Bigelovin inhibits STAT3 signaling by inactivating JAK2 and induces apoptosis in human cancer cells

Novel drimane-type sesquiterpenoids and nucleosides from the Helicoma septoconstrictum suppress the growth of ovarian cancer cells

Four new drimane-type sesquiterpenoids and two new nucleoside derivatives (1-6), were isolated from the fungus Helicoma septoconstrictum. Their structures were determined based on the combination of the analysis of their HR-ESI-MS, NMR, ECD calculations data and acid hydrolysis. All the isolated compounds were detected for their bio-activities against MDA-MB-231, A549/DDP, A2780 and HepG2 cell lines. Helicoside C (4) exhibited superior cytotoxicity against the A2780 cell line with IC50 7.5 ± 1.5 µM. The analysis of reactive oxygen species (ROS) revealed that Helicoside C induced an increase in intracellular ROS. Furthermore, the flow cytometry and mitochondrial membrane potential (MMP) analyses unveiled that Helicoside C mediated mitochondrial-dependent apoptosis in A2780 cells. The western blotting test showed that Helicoside C could suppress the STAT3's phosphorylation. These findings offered crucial support for development of H. septoconstrictum and highlighted the potential application of drimane-type sesquiterpenoids in pharmaceuticals.

Research progress on antitumor mechanisms and molecular targets of Inula sesquiterpene lactones

The pharmacological effects of natural product therapy have received sigificant attention, among which terpenoids such as sesquiterpene lactones stand out due to their biological activity and pharmacological potential as anti-tumor drugs. Inula sesquiterpene lactones are a kind of sesquiterpene lactones extracted from Inula species. They have many pharmacological activities such as anti-inflammation, anti-asthma, anti-tumor, neuroprotective and anti-allergic. In recent years, more and more studies have proved that they are important candidate drugs for the treatment of a variety of cancers because of its good anti-tumor activity. In this paper, the structure, structure-activity relationship, antitumor activities, mechanisms and targets of Inula sesquiterpene lactones reported in recent years were reviewed in order to provide clues for the development of novel anticancer drugs.

Anticancer Targets and Signaling Pathways Activated by Britannin and Related Pseudoguaianolide Sesquiterpene Lactones

Sesquiterpene lactones (SLs) are abundant in plants and display a large spectrum of bioactivities. The compound britannin (BRT), found in different Inula species, is a pseudoguaianolide-type SL equipped with a typical and highly reactive α-methylene-γ-lactone moiety. The bioproperties of BRT and related pseudoguaianolide SLs, including helenalin, gaillardin, bigelovin and others, have been reviewed. Marked anticancer activities of BRT have been evidenced in vitro and in vivo with different tumor models. Three main mechanisms are implicated: (i) interference with the NFκB/ROS pathway, a mechanism common to many other SL monomers and dimers; (ii) blockade of the Keap1-Nrf2 pathway, with a covalent binding to a cysteine residue of Keap1 via the reactive α-methylene unit of BRT; (iii) a modulation of the c-Myc/HIF-1α signaling axis leading to a downregulation of the PD-1/PD-L1 immune checkpoint and activation of cytotoxic T lymphocytes. The non-specific reactivity of the α-methylene-γ-lactone moiety with the sulfhydryl groups of proteins is discussed. Options to reduce or abolish this reactivity have been proposed. Emphasis is placed on the capacity of BRT to modulate the tumor microenvironment and the immune-modulatory action of the natural product. The present review recapitulates the anticancer effects of BRT, some central concerns with SLs and discusses the implication of the PD1/PD-L1 checkpoint in its antitumor action.

A review of the botany, traditional uses, phytochemistry, and pharmacology of the Flos Inulae

ETHNOPHARMACOLOGICAL RELEVANCE

Plants of the genus Inula have long been used as an ethnomedicine in Asia, Europe, and North America for its high medicinal value and health benefits. Inula japonica Thunb. (I. japonica) and Inula britanica L. (I. britanica) are included in Chinese Pharmacopoeia (2020 edition) as the traditional Chinese medicine Flos inulae (FI). In TCM, FI tastes bitter, pungent, and salt, with warm nature and has the functions of water removal, reduction in nausea, and prevention of vomiting and is often used for cold-related coughs, sputum, wheezing coughs, vomiting, belching and other related diseases. In addition, Inula japonica Thunb is used as a botanical medicine in Korea and Inula britannica L. is also used as a traditional plant medicine in Iran.

AIM OF THE STUDY

This paper collects the relevant research literature (1970-2021) and provides a systematic summary of the botany, ethnopharmacology, processing, phytochemistry, pharmacology, toxicity, analytical methods and quality control of FI to explore its potential and expand its scope for better clinical application.

MATERIALS AND METHODS

Information on Inula japonica Thunb. and Inula britanica L. was collected from scientific databases (1970-2021), including Google Scholar, Baidu Scholar, Springer, PubMed, CNKI and Wan Fang DATA. Information was also collected from classic books of Chinese herbal medicine and Ph.D. and M.Sc. theses.

RESULTS

More than 200 chemical compounds have been isolated from Inula japonica Thunb. and Inula britanica L., including sesquiterpenes, flavonoids, volatile oils, triterpenoids, diterpenoid glycosides, monoterpenoids, polysaccharides, steroid and small molecule acids. Based on a wide variety of chemically active ingredients, FI has a wide range of pharmacological effects. Modern pharmacological research has proven that the pharmacological effects of FI include anti-inflammatory, antitumor, antioxidant, antiallergy, antidiabetic, blood lipid reduction, skin whitening, liver protection, anticonstipation, and antinociceptive effects.

CONCLUSIONS

FI is a very important traditional Chinese herbal medicine with anti-inflammatory antitumor, antioxidant, antiallergy, antidiabetic and other pharmacological effects that can treat a variety of related diseases. This paper summarizes the botany, ethnopharmacology, processing, phytochemistry, pharmacology, toxicity, analytical methods, and quality control of FI. However, the research on the processing, toxicity and quality control of FI is currently too shallow, especially concerning the relationship between the changes in active components before and after processing and the changes in its pharmacological action, which remains unclear. There are few toxicity experiments conducted with FI, so it is impossible to evaluate the safety of FI objectively and impartially. There are also few studies on the material basis and doses of FI causing toxicity and side effects, and more in-depth and concrete researches should be carried out in the future regarding these aspects. Furthermore, to ensure effective and safe clinical medication, we should also pay attention to the mixed use of FI in various regions of China to control the quality of the FI plant.

Usnic acid suppresses cervical cancer cell proliferation by inhibiting PD-L1 expression and enhancing T-lymphocyte tumor-killing activity

The programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) pathway is abnormally expressed in cervical cancer cells. Moreover, PD-1/PD-L1 blockade reduces the apoptosis and exhaustion of T cells and inhibits the development of malignant tumors. Usnic acid is a dibenzofuran compound originating from Usnea diffracta Vain and has anti-inflammatory, antifungal, and anticancer activities. However, the molecular mechanism of its antitumor effects has not been fully elucidated. In this work, we first observed that usnic acid decreased the expression of PD-L1 in HeLa cells and enhanced the cytotoxicity of co-cultured T cells toward tumor cells. Usnic acid inhibited PD-L1 protein synthesis by reducing STAT3 and RAS pathways cooperatively. It was subsequently shown that usnic acid induced MiT/TFE nuclear translocation through the suppression of mTOR signaling pathways, and promoted the biogenesis of lysosomes and the translocation of PD-L1 to the lysosomes for proteolysis. Furthermore, usnic acid inhibited cell proliferation, angiogenesis, migration, and invasion, respectively, by downregulating PD-L1, thereby inhibiting tumor growth. Taken together, our results show that usnic acid is an effective inhibitor of PD-L1 and our study provide novel insights into the mechanism of its anticancer targeted therapy.

Sesquiterpene lactone Bigelovin induces apoptosis of colon cancer cells through inducing IKK-β degradation and suppressing nuclear factor kappa B activation

Bigelovin, a sesquiterpene lactone extracted from plant Inula helianthus aquatica, exhibited multiple interesting biological activities, including anti-inflammation, antiangiogenesis and cytotoxic action against cancer cells. In the present study, we found that Bigelovin reduced the viability of human colon cancer cells and induced their apoptosis in a time- and dose-dependent manner, with an IC50-5 μM. RNAseq and luciferase reporter analyses revealed that the nuclear factor kappa B (NF-κB) signaling was one of the most significantly inhibited pathways after Bigelovin treatment. Further systemic examination showed that exposure to Bigelovin resulted in ubiquitination and degradation of inhibitor of kappa-B kinase-beta (IKK-β) and decrease of IκB-α and p65 phosphorylation, which led to the downregulation of NF-κB-regulated genes expression. Moreover, enforced expression of exogenous IKK-β attenuated Bigelovin-induced NF-κB suppression and cell viability reduction. These results indicated that Bigelovin exerts a cytotoxic action against colon cancer cells through the induction of IKK-β degradation and consequently the inhibition of NF-κB signaling. Given the abnormal activation of NF-κB signaling in colorectal cancer (CRC) cells and the critical role of chronic inflammation in CRC development, it is conceivable that at least some colorectal cancer cells are addictive to NF-κB activation and targeting the pathway is an effective anti-CRC strategy.

Inula L. Secondary Metabolites against Oxidative Stress-Related Human Diseases

An imbalance in the production of reactive oxygen species in the body can cause an increase of oxidative stress that leads to oxidative damage to cells and tissues, which culminates in the development or aggravation of some chronic diseases, such as inflammation, diabetes mellitus, cancer, cardiovascular disease, and obesity. Secondary metabolites from Inula species can play an important role in the prevention and treatment of the oxidative stress-related diseases mentioned above. The databases Scopus, PubMed, and Web of Science and the combining terms Inula, antioxidant and secondary metabolites were used in the research for this review. More than 120 articles are reviewed, highlighting the most active compounds with special emphasis on the elucidation of their antioxidative-stress mechanism of action, which increases the knowledge about their potential in the fight against inflammation, cancer, neurodegeneration, and diabetes. Alantolactone is the most polyvalent compound, reporting interesting EC50 values for several bioactivities, while 1-O-acetylbritannilactone can be pointed out as a promising lead compound for the development of analogues with interesting properties. The Inula genus is a good bet as source of structurally diverse compounds with antioxidant activity that can act via different mechanisms to fight several oxidative stress-related human diseases, being useful for development of new drugs.

PP-22 promotes autophagy and apoptosis in the nasopharyngeal carcinoma cell line CNE-2 by inducing endoplasmic reticulum stress, downregulating STAT3 signaling, and modulating the MAPK pathway

Paris polyphylla var. yunnanensis, named Chong Lou, is considered an antitumor substance. In this study, we investigated the effect of PP-22, a monomer purified from P. polyphylla var. yunnanensis, on the nasopharyngeal carcinoma cell line CNE-2 in vitro. The results showed that PP-22 could inhibit the proliferation of CNE-2 cells via the induction of apoptosis, with evidence of the characteristic morphological changes in the apoptosis in the nucleus and an increase in Annexin V-positive cells. In addition, we found that PP-22 could activate the p38 mitogen-activated protein kinase (MAPK) pathway and that this activation was reversed by SB203580, a specific inhibitor of the p38 MAPK pathway. In contrast, PP-22 promoted apoptosis via an intrinsic pathway, including the endoplasmic reticulum stress pathway, in a caspase-dependent manner. A further study showed that PP-22 also induced apoptosis by downregulating the signal transducers and activators of transcription 3 (STAT3) pathway, and the inhibitory effect was also confirmed by STAT3 small interfering RNA. In addition, PP-22 could promote autophagy by inhibiting the extracellular regulated protein kinases (ERK) pathway. And autophagy plays a protective role against apoptosis. Together, these data show that PP-22 promotes autophagy and apoptosis in the nasopharyngeal carcinoma CNE-2 cell line.

Bigelovin, a sesquiterpene lactone, suppresses tumor growth through inducing apoptosis and autophagy via the inhibition of mTOR pathway regulated by ROS generation in liver cancer

Bigelovin (BigV) is a sesquiterpene lactone, isolated from Inula helianthus aquatica, which has been reported to induce apoptosis and show anti-inflammatory and anti-angiogenic activities. Nevertheless, the effects of BigV on liver cancer and the underlying mechanisms have not been investigated. In the study, we found that BigV exhibited potential anti-tumor activities against human liver cancer in vitro and in vivo. BigV reduced the cell proliferation and colony formation. BigV induced apoptosis through improving the cleavage of Caspase-3 and poly (ADP-ribose) polymerase 1 (PARP-1). The process was along with the activation of autophagy, as proved by the enhanced accumulation of autophagosomes, the microtubule-associated light chain 3B-II (LC3B-II) and Beclin-1, and p62 decrease. Further, the autophagy blockage markedly sensitized BigV-induced cell death, indicating the cytoprotective function of autophagy in liver cancer cell lines. In addition, BigV treatment inactivated the pathway of protein kinase B (AKT)/mammalian target of rapamycin (mTOR)/ribosomal protein S6 kinase (p70S6K). Of note, BigV-induced cell death was abolished by over-expressing the phosphorylation of mTOR. Intriguingly, the induction of apoptosis and autophagy were eliminated by the pretreatment of reactive oxygen species (ROS) scavenger N-acetyl-l-cysteine (NAC), suggesting that ROS played an important role in the regulation of BigV-induced cell death. Finally, in vivo studies demonstrated that BigV significantly suppressed the growth of HepG2 cancer xenograft tumors through the activation of apoptosis and autophagy in a dose-dependent manner with low systemic toxicity. In conclusion, the results revealed that BigV had significant antitumor effects against human liver cancer and it may potentially be used as a novel antitumor agent for the prevention of liver cancer.

Natural small molecule bigelovin suppresses orthotopic colorectal tumor growth and inhibits colorectal cancer metastasis via IL6/STAT3 pathway

Bigelovin, a sesquiterpene lactone, has been demonstrated to induce apoptosis, inhibit inflammation and angiogenesis in vitro, but its potential anti-metastatic activity remains unclear. In the present study, two colon cancer mouse models, orthotopic tumor allografts and experimental metastatic models were utilized to investigate the progression and metastatic spread of colorectal cancer after bigelovin treatments. Results showed that bigelovin (intravenous injection; 0.3-3 mg/kg) significantly suppressed tumor growth and inhibited liver/lung metastasis with modulation of tumor microenvironment (e.g. increased populations of T lymphocytes and macrophages) in orthotopic colon tumor allograft-bearing mice. Furthermore, the inhibitory activities were also validated in the experimental human colon cancer metastatic mouse model. The underlying mechanisms involved in the anti-metastatic effects of bigelovin were then revealed in murine colon tumor cells colon 26-M01 and human colon cancer cells HCT116. Results showed that bigelovin induced cytotoxicity, inhibition of cell proliferation, motility and migration in both cell lines, which were through interfering IL6/STAT3 and cofilin pathways. Alternations of the key molecules including Rock, FAK, RhoA, Rac1/2/3 and N-cadherin, which were detected in bigelovin-treated cancer cells, were also observed in the tumor allografts of bigelovin-treated mice. These findings strongly indicated that bigelovin has potential to be developed as anti-tumor and anti-metastatic agent for colorectal cancer.

The natural sesquiterpene lactones arglabin, grosheimin, agracin, parthenolide, and estafiatin inhibit T cell receptor (TCR) activation

Inhibition of the T cell receptor (TCR) pathway represents an effective strategy for the treatment of T cell-mediated inflammatory and autoimmune diseases. To identify natural compounds that could inhibit inflammatory T cell responses, we screened 13 sesquiterpene lactones, including achillin, arglabin, argolide, argracin, 3β-hydroxyarhalin, artesin, artemisinin, estafiatin, grosheimin, grossmisin, leucomisine, parthenolide, and taurine, for their ability to modulate activation-induced Ca²⁺ mobilization in Jurkat T cells. Five of the compounds (arglabin, grosheimin, argracin, parthenolide, and estafiatin) inhibited anti-CD3-induced mobilization of intercellular Ca²⁺ ([Ca²⁺]_i) in Jurkat cells, with the most potent being parthenolide and argacin (IC₅₀ = 5.6 and 6.1 μM, respectively). Likewise, phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 in activated Jurkat cells was inhibited by these five compounds, with the most potent being parthenolide and estafiatin (IC₅₀ = 13.8 and 15.4 μM, respectively). These compounds also inhibited ERK1/2 phosphorylation in primary human T cells and depleted intracellular glutathione. In contrast, none of the sesquiterpene lactones inhibited ERK1/2 phosphorylation in HL60 cells transfected with N-formyl peptide receptor 2 (FPR2) and stimulated with the FPR2 peptide agonist WKYMVM, indicating specificity for T cell activation. Estafiatin, a representative sesquiterpene lactone, was also profiled in a cell-based phosphokinase array for 43 kinase phosphorylation sites, as well as in a cell-free competition binding assay for its ability to compete with an active-site directed ligand for 95 different protein kinases. Besides inhibition of ERK1/2 phosphorylation, estafiatin also inhibited phosphorylation of p53, AMPKα1, CREB, and p27 elicited by TCR activation in Jurkat cells, but it did not bind to any of 95 kinases evaluated. These results suggest that arglabin, grosheimin, agracin, parthenolide, and estafiatin can selectively inhibit initial phases of TCR activation and may be natural compounds with previously undescribed immunotherapeutic properties.

Study on the mechanism of JAK2/STAT3 signaling pathway-mediated inflammatory reaction after cerebral ischemia

The present study aimed to investigate the mechanism by which the Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)3 signaling pathway mediates cerebral ischemia and the efficacy of pharmaceutical intervention. The rat model of middle cerebral artery occlusion (MCAO) was established and confirmed via assessment of changes in the expression of phosphorylated (p)‑JAK2, p‑STAT3, high‑mobility group box 1 (HMGB1), and inflammatory factors using ELISA and western blot analysis. The effects of JAK2/STAT3 inhibitor and curcumin on the expression of p‑JAK2, p‑STAT3, HMGB1, and inflammatory factors after cerebral ischemia were observed with ELISA, western blotting and immunohistochemical staining. The concentrations of tumor necrosis factor (TNF)‑α and HMGB1 in brain tissue homogenate of MCAO group were significantly higher than in the sham group (P<0.01). The concentration of p‑JAK2/JAK2 and p‑STAT3/STAT3 in the brain tissue homogenate of MCAO group was significantly higher than in the sham group (P<0.05). The concentrations of TNF‑α, interleukin (IL)‑1β, IL‑6, and HMGB1 in the group treated with STAT3 inhibitor (MCAO + rapamycin), JAK2 inhibitor (MCAO + AG490), and MCAO + curcumin were significantly lower than in the MCAO group (P<0.01), as well as the relative content of p‑JAK2/JAK2 and p‑STAT3/STAT3 (P<0.05). Inhibition of the JAK2/STAT3 signaling pathway, such as curcumin can reduce the expression of HMGB1 in brain tissue after cerebral ischemia, which can significantly reduce the inflammatory response after cerebral ischemia.

Bigelovin triggered apoptosis in colorectal cancer in vitro and in vivo via upregulating death receptor 5 and reactive oxidative species

Colorectal cancer (CRC) is the third most prevalent cancer and the third highest cancer-related mortality in the United States. Bigelovin, a sesquiterpene lactone isolated from Inula helianthus aquatica, has been proven to induce apoptosis and exhibit anti-inflammatory and anti-angiogenic activities. However, the effects of bigelovin on CRC and underlying mechanisms have not been explored. The present study demonstrated that bigelovin exhibited potent anti-tumor activities against CRC in vitro and in vivo. Bigelovin suppressed cell proliferation and colony formation and induced apoptosis in human colorectal cancer HT-29 and HCT 116 cells in vitro. Results also revealed that bigelovin activated caspases, caused the G2/M cell cycle arrest and induced DNA damage through up-regulation of death receptor (DR) 5 and increase of ROS. In HCT 116 xenograft model, bigelovin treatment resulted in suppression of tumor growth. Bigelovin at 20 mg/kg showed more significant tumor suppression and less side effects than conventional FOLFOX (containing folinic acid, 5-fluorouracil and oxaliplatin) treatment. In addition, in vivo data confirmed that anti-tumor activity of bigelovin in CRC was through induction of apoptosis by up-regulating DR5 and increasing ROS. In conclusion, these results strongly suggested that bigelovin has potential to be developed as therapeutic agent for CRC patients.

Inhibition of cerebral ischemia/reperfusion injury-induced apoptosis: nicotiflorin and JAK2/STAT3 pathway

Nicotiflorin is a flavonoid extracted from Carthamus tinctorius. Previous studies have shown its cerebral protective effect, but the mechanism is undefined. In this study, we aimed to determine whether nicotiflorin protects against cerebral ischemia/reperfusion injury-induced apoptosis through the JAK2/STAT3 pathway. The cerebral ischemia/reperfusion injury model was established by middle cerebral artery occlusion/reperfusion. Nicotiflorin (10 mg/kg) was administered by tail vein injection. Cell apoptosis in the ischemic cerebral cortex was examined by hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Bcl-2 and Bax expression levels in ischemic cerebral cortex were examined by immunohistochemial staining. Additionally, p-JAK2, p-STAT3, Bcl-2, Bax, and caspase-3 levels in ischemic cerebral cortex were examined by western blot assay. Nicotiflorin altered the shape and structure of injured neurons, decreased the number of apoptotic cells, down-regulates expression of p-JAK2, p-STAT3, caspase-3, and Bax, decreased Bax immunoredactivity, and increased Bcl-2 protein expression and immunoreactivity. These results suggest that nicotiflorin protects against cerebral ischemia/reperfusion injury-induced apoptosis via the JAK2/STAT3 pathway.

Synergistic effects of the sesquiterpene lactone, EPD, with cisplatin and paclitaxel in ovarian cancer cells

BACKGROUND

Ovarian cancer remains still the leading cause of death of gynecological malignancy, in spite of first-line chemotherapy with cisplatin and paclitaxel. Although initial response is favorably, relapses are common and prognosis for women with advanced disease stays poor. Therefore efficacious approaches are needed.

METHODS

Previously, an anti-cancer agent, EPD exhibited potent cytotoxic effects towards ovarian cancer and not towards normal cells. Cell viability and cell cycle analysis studies were performed with EPD, in combination with cisplatin and/or paclitaxel, using the ovarian carcinoma cell lines: SK-OV-3, OVCAR-3, JC, JC-pl and normal fibroblasts. Cell viability was measured using Presto Blue and cell cycle analysis using a flow cytometer. Apoptosis was measured in JC and JC-pl , using the caspase 3 assay kit.

RESULTS

In JC-pl, SK-OV-3 and JC, synergistic interactions between either EPD and cisplatin or EPD and paclitaxel were observed. For the first time the effects of EPD on the cell cycle of ovarian cancer cells and normal cells was studied. EPD and combinations of EPD with cisplatin and/ or paclitaxel showed cell cycle arrest in the G2/M phase. The combination of EPD and cisplatin showed a significant synergistic effect in cell line JC-pl, while EPD with paclitaxel showed synergistic interaction in JC. Additionally, synergistic drug combinations showed increased apoptosis.

CONCLUSIONS

Our results showed a synergistic effect of EPD and cisplatin in an ovarian drug resistant cell line as well as a synergistic effect of EPD and paclitaxel in two other ovarian cell lines. These results might enhance clinical efficacy, compared to the existing regimen of paclitaxel and cisplatin.