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.

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.

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.

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.

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.