Targeting EMT using low-dose Teniposide by downregulating ZEB2-driven activation of RNA polymerase I in breast cancer.

Metastatic dissemination from the primary tumor is a complex process that requires crosstalk between tumor cells and the surrounding milieu and involves the interplay between numerous cellular-signaling programs. Epithelial-mesenchymal transition (EMT) remains at the forefront of orchestrating a shift in numerous cellular programs, such as stemness, drug resistance, and apoptosis that allow for successful metastasis. Till date, there is limited success in therapeutically targeting EMT. Utilizing a high throughput screen of FDA-approved compounds, we uncovered a novel role of the topoisomerase inhibitor, Teniposide, in reversing EMT. Here, we demonstrate Teniposide as a potent modulator of the EMT program, specifically through an IRF7-NMI mediated response. Furthermore, Teniposide significantly reduces the expression of the key EMT transcriptional regulator, Zinc Finger E-Box Binding Homeobox 2 (ZEB2). ZEB2 downregulation by Teniposide inhibited RNA polymerase I (Pol I) activity and rRNA biogenesis. Importantly, Teniposide treatment markedly reduced pulmonary colonization of breast cancer cells. We have uncovered a novel role of Teniposide, which when used at a very low concentration, mitigates mesenchymal-like invasive phenotype. Overall, its ability to target EMT and rRNA biogenesis makes Teniposide a viable candidate to be repurposed as a therapeutic option to restrict breast cancer metastases.

Discovery of 4,6-O-Thenylidene-ß-d-glucopyranoside-(2″-acetamido, 3″-acetyl-di-S-5-fluorobenzothizole/5-fluorobenzoxazole)-4'-demethylepipodophyllotoxin as Potential Less Toxic Antitumor Candidate Drugs by Reducing DNA Damage and Less Inhibition of PI3K.

As an FDA-approved drug, teniposide, was utilized in cancer treatment but was accompanied by a strong side effect in long-term clinical trials. This work discovered potential candidate drugs with low toxicity by modifying the molecule structure of teniposide through a structure-guided drug design approach. The IC50 value of novel 4,6-O-thenylidene-ß-d-glucopyranoside-(2″-acetamido, 3″-acetyl-di-S-5-fluorobenzothizole/5-fluorobenzoxazole)-4'-demethylepipodophyllotoxin (compounds 15 and 16) was 120.4-125.1 µM, which was significantly improved by around 10 times more than teniposide (11.5-22.3 µM) against healthy human cells (i.e., HL-7702, H8, MRC-5, and HMEC). In vivo studies demonstrated compounds 15 and 16 significantly suppressed the tumor growth in the HepG2 cell xenograft model without exhibiting obvious toxicity (LD50 values of 208.45 and 167.52 mg/kg), which was lower than that of teniposide (LD50 = 46.12 mg/kg). Compounds 15 and 16 caused mild γH2AX phosphorylation for low DNA toxicity and less inhibition of PI3K/Akt. Compounds 15 and 16 might be potential antitumor drugs with low toxicity.

cGAS/STING axis mediates a topoisomerase II inhibitor-induced tumor immunogenicity.

Checkpoint blockade antibodies have been approved as immunotherapy for multiple types of cancer, but the response rate and efficacy are still limited. There are few immunogenic cell death (ICD)-inducing drugs available that can kill cancer cells, enhance tumor immunogenicity, increase the in vivo immune infiltration, and thereby boosting a tumor response to immunotherapy. So far, the ICD markers have been identified as the few immuno-stimulating characteristics of dead cells, but whether the presence of such ICD markers on tumor cells translates into enhanced antitumor immunity in vivo is still investigational. To identify anticancer drugs that could induce tumor cell death and boost T cell response, we performed drug screenings based on both an ICD reporter assay and T cell activation assay. We identified that teniposide, a DNA topoisomerase II inhibitor, could induce high mobility group box 1 (HMGB1) release and type I interferon signaling in tumor cells, and teniposide-treated tumor cells could activate antitumor T cell response both in vitro and in vivo. Mechanistically, teniposide induced tumor cell DNA damage and innate immune signaling including NF-κB activation and STING-dependent type I interferon signaling, both of which contribute to the activation of dendritic cells and subsequent T cells. Furthermore, teniposide potentiated the antitumor efficacy of anti-PD1 on multiple types of mouse tumor models. Our findings showed that teniposide could trigger tumor immunogenicity, and enabled a potential chemo-immunotherapeutic approach to potentiate the therapeutic efficacy of anti-PD1 immunotherapy.

Teniposide regulates the phenotype switching of vascular smooth muscle cells in a miR-21-dependent manner.

The switch of vascular smooth muscle cells (SMCs) from the contractile phenotype to proliferative one can make contributions to atherosclerosis and neointima formation. MiR-21 can prevent the rupture of advanced lesion plaques. We previously reported the protection of DNA topoisomerase II (Topo II) inhibitors against atherosclerosis and vascular calcification. However, it remains unknown if Topo II inhibitors can change SMC phenotypes. Herein, we show that teniposide protected SMC phenotype switching during atherosclerosis by enhancing expression of smooth muscle α-actin (SMA) while reducing osteopontin (OPN) expression in aortic lesion plaques. In vitro, teniposide induced expression of smooth muscle protein 22-α and calponin 1, but inhibited expression of OPN and epiregulin in human aortic SMCs (HASMCs). Moreover, teniposide attenuated platelet derived growth factor-BB-induced HASMC proliferation and migration. Mechanistically, the effect of teniposide on SMC phenotypes was completed, at least in part, by activating miR-21 expression. In addition, teniposide ameliorated ligation-induced carotid artery remodeling in C57BL/6J mice by regulating SMA and OPN expression. Taken together, our study demonstrates that teniposide regulates SMC phenotype switching by upregulating expression of contractile genes in a miR-21-dependent manner, and this function is an important anti-atherogenic mechanism of teniposide.

Inhibition of Vascular Calcification.

Objective- Vascular calcification is a major risk factor for rupture of atherosclerotic plaques. High expression of BMP2 (bone morphogenetic protein 2) in lesions suggests its importance in vascular calcification during atherosclerosis. Teniposide is a Topo II (DNA topoisomerase II) inhibitor and is used for cancer treatment. Previously, we reported that teniposide activated macrophage ABCA1 (ATP-binding cassette transporter A1) expression and free cholesterol efflux indicating Topo II inhibitors may demonstrate antiatherogenic properties. Herein, we investigated the effects of teniposide on the development of atherosclerosis and vascular calcification in apoE-/- (apoE deficient) mice. Approach and Results- apoE-/- mice were fed high-fat diet containing teniposide for 16 weeks, or prefed high-fat diet for 12 weeks followed by high-fat diet containing teniposide for 4 weeks. Atherosclerosis and vascular calcification were determined. Human aortic smooth muscle cells were used to determine the mechanisms for teniposide-inhibited vascular calcification. Teniposide reduced atherosclerotic lesions. It also substantially reduced vascular calcification without affecting bone structure. Mechanistically, teniposide reduced vascular calcification by inactivating BMP2/(pi-Smad1/5/8 [mothers against decapentaplegic homolog 1, 5, and 8])/RUNX2 (runt-related transcription factor 2) axis in a p53-dependent manner. Furthermore, activated miR-203-3p by teniposide functioned as a link between activated p53 expression and inhibited BMP2 expression in inhibition of calcification. Conclusions- Our study demonstrates that teniposide reduces vascular calcification by regulating p53-(miR-203-3p)-BMP2 signaling pathway, which contributes to the antiatherogenic properties of Topo II inhibitors.

A novel cell-based screening assay for small-molecule MYB inhibitors identifies podophyllotoxins teniposide and etoposide as inhibitors of MYB activity.

The transcription factor MYB plays key roles in hematopoietic cells and has been implicated the development of leukemia. MYB has therefore emerged as an attractive target for drug development. Recent work has suggested that targeting MYB by small-molecule inhibitors is feasible and that inhibition of MYB has potential as a therapeutic approach against acute myeloid leukemia. To facilitate the identification of small-molecule MYB inhibitors we have re-designed and improved a previously established cell-based screening assay and have employed it to screen a natural product library for potential inhibitors. Our work shows that teniposide and etoposide, chemotherapeutic agents causing DNA-damage by inhibiting topoisomerase II, potently inhibit MYB activity and induce degradation of MYB in AML cell lines. MYB inhibition is suppressed by caffeine, suggesting that MYB is inhibited indirectly via DNA-damage signalling. Importantly, ectopic expression of an activated version of MYB in pro-myelocytic NB4 cells diminished the anti-proliferative effects of teniposide, suggesting that podophyllotoxins disrupt the proliferation of leukemia cells not simply by inducing general DNA-damage but that their anti-proliferative effects are boosted by inhibition of MYB. Teniposide and etoposide therefore act like double-edged swords that might be particularly effective to inhibit tumor cells with deregulated MYB.

Teniposide ameliorates bone cancer nociception in rats via the P2X7 receptor.

Bone pain associated with advanced tumor metastasis is the most severe threat to life quality of patients. Highly efficient and low-toxic therapeutics is of urgent need for this complication. Bone tumor metastasis was established by direct bone inoculation of Walker 256 mammary gland carcinoma cells. Bone nociception was measured by mechanical allodynia, thermal hyperalgesia and spontaneous flinches. P2X7R level was determined by immunoblotting. The inward current was recorded by a patch clamp. The related cytokines were determined by ELISA. Our results showed that teniposide (TN) treatment significantly ameliorated bone nociception associated with tumor inoculation to a comparable extent with P2X7-specific inhibitor, BBG, in rat model. The efficient blockade of inward current generation and pro-inflammatory cytokines secretion were observed upon administration with TN. Our data highlighted the therapeutic potency of TN in this complication associated with tumor metastasis and warrants further clinical investigations.

Preparation and evaluation of teniposide-loaded polymeric micelles for breast cancer therapy.

Self-assembled polymeric micelles have been widely applied in anticancer drug delivery systems. Teniposide is a broad spectrum and effective anticancer drug, but its poor water-solubility and adverse effects of commercial formulation (VM-26) restrict its clinical application. In this work, teniposide-loaded polymeric micelles were prepared based on monomethoxy-poly(ethylene glycol)-poly(ε-caprolactone-co-d,l- lactide) (MPEG-PCLA) copolymers through a thin-film hydration method to improve the hydrophilic and reduce the systemic toxicity. The prepared teniposide micelles were without any surfactants or additives and monodisperse with a mean particle size of 29.6±0.3nm. The drug loading and encapsulation efficiency were 18.53±0.41% and 92.63±2.05%, respectively. The encapsulation of teniposide in MPEG-PCLA micelles showed a slow and sustained release behavior of teniposide in vitro and improved the terminal half-life (t1/2), the area under the plasma concentration-time curve (AUC) and retention time of teniposide in vivo compared with VM-26. In addition, teniposide micelles also enhanced the cellular uptake by MCF-7 breast cancer cells in vitro and increased the distribution in tumors in vivo. Teniposide micelles showed an excellent safety with a maximum tolerated dose (MTD) of approximately 50mg teniposide/kg body weight, which was 2.5-fold higher than that of VM-26 (about 20mg teniposide/kg body weight). Furthermore, the intravenous application of teniposide micelles effectively suppressed the growth of subcutaneous MCF-7 tumor in vivo and exhibited a stronger anticancer effect than that of VM-26. These results suggested that we have successfully prepared teniposide-loaded MPEG-PCLA micelles with improved safety, hydrophilic and therapeutic efficiency, which are efficient for teniposide delivery. The prepared teniposide micelles may be promising in breast cancer therapy.

Cremophor-free intravenous self-microemulsions for teniposide: Safety, antitumor activity in vitro and in vivo.

The study was designed to identify the safety and antitumor activity of teniposide self-microemulsified drug delivery system (TEN-SMEDDS) previously developed, and to provide evidence for the feasibility and effectiveness of TEN-SMEDDS for application in clinic. The TEN-SMEDDS could form fine emulsion with mean diameter of 279 ± 19 nm, Zeta potential of -6.9 ± 1.4 mV, drug loading of 0.04 ± 0.001% and entrapment efficiency of 98.7 ± 1.6% after dilution with 5% glucose, respectively. The safety, including hemolysis, hypersensitivity, vein irritation and toxicity in vivo, and antitumor activity were assessed, VUNON as a reference. Sulforhodamine B assays demonstrated that the IC50 of TEN-SMEDDS against C6 and U87MG cells were higher than that of VUMON. But the effect of TEN-SMEDDS on the cell cycle distribution and cell apoptotic rate was similar to that of VUMON as observed by flow cytometry. Likewise, the antitumor activity of TEN-SMEDDS was considerable to that of VUMON. Finally, the TEN-SMEDDS exhibited less body weight loss, lower hemolysis and lower myelosuppression as compared with VUMON. In conclusion, promising TEN-SMEDDS retained the antitumor activity of teniposide and was less likely to cause some side effects compared to VUMON. It may be favorable for the application in clinic.

Regulation of Hepatic Cholesteryl Ester Transfer Protein Expression and Reverse Cholesterol Transport by Inhibition of DNA Topoisomerase II.

Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from high density lipoprotein to triglyceride-rich lipoproteins. CETP expression can be transcriptionally activated by liver X receptor (LXR). Etoposide and teniposide are DNA topoisomerase II (Topo II) inhibitors. Etoposide has been reported to inhibit atherosclerosis in rabbits with un-fully elucidated mechanisms. In this study we determined if Topo II activity can influence cholesterol metabolism by regulating hepatic CETP expression. Inhibition of Topo II by etoposide, teniposide, or Topo II siRNA increased CETP expression in human hepatic cell line, HepG2 cells, which was associated with increased CETP secretion and mRNA expression. Meanwhile, inhibition of LXR expression by LXR siRNA attenuated induction of CETP expression by etoposide and teniposide. Etoposide and teniposide induced LXRα expression and LXRα/ß nuclear translocation while inhibiting expression of receptor interacting protein 140 (RIP140), an LXR co-repressor. In vivo, administration of teniposide moderately reduced serum lipid profiles, induced CETP expression in the liver, and activated reverse cholesterol transport in CETP transgenic mice. Our study demonstrates a novel function of Topo II inhibitors in cholesterol metabolism by activating hepatic CETP expression and reverse cholesterol transport.

Encapsulation of teniposide into albumin nanoparticles with greatly lowered toxicity and enhanced antitumor activity.

Teniposide (VM-26) is a semisynthetic derivative of podophyllotoxin effective for the treatment of many types of tumors. However, the poor water solubility and adverse effects restrict its clinical use. Our study aimed to develop a novel phospholipid complex albumin nanoparticle (VM-E80-AN) to reduce the systemic toxicity and enhance antitumor activity of VM-26. Egg yolk lecithin E80 and human serum albumin (HSA) were used as the main excipients to replace Cremophor EL in the commercial formulation. The physicochemical properties of VM-E80-AN were characterized to optimize the formulation. Cell and animal studies were further carried out to estimate its tumor inhibition efficacy, biodistribution, and toxicity. Comparison between VM-26 solution and VM-E80-AN showed that VM-E80-AN significantly reduced the toxicity of VM-26 and enhanced the anticancer efficacy of the drug. Thus, VM-E80-AN represents a safe and promising formulation of teniposide for clinical application.

MiR-181b sensitizes glioma cells to teniposide by targeting MDM2.

BACKGROUND: Although the incidence of glioma is relatively low, it is the most malignant tumor of the central nervous system. The prognosis of high-grade glioma patient is very poor due to the difficulties in complete resection and resistance to radio-/chemotherapy. Therefore, it is worth investigating the molecular mechanisms involved in glioma drug resistance. MicroRNAs have been found to play important roles in tumor progression and drug resistance. Our previous work showed that miR-181b is involved in the regulation of temozolomide resistance. In the current study, we investigated whether miR-181b also plays a role in antagonizing the effect of teniposide. METHODS: MiR-181b expression was measured in 90 glioma patient tissues and its relationship to prognosis of these patients was analyzed. Cell sensitivity to teniposide was tested in 48 primary cultured glioma samples. Then miR-181b stably overexpressed U87 cells were generated. The candidate genes of miR-181b from our previous study were reanalyzed, and the interaction between miR-181b and target gene MDM2 was confirmed by dual luciferase assay. Cell sensitivity to teniposide was detected on miR-181b over expressed and MDM2 down regulated cells. RESULTS: Our data confirmed the low expression levels of miR-181b in high-grade glioma tissues, which is related to teniposide resistance in primary cultured glioma cells. Overexpression of miR-181b increased glioma cell sensitivity to teniposide. Through target gene prediction, we found that MDM2 is a candidate target of miR-181b. MDM2 knockdown mimicked the sensitization effect of miR-181b. Further study revealed that miR-181b binds to the 3'-UTR region of MDM2 leading to the decrease in MDM2 levels and subsequent increase in teniposide sensitivity. Partial restoration of MDM2 attenuated the sensitivity enhancement by miR-181b. CONCLUSIONS: MiR-181b is an important positive regulator on glioma cell sensitivity to teniposide. It confers glioma cell sensitivity to teniposide through binding to the 3'-UTR region of MDM2 leading to its reduced expression. Our findings not only reveal the novel mechanism involved in teniposide resistance, but also shed light on the optimization of glioma treatment in the future.

Toward discovering new anti-cancer agents targeting topoisomerase IIα: a facile screening strategy adaptable to high throughput platform.

Topoisomerases are a family of vital enzymes capable of resolving topological problems in DNA during various genetic processes. Topoisomerase poisons, blocking reunion of cleaved DNA strands and stabilizing enzyme-mediated DNA cleavage complex, are clinically important antineoplastic and anti-microbial agents. However, the rapid rise of drug resistance that impedes the therapeutic efficacy of these life-saving drugs makes the discovering of new lead compounds ever more urgent. We report here a facile high throughput screening system for agents targeting human topoisomerase IIα (Top2α). The assay is based on the measurement of fluorescence anisotropy of a 29 bp fluorophore-labeled oligonucleotide duplex. Since drug-stabilized Top2α-bound DNA has a higher anisotropy compared with free DNA, this assay can work if one can use a dissociating agent to specifically disrupt the enzyme/DNA binary complexes but not the drug-stabilized ternary complexes. Here we demonstrate that NaClO4, a chaotropic agent, serves a critical role in our screening method to differentiate the drug-stabilized enzyme/DNA complexes from those that are not. With this strategy we screened a chemical library of 100,000 compounds and obtained 54 positive hits. We characterized three of them on this list and demonstrated their effects on the Top2α-mediated reactions. Our results suggest that this new screening strategy can be useful in discovering additional candidates of anti-cancer agents.

DNA topoisomerase II inhibitors induce macrophage ABCA1 expression and cholesterol efflux-an LXR-dependent mechanism.

ATP-binding cassette transporter A1 (ABCA1) facilitates cholesterol efflux and thereby inhibits lipid-laden macrophage/foam cell formation and atherosclerosis. ABCA1 expression is transcriptionally regulated by activation of liver X receptor (LXR). Both etoposide and teniposide are DNA topoisomerase II (Topo II) inhibitors and are chemotherapeutic medications used in the treatment of various cancers. Interestingly, etoposide inhibits atherosclerosis in rabbits by unclear mechanisms. Herein, we report the effects of etoposide and teniposide on macrophage ABCA1 expression and cholesterol efflux. Both etoposide and teniposide increased macrophage free cholesterol efflux. This increase was associated with increased ABCA1 mRNA and protein expression. Etoposide and teniposide also increased ABCA1 promoter activity in an LXR-dependent manner and formation of the LXRE-LXR/RXR complex indicating that transcriptional induction had occurred. Expression of ABCG1 and fatty acid synthase (FAS), another two LXR-targeted genes, was also induced by etoposide and teniposide. In vivo, administration of mice with either etoposide or teniposide induced macrophage ABCA1 expression and enhanced reverse cholesterol transport from macrophages to feces. Taken together, our study indicates that etoposide and teniposide increase macrophage ABCA1 expression and cholesterol efflux that may be attributed to the anti-atherogenic properties of etoposide. Our study also describes a new function for Topo II inhibitors in addition to their role in anti-tumorigenesis.

A self-assembled nanocarrier loading teniposide improves the oral delivery and drug concentration in tumor.

We attempted to improve the oral delivery of lipophilic teniposide to achieve higher drug concentration in tumor by self-assembled nanocarrier for further oral chemotherapy. The teniposide loaded self-assembled nanocarrier (TSN) was spherical nanometric particles with narrow size distribution. The intestinal absorption of teniposide from TSN was obviously improved 4.09- and 6.35-fold in duodenum and jejunum at 0.5h after oral administration, then significantly decreased with the prolongation of time. The cellular uptake of TSN in Caco-2 cell monolayer was significantly enhanced over 3 folds and increased with incubation time. Moreover, TSN could be internalized into Caco-2 cell monolayer through clathrin-mediated endocytosis pathway, and then mainly transported into the systemic circulation via portal vein and intestinal lymphatic pathway. The pharmacokinetic results indicated that the AUC(0-t) value of TSN in rats was significantly improved 5.41-fold than that of teniposide solution, moreover, the teniposide concentration in tumor from TSN was obviously improved over 7-fold in tumor bearing mice. The captured image indicated that the oral administered TSN could specifically accumulate in tumor in the xenograft model. Therefore, the self-assembled nanocarrier was promising to enhance the oral delivery of lipophilic teniposide and its concentration in tumor for oral chemotherapy.

Knockdown of apoptosis repressor with caspase recruitment domain (ARC) increases the sensitivity of human glioma cell line U251MG to VM-26.

Previous studies have demonstrated that apoptosis repressor with caspase recruitment domain (ARC) is up-regulated in many forms of malignant tumors and low levels of ARC protein were expressed in normal human brain tissue. Little is known expression of ARC in glioma. Here, we found that ARC protein was highly expressed in primary human glioma when compared with normal brain tissues. A decrease in cell viability and an increase in apoptosis were observed in U251MG cells after ARC was knocked down. Knockdown of ARC was confirmed by western blotting. Knockdown of ARC promoted caspase-8, caspase-3 activation and Bax accumulation. These results indicate that ARC has a anti-apoptosis function in glioma.

Knockdown of AKT2 expression by RNA interference inhibits proliferation, enhances apoptosis, and increases chemosensitivity to the anticancer drug VM-26 in U87 glioma cells.

The AKT2 kinase (protein kinas Bß) is frequently overexpressed in malignant gliomas. In this study, the human glioblastoma cell line U87 was stably transfected with a lentivirus vector expressing a short hairpin RNA (shRNA) targeting AKT2. Knockdown of AKT2 by the shRNA inhibited U87 cell proliferation and increased the rate of apoptosis. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blot analysis revealed that cells stably underexpressing AKT2 showed lower expression of the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2) and enhanced expression of the apoptosis effector caspase-3 compared to U87 cells stably transfected with a control vector. Furthermore, expression levels of AKT2 were correlated with the IC50 of the antitumor drug VM-26 (teniposide); the VM-26 IC50 was reduced from 6.46±0.42µg/ml in control glioma cells to 1.15±0.22µg/ml in U87 cells underexpressing AKT2. Combined AKT2 knockdown and VM-26 treatment inhibited cell proliferation in vitro more effectively than either treatment alone. Knockdown of AKT2 expression was associated with decreased expression of the multidrug resistance-associated protein 1 (MRP1) without affecting MRP1 mRNA expression. However, the mRNA and protein levels of MDR1 (p-glycoprotein) were unaffected by AKT2 knockdown. These results indicate that inhibition of AKT2 expression may be an effective means for overcoming AKT2-associated chemoresistance in human malignant glioma cells and may represent a potential gene-targeting approach to treat glioma.

Action of db-cAMP on the bystander effect and chemosensitivity through connexin 43 and Bcl-2-mediated pathways in medulloblastoma cells.

Medulloblastoma (MB) is one of the most common malignant brain tumors of childhood and is associated with a poor prognosis. Gap-junctional intercellular communication (GJIC) is an important mode for cell-to-cell communication. Dysfunctional GJIC is exhibited in most cancer cells. There is significant evidence that GJIC is important in at least some prodrug/suicide gene systems by augmenting the bystander effect (BE). GJIC is made up of connexins (Cxs), among which Cx43 is present in most tissues. Bcl-2, an important apoptosis blocker, is closely associated with the sensitivity to anticancer drugs. Our study showed that dibutyryl cyclic adenosine monophosphate (db-cAMP) upregulated the Cx43 expression and GJIC function in Daoy medulloblastoma cells. It directly enhanced the BE using a herpes simplex virus thymidine kinase (HSV­tk)/ganciclovir (GCV) system, which was blocked by a Cx43 inhibitor. In addition, db-cAMP increased the cytotoxicity of temozolomide and teniposide, possibly by downregulating the Bcl-2 expression and inducing apoptosis. Taken together, we demonstrated the beneficial effect of db-cAMP in treating medulloblastoma depending on the upregulation of BE and chemosensitivity through Cx43 and Bcl-2-mediated pathways.

Molecular cytogenetic evaluation of the aneugenic effects of teniposide in somatic and germinal cells of male mice.

The ability of topoisomerase II inhibitor, teniposide, to induce aneuploidy and meiotic delay in somatic and germinal cells of male mice was investigated by fluorescence in situ hybridisation (FISH) assay using labelled DNA probes and 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, respectively. Colchicine and mitomycin C were used as a positive control aneugen and clastogen, respectively, and these compounds produced the expected responses. Using FISH assay with centromeric and telomeric DNA probes for erythrocyte, micronuclei (MN) showed that teniposide is not only clastogenic but also aneugenic in somatic cells in vivo. The assay also showed that chromosomes can be enclosed in the MN before and after centromere separation. By using the BrdU incorporation assay, it could be shown that the meiotic delay caused by teniposide in germ cells was ∼48 h. Disomic and diploid sperms were shown in epididymal sperm hybridised with DNA probes specific for chromosomes 8, X and Y after teniposide treatment. The prevalence of autodiploid (XX88 and YY88) sperm and disomic XX8 or YY8 sperm indicates that the second meiotic division was more sensitive to teniposide than the first meiotic division. The results also suggest that earlier prophase stages contribute relatively less to teniposide-induced aneuploidy. Both the clastogenic and the aneugenic potential of teniposide can give rise to the development of secondary tumours and abnormal reproductive outcomes in cured cancer patients and medical personnel exposing to drug regimens that include teniposide. Thus, genetic counselling of these patients should take place before the start of chemotherapy and should take the present results into consideration.

Recent advances in semisynthesis, biosynthesis, biological activities, mode of action, and structure-activity relationship of podophyllotoxins: an update (2008-2010).

Podophyllotoxin, one of the well-known naturally occurring aryltetralin lignans, has been used as the lead-compound for the preparation of potent anticancer agents, such as etoposide, teniposide, and etopophos. In our previous review, we described the advances of podophyllotoxin derivatives from 2003 and 2007. In recent years, an increased number of interesting research work has been carried out on the podophyllotoxins. As a continuation, the present review summarizes and highlights the update advances of podophyllotoxin derivatives from 2008 and 2010 in regard to semisynthesis, biosynthesis, biological activities, mode of action and structure-biological activity relationship.