Therapeutic Potential of (-)-Agelamide D, a Diterpene Alkaloid from the Marine Sponge Agelas sp., as a Natural Radiosensitizer in Hepatocellular Carcinoma Models.

Radiation therapy (RT) is an effective local treatment for unresectable hepatocellular carcinoma (HCC), but there are currently no predictive biomarkers to guide treatment decision for RT or adjuvant systemic drugs to be combined with RT for HCC patients. Previously, we reported that extracts of the marine sponge Agelas sp. may contain a natural radiosensitizer for HCC treatment. In this study, we isolated (-)-agelamide D from Agelas extract and investigated the mechanism underlying its radiosensitization. (-)-Agelamide D enhanced radiation sensitivity of Hep3B cells with decreased clonogenic survival and increased apoptotic cell death. Furthermore, (-)-agelamide D increased the expression of protein kinase RNA-like endoplasmic reticulum kinase/inositol-requiring enzyme 1α/activating transcription factor 4 (PERK/eIF2α/ATF4), a key pathway of the unfolded protein response (UPR) in multiple HCC cell lines, and augmented radiation-induced UPR signaling. In vivo xenograft experiments confirmed that (-)-agelamide D enhanced tumor growth inhibition by radiation without systemic toxicity. Immunohistochemistry results showed that (-)-agelamide D further increased radiation-induced ATF4 expression and apoptotic cell death, which was consistent with our in vitro finding. Collectively, our results provide preclinical evidence that the use of UPR inducers such as (-)-agelamide D may enhance the efficacy of RT in HCC management.

Enzymatic transformation and anti-tumor activity of Sargassum horneri fucoidan.

Structure of the fucoidan from Sargassum horneri and products of its enzymatic transformation with molecular weight over 20 kDa were investigated. Fucoidan was hydrolyzed by recombinant fucoidanase FFA1 and its fraction of higher molecular weight was fractionated using anion-exchange chromatography, resulting in three sulphated polysaccharides of various molecular weight (63-138 kDa). Their structures were analyzed using NMR spectroscopy, showing the fucoidan (ShF) to be a branched polysaccharide with the backbone consisting of the repeating →3-α-l-Fucp(2SO3-)-1→4-α-l-Fucp(2,3SO3-)-1→ fragment and side chains including the α-l-Fucp-1→2-α-l-Fucp-1→ or α-l-Fucp-1→3-α-l-Fucp(4SO3-)-1→ fragments attached to the main chain at C4. The fragment F3 differing by molecular weight and side chain from other fucoidans fragments possessed the most significant anticancer and radiosensitizing activities.

Structures and Bioactivities of Quadrangularisosides A, A1, B, B1, B2, C, C1, D, D1-D4, and E from the Sea Cucumber Colochirus quadrangularis: The First Discovery of the Glycosides, Sulfated by C-4 of the Terminal 3-O-Methylglucose Residue. Synergetic Effect on Colony Formation of Tumor HT-29 Cells of these Glycosides with Radioactive Irradiation.

Thirteen new mono-, di-, and trisulfated triterpene glycosides, quadrangularisosides A-D4 (1-13) have been isolated from the sea cucumber Colochirus quadrangularis, which was collected in Vietnamese waters. The structures of these glycosides were established by 2D NMR spectroscopy and HR-ESI (High Resolution Electrospray Ionization) mass spectrometry. The novel carbohydrate moieties of quadrangularisosides D-D4 (8-12), belonging to the group D, and quadrangularisoside E (13) contain three sulfate groups, with one of them occupying an unusual position-at C(4) of terminal 3-O-methylglucose residue. Quadrangularisosides A (1) and D3 (11) as well as quadrangularisosides A1 (2) and D4 (12) are characterized by the new aglycones having 25-hydroperoxyl or 24-hydroperoxyl groups in their side chains, respectively. The cytotoxic activities of compounds 1-13 against mouse neuroblastoma Neuro 2a, normal epithelial JB-6 cells, erythrocytes, and human colorectal adenocarcinoma HT-29 cells were studied. All the compounds were rather strong hemolytics. The structural features that most affect the bioactivity of the glycosides are the presence of hydroperoxy groups in the side chains and the quantity of sulfate groups. The membranolytic activity of monosulfated quadrangularisosides of group A (1, 2) against Neuro 2a, JB-6 cells, and erythrocytes was relatively weak due to the availability of the hydroperoxyl group, whereas trisulfated quadrangularisosides D3 (11) and D4 (12) with the same aglycones as 1, 2 were the least active compounds in the series due to the combination of these two structural peculiarities. The erythrocytes were more sensitive to the action of the glycosides than Neuro 2a or JB-6 cells, but the structure-activity relationships observed for glycosides 1-13 were similar in the three cell lines investigated. The compounds 3-5, 8, and 9 effectively suppressed the cell viability of HT-29 cells. Quadrangularisosides A1 (2), C (6), C1 (7), and E (13) possessed strong inhibitory activity on colony formation in HT-29 cells. Due to the synergic effects of these glycosides (0.02 µM) and radioactive irradiation (1 Gy), a decreasing of number of colonies was detected. Glycosides 1, 3, and 9 enhanced the effect of radiation by about 30%.

In Vitro Anticancer and Radiosensitizing Activities of Phlorethols from the Brown Alga Costaria costata.

The anticancer and radiosensitizing effects of high-molecular-weight phlorethols CcPh (Mw = 2520 Da) isolated from the brown algae of Costaria costata on human colorectal carcinoma HCT 116 and HT-29 cells were investigated. Phlorethols CcPh possessed cytotoxic activity against HT-29 (IC50 = 92 µg/mL) and HCT 116 (IC50 = 94 µg/mL) cells. CcPh at non-toxic concentrations inhibited the colony formation in colon cancer cells and significantly enhanced their sensitivity to low non-toxic X-ray irradiation. The combinatory effect of radiation and CcPh was synergistic (Combination index < 0.7). Algal phlorethols might be prospective candidates as radiosensitizers to improve the scheme of radiotherapy.

Effects of Polar Steroids from the Starfish Patiria (=Asterina) pectinifera in Combination with X-Ray Radiation on Colony Formation and Apoptosis Induction of Human Colorectal Carcinoma Cells.

Despite significant advances in the understanding, prevention, and treatment of cancer, the disease continues to affect millions of people worldwide. Chemoradiation therapy is a rational approach that has already proven beneficial for several malignancies. However, the existence of toxicity to normal tissue is a serious limitation of this treatment modality. The aim of the present study is to investigate the ability of polar steroids from starfish Patiria (=Asterina) pectinifera to enhance the efficacy of radiation therapy in colorectal carcinoma cells. The cytotoxic activity of polar steroids and X-ray radiation against DLD-1, HCT 116, and HT-29 cells was determined by an MTS assay. The effect of compounds, X-ray, and their combination on colony formation was studied using the soft agar method. The molecular mechanism of the radiosensitizing activity of asterosaponin P1 was elucidated by western blotting and the DNA comet assay. Polar steroids inhibited colony formation in the tested cells, and to a greater extent in HT-29 cells. Asterosaponin P1 enhanced the efficacy of radiation and, as a result, reduced the number and size of the colonies of colorectal cancer cells. The radiosensitizing activity of asterosaponin P1 was realized by apoptosis induction through the regulation of anti- and pro-apoptotic protein expression followed by caspase activation and DNA degradation.

Radiosensitizing effect of the fucoidan from brown alga Fucus evanescens and its derivative in human cancer cells.

Fucoidan from brown alga Fucus evanescens and its product of enzymatic hydrolysis have precisely established structure and possess significant biological activities. The aim of present study was to determine radiosensitizing activity of fucoidan from brown alga F. evanescens and its derivative in human melanoma, breast adenocarcinoma, and colorectal carcinoma cell lines and elucidate mechanism of their action. The fucoidan from F. evanescens and its derivative had a comparable radiosensitizing activity and increased the inhibiting effect of X-ray radiation on proliferation and colony formation of human cancer cells, with significant inhibition of melanoma cells. The molecular mechanism of this action was associated with the induction of apoptosis by activating the initiator and effector caspases, suppressing the expression of the anti-apoptotic protein, and enhancing the fragmentation of DNA. The obtained data confirm the prospects of using fucoidan's derivative in combination with radiation therapy for the improvement of the schemes of cancer therapy.

Stem cell enriched-epithelial spheroid cultures for rapidly assaying small intestinal radioprotectors and radiosensitizers in vitro.

Radiation therapy is one of the main treatment options for many cancer patients. Although high doses of radiation may maximize tumor cell killing, dose escalation is limited by toxicity to neighboring normal tissues. This limitation applies particularly to the small intestine, the second most radiosensitive organ in the body. Identifying small intestinal (SI) radioprotectors could enable dose escalation in the treatment of abdominopelvic malignancies. However, the only assay currently available to identify effects of radiomodulating drugs on the regenerating capacity of SI stem cells is the Withers-Elkind microcolony assay, which requires large numbers of mice, making it a costly and low throughput method. Here, we describe a novel spheroid formation assay (SFA) that utilizes SI stem cell-enriched three-dimensional epithelial spheroid cultures to identify gastrointestinal radiomodulators ex vivo. The SFA is scalable for high throughput screening and can be used to identify both radioprotectors and radiosensitizers.

Ginseng polysaccharide serves as a potential radiosensitizer through inducing apoptosis and autophagy in the treatment of osteosarcoma.

Recent studies have confirmed that the combined use of anti-cancer drugs with ionizing radiation (IR) could improve the sensitivity of osteosarcoma (OS) cells. Therefore, it is necessary to identify potential effective drugs for the enhancement of IR-radiosensitivity. In the current study, we found that 20, 10, 5, and 1 µM of ginseng polysaccharide (GPS) significantly suppressed MG-63 cell viability with or without γ-ray radiation in a dose- and time-dependent manner. Strikingly, 20 µM of GPS combined with 5 Gy treatment suppressed colony formation capacity by nearly 13.75∼fold compared with IR treatment alone. Our results showed that GPS could markedly induce early apoptosis and autophagy in MG-63 cells. A higher drug concentration and a greater exposure dose were directly associated with more apoptosis and autophagy in cells. Western blot analysis showed that GPS decreased the phosphorylation of p38 and AKT as well as the protein expression of Bax and cleaved-caspase3. In summary, GPS inhibited proliferation and increased apoptosis and autophagic death in OS cells, indicating that GPS may be a potential effective auxiliary drug for improving the IR sensitivity of OS patients.

Tanshinone IIA sensitizes oral squamous cell carcinoma to radiation due to an enhanced autophagy.

PURPOSE: Tanshinone IIA (TanIIA), which is derived from the roots of Salvia miltiorrhiza (Danshen), has multiple pharmacological activities. However, the radiosensitivezing activity of TanIIA in oral cancer cells has not been studied extensively. The purpose of this study is to investigate the radiosensitizing effects of TanIIA in human oral squamous cell carcinoma SCC090 and examined the underlying mechanisms. METHODS: Clonogenic assay was used to investigate the radiosensitizing effect of TanIIA on SCC090. And then, apoptosis and reactive oxygen species (ROS) induced by the combination of TanIIA with radiation were analyzed by Flow cytometry. Finally, autophagy was detected by monodansylcadervarine (MDC) staining. RESULTS: TanIIA could significantly sensitize SCC090 to radiation. Meanwhile, an increase ROS generation after exposed to the combination treatment was found. In addition, the protein levels of Beclin 1, Atg5 and LC3-II, three important proteins involved in autophagy were increased in cells. CONCLUSIONS: TanIIA exerted a strong radiosensitizing effect on SCC090 comparing with the simple drug or single radiation treatment, which was due to an enhanced ROS generation and autophagy.

Targeting DDX3 with a small molecule inhibitor for lung cancer therapy.

Lung cancer is the most common malignancy worldwide and is a focus for developing targeted therapies due to its refractory nature to current treatment. We identified a RNA helicase, DDX3, which is overexpressed in many cancer types including lung cancer and is associated with lower survival in lung cancer patients. We designed a first-in-class small molecule inhibitor, RK-33, which binds to DDX3 and abrogates its activity. Inhibition of DDX3 by RK-33 caused G1 cell cycle arrest, induced apoptosis, and promoted radiation sensitization in DDX3-overexpressing cells. Importantly, RK-33 in combination with radiation induced tumor regression in multiple mouse models of lung cancer. Mechanistically, loss of DDX3 function either by shRNA or by RK-33 impaired Wnt signaling through disruption of the DDX3-ß-catenin axis and inhibited non-homologous end joining-the major DNA repair pathway in mammalian somatic cells. Overall, inhibition of DDX3 by RK-33 promotes tumor regression, thus providing a compelling argument to develop DDX3 inhibitors for lung cancer therapy.

Anti-tumor effects of various furocoumarins isolated from the roots, seeds and fruits of Angelica and Cnidium species under ultraviolet A irradiation.

We examined the effects on cell proliferation of 10 methoxyfurocoumarins and 7 dihydrofurocumarins isolated from Umbelliferae medicinal plants, and their mechanisms of action against B16F10 melanoma cells or in melanin-possessing hairless mice implanted with B16F10 melanoma cells, under UVA irradiation. Furocoumarins having a methoxy group, such as bergapten (1), xanthotoxin (2), phellopterin (4), byakangelicin (6), neobyakangelicin (8), isobergapten (9) and sphondin (10), showed anti-proliferative activity and caused G2/M arrest at concentrations of 0.05-15.0 µM. The 7 dihydrofurocoumarins had no effect. UVA plus 1, 2, 4, 6 and sec-O-acetylbyakagelicin (7), having one methoxy group at the C-5 position and a linear-type conformation, reduced tumor growth and final tumor weight in B16F10-bearing mice at 0.5 or 1.0 mg/kg (intraperitoneal injection). UVA plus 1 and 2 increased Chk1 phosphorylation and decreased cdc2 (Thr 161) phosphorylation in the melanoma cells. The anti-tumor actions of UVA plus furocoumarins having a methoxy group might be due to the arrest of the cell cycle at G2/M through an increase in phospho-Chk1 and reduction in phospho-cdc2.

Isolation of substances with antiproliferative and apoptosis-inducing activities against leukemia cells from the leaves of Zanthoxylum ailanthoides Sieb. & Zucc.

Extraction of the leaves of Zanthoxylum ailanthoides Sieb. & Zucc. affords extracts and four isolated compounds which exhibit activities against leukemia cells. The chloroform-soluble fraction (ZAC) of the crude extract of this plant showed cytotoxic activity against human promyelocytic leukemia (HL-60) and myelomonocytic leukemia (WEHI-3) cells with IC(50) values of 73.06 and 42.22 µg/mL, respectively. The active ZAC was further separated to yield pheophorbide-a methyl ester (1), pheophorbide-b methyl ester (2), 13(2)-hydroxyl (13(2)-S) pheophorbide-a methyl ester (3) and 13(2)-hydroxyl (13(2)-R) pheophorbide-b methyl ester (4) whose structures were confirmed by spectroscopic methods. Compounds 2-4 showed cytotoxic activities against both leukemia cells with IC(50) value in the range of 46.76-79.43 nM, whereas compound 1 exhibited only weak cytotoxic activity. The extracts and compounds 1-4 also induced apoptosis and DNA damage in leukemia cells after treatment. The results suggested that the Z. ailanthoides is biologically active against leukemia cells.

Photo-activated pheophorbide-a, an active component of Scutellaria barbata, enhances apoptosis via the suppression of ERK-mediated autophagy in the estrogen receptor-negative human breast adenocarcinoma cells MDA-MB-231.

AIM OF THE STUDY: Scutellaria barbata is a traditional Chinese medicine for cancer treatments. Pheophorbide-a (Pa), one of the active components isolated from this herbal medicine has been proposed to be a potential natural photosensitizer for photodynamic therapy. The anti-tumor effect of pheophorbide-a based photodynamic therapy (Pa-PDT) has been successfully demonstrated in a wide range of human malignant cell lines. However, the effectiveness of Pa-PDT has not yet been evaluated on human breast cancer, which is documented as the second common and the fifth most lethal cancer worldwide. MATERIALS AND METHODS: The cytotoxicity of Pa-PDT was evaluated by using an estrogen receptor (ER)-negative human breast adenocarcinoma cell line MDA-MB-231. The involvement of mitochondria was revealed by the change of mitochondrial membrane potential and the increase of intracellular reactive oxygen species (ROS). The hallmarks of apoptosis, ER stress and autophagy were also assessed by DNA fragmentation, Western blotting, and immunostaining assays. RESULTS: Pa-PDT showed inhibitory effect on the growth of MDA-MB-231 cells with an IC(50) value of 0.5 microM at 24h. Mitogen-activated protein kinase (MAPK) pathway was found to be triggered, where activation of c-Jun N-terminal kinase (JNK) and inhibition of extracellular signal-regulated kinase (ERK) were occurred in the Pa-PDT-treated cells. Our findings suggested that Pa-PDT exhibited its anti-tumor effects by the activation of mitochondria-mediated apoptosis and the ERK-mediated autophagy in MDA-MB-231 cells. CONCLUSION: The present study suggested Pa-PDT is a potential protocol for the late phase human breast cancer, and it is the first study to demonstrate the Pa-PDT induced autophagy contributed to the anti-tumor effects of Pa-PDT on human cancer cells.

Efficient preparation of highly pure chlorin e6 and its photodynamic anti-cancer activity in a rat tumor model.

Photodynamic therapy (PDT) is currently being used as an alternative therapeutic modality for a variety of malignant tumors. This study was performed to show an efficient preparation of second generation of photosensitizer chlorin e6 (Ce6) with high yield and purity, and to test antitumor activity of Ce6-induced PDT (Ce6-PDT) both in vitro and in vivo using a rat tumor model. Three-week-old male Sprague-Dawley (SD) rats were inoculated s.c. on the right flank with 5x10(6) RK3E-ras cells. The animals were administered i.v. with Ce6 (10 mg/kg) and 24 h later, PDT was performed using a laser diode at a light dose of 100 J/cm2. Ce6-PDT generated reactive oxygen species and led to significant growth inhibition in RK3E-ras cell. In addition, Ce6-PDT induced apoptosis through the activation of caspase-3 and its downstream target, PARP cleavage. The protein level of anti-apoptotic bcl-2 was also reduced by Ce6-PDT in RK3E-ras cells. In in vivo experiments, application of Ce6-PDT led to a significant reduction of tumor size. PCNA immunostaining and TUNEL assay revealed that Ce6-PDT inhibited tumor cell proliferation and increased apoptosis. These findings suggest that the newly purified Ce6-PDT can effectively arrest tumor growth by inhibiting cell proliferation and inducing apoptosis.

Isolation and identification of impurities in chlorin e6.

The tetrapyrrolic compound chlorin e6 is currently used as a pharmaceutical substance for Photolon formulation, which is utilized in photodynamic therapy of various diseases. It was found that chlorin e6 could contain both process- and degradation-related impurities. In order to understand their origin, the most abundant impurities were prepared by liquid extraction, preparative chromatography or chemical synthesis. By means of HPLC-PDA-MS, 1D and 2D NMR spectroscopy, these impurities were identified as chlorin e6 17(4)-ethyl ester, chlorin e4, 15-hydroxyphyllochlorin, rhodochlorin, 15(1)-hydroxymethylrhodochlorin delta-lactone, rhodochlorin-15-oxymethyl delta-lactone, rhodochlorin-15-oxymethyl delta-lactone 17(4)-ethyl ester, 15(1)-hydroxymethylrhodoporphyrin delta-lactone, rhodoporphyrin-15-oxymethyl delta-lactone and purpurin 18. The possible routes of formation of the chlorin derivatives upon the production and storage of chlorin e6 are discussed.

Enhancement of radiation effect by Aphanamixis polystachya in mice transplanted with Ehrlich ascites carcinoma.

The effect of radiation on tumor tissue can be optimized by adding radiosensitizing agents, in order to achieve a greater degree of tumor damage than expected from the use of either treatment alone. The ethanolic extract of Aphanamixis polystachya (APE) was tested in Swiss albino mice transplanted with Ehrlich ascites carcinoma (EAC) and exposed to various doses of gamma-radiation. EAC mice received 0, 10, 25, 50, 75, 100, 150 or 200 mg/kg body wt APE before exposure to 6 Gy gamma-radiation followed by once daily administration for another 8 consecutive days post-irradiation. The optimum radiosensitizing dose was found to be 50 mg/kg APE that was further tested in EAC mice exposed to 0, 1, 2, 4, 6 or 8 Gy hemi body gamma-radiation. The best effect of APE and radiation was observed for 6 Gy gamma-radiation. The splitting of 50 mg into two equal fractions of 25 mg and administering the split dose with a gap of 8 h on 1, 3, 5, 7 or 9 d of tumor inoculation resulted in an increased survival even when the drug was administered at late stages (day 5) of tumor development. The APE treatment before irradiation elevated lipid peroxidation followed by a reduction in the glutathione contents. Treatment of tumor bearing mice with APE before irradiation further reduced the activities of various antioxidant enzymes like glutathione peroxidase, glutathione-s-transferase, superoxide dismutase and catalase at different post last drug administration (PLDA) times.

Enhancement of radiation-induced apoptosis by Podophyllum hexandrum.

The aqueous extract of Podophyllum hexandrum (RP-1), which has been recently reported to manifest radioprotective and anti-tumour properties, has been investigated for its mode of action. RP-1, under in-vitro conditions dose-dependently chelated metal ions, inhibited radiation or metal ion-induced hydroxyl radicals and lipid peroxidation and scavenged superoxide anions. Intraperitoneal administration of RP-1 to mice pre-irradiation (10 Gy) induced more DNA fragmentation and lipid peroxidation in thymocytes maximally at 4 and 8 h, respectively, in comparison with RP-1 treatment or irradiation. Flow-cytometric quantification of sub-diploid peak, oligonucleosomal cleavage assay (ladder) and depletion of total thiols also corroborated the ability of RP-1 to enhance radiation-induced apoptosis. RP-1 in presence of 100 microM CuSO(4) induced strand breaks in plasmid DNA and addition of metal chelators (EDTA and deferoxamine) inhibited the strand scission. Treatment with a major constituent of RP-1, podophyllin, did not cause strand breaks, but isolated constituents of RP-1, quercetin or podophyllotoxin, induced strand breaks. Depending on its concentration in the milieu, RP-1 acted as a pro- or antioxidant modifying the radiation-induced apoptosis and therefore could be exploited for cancer management.

High-throughput assay for G2 checkpoint inhibitors and identification of the structurally novel compound isogranulatimide.

Treatment of cancer cells lacking p53 function with G2 checkpoint inhibitors sensitizes them to the toxic effects of DNA damage and has been proposed as a strategy for cancer therapy. However, few inhibitors are known, and they have been found serendipitously. We report the development of a G2 checkpoint inhibition assay that is suitable for high-throughput screening and its application to a screen of 1300 natural extracts. We present the isolation of a new G2 checkpoint inhibitor, the structurally novel compound isogranulatimide. In combination with gamma-irradiation, isogranulatimide selectively kills MCF-7 cells lacking p53 function.

Withania somnifera Dunal (Ashwagandha): potential plant source of a promising drug for cancer chemotherapy and radiosensitization.

Study of antitumor and radiosensitizing properties of W. somnifera (Ashwagandha), a well known medicinal plant, have yielded encouraging results. The alcoholic extract of the dried roots of the plant as well as the active component withaferin A isolated from the extract showed significant antitumor and radiosensitizing effects in experimental tumors in vivo, without any noticeable systemic toxicity. Withaferin A gave a sensitizer enhancement ratio of 1.5 for in vitro cell killing of V79 Chinese hamster cells at a non toxic concentration of approximately 2 microM. The mechanism of action of this compound is not known. The studies so far indicate that W. somnifera could prove to be a good natural source of a potent and relatively safe radiosensitizer/chemotherapeutic agent. Further studies are needed to explore the clinical potential of this plant for cancer therapy.