated signaling pathways. To determine protein expression alterations, Western blot analysis was conducted. Furthermore, an in vivo model was created by subcutaneously injecting HeLa cells into nude mice to assess the impact of ALT on cervical cancer. Our research thoroughly investigates the anti-tumor potential of ALT in the context of CC. ALT was found to inhibit cell proliferation and induce apoptosis in SiHa and HeLa cell lines, particularly targeting ataxia-telangiectasia mutated (ATM) proteins associated with DNA damage. The suppression of DNA damage and apoptosis induction when ATM was inhibited underscores the crucial role of the ATM/cell cycle checkpoint kinase 2 (CHK2) axis in ALT's anti-tumor effects. In vivo studies with a xenograft mouse model further validated ALT's effectiveness in reducing CC tumor growth and promoting apoptosis. This study offers new insights into how ALT combats CC, highlighting its promise as an effective anti-cervical cancer agent and providing hope for improved treatment outcomes for CC patients.

Alantolactone induces concurrent apoptosis and GSDME-dependent pyroptosis of anaplastic thyroid cancer through ROS mitochondria-dependent caspase pathway

BACKGROUND

Anaplastic thyroid cancer (ATC) is one of the fatal cancers and has not effective treatments. Alantolactone (ATL), a terpenoid extracted from traditional Chinese medicinal herb Inula helenium L., confers significant anti-inflammatory, antibacterial and antitumor activity. However, the activity and mechanisms of ATL in ATC remain unclear.

PURPOSE

To investigate the potential anti-ATC effects in vitro and in vivo and the mechanisms involved.

METHODS

The anti-proliferative activity of Alantolactone (ATL) against ATC cells was analyzed through CCK-8 and colony formation assays. Flow cytometry assay was performed to assess the cell cycle, cell apoptosis, ROS, and mitochondrial membrane potential (ΔΨm), whereas the cellular localization of cytochrome c and calreticulin were determined using cellular immunofluorescence assays. The lactate dehydrogenase (LDH) enzyme activity in the cell culture medium was measured using a commercial LDH kit, whereas ELISA was conducted to assess the secretory function of IL-1β. Western blot assays were conducted to determine the expression or regulation of proteins associated with apoptosis and pyroptosis. Subcutaneous tumor model of nude mice was established to evaluate the anticancer activity of ATL in vivo. The expression of Ki67, cyclin B1, cleaved-PARP, cleaved-caspase 3, and IL-1β in the animal tumor tissues was profiled using immunohistochemistry analyses.

RESULTS

Our data showed that ATL significantly inhibited the proliferation and colony formation activity of ATC cells. ATL induced ATC cell cycle arrest at G2/M phase, and downregulated the expression of cyclin B1 and CDC2. Furthermore, ATL induced concurrent apoptosis and pyroptosis in the ATC cells, and the cleavage of PARP and GSDME. It also significantly increased the release of LDH and IL-1β. Mechanically, ATL-mediated increase in ROS suppressed the Bcl-2/Bax ratio, downregulated the mitochondrial membrane potential and increased the release of cytochrome c, leading to caspase 9 and caspase 3 cleavage. We also found that ATL induced the translocation of an immunogenic cell death marker (calreticulin) to the cell membrane. In addition, it inhibited the growth of the ATC subcutaneous xenograft model, and activated proteins associated with apoptosis and pyroptosis, with a high safety profile.

CONCLUSION

Taken together, these results firstly demonstrated that ATL exerted an anti-ATC activity by inducing concurrent apoptosis and GSDME-dependent pyroptosis through ROS-mediated mitochondria-dependent caspase activation. Meanwhile, these cell deaths exhibited obvious characteristics of immunogenic cell death, which may synergistically increase the potential of cancer immunotherapy in ATC. Further studies are needed to explore deeper mechanisms for the anti- ATC activity of ATL.

Sesquiterpene Lactones Attenuate Paclitaxel Resistance Via Inhibiting MALAT1/STAT3/ FUT4 Axis and P-Glycoprotein Transporters in Lung Cancer Cells

Paclitaxel resistance is a challenging factor in chemotherapy resulting in poor prognosis and cancer recurrence. Signal transducer and activator of transcription factor 3 (STAT3), a key transcription factor, performs a critical role in cancer development, cell survival and chemoresistance, while its inactivation overwhelms drug resistance in numerous cancer types including lung cancer. Additionally, the fucosyltransferase 4 (FUT4) is a crucial enzyme in post-translational modification of cell-surface proteins involved in various pathological conditions such as tumor multidrug resistance (MDR). The P-glycoprotein (P-GP) is the well-known ABC transporter member that imparts drug resistance in different cancer types, most notably paclitaxel resistance in lung cancer cells. LncRNA-MALAT1 exerts a functional role in the cancer development as well as the drug resistance and is linked with STAT3 activation and activity of FUT4. Moreover, STAT3-mediated induction of P-GP is well-documented. Natural compounds of Sesquiterpene Lactone (SL) family are well-known for their anticancer properties with particular emphasis over STAT3 inhibitory capabilities. In this study, we explored the positive correlation of MALAT1 with STAT3 and FUT4 activity in paclitaxel resistant A549 (A549/T) lung cancer cells. Additionally, we investigated the anticancer activity of two well-known members of SLs, alantolactone (ALT) and Brevilin A (Brv-A), in A549/T lung cancer cells. ALT and Brv-A induced apoptosis in A549/T cells. Furthermore, these two natural SLs suppressed MALAT1 expression, STAT3 activation, and FUT4 and P-GP expression which are the hallmarks for paclitaxel resistance in A549 lung cancer cells. The inhibition of MALAT1 enhanced the competence of these SLs members significantly, which accounted for the growth inhibition as well as anti-migratory and anti-invasive effects of ALT and Brv-A. These findings suggest SLs to be the promising agents for overcoming paclitaxel resistance in A549 lung cancer cells.

Alantolactone: A Natural Plant Extract as a Potential Therapeutic Agent for Cancer

Alantolactone (ALT) is a natural compound extracted from Chinese traditional medicine Inula helenium L. with therapeutic potential in the treatment of various diseases. Recently, in vitro and in vivo studies have indicated cytotoxic effects of ALT on various cancers, including liver cancer, colorectal cancer, breast cancer, etc. The inhibitory effects of ALT depend on several cancer-associated signaling pathways and abnormal regulatory factors in cancer cells. Moreover, emerging studies have reported several promising strategies to enhance the oral bioavailability of ALT, such as combining ALT with other herbs and using ALT-entrapped nanostructured carriers. In this review, studies on the anti-tumor roles of ALT are mainly summarized, and the underlying molecular mechanisms of ALT exerting anticancer effects on cells investigated in animal-based studies are also discussed.

Alantolactone: A sesquiterpene lactone with diverse pharmacological effects

Alantolactone (Ala) is a sesquiterpene lactone that can be isolated from many herbal plants belonging to Asteraceae. Besides the antimicrobial activities against bacteria, fungi and viruses, Ala has also demonstrated significant anti-inflammatory effects in various models by inhibiting NF-κB and MAPKs to decrease the pro-inflammatory cytokines such as IL-1β, IL-6 and TNF-α. The antitumor effects of Ala have been demonstrated in vitro and in vivo via inducing intrinsic apoptosis, oxidative stress, ER stress, cell cycle arrest and inhibiting autophagy and STAT3 phosphorylation, which are also involved in its combination or synergy with other antitumor drugs. Ala also has neuroprotective activity through attenuating oxidative stress and inflammation, besides its modulation of glucose and lipid metabolism. This review summarizes the recent advances of the pharmacological effects of Ala, including anti-inflammatory, antitumor, antimicrobial, neuroprotective activities, as well as the underlying mechanisms. Ala might be employed as a potential lead to develop drugs for multiple diseases.

Alantolactone exhibits antiproliferative and apoptosis-promoting properties in colon cancer model via activation of the MAPK-JNK/c-Jun signaling pathway

Colorectal cancer (CRC) is one of the most common human malignancies in the digestive tract with high mortality. Alantolactone (ATL), as a plant-derived sesquiterpene lactone, has shown a variety of pharmacological activities, such as antibacterial, anti-inflammatory, anti-virus and so on. However, the exact molecular mechanism of ATL in colorectal cancer remains largely unknown. Here, we performed a study to explore the effect and mechanism of ATL on colorectal cancer. The CCK-8 assay, colony formation assay, Wound-healing and Transwell assays were performed to evaluate the cytotoxic effect, antiproliferative effect, anti-migratory and anti-invasive properties of ATL respectively. The xenograft tumor model was established in Balb/c mice to evaluate the anti-tumor effect. The expression levels of proteins involved the MAPK-JNK/c-Jun signaling pathway were measured by Western blot and RT-qPCR both in cells and tumor tissues. The results showed that ATL could inhibit the cells activities of various colon cancer cell lines. Moreover, ATL could induce HCT-116 cells nuclear pyknosis, mitochondrial membrane potential loss, G0/G1 phase arrest, as well as enhance the proportion of apoptosis cells and inhibit colony formation. The migration distance and invasion rate of cells were significantly reduced after treated with ATL. Additionally, in the xenograft model, ATL (50 mg/kg) significantly decreased the tumor tumor volume and weight (p < 0.001). For the anti-colon cancer mechanism, the ATL showed the anti-proliferative and pro-apoptosis effect by activating MAPK-JNK/c-Jun signaling pathway. In conclusion, ATL exhibits anti-proliferation and apoptosis-promoting potential in colon cancer via the activation of MAPK-JNK/c-Jun signaling pathway.

A comprehensive review of anticancer mechanisms of action of Alantolactone

Cancer is considered as the main challenge of human communities, and it annually imposes a significant economic burden on society. Natural products have been used for treatment of many diseases including inflammation, infections, neurological disorders, atherosclerosis, asthma and cancer for many years. Sesquiterpene lactones (STLs) refers to a group of natural products with different biological activities. A type of STL that has recently attracted much attention is Alantolactone (ALT). In recent years, many studies have investigated the molecular mechanism of this compound affecting cancer cells and results suggest that this compound exerts its anticancer effects by providing free radicals and inhibiting some of the signaling pathways that are effective in progression of cancer cells. The present study is aimed to introduce the latest molecular mechanisms of ALT proposed by researchers in recent years.

Alantolactone induces apoptosis in THP-1 cells through STAT3, survivin inhibition, and intrinsic apoptosis pathway

Cancer is the second foremost cause of mortality in the world, and THP-1 cells play an important role in cancer progression. Alantolactone (ALT), a sesquiterpene lactone compound derived from Inula helenium, has a number of biological activities including antibacterial, antifungal, and anticancer. The current study was conducted to investigate the effects of ALT on THP-1 cells and its underlying molecular mechanisms. THP-1 cells were cultured and treated with ALT (20, 40 µM) for 12 hr, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, cell morphology, live/dead, and apoptosis assays were performed. The gene expressions at the protein level were checked through Western blot. Results show that ALT decreased cell viability and increased cell death and apoptosis. We found that ALT inhibited STAT3 and survivin expression. Furthermore, ALT induced mitochondrial-dependent apoptosis through a decrease in B-cell lymphoma-2 (Bcl-2) and Bcl-xL and increase in Bax expression, resulting in the release of cytochrome c (Cyt-c) from mitochondria. Cyt-c release from mitochondria further increased cleaved (cl) caspase-3 and cl-PARP expression and led the cells to apoptosis. Therefore, ALT might be a good therapy for the progression due to THP-1 cells.

Sesquiterpenes and their derivatives-natural anticancer compounds: An update

Sesquiterpenes belong to the largest group of plant secondary metabolites, which consist of three isoprene building units. These compounds are widely distributed in various angiosperms, a few gymnosperms and bryophytes. Sesquiterpenes and their allied derivatives are bio-synthesized in various plant parts including leaves, fruits and roots. These plant-based metabolites are predominantly identified in the Asteraceae family, wherein up to 5000 complexes have been documented to date. Sesquiterpenes and their derivatives are characteristically associated with plant defence mechanisms owing to their antifungal, antibacterial and antiviral activities. Over the last two decades, these compounds have been reportedly demonstrated health promoting perspectives against a wide range of metabolic syndromes i.e. hyperglycemia, hyperlipidemia, cardiovascular complications, neural disorders, diabetes, and cancer. The high potential of sesquiterpenes and their derivatives against various cancers like breast, colon, bladder, pancreatic, prostate, cervical, brain, liver, blood, ovarium, bone, endometrial, oral, lung, eye, stomach and kidney are the object of this review. Predominantly, it recapitulates the literature elucidating sesquiterpenes and their derivatives while highlighting the mechanistic approaches associated with their potent anticancer activities such as modulating nuclear factor kappa (NF-kB) activity, inhibitory action against lipid peroxidation and retarding the production of reactive oxygen & nitrogen species (ROS&RNS).

Synergistic lethality between PARP-trapping and alantolactone-induced oxidative DNA damage in homologous recombination-proficient cancer cells

PARP1 and PARP2 play critical roles in regulating DNA repair and PARP inhibitors have been approved for the treatment of BRCA1/2-mutated ovarian and breast cancers. It has long been known that PARP inhibition sensitizes cancer cells to DNA-damaging cytotoxic agents independent of BRCA status, however, clinical use of PARP inhibitors in combination with DNA-damaging chemotherapy is limited by the more-than-additive cytotoxicity. The natural compound alantolactone (ATL) inhibits the thioredoxin reductase to induce ROS accumulation and oxidative DNA damage selectively in cancer cells. Here, we showed that nontoxic doses of ATL markedly synergized with the PARP inhibitor olaparib to result in synthetic lethality irrespective of homologous recombination status. Synergistic cytotoxicity was seen in cancer but not noncancerous cells and was reduced by the ROS inhibitor NAC or knockdown of OGG1, demonstrating that the cytotoxicity resulted from the repair of ATL-induced oxidative DNA damage. PARP1 knockdown suppressed the synergistic lethality and olaparib was much more toxic than veliparib when combined with ATL, suggesting PARP-trapping as the primary inducer of cytotoxicity. Consistently, combined use of ATL and olaparib caused intense signs of replication stress and formation of double strand DNA breaks, leading to S and G₂ arrest followed by apoptosis. In vivo, the combination effectively induced regression of tumor xenografts, while either agent alone had no effect. Hence, PARP trapping combined with specific pro-oxidative agents may provide safe and effective ways to broaden the therapeutic potential of PARP inhibitors.

Nanoformulated Codelivery of Quercetin and Alantolactone Promotes an Antitumor Response through Synergistic Immunogenic Cell Death for Microsatellite-Stable Colorectal Cancer

Microsatellite-stable colorectal cancer (CRC) is known to be resistant to immunotherapy. The combination of quercetin (Q) and alantolactone (A) was found to induce synergistic immunogenic cell death (ICD) at a molar ratio of 1:4 (Q:A). To achieve ratiometric loading and delivery, the micellar delivery of Q and A (QA-M) was developed with high entrapment efficiency and drug loading at an optimal ratio. QA-M achieved prolonged blood circulation and increased tumor accumulation for both drugs. More importantly, QA-M retained the desired drug ratio (molar ratio of Q to A = 1:4) in tumors at 2 and 4 h after intravenous injection for synergistic immunotherapy. Tumor growth was significantly inhibited in murine orthotopic CRC by the treatment of QA-M compared to PBS and the combination of free drugs (p < 0.005). The combination of nanotherapy stimulated the host immune response to induce long-term tumor destruction and induced memory tumor surveillance with a 1.3-fold increase in survival median time compared to PBS (p < 0.0001) and a combination of free drugs (p < 0.0005). The synergistic therapeutic effect induced by codelivery of Q and A is capable of reactivating antitumor immunity by inducing ICD, causing cell toxicity and modulating the immune-suppressive tumor microenvironment. Such a combination of Q and A with synergistic effects entrapped in a simple and safe nanodelivery system may provide the potential for scale-up manufacturing and clinical applications as immunotherapeutic agents for CRC.

Activation of PXR by alantolactone ameliorates DSS-induced experimental colitis via suppressing NF-κB signaling pathway

Alantolactone (ALA) is a sesquiterpene lactone with potent anti-inflammatory activity. However, the effect of ALA on intestinal inflammation remains largely unknown. The present study demonstrated that ALA significantly ameliorated the clinical symptoms of dextran sulfate sodium (DSS)-induced mice colitis as determined by body weight loss, diarrhea, colon shortening, inflammatory infiltration and histological injury. In mice exposed to DSS, ALA treatment significantly lowered pro-inflammatory mediators, including nuclear factor-kappa B (NF-κB) activation. In vitro, ALA inhibited NF-κB nuclear translocation and dose-dependently activated human/mouse pregnane X receptor (PXR), a key regulator gene in inflammatory bowel disease (IBD) pathogenesis. However, the pocket occluding mutants of the ligand-binding domain (LBD) of hPXR, abrogated ALA-mediated activation of the receptor. Overexpression of hPXR inhibited NF-κB-reporter activity and in this setting, ALA further enhanced the hPXR-mediated inhibition of NF-κB-reporter activity. Furthermore, silencing hPXR gene demonstrated the necessity for hPXR in downregulation of NF-κB activation by ALA. Finally, molecular docking studies confirmed the binding affinity between hPXR-LBD and ALA. Collectively, the current study indicates a beneficial effect of ALA on experimental IBD possibly via PXR-mediated suppression of the NF-κB inflammatory signaling.

Alantolactone enhances gemcitabine sensitivity of lung cancer cells through the reactive oxygen species-mediated endoplasmic reticulum stress and Akt/GSK3β pathway

Lung cancer is one of the leading causes of cancer-associated mortality in China and globally. Gemcitabine (GEM), as a first-line therapeutic drug, has been used to treat lung cancer, but GEM resistance poses a major limitation on the efficacy of GEM chemotherapy. Alantolactone (ALT), a sesquiterpene lactone compound isolated from Inula helenium, has been identified to exert anticancer activity in various types of cancer, including breast, pancreatic, lung squamous and colorectal cancer. However, the underlying mechanisms of the anticancer activity of ALT in lung cancer remain to be fully elucidated. The present study aimed to determine whether ALT enhances the anticancer efficacy of GEM in lung cancer cells and investigated the underlying mechanisms. The cell viability was assessed with a Cell Counting Kit-8 assay. The cell cycle, apoptosis and the level of reactive oxygen species (ROS) were assessed by flow cytometry, and the expression of cell cycle-associated and apoptosis-associated proteins were determined by western blot analysis. The results demonstrated that ALT inhibited cell growth and induced S-phase arrest and cell apoptosis in A549 and NCI-H520 cells. Furthermore, ALT increased the level of ROS, inhibited the Akt/glycogen synthase kinase (GSK)3β pathway and induced endoplasmic reticulum (ER) stress in A549 and NCI-H520 cells. Additionally, ALT treatment sensitized lung cancer cells to GEM. Analysis of the molecular mechanisms further revealed that ALT enhanced the anticancer effects of GEM via ROS-mediated activation of the Akt/GSK3β and ER stress pathways. In conclusion, combined treatment with ALT and GEM may have potential as a clinical strategy for lung cancer treatment.

Intestinal Absorption of Isoalantolactone and Alantolactone, Two Sesquiterpene Lactones from Radix Inulae, Using Caco-2 Cells

BACKGROUND

Isoalantolactone and alantolactone are the main sesquiterpene lactones in Radix Inulae (dried root of Inula helenium L. or I. racemosa Hook. F.), which is a frequently utilized herbal medicine. They also occur in several plants and have various pharmacologic effects. However, they have been found to have poor oral bioavailability in rats.

OBJECTIVES

To understand the intestinal absorptive characteristics of isoalantolactone and alantolactone as well specific influx and efflux transporters in their absorption.

METHODS

Bidirectional permeabilities of isoalantolactone and alantolactone were investigated across Caco-2 cell monolayers. Transport assays were performed using different concentrations of two lactones and specific inhibitors of ATP-binding cassette transporters and influx transporters.

RESULTS

The absorption permeability of isoalantolactone and alantolactone was high at the tested concentrations (5, 20 and 80 μmol/l), and the major permeation mechanism of both lactones was found to be passive diffusion with active efflux mediated by multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP).

CONCLUSION

Our results demonstrated that the absorption permeability of isoalantolactone and alantolactone was good in the Caco-2 cell model. The isoalantolactone and alantolactone absorption elucidated in this study provides useful information for further pharmacokinetics studies. Since low intestinal absorption can now be ruled out as a cause, further studies are needed to explain the low oral bioavailability of the two sesquiterpene lactones.

Apoptosis-promoting and migration-suppressing effect of alantolactone on gastric cancer cell lines BGC-823 and SGC-7901 via regulating p38MAPK and NF-κB pathways

BACKGROUND

Gastric cancer is a malignant tumor with high incidence rate and mortality rate.

PURPOSE

In this study, we investigated the anti-cancer effect of alantolactone, a sesquiterpene lactone, on gastric cancer cell lines BGC-823 and SGC-7901.

METHODS

BGC-823 and SGC-7901 cells were treated with different concentrations of alantolactone, Hoechst 33258 staining, flow cytometry, wound healing assay, invasion assay, colony forming assay, quantative polymerase chain reaction, and western blot analysis were used to evaluate the anticancer activity of alantolactone to gastric cancer.

RESULTS

Alantolactone induced apoptosis of gastric cancer cells by regulating the expression of Bax, Bcl-2, and p53, which related to intrinsic apoptotic pathway, and suppressed colony formation, migration, and invasion by mediating the expression of matrix metalloproteinase (MMP)-2, MMP-7, and MMP-9. Cell signaling pathway analysis showed that alantolactone enhanced the phosphorylation of p38 and decreased the translocation of nucleus p65, suggesting that the apoptosis-promoting and migration-suppressing effect of alantolactone might at least partially rely on regulating p38 mitogen-activated protein kinase (p38MAPK) pathway and nuclear factor-κB (NF-κB) pathway.

CONCLUSIONS

Alantolactone can be used as a potential therapeutic agent for treating gastric cancer.

Alantolactone induces gastric cancer BGC-823 cell apoptosis by regulating reactive oxygen species generation and the AKT signaling pathway

Alantolactone (ALT), a natural sesquiterpene lactone, has been suggested to exert anti-cancer activities in various cancer cell lines. However, the effects and mechanisms of action of ALT in human gastric cancer remains to be elucidated. In the present study, the effects of ALT on BGC-823 cells were examined and the underlying molecular mechanisms associated with these effects were investigated. Cell viability was detected by using an MTT assay. Cell cycle, cell apoptosis and the level of reactive oxygen species (ROS) were assessed by flow cytometry, and the expression levels of proteins of interest were analyzed by western blot assay. The results demonstrated that ALT triggered apoptosis and induced G0/G1 phase arrest in a dose-dependent manner. Furthermore, the expression level of the anti-apoptosis protein Bcl-2 was downregulated, and expression of the pro-apoptosis proteins Bax and cleaved PARP were significantly upregulated. The cell cycle-associated proteins cyclin-dependent kinase inhibitor 1 and cyclin-dependent kinase inhibitor 1B were also increased, while cyclin D1 was deceased. In addition, ALT induced apoptosis via the inhibition of RAC-alpha serine/threonine-protein kinase (AKT) signaling and ROS generation, which was effectively inhibited by the ROS scavenger, N-acetyl cysteine. Therefore, the results from the present study indicated that the ROS-mediated inhibition of the AKT signaling pathway serves an important role in ALT-induced apoptosis in BGC-823 cells. In conclusion, the results demonstrated that ALT exerted significant anti-cancer effects against gastric cancer cells in vitro.

Alantolactone promotes ER stress-mediated apoptosis by inhibition of TrxR1 in triple-negative breast cancer cell lines and in a mouse model

Triple‐negative breast cancer (TNBC) is a subtype of breast cancer with poor clinical outcome and currently no effective targeted therapies are available. Alantolactone (ATL), a sesquiterpene lactone, has been shown to have potential anti‐tumour activity against various cancer cells. However, the underlying mechanism and therapeutic effect of ATL in the TNBC are largely unknown. In the present study, we found that ATL suppresses TNBC cell viability by reactive oxygen species (ROS) accumulation and subsequent ROS‐dependent endoplasmic reticulum (ER) stress both in vitro and in vivo. Thioredoxin reductase 1 (TrxR1) expression and activity of were significantly up‐regulated in the TNBC tissue specimens compare to the normal adjacent tissues. Further analyses showed that ATL inhibits the activity of TrxR1 both in vitro and in vivo in TNBC and knockdown of TrxR1 in TNBC cells sensitized ATL‐induced cell apoptosis and ROS increase. These results will provide pre‐clinical evidences that ATL could be a potential therapeutic agent against TNBC by promoting ROS‐ER stress‐mediated apoptosis through partly targeting TrxR1.

Alantolactone induces apoptosis and suppresses migration in MCF‑7 human breast cancer cells via the p38 MAPK, NF‑κB and Nrf2 signaling pathways

Human breast cancer is a malignant type of cancer with high prevalence. In the present study, the anticancer effects of alantolactone, a sesquiterpene lactone, on the human breast cancer cell line MCF‑7 were investigated in vitro. The MCF‑7 cell morphology changed from diamond to round subsequent to treatment with alantolactone, and the cell viability reduced significantly compared with that of the control cells. Alantolactone induced apoptosis of MCF‑7 cells by regulating the protein expression levels of B‑cell lymphoma 2 (Bcl‑2), Bcl‑2‑associated X protein, p53, caspase‑3 and caspase‑12, which are associated with the apoptotic pathway, and suppressed colony formation and migration by regulating the protein expression of matrix metalloproteinase (MMP)‑2, MMP‑7 and MMP‑9. Cell signaling pathway analysis confirmed that alantolactone increased the phosphorylation of p38, and decreased the nuclear expression levels of p65 and nuclear factor erythroid 2‑related factor 2 (Nrf2), suggesting that the apoptosis‑promoting and migration‑suppressing effect of alantolactone may partially depend on regulating the p38 MAPK, NF‑κB and Nrf2 pathways. These results also suggested that alantolactone may become a potential therapeutic strategy for treating breast cancer.

Application of sesquiterpene lactone: A new promising way for cancer therapy based on anticancer activity

Cancer is one of the most dangerous diseases that are rapidly increasing globally. After heart disease, it is the second leading cause of death, accounting for seven million deaths each year. Chemotherapy is the use of cytotoxic drugs on cancer cells. But the use of common chemotherapy drugs poses a problem due their high side effects and low efficacy. As a result, efforts are on to find new potent compounds with low side effects. The compounds extracted from plants have been studied in this regard due to their prevalence. Sesquiterpene lactones are a group of natural compounds that were first detected in Asteraceae dark plants. These compounds exercise their effects by reacting with functional groups available on proteins and enzymes, especially the thiol group. Owing to the high side effects as an antitumor synthetic drugs, efforts are being made to find drugs with high efficiency and low side effects. Their high structural ranges have attracted the attention of many researchers as a potential source of new anticancer drugs.

Cinobufagin inhibits tumor growth by inducing intrinsic apoptosis through AKT signaling pathway in human nonsmall cell lung cancer cells

The cinobufagin (CB) has a broad spectrum of cytotoxicity to inhibit cell proliferation of various human cancer cell lines, but the molecular mechanisms still remain elusive. Here we observed that CB inhibited the cell proliferation and tumor growth, but induced cell cycle arrest and apoptosis in a dose-dependent manner in non-small cell lung cancer (NSCLC) cells. Treatment with CB significantly increased the reactive oxygen species but decreased the mitochondrial membrane potential in NSCLC cells. These effects were markedly blocked when the cells were pretreated with N-acetylcysteine, a specific reactive oxygen species inhibitor. Furthermore, treatment with CB induced the expression of BAX but reduced that of BCL-2, BCL-XL and MCL-1, leading to an activation of caspase-3, chromatin condensation and DNA degradation in order to induce programmed cell death in NSCLC cells. In addition, treatment with CB reduced the expressions of p-AKT^T308 and p-AKT^S473 and inhibited the AKT/mTOR signaling pathway in NSCLC cells in a time-dependent manner. Our results suggest that CB inhibits tumor growth by inducing intrinsic apoptosis through the AKT signaling pathway in NSCLC cells.

Alantolactone induces apoptosis of human cervical cancer cells via reactive oxygen species generation, glutathione depletion and inhibition of the Bcl-2/Bax signaling pathway

Alantolactone is the active ingredient in frankincense, and is extracted from the dry root of elecampane. It has a wide variety of uses, including as an insect repellent, antibacterial, antidiuretic, analgesic and anticancer agent. In addition, alantolactone induces apoptosis of human cervical cancer cells, however, its mechanism of action remains to be elucidated. Therefore, the present study investigated whether alantolactone was able to induce apoptosis of human cervical cancer cells, and its potential mechanisms of action were analyzed. Treatment of HeLa cells with alantolactone (0, 10, 20, 30, 40, 50 and 60 µM) for 12 h significantly inhibited growth in a dose-dependent manner. Cells treated with 30 µM of alantolactone for 0, 3, 6 and 12 h demonstrated marked induction of apoptosis in a time-dependent manner. Treatment of HeLa cells with 30 µM of alantolactone for 0, 3, 6 and 12 h significantly induced the generation of reactive oxygen species (ROS) and inhibited glutathione (GSH) production in HeLa cells in a dose-dependent manner. Alantolactone additionally markedly inhibited the Bcl-2/Bax signaling pathway in HeLa cells. Therefore, administration of alantolactone induced apoptosis of human cervical cancer cells via ROS generation, GSH depletion and inhibition of the Bcl-2/Bax signaling pathway.

β-Carotene Induces Apoptosis in Human Esophageal Squamous Cell Carcinoma Cell Lines via the Cav-1/AKT/NF-κB Signaling Pathway

β-carotene, a type of terpenoid, has many metabolic and physiological functions. In particular, β-carotene has an antitumor effect. However, the efficacy of β-carotene against esophageal squamous cell carcinoma (ESCC) remains unclear. In our study, β-carotene inhibited the growth of ESCC cells and downregulated expression of the Caveolin-1 (Cav-1) protein. Cav-1 protein was expressed only in ESCC cells, not in Het-1A cells. Moreover, β-carotene triggered apoptosis, induced cell cycle G0⁄G1 phase arrest, and inhibited cell migration. To explore the mechanism involved in these processes, we further examined the effect of β-carotene on the Cav-1-mediated AKT/NF-κB pathway. The results showed that the level of AKT and NF-κB phosphorylation was dramatically inhibited, which led to an increase in the Bax/Bcl-2 ratio. Correspondingly, the activity of Caspase-3 was also enhanced. These data suggest that β-carotene has an antiproliferative role in ESCC cells and may be a promising chemotherapeutic agent for use against ESCC cells.

Pharmacokinetics, tissue distribution and excretion of isoalantolactone and alantolactone in rats after oral administration of Radix Inulae extract

Radix Inulae is endemic to China and has been used in traditional medicine to treat upper body pain, emesis and diarrhoea, and to eliminate parasites. Here, an UPLC-MS/MS method was developed and applied to study the pharmacokinetics, distribution and excretion of isoalantolactone and alantolactone, which are two main active sesquiterpene lactones in Radix Inulae, in Sprague-Dawley rats following oral administration of total Radix Inulae extract. Isoalantolactone, alantolactone and osthole (internal standard) were prepared using acetonitrile precipitation, and the separation of isoalantolactone and alantolactone was achieved by isocratic elution using water (containing 0.1% formic acid) and acetonitrile as the mobile phase using a ZORBAX Eclipse Plus C18 column. The total run time was 6.4 min. The present study showed poor absorption of isoalantolactone and alantolactone in vivo. The apparent Cmax, Tmax, T1/2 and total exposure (AUC0-12h) in rat plasma were 37.8 ng/mL, 120 min, 351.7 min and 6112.3 ng-min/mL for isoalantolactone and 25.9 ng/mL, 90 min, 321.0 min and 4918.9 ng-min/mL for alantolactone, respectively. It was shown that the highest concentration was achieved in the small intestine and feces clearance was shown to be the dominant elimination pathway of the lactones.