Brusatol, a Nrf2 Inhibitor Targets STAT3 Signaling Cascade in Head and Neck Squamous Cell Carcinoma

Brusatol improves the efficacy of an anti-mouse-PD-1 antibody via inhibiting programmed cell death 1 ligand 1 expression in a murine head and neck squamous cell carcinoma model

OBJECTIVE

Combing PD-1/PD-L1 immune checkpoint inhibitors with natural products has exhibited better efficacy than monotherapy. Hence, the purpose of this research was to examine the anti-cancer effects of brusatol, a natural quassinoid-terpenoid derived from Brucea javanica, when used in conjunction with an anti-mouse-PD-1 antibody in a murine head and neck squamous cell carcinoma (HNSCC) model and elucidate underlying mechanisms.

DESIGN

A murine HNSCC model and an SCC-15 cell xenograft nude mouse model were established to investigate the anti-cancer effects of brusatol and anti-PD-1 antibody. Mechanistic studies were performed using immunohistochemistry. Cell proliferation, migration, colony formation, and invasion were evaluated by MTT, migration, colony formation, and transwell invasion assays. PD-L1 levels in oral squamous cell carcinoma (OSCC) cells were assessed through qRT-PCR, flow cytometry, and western blotting assays. The impact of brusatol on Jurkat T cell function was assessed by an OSCC/Jurkat co-culture assay.

RESULTS

Brusatol improved tumor suppression by anti-PD-1 antibody in HNSCC mouse models. Mechanistic studies revealed brusatol inhibited tumor cell growth and angiogenesis, induced apoptosis, increased T lymphocyte infiltration, and reduced PD-L1 expression in tumors. Furthermore, in vitro assays confirmed brusatol inhibited PD-L1 expression in OSCC cells and suppressed cell migration, colony formation, and invasion. Co-culture assays indicated that brusatol's PD-L1 inhibition enhanced Jurkat T cell-mediated OSCC cell death and reversed the inhibitory effect induced by OSCC cells.

CONCLUSIONS

Brusatol improves anti-PD-1 antibody efficacy by targeting PD-L1, suggesting its potential as an adjuvant in anti-PD-1 immunotherapy.

Ferroptosis: Biology and Role in Gastrointestinal Disease

Ferroptosis is a form of nonapoptotic cell death that involves iron-dependent phospholipid peroxidation induced by accumulation of reactive oxygen species, and results in plasma membrane damage and the release of damage-associated molecular patterns. Ferroptosis has been implicated in aging and immunity, as well as disease states including intestinal and liver conditions and cancer. To date, several ferroptosis-associated genes and pathways have been implicated in liver disease. Although ferroptotic cell death is associated with dysfunction of the intestinal epithelium, the underlying molecular basis is poorly understood. As the mechanisms regulating ferroptosis become further elucidated, there is clear potential to use ferroptosis to achieve therapeutic benefit.

Terpenoid-Mediated Targeting of STAT3 Signaling in Cancer: An Overview of Preclinical Studies

Cancer has become one of the most multifaceted and widespread illnesses affecting human health, causing substantial mortality at an alarming rate. After cardiovascular problems, the condition has a high occurrence rate and ranks second in terms of mortality. The development of new drugs has been facilitated by increased research and a deeper understanding of the mechanisms behind the emergence and advancement of the disease. Numerous preclinical and clinical studies have repeatedly demonstrated the protective effects of natural terpenoids against a range of malignancies. Numerous potential bioactive terpenoids have been investigated in natural sources for their chemopreventive and chemoprotective properties. In practically all body cells, the signaling molecule referred to as signal transducer and activator of transcription 3 (STAT3) is widely expressed. Numerous studies have demonstrated that STAT3 regulates its downstream target genes, including Bcl-2, Bcl-xL, cyclin D1, c-Myc, and survivin, to promote the growth of cells, differentiation, cell cycle progression, angiogenesis, and immune suppression in addition to chemotherapy resistance. Researchers viewed STAT3 as a primary target for cancer therapy because of its crucial involvement in cancer formation. This therapy primarily focuses on directly and indirectly preventing the expression of STAT3 in tumor cells. By explicitly targeting STAT3 in both in vitro and in vivo settings, it has been possible to explain the protective effect of terpenoids against malignant cells. In this study, we provide a complete overview of STAT3 signal transduction processes, the involvement of STAT3 in carcinogenesis, and mechanisms related to STAT3 persistent activation. The article also thoroughly summarizes the inhibition of STAT3 signaling by certain terpenoid phytochemicals, which have demonstrated strong efficacy in several preclinical cancer models.

A review of Brucea javanica: metabolites, pharmacology and clinical application

This review examines advances in the metabolites, pharmacological research, and therapeutic applications of the medicinal fruit of Brucea javanica (L.) Merr. Brucea javanica (BJ) is derived from the fruit of the Brucea javanica (L.) Merr. There are nearly 200 metabolites present in BJ, and due to the diversity of its metabolites, BJ has a wide range of pharmacological effects. The traditional pharmacological effects of BJ include anti-dysentery, anti-malaria, etc. The research investigating the contemporary pharmacological impacts of BJ mainly focuses on its anti-tumor properties. In the article, the strong monomeric metabolites among these pharmacological effects were preliminarily screened. Regarding the pharmacological mechanism of action, current research has initially explored BJ's pharmacological agent and molecular signaling pathways. However, a comprehensive system has yet to be established. BJ preparations have been utilized in clinical settings and have demonstrated effectiveness. Nevertheless, clinical research is primarily limited to observational studies, and there is a need for higher-quality research evidence to support its clinical application. There are still many difficulties and obstacles in studying BJ. However, it is indisputable that BJ is a botanical drugs with significant potential for application, and it is expected to have broader global usage.

Brusatol enhances MEF2A expression to inhibit RCC progression through the Wnt signalling pathway in renal cell carcinoma

Renal cell carcinoma (RCC) is the most aggressive subtype of kidney tumour with a poor prognosis and an increasing incidence rate worldwide. Brusatol, an essential active ingredient derived from Brucea javanica, exhibits potent antitumour properties. Our study aims to explore a novel treatment strategy for RCC patients. We predicted 37 molecular targets of brusatol based on the structure of brusatol, and MEF2A (Myocyte Enhancer Factor 2A) was selected as our object through bioinformatic analyses. We employed various experimental techniques, including RT-PCR, western blot, CCK8, colony formation, immunofluorescence, wound healing, flow cytometry, Transwell assays and xenograft mouse models, to investigate the impact of MEF2A on RCC. MEF2A expression was found to be reduced in patients with RCC, indicating a close correlation with MEF2A deubiquitylation. Additionally, the protective effects of brusatol on MEF2A were observed. The overexpression of MEF2A inhibits RCC cell proliferation, invasion and migration. In xenograft mice, MEF2A overexpression in RCC cells led to reduced tumour size compared to the control group. The underlying mechanism involves the inhibition of RCC cell proliferation, invasion, migration and epithelial-mesenchymal transition (EMT) through the modulation of Wnt/β-catenin signalling. Altogether, we found that MEF2A overexpression inhibits RCC progression by Wnt/β-catenin signalling, providing novel insight into diagnosis, treatment and prognosis for RCC patients.

Genistein: a promising modulator of apoptosis and survival signaling in cancer

Genistein, a commonly occurring isoflavone, has recently gained popularity owing to its ever-expanding spectrum of pharmacological benefits. In addition to health benefits such as improved bone health and reduced postmenopausal complications owing to its phytoestrogen properties, it has been widely evaluated for its anti-cancer potential. Several studies have established the potential for its usage in the management of breast, lung, and prostate cancers, and its usage has significantly evolved from early applications in traditional systems of medicine. This review offers an insight into its current status of usage, the chemistry, and pharmacokinetics of the molecule, an exploration of its apoptotic mechanisms in cancer management, and opportunities for synergism to improve therapeutic outcomes. In addition to this, the authors have presented an overview of recent clinical trials, to offer an understanding of contemporary studies and explore prospects for a greater number of focused trials, moving forward. Advancements in the application of nanotechnology as a strategy to improve safety and efficacy have also been highlighted, with a brief discussion of results from safety and toxicology studies.

Noncoding RNAs as regulators of STAT3 pathway in gastrointestinal cancers: Roles in cancer progression and therapeutic response

Gastrointestinal (GI) tumors (cancers of the esophagus, gastric, liver, pancreas, colon, and rectum) contribute to a large number of deaths worldwide. STAT3 is an oncogenic transcription factor that promotes the transcription of genes associated with proliferation, antiapoptosis, survival, and metastasis. STAT3 is overactivated in many human malignancies including GI tumors which accelerates tumor progression, metastasis, and drug resistance. Research in recent years demonstrated that noncoding RNAs (ncRNAs) play a major role in the regulation of many signaling pathways including the STAT3 pathway. The major types of endogenous ncRNAs that are being extensively studied in oncology are microRNAs, long noncoding RNAs, and circular RNAs. These ncRNAs can either be tumor-promoters or tumor-suppressors and each one of them imparts their activity via different mechanisms. The STAT3 pathway is also tightly modulated by ncRNAs. In this article, we have elaborated on the tumor-promoting role of STAT3 signaling in GI tumors. Subsequently, we have comprehensively discussed the oncogenic as well as tumor suppressor functions and mechanism of action of ncRNAs that are known to modulate STAT3 signaling in GI cancers.

Hypoxia signaling in hepatocellular carcinoma: Challenges and therapeutic opportunities

Hepatocellular carcinoma (HCC) is one of the most common cancers with a relatively high cancer-related mortality. The uncontrolled proliferation of HCC consumes a significant amount of oxygen, causing the development of a hypoxic tumor microenvironment (TME). Hypoxia-inducible factors (HIFs), crucial regulators in the TME, activate several cancer hallmarks leading to the hepatocarcinogenesis of HCC and resistance to current therapeutics. As such, HIFs and their signaling pathways have been explored as potential therapeutic targets for the future management of HCC. This review discusses the current understanding of the structure and function of HIFs and their complex relationship with the various cancer hallmarks. To address tumor hypoxia, this review provides an insight into the various potential novel therapeutic agents for managing HCC, such as hypoxia-activated prodrugs, HIF inhibitors, nanomaterials, antisense oligonucleotides, and natural compounds, that target HIFs/hypoxic signaling pathways in HCC. Because of HCC's relatively high incidence and mortality rates in the past decades, greater efforts should be put in place to explore novel therapeutic approaches to improve the outcome for HCC patients.

Identification of the Brucea javanica Constituent Brusatol as a EGFR-Tyrosine Kinase Inhibitor in a Cell-Free Assay

Inhibitors of the tyrosine kinase (TK) activity of the epidermal growth factor receptor (EGFR) are routinely used in cancer therapy. However, there is a need to discover a new TK inhibitor. This study evaluated extracts from Brucea javanica and its components for their potential as novel EGFR-TK inhibitors. The cytotoxic effect of a g aqueous extract and its fractions was assessed by MTT assays with A549 lung cancer cells. The two fractions with the highest cytotoxicity were analyzed by LC/MS and 1H NMR. Brusatol was identified as the main constituent of these fractions, and its cytotoxic and pro-apoptotic activities were confirmed in A549 cells. To elucidate the inhibitory activity of brusatol against EGFR-TK, a specific ADP-GloTM kinase assay was used. In this assay, the IC50 value for EGFR-TK inhibition was 333.1 nM. Molecular dynamic simulations and docking experiments were performed to identify the binding pocket of brusatol to be located in the intracellular TK-domain of EGFR. This study demonstrates that brusatol inhibits EGFR-TK and therefore harbors a potential as a new therapeutic drug for the therapy of EGFR-depending cancers.

Phloretin-induced STAT3 inhibition suppresses pancreatic cancer growth and progression via enhancing Nrf2 activity

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a malignant pancreatic tumor charactered by a rapid progression and high lethal rate. Hyperactivation of STAT3 signaling exerts a vital effect on the growth and progression of PDAC. While dietary flavonoid phloretin has anti-inflammatory and antioxidant activities, it remains unclear whether phloretin has anti-tumor effects on PDAC.

PURPOSE

The focus of the present study is to elucidate the effects of phloretin on PDAC and investigate its underlying molecular mechanisms.

STUDY DESIGN AND METHODS

Effect of phloretin were assessed in the pancreatic cancer cells (PCCs) by colony formation assay, real-time cell analysis, flow cytometry, Immunofluorescence staining, and cell migration assay. The expressions of mRNA and protein were respectively analyzed by quantitative PCR and Western blotting. A xenograft model was used to appraise the antitumor efficacy of phloretin.

RESULTS

Phloretin treatment significantly restrained cell viability and metastasis, induced DNA injury and ROS accumulation, and triggered mitochondrial-dependent apoptosis in PCCs. Mechanistically, phloretin exhibits anti-tumor potential via inactivating STAT3 signaling and enhancing Nrf2 activity. STAT3 overexpression and Nrf2 silencing partially relieved phloretin-induced inhibition on cell growth and metastasis in PCCs. Phloretin remarkably blocked pancreatic tumor growth and metastasis in vivo.

CONCLUSIONS

Phloretin suppresses pancreatic cancer growth and progression through inhibition of STAT3 mediated by enhancing Nrf2 activity. Phloretin may serve as a promising therapeutic agent for PDAC.

NRF2 and STAT3: friends or foes in carcinogenesis?

NRF2 is a transcription factor that plays a pivotal role in carcinogenesis, also through the interaction with several pro-survival pathways. NRF2 controls the transcription of detoxification enzymes and a variety of other molecules impinging in several key biological processes. This perspective will focus on the complex interplay of NRF2 with STAT3, another transcription factor often aberrantly activated in cancer and driving tumorigenesis as well as immune suppression. Both NRF2 and STAT3 can be regulated by ER stress/UPR activation and their cross-talk influences and is influenced by autophagy and cytokines, contributing to shape the microenvironment, and both control the execution of DDR, also by regulating the expression of HSPs. Given the importance of these transcription factors, more investigations aimed at better elucidating the outcome of their networking could help to discover new and more efficacious strategies to fight cancer.

Mechanism of epithelial-mesenchymal transition in cancer and its regulation by natural compounds

Epithelial-mesenchymal transition (EMT) is a complex process with a primordial role in cellular transformation whereby an epithelial cell transforms and acquires a mesenchymal phenotype. This transformation plays a pivotal role in tumor progression and self-renewal, and exacerbates resistance to apoptosis and chemotherapy. EMT can be initiated and promoted by deregulated oncogenic signaling pathways, hypoxia, and cells in the tumor microenvironment, resulting in a loss-of-epithelial cell polarity, cell-cell adhesion, and enhanced invasive/migratory properties. Numerous transcriptional regulators, such as Snail, Slug, Twist, and ZEB1/ZEB2 induce EMT through the downregulation of epithelial markers and gain-of-expression of the mesenchymal markers. Additionally, signaling cascades such as Wnt/β-catenin, Notch, Sonic hedgehog, nuclear factor kappa B, receptor tyrosine kinases, PI3K/AKT/mTOR, Hippo, and transforming growth factor-β pathways regulate EMT whereas they are often deregulated in cancers leading to aberrant EMT. Furthermore, noncoding RNAs, tumor-derived exosomes, and epigenetic alterations are also involved in the modulation of EMT. Therefore, the regulation of EMT is a vital strategy to control the aggressive metastatic characteristics of tumor cells. Despite the vast amount of preclinical data on EMT in cancer progression, there is a lack of clinical translation at the therapeutic level. In this review, we have discussed thoroughly the role of the aforementioned transcription factors, noncoding RNAs (microRNAs, long noncoding RNA, circular RNA), signaling pathways, epigenetic modifications, and tumor-derived exosomes in the regulation of EMT in cancers. We have also emphasized the contribution of EMT to drug resistance and possible therapeutic interventions using plant-derived natural products, their semi-synthetic derivatives, and nano-formulations that are described as promising EMT blockers.

Brusatol: A potential sensitizing agent for cancer therapy from Brucea javanica

Cancer is currently the most important problem endangering human health. As antitumor drugs have always been the most common methods for treating cancers, searching for new antitumor agents is of great significance. Brusatol, a quassinoid from the seeds of Brucea javanica, exhibits a potent tumor-suppressing effect with improved disease outcome. Studies have shown that brusatol not only shows potential tumor inhibition through multiple pharmacological effects, such as promoting apoptosis and inhibiting metastasis but also exhibits significant synergistic antitumor effects in combination with chemotherapeutic agents and overcoming chemical resistance in a wide range of cancer types. In this paper, the antitumor effects and mechanisms of brusatol were reviewed to provide evidence that brusatol has the exact antitumor efficacy of chemotherapeutic agents and show the potential of brusatol to be developed as a promising antitumor drug.

Ferroptosis: a potential therapeutic target for Alzheimer's disease

The most prevalent dementia-causing neurodegenerative condition is Alzheimer's disease (AD). The aberrant buildup of amyloid β and tau hyperphosphorylation are the two most well-known theories about the mechanisms underlying AD development. However, a significant number of pharmacological clinical studies conducted around the world based on the two aforementioned theories have not shown promising outcomes, and AD is still not effectively treated. Ferroptosis, a non-apoptotic programmed cell death defined by the buildup of deadly amounts of iron-dependent lipid peroxides, has received more attention in recent years. A wealth of data is emerging to support the role of iron in the pathophysiology of AD. Cell line and animal studies applying ferroptosis modulators to the treatment of AD have shown encouraging results. Based on these studies, we describe in this review the underlying mechanisms of ferroptosis; the role that ferroptosis plays in AD pathology; and summarise some of the research advances in the treatment of AD with ferroptosis modulators. We hope to contribute to the clinical management of AD.

Brusatol sensitizes endometrial hyperplasia and cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism

Progestin resistance is the main obstacle for the conservative therapy to maintain fertility in women with endometrial cancer. Brusatol was identified as an inhibitor of the NRF2 pathway; however, its impact on progestin resistance and the underlying mechanism remains unclear. Here, we found that brusatol sensitized endometrial cancer to progestin by suppressing NRF2-TET1-AKR1C1-mediated progestin metabolism. Brusatol transcriptionally suppressed AKR1C1 via modifying the hydroxymethylation status in its promoter region through TET1 inhibition. Suppression of AKR1C1 by brusatol resulted in decreased progesterone catabolism and maintained potent progesterone to inhibit endometrial cancer growth. This inhibition pattern has also been found in the established xenograft mouse and organoid models. Aberrant overexpression of AKR1C1 was found in paired endometrial hyperplasia and cancer samples from the same individuals with progestin resistance, whereas attenuated or loss of AKR1C1 was observed in post-treatment samples with well progestin response as compared with paired pre-treatment tissues. Our findings suggest that AKR1C1 expression pattern may serve as an important biomarker of progestin resistance in endometrial cancer.

Fangchinoline abrogates growth and survival of hepatocellular carcinoma by negative regulation of c-met/HGF and its associated downstream signaling pathways

Among all cancers, hepatocellular carcinoma (HCC) remains a lethal disease with limited treatment options. In this study, we have analyzed the possible inhibitory effects of Fangchinoline (FCN) on c-Met, a protein known to regulate the rapid phosphorylation of downstream signals, as well as mediate aberrant growth, metastasis, survival, and motility in cancer. FCN inhibited the activation of c-Met and its downstream signals PI3K, AKT, mTOR, MEK, and ERK under in vitro settings. Moreover, c-Met gene silencing lead to suppression of PI3K/AKT/mTOR and MEK/ERK signaling pathways, and induced apoptotic cell death upon exposure to FCN. In addition, FCN markedly inhibited the expression of the various oncogenic proteins such as Bcl-2/xl, survivin, IAP-1/2, cyclin D1, and COX-2. In vivo studies in HepG2 cells xenograft mouse model showed that FCN could significantly attenuate the tumor volume and weight, without affecting significant loss in the body weight. Similar to in vitro studies, expression level of c-Met and PI3K/AKT/mTOR, MEK/ERK signals was also suppressed by FCN in the tissues obtained from mice. Therefore, the novel findings of this study suggest that FCN can potentially function as a potent anticancer agent against HCC.

The multifaceted role of STAT3 pathway and its implication as a potential therapeutic target in oral cancer

Oral cancer is one of the leading causes of cancer-related deaths, and it has become a matter of serious concern due to the alarming rise in its incidence rate worldwide. Despite recent advancements in oral cancer treatment strategies, there are no significant improvements in patient's survival rate. Among the numerous cell signaling pathways involved in oral cancer development and progression, STAT3 is known to play a multifaceted oncogenic role in shaping the tumor pathophysiology. STAT3 hyperactivation in oral cancer contributes to survival, proliferation, invasion, epithelial to mesenchymal transition, metastasis, immunosuppression, chemoresistance, and poor prognosis. A plethora of pre-clinical and clinical studies have documented the role of STAT3 in the initiation and development of oral cancer and showed that STAT3 inhibition holds significant potential in the prevention and treatment of this cancer. However, to date, targeting STAT3 activation mainly involves inhibiting the upstream signaling molecules such as JAK and IL-6 receptors. The major challenge in targeting STAT3 lies in the complexity of its phosphorylation- and dimerization-independent functions, which are not affected by disrupting the upstream regulators. The present review delineates the significance of the STAT3 pathway in regulating various hallmarks of oral cancer. In addition, it highlights the STAT3 inhibitors identified to date through various preclinical and clinical studies that can be employed for the therapeutic intervention in oral cancer treatment.

Leelamine Exerts Antineoplastic Effects in Association with Modulating Mitogen‑Activated Protein Kinase Signaling Cascade

Mitogen‑activated protein kinase (MAPK) pathway is a prominent signaling cascade that modulates cell proliferation, apoptosis, stress response, drug resistance, immune response, and cell motility. Activation of MAPK by various small molecules/natural compounds has been demonstrated to induce apoptosis in cancer cells. Herein, the effect of leelamine (LEE, a triterpene derived from bark of pine trees) on the activation of MAPK in hepatocellular carcinoma (HCC) and breast cancer (BC) cells was investigated. LEE induced potent cytotoxicity of HCC (HepG2 and HCCLM3) and BC (MDA-MB-231 and MCF7) cells over normal counterparts (MCF10A). LEE significantly enhanced the phosphorylation of p38 and JNK MAPKs in a dose-dependent fashion and it did not affect the phosphorylation of ERK in HCC and BC cells. The apoptosis-driving effect of LEE was further demonstrated by cleavage of procaspase-3/Bid and suppression of prosurvival proteins (Bcl-xL and XIAP). Furthermore, LEE also reduced the SDF1-induced-migration and -invasion of HCC and BC cells. Taken together, the data demonstrated that LEE promotes apoptosis and induces an anti-motility effect by activating p38 and JNK MAPKs in HCC and BC cells.

Development of 1-(4-(Substituted)piperazin-1-yl)-2-((2-((4-methoxybenzyl)thio)pyrimidin-4-yl)oxy)ethanones That Target Poly (ADP-Ribose) Polymerase in Human Breast Cancer Cells

A number of uracil amides cleave poly (ADP-ribose) polymerase and therefore novel thiouracil amide compounds were synthesized and screened for the loss of cell viability in a human-estrogen-receptor-positive breast cancer cell line. The synthesized compounds exhibited moderate to significant efficacy against human breast cancer cells, where the compound 5e IC₅₀ value was found to be 18 μM. Thouracil amide compounds 5a and 5e inhibited the catalytical activity of PARP1, enhanced cleavage of PARP1, enhanced phosphorylation of H2AX, and increased CASPASE 3/7 activity. Finally, in silico analysis demonstrated that compound 5e interacted with PARP1. Hence, specific thiouracil amides may serve as new drug-seeds for the development of PARP inhibitors for use in oncology.

Major Constituents From Brucea javanica and Their Pharmacological Actions

Brucea javanica (Ya-dan-zi in Chinese) is a well-known Chinese herbal medicine, which is traditionally used in Chinese medicine for the treatment of intestinal inflammation, diarrhea, malaria, and cancer. The formulation of the oil (Brucea javanica oil) has been widely used to treat various types of cancer. It has also been found that B. javanica is rich in chemical constituents, including quassinoids, triterpenes, alkaloids and flavonoids. Pharmacological studies have revealed that chemical compounds derived from B. javanica exhibit multiple bioactivities, such as anti-cancer, anti-bacterial, anti-diabetic, and others. This review provides a comprehensive summary on the pharmacological properties of the main chemical constituents presented in B. javanica and their underlying molecular mechanisms. Moreover, the review will also provide scientific references for further research and development of B. javanica and its chemical constituents into novel pharmaceutical products for disease management.

3-Formylchromone Counteracts STAT3 Signaling Pathway by Elevating SHP-2 Expression in Hepatocellular Carcinoma

Simple Summary

STAT3 acts as a potential tumor-promoting transcription factor that gets aberrantly activated in several types of human cancers and plays a crucial role in tumor progression and metastasis. STAT3 expression has been correlated with a dismal prognosis and poor survival. In this study, we have demonstrated that 3-formylchromone inhibits the STAT3 signaling in HCC cells by modulating SHP-2 expression. It also effectively diminished the tumor growth and subsequent reduction in metastasis in the HCC mouse model without exhibiting any major side effects.

Abstract

Hepatocellular carcinoma (HCC) is one of the leading cancers that contribute to a large number of deaths throughout the globe. The signal transducer and activator of transcription 3 (STAT3) is a tumorigenic protein that is overactivated in several human malignancies including HCC. In the present report, the effect of 3-formylchromone (3FC) on the STAT3 signaling pathway in the HCC model was investigated. 3FC downregulated the constitutive phosphorylation of STAT3 and non-receptor tyrosine kinases such as JAK1 and JAK2. It also suppressed the transportation of STAT3 to the nucleus and reduced its DNA-binding ability. Pervanadate treatment overrode the 3FC-triggered STAT3 inhibition, and the profiling of cellular phosphatase expression revealed an increase in SHP-2 levels upon 3FC treatment. The siRNA-driven deletion of SHP-2 led to reinstate STAT3 activation. 3FC downmodulated the levels of various oncogenic proteins and decreased CXCL12-driven cell migration and invasion. Interestingly, 3FC did not exhibit any substantial toxicity, whereas it significantly regressed tumor growth in an orthotopic HCC mouse model and abrogated lung metastasis. Overall, 3FC can function as a potent agent that can display antitumor activity by targeting STAT3 signaling in HCC models.

The multifaceted antineoplastic role of pyrimethamine against different human malignancies

Cancer accounted for nearly 10 million deaths in 2020 and is the second leading cause of death worldwide. The chemotherapeutic agents that are in clinical practice possess a broad range of severe adverse effects towards vital organs which emphasizes the importance of the discovery of new therapeutic agents or repurposing of existing drugs for the treatment of human cancers. Pyrimethamine is an antiparasitic drug used for the treatment of malaria and toxoplasmosis with a well-documented excellent safety profile. In the last five years, numerous efforts have been made to explore the anticancer potential of pyrimethamine in in vitro and in vivo preclinical models and to repurpose it as an anticancer agent. The studies have demonstrated that pyrimethamine inhibits oncogenic proteins such as STAT3, NF-κB, DX2, MAPK, DHFR, thymidine phosphorylase, telomerase, and many more in a different types of cancer models. Moreover, pyrimethamine has been reported to work in synergy with other anticancer agents, such as temozolomide, to induce apoptosis of tumor cells. Recently, the results of phase-1/2 clinical trials demonstrated that pyrimethamine administration reduces the expression of STAT3 signature genes in tumor tissues of chronic lymphocytic leukemia patients with a good therapeutic response. In the present article, we have reviewed most of the published papers related to the antitumor effects of pyrimethamine in malignancies of breast, liver, lung, skin, ovary, prostate, pituitary, and leukemia in in vitro and in vivo settings. We have also discussed the pharmacokinetic profile and results of clinical trials obtained after pyrimethamine treatment. From these studies, we believe that pyrimethamine has the potential to be repurposed as an anticancer drug. This article is protected by copyright. All rights reserved.

Abrogation of STAT3 activation cascade by Ginkgolide C mitigates tumourigenesis in lung cancer preclinical model

OBJECTIVES

Ginkgolide C (GGC) isolated from Ginkgo biloba (Ginkgoaceae) leaf can demonstrate pleiotropic pharmacological actions. However, its anti-oncogenic impact in non-small cell lung cancer (NSCLC) model has not been reconnoitered. As signal transducer and activator of transcription 3 (STAT3) cascade can promote tumour growth and survival, we contemplated that GGC may interrupt this signalling cascade to expend its anti-cancer actions in NSCLC.

METHODS

The effect of GGC on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation and apoptosis was examined. The in-vivo effect of GGC on the growth of human NSCLC xenograft tumours in athymic nu/nu female mice was also investigated.

KEY FINDINGS

GGC attenuated the phosphorylation of STAT3 and STAT3 upstream kinases effectively. Exposure to pervanadate modulated GGC-induced down-regulation of STAT3 activation and promoted an elevation in the level of PTPε protein. Indeed, silencing of the PTPε gene reversed the GGC-promoted abrogation of STAT3 activation and apoptosis. Moreover, GGC exposure significantly reduced NSCLC tumour growth without demonstrating significant adverse effects via decreasing levels of p-STAT3 in mice tissues.

CONCLUSIONS

Overall, the findings support that GGC may exhibit anti-neoplastic actions by mitigation of STAT3 signalling cascade in NSCLC.

PIAS1 alleviates diabetic peripheral neuropathy through SUMOlation of PPAR-γ and miR-124-induced downregulation of EZH2/STAT3

Diabetic peripheral neuropathy (DPN) is a frequently occurring chronic complication of diabetes. In this study, we aim to explore the regulatory mechanism of protein inhibitor of activated STAT1 (PIAS1) in DPN in terms of autophagy and apoptosis of Schwann cells. The SUMOlation of PPAR-γ by PIAS1 was examined, and ChIP was performed to verify the binding of PPAR-γ to miR-124 promoter region. Dual-luciferase gene reporter assay was used to validate the binding affinity between miR-124 and EZH2/STAT3. Following loss‐ and gain‐of-function experiments, in vitro assays in high glucose-treated Schwann cells (SC4) and in vivo assays in db/db and ob/ob mice were performed to detect the effects of PIAS1 on autophagy and apoptosis of Schwann cells as well as symptoms of DPN by regulating the PPAR-γ-miR-124-EZH2/STAT3. The expression of PIAS1, PPAR-γ, and miR-124 was downregulated in the sciatic nerve tissue of diabetic mice. PIAS1 enhanced the expression of PPAR-γ through direct binding and SUMOlation of PPAR-γ. PPAR-γ enhanced the expression of miR-124 by enhancing the promoter activity of miR-124. Furthermore, miR-124 targeted and inversely modulated EZH2 and STAT3, promoting the autophagy of Schwann cells and inhibiting their apoptosis. In vivo experiments further substantiated that PIAS1 could promote the autophagy and inhibit the apoptosis of Schwann cells through the PPAR-γ-miR-124-EZH2/STAT3 axis. In conclusion, PIAS1 promoted SUMOlation of PPAR-γ to stabilize PPAR-γ expression, which upregulated miR-124 to inactivate EZH2/STAT3, thereby inhibiting apoptosis and promoting autophagy of Schwann cells to suppress the development of DPN.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

Tris(dibenzylideneacetone)dipalladium(0) (Tris DBA) Abrogates Tumor Progression in Hepatocellular Carcinoma and Multiple Myeloma Preclinical Models by Regulating the STAT3 Signaling Pathway

Simple Summary

STAT3 is a major oncogenic transcription factor that is constitutively activated in many types of human cancers, including hepatocellular carcinoma (HCC) and multiple myeloma (MM). Many STAT3 inhibitors have gained momentum in clinical trials towards the treatment of various cancers. In the present study, we have investigated the STAT3 inhibitory efficacy of Tris DBA, a palladium-based compound, in HCC and MM cancer cells and preclinical cancer models. Tris(dibenzylideneacetone)dipalladium(0) (Tris DBA) abrogated the STAT3 signaling pathway in both models by elevating the expression of SHP2. Functionally, Tris DBA inhibited cell proliferation, migration, invasion, and regressed tumor metastasis. Although many studies propose Tris DBA as a modulator of MAPK, Akt, phospho-S6 kinase, and N-myristoyltransferase-1, we have comprehensively demonstrated for the first time that Tris DBA is an inhibitor of STAT3 signaling in preclinical cancer models. These results support the consideration of Tris DBA in clinical trials in translational relevance.

Abstract

STAT3 is an oncogenic transcription factor that controls the expression of genes associated with oncogenesis and malignant progression. Persistent activation of STAT3 is observed in human malignancies, including hepatocellular carcinoma (HCC) and multiple myeloma (MM). Here, we have investigated the action of Tris(dibenzylideneacetone) dipalladium 0 (Tris DBA) on STAT3 signaling in HCC and MM cells. Tris DBA decreased cell viability, increased apoptosis, and inhibited IL-6 induced/constitutive activation of STAT3, JAK1, JAK2, and Src in HCC and MM cells. Tris DBA downmodulated the nuclear translocation of STAT3 and reduced its DNA binding ability. It upregulated the expression of SHP2 (protein and mRNA) to induce STAT3 dephosphorylation, and the inhibition of SHP2 reversed this effect. Tris DBA downregulated the expression of STAT3-driven genes, suppressed cell migration/invasion. Tris DBA significantly inhibited tumor growth in xenograft MM and orthotopic HCC preclinical mice models with a reduction in the expression of various prosurvival biomarkers in MM tumor tissues without displaying significant toxicity. Overall, Tris DBA functions as a good inhibitor of STAT3 signaling in preclinical HCC and MM models.

Pyrimidine-2,4-dione targets STAT3 signaling pathway to induce cytotoxicity in hepatocellular carcinoma cells

Signal transducer and activator of transcription 3 (STAT3) is a tumorigenic transcription factor that is persistently activated in various human cancers including hepatocellular carcinoma (HCC). Therefore, STAT3 is considered as a prominent target to counteract the uncontrolled proliferation of cancer cells. In the present report, pyrimidine-2,4-diones (N-methyluracil derivatives) (MNK1-MNK14) were synthesized in an ionic liquid (BMIm PF₆) medium employing a ligand-free Suzuki-Miyaura cross-coupling process. Among the 14 derivatives, compound MNK8 showed good cytotoxicity towards both the tested cell lines and did not display a toxic effect against normal hepatocytes (LO2). MNK8 significantly increased the Sub-G1 cell count in both cell lines and the cytotoxic effect of MNK8 was found to be mediated through the suppression of constitutive phosphorylation of STAT3^Y705. It also decreased the DNA interaction ability of nuclear STAT3 in HCC cells. MNK8 downregulated the levels of apoptosis-related proteins (such as Bcl-2, cyclin D1, survivin) and increased cleaved caspase-3 inferring the apoptogenic effect of MNK8. It also reduced the CXCL12-triggered cell migration and invasion in in vitro assay systems. Overall, MNK8 has been demonstrated as a new inhibitor of STAT3 signaling cascade in HCC cells.

Crocetin imparts antiproliferative activity via inhibiting STAT3 signaling in hepatocellular carcinoma

STAT3 is a key oncogenic transcription factor, often overactivated in several human cancers including hepatocellular carcinoma (HCC). STAT3 modulates the expression of genes that are connected with cell proliferation, antiapoptosis, metastasis, angiogenesis, and immune evasion in tumor cells. In this study, we investigated the effect of crocetin on the growth of HCC cells and dissected its underlying molecular mechanism in imparting a cytotoxic effect. Crocetin suppressed proliferation, promoted apoptosis, and counteracted the invasive capacity of HCC cells. Besides, crocetin downregulated the constitutive/inducible STAT3 activation (STAT3^Y705 ), nuclear accumulation of STAT3 along with suppression of its DNA binding activity in HCC cells with no effect on STAT5 activation. Crocetin suppressed the activity of upstream kinases such as Src, JAK1, and JAK2. Sodium pervanadate treatment terminated the crocetin-propelled STAT3 inhibition suggesting the involvement of tyrosine phosphatases. Crocetin increased the expression of SHP-1 and siRNA-mediated SHP-1 silencing resulted in the negation of crocetin-driven STAT3 inhibition. Further investigation revealed that crocetin treatment inhibited the expression of STAT3 regulated genes (Bcl-2, Bcl-xL, cyclin D1, survivin, VEGF, COX-2, and MMP-9). Taken together, this report presents crocetin as a novel abrogator of the STAT3 pathway in HCC cell lines.

Brusatol Inhibits Tumor Growth and Increases the Efficacy of Cabergoline against Pituitary Adenomas

Cabergoline (CAB) is the first choice for treatment of prolactinoma and the most common subtype of pituitary adenoma. However, drug resistance and lack of effectiveness in other pituitary tumor types remain clinical challenges to this treatment. Brusatol (BT) is known to inhibit cell growth and promote apoptosis in a variety of cancer cells. In our present studies, we investigate the effects of BT on pituitary tumor cell proliferation in vitro and in vivo. BT treatment resulted in an increase in Annexin V-expressing cells and promoted the expression of apoptosis-related proteins in rat and human pituitary tumor cells. Investigation of the mechanism underlying this effect revealed that BT increased the production of reactive oxygen species (ROS) and inhibited the phosphorylation of 4EBP1 and S6K1. Furthermore, treatment with a combination of BT and CAB resulted in greater antitumor effects than either treatment alone in nude mice and pituitary tumor cells. Collectively, our results suggest that the BT-induced ROS accumulation and inhibition of mTORC1 signaling pathway leads to inhibition of tumor growth. Combined use of CAB and BT may increase the clinical effectiveness of treatment for human pituitary adenomas.

Paradoxical functions of long noncoding RNAs in modulating STAT3 signaling pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the lethal and leading types of cancer threatening the globe with a high mortality rate. STAT3 is an oncogenic transcription factor that is aberrantly activated in several human malignancies including HCC. Many STAT3-driven genes control cell proliferation and survival, apoptotic resistance, cell cycle progression, metastasis, and chemotherapeutic resistance. STAT3 signaling is regulated by endogenous modulators such as protein tyrosine phosphatase (PTP), suppressor of cytokine signaling (SOCS), protein inhibitor of activated STAT (PIAS), and various long noncoding RNAs (lncRNAs). Interestingly, lncRNAs have been reported to exhibit oncogenic and tumor suppressor functions, and these effects are mediated through diverse molecular mechanisms including sponging of microRNAs (miRs), transcription activation/inhibition, and epigenetic modifications. In this article, we have discussed the possible role of STAT3 signaling in hepatocarcinogenesis and various mechanisms by which lncRNAs impart their oncogenic or tumor suppressive action by modulating the STAT3 pathway in HCC.

Ferroptosis: mechanisms and links with diseases

Ferroptosis is an iron-dependent cell death, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. The process of ferroptotic cell death is defined by the accumulation of lethal lipid species derived from the peroxidation of lipids, which can be prevented by iron chelators (e.g., deferiprone, deferoxamine) and small lipophilic antioxidants (e.g., ferrostatin, liproxstatin). This review summarizes current knowledge about the regulatory mechanism of ferroptosis and its association with several pathways, including iron, lipid, and cysteine metabolism. We have further discussed the contribution of ferroptosis to the pathogenesis of several diseases such as cancer, ischemia/reperfusion, and various neurodegenerative diseases (e.g., Alzheimer's disease and Parkinson's disease), and evaluated the therapeutic applications of ferroptosis inhibitors in clinics.

Brucein D modulates MAPK signaling cascade to exert multi-faceted anti-neoplastic actions against breast cancer cells

Breast cancer is a prominent type of malignancy among women with a high rate of mortality. A number of previous studies have demonstrated the anticancer potential of brucein D (BD), a quassinoid extracted from Brucea javanica, against the cancers of the pancreas, bone, and liver. We investigated the impact of BD on apoptotic as well on mitogen-activated protein kinase (MAPK) signaling cascades in breast cancer cells. The effect of BD on p38 MAPK and JNK signaling pathways and its downstream functions was deciphered in both MDA-MB-231 and MCF-7 cell lines. We noted that BD decreased the viability of breast cancer cells without affecting the growth of healthy mammary epithelial cells (MCF-10A). Flow cytometric analysis revealed that BD can increase sub-G1 cells and enhanced annexin-V-PI stained cells. The apoptogenic impact of BD was further substantiated by cleavage of procaspase-3/8 and downregulation of antiapoptotic proteins (Bcl-xL, XIAP, and survivin). Furthermore, BD also downmodulated the migratory ability, and chemokine triggered invasion of breast cancer cells. Interestingly, the pharmacological inhibition of p38 MAPK and JNK kinases abrogated the observed anticancer actions of BD. Overall, the data indicated that BD can induce substantial apoptosis and interfere with cellular invasion by modulating MAPK signaling pathway in breast cancer cells.

Development of Potential Antitumor Agents from the Scaffolds of Plant-Derived Terpenoid Lactones

Naturally occurring terpenoid lactones and their synthetic derivatives have attracted increasing interest for their promising antitumor activity and potential utilization in the discovery and design of new antitumor agents. In the present perspective article, selected plant-derived five-membered γ-lactones and six-membered δ-lactones that occur with terpenoid scaffolds are reviewed, with their structures, cancer cell line cytotoxicity and in vivo antitumor activity, structure-activity relationships, mechanism of action, and the potential for developing cancer chemotherapeutic agents discussed in each case. The compounds presented include artemisinin (ART, 1), parthenolide (PTL, 2), thapsigargin (TPG, 3), andrographolide (AGL, 4), ginkgolide B (GKL B, 5), jolkinolide B (JKL B, 6), nagilactone E (NGL E, 7), triptolide (TPL, 8), bruceantin (BRC, 9), dichapetalin A (DCT A, 10), and limonin (LMN, 11), and their naturally occurring analogues and synthetic derivatives. It is hoped that this contribution will be supportive of the future development of additional efficacious anticancer agents derived from natural products.

Interaction of Nrf2 with dimeric STAT3 induces IL-23 expression: Implications for breast cancer progression

Persistent activation of STAT3 and Nrf2 is considered to stimulate the aggressive behavior of basal-like breast cancer (BLBC). However, the precise mechanism underlying sustained overactivation of these transcription factors and their roles in breast cancer progression remain elusive. Analysis of the TCGA multi-omics data showed that high levels of STAT3 and Nrf2 mRNA were correlated with elevated expression of P-STAT3^Y705 and Nrf2 target proteins in breast cancer patients. Our present study demonstrates a unique interaction between Nrf2 and STAT3 in the maintenance and progression of BLBC. RNA sequencing analysis identified the gene encoding IL-23A upregulated by concurrent binding of STAT3 and Nrf2 to its promoter. IL-23A depletion also showed the similar phenotypic changes to those caused by double knockdown of both transcription factors. In conclusion, the STAT3-Nrf2 interaction accelerates BLBC growth and progression by augmenting IL-23A expression, which underscores the importance of subtype-specific molecular pathways in human breast cancer.

Identification of protocatechuic acid as a novel blocker of epithelial-to-mesenchymal transition in lung tumor cells

Protocatechuic acid (PA) is widely distributed and commonly occurring natural compound that can exert antioxidant, anti-inflammatory, as well as anti-cancer effects. Epithelial-to-mesenchymal transition (EMT) is important cellular process that can control tumor invasion and metastasis. Here, we investigated whether PA can modulate the EMT process in basal and transforming growth factorβ-induced A549 and H1299 cells. We found that PA suppressed expression of mesenchymal markers (Fibronectin, Vimentin, and N-cadherin), MMP-9, MMP-2, twist, and snail but stimulated the levels of epithelial markers (E-cadherin and Occludin). In addition, PA can affect TGFβ-induced expression of both mesenchymal and epithelial markers. Moreover, PA abrogated migratory and invasive potential of tumor cells by reversing the EMT process. Furthermore, we found that PA suppressed EMT process by abrogating the activation of PI3K/Akt/mTOR signaling cascade in lung cancer cells.

Potential of guggulsterone, a farnesoid X receptor antagonist, in the prevention and treatment of cancer

Cancer is one of the most dreadful diseases in the world with a mortality of 9.6 million annually. Despite the advances in diagnosis and treatment during the last couple of decades, it still remains a serious concern due to the limitations associated with currently available cancer management strategies. Therefore, alternative strategies are highly required to overcome these glitches. The importance of medicinal plants as primary healthcare has been well-known from time immemorial against various human diseases, including cancer. Commiphora wightii that belongs to Burseraceae family is one such plant which has been used to cure various ailments in traditional systems of medicine. This plant has diverse pharmacological properties such as antioxidant, antibacterial, antimutagenic, and antitumor which mostly owes to the presence of its active compound guggulsterone (GS) that exists in the form of Z- and E-isomers. Mounting evidence suggests that this compound has promising anticancer activities and was shown to suppress several cancer signaling pathways such as NF-κB/ERK/MAPK/AKT/STAT and modulate the expression of numerous signaling molecules such as the farnesoid X receptor, cyclin D1, survivin, caspases, HIF-1α, MMP-9, EMT proteins, tumor suppressor proteins, angiogenic proteins, and apoptotic proteins. The current review is an attempt to summarize the biological activities and diverse anticancer activities (both in vitro and in vivo) of the compound GS and its derivatives, along with its associated mechanism against various cancers.

Genistin attenuates cellular growth and promotes apoptotic cell death breast cancer cells through modulation of ERalpha signaling pathway

Estrogen receptor alpha (ERα) is a vital molecular target in ER-positive breast cancer. Genistin (GS) is one of isoflavones that can exert diverse pharmacological effects including that of anti-proliferation, anti-tumor angiogenesis, induce cell cycle arrest and apoptosis. Here, we examined the efficacy of GS as an anti-cancer agent against breast cancer cells. We observed that GS exhibited more cytotoxic activity against MCF-7 cells than MDA-MB-231cells. We found that GS caused negative regulation of ERα. It also effectively down-modulated ER nuclear translocation as well DNA binding activity in breast cancer cells. Moreover, GS effectively induced apoptosis and suppressed levels of oncogenic markers in MCF-7 cells. Interestingly, in ERα knocked-down MCF-7 cells, cell viability was found to be increased and the levels of cleaved PARP was abolished. We found completely contrasting results in ERα overexpressed MDA-MB-231 cells, where cell viability was decreased and expression level of apoptotic markers was enhanced. Our results demonstrate that GS can suppress ERα signaling and can be useful for prevention and therapy of ER-positive breast cancer.

Apigenin as Tumor Suppressor in Cancers: Biotherapeutic Activity, Nanodelivery, and Mechanisms With Emphasis on Pancreatic Cancer

Pancreatic cancer is the most lethal malignancy of the gastrointestinal tract. Due to its propensity for early local and distant spread, affected patients possess extremely poor prognosis. Currently applied treatments are not effective enough to eradicate all cancer cells, and minimize their migration. Besides, these treatments are associated with adverse effects on normal cells and organs. These therapies are not able to increase the overall survival rate of patients; hence, finding novel adjuvants or alternatives is so essential. Up to now, medicinal herbs were utilized for therapeutic goals. Herbal-based medicine, as traditional biotherapeutics, were employed for cancer treatment. Of them, apigenin, as a bioactive flavonoid that possesses numerous biological properties (e.g., anti-inflammatory and anti-oxidant effects), has shown substantial anticancer activity. It seems that apigenin is capable of suppressing the proliferation of cancer cells via the induction of cell cycle arrest and apoptosis. Besides, apigenin inhibits metastasis via down-regulation of matrix metalloproteinases and the Akt signaling pathway. In pancreatic cancer cells, apigenin sensitizes cells in chemotherapy, and affects molecular pathways such as the hypoxia inducible factor (HIF), vascular endothelial growth factor (VEGF), and glucose transporter-1 (GLUT-1). Herein, the biotherapeutic activity of apigenin and its mechanisms toward cancer cells are presented in the current review to shed some light on anti-tumor activity of apigenin in different cancers, with an emphasis on pancreatic cancer.

Stigmasterol sensitizes endometrial cancer cells to chemotherapy by repressing Nrf2 signal pathway

Background

Chemoresistance reduces the 5-year survival rate of endometrial cancer patient, which is the current major obstacle for cancer therapy. Increasing evidence state that Nrf2 contributes to chemoresistance in several kinds of cancer. However, its role in endometrial cancer cells remains unclarified.

Methods

Immunohistochemistry staining was used to detect the expression of Nrf2 in normal patient and endometrial cancer patient. Stable transfection Ishikawa cell line with high level of Nrf2 was established to evaluate its role in chemoresistance. Dot blot assays were used to assess global hydroxymethylation level after stigmasterol treatment. Cellular growth profile was detected by CCK8 assay. Western blot was used to evaluate the changes of the target molecules after various treatments.

Results

Nrf2 is overexpressed in endometrial cancer tissues compared with the normal endometrium. Overexpression of Nrf2 resulted in decrease sensitivity to cisplatin. In addition, stigmasterol has been identified as a novel Nrf2 inhibitor. It enhanced the sensitivity of endometrial cancer cells to cisplatin, and the underlying mechanism is that stigmasterol declines the Nrf2 protein level.

Conclusions

Our findings identified stigmasterol as a new potential inhibitor of Nrf2 and highlight a critical role of stigmasterol in overcoming chemoresistance in endometrial cancer therapy.

Brusatol: A potential anti-tumor quassinoid from Brucea javanica

Brusatol, a triterpene lactone compound mainly from Brucea javanica, sensitizes a broad spectrum of cancer cells. It is known as a specific inhibitor of nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. In this review, we provide a comprehensive overview on the antitumor effect and molecular mechanisms of brusatol in vitro and in vivo. This review also covers pharmacokinetics studies, modification of dosages forms of brusatol. Increasing evidences have validated the value of brusatol as a chemotherapeutic agent in cancers, which may contribute to drug development and clinical application.

Novel 1,3,4-oxadiazole Targets STAT3 Signaling to Induce Antitumor Effect in Lung Cancer

Lung cancer is the leading type of malignancy in terms of occurrence and mortality in the global context. STAT3 is an oncogenic transcription factor that is persistently activated in many types of human malignancies, including lung cancer. In the present report, new oxadiazole conjugated indazoles were synthesized and examined for their anticancer potential in a panel of cancer cell lines. Among the new compounds, 2-(3-(6-chloro-5-methylpyridin-3-yl)phenyl)-5-(1-methyl-1H-indazol-3-yl)-1,3,4-oxadiazole (CHK9) showed consistently good cytotoxicity towards lung cancer cells with IC50 values ranging between 4.8-5.1 µM. The proapoptotic effect of CHK9 was further demonstrated by Annexin-FITC staining and TUNEL assay. In addition, the effect of CHK9 on the activation of STAT3 in lung cancer cells was examined. CHK9 reduced the phosphorylation of STAT3Y705 in a dose-dependent manner. CHK9 had no effect on the activation and expression of JAK2 and STAT5. It also reduced the STAT3-dependent luciferase reporter gene expression. CHK9 increased the expression of proapoptotic (p53 and Bax) proteins and decreased the expression of the antiapoptotic (Bcl-2, Bcl-xL, BID, and ICAM-1) proteins. CHK9 displayed a significant reduction in the number of tumor nodules in the in vivo lung cancer model with suppression of STAT3 activation in tumor tissues. CHK9 did not show substantial toxicity in the normal murine model. Overall, CHK9 inhibits the growth of lung cancer cells and tumors by interfering with the STAT3 signaling pathway.

Possible applications of salvianolic acid B against different cancers

Cancer is the second death causing disease worldwide after cardiovascular abnormalities. The difficulty in treating tumor cells with more precise targeted interventions and recurrence of cancer after treatment may pose great difficulty in developing sustainable therapeutic regimens. These limitations have prompted the need to explore several compounds with ability to cease tumor growth while at the same time induce apoptosis of tumor cells. Several studies have emphasized the use of natural compounds as antitumor agents due to their high efficacy against cancer cells and low toxicity in normal cells. Salvianolic acid B (SAB), a naturally occurring phenolic compound extracted from the radix of Chinese herb Salvia miltiorrhiza can induce apoptosis in different types of tumor cells. It can be used to treat cardiovascular and neurodegenerative disorders, hepatic fibrosis, and cancers. Several studies have shown that SAB can mitigate tumorigenesis by modulating MAPK, PI3K/AKT, and NF-ĸB signaling pathways. It also sensitizes the tumor cells to different anti-cancer agents by reversing the multi-drug resistance mechanisms found in tumor cells. This review summarizes the studies showing antitumor potential of SAB in different types of cancer cell lines, animal models and highlights the possible mechanisms through which SAB can induce apoptosis, inhibit growth and metastasis in tumor cells. Moreover, the possible role of nano-technological approaches to induce targeted delivery of SAB to eradicate tumor cells has been also discussed.

Nrf2 Inhibitor, Brusatol in Combination with Trastuzumab Exerts Synergistic Antitumor Activity in HER2-Positive Cancers by Inhibiting Nrf2/HO-1 and HER2-AKT/ERK1/2 Pathways

The HER2-targeting antibody trastuzumab has shown effectiveness in treating HER2-positive breast and gastric cancers; however, its responses are limited. Currently, Nrf2 has been deemed as a key transcription factor in promoting cancer progression and resistance by crosstalk with other proliferative signaling pathways. Brusatol as a novel Nrf2 inhibitor has been deemed as an efficacious and safe drug candidate in cancer therapy. In this study, we firstly reported that brusatol exerted the growth-inhibitory effects on HER2-positive cancer cells by regressing Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways in these cells. More importantly, we found that brusatol synergistically enhanced the antitumor activity of trastuzumab against HER2-positive SK-OV-3 and BT-474 cells, which may be attributed to the inhibition of Nrf2/HO-1 and HER2-AKT/ERK1/2 signaling pathways. Furthermore, the synergistic effects were also observed in BT-474 and SK-OV-3 tumor xenografts. In addition, our results showed that trastuzumab markedly enhanced brusatol-induced ROS accumulation and apoptosis level, which could further explain the synergistic effects. To conclude, the study provided a new insight on exploring Nrf2 inhibition in combination with HER2-targeted trastuzumab as a potential clinical treatment regimen in treating HER2-positive cancers.

Brusatol suppresses STAT3-driven metastasis by downregulating epithelial-mesenchymal transition in hepatocellular carcinoma

Introduction

Epithelial-mesenchymal transition (EMT) is a process of transdifferentiation where epithelial cells attain mesenchymal phenotype to gain invasive properties and thus, can contribute to metastasis of tumor cells.

Objectives

The antimetastatic and antitumor efficacy of brusatol (BT) was investigated in a hepatocellular carcinoma (HCC) model.

Methods

We evaluated the action of BT on EMT process using various biological assays in HCC cell lines and its effect on tumorigenesis in an orthotopic mouse model.

Results

We found that BT treatment restored the expression of Occludin, E-cadherin (epithelial markers) while suppressing the levels of different mesenchymal markers in HCC cells and tumor tissues. Moreover, we observed a decline in the expression of transcription factors (Snail, Twist). Since the expression of these two factors can be regulated by STAT3 signaling, we deciphered the influence of BT on modulation of this pathway. BT suppressed the phosphorylation of STAT3^Y705 and STAT3 depletion using siRNA resulted in the restoration of epithelial markers. Importantly, BT (1mg/kg) reduced the tumor burden in orthotopic mouse model with a concurrent decline in lung metastasis.

Conclusions

Overall, our results demonstrate that BT interferes with STAT3 induced metastasis by altering the expression of EMT-related proteins in HCC model.

Flaming the fight against cancer cells: the role of microRNA-93

There have been attempts to develop novel anti-tumor drugs in cancer therapy. Although satisfying results have been observed at a consequence of application of chemotherapeutic agents, the cancer cells are capable of making resistance into these agents. This has forced scientists into genetic manipulation as genetic alterations are responsible for generation of a high number of cancer cells. MicroRNAs (miRs) are endogenous, short non-coding RNAs that affect target genes at the post-transcriptional level. Increasing evidence reveals the potential role of miRs in regulation of biological processes including angiogenesis, metabolism, cell proliferation, cell division, and cell differentiation. Abnormal expression of miRs is associated with development of a number of pathologic events, particularly cancer. MiR-93 plays a significant role in both physiological and pathological mechanisms. At the present review, we show how this miR dually affects the proliferation and invasion of cancer cells. Besides, we elucidate the oncogenesis or oncosuppressor function of miR-93.

MicroRNAs in cancer therapy: Their involvement in oxaliplatin sensitivity/resistance of cancer cells with a focus on colorectal cancer

The resistance of cancer cells into chemotherapy has restricted the efficiency of anti-tumor drugs. Oxaliplatin (OX) being an anti-tumor agent/drug is extensively used in the treatment of various cancer diseases. However, its frequent application has led to chemoresistance. As a consequence, studies have focused in finding underlying molecular pathways involved in OX resistance. MicroRNAs (miRs) are short endogenous non-coding RNAs that are able to regulate vital biological mechanisms such as cell proliferation and cell growth. The abnormal expression of miRs occurs in pathological events, particularly cancer. In the present review, we describe the involvement of miRs in OX resistance and sensitivity. The miRs are able to induce the oncogene factors and mechanisms, resulting in stimulation OX chemoresistance. Also, onco-suppressor miRs can enhance the sensitivity of cancer cells into OX chemotherapy and trigger apoptosis and cell cycle arrest, leading to reduced viability and progression of cancer cells. MiRs can also enhance the efficacy of OX chemotherapy. It is worth mentioning that miRs affect various down-stream targets in OX resistance/sensitivity such as STAT3, TGF-β, ATG4B, FOXO1, LATS2, NF-κB and so on. By identification of these miRs and their upstream and down-stream mediators, further studies can focus on targeting them to sensitize cancer cells into OX chemotherapy and induce apoptotic cell death.

Targeting the JAK/STAT Signaling Pathway Using Phytocompounds for Cancer Prevention and Therapy

Cancer is a prevalent cause of mortality around the world. Aberrated activation of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway promotes tumorigenesis. Natural agents, including phytochemicals, exhibit potent anticancer activities via various mechanisms. However, the therapeutic potency of phytoconstituents as inhibitors of JAK/STAT signaling against cancer has only come into focus in recent days. The current review highlights phytochemicals that can suppress the JAK/STAT pathway in order to impede cancer cell growth. Various databases, such as PubMed, ScienceDirect, Web of Science, SpringerLink, Scopus, and Google Scholar, were searched using relevant keywords. Once the authors were in agreement regarding the suitability of a study, a full-length form of the relevant article was obtained, and the information was gathered and cited. All the complete articles that were incorporated after the literature collection rejection criteria were applied were perused in-depth and material was extracted based on the importance, relevance, and advancement of the apprehending of the JAK/STAT pathway and their relation to phytochemicals. Based on the critical and comprehensive analysis of literature presented in this review, phytochemicals from diverse plant origins exert therapeutic and cancer preventive effects, at least in part, through regulation of the JAK/STAT pathway. Nevertheless, more preclinical and clinical research is necessary to completely comprehend the capability of modulating JAK/STAT signaling to achieve efficient cancer control and treatment.

Versatile role of curcumin and its derivatives in lung cancer therapy

Lung cancer is a main cause of death all over the world with a high incidence rate. Metastasis into neighboring and distant tissues as well as resistance of cancer cells to chemotherapy demand novel strategies in lung cancer therapy. Curcumin is a naturally occurring nutraceutical compound derived from Curcuma longa (turmeric) that has great pharmacological effects, such as anti-inflammatory, neuroprotective, and antidiabetic. The excellent antitumor activity of curcumin has led to its extensive application in the treatment of various cancers. In the present review, we describe the antitumor activity of curcumin against lung cancer. Curcumin affects different molecular pathways such as vascular endothelial growth factors, nuclear factor-κB (NF-κB), mammalian target of rapamycin, PI3/Akt, microRNAs, and long noncoding RNAs in treatment of lung cancer. Curcumin also can induce autophagy, apoptosis, and cell cycle arrest to reduce the viability and proliferation of lung cancer cells. Notably, curcumin supplementation sensitizes cancer cells to chemotherapy and enhances chemotherapy-mediated apoptosis. Curcumin can elevate the efficacy of radiotherapy in lung cancer therapy by targeting various signaling pathways, such as epidermal growth factor receptor and NF-κB. Curcumin-loaded nanocarriers enhance the bioavailability, cellular uptake, and antitumor activity of curcumin. The aforementioned effects are comprehensively discussed in the current review to further direct studies for applying curcumin in lung cancer therapy.