1-oxoeudesm-11(13)-ene-12,8α-lactone-induced apoptosis via ROS generation and mitochondria activation in MCF-7 cells

Modulation of diverse oncogenic signaling pathways by oroxylin A: An important strategy for both cancer prevention and treatment

BACKGROUND

Regardless of major advances in diagnosis, prevention and treatment strategies, cancer is still a foreboding cause due to factors like chemoresistance, radioresistance, adverse side effects and cancer recurrence. Therefore, continuous development of unconventional approaches is a prerequisite to overcome foregoing glitches. Natural products have found their way into treatment of serious health conditions, including cancer since ancient times. The compound oroxylin A (OA) is one among those with enormous potential against different malignancies. It is a flavonoid obtained from the several plants such as Oroxylum indicum, Scutellaria baicalensis and S. lateriflora, Anchietea pyrifolia, and Aster himalaicus.

PURPOSE

The main purpose of this study is to comprehensively elucidate the anticancerous effects of OA against various malignancies and unravel their chemosensitization and radiosensitization potential. Pharmacokinetic and pharmacodynamic studies of OA have also been investigated.

METHOD

The literature on antineoplastic effects of OA was searched in PubMed and Scopus, including in vitro and in vivo studies and is summarized based on a systematic review protocol prepared according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The term "oroxylin A" was used in combination with "cancer" and all the title, abstracts and keywords appeared were considered.

RESULTS

In Scopus, a total of 157 articles appeared out of which 103 articles that did not meet the eligibility criteria were eliminated and 54 were critically evaluated. In PubMed, from the 85 results obtained, 26 articles were eliminated and 59 were included in the preparation of this review. Mounting number of studies have illustrated the anticancer effects of OA, and its mechanism of action.

CONCLUSION

OA is a promising natural flavonoid possessing wide range of pleiotropic properties and is a potential anticancer agent. It has a great potential in the treatment of multiple cancers including brain, breast, cervical, colon, esophageal, gall bladder, gastric, hematological, liver, lung, oral, ovarian, pancreatic and skin. However, lack of pharmacokinetic studies, toxicity assessments, and dose standardization studies and adverse effects limit the optimization of this compound as a therapeutic agent.

Aqueous Extract of Sea Squirt (Halocynthia roretzi) with Potent Activity against Human Cancer Cells Acts Synergistically with Doxorubicin

Marine ascidian is becoming one of the main sources of an antitumor drug that has shown high bioactivity and extensive application in cancer treatment. Halocynthia roretzi, an edible marine sea squirt, has been demonstrated to have various kinds of biological activities, such as anti-diabetic, anti-hypertension, and enhancing immunity. In this study, we reported that aqueous extracts from the edible parts of H. roretzi presented significantly inhibiting the efficiency on HepG-2 cell viability. The separate mixed compound exhibited strong effects of inhibitory proliferation and induced apoptosis via the generation of ROS along with the concurrent loss of mitochondrial membrane potential on tumor cells. Furthermore, we found that there existed a significantly synergistic effect of the ascidian-extracted compound mixture with the anti-cancer drug doxorubicin. In the presence of the extracts from H. roretzi, the dose of doxorubicin at the cellular level could be reduced by a half dose. The extracts were further divided by semipreparative-HPLC and the active ingredients were identified as a mixture of fatty amide, which was composed of hexadecanamide, stearamide, and erucamide by UHPLC-MS/MS. Our results suggest that the potential toxicity of ascidian H. roretzi in tumor cells, and the compounds extracted from H. roretzi could be potentially utilized on functional nutraceuticals or as an adjunct in combination with chemotherapy.

Trilobatin Induces Apoptosis and Attenuates Stemness Phenotype of Acquired Gefitinib Resistant Lung Cancer Cells via Suppression of NF-κB Pathway

Trilobatin is a common type of flavonoids compounds derived from Lithocarpus polystachyus Rehd leaves. Previous report suggests that trilobatin was potentially involved in pro-and anticancer, antioxidative and anti-hyperglycemic activities. Here, we investigated the anticancer efficiency of trilobatin on gefitinib resistant lung cancer cells. In this study, MTT assays, EdU incorporation assays, DAPI staining, tumor sphere formation assays, immunofluorescent staining and Western blot analysis were performed to explore the functional role of trilobatin on gefitinib resistant lung cancer cells. The results showed that trilobatin inhibits proliferation of gefitinib resistant lung cancer cells. In addition, the proportions of apoptotic cells were increased along with down-regulated expression levels of Bcl-2 and mitochondrial Cytochrome C while up-regulated Bax, Cleaved Caspase-3, -9, and cytosolic Cytochrome C expression. Moreover, trilobatin decreased tumor sphere formation and expression levels of multiple stemness markers (ALDH1, CD133, Nanog, and ABCG2) in gefitinib resistant lung cancer cells. Furthermore, investigation of the mechanism indicated that trilobatin suppressed activity of NF-κB via decreasing constitutive phosphorylation of NF-κB p65 and IκB-α in gefitinib resistant lung cancer cells. All these results indicate that trilobatin induces apoptosis and attenuates stemness phenotype of gefitinib resistant lung cancer cells, involved with, or partly, the suppression of NF-κB activity.

Ivalin Induces Mitochondria-Mediated Apoptosis Associated with the NF-κB Activation in Human Hepatocellular Carcinoma SMMC-7721 Cells

Ivalin, a natural compound isolated from Carpesium divaricatum, showed excellent microtubule depolymerization activities among human hepatocellular carcinoma in our previous work. Here, we investigated its functions on mitochondria-mediated apoptosis in hepatocellular carcinoma SMMC-7721 cells. DAPI (4′,6-diamidino-2-phenylindole) staining, annexin V-fluorexcein isothiocyanate (FITC) apoptosis detection, and western blotting were applied to explore the apoptotic effect of Ivalin. Next, the induction effect of Ivalin on the mitochondrial pathway was also confirmed via a series of phenomena including the damage of mitochondria membrane potential, mitochondria cytochrome c escape, cleaved caspase-3 induction, and the reactive oxygen species generation. In this connection, we understood that Ivalin induced apoptosis through the mitochondrial pathway and the overload of reactive oxygen species. Furthermore, we found that the activation of nuclear factor-κB (NF-κB) and subsequent p53 induction were associated with the apoptotic effect of Ivalin. These data confirmed that Ivalin might be a promising pro-apoptotic compound that can be utilized as a potential drug for clinical treatment.

Cyanidin-3-o-Glucoside Pharmacologically Inhibits Tumorigenesis via Estrogen Receptor β in Melanoma Mice

Expression patterns of estrogen receptors [ERα, ERβ, and G-protein associated ER (GPER)] in melanoma and skin may suggest their differential roles in carcinogenesis. Phytoestrogenic compound cyanidin-3-o-glucoside (C3G) has been shown to inhibit the growth and metastatic potential of melanoma, although the underlying molecular mechanism remains unclear. The aim of this study was to clarify the mechanism of action of C3G in melanoma in vitro and in vivo, as well as to characterize the functional expressions of ERs in melanoma. In normal skin or melanoma (n = 20/each), no ERα protein was detectable, whereas expression of ERβ was high in skin but weak focal or negative in melanoma; and finally high expression of GPER in all skin vs. 50% melanoma tissues (10/20) was found. These results correspond with our analysis of the melanoma survival rates (SRs) from Human Protein Atlas and The Cancer Genome Atlas GDC (362 patients), where low ERβ expression in melanoma correlate with a poor relapse-free survival, and no correlations were observed between SRs and ERα or GPER expression in melanoma. Furthermore, we demonstrated that C3G treatment arrested the cell cycle at the G2/M phase by targeting cyclin B1 (CCNB1) and promoted apoptosis via ERβ in both mouse and human melanoma cell lines, and inhibited melanoma cell growth in vivo. Our study suggested that C3G elicits an agonistic effect toward ERβ signaling enhancement, which may serve as a potential novel therapeutic and preventive approach for melanoma.

Strepantibins A-C: Hexokinase II Inhibitors from a Mud Dauber Wasp Associated Streptomyces sp

Two new p-terphenyls, strepantibins A and B (1 and 2), along with the first representative of a naturally occurring bisphenyltropone, strepantibin C (3), were characterized from a Streptomyces sp. associated with the larvae of the mud dauber wasp Sceliphron madraspatanum. Their structures were determined by high-resolution electrospray ionization mass spectrometry, NMR, and X-ray crystallography data interpretation. Strepantibins A-C inhibited hexokinase II (HK2) activity and displayed antiproliferative activity against hepatoma carcinoma cells HepG-2, SMMC-7721 and plc-prf-5. In SMMC-7721 cells treated with strepantibin A, the morphological characteristics of apoptosis were observed.

Cyanidin-3-o-glucoside directly binds to ERα36 and inhibits EGFR-positive triple-negative breast cancer

Anthocyanins have been shown to inhibit the growth and metastatic potential of breast cancer (BC) cells. However, the effects of individual anthocyanins on triple-negative breast cancer (TNBC) have not yet been studied. In this study, we found that cyanidin-3-o-glucoside (Cy-3-glu) preferentially promotes the apoptosis of TNBC cells, which co-express the estrogen receptor alpha 36 (ERα36) and the epidermal growth factor receptor (EGFR). We demonstrated that Cy-3-glu directly binds to the ligand-binding domain (LBD) of ERα36, inhibits EGFR/AKT signaling, and promotes EGFR degradation. We also confirmed the therapeutic efficacy of Cy-3-glu on TNBC in the xenograft mouse model. Our data indicates that Cy-3-glu could be a novel preventive/therapeutic agent against the TNBC co-expressed ERα36/EGFR.

3-Oxo-γ-costic acid fungal-transformation generates eudesmane sesquiterpenes with in vitro tumor-inhibitory activity

While select eudesmane sesquiterpenes exhibit anti-neoplastic activity, tumor-inhibition for costic-acids has not been established. Here biological activity of 3-oxo-γ-costic acid (1), previously isolated from Chiliadenus montanus, as well as new sesquiterpenes (2-5) and the known derivative, 3-oxoeudesma-1,4,11(13)-trien-7-1061αH-l2-oic acid (6), all produced from 1 by the fungus Athelia rolfsii, are reported. Structures were elucidated using MS and NMR spectroscopy with activity-screening utilizing human colon- and lung-tumor lines, Caco-2 and A549 respectively. Compound 1 exhibited anti-proliferative activity against Caco-2 (IC₅₀ 39µM) and 2 was active against A549 (IC₅₀ 74µM) suggesting therapeutic potential for the original substrate and a bio-transformed product.

5,6-Dihydroxy-3,7,4'-trimethoxyflavonol induces G2/M cell cycle arrest and apoptosis in human hepatocellular carcinoma cells

5,6-Dihydroxy-3,7,4'-trimethoxyflavonol (AH5), 5,6,3'-trihydroxy-3,7,4'-trimethoxyflavonol (AH22), artemetin, and oroxylin A are four flavonoids with the same 2-phenyl-chromone skeleton isolated from the Chinese herb Aster himalaicus. The aim of this study was to evaluate the structure-activity relationship of these four analogs and the mediation of AH5 cytotoxicity via G2/M arrest and apoptosis in human hepatocellular carcinoma (HCC) cells. 3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated AH5 showed the better potency to inhibit proliferation in human HCC cells, which suggested hydroxyl binding to C6 is necessary to anticancer properties, whereas binding to C3' attenuated the activities and increased toxicity in tested cells. Flow cytometry analysis revealed that AH5-induced G2/M arrest and significantly apoptosis in these cell lines. HepG-2 cells were used to further evaluate the antitumor effects and mechanisms of AH5. AH5-induced apoptosis was further confirmed by 4',6-diamidino-2-phenylindole (DAPI) staining and the increased ratio of Bax/Bcl-2. Moreover, AH5 induced the release of cytochrome C and the activation of caspase-9 and caspase-3, thus suggesting mitochondria activation might be involved. Western blot showed that AH5 induced the phosphorylation of Cdc2 and decreased the level of Cyclin B1. These results demonstrated that AH5 could be a proapoptotic leading compound for developing novel anticancer drugs.

Eudesmane-type sesquiterpene derivatives from Laggera alata

Ten eudesmane-type sesquiterpene derivatives (1-10), including six cuauhtemone derivatives (1-6), one di-norsesquiterpene (3-oxo-di-nor-eudesma-4-en-11-oic acid, 7), and three eudesmane glycosides (alatoside F-H, 8-10) were isolated from the whole plants of Laggera alata together with 12 known compounds. Their structures were elucidated on the basis of extensive spectroscopic analysis, acid hydrolysis, and compounds 1 and 7 were studied by single-crystal X-ray diffraction analysis. The absolute configuration of 1 was determined by the application of the modified Mosher's method. All of the isolated eudesmane-type sesquiterpenes were evaluated for their cytotoxic activities on six human cancer cell lines, but all of the compounds were inactive on the tested cell lines in the concentration of 100 μg/mL.

NF-κB activation was involved in reactive oxygen species-mediated apoptosis and autophagy in 1-oxoeudesm-11(13)-eno-12,8α-lactone-treated human lung cancer cells

1-oxoeudesm-11(13)-eno-12,8α-lactone (OEL), a novel eudesmane-type sesquiterpene compound, has been shown to inhibit the growth of some cancer cell lines and induce significant apoptosis. Here, we investigated the anti-cancer activities of OEL in human lung cancer cells. Our studies demonstrated that OEL induced both apoptosis and autophagy in A549 and H460 cells. OEL-induced autophagy was assessed by appearance of autophagic vacuoles, formation of acidic vesicular organelles, conversion of LC3-I to LC3-II, recruitment of LC3-II to the autophagosomes, and activation of autophagy genes. Furthermore, administration of autophagic inhibitor 3-methyladenine augments OEL-induced apoptotic cell death. The induction of autophagy and apoptosis by OEL links to NF-κB activation and the generation of reactive oxygen species (ROS). Interruption of NF-κB activation by specific inhibitor promotes apoptosis, but decreases autophagy. ROS antioxidants (N-acetylcysteine) attenuated both OEL-induced autophagy and apoptosis. Further experiments confirmed that OEL-induced activation of ROS was increased by NF-κB inhibitor whereas NF-κB activation was not affected by ROS inhibition. These findings suggest that OEL-elicited autophagic response plays a protective role that impedes cell death, and inhibition of autophagy could be an adjunctive strategy for enhancing the chemotherapeutic effect of OEL as an antitumor agent.

A new cembrane glycoside in Asterothamnus centrali-asiaticus from Gobi Desert

A new cembrane glycoside, nephthenol 15-O-β-d-quinovoside, was isolated from the aerial parts of Asterothamnus centrali-asiaticus. Its structure was elucidated by 1D and 2D NMR spectroscopic analysis, as well as by mass spectrometry. This is the first report of the occurrence of a cembrane glycoside in vascular plants.

Sesquiterpenoids from Carpesium divaricatum and their cytotoxic activity

In the course of searching for cytotoxic terpenoids from medicinal plants in China, two new eudesmane sesquiterpenoids, 5α-hydroxy-13-methoxy-7αH,11αH-eudesm-4(15)-en-12,8β-lactone (1) and 1β-hydroxy-7αH,11αH-eudesm-4(15)-en-12,8β-lactone (2), along with fourteen known sesquiterpenoids were isolated from the whole plant of Carpesium divaricatum. The structures of new compounds were determined using spectroscopic methods, including IR, HRESIMS, and 1D and 2D NMR spectroscopy. The cytotoxicity of selected sesquiterpene lactones against human oral epidermoid carcinoma (KB), human breast cancer (MCF-7) and human hepatoma (HepG-2) cells was also evaluated by MTT method.

Ehrlichia type IV secretion effector ECH0825 is translocated to mitochondria and curbs ROS and apoptosis by upregulating host MnSOD

Ehrlichia chaffeensis infects monocytes/macrophages and causes human monocytic ehrlichiosis. To determine the role of type IV secretion (T4S) system in infection, candidates for T4S effectors were identified by bacterial two-hybrid screening of E. chaffeensis hypothetical proteins with positively charged C-terminus using E. chaffeensis VirD4 as bait. Of three potential T4S effectors, ECH0825 was highly upregulated early during exponential growth in a human monocytic cell line. ECH0825 was translocated from the bacterium into the host-cell cytoplasm and localized to mitochondria. Delivery of anti-ECH0825 into infected host cells significantly reduced bacterial infection. Ectopically expressed ECH0825 also localized to mitochondria and inhibited apoptosis of transfected cells in response to etoposide treatment. In double transformed yeast, ECH0825 localized to mitochondria and inhibited human Bax-induced apoptosis. Mitochondrial manganese superoxide dismutase (MnSOD) was increased over ninefold in E. chaffeensis-infected cells, and the amount of reactive oxygen species (ROS) in infected cells was significantly lower than that in uninfected cells. Similarly, MnSOD was upregulated and the ROS level was reduced in ECH0825-transfected cells. These data suggest that, by upregulating MnSOD, ECH0825 prevents ROS-induced cellular damage and apoptosis to allow intracellular infection. This is the first example of host ROS levels linked to a bacterial T4S effector.