Protoapigenone, a novel flavonoid, inhibits ovarian cancer cell growth in vitro and in vivo

Natural Products as Anticancer Agents: Current Status and Future Perspectives

Natural products have been an invaluable and useful source of anticancer agents over the years. Several compounds have been synthesized from natural products by modifying their structures or by using naturally occurring compounds as building blocks in the synthesis of these compounds for various purposes in different fields, such as biology, medicine, and engineering. Multiple modern and costly treatments have been applied to combat cancer and limit its lethality, but the results are not significantly refreshing. Natural products, which are a significant source of new therapeutic drugs, are currently being investigated as potential cytotoxic agents and have shown a positive trend in preclinical research and have prompted numerous innovative strategies in order to combat cancer and expedite the clinical research. Natural products are becoming increasingly important for drug discovery due to their high molecular diversity and novel biofunctionality. Furthermore, natural products can provide superior efficacy and safety due to their unique molecular properties. The objective of the current review is to provide an overview of the emergence of natural products for the treatment and prevention of cancer, such as chemosensitizers, immunotherapeutics, combinatorial therapies with other anticancer drugs, novel formulations of natural products, and the molecular mechanisms underlying their anticancer properties.

The role of nanomaterials in enhancing natural product translational potential and modulating endoplasmic reticulum stress in the treatment of ovarian cancer

Ovarian cancer, and particularly its most frequent type, epithelial ovarian carcinoma, constitutes one of the most dangerous malignant tumors among females. Substantial evidence has described the potential of phytochemicals against ovarian cancer. The effect of natural compounds on endoplasmic reticulum (ER) stress is of great relevance in this regard. In ovarian cancer, the accumulation of misfolded proteins in the ER lumen results in decompensated ER stress. This leads to deregulation in the physiological processes for the posttranslational modification of proteins, jeopardizes cellular homeostasis, and increases apoptotic signaling. Several metabolites and metabolite extracts of phytochemical origin have been studied in the context of ER stress in ovarian cancer. Resveratrol, quercetin, curcumin, fucosterol, cleistopholine, fucoidan, and epicatechin gallate, among others, have shown inhibitory potential against ER stress. The chemical structure of each compound plays an important role concerning its pharmacodynamics, pharmacokinetics, and overall effectiveness. Studying and cross-comparing the chemical features that render different phytochemicals effective in eliciting particular anti-ER stress actions can help improve drug design or develop multipotent combination regimens. Many studies have also investigated the properties of formulations such as nanoparticles, niosomes, liposomes, and intravenous hydrogel based on curcumin and quercetin along with some other phytomolecules in ovarian cancer. Overall, the potential of phytochemicals in targeting genetic mechanisms of ovarian cancer warrants further translational and clinical investigation.

Green Synthesis of a Novel Silver Nanoparticle Conjugated with Thelypteris glandulosolanosa (Raqui-Raqui): Preliminary Characterization and Anticancer Activity

In the last decade, the green synthesis of nanoparticles has had a prominent role in scientific research for industrial and biomedical applications. In this current study, silver nitrate (AgNO3) was reduced and stabilized with an aqueous extract of Thelypteris glandulosolanosa (Raqui-raqui), forming silver nanoparticles (AgNPs-RR). UV-vis spectrophotometry, dynamic light scattering (DLS), and scanning transmission electron microscopy (STEM) were utilized to analyze the structures of AgNPs-RR. The results from this analysis showed a characteristic peak at 420 nm and a mean hydrodynamic size equal to 39.16 nm, while the STEM revealed a size distribution of 6.64–51.00 nm with an average diameter of 31.45 nm. Cellular cytotoxicity assays using MCF-7 (ATCC® HTB-22™, mammary gland breast), A549 (ATCC® CCL-185, lung epithelial carcinoma), and L929 (ATCC® CCL-1, subcutaneous connective tissue of Mus musculus) demonstrated over 42.70% of MCF-7, 59.24% of A549, and 8.80% of L929 cells had cell death after 48 h showing that this nanoparticle is more selective to disrupt neoplastic than non-cancerous cells and may be further developed into an effective strategy for breast and lung cancer treatment. These results demonstrate that the nanoparticle surfaces developed are complex, have lower contact angles, and have excellent scratch and wear resistance.

The protoapigenone analog WYC0209 targets CD133+ cells: A potential adjuvant agent against cancer stem cells in urothelial cancer therapy

Urothelial carcinoma (UC) is one of the highest incidence cancers that rank the fourth commonly diagnosed tumors worldwide. The unresectable lesions that are resistant to therapeutic interventions is the major cause leading to death. Previous studies had shown that the resistance and metastatic consequence may arise from cancer stem-like cells population. The phytochemical flavonoids have promised bioactivity and potent anti-carcinogenic effects, and trap great attentions for cancer chemoprevention and/or adjuvant chemotherapy. However, the mechanisms of flavonoids on cancer stemness is still obscured. In this study, we analyzed the biofunctional effects of as-prepared flavonoid derivative-WYC0209 on T24, BFTC905 and BFTC909 human UC cell lines. Our results demonstrated that WYC0209 significantly induced anti-cell viability on UC cells through decreased Akt/NFkB signaling. Moreover, WYC0209 enhanced the cell apoptosis through activated the caspase-3 activity and inactivated Bcl-xL expression. Interestingly, WYC0209 dramatically inhibited the cancer stem cells (CSCs) traits, including attenuation of side population and tumorsphere formation in which were through declined EMT-CSCs markers including MDR1, ABCG2 and BMI-1. We further validated the effects of WYC0209 on several CSC surface markers including CD133, CD44, SOX-2 and Nanog. Our results showed that WYC0209 markedly inhibited CD133 expressions in both transcriptional and translational levels. High expression levels of CD133 was also demonstrated in human upper tract UC specimens. In summary, our study showed that WYC0209 may potentially as an adjuvant agent to against CD133-driven UC CSCs and provide a beneficial strategy to against UC cancer therapeutics resistant.

Protoflavone-Chalcone Hybrids Exhibit Enhanced Antitumor Action through Modulating Redox Balance, Depolarizing the Mitochondrial Membrane, and Inhibiting ATR-Dependent Signaling

Hybrid compounds combine fragments with complementary targets to achieve a common pharmacological goal. This approach represents an increasingly popular strategy for drug discovery. In this work, we aimed to design antitumor hybrid compounds based on an inhibitor of ataxia-telangiectasia and Rad3-related protein (ATR)-dependent signaling, protoapigenone, and a pro-oxidant ferrocene or chalcone fragment. Four new triazole-coupled hybrids were prepared. The compounds were cytotoxic against human breast cancer cell lines in vitro, showing IC₅₀ values in the sub-micromolar range. The nature of interactions between relevant fragments of the hybrids was evaluated by the Chou–Talalay method. Experimental combination treatment with the fragments showed additive effects or slight/moderate synergism, while strong synergism was observed when the fragments were virtually combined into their hybrids, suggesting a relevant pharmacological benefit of the coupling. All hybrids were strong inhibitors of the ATR-mediated activation of Chk1, and they interfered with the redox balance of the cells leading to mitochondrial membrane depolarization. Additionally, they induced late apoptosis and primary necrosis in MDA-MB-231 and MCF-7 breast cancer cells, respectively. Our results demonstrate that coupling the ATR-dependent signaling inhibitor protoflavone with a pro-oxidant chalcone dramatically increases the antitumor activity compared with either fragment alone. Such compounds may offer an attractive novel strategy for the treatment of various cancers.

The Effect of Green and Black Tea Polyphenols on BRCA2 Deficient Chinese Hamster Cells by Synthetic Lethality through PARP Inhibition

Tea polyphenols are known antioxidants presenting health benefits due to their observed cellular activities. In this study, two tea polyphenols, epigallocatechin gallate, which is common in green tea, and theaflavin, which is common in black tea, were investigated for their PARP inhibitory activity and selective cytotoxicity to BRCA2 mutated cells. The observed cytotoxicity of these polyphenols to BRCA2 deficient cells is believed to be a result of PARP inhibition induced synthetic lethality. Chinese hamster V79 cells and their BRCA2 deficient mutant V-C8, and V-C8 with gene complemented cells were tested against epigallocatechin gallate and theaflavin. In addition, Chinese hamster ovary (CHO) wild-type cells and rad51D mutant 51D1 cells were used to further investigate the synthetic lethality of these molecules. The suspected PARP inhibitory activity of epigallocatechin and theaflavin was confirmed through in vitro and in vivo experiments. Epigallocatechin gallate showed a two-fold increase of cytotoxicity to V-C8 cells compared to V79 and gene complimented cells. Compared to CHO wild type cells, 51D1 cells also showed elevated cytotoxicity following treatment with epigallocatechin gallate. Theaflavin, however, showed a similar increase of cytotoxicity to VC8 compared to V79 and gene corrected cells, but did not show elevation of cytotoxicity towards rad51D mutant cells compared to CHO cells. Elevation of sister chromatid exchange formation was observed in both tea polyphenol treatments. Polyphenol treatment induced more micronuclei formation in BRCA2 deficient cells and rad51D deficient cells when compared against the respective wild type cells. In conclusion, tea polyphenols, epigallocatechin gallate, and theaflavin may present selective cytotoxicity to BRCA2 deficient cells through synthetic lethality induced by PARP inhibition.

HPLC analysis, optimization of extraction and purification conditions, biological evaluation of total protoflavones from Macrothelypteris viridifrons

The present study aims to evaluate phytochemical and pharmacological potential of total protoflavones from Macrothelypteris viridifrons. In the phytochemical study, an HPLC analysis method was established, and the optimal extraction and purification conditions were analyzed. The extractive condition was optimized as follows: the backflow extraction with 20 folds of 70% ethanol at 80◦C for 1 h twice. Moreover, by combining the alkali-extraction and acid-precipitation method with the macroporous resin purification technology, the final purity rate of total protoflavones was no less than 54.85%. In the pharmacological study, the total protoflavones from M. viridifrons showed a significant tumor-inhibitory effect in the H22 hepatoma cells transplantation model with a higher inhibitory rate of 55.76% in high dosage (100mg/kg) treatment group compared with the positive control group (20 mg/kg cyclophosphamide). Taken of all, these results support that protoflavones are the material basis of M. viridifrons as an anticancer folk medicine.

The use of natural compounds for the targeting and chemoprevention of ovarian cancer

Among gynaecological cancers, ovarian cancer represents the leading cause of death in women. Current treatment for ovarian cancer entails surgery followed by combined chemotherapy with platinum and taxane, which are associated, particularly cisplatin, with severe side effects. While this treatment approach appears to be initially effective in a high number of patients, nearly 70% of them suffer a relapse within a few months after initial treatment. Therefore, more effective and better-tolerated treatment options are clearly needed. In recent years, several natural compounds (such as curcumin, epigallocatechin 3-gallate (EGCG), resveratrol, sulforaphane and Withaferin-A), characterized by long-term safety and negligible and/or inexistent side effects, have been proposed as possible adjuvants of traditional chemotherapy. Indeed, several in vitro and in vivo studies have shown that phytocompounds can effectively inhibit tumor cell proliferation, stimulate autophagy, induce apoptosis, and specifically target ovarian cancer stem cells (CSCs), which are generally considered to be responsible for tumor recurrence in several types of cancer. Here we review current literature on the role of natural products in ovarian cancer chemoprevention, highlighting their effects particularly on the regulation of inflammation, autophagy, proliferation and apoptosis, chemotherapy resistance, and ovarian CSC growth.

Anti-tumor and Immunomodulatory Effect of Flavonoid Extracts from Patrinia heterophylla on Cervical Carcinoma Bearing Mice

Patrinia heterophylla Bunge, a traditional Chinese herb, has long been used for therapy of many kinds of diseases, including cancer. Its extract or pure compound has displayed anti-proliferative effect on cancer cells as well. However, the underlying mechanism(s) by which P. heterophylla Bunge exhibited anti-tumor activity in vivo remains to be further elucidated. Herein, we investigated the effect of total flavonoid from P. heterophylla Bunge, named as PHBF, on mice bearing cervical cancer. As a result, the oral administration of PHBF (250 and 500 mg/kg BW) had significant inhibitory effect on tumor volume and weight. In addition, PHBF treatment increased thymus index of tumor-bearing mice in a dose-dependent manner ( P<0.01). Further analysis revealed that cervical cancer cell from tumor-bearing mice treated with PHBF underwent significant apoptosis, which was accompanied by the decrease of PCNA and Bcl-2 expression and increase of Bax and cleaved caspase 3 expression. Interestingly, PHBF treatment also induced more CD4+ and CD8+ T lymphocytes in peripheral blood mononuclear cells (PBMC) of tumor-bearing mice. Furthermore, we observed that the serum level of interferon gamma (IFN-γ) and interleukin-2 (IL-2) was significant higher in mice treated with PHBF than those of control group, implicating that PHBF could function as an immunomodulatory agent. Taken together, these data suggested that PHBF harbored anti-tumor properties against cervical cancer and up-regulated immune response, therefore paving a path to develop as a potential therapeutic and preventive agent for cervical treatment.

Phytochemicals from fern species: potential for medicine applications

Ferns are an important phytogenetic bridge between lower and higher plants. Historically they have been used in many ways by humans, including as ornamental plants, domestic utensils, foods, and in handicrafts. In addition, they have found uses as medicinal herbs. Ferns produce a wide array of secondary metabolites endowed with different bioactivities that could potentially be useful in the treatment of many diseases. However, there is currently relatively little information in the literature on the phytochemicals present in ferns and their pharmacological applications, and the most recent review of the literature on the occurrence, chemotaxonomy and physiological activity of fern secondary metabolites was published over 20 years ago, by Soeder (Bot Rev 51:442-536, 1985). Here, we provide an updated review of this field, covering recent findings concerning the bioactive phytochemicals and pharmacology of fern species.

RY10-4 Inhibits the Proliferation of Human Hepatocellular Cancer HepG2 Cells by Inducing Apoptosis In Vitro and In Vivo

This study aimed to investigate the anti-tumor activity of RY10-4, a small molecular that was designed and synthesized based on the structure of protoapigenone. A previous screening study showed that RY10-4 possessed anti-proliferative effects against HepG2 human hepatocellular carcinoma cells. However, the full range of RY10-4 anti-cancer effects on liver tumors and the underlying mechanisms have not been identified. Herein, employing flow cytometry, and Western blot analysis, we demonstrate that RY10-4 can induce cell cycle arrest, intracellular reactive oxygen species (ROS) production and apoptosis in HepG2 cells. In HepG2 cell xenograft tumor model, RY10-4 significantly inhibited the growth of tumors and induced apoptosis in tumor cells, with little side effects. Moreover, RY10-4 caused the suppression of STAT3 activation, which may be involved the apoptosis induction. In addition, RY10-4 inhibited the proliferation of Hep3B and HuH-7 human hepatocellular carcinoma cells in a concentration-dependent manner. Taken together, our results suggest that RY10-4 has a great potential to develop as chemotherapeutic agent for liver cancer.

Activities of wogonin analogs and other flavones against Flavobacterium columnare

In our on-going pursuit to discover natural products and natural product-based compounds to control the bacterial species Flavobacterium columnare, which causes columnaris disease in channel catfish (Ictalurus punctatus), we synthesized flavone and chalcone analogs, and evaluated these compounds, along with flavonoids from natural sources, for their antibacterial activities against two isolates of F. columnare (ALM-00-173 and BioMed) using a rapid bioassay. The flavonoids chrysin (1a), 5,7-dihydroxy-4'-methoxyflavone (11), isorhamnetin (26), luteolin (27), and biochanin A (29), and chalcone derivative 8b showed strong antibacterial activities against F. columnare ALM-00-173 based on minimum inhibition concentration (MIC) results. Flavonoids 1a, 8, 11, 13 (5,4'-dihydroxy-7-methoxyflavone), 26, and 29 exhibited strong antibacterial activities against F. columnare BioMed based upon MIC results. The 24-h 50% inhibition concentration (IC50 ) results revealed that 27 and 29 were the most active compounds against F. columnare ALM-00-173 (IC50 of 7.5 and 8.5 mg/l, resp.), while 26 and 29 were the most toxic compound against F. columnare BioMed (IC50 of 9.2 and 3.5 mg/l, resp.). These IC50 results were lower than those obtained for wogonin against F. columnare ALM-00-173 and F. columnare BioMed (28.4 and 5.4 mg/l, resp.). However, based on MIC results, none of the compounds evaluated in this study were as active as wogonin (MIC 0.3 mg/l for each F. columnare isolate). Further modification of the wogonin structure to enhance antibacterial is of interest.

Increased adiponectin associated with poor survival in hepatocellular carcinoma

BACKGROUND

Alterations of adiponectin (APN), one of the adipokines, have been associated with human cancers. However, the clinical significance and impacts of APN on hepatocellular carcinoma (HCC) remain undetermined.

METHODS

Using immunohistochemistry, expression patterns of APN were semiquantitatively scored and further statistically correlated with clinicopathological characteristics and patient survival. Furthermore, the bioeffects and underlying mechanisms of ectopic APN overexpression were determined in Hep3B and HepG2 cells by XTT, immunoblotting, flowcytometry, and invasion assays with or without chemical inhibitors and neutralization antibody.

RESULTS

We found that cytoplasmic APN staining in 85 cancerous lesions was increased and associated with a poor survival rate (P = 0.007), even when using the Cox regression model (OR = 3.590; 95 % CI = 1.240-10.394; P = 0.018). Ectopic overexpression of APN in Hep3B and HepG2 cells increased proliferation and invasion as well as the levels of p-AKT (Ser473), p-STAT3 (Tyr705), and those downstream, i.e., cyclin D1 and β-catenin. Similar results were also demonstrated in a stable APN-overexpressing clone, HepG2#136. APN neutralization antibody and LY294002 blocked the APN-mediated effects via inhibition of activated AKT.

CONCLUSIONS

Our results suggest that increased APN may contribute to HCC at least in part through its activation of AKT signalling and may serve as a prognostic factor in HCC.

Cytotoxic non-aromatic B-ring flavanones from Piper carniconnectivum C. DC

The EtOAc extract from the leaves of Piper carniconnectivum C. DC. was subjected to chromatographic separation to afford two non-aromatic B-ring flavanone compounds: 5-hydroxy-2-(1'-hydroxy-4'-oxo-cyclohex-2'-en-1'-yl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (1) and 5-hydroxy-2-(1',2'-dihydroxy-4'-oxo-cyclohexyl)-6,7-dimethoxy-2,3-dihydro-4H-chromen-4-one (2). The absolute configuration of (+)-1 was unambiguously determined as 2S,1'R by electronic circular dichroism (ECD) spectroscopy and comparison to simulated spectra that were calculated using time-dependent density functional theory (TDDFT). This methodology allowed the assignment of the absolute configuration of (+)-2 also as 2S,1'R, except for the stereogenic center at C-2', which was assigned as R because of the evidence drawn from high resolution NMR experiments. The cytotoxic activity of both compounds and 3 (hydrogenated B-ring derivative of 1) was evaluated on twelve human leukemia cell lines, and the IC50 values (<10 μM) indicated the activity of 1 against seven cell lines.

A novel compound RY10-4 induces apoptosis and inhibits invasion via inhibiting STAT3 through ERK-, p38-dependent pathways in human lung adenocarcinoma A549 cells

Previous reports suggested that protoapigenone showed remarkable antitumor activities against a broad spectrum of human cancer cell lines, but had no effect on human lung adenocarcinoma A549 cell. The lack of effective remedies had necessitated the application of new therapeutic scheme. A novel compound RY10-4 which has the similar structure close to protoapigenone showed better antitumor activity. Treatment with RY10-4 inhibited the expression of pro-caspase-3, pro-caspase-9, Bcl-2 as well as phosphorylation of signal transducer and activator of transcription-3 (p-STAT3). It also reduced the expressions of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and increases the expressions of reversion-inducing cysteine-rich protein with kazal motifs (RECK), as well as tissue inhibitor of metalloproteinase (TIMP) via inhibiting STAT3 by activating the mitogen-activated protein (MAP) kinases (the c-Jun N-terminal kinase (JNK), the p38 and extracellular signal-regulated kinase (ERK)) in A549 cells treated with RY10-4. Moreover, the cytotoxic effect of RY10-4 was induction of apoptosis in A549 cells by enhancing production of reactive oxygen species (ROS). Taken together, the observations suggested that RY10-4 had affected Bcl-2 family members, caspases, MMPs, TIMPs expressions and ROS production via inhibiting STAT3 activities through ERK and p38 pathways in A549 cells.

Determination of protoapigenone in rat plasma by high-performance liquid chromatography with UV detection and its application in pharmacokinetic studies

A simple and sensitive HPLC method using UV detection was developed to determine the concentration of protoapigenone in rat plasma. Chromatographic separation was conducted on a C18 column with a mobile phase consisting of an acetonitrile-methanol-aqueous phase (containing 0.2% acetic acid, pH 3.0) system at a flow rate of 1.0 mL/min. The UV detector was set at 248 nm. The calibration curve was linear over the range of 0.031-10.0 µg/mL. The lower limit of quantification was 31 ng/mL. The recoveries for plasma samples ranged from 70.3 to 82.5%. The intra- and inter-day accuracy and precision fulfilled the international standards. This method was successfully applied to a pharmacokinetic study of protoapigenone in rats after oral administration of protoapigenone. It was shown that protoapigenone could be absorbed rapidly after oral administration and could reach the maximum concentration within 1 h.

Ferns and lycopods--a potential treasury of anticancer agents but also a carcinogenic hazard

Many species of seedless vascular plants-ferns and lycopods-have been used as food and folk medicine since ancient times. Some of them have become the focus of intensive research concerning their anticancer properties. Studies on the anticancer effect of crude extracts are being increasingly replaced by bioactivity-guided fractionation, as well as detailed assessment of the mechanism of action. Numerous compounds-especially flavonoids such as amentoflavone and protoapigenone, and also simpler phenolic compounds, steroids, alkaloids and terpenoids-were isolated and found to be cytotoxic, particularly pro-apoptotic, or to induce cell cycle arrest in cancer cell lines in vitro. In in vivo experiments, some fern-derived compounds inhibited tumour growth with little toxicity. On the other hand, many ferns-not only the well-known Bracken (Pteridium)-may pose a significant hazard to human health due to the fact that they contain carcinogenic sesquiterpenoids and their analogues. The objective of this review is to summarise the recent state of research on the anticancer properties of ferns and lycopods, with a focus on their characteristic bioactive constituents. The carcinogenic hazard posed by ferns is also mentioned.

HPLC-UV-ESI-MS methods for flavonoid profiling of sugarcane juice extract

An efficient method combining liquid chromatography coupled to electrospray ionization mass spectrometry in tandem mode with negative ion detection was described for the qualitative analysis of flavonoids in sugarcane juice. The analyses were carried out on a Shim-pack C18 column (150mm×4.6mmI.D.,5µm), with a mobile phase composed by methanol: 5% aqueous acetic acid by linear gradient elution (0–20min, methanol 15–25%; 20–60min, methanol 25–33%; 60–90min, methanol 33–48%). Nine phenolic compounds were identified on the basis of their mass spectra in full scan mode and the pattern of their fragmentation. The diagnostic fragmentation patterns of the compounds during collision induced dissociation (CID) elucidated structural information of the compounds analysed. This is the first time that vitexin-rhamnosyl glucoside (8-glucopyranosyl-7-[6-O-(6-deoxy-mannopyranosyl)-glucopyranosyl]-5-hydroxy-2-(4-hydroxyphenyl)-4H-1-Benzopyran-4-one) has been detected or identified in sugarcane juice.

A new protoapigenone analog RY10-4 induces apoptosis and suppresses invasion through the PI3K/Akt pathway in human breast cancer

RY10-4, a novel protoapigenone analog, shows potent cytotoxicity against a broad spectrum of human cancer cells. Here we investigate its anti-tumor activity on breast cancer. The results indicated that RY10-4 suppressed proliferation, arrested cell cycle, induced apoptosis and inhibited invasion in MDA-MB-231, MCF-7 and SKBR3 breast cancer cells. Western blot analysis showed that RY10-4 down-regulated the PI3K/Akt signaling pathway and inhibited doxorubicin-induced p-Akt. Moreover, it effectively suppressed tumor growth in mice without major side effects. Therefore, RY10-4 had potential anti-tumor activity, and could be used as a lead to design more potent derivatives.

Inhibition of ATR-dependent signaling by protoapigenone and its derivative sensitizes cancer cells to interstrand cross-link-generating agents in vitro and in vivo

DNA damage caused during cancer treatment can rapidly activate the ataxia telangiectasia-mutated (ATM) and ATM and Rad3-related (ATR)-dependent phosphorylation of Chk2 and Chk1 kinases, which are hallmarks of the DNA damage response (DDR). Pharmacologic inhibition of ATR causes a synthetic lethal effect on ATM- or p53-defective cancers, suggesting that such inhibition is an effective way to improve the sensitivity of cancers to DNA-damaging agents. Here, both the natural compound protoapigenone (WYC02) and its synthetic derivative WYC0209 exhibited cytotoxic effects on various cancer cell lines. WYC02 causes chromosomal aberration in the mitotic spreads of Chinese hamster ovary cells. Interestingly, cancer cells did not exhibit typical DDR markers upon exposure to WYC02 and WYC0209 (WYCs). Further investigation into the molecular mechanisms of WYCs function revealed that they have a potential ability to inhibit DDR, particularly on activation of Chk1 and Fanconi anemia group D2 protein (FANCD2), but not Chk2. In this way, WYCs inhibited ATR-mediated DNA damage checkpoint and repair. Furthermore, when combined with the DNA cross-linking agent cisplatin, treatment with WYCs resulted in increased tumor sensitivity to interstrand cross-link-generating agents both in vitro and in vivo. Our results therefore especially implicate WYCs in enhancing tumor chemosensitivity when the ATR checkpoint is constitutively active in states of oncogene-driven replicative stress or tolerance to DNA-interfering agents.

Anti-tumor and anti-angiogenic effects of Macrothelypteris viridifrons and its constituents by HPLC-DAD/MS analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Macrothelypteris viridifrons is widely distributed in south of China and has been used as folk medicine to treat cancer, hydropsy, and traumatic bleeding.

AIM OF THE STUDY

To investigate the chemical constituents and the anti-tumor and anti-angiogenic effects of Macrothelypteris viridifrons.

MATERIALS AND METHODS

An HPLC-DAD/MS technique was used to determine the flavonoid profile of Macrothelypteris viridifrons. The anti-tumor effect of Macrothelypteris viridifrons was evaluated by in vivo mice bearing H22 hepatoma cells transplantation tumor model. And the anti-angiogenic activity was investigated by measuring the effects on the in vitro proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs). Furthermore, the in vivo zebrafish model was applied to evaluate the anti-angiogenic effect of Macrothelypteris viridifrons.

RESULTS

18 flavonoids were identified from Macrothelypteris viridifrons. Administration of Macrothelypteris viridifrons significantly inhibited the tumor growth and the expression of vascular endothelial growth factor (VEGF) and CD34. Meanwhile, Macrothelypteris viridifrons showed significant inhibition on proliferation, migration and tube formation of HUVECs in vitro and the intersegmental vessels formation in zebrafish model.

CONCLUSIONS

Macrothelypteris viridifrons showed significant anti-tumor and anti-angiogenic effects and might be developed as a novel anti-tumor drug.

The promoting effect of adiponectin in hepatocellular carcinoma

BACKGROUND AND OBJECTIVES

Adipokines may explain the newly established association of obesity with hepatocellular carcinoma (HCC). This study investigated if adiponectin levels in HCC patients differed from healthy controls and their potential effect in the development of HCC.

METHODS

Radioimmunoassay was used to determine serum adiponectin levels of 65 HCC patients and 165 healthy controls. The expressions of adiponectin protein in the tumor and adjacent non-tumor parts were examined by the immunoblotting method. Cell proliferation assays were used to assess the bioeffects of adiponectin in two human liver cancer cell lines.

RESULTS

Serum adiponectin levels were significantly higher in the HCC patients than the controls. Significant correlations of serum adiponectin levels with serum triglyceride levels and insulin resistance were found in the controls, but not in the HCC patients. In contrast, serum adiponectin levels significantly correlated with serum albumin and alkaline phosphatase levels in the HCC patients, but this trend was not observed in the controls. The expression pattern of adiponectin protein between the paired tumor and adjacent non-tumor tissues significantly correlated with tumor size. In vitro, adiponectin increased cell proliferation in a dose-dependent manner.

CONCLUSIONS

Increased adiponectin expressions were found in HCC and this increase might contribute to tumor growth.

Direct semi-synthesis of the anticancer lead-drug protoapigenone from apigenin, and synthesis of further new cytotoxic protoflavone derivatives

Protoapigenone, a natural flavonoid possessing an unusual p-quinol moiety on its B-ring, is a novel prospective anticancer agent with low toxicity that is currently in development. The first economical, one-step synthesis of protoapigenone from apigenin is described on up to gram scale. 13 new 1′-O-alkylflavone analogs were also synthesized, either from apigenin or β-naphthoflavone. The in vitro cytotoxic activity of each compound was tested on six human cancer cell lines (HepG2, Hep3B, Ca9-22, A549, MCF-7 and MDA-MB-231). In the case of 1′-O-alkyl-protoapigenone derivatives, structure-activity relationships were found depending on the side-chain, and protoapigenone 1′-O-butyl ether was found to exert significantly stronger activity against three of the cell lines (Hep3B, MCF-7 and MDA-MB-231) than its non-substituted analog, protoapigenone itself. In contrast to this, all β-naphthoflavone derivatives bearing the same pharmacophore on their B-ring showed decreased cytotoxic activities when substituted with an O-alkyl side-chain at position 1′, comparing to that of the non-substituted compound.

A novel non-aromatic B-ring flavonoid: isolation, structure elucidation and its induction of apoptosis in human colon HT-29 tumor cell via the reactive oxygen species-mitochondrial dysfunction and MAPK activation

The aim of the present study was to elucidate the chemical structure of a novel non-aromatic B-ring flavonoid (DHEC) isolated from Macrothelypteris viridifrons and to evaluate its putative molecular mechanism of action on induction of apoptosis in human colon HT-29 cancer cell. On the basis of MS, UV, IR, 1D and 2D NMR data, DHEC was identified as 2-(cis-1, 2-dihydroxy-4-oxo-cyclohex-5-enyl)-5-hydroxy-7-ethoxy-chromone. In addition, the cytotoxicity of DHEC and its effect on induction of apoptosis were confirmed by several assays. After treatment of HT-29 cell with DHEC, we observed the accumulation of intracellular reactive oxygen species, the loss of mitochondrial membrane potential, the alteration of expression of the Bcl-2 family members, the releasing of cytochrome c, the cleavage of poly (ADP-ribose) polymerase (PARP), and the activation of caspase-3, -8, and -9. Further analysis showed that the mitogen-activated protein kinase (MAPK) related proteins were stimulated by treatment with DHEC. These results suggest that DHEC exhibits potential anti-cancer activity in HT-29 cell through induction of apoptosis, which may highly be associated with reactive oxygen species-mitochondrial dysfunction as well as activation of MAPK signaling pathway.

Anticancer activity of total flavonoids isolated from Xianhe Yanling Recipe (仙鹤延龄方)

OBJECTIVE

To investigate the anticancer activity of the total flavonoids isolated from a herbal formula, Xianhe Yanling Recipe (仙鹤延龄方), a recipe commonly used in cancer patients in China.

METHODS

The in vitro anticancer activity of the total flavonoids was determined using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on three cancer cell lines: MCF-7 (a human breast adenocarcinoma cell line), HepG-2 (a human hepatocellular carcinoma cell line) and ES-2 (a human ovarian cancer cell line). The in vivo anticancer effect of the total flavonoids was assessed in a mouse tumor model bearing H22-induced hepatocellular carcinoma, and cisplatin was used as a positive control.

RESULTS

The total flavonoids exerted a powerful inhibitory effect on the three cell lines, with 50% inhibiting concentrations (IC(50)) of 24.948, 31.569 and 6.923 μg/mL, respectively. In vivo studies showed that the total flavonoids had dose-dependent inhibitory effects on hepatocellular carcinoma in mice.

CONCLUSION

The total flavonoids from Xianhe Yanling Recipe have potential anticancer activity, and further researches and development are warranted.

A novel synthetic protoapigenone analogue, WYC02-9, induces DNA damage and apoptosis in DU145 prostate cancer cells through generation of reactive oxygen species

The protoapigenone analogue WYC02-9, a novel synthetic flavonoid, has been shown to act against a variety of experimental tumors. However, its effects on prostate cancer and its mechanism of action are unknown. Thus, WYC02-9 was investigated for its cytotoxicity against DU145 prostate cancer cells, as was the underlying mechanisms by which WYC02-9 might induce DNA damage and apoptotic cell death through reactive oxygen species (ROS). WYC02-9 inhibited the cell growth of three prostate cancer cell lines, especially DU145 cells. In DU145 cells, WYC02-9 increased the generation of intracellular ROS, followed by induction of DNA damage and activation of the ATM-p53-H2A.X pathway and checkpoint-related signals Chk1/Chk2, which led to increased numbers of cells in the S and G2/M phases of the cell cycle. Furthermore, WYC02-9 induced apoptotic cell death through mitochondrial membrane potential decrease and activation of caspase-9, caspase-3, and PARP. The above effects were all prevented by the ROS scavenger N-acetylcysteine. Administration of WYC02-9 in a nude mouse DU145 xenograft model further identified the anti-cancer activity of WYC02-9. These findings therefore suggest that WYC02-9-induced DNA damage and mitochondria-dependent cell apoptosis in DU145 cells are mediated via ROS generation.

Three 2-oxoglutarate-dependent dioxygenase activities of Equisetum arvense L. forming flavone and flavonol from (2S)-naringenin

Equisetum arvense L. (Equisetaceae-horsetail) accumulates various flavones and flavonols in infertile shoot. Enzyme assays conducted with crude extracts of the green tissue revealed chalcone synthase activity and also three further activities assigned to flavonoid biosynthesis and identified as flavone synthase I, flavanone 3β-hydroxylase and flavonol synthase. The latter three activities were characterized as soluble, 2-oxoglutarate-dependent dioxygenases by their typical cofactor requirements and peculiar inhibition. Notably, this is the first report of flavone synthase I which had been considered to be restricted solely to species of the Apiaceae from a distant plant taxon.

Apoptosis induced by a new flavonoid in human hepatoma HepG2 cells involves reactive oxygen species-mediated mitochondrial dysfunction and MAPK activation

Earlier reports suggest that protoapigenone showed remarkable anticancer activities. In the present study, the cytotoxic effect of a new flavonoid, 2-(cis-1, 2-dihydroxy 4-oxo-cyclohex-5-enyl)-5, 7-dihydroxy-chromone (DEDC), which is a protoapigenone analog, was investigated in human hepatoma HepG2 cells. We found that hepatoma cells were highly susceptible to DEDC in contrast with normal cells. The sustainable and rapid generation of reactive oxygen species was observed in DEDC-induced cell death. Following oxidative stress, DEDC sequentially decreased mitochondrial membrane potential (ΔΨm), reduced Bcl-2 expression, increased cytochrome c release, and activated caspase-3, -8, and -9. Phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen activated protein kinase (MAPK) was stimulated by treatment with DEDC. To further investigate the mechanisms of the DEDC-induced cell death, we examined the effects of reactive oxygen species scavenger N-acetyl-L-cysteine (NAC) and selective inhibitors for MAPK pathways on the cell death. The DEDC-induced cell death was significantly inhibited by both NAC and JNK inhibitor SP600125, but promoted by p38 MAPK inhibitor, SB203580. Together, DEDC may have antitumor effects in HepG2 cells through reactive oxygen species production as well as activation of MAPK signaling pathways.

New synthetic flavone derivatives induce apoptosis of hepatocarcinoma cells

Natural flavonoids have broad biological activity, including anticancer. In this study, a series of novel flavone derivatives were synthesized with the substitutions of chlorine, isopropyl, methoxy, and nitro groups on the benzene ring of flavone skeleton to develop effective anticancer agents. Antiproliferative assays showed that the synthesized chemicals possess notable activity against hepatocarcinoma cells (HepG-2); in particular, the compound 6f with chlorine and dimethoxy modifications at the two benzene rings showed an IC(50) at 1.1 microM to HepG-2. The 6f also displayed marked anticancer activity towards a panel of cancer cells, including nasopharyngeal carcinoma cells (CNE-2 and CNE-1), breast adenocarcinoma cell (MCF-7), and epithelial carcinoma cells (Hela). Exposing HepG-2 cells to compound 6f at 10 microM induced chromatin condensation, nuclear disassembly, and DNA fragmentation. In 6f-treated HepG-2 cells, the sub-G(0) population was remarkably increased; and in these cells, both caspase-8 and caspase-9 activity was significantly increased, which in turn activated caspase-3. In addition, proapoptotic Bax was upregulated by compound 6f while the antiapoptotic Bcl-2 was downregulated. Taken together, our data suggest that the new flavonoid derivative 6f triggers apoptosis through both death-receptor and mitochondria-dependent intrinsic pathways, being a potent therapeutic agent against hepatocarcinoma.

Fern plant-derived protoapigenone leads to DNA damage, apoptosis, and G(2)/m arrest in lung cancer cell line H1299

Protoapigenone, isolated from the native fern plant Thelypteris torresiana, has anticancer activity against some cancer cells. However, the toxicological mechanism for protoapigenone is still unknown. Here, we investigated the anticancer effect of protoapigenone on human lung cancer cell lines. The comet assay showed that DNA damage induced by protoapigenone is dose-dependent. Trypan blue exclusion showed that the cell killing by protoapigenone is both time and dose dependent. The IC(50) of protoapigenone for 12, 24, and 48 h in H1299 cells is 6.11, 2.74, and 1.49 microM, respectively. Flow cytometry showed cell cycle perturbation such as sub-G(1) accumulation (at 1.57 microM for 48 h and at 3.57 microM for 12 and 24 h) and G(2)/M arrest (at 3.57 microM for 12 and 24 h) for protoapigenone. The sub-G(1) accumulation phenomena in the 3.57 microM for 24 h sample were shown to be apoptosis using Annexin V-immunofluorescence/propidium iodide staining. These results suggest protoapigenone is a potential chemotherapeutic agent for lung cancers.