Low dose Emodin induces tumor senescence for boosting breast cancer chemotherapy via silencing NRARP.

PURPOSE: The resistance to 5-FU often limits its clinical effectiveness on breast cancer treatment. Combination therapy thus is employed to overcome this treatment resistance. We here report a potent antitumor effect of Emodin at low dose on chemotherapy sensitivity of MCF-7 breast cancer cells. METHODS: Cell viability, apoptosis, glutathiones (GSH) concentration and Reactive oxygen species (ROS) activity following Emodin and 5-FU treatment was assessed. Cellular senescence following combined treatment and silence of NRARP was examined by senescence-associated ß-galactosidase analysis. Western blot analysis was used to determine changes in the expression of p21, p16, p27, E2F1 and NRARP. RESULTS: Low dose Emodin potentiates 5-FU-induced apoptosis of breast cancer cells, in association with inhibition of NRARP, resulting in cellular senescence. RNA interference of NRARP induced cellular senescence in MCF-7 breast cancer cells. Furthermore, the cellular senescence induced by Emodin and 5-FU treatment could be reverted by pcDNA-NRARP. CONCLUSION: These findings provide preclinical evidence for repurposing use of Emodin in combination with chemotherapeutic agents to treat breast cancer as an alternative salvage regimen.

Tanshinone IIA enhances bystander cell killing of cancer cells expressing Drosophila melanogaster deoxyribonucleoside kinase in nuclei and mitochondria.

Heterologous expression of the Drosophila melanogaster multi-substrate deoxyribonucleoside kinase (Dm-dNK) increases the sensitivity of cancer cells to several cytotoxic nucleoside analogs. Thus, it may be used as a suicide gene in combined gene/chemotherapy treatment of cancer. To further characterize this potential suicide gene, we constructed two retroviral vectors that enabled the expression of Dm-dNK in cancer cells. One vector harbored the wild­type enzyme that localized to the nucleus. The other vector harbored a mitochondrial localized mutant enzyme that was constructed by deleting the nuclear localization signal and fusing it to a mitochondrial import signal of cytochrome c oxidase. A thymidine kinase-deficient osteosarcoma cell line was transduced with the recombinant viruses. The sensitivity and bystander cell killing in the presence of pyrimidine nucleoside analogs (E)-5-(2-bromovinyl)­2'­deoxyuridine and 1-ß-D-arabinofuranosylthymine were investigated. Tanshinone IIA is a constituent of Danshen; a traditional Chinese medicine used in the treatment of cardiovascular diseases. This study also looked at the influence of Tanshinone IIA on the bystander effect and the underlying mechanisms. We showed that sensitivity of the osteosarcoma cell line to the nucleoside analogs and the efficiency of bystander cell killing were independent of the subcellular localization of Dm-dNK. The enhanced effect of tanshinone IIA on the bystander effect was related to the increased expression of Cx43 and Cx26.

Synergistic antitumor effect of adenovirus armed with Drosophila melanogaster deoxyribonucleoside kinase and nucleoside analogs for human breast carcinoma in vitro and in vivo.

BACKGROUND: Suicide gene therapy in cancer can selectively kill tumors without damaging normal tissues. Drosophila melanogaster multisubstrate deoxyribonucleoside kinase (Dm-dNK), an original suicide kinase, makes use of the carcinomatous suicide gene therapy for broader substrate specificity and a higher catalytic rate. METHODS: To enhance the anti-tumor efficacy of Dm-dNK and maintain its substrate specificity and safety control in the meantime, the conditionally replicative gene-viral system, ZD55-dNK (which contains the selective replication adenovirus, ZD55, encoded with Dm-dNK), was investigated in pushing a deeper development of this strategy. Selective replication, cell killing efficacy, and cytotoxicity, in combination with chemotherapy, were applied to two breast cell lines (MDA231 and MCF7 cells), two normal cell lines (WI38 and MRC5 cells), and the MCF7 xenograft model in vivo. RESULTS: The preclinical study showed that ZD55-dNK, combined with 2',2'-difluorodeoxycytidine (DFDC), synergistically inhibited adenovirus replication in vitro but maintained specifically cancer cell killing efficacy. ZD55-dNK also greatly improved the antineoplastic effect in vitro and in breast cancer xenograft in vivo. CONCLUSION: The concomitant use of ZD55-dNK and DFDC is possibly a novel and promising approach to breast cancer treatment, and further investigation on the safe control of excessive virus replication and the efficacy of this approach in humans is warranted.

Emodin induces apoptosis of human breast cancer cells by modulating the expression of apoptosis-related genes.

The aim of this study was to investigate the effects of emodin on the proliferation of human breast cancer cells Bcap-37 and ZR-75-30. Cell viability following emodin treatment was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The effects of emodin on apoptosis were determined by flow cytometry using Annexin V-fluorescein isothiocyanate and propidium iodide staining. Quantitative polymerase chain reaction and western blot analysis were used to determine changes in the expression of apoptotic genes and protein, respectively. The effect of emodin on the invasiveness of breast cancer cells was evaluated by Matrigel invasion assay. Treatment of breast cancer cells Bcap-37 and ZR-75-30 with emodin was observed to inhibit the growth and induced apoptosis in a time- and dose-dependent manner. Emodin reduced the level of Bcl-2 and increased levels of cleaved caspase-3, PARP, p53 and Bax. These findings indicate that emodin induces growth inhibition and apoptosis in human breast cancer cells. Emodin may be a potential therapeutic agent for the treatment of breast cancer.

Predictive value of phosphorylated mammalian target of rapamycin for disease-free survival in breast cancer patients receiving neoadjuvant chemotherapy.

The mammalian target of rapamycin (mTOR)/eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) pathway plays a critical role in cell growth, survival and angiogenesis, and has been demonstrated to correlate with human epidermal growth factor receptor 2 (HER2) status. Neoadjuvant chemotherapy (NAC), also known as preoperative therapy, is now well established in the treatment of inoperable locally advanced and inflammatory breast cancer. In vitro study has shown that mTOR inhibitors, together with cytotoxic agents, exhibit tumor cell killing activity. A number of non-randomized studies in HER2-positive trastuzumab-resistant metastatic breast cancer have revealed the antitumor activity of mTOR inhibitors when used together with standard chemotherapy plus trastuzumab. In the present study, the expression levels of phosphorylated (p)-mTOR and p-4E-BP1 were analyzed in breast cancer patients prior to and following NAC, to determine whether p-mTOR and p-4E-BP1 affect the response to NAC and the subsequent survival. Formalin-fixed, paraffin-embedded tissues representing matched pairs of core biopsy (pre-NAC) and surgical specimen (post-NAC) from 83 patients with invasive ductal carcinomas were collected. Immunohistochemistry was performed to evaluate the expression of p-mTOR and p-4E-BP1 using a semi-quantitative scoring system by two pathologists. It was found that the expression of p-mTOR and p-4E-BP1 was downregulated following NAC. The decrease in mTOR expression following NAC was found to positively correlate with HER2 expression and the reduction of tumor sizes. The high expression of p-mTOR and p-4E-BP1 in pre-NAC specimens was associated with poor disease-free survival (DFS). Furthermore, the high expression of p-mTOR in post-NAC specimens was associated with poor DFS, regardless of whether the expression was high or low in the pre-NAC specimens. In conclusion, NAC was found to decrease the expression levels of p-mTOR and p-4E-BP1. The p-mTOR expression post-NAC may potentially serve as a predictor for DFS. However, further study is required to clarify the mechanism and to evaluate the predictive value of the phosphatidylinositol 3-kinase/Akt/mTOR/4E-BP1 pathway in NAC.

The combined effect of survivin-targeted shRNA and emodin on the proliferation and invasion of ovarian cancer cells.

Survivin has been shown to be highly expressed in ovarian cancers, but not normal ovarian tissue, which makes it an attractive target for ovarian cancer treatment. Emodin is a traditional Chinese medicine that has been found to inhibit proliferation and induce apoptosis in ovarian cancer cells. Thus, in our study, we combined survivin-targeted shRNA (sur-shRNA) with emodin and tested the effects of this combination on ovarian cancer cells to identify more effective therapeutics against ovarian cancer. A sur-shRNA plasmid was constructed and transfected into the ovarian cancer cell lines SKOV3 and HO8910, and the cells were cultured for 24 h. The cells were then treated with emodin for specific time periods and assessed for viability and apoptosis using the MTT assay and flow cytometry, respectively. Cell invasion was also measured using a Matrigel invasion assay. The shRNA specific for survivin effectively reduced the expression of survivin at the mRNA and protein levels in SKOV3 and HO8910 cells. Both emodin and shRNA-mediated knockdown of survivin significantly inhibited cell proliferation, induced apoptosis, and suppressed invasion in SKOV3 and HO8910 cells (P<0.05). Moreover, the combination of the agents significantly enhanced these effects (P<0.05). We found that the combination of sur-shRNA and emodin could be effective in the treatment of ovarian cancer.

Potent antitumoral effects of targeted promoter-driven oncolytic adenovirus armed with Dm-dNK for breast cancer in vitro and in vivo.

Currently, no curative treatments are available for late-stage metastatic or recurrent breast cancer, because the cancer tolerates both chemotherapy and endocrine therapy. In this study, we investigated the feasibility of a dual-regulated oncolytic adenoviral vector with a novel suicide gene to treat breast cancer. Following targeted gene virotherapy of conditionally replicating adenoviruses (CRAds), the novel suicide gene of multisubstrate deoxyribonucleoside kinase of Drosophila melanogaster (Dm-DNK) was inserted into the double-regulated oncolytic adenovirus SG500 to ensure more safety and enhanced antitumor activity against breast cancer both in vitro and in vivo. Selective replication, cell-killing efficacy, and cytotoxicity, combined with chemotherapeutics were investigated in several breast cell lines (MDA-MB-231 and MCF-7), normal cells (WI-38 and MRC-5), and human (MDA-MB-231) tumor models in vivo. The double-regulated SG500-dNK had high cell-killing activity in breast cancer. Replication was similar to wild-type in breast cells and was attenuated in normal cells. SG500-dNK combined with the chemotherapeutics (E)-5-(2-bromovinyl)-2'-deoxyuridine (Bvdu) and 2',2'-difluoro-deoxycytidine (dFdC) resulted in synergistically enhanced cell killing and greatly improved antitumor efficacy in vitro or in breast xenografts in vivo. These data suggest that the novel oncolytic variant SG500-dNK is a promising candidate for targeting breast tumors specifically when combined with chemotherapeutics.

Cytotoxic effects of adenovirus- and lentivirus-mediated expression of Drosophila melanogaster deoxyribonucleoside kinase on Bcap37 breast cancer cells.

Gene transfer using different viral vectors has demonstrated different antitumor effects in suicide gene therapy. In the present study, in order to optimize the efficacy of replication-defective adenoviral and lentiviral vectors for gene therapy, RT-PCR was used to evaluate the expression of Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) in the Bcap37 human breast cancer cell line, dThd was used to determine the activity of Dm-dNK, cell cytotoxicity was evaluated by MTT assay and cell proliferation was assessed using a hemocytometer. Moreover, apoptosis induction was evaluated by the Annexin V-FITC-labeled FACS method. Furthermore, BALB/C nude mice bearing tumors were treated with Dm-dNK mediated with the pyrimidine nucleoside analog, brivudine [BVDU, (E)-5-(2-bromovinyl)-2'-deoxyuridine]. Our results indicated that the gene expression of Dm-dNK transfected by adenoviral and lentiviral vectors may be detected and that its long-term activity may be retained. Both vectors containing the Dm-dNK gene revealed high cytotoxicity and sensitized cell apoptosis from the BVDU prodrug. In tumor models, lentivirus-mediated gene therapy significantly inhibited the growth of tumors compared with adenovirus-mediated gene therapy. Although adenovirus- and lentivirus-transduced Dm-dNK reveal strong treatment efficacy in vitro, the latter has great potential due to the long-term expression of the therapeutic gene in vivo.

Conditionally replicating adenovirus SG500-expressed mutant Dm-dNK gene for breast cancer therapy.

The purpose of this analysis was to investigate the enzyme activity and specificity of using adenovirus-mediated Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) mutants in combination with gemcitabine. Compared with herpes simplex type 1 thymidine kinase (HSV-TK) and other known dNKs, this Dm-dNK enzyme has a broader substrate specificity and a higher catalytic rate. We created the Dm-dNK mutants (dNKmu) by site-directed mutagenesis at the sites of 244E, 245S, 251S and 252R, with the last 10 amino acids in the amino acid sequence randomly mutated. We evaluated the enzyme activity and substrate specificity. The engineered enzymes showed a relative increase in phosphorylation in the nucleoside analogs of BVDU ((E)-5­(2-Bromovinyl)-2'-deoxyuridine) or gemcitabine (DFDC, 2',2'-difluoro-deoxycytidine) compared with the wild-type enzyme. The dNKmu enzymes were expressed in the breast cancer cell lines MDA-MB-231 (ER-) and MCF7 (ER+). In studying the sensitivity of the cell lines to DFDC, conditionally replicative adenovirus (CRAd) SG500-dNKmu showed higher expression and enzymatic activity than the replication-defective adenovirus SG500 in cancer cells, but with less cytotoxicity to cancer cells than that of SG500. Our data suggest that the triple phosphorylated DFDC catalyzed by dNKmu inhibited the replication of adenovirus with a simultaneous positive therapeutic effect to cancer cells. Therefore, concomitant use of the SG500­dNKmu and DFDC could be a novel targeted strategy in suicide gene therapy with safe control of excessive virus replication.

Adenovirus-mediated Drosophila melanogaster deoxyribonucleoside kinase mutants combined with gemcitabine harbor a safe cancer treatment profile.

The purpose of this analysis was to investigate the enzyme activity and specificity of adenovirus-mediated Drosophila melanogaster deoxyribonucleoside kinase (Dm-dNK) mutants in combination with gemcitabine. Compared to herpes simplex type 1 thymidine kinases (HSV-TK) and other known dNKs, this Dm-dNK enzyme has a broader substrate specificity and a higher catalytic rate. We created the Dm-dNK mutants (dNKmut) by site-directed mutagenesis at the sites of 244E, 245S, 251S, and 252R, with the last 10 amino acids in the amino acid sequence randomly alternated. We subsequently evaluated the enzyme activity and substrate specificity. The engineered enzymes showed a relative increase in phosphorylation in the nucleoside analogs of gemcitabine (dFdC, 2',2'-difluoro-deoxycytidine) compared to the wild-type enzyme. The dNKmut enzymes were expressed in breast (Bcap37) and gastric (SGC-7901) cancer cell lines. In studying the sensitivity of the cell lines to dFdC, conditionally replicative adenovirus (CRAd) ZD55-dNKmut showed higher expression and enzymatic activity than the replication-defective adenovirus Ad-dNKmut in cancer cells, but with less cytotoxicity to cancer cells than that of Ad-dNKmut. Our data suggest that the triple phosphorylated dFdC catalyzed by dNKmut inhibited the replication of adenovirus with a simultaneous positive therapeutic effect on cancer cells. Therefore, concomitant use of the ZD55-dNKmut and dFdC could be a novel targeted strategy in suicide gene therapy with safe control of excessive virus replication.

Retrovirus-mediated Drosophila melanogaster multisubstrate deoxyribonucleoside kinase gene therapy of gastric cancer cells in vitro and in vivo.

AIM: The cytotoxicity of the Drosophila melanogaster multisubstrate deoxyribonucleoside kinase (Dm-dNK)/nucleoside analog system to human gastric carci-noma cells was evaluated in vitro and in vivo for the development of novel gene therapy for gastric cancer. METHODS: MGC-803 and BGC-823 cells were infected with retroviral vectors containing the Dm-dNK gene expressing Dm-dNK in its active form. [(3)H]-labeled substrates were used for enzyme activity assays and cytotoxicities were evaluated in vitro by MTT assay and annexin-V-FITC labeled FACS methods. Bystander effect assay was performed by MTT assay using a mixture of cells with and without expressed Dm-dNK. Anti-tumor efficacy was also examined in vivo. RESULTS: Nucleoside analogs were significantly more cytotoxic to Dm-dNK-expressing cells than to their parental counterparts, and death was attributable to apoptosis. Implementation of the Dm-dNK/nucleoside analog system was associated with 'bystander' effects in vitro and suppressed the growth of MGC-803 tumors in mice. CONCLUSION: The Dm-dNK/nucleoside analoguesystem possesses significant potential as suicide gene therapy for human gastric carcinoma.

Effects of MK-801, taurine and dextromethorphan on neurotoxicity caused by manganese in rats.

The effects of manganese on the activities of GS, PAG, SDH and Na(+)-K(+)-ATPase were investigated and the impact of MK-801, Tau and DM on manganese-induced neurotoxicity were observed in rats. Seventy Wistar rats were divided into seven groups, 10 animals for each group. The first group was the control group, the second to fourth groups were 8, 40 and 200 micromol/kg MnCl(2) groups, the fifth to seventh groups were 0.3 micromol/kg MK-801, 1 micromol/kg Tau and 13.5 micromol/kg DM pretreatment groups. The animals were injected with manganese chloride for 25 days and pretreated for every other day. Manganese resulted in the reduction of GS, SDH and Na(+)-K(+)-ATPase activities, and the increase of PAG activity. The percentage of positive area and integral optical density of glutamate immunocreative cell were significantly increased in the group given 200 micromol/kg MnCl(2) alone. Pretreatment with MK-801, Tau and DM can antagonize neurotoxicity induced by manganese in the certain extent.