Deoxyelephantopin impedes mammary adenocarcinoma cell motility by inhibiting calpain-mediated adhesion dynamics and inducing reactive oxygen species and aggresome formation

Sesquiterpene Lactones as Promising Phytochemicals to Cease Metastatic Propagation of Cancer

Cancer metastasis remains the most challenging issue in cancer therapy. Recent reports show that cancer metastasis accounts for over 90% of cancer-associated deaths in the world. Metastasis is a multi-step process by which cancer cells spread to distant tissues and organs beyond the primary site. The metastatic propagation of different cancers is under the surveillance of several regulating processes and factors related to cellular signaling pathways. Plant-derived phytochemicals are bioactive components of plants with a variety of biological and medicinal activities. Several phytochemicals have been shown to target various molecular factors in cancer cells to tackle metastasis. Sesquiterpene lactones, as a diverse group of plant-derived phytochemicals with a variety of biological activities, have been shown to suppress the promotion and progression of different cancer types by acting on multiple cell-signaling pathways. This review article briefly describes the process of metastasis and its components. Then, sesquiterpene lactones with the ability to target and inhibit invasion, migration, and metastasis along with the molecular mechanisms of their effects on different cancers are described in detail.

Sesquiterpenoids from the whole plants of Elephantopus mollis with cytotoxicity activities

Five new sesquiterpenoids (1-5), elephantmollides A-E, along with four known compounds (6-9), were isolated from the whole plants of E. mollis. Their planar structures were elucidated using the spectroscopic methods, including HRESIMS, IR, UV, and NMR (1H, 13C, DEPT, HSQC, HMBC, 1H-1H COSY). The relative configurations of them were partially deduced by the NOESY experiment, and the absolute configurations were assigned by comparing the calculated electronic circular dichroism (ECD) results with the experimental data. In addition, cytotoxic activities of 1-9 against HepG2 cells ware tested, and compounds 1-9 exhibited cytotoxic activities with IC50 values ranging from 6.7 to 25.8 μM.

Phytochemicals as Novel Therapeutics for Triple-Negative Breast Cancer: A Comprehensive Review of Current Knowledge

Triple-negative breast cancer is a characteristic subtype of breast cancer that lacks the estrogen receptor, human epidermal growth factor receptor 2, and progesterone receptor. Because of its highly diverse subtypes, increased metastasis capability, and poor prognosis, the risk of mortality for people with triple-negative breast cancers is high as compared with other cancers. Chemotherapy is currently playing a major role in treating triple-negative breast cancer patients; however, poor prognosis due to drug resistance is causing serious concern. Recent studies on several phytochemicals derived from various plants being used in Traditional Chinese Medicine, Traditional Korean Medicine, Ayurveda (Traditional Indian Medicine), and so on, have demonstrated to be a promising agent as a viable therapy against triple-negative breast cancer. Phytochemicals categorized as alkaloids, polyphenols, terpenoids, phytosterols, and organosulfur compounds have been demonstrated to reduce cancer cell proliferation and metastasis by activating various molecular pathways, thereby reducing the spread of triple-negative breast cancer. This review analyzes the molecular mechanisms by which various phytochemicals fight triple-negative breast cancer and offers a perspective on the difficulties and potential prospects for treating triple-negative breast cancer with various phytochemicals.

Phytosesquiterpene lactones deregulate mitochondrial activity and phenotypes associated with triple-negative breast cancer metastasis

BACKGROUND

Triple-negative breast cancer (TNBC) recurrence and metastasis are the major causes of failure in TNBC therapy. The difficulties in treating TNBCs may be because of increased cancer cell plasticity that involves the fine-tuning of cellular redox homeostasis, mitochondrial bioenergetics, metabolic characteristics, and the development of cancer stem cells (CSCs).

PURPOSE

To investigate the effects and the underlying mechanisms of the phytosesquiterpene lactone deoxyelephantopin (DET) and its semi-synthesized derivative (DETD-35) in suppressing different phenotypic TNBC cell populations that contribute to tumor metastasis.

METHODS

A timelapse microfluidic-based system was established to analyze the effects of DETD-35 and DET on cell migration behavior in an oxygen gradient. Seahorse real-time cell metabolic analyzer and gas chromatography/quadrupole-time-of-flight mass spectrometry (GC/Q-TOF MS) were utilized to analyze the effects of the compounds on mitochondrial bioenergetics in TNBC cells. A miRNA knockout technique and miRNA sponges were employed to evaluate the miR-4284 involvement in the anti-TNBC cell effect of either compound.

RESULTS

DETD-35 and DET attenuated TNBC cell migration toward hypoxic regions under a 2-19 % oxygen gradient in a timelapse microfluidic-based system. DETD-35 and DET also suppressed CSC-like phenotypes, including the expression of Sox2, Oct4, and CD44 in TNBC cells under hypoxic conditions. DETD-35 and DET affected mitochondrial basal respiration, ATP production, proton leak, and primary metabolism, including glycolysis, the TCA cycle, and amino acid metabolism in the lung-metastatic TNBC cells. Furthermore, the expression of mitophagy markers PARKIN, BNIP3, PINK1, LC3-II, and apoptotic markers Bax, cleaved caspase 7, and cleaved PARP in hypoxic and lung-metastatic TNBC cells was also regulated by treatment with either compound. In miR-4284 knockout cells or miR-4284 inhibitor co-treated TNBC cells, DET- and DETD-35-induced over-expression of mitophagic and apoptotic markers was partially reversed, indicating miR-4284 involved with the compounds caused programmed cell death.

CONCLUSION

This study demonstrated the novel activities of DETD-35 and DET in suppressing CSC-like phenotypes and metastatic TNBC cells through the de-regulation of mitochondrial bioenergetics.

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development.

The Effects of Deoxyelephantopin on the Akt/mTOR/P70S6K Signaling Pathway in MCF-7 Breast Carcinoma Cells In Vitro

Objective

To determine the effects of deoxyelephantopin on mTOR and its related target molecules (Akt/mTOR/P70S6K) in the ER-positive breast cancer cell line.

Materials and Methods

Primary in silico simulations were determined, and the effects of deoxyelephantopin on the phosphorylation of the Akt/mTOR/P70S6K molecules were evaluated using AlphaScreen-based assays and western blot analysis, respectively.

Results

Based on the estimated FEB and K i values, deoxyelephantopin appeared to have a stronger affinity toward P70S6K as compared with Akt and mTOR. Both deoxyelephantopin and control inhibitors were observed to form hydrogen bonds with the same key residue, Leu175 of the P70S6K molecule. Deoxyelephantopin downregulated the p-P70S6K protein expression significantly from 18 µM ( P < .05) and onward. Based on the AlphaScreen assay, deoxyelephantopin produced a concentration-dependent inhibition on the phosphorylation of P70S6K with an IC50 value of 7.13 µM.

Conclusion

Deoxyelephantopin induced cell death in MCF-7 cells, possibly via DNA fragmentation, inhibition of the phosphorylation of P70SK6, and downregulation of the relative p-p70S6K protein expression levels.

MS/MS-based molecular networking accelerated discovery of germacrane-type sesquiterpene lactones from Elephantopus scaber L

Assisted by an MS/MS-based molecular networking guided strategy, six undescribed germacrane-type sesquiterpene lactones, namely scaberxones A-F, along with a known analog were obtained and characterized from Elephantopus scaber L. Their structures were unequivocally assigned by detailed spectroscopic analyses, NMR and ECD spectral calculations, and computer-assisted structure elucidation (CASE), complemented with single-crystal X-ray diffraction. All compounds were measured for their production of nitric oxide (NO) levels in lipopolysaccharide (LPS)-induced BV-2 microglial cells to assess their anti-neuroinflammatory activity. Scaberxone F showed the most potent inhibition of NO production at a concentration of 10 μM.

Current Advancements of Plant-Derived Agents for Triple-Negative Breast Cancer Therapy through Deregulating Cancer Cell Functions and Reprogramming Tumor Microenvironment

Triple-negative breast cancer (TNBC) is defined based on the absence of estrogen, progesterone, and human epidermal growth factor receptor 2 receptors. Currently, chemotherapy is the major therapeutic approach for TNBC patients; however, poor prognosis after a standard chemotherapy regimen is still commonplace due to drug resistance. Abnormal tumor metabolism and infiltrated immune or stromal cells in the tumor microenvironment (TME) may orchestrate mammary tumor growth and metastasis or give rise to new subsets of cancer cells resistant to drug treatment. The immunosuppressive mechanisms established in the TME make cancer cell clones invulnerable to immune recognition and killing, and turn immune cells into tumor-supporting cells, hence allowing cancer growth and dissemination. Phytochemicals with the potential to change the tumor metabolism or reprogram the TME may provide opportunities to suppress cancer metastasis and/or overcome chemoresistance. Furthermore, phytochemical intervention that reprograms the TME away from favoring immunoevasion and instead towards immunosurveillance may prevent TNBC metastasis and help improve the efficacy of combination therapies as phyto-adjuvants to combat drug-resistant TNBC. In this review, we summarize current findings on selected bioactive plant-derived natural products in preclinical mouse models and/or clinical trials with focus on their immunomodulatory mechanisms in the TME and their roles in regulating tumor metabolism for TNBC prevention or therapy.

Targeting thioredoxin reductase by deoxyelephantopin from Elephantopus scaber triggers cancer cell apoptosis

Elevated expression of thioredoxin reductase (TrxR) is associated with the tumorigenesis and resistance to cancer chemoradiotherapy, highlighting the potential of TrxR inhibitors as anticancer drugs. Deoxyelephantopin (DET) is the major active ingredient of Elephantopus scaber and reveals potent anticancer activity. However, the potential mechanism of action and the cellular target of DET are still unknown. Here, we found that DET primarily targets the Sec residue of TrxR and irreversibly prohibits enzyme activity. Suppression of TrxR by DET leads to accumulation of reactive oxygen species and dysregulation in intracellular redox balance, eventually inducing cancer cell apoptosis mediated by oxidative stress. Noticeably, down-regulation of TrxR1 by shRNA increases cell sensitivity to DET. Collectively, targeting of TrxR1 by DET uncovers a novel mechanism of action in DET and deepens the understanding of developing DET as a potential chemotherapeutic agent for treating cancers.

Targeted isolation of cytotoxic germacranolide sesquiterpenes from Elephantopus scaber L. using small molecule accurate recognition technology

Small molecule accurate recognition technology (SMART) is an emerging method for the rapid structural prediction of major constituents from crude extracts and fractions. In the present study, a targeted isolation of an Elephantopus scaber extract by SMART resulted in the obtention of 15 new (1-15) and five known germacranolide sesquiterpenes (16-20). Their structures were assigned by extensively analyzing HRESIMS, NMR, X-ray crystallographic analyses, modified Mosher's method results, and quantum chemical calculate electronic circular dichroism (ECD) spectra. All germacranolide sesquiterpenes were screened to determine their inhibitory effects with two hepatoma cell lines (HepG2 and Hep3B), and compounds 14, 16, 18, 19 and 20 showed significant cytotoxic activities against the HepG2 (IC50, 3.3-9.9 μM) and Hep3B (IC50, 4.5-8.6 μM) cell lines. Further study suggested that 18 can induce the apoptosis of hepatoma cells via mitochondrial dysfunction.

Elephantopinolide A-P, germacrane-type sesquiterpene lactones from Elephantopus scaber induce apoptosis, autophagy and G2/M phase arrest in hepatocellular carcinoma cells

Chromatographic purification of Elephantopus scaber led to 16 new germacrane-type sesquiterpene lactones (1-16), named elephantopinolide A-P, along with a known analogue (17). Their structures were confirmed by comprehensive spectroscopic analyses, single-crystal X-ray diffraction, and comparison between the experimental and calculated ECD spectra. Their hepatocellular inhibition activities against Hep3B and HepG2 cells were screened by MTT assay, and the structure-activity relationships were examined. The results revealed that 10 (IC50 value of 2.83 μM and 1.98 μM) is more potent than sorafenib. The underlying mechanism study demonstrated that 10 could markedly induce apoptosis accompanied by increased ROS production and decreased mitochondrial membrane potential, resulting in the autophagy and G2/M phase cell arrest in Hep3B and HepG2 cells. Furthermore, signal pathways including MAPKs and AKT may play important roles in 10-induced hepatocellular carcinoma cells death.

Phyto-sesquiterpene lactone deoxyelephantopin and cisplatin synergistically suppress lung metastasis of B16 melanoma in mice with reduced nephrotoxicity

BACKGROUND

Cisplatin (CP) is a chemotherapeutic drug for treating melanoma that also causes adverse side effects in cancer patients.

PURPOSE

This study investigated the bioefficacy of a phytoagent deoxyelephantopin (DET) in inhibiting B16 melanoma cell activity, its synergism with CP against metastatic melanoma, and its capability to attenuate CP side effects in animals.

METHODS

DET and CP bioactivities were assessed by MTT assay, isobologram analysis, time-lapse microscopy, migration and invasion assays, flow cytometry and western blotting. In vivo bioluminescence imaging was used to detect lung metastasis of B16 cells carrying COX-2 reporter gene in syngeneic mice. H&E staining and immunohistochemistry were used to evaluate the compound/drug efficacy and CP side effects. Nephrotoxicity caused by CP treatment in mice was evaluated by UPLC/ESI-QTOF MS - based metabolomics and haematometry.

RESULT

DET, alone or in combination with cisplatin, inhibited B16 cell proliferation, migration, and invasion, and induced cell-cycle arrested at the G₂/M phase and de-regulated cell-cycle mediators in cancer cells. In a murine B16^COX-Luc metastatic allograft model, CP2 (2  mg/kg) treatment inhibited B16 lung metastasis accompanied by severe body weight loss, renal damage and inflammation, and haematological toxicity. DET10 and CP cotreatment (DET10 + CP1) or sequential treatment (CP2→DET10) significantly inhibited formation of pulmonary melanoma foci and reduced renal damage. DET pretreatment (Pre-DET10) or CP2→DET10 treatment had the longest survival (52  vs. 37 days for tumor control mice). CP treatment caused abnormally accumulated urea cycle metabolites and serotonin metabolite hippuric acid in renal tissues that were not seen with DET alone or in combination with CP.

CONCLUSION

The CP and DET combination may be an effective intervention for melanoma with reduced side effects.

Evidence for calpains in cancer metastasis

Metastatic dissemination represents the final stage of tumor progression as well as the principal cause of cancer-associated deaths. Calpains are a conserved family of calcium-dependent cysteine proteinases with ubiquitous or tissue-specific expression. Accumulating evidence indicates a central role for calpains in tumor migration and invasion via participating in several key processes, including focal adhesion dynamics, cytoskeletal remodeling, epithelial-to-mesenchymal transition, and apoptosis. Activated after the increased intracellular calcium concentration ( [ Ca 2 + ] i ) induced by membrane channels and extracellular or intracellular stimuli, calpains induce the limited cleavage or functional modulation of various substrates that serve as metastatic mediators. This review covers established literature to summarize the mechanisms and underlying signaling pathways of calpains in cancer metastasis, making calpains attractive targets for aggressive tumor therapies.

Synthesis and evaluation of new sterol derivatives as potential antitumor agents

The current optimization of tetrazanbigen (TNBG) on the C-ring provided a series of new sterol derivatives 2a–2n. All new synthesized compounds were screened for their anti-proliferation activities against five human cancer cell lines (HepG2, QGY-7701, SMMC-7721, A-431 and NCI-H23 cell lines) in vitro. Among them, 2a, 2b, 2c, 2m and 2n exhibited high anti-proliferation activities on SMMC-7721, and their IC₅₀ values approach that of the positive control drug cisplatin. Compound 2a not only showed strong anti-proliferation activities against QGY-7701 and HepG2 cell lines, with IC₅₀ values (IC₅₀: 6.81 ± 0.24 μM, 7.69 ± 0.87 μM) better than that of cisplatin (IC₅₀: 8.75 μM, 18.89 ± 2.01 μM), but also exhibited good aqueous solubility (0.15–15 mg mL⁻¹ at pH 7.4 and 2.0). On the most sensitive QGY-7701 cell line, Oil red O staining and western blot analysis were performed. The results suggested that 2a can inhibit the growth of cancer cells possibly by interfering with the lipid metabolism balance of tumor cells, resulting in lipid accumulation and cell apoptosis (lipotoxicity). Moreover, after being treated with 2a, lipid accumulation of QGY-7701 cell was increased in a time and dose dependent manner. Based on these promising results, 2a was selected for drug formulation and further pre-clinical development.

The current optimization of tetrazanbigen (TNBG) on the C-ring provided a series of new sterol derivatives 2a–2n.

Phytoagent deoxyelephantopin derivative inhibits triple negative breast cancer cell activity by inducing oxidative stress-mediated paraptosis-like cell death

Triple negative breast cancer (TNBC) is a highly metastatic cancer among the breast cancer subgroups. A thorny issue for clinical therapy of TNBC is lack of an efficient targeted therapeutic strategy. We previously created a novel sesquiterpene lactone analog (named DETD-35) derived from plant deoxyelephantopin (DET) which exhibits potent effects against human TNBC MDA-MB-231 tumor growth in a xenograft mouse model. Here we studied the mechanisms of both DET and DETD-35 against MDA-MB-231 cells. DETD-35 (3-fold decreased in IC50) exhibited better anti-TNBC cell activity than DET as observed through induction of reactive oxygen species production (within 2 h treatment) and damage to the ER structures, resulting in ER-derived cytoplasmic vacuolation and ubiquitinated protein accumulation in the treated cells. Intriguingly, the effects of both compounds were blockaded by pretreatment with ROS scavengers, N-acetylcysteine and reduced glutathione, and protein synthesis inhibitor, cycloheximide. Further, knockdown of MEK upstream regulator RAF1 and autophagosomal marker LC3, and co-treatment with JNK or ERK1/2 inhibitor resulted in the most significant attenuation of DETD-35-induced morphological and molecular or biochemical changes in cancer cells, while the inhibitory effect of DET was not influenced by MAPK inhibitor treatment. Therefore, DETD-35 exerted both ER stress-mediated paraptosis and apoptosis, which may explain its superior activity to DET against TNBC cells. Although the chemotherapeutic drug paclitaxel induced vacuole-like structures in MDA-MB-231 cells, no paraptotic cell death features were detected. This study provides a strategy for combating TNBC through sesquiterpene lactone analogs by induction of oxidative and ER stresses that cause paraptosis-like cell death.

The effects of deoxyelephantopin on the cardiac delayed rectifier potassium channel current (IKr) and human ether-a-go-go-related gene (hERG) expression

Elephantopus scaber Linn and its major bioactive component, deoxyelephantopin are known for their medicinal properties and are often reported to have various cytotoxic and antitumor activities. This plant is widely used as folk medicine for a plethora of indications although its safety profile remains unknown. Human ether-a-go-go-related gene (hERG) encodes the cardiac I_Kr current which is a determinant of the duration of ventricular action potentials and QT interval. The hERG potassium channel is an important antitarget in cardiotoxicity evaluation. This study investigated the effects of deoxyelephantopin on the current, mRNA and protein expression of hERG channel in hERG-transfected HEK293 cells. The hERG tail currents following depolarization pulses were insignificantly affected by deoxyelephantopin in the transfected cell line. Current reduction was less than 40% as compared with baseline at the highest concentration of 50 μM. The results were consistent with the molecular docking simulation and hERG surface protein expression. Interestingly, it does not affect the hERG expression at both transcriptional and translational level at most concentrations, although higher concentration at 10 μM caused protein accumulation. In conclusion, deoxyelephantopin is unlikely a clinically significant hERG channel and I_kr blocker.

Phytoagent Deoxyelephantopin and Its Derivative Inhibit Triple Negative Breast Cancer Cell Activity through ROS-Mediated Exosomal Activity and Protein Functions

A novel plant sesquiterpene lactone derivative, DET derivative (DETD)-35, originating from parental deoxyelephantopin (DET) was previously observed to effectively suppress human triple negative breast cancer (TNBC) MDA-MB-231 cell activity and tumor growth in mice. In this study, the mechanisms underlying the activity of DETD-35 were elucidated. DET and DETD-35 induced reactive oxygen species (ROS) which caused structural damage and dysfunction of mitochondria and increased cytosolic calcium level, subsequently evoking exosome release from the cancer cells. Intriguingly, exosomes induced by both compounds had an atypical function. Cancer cell-derived exosomes commonly show metastatic potential, but upon DET/DETD-35 treatment exosomes showed anti-proliferative activity against MDA-MB-231 cells. Quantitative proteome analysis of TNBC cell-secreted exosomes showed that DET and DETD-35 attenuated the expression of proteins related to cell migration, cell adhesion, and angiogenesis. Furthermore, several exosomal proteins participating in biological mechanisms such as oxidative stress and decrease of transmembrane potential of mitochondria were found deregulated by treatment with either compound. Pretreatment with ROS scavenger, N-acetylcysteine, blockaded DET- or DETD-35-induced oxidative stress and calcium dependent exosome release mechanisms, and also reverted DET- or DETD-35-induced reprogramming exosomal protein expression profiles resulting in attenuation of exosomal toxicity against TNBC cell proliferation. In summary, this study shows that a plant-derived sesquiterpene lactone DET and its analog DETD-35 inhibitory TNBC cell activities through oxidative stress-induced cancer cell releasing exosomes in tandem with alteration of exosomal protein composition and functions. The findings of this study suggest that DETD-35 may be suitable for further development into an anti-TNBC drug.

Novel effect and the mechanistic insights of fruiting body extract of medicinal fungus Antrodia cinnamomea against T47D breast cancer

INTRODUCTION

Tamoxifen, an anti-oestrogenic drug for estrogen receptor positive (ER+) breast cancer, was observed to stimulate tumor growth or drug resistance in patients. Antrodia cinnamomea (AC), a precious medicinal fungus has been traditionally used as a folk remedy for cancers in Asian countries. The objective of this study was to investigate the bioefficacy and the underlying molecular mechanisms of the AC fruiting bodies extracts (AC-3E) against human ER+ T47D breast cancer cells, and compare the effect with that of tamoxifen.

METHODS

Cell proliferation, migration, TUNEL assay, western blotting, time-lapse confocal microscopy analyses, chorioallantoic membrane assay, and a xenograft BALB/c nude mouse system were used in this study. Chemical fingerprinting of AC-3E was established using LC-MS.

RESULTS

AC-3E attenuated T47D breast cancer cell activity by deregulating the PI3K/Akt/mTOR signaling pathway and key cell-cycle mediators, and inducing apoptosis. AC-3E also effectively inhibited tube-like structures of endothelial cells, blood vessel branching and microvessel formation ex vivo and in vivo. Significant preventive and therapeutic effects against T47D mammary tumor growth of AC-3E was observed comparable or superior to tamoxifen treatment in xenograft BALB/c nude mice. Dehydroeburicoic acid (2) was characterized as the main chemical constituent in AC-3E against breast cancer.

CONCLUSION

This study suggests that AC-3E extracts can be employed as a double-barreled approach to treat human ER+ breast cancer by attacking both cancer cells and tumor-associated blood vessel cells.

Deoxyelephantopin induces apoptosis in HepG2 cells via oxidative stress, NF-κB inhibition and mitochondrial dysfunction

Deoxyelephantopin (DET), a naturally occurring sesquiterpene lactone present in Chinese medicinal herb, Elephantopus scaber has been shown to exert anti-inflammatory as well as anticancer effects in various cancer cells of human origin in vitro. However, the exact molecular mechanism underlying DET-induced apoptosis remains largely unexplored, particularly in human hepatocellular carcinoma G2 (HepG2) cells. In the present study, we found that DET inhibits proliferation and induces apoptosis in HepG2 cells in a dose-dependent manner. This DET-mediated apoptosis was found to be associated with reactive oxygen species generation, glutathione depletion and decreased activity of thioredoxin reductase, mitochondrial membrane potential disruption, Bcl-2 family proteins modulation, cytochrome c release, caspases-3 activation, PARP cleavage and inhibition of NF-κB activation. DET inhibited the constitutive as well as induced-translocation of NF-κB into nucleus and augmented the apoptotic effect of Gemcitabine. IKK-16 (NF-κB inhibitor) further enhanced the cytotoxicity of DET and gemcitabine indicating that DET induces apoptosis in HepG2 cells at least partially through inhibition of NF-κB activation. Further mechanistic study demonstrated that DET inhibits the translocation of constitutive as well as induced-NF-κB into nucleus by decreasing phosphorylation of IкBα. Moreover, pretreatment of cells with 3 mM NAC reversed DET-mediated cell death and NF-κB inhibition, indicating that DET exerts its anticancer effects mainly through oxidative stress. Therefore, DET may be developed into a lead chemotherapeutic drug as a single agent or in combination with clinical drugs for the effective treatment of liver cancer. © 2016 BioFactors, 43(1):63-72, 2017.

Phytomedicine-Modulating oxidative stress and the tumor microenvironment for cancer therapy

In spite of the current advances and achievements in systems biology and translational medicinal research, the current strategies for cancer therapy, such as radiotherapy, targeted therapy, immunotherapy and chemotherapy remain palliative or unsatisfactory due to tumor metastasis or recurrence after surgery/therapy, drug resistance, adverse side effects, and so on. Oxidative stress (OS) plays a critical role in chronic/acute inflammation, carcinogenesis, tumor progression, and tumor invasion/metastasis which is also attributed to the dynamic and complex properties and activities in the tumor microenvironment (TME). Re-educating or reprogramming tumor-associated stromal or immune cells in the TME provides an approach for restoring immune surveillance impaired by disease in cancer patients to increase overall survival and reduce drug resistance. Herbal medicines or plant-derived natural products have historically been a major source of anti-cancer drugs. Delving into the lore of herbal medicine may uncover new leads for anti-cancer drugs. Phytomedicines have been widely documented to directly or indirectly target multiple signaling pathways and networks in cancer cells. A combination of anti-cancer drugs and polypharmacological plant-derived extracts or compounds may offer a significant advantage in sensitizing the efficacy of monotherapy and overcoming drug-induced resistance in cancer patients. This review introduces several phytochemicals and phytoextracts derived from medicinal plants or dietary vegetables that have been studied for their efficacy in preclinical cancer models. We address the underlying modes of action of induction of OS and deregulation of TME-associated stromal cells, mediators and signaling pathways, and reference the related clinical investigations that look at the single or combination use of phytochemicals and phytoextracts to sensitize anti-cancer drug effects and/or overcome drug resistance.

A Novel Plant Sesquiterpene Lactone Derivative, DETD-35, Suppresses BRAFV600E Mutant Melanoma Growth and Overcomes Acquired Vemurafenib Resistance in Mice

Acquired resistance to vemurafenib develops through reactivation of RAF/MEK/ERK signaling or bypass mechanisms. Recent combination therapies such as a MEK inhibitor combined with vemurafenib show improvement in major clinical end points, but the percentage of patients with adverse toxic events is higher than with vemurafenib monotherapy and most patients ultimately relapse. Therefore, there is an urgent need to develop new antimelanoma drugs and/or adjuvant agents for vemurafenib therapy. In this study, we created a novel semiorganically modified derivative, DETD-35, from deoxyelephantopin (DET), a plant sesquiterpene lactone demonstrated as an anti-inflammatory and anti-mammary tumor agent. Our results show that DETD-35 inhibited proliferation of a panel of melanoma cell lines, including acquired vemurafenib resistance A375 cells (A375-R) established in this study, with superior activities to DET and no cytotoxicity to normal melanocytes. DETD-35 suppressed tumor growth and reduced tumor mass as effectively as vemurafenib in A375 xenograft study. Furthermore, DETD-35 also reduced tumor growth in both acquired (A375-R) and intrinsic (A2058) vemurafenib resistance xenograft models, where vemurafenib showed no antitumor activity. Notably, the combination of DETD-35 and vemurafenib exhibited the most significant effects in both in vitro and in vivo xenograft studies due to synergism of the compound and the drug. Mechanistic studies suggested that DETD-35 overcame acquired vemurafenib resistance at least in part through deregulating MEK-ERK, Akt, and STAT3 signaling pathways and promoting apoptosis of cancer cells. Overall, our results suggest that DETD-35 may be useful as a therapeutic or adjuvant agent against BRAF(V600E) mutant and acquired vemurafenib resistance melanoma. Mol Cancer Ther; 15(6); 1163-76. ©2016 AACR.

Novel sesquiterpene lactone analogues as potent anti-breast cancer agents

Triple-negative breast cancer (TNBC) is associated with high grade, metastatic phenotype, younger patient age, and poor prognosis. The discovery of an effective anti-TNBC agent has been a challenge in oncology. In this study, fifty-eight ester derivatives (DETDs) with a novel sesquiterpene dilactone skeleton were organically synthesized from a bioactive natural product deoxyelephantopin (DET). Among them, DETD-35 showed potent antiproliferative activities against a panel of breast cancer cell lines including TNBC cell line MDA-MB-231, without inhibiting normal mammary cells M10. DETD-35 exhibited a better effect than parental DET on inhibiting migration, invasion, and motility of MDA-MB-231 cells in a concentration-dependent manner. Comparative study of DETD-35, DET and chemotherapeutic drug paclitaxel (PTX) showed that PTX mainly caused a typical time-dependent G2/M cell-cycle arrest, while DETD-35 or DET treatment induced cell apoptosis. In vivo efficacy of DETD-35 was evaluated using a lung metastatic MDA-MB-231 xenograft mouse model. DETD-35 significantly suppressed metastatic pulmonary foci information along with the expression level of VEGF and COX-2 in SCID mice. DETD-35 also showed a synergistic antitumor effect with PTX in vitro and in vivo. This study suggests that the novel compound DETD-35 may have a potential to be further developed into a therapeutic or adjuvant agent for chemotherapy against metastatic TNBC.

Elephantopus scaber induces apoptosis through ROS-dependent mitochondrial signaling pathway in HCT116 human colorectal carcinoma cells

ETHNOPHARMACOLOGICAL RELEVANCE

Elephantopus scaber also known as Elephant's foot (Asteraceae family) has a plethora of traditional applications including dysuria, diarrhea, dysentery, leukemia and cancer. This study aimed to investigate the apoptosis inducing effects of E. scaber and the underlying mechanisms in HCT116 colorectal cell line.

METHODS

The MTT assay was used to determine the IC50 values on cancer cell lines by the ethanol, hexane, ethyl acetate and water fractions. Apoptosis was detected by cell morphologic observation through Hoechst 33342/PI dual staining, phosphatidylserine externalization by Annexin V/PI staining and DNA fragmentation by TUNEL assay. The caspase activity, Bcl-2 family and p53 proteins were determined by flow cytometric analysis. The cleaved PARP protein expression was assessed by western blot analysis

RESULTS

The ethanol extract of E. scaber and its fractions significantly inhibited the growth of HCT116 and HT-29 cells and induced apoptosis. The E. scaber ethyl acetate fraction (ESEAF) was the most potent on HCT116 cell line with the IC50 value of 1.42 ± 0.10 µg/mL. The induction of apoptosis was marked by nuclear shrinkage accompanied with chromatin condensation, DNA fragmentation and phosphatidylserine externalization. The results showed that ESEAF-induced apoptosis was associated with an upregulation of proapoptotic Bax, elevation of Bax/Bcl-2 ratio, dissipation of mitochondrial membrane potential, activation of caspase-3 and cleavage of poly (ADP-ribose) polymerase (PARP). In addition, a compromised mitochondrial membrane potential and overproduction of ROS demonstrated the involvement of the mitochondrial signaling pathway. Mechanistic studies further revealed that ESEAF caused the augmentation of the intracellular ROS, subsequently incited the increase in p53 protein expression and led to oligomerization of Bax, depolarization of mitochondrial membrane potential and caspases cascade (caspase-3/7 and -9) in a time-dependent manner. The attenuation of intracellular ROS level by N-acetyl-l-cysteine (NAC) preserved the integrity of mitochondrial membrane and rescued the cells from cell death. Furthermore, caspase cascade results in the cleavage of PARP which ultimately activated DNA fragmentation and eventually apoptosis.

CONCLUSION

Taken together, cumulative evidences in this study suggest that ESEAF induces apoptosis through ROS-dependent mitochondrial signaling pathway and holds potential therapeutic effect for colorectal cancer.

Plant regeneration from organogenic callus and assessment of clonal fidelity in Elephantopus scaber Linn., an ethnomedicinal herb

An efficient callus induction and plant regeneration system has been standardized for an ethnomedicinal plant, Elephantopus scaber Linn. Two explants i. e. seeds and leaf segments were used for callus induction. Murashige and Skoog (MS) medium supplemented with 5.0 μM 2, 4-dichlorophenoxy acetic acid (2, 4-D) and 0.5 μM kinetin (Kn) gave the optimum frequency (89 %) of callus induction from seed explant. The results showed that the highest response in terms of percent callus regenerating (91 %) and number of shoots (56) per culture was recorded on MS medium supplemented with 6.0 μM N6-benzylaminopurine (BA) and 1.5 μM α naphthalene acetic acid (NAA). The best rooting of regenerated shoots was obtained on half strength MS medium supplemented with 6.0 μM indole-3- butyric acid (IBA). On this medium, 100 % of the shoots produced roots with a mean number of 3.2 roots per shoot. The positive role of vesicular arbuscular mycorrhizae (VAM) along with potting mix has been well established in the present study. Of the various potting mix employed for plant acclimatization, the highest response of 100 % plant survival was noticed when autoclaved garden soil, sand (2:1) and VAM was utilized as potting mix. Inter-simple sequence repeats (ISSR) were used to establish the clonal fidelity of regenerated plantlets and the banding profiles from callus derived plants were monomorphic and similar to those of mother plant, thus ascertaining the true-to-type nature of these plants.

Phytoagents for cancer management: regulation of nucleic acid oxidation, ROS, and related mechanisms

Accumulation of oxidized nucleic acids causes genomic instability leading to senescence, apoptosis, and tumorigenesis. Phytoagents are known to reduce the risk of cancer development; whether such effects are through regulating the extent of nucleic acid oxidation remains unclear. Here, we outlined the role of reactive oxygen species in nucleic acid oxidation as a driving force in cancer progression. The consequential relationship between genome instability and cancer progression highlights the importance of modulation of cellular redox level in cancer management. Current epidemiological and experimental evidence demonstrate the effects and modes of action of phytoagents in nucleic acid oxidation and provide rationales for the use of phytoagents as chemopreventive or therapeutic agents. Vitamins and various phytoagents antagonize carcinogen-triggered oxidative stress by scavenging free radicals and/or activating endogenous defence systems such as Nrf2-regulated antioxidant genes or pathways. Moreover, metal ion chelation by phytoagents helps to attenuate oxidative DNA damage caused by transition metal ions. Besides, the prooxidant effects of some phytoagents pose selective cytotoxicity on cancer cells and shed light on a new strategy of cancer therapy. The “double-edged sword” role of phytoagents as redox regulators in nucleic acid oxidation and their possible roles in cancer prevention or therapy are discussed in this review.

The effect of p38MAPK on cyclic stretch in human facial hypertrophic scar fibroblast differentiation

Hypertrophic scars (HTS), the excessive deposition of scar tissue by fibroblasts, is one of the most common skin disorders. Fibroblasts derived from surgical scar tissue produce high levels of α-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1). However, the molecular mechanisms for this phenomenon is poorly understood. Thus, the purpose of this study was to evaluate the molecular mechanisms of HTS and their potential therapeutic implications. Fibroblasts derived from skin HTS were cultured and characterized in vitro. The fibroblasts were synchronized and randomly assigned to two groups: cyclic stretch and cyclic stretch pre-treated with SB203580 (a p38MAPK inhibitor). Cyclic stretch at 10% strain was applied at a loading frequency of 10 cycles per minute (i.e. 5 seconds of tension and 5 seconds of relaxation) for 0 h, 6 h and 12 h. Cyclic stretch on HTS fibroblasts led to an increase in the expression of α-SMA and TGF-β1 mRNA and protein and the phosphorylation of p38MAPK. SB203580 reversed these effects and caused a decrease in matrix contraction. Furthermore, HTS fibroblast growth was partially blocked by p38MAPK inhibition. Therefore, the mechanism of cyclic stretch involves p38 MAPK, and its inhibition is suggested as a novel therapeutic strategy for HTS.