Arctigenin inhibits STAT3 and exhibits anticancer potential in human triple-negative breast cancer therapy

Potential therapeutic targets of the JAK2/STAT3 signaling pathway in triple-negative breast cancer

Triple-negative breast cancer (TNBC) poses a significant clinical challenge due to its propensity for metastasis and poor prognosis. TNBC evades the body's immune system recognition and attack through various mechanisms, including the Janus Kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. This pathway, characterized by heightened activity in numerous solid tumors, exhibits pronounced activation in specific TNBC subtypes. Consequently, targeting the JAK2/STAT3 signaling pathway emerges as a promising and precise therapeutic strategy for TNBC. The signal transduction cascade of the JAK2/STAT3 pathway predominantly involves receptor tyrosine kinases, the tyrosine kinase JAK2, and the transcription factor STAT3. Ongoing preclinical studies and clinical research are actively investigating this pathway as a potential therapeutic target for TNBC treatment. This article comprehensively reviews preclinical and clinical investigations into TNBC treatment by targeting the JAK2/STAT3 signaling pathway using small molecule compounds. The review explores the role of the JAK2/STAT3 pathway in TNBC therapeutics, evaluating the benefits and limitations of active inhibitors and proteolysis-targeting chimeras in TNBC treatment. The aim is to facilitate the development of novel small-molecule compounds that target TNBC effectively. Ultimately, this work seeks to contribute to enhancing therapeutic efficacy for patients with TNBC.

Novel (-)-arctigenin derivatives inhibit signal transducer and activator of transcription 3 phosphorylation and P-glycoprotein function resensitizing multidrug resistant cancer cells in vitro and in vivo

Multidrug resistance (MDR) is considered one of the significant chemotherapy failures of cancer patients and resulting in tumor recurrence and refractory cancer. The collateral sensitivity phenomenon is suggested as a potential alternative therapy for coring multidrug resistance in cancer. To achieve better effects and reduce toxicity, a polypharmacology strategy was applied. Arctigenin has been reported as a signal transducer and activator of transcription 3 (STAT3) inhibitor as an anticancer drug with low toxicity. However, the effective dosage of arctigenin was too high for re-sensitization in MDR cell lines. Therefore, we have designed and synthesized arctigenin derivatives and have evaluated their chemoreversal effects in KBvin and KB cells. The results conveyed that compounds 9, 10, and 12 displayed significant collateral sensitivity effects on MDR cancer cells, and the corresponding calculated RF values were 32, 174, and 133, respectively. In addition, compounds 9, 10, and 12 were identified to influence the activation of STAT3 and the function of P-glycoprotein in KBvin cells. Combining the active compounds (9, 10, and 12) with paclitaxel significantly inhibits MDR tumor growth in a zebrafish xenograft tumor model without toxicity. Thus, this study provided novel effective arctigenin derivatives and is considered a potential co-treatment with paclitaxel for treating MDR tumors.

Polyphyllin VII induces autophagy-dependent ferroptosis in human gastric cancer through targeting T-lymphokine-activated killer cell-originated protein kinase

T-lymphokine-activated killer cell-originated protein kinase (TOPK) is a serine-threonine kinase that is overexpressed in gastric cancer (GC) and promotes tumor progression. Polyphyllin VII (PPVII), a pennogenin isolated from the rhizomes of Paris polyphylla, shows anticancer effects. Here, we explored the antitumor activity and mechanism of PPVII in GC. Ferroptosis was detected by transmission electron microscope, malondialdehyde, and iron determination assays. Autophagy and its upstream signaling pathway were detected by Western blot, and gene alterations. The binding of PPVII and TOPK was examined through microscale thermophoresis and drug affinity responsive target stability assays. An in vivo mouse model was performed to evaluate the therapeutic of PPVII. PPVII inhibits GC by inducing autophagy-mediated ferroptosis. PPVII promotes the degradation of ferritin heavy chain 1, which is responsible for autophagy-mediated ferroptosis. PPVII activates the Unc-51-like autophagy-activating kinase 1 (ULK1) upstream of autophagy. PPVII inhibits the activity of TOPK, thereby weakening the inhibition of downstream ULK1. PPVII stabilizes the dimer of the inactive form of TOPK by direct binding. PPVII inhibits tumor growth without causing obvious toxicity in vivo. Collectively, this study suggests that PPVII is a potential agent for the treatment of GC by targeting TOPK to activate autophagy-mediated ferroptosis.

Methoxyhispolon Methyl Ether, a Hispolon Analog, Thwarts the SRC/STAT3/BCL-2 Axis to Provoke Human Triple-Negative Breast Cancer Cell Apoptosis In Vitro

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with few treatment options. A promising TNBC treatment approach is targeting the oncogenic signaling pathways pivotal to TNBC initiation and progression. Deregulated activation of signal transducer and activator of transcription 3 (STAT3) is fundamental to driving TNBC malignant transformation, highlighting STAT3 as a promising TNBC therapeutic target. Methoxyhispolon Methyl Ether (MHME) is an analog of Hispolon, an anti-cancer polyphenol found in the medicinal mushroom Phellinus linteus. Still, MHME's anti-cancer effects and mechanisms remain unknown. Herein, we present the first report about MHME's anti-TNBC effect and its action mechanism. We first revealed that MHME is proapoptotic and cytotoxic against human TNBC cell lines HS578T, MDA-MB-231, and MDA-MB-463 and displayed a more potent cytotoxicity than Hispolon's. Mechanistically, MHME suppressed both constitutive and interleukin 6 (IL-6)-induced activation of STAT3 represented by the extent of tyrosine 705-phosphorylated STAT3 (p-STAT3). Notably, MHME-evoked apoptosis and clonogenicity impairment were abrogated in TNBC cells overexpressing a dominant-active mutant of STAT3 (STAT3-C); supporting the blockade of STAT3 activation is an integral mechanism of MHME's cytotoxic action on TNBC cells. Moreover, MHME downregulated BCL-2 in a STAT3-dependent manner, and TNBC cells overexpressing BCL-2 were refractory to MHME-induced apoptosis, indicating that BCL-2 downregulation is responsible for MHME's proapoptotic effect on TNBC cells. Finally, MHME suppressed SRC activation, while v-src overexpression rescued p-STAT3 levels and downregulated apoptosis in MHME-treated TNBC cells. Collectively, we conclude that MHME provokes TNBC cell apoptosis through the blockade of the SRC/STAT3/BCL-2 pro-survival axis. Our findings suggest the potential of applying MHME as a TNBC chemotherapy agent.

Sculponeatin A promotes the ETS1-SYVN1 interaction to induce SLC7A11/xCT-dependent ferroptosis in breast cancer

BACKGROUND

E26 transformation specificity-1 (ETS1) is a transcription factor that is overexpressed in breast cancer (BC) and promotes tumor progression. Sculponeatin A (stA), a new diterpenoid extracted from Isodon sculponeatus, has no reported antitumor mechanism.

PURPOSE

Here, we explored the antitumor activity of stA in BC and further clarified its mechanism.

METHODS

Ferroptosis was detected by flow cytometric, glutathione, malondialdehyde, and iron determination assays. The effect of stA on the upstream signaling pathway of ferroptosis was detected by Western blot, gene expression, gene alterations and other approaches. The binding of stA and ETS1 was examined through a microscale thermophoresis assay and a drug affinity responsive target stability assay. An in vivo mouse model experiment was performed to evaluate the therapeutic and potential mechanism of stA.

RESULTS

stA exhibits therapeutic potential in BC by inducing SLC7A11/xCT-dependent ferroptosis. stA decreases the expression of ETS1, which is responsible for xCT-dependent ferroptosis in BC. stA inhibits the transcriptional expression of xCT by directly binding to the ETS domain of the ETS1 protein. In addition, stA promotes proteasomal degradation of ETS1 by triggering ubiquitin ligase synoviolin 1 (SYVN1)-mediated ubiquitination. The K318 site of ETS1 mediates ubiquitination of ETS1 by SYVN1. In a mouse model, stA inhibits tumor growth without causing obvious toxicity.

CONCLUSION

Taken together, the results confirm that stA promotes the ETS1-SYVN1 interaction to induce ferroptosis in BC mediated by ETS1 degradation. stA is expected to be used in research of candidate drugs for BC and drug design based on ETS1 degradation.

A systematic review on botany, ethnopharmacology, quality control, phytochemistry, pharmacology and toxicity of Arctium lappa L. fruit

ETHNOPHARMACOLOGICAL RELEVANCE

Arctium lappa L., is a biennial plant that grows around the Eurasia. Many parts of Arctium lappa L. (roots, leaves and fruits, etc.) are medically used in different countries. Arctium lappa L. fruit, also called Arctii Fructus, is traditionally applied to dispel wind-heat, ventilate lung to promote eruption, remove toxicity substance and relieve sore throat.

THE AIM OF THE REVIEW

The review aims to integrate the botany, ethnopharmacology, quality control, phytochemistry, pharmacology, derivatives and toxicity information of Arctii Fructus, so as to facilitate future research and explore the potential of Arctii Fructus as an agent for treating diseases.

MATERIALS AND METHODS

Related knowledge about Arctii Fructus were acquired from Science Direct, GeenMedical, PubMed, China National Knowledge Infrastructure (CNKI), Web of Science, Pharmacopoeia of the People's Republic of China, Doctoral and Master's thesis, ancient books, etc. RESULTS: Arctii Fructus as an herb used for medicine and food was pervasively distributed and applicated around the world. It was traditionally used to treat anemopyretic cold, dyspnea and cough, sore throat, etc. To date, more than 200 compounds have been isolated and identified from Arctii Fructus. It contained lignans, phenolic acids and fatty acids, terpenoids, volatile oils and others. Lignans, especially arctigenin and arctiin, had the extensive pharmacological effects such as anti-cancer, antiviral, anti-inflammatory activities. The ester derivatives of arctigenin had the anti-cancer, anti-Alzheimer's disease and immunity enhancing effects. Although Arctii Fructus extract had no toxicity, arctigenin was toxic at a certain dose. The alleviating effects of Arctii Fructus on chronic inflammation and ageing have been demonstrated by clinical studies.

CONCLUSION

Arctii Fructus is regarded as a worthy herb with many chemical components and various pharmacological effects. Several traditional applications have been supported by modern pharmacological research. However, their action mechanisms need to be further studied. Although many chemical components were isolated from Arctii Fructus, the current research mainly focused on lignans, especially arctiin and arctigenin. Therefore, it is very important to deeply clarify the pharmacological activities and action mechanism of the compounds and make full medicinal use of the resources of Arctii Fructus.

Compounds from diverse natural origin against triple-negative breast cancer: A comprehensive review

Triple-negative breast cancer (TNBC) is caused due to the lack of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor 2 (HER2) expression. Triple-negative breast cancer is the most aggressive heterogeneous disease that is capable of producing different clones and mutations. Tumorigenesis in TNBC is caused due to the mutation or overexpression of tumor suppressor genes. It is also associated with mutations in the BRCA gene which is linked to hereditary breast cancer. In addition, PARP proteins and checkpoint proteins also play a crucial function in causing TNBC. Many cell signaling pathways are dysregulated in TNBC. Even though chemotherapy and immunotherapy are good options for TNBC treatment, the response rates are still low in general. Many phytochemicals that are derived from natural compounds have shown very good inhibitions for TNBC. Natural compounds have the great advantage of being less toxic, having lesser side effects, and being easily available. The secondary metabolites such as alkaloids, terpenoids, steroids, and flavonoids in natural products make them promising inhibitors of TNBC. Their compositions also offer vital insights into inhibitory action, which could lead to new cancer-fighting strategies. This review can help in understanding how naturally occurring substances and medicinal herbs decrease specific tumors and pave the way for the development of novel and extremely efficient antitumor therapies.

Preliminary study on the role and mechanism of KIRREL3 in the development of esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a common malignant tumor of the digestive tract, which is very harmful to human health. The JAK-STAT signaling pathway is a recognized carcinogenic pathway that plays a role in the proliferation, apoptosis, migration, and invasion of a variety of cancer cells. Some studies have shown that the activation status of STAT3 affects the expression of KIRREL3. However, the expression of KIRREL3 in ESCC and its relationship with KIRREL3 or the JAK-STAT signaling pathway is still unclear.

METHODS

In this study, we used immunohistochemistry and western blotting to analyze the protein expression levels of KIRREL3 in tumor tissues and ESCC cell lines. We applied proliferation assays, plate clone formation assays, Transwell assays, flow cytometry analysis, and CDX animal models to examine the role of KIRREL3 in ESCC.

RESULTS

The results indicate that KIRREL3 is highly expressed to varying degrees in ESCC tissues and cell lines. Knocking down KIRREL3 expression in ESCC cells could correspondingly inhibit cell proliferation, colony formation, invasion, and migration, and had some effects on cell cycle progression and apoptosis. In addition, overexpressing KIRREL3 in these cells had opposite effects. Tumor formation in nude mice experiments also confirmed that KIRREL3 is involved in the growth of ESCC cells in vivo.

CONCLUSIONS

These data suggest that KIRREL3 plays a key role in the development of ESCC, and KIRREL3 is a potential new target for the early diagnosis and clinical treatment of this disease.

Benzobis(imidazole) derivatives as STAT3 signal inhibitors with antitumor activity

Polycyclic aromatic systems have been considered good biological probes, but some may also be good scaffolds for drug development. In this study, a series of benzobis(imidazole) derivatives were identified as STAT3 signal inhibitors, among which compound 24 showed significant inhibition of IL-6 induced JAK/STAT3 signalling pathway activation. Moreover, 24 inhibited cancer cell growth and migration, and induced cell apoptosis as well as cycle arrest in human hepatocellular carcinoma cells (HepG2) and oesophageal carcinoma cells (EC109). Compound 24 also displayed obvious antitumor activity in a mouse HepG2 cell xenograft tumor model without affecting the body weight. These results confirmed that 24 was a potential STAT3 signal inhibitor with certain antitumor activity.

A comprehensive insight into the antineoplastic activities and molecular mechanisms of deoxypodophyllotoxin: Recent trends, challenges, and future outlook

Lignans constitute an important group of polyphenols, which have been demonstrated to potently suppress cancer cell proliferation. Numerous in vitro and in vivo studies indicate that deoxypodophyllotoxin as a natural lignan possesses potent anticancer activities against various types of human cancer. The purpose of current review is to provide the reader with the latest findings in understanding the anticancer effects and molecular mechanisms of deoxypodophyllotoxin. This review comprehensively describes the influence of deoxypodophyllotoxin on signaling cascades and molecular targets implicated in cancer cell proliferation and invasion. A number of various signaling molecules and pathways, including apoptosis, necroptosis, cell cycle, angiogenesis, vascular disruption, ROS, MMPs, glycolysis, and microtubules as well as NF-κB, PI3K/Akt/mTOR, and MAPK cascades have been reported to be responsible for the anticancer activities of deoxypodophyllotoxin. The results of present review suggest that the cyclolignan deoxypodophyllotoxin can be developed as a novel and potent anticancer agent, especially as an alternative option for treatment of resistant tumors to chemotherapy.

Therapeutic potential of naturally occurring lignans as anticancer agents

Cancer as a long-lasting and dramatic pandemic affects almost a third of the human being worldwide. At present, chemotherapy is the main clinical treatment strategy, but it is difficult to achieve satisfactory efficacy due to drug resistance and side effects. Natural products are becoming increasingly popular in cancer therapy due to their potent broad-spectrum anticancer potency and slight side effects. Lignans are complex diphenolic compounds, comprising a family of secondary metabolites existing widely in plants. Naturally occurring lignans have the potential to act on cancer cells by a range of mechanisms of action and could inhibit the colony formation, arrest the cell cycle in different phases, induce apoptosis, and suppress migration, providing privileged scaffolds for the discovery of novel anticancer agents. In recent five years, a variety of naturally occurring lignans were isolated and screened for their in vitro and/or in vivo anticancer efficacy, and some of them exhibited promising potential. This review has systematically summarized the resources, anticancer activity, and mechanisms of action of naturally occurring lignans, covering articles published between January 2017 and January 2022.

Novel inhibitors of the STAT3 signaling pathway: an updated patent review (2014-present)

INTRODUCTION

STAT3 is a critical transcription factor that transmits signals from the cell surface to the nucleus, thus influencing the transcriptional regulation of some oncogenes. The inhibition of the activation of STAT3 is considered a promising strategy for cancer therapy. Numerous STAT3 inhibitors bearing different scaffolds have been reported to date, with a few of them having been considered in clinical trials.

AREAS COVERED

This review summarizes the advances on STAT3 inhibitors with different structural skeletons, focusing on the structure-activity relationships in the related patent literature published from 2014 to date.

EXPERT OPINION

Since the X-ray crystal structure of STAT3β homo dimer bound to DNA was solved in 1998, the development of STAT3 inhibitors has gone through a boom in recent years. However, none of them have been approved for marketing, probably due to the complex biological functions of the STAT3 signaling pathway, including its character and the poor drug-like physicochemical properties of its inhibitors. Nonetheless, targeting STAT3 continues to be an exciting field for the development of anti-tumor agents along with the emergence of new STAT3 inhibitors with unique mechanisms of action.

Combinatorial Effects of the Natural Products Arctigenin, Chlorogenic Acid, and Cinnamaldehyde Commit Oxidation Assassination on Breast Cancer Cells

Major obstacles in current breast cancer treatment efficacy include the ability of breast cancer cells to develop resistance to chemotherapeutic drugs and the off-target cytotoxicity of these drugs on normal cells, leading to debilitating side effects. One major difference between cancer and normal cells is their metabolism, as cancer cells acquire glycolytic and mitochondrial metabolism alterations throughout tumorigenesis. In this study, we sought to exploit this metabolic difference by investigating alternative breast cancer treatment options based on the application of phytochemicals. Herein, we investigated three phytochemicals, namely cinnamaldehyde (CA), chlorogenic acid (CGA), and arctigenin (Arc), regarding their anti-breast-cancer properties. These phytochemicals were administered alone or in combination to MCF-7, MDA-MB-231, and HCC1419 breast cancer or normal MCF-10A and MCF-12F breast cells. Overall, our results indicated that the combination treatments showed stronger inhibitory effects on breast cancer cells versus single treatments. However, only treatments with CA (35 μM), CGA (250 μg/mL), and the combination of CA + CGA (35 μM + 250 μg/mL) showed no significant cytotoxic effects on normal mammary epithelial cells, suggesting that Arc was the driver of normal cell cytotoxicity in all other treatments. CA + CGA and, to a lesser extent, CGA alone effectively induced breast cancer cell death accompanied by decreases in mitochondrial membrane potential, increased mitochondrial superoxide, reduced mitochondrial and glycolytic ATP production, and led to significant changes in cellular and mitochondrial morphology. Altogether, the combination of CA + CGA was determined as the best anti-breast-cancer treatment strategy due to its strong anti-breast-cancer effects without strong adverse effects on normal mammary epithelial cells. This study provides evidence that targeting the mitochondria may be an effective anticancer treatment, and that using phytochemicals or combinations thereof offers new approaches in treating breast cancer that significantly reduce off-target effects on normal cells.

Repurposing drugs as novel triple negative breast cancer therapeutics

BACKGROUND

Among all the types of breast cancer (BC), triple negative breast cancer (TNBC) is the most aggressive form having high metastasis and recurrence rate with limited treatment options. Conventional treatments such as chemotherapy and radiotherapy have lots of toxic side effects and also no FDA approved therapies are available till now. Repurposing of old clinically approved drugs towards various targets of TNBC is the new approach with lesser side effects and also leads to successful inexpensive drug development with less time consuming. Medicinal plants containg various phytoconstituents (flavonoids, alkaloids, phenols, essential oils, tanins, glycosides, lactones) plays very crucial role in combating various types of diseases and used in drug development process because of having lesser side effects.

OBJECTIVE

The present review focuses in summarization of various categories of repurposed drugs against multitarget of TNBC and also summarizes the phytochemical categories that targets TNBC singly or in combination with synthetic old drugs.

METHODS

Literature information was collected from various databases such as Pubmed, Web of Science, Scopus and Medline to understand and clarify the role and mechanism of repurposed synthetic drugs and phytoconstituents aginst TNBC by using keywords like "breast cancer", "repurposed drugs", "TNBC" and "phytoconstituents".

RESULTS

Various repurposed drugs and phytochemicals targeting different signaling pathways that exerts their cytotoxic activities on TNBC cells ultimately leads to apoptosis of cells and also lowers the recurrence rate and stops the metastasis process.

CONCLUSION

Inhibitory effects seen in different levels, which provides information and evidences to researchers towards drug developments process and thus further more investigations and researches need to be taken to get the better therapeutic treatment options against TNBC.

Fructus arctii: an overview on its traditional uses, pharmacology and phytochemistry

OBJECTIVES

Fructus arctii (F. arctii) is the dried ripe fruit of Arctium lappa Willd (Asteraceae). It is being used as a traditional medicine in China, Japan, Iran, Europe, Afghanistan, India, etc. for cough, inflammation, clearing the heat, detoxification, cancer and diabetes. This review summarized the botanical description, distribution, ethnopharmacology, bioactive constituents and pharmacological actions of F. arctii including methods to assess its quality. In addition, this review also provides insights into future research directions on F. arctii to further explore its bioactive constituents, mechanism involved in pharmacological activity, and clinical use including the development of new analytical methods for assessing the quality.

KEY FINDINGS

The comprehensive analysis of the literature revealed that F. arctii contains lignans, volatile oil, flavonoids, sesquiterpenoids, triterpenes, phenolic acids, etc. Experimental studies on various extracts and drug formulations showed that it has antioxidant, antimicrobial, hypoglycaemic, lipid-lowering, anti-inflammatory, analgesic, antiviral, anti-tumour activity, etc.

SUMMARY

The pharmacological activity of a few major constituents in F. arctii have been identified. However, there are still need more studies and more new technologies to prove the pharmacological activity and the effective mechanism of the other constituents that undergoing uncertain. Except for the animal experiments, clinical studies should be carried out to provide the evidence for clinical application.

Arctigenin, an anti-tumor agent; a cutting-edge topic and up-to-the-minute approach in cancer treatment

Today, herbal-derived compounds are being increasingly studied in cancer treatment. Over the past decade, Arctigenin has been introduced as a bioactive dibenzylbutyrolactone lignan which is found in Chinese herbal medicines. In addition to anti-microbial, anti-inflammatory, immune-modulatory functions, Arctigenin has attracted growing attention due to its anti-tumor capabilities. It has been shown that Arctigenin can induce apoptosis and necrosis and abolish drug resistance in tumor cells by inducing apoptotic signaling pathways, caspases, cell cycle arrest, and the modulating proteasome. Moreover, Arctigenin mediates other anti-tumor functions through several mechanisms. It has been demonstrated that Arctigenin can act as an anti-inflammatory compound to inhibit inflammation in the tumor microenvironment. It also downregulates factors involved in tumor metastasis and angiogenesis, such as matrix metalloproteinases, N-cadherin, TGF-β, and VEGF. Additionally, Arctigenin, through modulation of MAPK signaling pathways and stress-related proteins, is able to abolish tumor cell growth in nutrient-deprived conditions. Due to the limited solubility of Arctigenin in water, it is suggested that modification of this compound through amino acid esterification can improve its pharmacogenetic properties. Collectively, it is hoped that using Arctigenin or its derivates might introduce new chemotherapeutic approaches in future treatment.

Arctigenin inhibits human breast cancer cell proliferation, migratory and invasive abilities and epithelial to mesenchymal transition by targeting 4EBP1

Breast cancer (BC) is one of the most common types of cancer with the highest morbidity rate amongst all cancers in women worldwide. Arctigenin is isolated from the seeds of Asteraceae lappa and exhibits anti-inflammatory and anti-viral effects. The present study aimed to investigate the effect of arctigenin on BC cells and to explore the regulation of arctigenin on eukaryotic translation initiation factor 4E binding protein 1 (4EBP1) expression. To do so, MDA-MB-231 and BT549 cells were treated with arctigenin at various concentrations (0, 5, 10, 20 and 40 µM). Cells treated with 40 µM arctigenin were transfected with pcDNA3.1-4EBP1 or NC control. Cell Counting Kit-8 assay was used to determine cell proliferation, reverse transcription quantitative PCR was used to evaluate the transfection efficiency, western blotting was used to detect relative protein expression and Transwell assays were performed to evaluate the migratory and invasive abilities of BC cells. The results demonstrated that arctigenin could inhibit the proliferation, migratory and invasive abilities, and epithelial to mesenchymal transition (EMT) of MDA-MB-231 and BT549 cells. Furthermore, arctigenin downregulated the expression of 4EBP1 in MDA-MB-231 and BT549 cells, whereas 4EBP1 overexpression could reverse the inhibiting effect of arctigenin on proliferation, migratory and invasive abilities, and EMT in MDA-MB-231 and BT549 cells. The findings suggested that arctigenin may inhibit human BC cell proliferation, migratory and invasive abilities, and EMT by targeting 4EBP1.

A comprehensive mechanistic insight into the dietary and estrogenic lignans, arctigenin and sesamin as potential anticarcinogenic and anticancer agents. Current status, challenges, and future perspectives

A large body of evidence indicates that lignans as polyphenolic compounds are beneficial against life-threatening diseases such as cancer. Plant lignans have the potential to induce cancer cell death and interfere with carcinogenesis, tumor growth, and metastasis. Epidemiological studies have revealed that the intake of lignans is inversely associated with the risk of several cancers. Moreover, numerous experimental studies demonstrate that natural lignans significantly suppress cancer cell proliferation with minimal toxicity against non-transformed cells. Dietary lignans arctigenin and sesamin have been found to have potent antiproliferative activities against various types of human cancer. The purpose of this review is to provide the reader with a deeper understanding of the cellular and molecular mechanisms underlying anticancer effects of arctigenin and sesamin. Our review comprehensively describes the effects of arctigenin and sesamin on the signaling pathways and related molecules involved in cancer cell proliferation and invasion. The findings of present review show that the dietary lignans arctigenin and sesamin seem to be promising carcinopreventive and anticancer agents. These natural lignans can be used as dietary supplements and pharmaceuticals for prevention and treatment of cancer.

The signaling pathways and targets of traditional Chinese medicine and natural medicine in triple-negative breast cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Triple-negative breast cancer (TNBC) has a poorer prognosis than other subtypes due to its strong invasion and higher risk of distant metastasis. Traditional Chinese medicine (TCM) and natural medicine have the unique advantages of multitargets and small side-effects and may be used as long-term complementary and alternative therapies.

AIM OF THE REVIEW

The present article summarizes the classical signaling pathways and potential targets by the action of TCM and natural medicine (including extracts, active constituents and formulas) on TNBC and provides evidence for its clinical efficacy.

METHODS

The literature information was acquired from the scientific databases PubMed, Web of Science and CNKI from January 2010 to June 2020, and it was designed to elucidate the internal mechanism and role of TCM and natural medicine in the treatment of TNBC. The search key words included "Triple negative breast cancer" or "triple negative breast carcinoma", "TNBC" and "traditional Chinese medicine" or "Chinese herbal medicine", "medicinal plant", "natural plant", and "herb".

RESULTS

We described the antitumor activity of TCM and natural medicine in TNBC based on different signaling pathways. Plant medicine and herbal formulas regulated the related gene and protein expression via pathways such as PI3K/AKT/mTOR, MAPK and Wnt/β-catenin, which inhibit the growth, proliferation, migration, invasion and metastasis of TNBC cells.

CONCLUSION

The inhibitory effect of TCM and natural medicine on tumors was reflected in multiple levels and multiple pathways, providing reasonable evidence for new drug development. To make TCM and natural medicine widely and flexibly used in clinical practice, the efficacy, safety and mechanism of action need more in-depth experimental research.

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

miR-518a-3p Suppresses Triple-Negative Breast Cancer Invasion and Migration Through Regulation of TMEM2

MicroRNAs (miRNAs) are emerging as critical mediators in tumors, including triple-negative breast cancer (TNBC). The role of miR-518a-3p in TNBC was investigated to identify potential therapeutic target. Data from KM Plotter database (www.kmplot.com) showed that high miR-518a-3p expression was significantly associated with overall survival of patients with TNBC (p = 0.04). The expression of miR-518a-3p was dysregulated in TNBC cells. Functional assays revealed that over-expression of miR-518a-3p inhibited cell invasion and migration of TNBC. Additionally, miR-518a-3p could target TMEM2 (transmembrane protein 2), and decreased protein and mRNA expression of TMEM2 in TNBC cells. Knockdown of TMEM2 suppressed cell invasion and migration through inhibiting phospho (p)-JAK1 (Janus kinase 1) and p-STAT (signal transducer and activator of transcription protein) 1/2. Moreover, over-expression of TMEM2 counteracted the suppressive effect of miR-518a-3p on TNBC invasion and migration through promoting the levels of p-JAK1 and p-STAT1/2. In conclusion, miR-518a-3p negatively regulates the JAK/STAT pathway via targeting TMEM2 and suppresses invasion and migration in TNBC, suggesting that miR-518a-3p may be a potential therapeutic target in TNBC.

A Review of Natural Therapies Potentially Relevant in Triple Negative Breast Cancer Aimed at Targeting Cancer Cell Vulnerabilities

We reviewed the research into the mechanisms of growth of triple negative breast cancer (TNBC) based on laboratory pre-clinical studies that have shaped understanding of the disease over the past decade. In response to these findings, we propose an approach to potentially prevent cancer metabolic adaptation and recurrence. This paper collates pre-clinical results, first to determine the tumor’s mechanisms of growth and then to source natural substances that could potentially suppress those mechanisms. The results from in vivo and in vitro studies of TNBC were combined first to select 10 primary mechanisms (Hypoxia-inducible factor 1α, Hedgehog, MAPK, MTAP, NF-κ B, Notch, P13K, STAT3, and Wnt signaling pathways plus p53 and POL2A gene expression) that promote TNBC growth, and second to propose a treatment array of 21 natural compounds that suppress laboratory models of TNBC via these mechanisms. We included BRCA mutations in the review process, but only pathways with the most preclinical studies utilizing natural products were included. Then we outlined potential biomarkers to assess the changes in the micro-environment and monitor biochemical pathway suppression. This suppression-centric aim targets these mechanisms of growth with the goal of potentially halting tumor growth and preventing cancer cell metabolic adaptation. We chose TNBC to demonstrate this 5-step strategy of supplementary therapy, which may be replicated for other tumor types.

Medicinal Herbs Used in Traditional Management of Breast Cancer: Mechanisms of Action

Background: Breast cancer is one of the principal causes of death among women and there is a pressing need to develop novel and effective anti-cancer agents. Natural plant products have shown promising results as anti-cancer agents. Their effectiveness is reported as decreased toxicity in usage, along with safety and less recurrent resistances compared with hormonal targeting anti-cancer agents. Methods: A literature search was conducted for all English-language literature published prior to June 2020. The search was conducted using electronic databases, including PubMed, Embase, Web of Science, and Cochrane Library. The search strategy included keywords such as breast cancer, herbs, anti-cancer biologically active components, clinical research, chemotherapy drugs amongst others. Results: The literature provides documented evidence of the chemo-preventative and chemotherapeutic properties of Ginseng, garlic (Allium sativum), Black cohosh (Actaea racemose), Tumeric (Curcuma longa), Camellia sinenis (green tea), Echinacea, Arctium (burdock), Flaxseed (Linum usitatissimum) and Black Cumin (Nigella sativa). Conclusions: The nine herbs displayed anti-cancer properties and their outcomes and mechanisms of action include inhibition of cell proliferation, angiogenesis and apoptosis as well as modulation of key intracellular pathways. However, more clinical trials and cohort human studies should be conducted to provide key evidence of their medical benefits.

Targeting β-Catenin Signaling by Natural Products for Cancer Prevention and Therapy

The mutations and deregulation of Wnt signaling pathway occur commonly in human cancer and cause the aberrant activation of β-catenin and β-catenin-dependent transcription, thus contributing to cancer development and progression. Therefore, β-catenin has been demonstrated as a promising target for cancer prevention and therapy. Many natural products have been characterized as inhibitors of the β-catenin signaling through down-regulating β-catenin expression, modulating its phosphorylation, promoting its ubiquitination and proteasomal degradation, inhibiting its nuclear translocation, or other molecular mechanisms. These natural product inhibitors have shown preventive and therapeutic efficacy in various cancer models in vitro and in vivo. In the present review, we comprehensively discuss the natural product β-catenin inhibitors, their in vitro and in vivo anticancer activities, and underlying molecular mechanisms. We also discuss the current β-catenin-targeting strategies and other potential strategies that may be examined for identifying new β-catenin inhibitors as cancer preventive and therapeutic drugs.

Arctigenin inhibits proliferation of ER-positive breast cancer cells through cell cycle arrest mediated by GSK3-dependent cyclin D1 degradation

Estrogen receptor (ER) positive accounts for a large proportion of breast cancer. Although there are many targeted therapeutic drugs, the emergence of drug resistance urgently requires the development of new drugs. Arctigenin (Arc), a lignan found in certain plants of the Asteraceae, has the effect on inhibiting breast cancer, but its molecular mechanism has not been clear.

AIMS

To this end, the current study focuses on understanding the mechanism of Arc on ER-positive breast cancer cells.

MAIN METHODS

Colony formation experiments and sulforhodamine B methods were used to determine the growth-inhibitory effect of Arc. The cell cycle and apoptosis were analyzed by flow cytometry. Alterations of signaling proteins were measured by Western blotting. Protein degradation was determined by comparing protein half-lives and inhibiting proteasome.

KEY FINDINGS

The experimental results show that Arc did not induce apoptosis in ER-positive breast cancer cell, rather caused G1 cycle arrest by decreasing cyclin D1 levels without effect on altering CDK4/6 levels. Moreover, we have demonstrated that Arc decreases cyclin D1 levels through prompting Akt/GSK3β-mediated degradation.

SIGNIFICANCE

These findings warrant the potential of Arc as a candidate treatment for ER-positive breast cancer.

Arnicolide D Inhibits Triple Negative Breast Cancer Cell Proliferation by Suppression of Akt/mTOR and STAT3 Signaling Pathways

Triple-Negative Breast Cancer (TNBC) is a most dangerous breast cancer subtype. The naturally occurring sesquiterpene lactone, arnicolide D (AD), has proven effective against a variety of tumors, however, the inhibitory effects of AD against TNBC and the underlying mechanisms remain unclear. In the present study, two TNBC cell lines (MDA-MB-231 and MDA-MB-468) and an MDA-MB-231 xenograft mouse model were employed to investigate the anti-TNBC effects of AD in vitro and in vivo. Cell viability was assessed by MTT assay. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Protein levels were determined by immunoblotting. In vitro studies demonstrated that AD significantly decreased cell viability, and induced G2/M cell cycle arrest and apoptosis. In vivo assays showed that oral administration of 25 or 50 mg/kg AD for 22 days led to a reduction of tumor weights by 24.7% or 41.0%, without appreciable side effects. Mechanistically, AD inhibited the activation of Akt/mTOR and STAT3 signaling pathways. Based on our findings, AD is a promising candidate for development as an adjunctive therapeutic drug for TNBC.

Cucurbitacin B inhibits gastric cancer progression by suppressing STAT3 activity

Signal transducer and activator of transcription 3 (STAT3) is expressed aberrantly in multiple tumors, including gastric cancer (GC). STAT3 overexpression and excessive activation have been confirmed to play vital roles in tumorigenesis. Cucurbitacin B (CuB) is a natural product with potent anti-cancer activities in solid tumors. Here, we systematically studied the underlying molecular mechanisms of CuB inhibition of GC both in vitro and in vivo. In GC cell lines, nanomolar concentrations of CuB decreased the phosphorylation of TYR-705 in STAT3 and suppressed STAT3 target gene expression, including c-Myc and Bcl-xL. Computational docking analysis showed that CuB interacts with the DNA-binding domain of STAT3 at several hydrophobic residues. In addition, pull-down experiments showed that CuB is a direct inhibitor of STAT3. CuB in combination with the conventional chemotherapy drug cisplatin exerted enhanced cytotoxicity in GC cells, possibly due to the potentiated inhibition of STAT3 activation. Moreover, a xenograft mouse model confirmed the therapeutic effect of CuB in vivo. These characteristics render CuB a promising candidate drug for further development in the design of new effective STAT3 inhibitors for treating GC.

Anti‑metastatic effects of arctigenin are regulated by MAPK/AP‑1 signaling in 4T‑1 mouse breast cancer cells

Arctigenin is a natural lignan that is found in burdock with anti‑viral, ‑oxidative, ‑inflammatory and anti‑tumor activities. In the current study, the effect of arctigenin on metastatic potential was examined in 4T‑1 mouse triple‑negative breast cancer cells. The results indicated that arctigenin inhibited cell motility and invasiveness, which was determined using wound healing and transwell invasion assays. Arctigenin suppressed matrix metalloprotease‑9 (MMP‑9) activity via gelatin zymography, and protein expression of cyclooxygenase‑2 (COX‑2) and MMP‑3. Furthermore, arctigenin attenuated the mRNA expression of metastatic factors, including MMP‑9, MMP‑3 and COX‑2. Based on these results, the effect of arctigenin on the mitogen‑activated protein kinase (MAPK)/activating protein‑1 (AP‑1) signaling pathway was assessed in an attempt to identify the regulatory mechanism responsible for its anti‑metastatic effects. Arctigenin was demonstrated to inhibit the phosphorylation of extracellular signal‑regulated protein kinase (ERK) and c‑Jun N‑terminal kinase (JNK), and the nuclear translocations of the AP‑1 subunits, c‑Jun and c‑Fos. In summary, the present study demonstrated that in 4T‑1 mouse triple‑negative breast cancer cells the anti‑metastatic effect of arctigenin is mediated by the inhibition of MMP‑9 activity and by the inhibition of the metastasis‑enhancing factors MMP‑9, MMP‑3 and COX‑2, due to the suppression of the MAPK/AP‑1 signaling pathway. The results of the current study demonstrated that arctigenin exhibits a potential for preventing cell migration and invasion in triple negative breast cancer.

Toxicity Study of 28-Day Subcutaneous Injection of Arctigenin in Beagle Dogs

Our previous studies have investigated the systematic pharmacokinetic characteristics, biological activities, and toxicity of arctigenin. In this research, the potential toxicities of arctigenin in beagle dogs were investigated via repeated 28-day subcutaneous injections. Beagle dogs were randomly divided into control, vehicle [polyethylene glycol (PEG)], and arctigenin 6, 20, 60 mg/kg treated groups. The whole experimental period lasted 77 days, including adaptive period (35 days), drug exposure period (animals were treated with saline, PEG, or arctigenin for 28 consecutive days), and recovery period (14 days). Arctigenin injection (60 mg/kg) affected the lymphatic hematopoietic, digestive, urinary, and cardiovascular systems, and all the impact on these tissues resulted in death in five dogs (three female and two male dogs); 20 mg/kg arctigenin injection resulted in toxic reactions of the lymphatic hematopoietic and digestive systems; and 6 mg/kg arctigenin and PEG injection did not lead to significant toxic reactions. Meanwhile, there were no sexual differences of drug exposure and accumulation when dogs underwent different dosages. As stated previously, the toxic target organs of arctigenin administration include lymphatic hematopoietic, digestive (liver and gallbladder), urinary (kidney), and cardiovascular (heart) systems, and the no observed adverse effect level (NOAEL) of arctigenin is less than 6 mg/kg.

3'-Desmethylarctigenin induces G2/M cell cycle arrest and apoptosis through reactive oxygen species generation in hepatocarcinoma cells

Previous studies have shown that arctigenin is a promising chemopreventive or therapeutic agent against various cancers. However, less is known about anticancer activity of 3'-desmethylarctigenin (3'-DMAG), which is a biotransformed product from arctigenin or arctin. In this study, we compared the anticancer activity of 3'-DMAG with its parent compound arctigenin and demonstrated that 3'-DMAG exerted a more potent inhibitory effect on HepG2 cells than arctigenin. Mechanistically, reactive oxygen species generation played an apical role in 3'-DMAG-induced G2/M cell cycle arrest and apoptosis in HepG2 cells. Furthermore, the Chk2-Cdc25c-Cdc2-cyclin B1 cascade was found to contribute to the cell cycle arrest, whereas the activation of mitochondrial pathway was involved in the cell apoptosis by 3'-DMAG. Additionally, a mouse xenograft hepatocellular carcinoma model was used to evaluate the antitumor effect of 3'-DMAG in vivo, and the results indicated that 3'-DMAG treatment significantly inhibited tumor growth without apparent toxicity. Taken together, 3'-DMAG is highly effective against liver cancer both in vitro and in vivo. The findings of the present study suggest that this compound deserves to be further investigated for its potential anticancer activity.

Protopanaxadiol inhibits epithelial-mesenchymal transition of hepatocellular carcinoma by targeting STAT3 pathway

Diol-type ginsenosides, such as protopanaxadiol (PPD), exhibit antioxidation, anti-inflammation, and antitumor effects. However, the antitumor effect of these ginsenosides and the mechanism of PPD remain unclear. In this work, the antitumor effects of several derivatives, including PPD, Rg5, Rg3, Rh2, and Rh3, were evaluated in five different cancer cell lines. PPD demonstrated the best inhibitory effects on the proliferation and migration of the five cancer cell lines, especially the hepatocellular carcinoma (HCC) cell lines. Therefore, the mechanism of action of PPD in HCC cells was elucidated. PPD inhibited the proliferation, migration, and invasion ability of HepG2 and PLC/PRF/5 cells in a dose-dependent manner. Western blot and immunofluorescence assay showed that PPD can alter the expression of epithelial–mesenchymal transition markers, increase E-cadherin expression, and decrease vimentin expression. Docking and biacore experiments revealed that STAT3 is the target protein of PPD, which formed hydrogen bonds with Gly583/Leu608/Tyr674 at the SH2 domain of STAT3. PPD inhibited the phosphorylation of STAT3 and its translocation from the cytosol to the nucleus, thereby inhibiting the expression of Twist1. PPD also inhibited tumor volume and tumor lung metastasis in PLC/PRF/5 xenograft model. In conclusion, PPD can inhibit the proliferation and metastasis of HCC cells through the STAT3/Twist1 pathway.

Methanol Extract of Aerial Parts of Pavetta indica L. Enhances the Cytotoxic Effect of Doxorubicin and Induces Radiation Sensitization in MDA-MB-231 Triple-Negative Breast Cancer Cells

Pavetta indica L. is used in traditional medicine for the treatment of various diseases including hemorrhoids, headache, urinary conditions, ulcerated nose, and dropsy. However, no study has evaluated the anticancer effect of P. indica L. In this study, we found that a methanol extract of the leaves and branches of P. indica L. (MEPI) caused cellcycle arrest at the sub-G1 phase and induced apoptosis, as indicated by the activation of caspase-8, -3, -7, and c-PARP. Western blotting revealed that MEPI significantly reduced the levels of markers of the epithelial-mesenchymal transition, such as Vimentin, Snail, Slug, and matrix metallopeptidase 9. Notably, the expression of multidrug resistance-associated protein 1 in triple negative breast cancer (TNBC) was significantly decreased by MEPI. Moreover, the co-treatment with MEPI and doxorubicin resulted in a synergistic reduction in cell viability. MEPI also induced radiation sensitization of TNBC cells. Gas chromatography-mass spectrometry analysis revealed that 5,6-dehydrokawain (DK) is the major constituent of MEPI. Interestingly, DK exerted significant anti-invasive and anti-metastatic effects. Our results provide a strong rationale for investigating the molecular mechanisms of action of MEPI in TNBC.

Ilamycin C induces apoptosis and inhibits migration and invasion in triple-negative breast cancer by suppressing IL-6/STAT3 pathway

BACKGROUND

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor prognosis, and its treatment remains a challenge due to few targeted medicines and high risk of relapse, metastasis, and drug resistance. Thus, more effective drugs and new regimens for the therapy of TNBC are urgently needed. Ilamycins are a kind of cyclic peptides and produced by Streptomyces atratus and Streptomyces islandicus with effective anti-tuberculosis activity. Ilamycin C is a novel compound isolated from the deep South China Sea-derived Streptomyces atratus SCSIO ZH16 and exhibited a strong cytotoxic activity against several cancers including breast cancer cell line MCF7. However, the cytotoxic activity of Ilamycin C to TNBC cells and a detailed antitumor mechanism have not been reported.

METHODS

CCK-8 assays were used to examine cell viability and cytotoxic activity of Ilamycin C to TNBC, non-TNBC MCF7, and nonmalignant MCF10A cells. EdU assays and flow cytometry were performed to assess cell proliferation and cell apoptosis. Transwell migration and Matrigel invasion assays were utilized to assess the migratory and invading capacity of TNBC cells following the treatment of Ilamycin C. The expressions of proteins were detected by western blot.

RESULTS

In this study, we found that Ilamycin C has more preferential cytotoxicity in TNBC cells than non-TNBC MCF7 and nonmalignant MCF10A cells. Notably, our studies revealed the mechanism that Ilamycin C can induce Bax/Bcl-2-related caspase-dependent apoptosis and inhibit migration and invasion through MMP2/MMP9/vimentin/fascin in TNBC by suppressing IL-6-induced STAT3 phosphorylation.

CONCLUSIONS

This study provides the first evidence that Ilamycin C has significant implications for the potential as a novel IL-6/STAT3 inhibitor for TNBC treatment in the future.

Chemoresistance in the Human Triple-Negative Breast Cancer Cell Line MDA-MB-231 Induced by Doxorubicin Gradient Is Associated with Epigenetic Alterations in Histone Deacetylase

Chemoresistance is one of the major causes of therapeutic failure in breast cancer patients. In this study, the mechanism of chemoresistance in human triple-negative breast cancer (TNBC) cells (MDA-MB-231) induced by doxorubicin (DOX) gradient was investigated. These DOX-resistant cells showed higher drug efflux rate, increased anchorage-independent growth when cultured in suspension, and increased tumor-forming ability in nude mice, compared to the wild-type MDA-MB-231 cells. RNA sequencing analysis showed an increase in the expression of genes involved in membrane transport, antiapoptosis, and histone regulation. Kaplan-Meier plot analysis of TNBC patients who underwent preoperative chemotherapy showed that the relapse free survival (RFS) of patients with high HIST1H2BK (histone cluster 1 H2B family member k) expression was significantly lower than that of patients with low HIST1H2BK expression. Quantitative real-time PCR confirmed that the level of HIST1H2BK expression was increased in resistant cells. The cytotoxicity analysis showed that the DOX resistance of resistant cells was reduced by treatment with a histone deacetylase (HDAC) inhibitor. Our results suggest that, in DOX-resistant cells, HIST1H2BK expression can be rapidly induced by the high expression of genes involved in membrane transport, antiapoptosis, and histone regulation. In conclusion, chemoresistance in MDA-MB-231 cells can occur in a relatively short period by DOX gradient via this previously known mechanism of resistance, and DOX resistance is dependent on the specificity of resistant cells to HDAC.

Arctigenin induces apoptosis in human hepatoblastoma cells

PURPOSE

Arctigenin has been shown to have anti-tumor effects in various types of cancers. This study was conducted to verify these effects in the human-derived hepatoblastoma cell line, HUH-6 clone 5 (hereinafter, HUH-6).

METHODS

Arctigenin was added to cultured HUH-6 cells, and cellular activity was evaluated by MTS assay. To determine the relationship between reduced cellular activity and apoptosis, we measured the activities of caspase 3/7, 8, and 9 and conducted flow cytometry with Annexin V/PI staining.

RESULTS

The MTS assay revealed that cellular activity decreased after arctigenin treatment in a concentration-dependent manner (IC₅₀ = 4 µM). To investigate apoptosis induction, activity assays of caspase 3/7, 8, and 9 were performed. While caspase 3/7 and 8 exhibited high activity, caspase 9 showed no activity. Thus, apoptosis induction may have involved the action of tumor necrosis factor receptor 1 (TNFR1). Flow cytometry conducted with Annexin V/PI staining revealed the occurrence of early apoptosis.

CONCLUSION

We found that arctigenin has anti-tumor effects in HUH-6 cells in a concentration-dependent manner. Arctigenin may have exerted its anti-tumor effect by inducing apoptosis via TNFR1, which recruits Complex IIa to activate caspase 8 and 3/7. These results may be useful for developing therapeutic agents for hepatoblastoma.

Lignans and Neolignans: Plant secondary metabolites as a reservoir of biologically active substances

Lignans and neolignans are plant secondary metabolites derived from the oxidative coupling of phenylpropanoids. Biological activity of these phenolic compounds ranges from antioxidant, antitumor (terminaloside P, IC₅₀ = 10 nM), anti-inflammatory, anti-neurodegenerative (schibitubin B, IC₅₀ = 3.2 nM) and antiviral (patentiflorin A, IC₅₀ = 14-23 nM) to antimicrobial. In addition, it was observed that several members of this group, namely enterolactone and its biochemical precursors also known as phytoestrogens, possess important protective properties. Most of these lignans and neolignans are presented in reasonable amounts in one's diet and thus the protection they provide against the colon and breast cancer, to name a few, is even more important to note. Similarly, neuroprotective properties were observed (schisanwilsonin G, IC₅₀ = 3.2 nM) These structural motives also serve as an important starting point in the development of anticancer drugs. Presumably the most famous members of this family, etoposide and teniposide, synthetic derivatives of podophyllotoxin, are used in the clinical treatment of lymphocytic leukemia, certain brain tumors, and lung tumors already for nearly 20 years. This review describes 413 lignans and neolignans which have been isolated between 2016 and mid-2018 being reported in more than 300 peer-reviewed articles. It covers their source, structure elucidation, and bioactivity. Within the review, the structure-based overview of compounds as well as the bioactivity-based overview of compounds are described.

STAT3 as a potential therapeutic target in triple negative breast cancer: a systematic review

Triple negative breast cancer (TNBC), which is typically lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), represents the most aggressive and mortal subtype of breast cancer. Currently, only a few treatment options are available for TNBC due to the absence of molecular targets, which underscores the need for developing novel therapeutic and preventive approaches for this disease. Recent evidence from clinical trials and preclinical studies has demonstrated a pivotal role of signal transducer and activator of transcription 3 (STAT3) in the initiation, progression, metastasis, and immune evasion of TNBC. STAT3 is overexpressed and constitutively activated in TNBC cells and contributes to cell survival, proliferation, cell cycle progression, anti-apoptosis, migration, invasion, angiogenesis, chemoresistance, immunosuppression, and stem cells self-renewal and differentiation by regulating the expression of its downstream target genes. STAT3 small molecule inhibitors have been developed and shown excellent anticancer activities in in vitro and in vivo models of TNBC. This review discusses the recent advances in the understanding of STAT3, with a focus on STAT3’s oncogenic role in TNBC. The current targeting strategies and representative small molecule inhibitors of STAT3 are highlighted. We also propose potential strategies that can be further examined for developing more specific and effective inhibitors for TNBC prevention and therapy.

Involvement of Stat3 phosphorylation in mild heat shock-induced thermotolerance

Thermotolerance is a phenomenon in which cells become resistant to stress by prior exposure to heat shock, and its development is associated with the induction of heat shock proteins (Hsps), including Hsp70. We previously showed that the expression of Hsp70 is regulated by the cytokine signaling transcription factor Stat3, but the role of Stat3 in thermotolerance is not known. In this study, we examined the possible involvement of Stat3 in the acquisition of thermotolerance. We found that severe heat shock-induced morphological changes and decreases in cell viability, which were suppressed by exposure to non-lethal mild heat shock prior to severe heat shock. This thermotolerance development was accompanied by Stat3 phosphorylation and the induction of Hsps such as Hsp105, Hsp70, and Hsp27. Stat3 phosphorylation and Hsp induction were inhibited by AG490, an inhibitor of JAK tyrosine kinase. Consistent with this, we found that mild heat shock-induced thermotolerance was partially suppressed by AG490 or knockdown of Hsp105. We also found that the Stat3 inhibitor Stattic suppresses the acquisition of thermotolerance by inhibiting the mild heat shock-induced Stat3 phosphorylation and Hsp105 expression. These results suggest that the mild heat shock-dependent stimulation of the JAK-Stat signaling pathway contributes to the development of thermotolerance via the induction of Hsps including Hsp105. This signaling pathway may be a useful target for hyperthermia cancer therapy.

Cucurbitacin B Induces the Lysosomal Degradation of EGFR and Suppresses the CIP2A/PP2A/Akt Signaling Axis in Gefitinib-Resistant Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) patients carrying an epidermal growth factor receptor (EGFR) mutation are initially sensitive to EGFR-tyrosine kinase inhibitors (TKIs) treatment, but soon develop an acquired resistance. The treatment effect of EGFR-TKIs-resistant NSCLC patients still faces challenges. Cucurbitacin B (CuB), a triterpene hydrocarbon compound isolated from plants of various families and genera, elicits anticancer effects in a variety of cancer types. However, whether CuB is a viable treatment option for gefitinib-resistant (GR) NSCLC remains unclear. Here, we investigated the anticancer effects and underlying mechanisms of CuB. We report that CuB inhibited the growth and invasion of GR NSCLC cells and induced apoptosis. The inhibitory effect of CuB occurred through its promotion of the lysosomal degradation of EGFR and the downregulation of the cancerous inhibitor of protein phosphatase 2A/protein phosphatase 2A/Akt (CIP2A/PP2A/Akt) signaling axis. CuB and cisplatin synergistically inhibited tumor growth. A xenograft tumor model indicated that CuB inhibited tumor growth in vivo. Immunohistochemistry results further demonstrated that CuB decreased EGFR and CIP2A levels in vivo. These findings suggested that CuB could suppress the growth and invasion of GR NSCLC cells by inducing the lysosomal degradation of EGFR and by downregulating the CIP2A/PP2A/Akt signaling axis. Thus, CuB may be a new drug candidate for the treatment of GR NSCLC.

Cryptotanshinone inhibits esophageal squamous-cell carcinoma in vitro and in vivo through the suppression of STAT3 activation

Purpose

Esophageal squamous-cell carcinoma (ESCC) is the most common subtype of esophageal cancer, with a poor clinical outcome. Cryptotanshinone (CTS) is the main bioactive compound from the root of Salvia miltiorrhiza Bunge. Our study aimed to investigate the anti-cancer effects and molecular mechanisms of CTS on ESCC.

Materials and methods

We investigated the anti-tumor activity of CTS on ESCC in vitro and in vivo. Activation of the STAT3 signaling pathway was evaluated in ESCC and HEK-Blue™ IL-6 cells. Cell viability was assessed by the MTT assay. Apoptosis and cell cycle arrest were assessed using flow cytometry. Cell migration was detected by a scratch wound assay.

Results

CTS inhibited STAT3 expression and IL-6-mediated STAT3 activation in esophageal cancer cells. Subsequently, CTS dose-dependently inhibited the proliferation of esophageal cancer cells via induction of cell apoptosis. Furthermore, CTS suppressed the migration of esophageal cancer cells. In vivo, CTS inhibited tumor growth of EC109 cell in xenograft mice without any obvious effect on body weight.

Conclusion

Our results indicated that STAT3 inhibition may be a therapeutic target for esophageal cancer. CTS could provide a potential approach for esophageal cancer therapy by influencing the janus kinase-2/STAT3 signaling pathway.

Cucurbitacin B Inhibits the Hippo-YAP Signaling Pathway and Exerts Anticancer Activity in Colorectal Cancer Cells

BACKGROUND Colorectal carcinoma (CRC) is one of the most frequently diagnosed malignancies. Cucurbitacin B (CuB) is a natural compound isolated from herbs and shows anticancer activity in several cancers. MATERIAL AND METHODS Here, we analyzed the effects of different CuB concentrations on the proliferative and invasive behaviors of CRC cells using MTT, clonogenic assay, Transwell invasion, and wound healing assays. Flow cytometry was performed to measure the apoptotic effects of CuB on CRC cells. Western blot and real-time PCR were used to investigate the expression of apoptosis and Hippo-YAP signaling pathway proteins. RESULTS CuB inhibited the proliferation and invasion of CRC cells while promoting apoptosis. In addition, the Western blot and real-time PCR results indicated that CuB suppressed YAP expression and its downstream target genes Cyr 61 and c-Myc in CRC cells. To assess the underlying mechanism, we investigated the upstream regulating factor LATS1, and the results revealed that CuB upregulated LATS1 expression in CRC cells. CONCLUSIONS In conclusion, our findings uncovered a novel therapeutic mechanism of CuB and suggest that there is therapeutic potential and feasibility in developing novel YAP inhibitors for cancer treatment.

Casticin inhibits growth and enhances ionizing radiation-induced apoptosis through the suppression of STAT3 signaling cascade

Casticin (CTC), one of the major components of Vitex rotundifolia L., has been reported to exert significant beneficial pharmacological activities and can function as an antiprolactin, anticancer, anti-inflammatory, neuroprotective, analgesic, and immunomodulatory agent. This study aimed at investigating whether the proapoptotic effects of CTC may be mediated through the abrogation of signal transducers and activators of transcription-3 (STAT3) signaling pathway in a variety of human tumor cells. We found that CTC significantly decreased cell viability in a concentration-dependent manner and suppressed cell proliferation in 786-O, YD-8, and HN-9 cells. CTC also induced programmed cell death that was found to be mediated via caspase-3 activation and induction of poly(ADP-ribose) polymerase cleavage. Interestingly, CTC repressed both constitutive and interleukin-6-induced STAT3 activation in 786-O and YD-8 cells but only affected constitutive STAT3 phosphorylation in HN-9 cells. Moreover, CTC could potentiate ionizing radiation-induced apoptotic effects leading to the downregulation of STAT3 activation and thus may be used in combination with radiation against diverse malignancies.

Arctigenin shows preferential cytotoxicity to acidity-tolerant prostate carcinoma PC-3 cells through ROS-mediated mitochondrial damage and the inhibition of PI3K/Akt/mTOR pathway

Extracellular acidity in the tumor microenvironment contributes to chemoresistance of malignant tumors. The objective of this study was to determine anticancer effects of arctigenin, a novel anti-inflammatory lignan extracted from seeds of Arctium lappa, on acidity-tolerant prostate cancer PC-3AcT cells. The PC-3AcT cells manifested increased tolerance to low-pH media with enhanced percent cell viability and increased resistance to docetaxel compared to their parental PC-3 cells. Arctigenin alone or in combination with docetaxel induced potent cytotoxicity. Preferential sensitization of PC-3AcT cells to arctigenin was accompanied by increased cell fractions with sub-G₀/G₁ peak and annexin V-PE(+), increased ROS levels, decreased mitochondrial membrane potential and cellular ATP content, and inhibition of PI3K/Akt/mTOR pathway. A series of changes caused by arctigenin were efficiently reversed through reducing ROS levels by radical scavenger N-acetylcysteine, thus placing ROS upstream of arctigenin-driven cytotoxicity. Collectively, these results demonstrate that arctigenin can increase oxidative stress-mediated mitochondrial damage of acidity-tolerant PC-3AcT cells, suggesting that arctigenin might be a potential therapeutic candidate to overcome acidic-microenvironment-associated chemotherapeutic resistance in prostate cancer.

Molecular mechanisms of the action of Arctigenin in cancer

Since antediluvian times, the scientific community has realized that natural compounds exhibit enormous potential for the treatment of terrible diseases, such as cancer. Despite a variety of effective bioactive molecules, effective therapies still need to be developed to treat cancer. Hence, it is necessary to study the interactions of natural molecules with their cellular targets. Arctigenin (ATG), a natural lignan compound extracted from Arctium lappa, inhibits the growth of various cancer cells, such as those of the stomach, lungs, liver, and colon, as well as leukocytes, and regulates numerous intracellular activities, such as antioxidative, anti-inflammatory, and anticancer activities. The intention of this paper is to summarize and generally analyse the molecular pathways that are involved in the anticancer effects of ATG. In addition, the interactions of ATG with other drugs are also highlighted in this paper.

Polyphyllin I inhibits invasion and epithelial-mesenchymal transition via CIP2A/PP2A/ERK signaling in prostate cancer

Polyphyllin I (PPI) is a natural compound extracted from the rhizomes of Paris polyphylla and has been used to treat fevers and headaches in China. In the present study, the antitumor activity of PPI in prostate cancer (PC) cells was evaluated. At low doses, PPI decreased proliferation, invasion and epithelial-mesenchymal transition (EMT) in PC cells. PPI decreased the expression of matrix metalloproteinase 7 (MMP7), an enzyme that is critical for tumor metastasis. PPI also decreased the expression of Snail and vimentin, which are EMT-associated factors. Additionally, PPI suppressed AP-1 transcriptional activity and AP-1 binding to the MMP7 and vimentin promoters. The results demonstrated that PPI downregulated the phosphorylation of extracellular signaling‑related kinase (ERK), which is upstream modulator of AP-1. The results of the present study demonstrated that PPI may inhibit the cancerous inhibitor of protein phosphatase 2A (CIP2A)/protein phosphatase 2A (PP2A)/ERK axis, downregulate the expression of MMP7, vimentin, and Snail, and suppress tumor invasion and EMT. A PC xenograft mouse model was employed and the results revealed that PPI may decrease tumor growth and weight. Additionally, PPI may inhibit proliferating cell nuclear antigen expression and CIP2A/PP2A/ERK signaling pathway in PPI-treated tumors. Therefore, the results of the present study suggest that PPI may suppress the growth, invasion and EMT of PC cells via inhibition of CIP2A/PP2A/ERK signaling axis. As a result, PPI may be a novel target for the treatment of PC.

Structural Biology of STAT3 and Its Implications for Anticancer Therapies Development

Transcription factors are proteins able to bind DNA and induce the transcription of specific genes. Consequently, they play a pivotal role in multiple cellular pathways and are frequently over-expressed or dysregulated in cancer. Here, we will focus on a specific “signal transducer and activator of transcription” (STAT3) factor that is involved in several pathologies, including cancer. For long time, the mechanism by which STAT3 exerts its cellular functions has been summarized by a three steps process: (1) Protein phosphorylation by specific kinases, (2) dimerization promoted by phosphorylation, (3) activation of gene expression by the phosphorylated dimer. Consequently, most of the inhibitors reported in literature aimed at blocking phosphorylation and dimerization. However, recent observations reopened the debate and the entire functional mechanism has been revisited stimulating the scientific community to pursue new inhibition strategies. In particular, the dimerization of the unphosphorylated species has been experimentally demonstrated and specific roles proposed also for these dimers. Despite difficulties in the expression and purification of the full length STAT3, structural biology investigations allowed the determination of atomistic structures of STAT3 dimers and several protein domains. Starting from this information, computational methods have been used both to improve the understanding of the STAT3 functional mechanism and to design new inhibitors to be used as anticancer drugs. In this review, we will focus on the contribution of structural biology to understand the roles of STAT3, to design new inhibitors and to suggest new strategies of pharmacological intervention.

Ethoxysanguinarine inhibits viability and induces apoptosis of colorectal cancer cells by inhibiting CIP2A

Cancerous inhibitor of protein phosphatase 2A (CIP2A) an endogenous inhibitor of protein phosphatase 2A (PP2A), which can promote proliferation and transformation of several cancer types, has been shown to be a target for tumor therapy. The present study investigated the effects and underlying mechanisms of action of a novel natural compound, ethoxysanguinarine (Eth), on colorectal cancer (CRC) cells. MTT assay and flow cytometric assay found that Eth inhibited the viability and induced the apoptosis of the CRC cells. The inhibition of viability and activation of apoptosis was mediated through the Eth-induced decrease in CIP2A expression. Knockdown of CIP2A by RNA interference sensitized, whereas overexpression of CIP2A antagonized, Eth-induced viability inhibition and apoptosis. Furthermore, western blot analysis suggested that Eth inhibited phosphorylation of CIP2A downstream molecule protein kinase B via the activation of PP2A. CRC xenograft tests also confirmed the antitumor effect of Eth in vivo. These results advance our understanding of Eth-induced viability inhibition and apoptosis, implying the requirement for further investigation of Eth as a CIP2A inhibitor for cancer therapies.