c-Myc downregulation: a critical molecular event in resveratrol-induced cell cycle arrest and apoptosis of human medulloblastoma cells

Remodeling tumor microenvironment with natural products to overcome drug resistance

With cancer incidence rates continuing to increase and occurrence of resistance in drug treatment, there is a pressing demand to find safer and more effective anticancer strategy for cancer patients. Natural products, have the advantage of low toxicity and multiple action targets, are always used in the treatment of cancer prevention in early stage and cancer supplement in late stage. Tumor microenvironment is necessary for cancer cells to survive and progression, and immune activation is a vital means for the tumor microenvironment to eliminate cancer cells. A number of studies have found that various natural products could target and regulate immune cells such as T cells, macrophages, mast cells as well as inflammatory cytokines in the tumor microenvironment. Natural products tuning the tumor microenvironment via various mechanisms to activate the immune response have immeasurable potential for cancer immunotherapy. In this review, it highlights the research findings related to natural products regulating immune responses against cancer, especially reveals the possibility of utilizing natural products to remodel the tumor microenvironment to overcome drug resistance.

The Identification of APOBEC3G as a Potential Prognostic Biomarker in Acute Myeloid Leukemia and a Possible Drug Target for Crotonoside

The apolipoprotein B mRNA editing enzyme catalytic subunit 3G (APOBEC3G) converts cytosine to uracil in DNA/RNA. Its role in resisting viral invasion has been well documented. However, its expression pattern and potential function in AML remain unclear. In this study, we carried out a bioinformatics analysis and revealed that the expression of APOBEC3G was significantly upregulated in AML, and high expression of APOBEC3G was significantly associated with short overall survival (OS). APOBEC3G expression was especially increased in non-M3AML, and correlated with the unfavorable cytogenetic risks. Additionally, Cox regression analyses indicated APOBEC3G is a hazard factor that cannot be ignored for OS of AML patients. In molecular docking simulations, the natural product crotonoside was found to interact well with APOBEC3G. The expression of APOBEC3G is the highest in KG-1 cells, and the treatment with crotonoside can reduce the expression of APOBEC3G. Crotonoside can inhibit the viability of different AML cells in vitro, arrest KG-1 and MV-4-11 cells in the S phase of the cell cycle and affect the expression of cycle-related proteins, and induce cell apoptosis. Therefore, APOBEC3G could be a potential drug target of crotonoside, and crotonoside can be considered as a lead compound for APOBEC3G inhibition in non-M3 AML.

Dietary polyphenols in chemoprevention and synergistic effect in cancer: Clinical evidences and molecular mechanisms of action

BACKGROUND

Epidemiological studies has revealed that a diet rich in fruits and vegetables could lower the risk of certain cancers. In this setting, natural polyphenols are potent anticancer bioactive compounds to overcome the non-target specificity, undesirable cytotoxicity and high cost of treatment cancer chemotherapy.

PURPOSE

The review focuses on diverse classifications of the chemical diversity of dietary polyphenol and their molecular targets, modes of action, as well as preclinical and clinical applications in cancer prevention.

RESULTS

The dietary polyphenols exhibit chemo-preventive activity through modulation of apoptosis, autophagy, cell cycle progression, inflammation, invasion and metastasis. Polyphenols possess strong antioxidant activity and control multiple molecular events through activation of tumor suppressor genes and inhibition of oncogenes involved in carcinogenesis. Numerous in vitro and in vivo studies have evidenced that these dietary phytochemicals regulate critical molecular targets and pathways to limit cancer initiation and progression. Moreover, natural polyphenols act synergistically with existing clinically approved drugs. The improved anticancer activity of combinations of polyphenols and anticancer drugs represents a promising perspective for clinical applications against many human cancers.

CONCLUSION

The anticancer properties exhibited by dietary polyphenols are mainly attributed to their anti-metastatic, anti-proliferative, anti-angiogenic, anti-inflammatory, cell cycle arrest, apoptotic and autophagic effects. Hence, regular consumption of dietary polyphenols as food or food additives or adjuvants can be a promising tactic to preclude adjournment or cancer therapy.

The multifaceted NF-kB: are there still prospects of its inhibition for clinical intervention in pediatric central nervous system tumors?

Despite advances in the understanding of the molecular mechanisms underlying the basic biology and pathogenesis of pediatric central nervous system (CNS) malignancies, patients still have an extremely unfavorable prognosis. Over the years, a plethora of natural and synthetic compounds has emerged for the pharmacologic intervention of the NF-kB pathway, one of the most frequently dysregulated signaling cascades in human cancer with key roles in cell growth, survival, and therapy resistance. Here, we provide a review about the state-of-the-art concerning the dysregulation of this hub transcription factor in the most prevalent pediatric CNS tumors: glioma, medulloblastoma, and ependymoma. Moreover, we compile the available literature on the anti-proliferative effects of varied NF-kB inhibitors acting alone or in combination with other therapies in vitro, in vivo, and clinical trials. As the wealth of basic research data continues to accumulate, recognizing NF-kB as a therapeutic target may provide important insights to treat these diseases, hopefully contributing to increase cure rates and lower side effects related to therapy.

Resveratrol for targeting the tumor microenvironment and its interactions with cancer cells

Tumor resistance to therapy modalities is one of the major challenges to the eradication of cancer cells and complete treatment. Tumor includes a wide range of cancer and non-cancer cells that play key roles in the proliferation of cancer cells and suppression of anti-tumor immunity. For overcoming tumor resistance to therapy, it is important to have in-depth knowledge relating to intercellular communications within the tumor microenvironment (TME). TME includes various types of immune cells such as CD4 + T lymphocytes, cytotoxic T lymphocytes (CTLs), natural killer (NK) cells, macrophages, and T regulatory cells (Tregs). Furthermore, some non-immune cells like cancer stem cells (CSCs), mesenchymal stem cells (MSCs), and cancer-associated fibroblasts (CAFs) are involved in the promotion of tumor growth. The interactions between these cells with cancer cells play a key role in tumor growth or inhibition. Resveratrol as a natural agent has shown the ability to modulate the immune system to potentiate anti-tumor immunity and also help to attenuate cancer cells and CSCs resistance. Thus, this review explains how resveratrol can modulate interactions within TME.

C-Myc Signaling Pathway in Treatment and Prevention of Brain Tumors

Brain tumors are responsible for high morbidity and mortality worldwide. Several factors such as the presence of blood-brain barrier (BBB), sensitive location in the brain, and unique biological features challenge the treatment of brain tumors. The conventional drugs are no longer effective in the treatment of brain tumors, and scientists are trying to find novel therapeutics for brain tumors. In this way, identification of molecular pathways can facilitate finding an effective treatment. c-Myc is an oncogene signaling pathway capable of regulation of biological processes such as apoptotic cell death, proliferation, survival, differentiation, and so on. These pleiotropic effects of c-Myc have resulted in much fascination with its role in different cancers, particularly brain tumors. In the present review, we aim to demonstrate the upstream and down-stream mediators of c-Myc in brain tumors such as glioma, glioblastoma, astrocytoma, and medulloblastoma. The capacity of c-Myc as a prognostic factor in brain tumors will be investigated. Our goal is to define an axis in which the c-Myc signaling pathway plays a crucial role and to provide direction for therapeutic targeting in these signaling networks in brain tumors.

Participation of MicroRNAs in the Treatment of Cancer with Phytochemicals

Cancer is a global health concern and one of the main causes of disease-related death. Even with considerable progress in investigations on cancer therapy, effective anti-cancer agents and regimens have thus far been insufficient. There has been compelling evidence that natural phytochemicals and their derivatives have potent anti-cancer activities. Plant-based anti-cancer agents, such as etoposide, irinotecan, paclitaxel, and vincristine, are currently being applied in medical treatments for patients with cancer. Further, the efficacy of plenty of phytochemicals has been evaluated to discover a promising candidate for cancer therapy. For developing more effective cancer therapy, it is required to apprehend the molecular mechanism deployed by natural compounds. MicroRNAs (miRNAs) have been realized to play a pivotal role in regulating cellular signaling pathways, affecting the efficacy of therapeutic agents in cancer. This review presents a feature of phytochemicals with anti-cancer activity, focusing mainly on the relationship between phytochemicals and miRNAs, with insights into the role of miRNAs as the mediators and the regulators of anti-cancer effects of phytochemicals.

Toxicity of TiO2 Nanoparticles: Validation of Alternative Models

There are many studies concerning titanium dioxide (TiO₂) nanoparticles (NP) toxicity. Nevertheless, there are few publications comparing in vitro and in vivo exposure, and even less comparing air–liquid interface exposure (ALI) with other in vitro and in vivo exposures. The identification and validation of common markers under different exposure conditions are relevant for the development of smart and quick nanotoxicity tests. In this work, cell viability was assessed in vitro by WST-1 and LDH assays after the exposure of NR8383 cells to TiO₂ NP sample. To evaluate in vitro gene expression profile, NR8383 cells were exposed to TiO₂ NP during 4 h at 3 cm² of TiO₂ NP/cm² of cells or 19 μg/mL, in two settings—submerged cultures and ALI. For the in vivo study, Fischer 344 rats were exposed by inhalation to a nanostructured aerosol at a concentration of 10 mg/m³, 6 h/day, 5 days/week for 4 weeks. This was followed immediately by gene expression analysis. The results showed a low cytotoxic potential of TiO₂ NP on NR8383 cells. Despite the absence of toxicity at the doses studied, the different exposures to TiO₂ NP induce 18 common differentially expressed genes (DEG) which are involved in mitosis regulation, cell proliferation and apoptosis and inflammation transport of membrane proteins. Among these genes, we noticed the upregulation of Ccl4, Osm, Ccl7 and Bcl3 genes which could be suggested as early response biomarkers after exposure to TiO₂ NP. On the other hand, the comparison of the three models helped us to validate the alternative ones, namely submerged and ALI approaches.

Resveratrol attenuates diabetes-associated cell centrosome amplification via inhibiting the PKCα-p38 to c-myc/c-jun pathway

Type 2 diabetes increases the risk for cancer. Centrosome amplification can initiate tumorigenesis. We have described that type 2 diabetes increases the centrosome amplification of peripheral blood mononuclear cells, with high glucose, insulin, and palmitic acid as the triggers, which suggests that centrosome amplification is a candidate biological mechanism linking diabetes to cancer. In this study, we aimed to further investigate the signaling pathways of the diabetes-associated centrosome amplification and to examine whether and how resveratrol inhibits the centrosome amplification. The results showed that treatment with high glucose, insulin, and palmitic acid, alone or in combination, could increase the protein levels of phospho-protein kinase C alpha (p-PKCα), phospho-p38 mitogen-activated protein kinases (p-p38), c-myc, and c-jun, as well as the mRNA levels of c-myc and c-jun. PKCα inhibitor could inhibit the treatment-induced increase in the protein levels of p-p38, c-myc, and c-jun. Inhibitor or siRNA of p38 was also able to inhibit the treatment-induced increase in the levels of p-p38, c-myc, and c-jun. Meanwhile, knockdown of c-myc or c-jun did not alter the treatment-induced increase in the phosphorylation of PKCα or p38. Importantly, inhibition of the phosphorylation of PKCα or p38 and knockdown of c-myc or c-jun could attenuate the centrosome amplification. In diabetic mice, the levels of p-PKCα, p-p38, c-myc, and c-jun were all increased in the colon tissues. Interestingly, resveratrol, but not metformin, was able to attenuate the treatment-induced increase in the levels of p-PKCα, p-p38, c-myc, and c-jun, as well as the centrosome amplification. In conclusion, our results suggest that PKCα-p38 to c-myc/c-jun is the signaling pathway of the diabetes-associated centrosome amplification, and resveratrol attenuates the centrosome amplification by inhibiting this signaling pathway.

Dose-dependent short- and long-term effects of ionizing irradiation on neural stem cells in murine hippocampal tissue cultures: neuroprotective potential of resveratrol

INTRODUCTION

Radiation therapy plays an essential role in the treatment of brain tumors, but neurocognitive deficits remain a significant risk, especially in pediatric patients. In recent trials, hippocampal sparing techniques are applied to reduce these adverse effects. Here, we investigate dose-dependent effects of ionizing radiation (IR) on juvenile hippocampal neurogenesis. Additionally, we evaluate the radioprotective potential of resveratrol, a plant polyphenol recognized for its bifunctional tumor-preventive and anticancer effects.

METHODS

Organotypic entorhinal-hippocampal slice cultures from transgenic nestin-CFPnuc C57BL/J6 mice, postnatal days 3-6, were irradiated on a X-ray machine (4.5, 8, 12, and 16 Gy, single doses) after about 2 weeks. Nestin-positive neural stem cells were counted at a confocal live imaging microscope 0, 2, 4, 14, 25, and 42 days after IR. Resveratrol (15 μmol/L) was added 2 hr before and 24 hr after IR. Proliferation and cell death were assessed by BrdU pulse label, 48 hr after and by propidium iodide staining 96 hr after IR. GFAP- and NeuN-positive cells were counted 42 days after IR in cryosectioned immunofluorescence-stained slices.

RESULTS

The observed age-related changes of nestin-positive stem cells in the organotypic slice culture model resembled the reduction of neural stem cells in vivo. IR (4.5-16 Gy) led to a dose-dependent damage of the neural stem cell pool in the dentate gyrus. No recovery was seen within 42 days after doses from 4.5 Gy onward. The decline of nestin-positive cells was paralleled by increased cell death and decreased proliferation. The number of GFAP-positive cells was significantly enhanced. No significant change was detected in the overall NeuN-positive cell population, whereas the number of newborn, NeuN/BrdU double-positive neurons was reduced. Resveratrol treatment reversed the irradiation-induced decline of neural stem cells.

CONCLUSION

The neuroprotective action of resveratrol on irradiated hippocampal tissue warrants further investigation as a possible supplement to hippocampal sparing procedures.

Enhanced inhibition of clonogenic survival of human medulloblastoma cells by multimodal treatment with ionizing irradiation, epigenetic modifiers, and differentiation-inducing drugs

Background

Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis.

Methods

In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2′-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start.

Results

All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures.

Conclusion

In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.

Calmidazolium chloride inhibits growth of murine embryonal carcinoma cells, a model of cancer stem-like cells

Calmidazolium chloride (CMZ) is widely used as a calmodulin (CaM) antagonist, but is also known to induce apoptosis in certain cancer cell lines. However, in spite of the importance of cancer stem cells (CSCs) in cancer therapy, the effects of CMZ on CSCs are not yet well understood. We investigated the effects of CMZ on the F9 embryonal carcinoma cell (ECC) line as a surrogate model of CSCs. To avoid bias due to culture conditions, F9 ECCs and E14 embryonic stem cells (ESCs) were grown in the same culture medium. Results obtained using a cell-counting kit showed that CMZ significantly inhibited growth in F9 ECCs compared with growth in E14 ESCs. CMZ also induced apoptosis of F9 ECCs, but not of E14 ESCs, which was associated with caspase-3 activation and an increased fraction of the sub-G1 cell population. In addition, our data revealed that the expression of stemness-related genes including c-Myc was selectively down regulated in CMZ-treated F9 ECCs. Our results suggest that CMZ can inhibit the growth of ECCs by inducing apoptosis and down regulating stemness-related genes, without causing any harm to normal stem cells. These findings indicate a potential application of CMZ in the development of anti-CSC therapeutics.

Inhibition of STAT3 signaling as critical molecular event in resveratrol-suppressed ovarian cancer cells

Background

Resveratrol exerts inhibitory effects on ovarian cancer cells, while its underlying mechanism and critical molecular target(s) have been lesser known. Activations of Wnt, Notch and STAT3 signaling are frequent in ovarian cancers/OCs and supposed to be important for OC formation and progression, while the impacts of resveratrol on these signaling pathways in OC cells remain obscure.

Methods

In this study, two human ovarian cancer cell lines, OVCAR-3 and CAOV-3, were treated by 120 μM resveratrol and their responses to the treatment and the statuses of Wnt, Notch and STAT3 signaling in them were analyzed by multiple experimental approaches. Selective inhibitors of Wnt, Notch or STAT3 signaling were employed to treat OVCAR-3 and CAOV-3 cells to elucidate the significance of individual signaling pathways for ovarian cancers.

Results

The results demonstrated distinct inhibitory effects of resveratrol on human ovarian cancer cells in terms of remarkable G1 phase accumulation, increased apoptosis fraction and concurrent suppression of Wnt, Notch and STAT3 signaling as well as their downstream cancer-related gene expression. Treatments with Wnt, Notch or STAT3 selective inhibitor revealed that only AG490, a JAK-specific inhibitor, inhibits OVCAR-3 and CAOV-3 cells in the extent as similar as that of resveratrol.

Conclusion

Our results suggest the significance of STAT3 activation in the maintenance and survival of ovarian cancer cells. The activated STAT3 signaling is the critical molecular target of resveratrol. Resveratrol would be a promising candidate in the management of ovarian cancers, especially the ones with resistance to conventional therapeutic agents.

Resveratrol analogue (E)-8-acetoxy-2-[2-(3,4-diacetoxyphenyl)ethenyl]-quinazoline induces G₂/M cell cycle arrest through the activation of ATM/ATR in human cervical carcinoma HeLa cells

Styrylquinazolines are synthetic analogues of resveratrol and have been suggested to cause anti-inflammatory activity by modulating prostaglandin E₂ (PGE₂) production. In the present study, we evaluated cytotoxic effects of various styrylquinazoline derivatives and found that (E)-8-acetoxy-2-[2-(3,4-diacetoxyphenyl)ethenyl]-quinazoline (8-ADEQ) most potently inhibited the proliferation of the human cervical carcinoma HeLa cells. Exploring the growth-inhibitory mechanisms of 8-ADEQ, we found that it causes a cell cycle arrest at the G₂/M phase by DNA flow cytometric analysis, which was accompanied by upregulation of cyclin B1 expression and cyclin-dependent protein kinase 1 (Cdk1) phosphorylation. In addition, we observed that 8-ADEQ causes phosphorylation of the cell division cycle 25C (Cdc25C) protein through the activation of checkpoint kinases 1 (Chk1) and Chk2, which in turn were activated via ataxia telangiectasia mutated (ATM)/ataxia telangiectasia-Rad3-related (ATR) kinases in response to the DNA damage. Furthermore, ATM/ATR inhibitor caffeine, p53- or ATM/ATR-specific siRNA significantly attenuated 8-ADEQ-induced G₂/M arrest. These results suggest that the 8-ADEQ inhibits the proliferation of human cervical cancer HeLa cells by DNA damage-mediated G₂/M cell cycle arrest. 8-ADEQ‑induced G₂/M arrest is mediated by the activation of both Chk1/2-Cdc25 and p53-p21CIP1/WAF1 via ATM/ATR pathway, and indicates that 8-ADEQ appears to have potential in the treatment of cervical cancer.

Protein arginine methyltransferase 5 is a key regulator of the MYCN oncoprotein in neuroblastoma cells

Approximately half of poor prognosis neuroblastomas (NBs) are characterized by pathognomonic MYCN gene amplification and MYCN over-expression. Here we present data showing that short-interfering RNA mediated depletion of the protein arginine methyltransferase 5 (PRMT5) in cell-lines representative of NBs with MYCN gene amplification leads to greatly impaired growth and apoptosis. Growth suppression is not apparent in the MYCN-negative SH-SY5Y NB cell-line, or in two immortalized human fibroblast cell-lines. Immunoblotting of NB cell-lines shows that high PRMT5 expression is strongly associated with MYCN-amplification (P < 0.004, Mann-Whitney U-test) and immunohistochemical analysis of primary NBs reveals that whilst PRMT5 protein is ubiquitously expressed in the cytoplasm of most cells, MYCN-amplified tumours exhibit pronounced nuclear PRMT5 staining. PRMT5 knockdown in MYCN-overexpressing cells, including the SHEP-21N cell-line with inducible MYCN expression leads to a dramatic decrease in MYCN protein and MYCN-associated cell-death in SHEP-21N cells. Quantitative gene expression analysis and cycloheximide chase experiments suggest that PRMT5 regulates MYCN at a post-transcriptional level. Reciprocal co-immunoprecipitation experiments demonstrated that endogenous PRMT5 and MYCN interact in both SK-N-BE(2)C and NGP cell lines. By using liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis of immunoprecipitated MYCN protein, we identified several potential sites of arginine dimethylation on the MYCN protein. Together our studies implicate PRMT5 in a novel mode of MYCN post-translational regulation and suggest PRMT5 plays a major role in NB tumorigenesis. Small-molecule inhibitors of PRMT5 may therefore represent a novel therapeutic strategy for neuroblastoma and other cancers driven by the MYCN oncogene.

Alteration of splice site selection in the LMNA gene and inhibition of progerin production via AMPK activation

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare genetic condition characterized by an accelerated aging phenotype and an average life span of 13years. Patients typically exhibit extensive pathophysiological vascular alterations, eventually resulting in death from stroke or myocardial infarction. A silent point mutation at position 1824 (C1824T) of the LMNA gene, generating a truncated form of lamin A (progerin), has been shown to be the cause of most cases of HGPS. Interestingly, this mutation induces the use of an internal 5' cryptic splice site within exon 11 of the LMNA pre-mRNA, leading to the generation of progerin via aberrant alternative splicing. The serine-arginine rich splicing factor 1 (SRSF1 or ASF/SF2) has been shown to function as an oncoprotein and is upregulated in many cancers and other age-related disorders. Indeed, SRSF1 inhibition results in a splicing ratio in the LMNA pre-mRNA favoring lamin A production over that of progerin. It is our hypothesis that activation of AMP-activated protein kinase (AMPK), a master regulator of cellular metabolism, may lead to a reduction in SRSF1 and thus a decrease in the use of the LMNA 5' cryptic splice site in exon 11 through upregulation of p32, a splicing factor-associated protein and putative mitochondrial chaperone that has been shown to inhibit SRSF1 and enhance mitochondrial DNA (mtDNA) replication and oxidative phosphorylation. AMPK activation by currently available compounds such as metformin, resveratrol, and berberine may thus have wide-ranging implications for disorders associated with increased production and accumulation of progerin.

Cytotoxic effects of pyrrolidine dithiocarbamate in small-cell lung cancer cells, alone and in combination with cisplatin

The cytocidal effect of pyrrolidine dithiocarbamate (PDTC) was investigated by focusing on cell viability, cell cycle arrest and apoptosis induction in small-cell lung cancer (SCLC) cell lines (NCI-H196 and NCI-H889). PDTC exhibited a much stronger dose-dependent cytotoxic activity against NCI-H196 compared to NCI-H889, while no such activity was observed in normal human embryonal lung fibroblast MRC-5 cells. Cell cycle arrest in S phase paralleled with suppression of c-myc expression without accompanying DNA fragmentation was observed in NCI-H196 cells. A transient increase in the intracellular ROS accompanied with an alteration of expression of oxidative stress-related genes was also confirmed in NCI-H196 cells. Furthermore, the addition of N-acetyl-l-cysteine (NAC), a free radical scavenger, not only abolished PDTC-trigger alterations of expression of these oxidative-related genes, but also almost completely abrogated PDTC-induced reduction in cell viability and morphological changes associated with cell damage. These results thus suggest that PDTC-induced cytotoxicity is attributed to its pro-oxidant activity. PDTC-induced cytotoxicity was further enhanced by CuCl2, however, abolished by bathocuproine disulfonate (BCPS), a non-permeable copper-specific chelator, supporting the plausibility that accumulation of intracellular Cu plays an important role in the cytotoxicity. Importantly, we demonstrated for the first time that PDTC downregulated the expression of ATP7A, known to be responsible for Cu efflux, but did not affect the expression of CTR1, known as a copper uptake transporter. Intriguingly, combination of much lower dose of cisplatin (5 µM) and non-toxic dose of PDTC (0.1 µM) synergistically induced a significant cytotoxicity in NCI-H196 cells. Given that ATP7A plays a critical role in the resistance of platinum-drug (such as cisplatin) representing a first-line treatment for SCLC, PDTC could be a promising candidate of adjunct therapeutic reagent for the patients requiring treatment with platinum-based regimens.

Biological significance and therapeutic implication of resveratrol-inhibited Wnt, Notch and STAT3 signaling in cervical cancer cells

Cervical cancers/CCs are one of the commonest malignancies and the second leading cause of cancer-related death in women. Resveratrol inhibits CC cell growth but its molecular target(s) remains unclear. Since the signaling pathways mediated by STAT3, Notch1 and Wnt2 play beneficial roles in CC formation and progression, the effects of resveratrol on them in cervical adenocarcinoma (HeLa) and squamous cell carcinoma (SiHa) cells were analyzed. The biological significances of the above signaling for HeLa and SiHa cells were evaluated by treating the cells with STAT3, Wnt or Notch selective inhibitors. The frequencies of STAT3, Notch and Wnt activations in 68 cases of CC specimens and 38 non-cancerous cervical epithelia were examined by tissue microarray-based immunohistochemical staining. The results revealed that HeLa and SiHa cells treated by 100μM resveratrol showed extensive apoptosis, accompanied with suppression of STAT3, Notch and Wnt activations. Growth inhibition and apoptosis were found in HeLa and SiHa populations treated by AG490, a STAT3/JAK3 inhibitor but not the ones treated by Notch inhibitor L-685,458 or by Wnt inhibitor XAV-939. Immunohistochemical staining performed on the tissue microarrays showed that the frequencies of Notch1, Notch2, Hes1, Wnt2, Wnt5a and p-STAT3 detection as well as β-catenin nuclear translocation in CC samples were significantly higher than that of noncancerous group (p<0.01), while the expression rate of PIAS3 was remarkably low in cancer samples (p<0.01). Our results thus demonstrate that STAT3, Wnt and Notch signaling are frequently co-activated in human CC cells and specimens and resveratrol can concurrently inhibit those signaling activations and meanwhile lead cervical squamous cell carcinoma and adenocarcinoma cells to growth arrest and apoptosis. STAT3 signaling is more critical for CC cells and is the major target of resveratrol because selective inhibition of STAT3 rather than Wnt or Notch activation commits SiHa and HeLa cells to apoptosis.

G-quadruplexes as potential therapeutic targets for embryonal tumors

Embryonal tumors include a heterogeneous group of highly malignant neoplasms that primarily affect infants and children and are characterized by a high rate of mortality and treatment-related morbidity, hence improved therapies are clearly needed. G-quadruplexes are special secondary structures adopted in guanine (G)-rich DNA sequences that are often present in biologically important regions, e.g. at the end of telomeres and in the regulatory regions of oncogenes such as MYC. Owing to the significant roles that both telomeres and MYC play in cancer cell biology, G-quadruplexes have been viewed as emerging therapeutic targets in oncology and as tools for novel anticancer drug design. Several compounds that target these structures have shown promising anticancer activity in tumor xenograft models and some of them have entered Phase II clinical trials. In this review we examine approaches to DNA targeted cancer therapy, summarize the recent developments of G-quadruplex ligands as anticancer drugs and speculate on the future direction of such structures as a potential novel therapeutic strategy for embryonal tumors of the nervous system.

Evaluation of resveratrol sensitivities and metabolic patterns in human and rat glioblastoma cells

PURPOSE

To further elucidate the correlation of resveratrol sensitivities with biotransformation activities of human and rat glioblastoma cells for personalized anti-glioblastoma therapy.

METHODS

Resveratrol sensitivity of human U251 and rat RG2 and C6 glioblastoma cells was evaluated by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide/MTT, flow cytometry, and TUNEL assays. The metabolic patterns of those cell lines were analyzed by high-performance liquid chromatography/HPLC coupled with tandem mass spectrum/MS/MS, and high-resolution mass spectrometry/HRMS. Immunocytochemical staining and Western blotting were employed to check resveratrol metabolic enzyme expression.

RESULTS

Both rat RG2 and C6 and human U251 glioblastoma cells are sensitive to 100 μM resveratrol in terms of growth arrest and increased apoptotic fraction. The main resveratrol metabolite in U251 cells is monosulfate biotransformed by sulfotransferases/SULTs and in RG2 and C6 cells is monoglucuronide generated by UDP-glucuronosyltransferase/UGT. Both metabolites show lesser therapeutic efficacy. Although brain-associated UGTs (UGT1A6, 2B7, and 8) and SULTs (SULT1A1, 1C2, and 4A1) are expressed in rat and human glioma cells, the overall level of UGTs is predominant in the rat and SULTs in human glioblastoma cells. In similar to SULT expression pattern, UGT1A6, 2B7, and 8 are frequently downregulated (84.6 %, 82/97; 90.7 %, 88/97; 80.4 %, 78/97) in human glioblastoma tissues.

CONCLUSION

Our results suggest (1) the decreased resveratrol biotransforming activity in rat and human resveratrol-sensitive glioblastoma cells; (2) the discrepant resveratrol metabolic patterns between human and rat glioblastoma cells; (3) the more powerful anti-glioblastoma efficacy of trans-resveratrol rather than resveratrol monoglucuronide or monosulfate; and (4) the value of RG2 and C6 cells in establishing resveratrol-based rat in vivo therapeutic model.

Inhibitory effects of epigenetic modulators and differentiation inducers on human medulloblastoma cell lines

Background

Medulloblastoma (MB) is the most common malignant brain tumor in childhood with a 5-year survival of approximately 60%. We have recently shown that treatment of human MB cells with 5-aza-2’-deoxycytidine (5-aza-dC) reduces the clonogenic survival significantly. Here, we tested combinatorial effects of 5-aza-dC with other epigenetic (valproic acid, SAHA) and differentiation-inducing drugs (resveratrol, abacavir, retinoic acid) on human MB cells in vitro to intensify the antitumor therapy further.

Methods

Three human MB cell lines were treated with 5-aza-dC alone or in combination for three or six days. Metabolic activity was measured by WST-1 assay. To determine long-term reproductive survival, clonogenic assays were performed. Induction of DNA double-strand break (DSB) repair was measured by γH2AX assay.

Results

The applied single drugs, except for ATRA, reduced the metabolic activity dose-dependently in all MB cell lines. Longer treatment times enhanced the reduction of metabolic activity by 5-aza-dC. Combinatorial treatments showed differential, cell line-dependent responses indicating an important impact of the genetic background. 5-Aza-dC together with resveratrol was found to exert the most significant inhibitory effects on metabolic activity in all cell lines. 5-aza-dC alone reduced the clonogenicity of MB cells significantly and induced DSB with no further changes after adjuvant administration of resveratrol.

Conclusion

The observed significant decrease in metabolic activity by combinatorial treatment of MB cells with 5-aza-dC and resveratrol does not translate into long-term reproductive survival deficiency in vitro. Further studies in animal models are needed to clarify the resveratrol-mediated anticancer mechanisms in vivo.

Resveratrol abrogates the temozolomide-induced G2 arrest leading to mitotic catastrophe and reinforces the temozolomide-induced senescence in glioma cells

Background

Temozolomide (TMZ) is the most widely used drug to treat glioblastoma (GBM), which is the most common and aggressive primary tumor of the Central Nervous System and one of the hardest challenges in oncotherapy. TMZ is an alkylating agent that induces autophagy, apoptosis and senescence in GBM cells. However, therapy with TMZ increases survival after diagnosis only from 12 to 14.4 months, making the development of combined therapies to treat GBM fundamental. One candidate for GBM therapy is Resveratrol (Rsv), which has additive toxicity with TMZ in several glioma cells in vitro and in vivo. However, the mechanism of Rsv and TMZ additive toxicity, which is the aim of the present work, is not clear, especially concerning cell cycle dynamics and long term effects.

Methods

Glioma cell lines were treated with Rsv and TMZ, alone or in combinations, and the induction and the role of autophagy, apoptosis, cell cycle dynamics, protein expression and phosphorylation status were measured. We further evaluated the long term senescence induction and clonogenic capacity.

Results

As expected, temozolomide caused a G2 cell cycle arrest and extensive DNA damage response. Rsv did not reduced this response, even increasing pATM, pChk2 and gammaH2Ax levels, but abrogated the temozolomide-induced G2 arrest, increasing levels of cyclin B and pRb(S807/811) and reducing levels of pWee1(S642) and pCdk1(Y15). This suggests a cellular state of forced passage through G2 checkpoint despite large DNA damage, a scenario that may produce mitotic catastrophe. Indeed, the proportion of cells with high nuclear irregularity increased from 6 to 26% in 48 h after cotreatment. At a long term, a reduction in clonogenic capacity was observed, accompanied by a large induction of senescence.

Conclusion

The presence of Rsv forces cells treated with TMZ through mitosis leading to mitotic catastrophe and senescence, reducing the clonogenic capacity of glioma cells and increasing the chronic effects of temozolomide.

Role of RANTES and its receptor in gastric cancer metastasis

This study examined the role of regulated upon activation normal T cell expressed and secreted (RANTES) and its receptor C-C chemokine receptor type 5 (CCR5) in gastric cancer metastasis and the associated mechanism. The expression of RANTES and CCR5 was detected by using immunohistochemical staining and Western blotting in the gastric cancer tissues obtained from 60 gastric cancer patients with or without lymph node metastasis (n=30 in each). The results showed that the expression levels of RANTES and CCR5 were higher in gastric cancer with lymph node metastasis than in that without metastasis (P<0.05). The expression levels of RANTES in 30 lymph nodes with cancerous invasion were higher than in 30 normal lymph nodes (P<0.05). Chemotactic test revealed that the number of migrating gastric cancer cells (n=295.0 ± 54.6) induced by the protein of cancer-invading lymph nodes was greater than that by the protein mixture from cancer-invading lymph nodes and RANTES antibody (n=42.5 ± 11.6) (P<0.05). RT-PCR showed that the expression levels of the main Th1 cytokines (IL-2, Γ-IFN) were lower in gastric cancer with lymph node metastasis (2.22 ± 0.90, 3.26 ± 1.15 respectively) than in that without metastasis (3.07 ± 1.67, 4.77 ± 1.52 respectively) (P<0.05), but the expression level of the main Th 2 cytokine (IL-10) was higher in gastric cancer with lymph nodes metastasis (6.06 ± 2.04) than in that without metastasis (4.88 ± 1.87) (P<0.05). It was concluded that RANTES and its receptor CCR5 may contribute to gastric cancer metastasis through influencing the balance of Th1/Th2. RANTES and CCR5 may become a marker of gastric cancer metastasis.

c-MYC expression sensitizes medulloblastoma cells to radio- and chemotherapy and has no impact on response in medulloblastoma patients

Background

To study whether and how c-MYC expression determines response to radio- and chemotherapy in childhood medulloblastoma (MB).

Methods

We used DAOY and UW228 human MB cells engineered to stably express different levels of c-MYC, and tested whether c-MYC expression has an effect on radio- and chemosensitivity using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay, clonogenic survival, apoptosis assays, cell cycle analysis, and western blot assessment. In an effort to validate our results, we analyzed c-MYC mRNA expression in formalin-fixed paraffin-embedded tumor samples from well-documented patients with postoperative residual tumor and compared c-MYC mRNA expression with response to radio- and chemotherapy as examined by neuroradiological imaging.

Results

In DAOY - and to a lesser extent in UW228 - cells expressing high levels of c-MYC, the cytotoxicity of cisplatin, and etoposide was significantly higher when compared with DAOY/UW228 cells expressing low levels of c-MYC. Irradiation- and chemotherapy-induced apoptotic cell death was enhanced in DAOY cells expressing high levels of c-MYC. The response of 62 of 66 residual tumors was evaluable and response to postoperative radio- (14 responders (CR, PR) vs. 5 non-responders (SD, PD)) or chemotherapy (23 CR/PR vs. 20 SD/PD) was assessed. c-MYC mRNA expression was similar in primary MB samples of responders and non-responders (Mann-Whitney U test, p = 0.50, ratio 0.49, 95% CI 0.008-30.0 and p = 0.67, ratio 1.8, 95% CI 0.14-23.5, respectively).

Conclusions

c-MYC sensitizes MB cells to some anti-cancer treatments in vitro. As we failed to show evidence for such an effect on postoperative residual tumors when analyzed by imaging, additional investigations in xenografts and larger MB cohorts may help to define the exact function of c-MYC in modulating response to treatment.

Multifaceted approach to resveratrol bioactivity: Focus on antioxidant action, cell signaling and safety

Resveratrol (RVT) is a naturally occurring trihydroxy stilbene that displays a wide spectrum of physiological activity. Its ability to behave therapeutically as a component of red wine has attracted wide attention. The phenol acts as a protective agent involving various body constituents. Most attention has been given to beneficial effects in insults involving cancer, aging, cardiovascular system, inflammation and the central nervous system. One of the principal modes of action appears to be as antioxidant. Other mechanistic pathways entail cell signaling, apoptosis and gene expression. There is an intriguing dichotomy in relation to pro-oxidant property. Also discussed are metabolism, receptor binding, rationale for safety and suggestions for future work. This is the first comprehensive review of RVT based on a broad, unifying mechanism.

Identification of metabolic pattern and bioactive form of resveratrol in human medulloblastoma cells

Cancer preventive reagent trans-resveratrol is intracellularly biotransformed to different metabolites. However, it is still unclear whether trans-resveratrol exerts its biological effects directly or through its metabolite(s). This issue was addressed here by identifying the metabolic pattern and the bioactive form of resveratrol in a resveratrol-sensitive human medulloblastoma cell line, UW228-3. The cell lysates and condition media of UW228-3 cells with or without 100 microM resveratrol treatment were analyzed by HPLC and LC/MS which revealed (1) that resveratrol was chemically unstable and the spontaneous generation of cis-resveratrol reduced resveratrol's anti-medulloblastoma efficacy and (2) that resveratrol monosulfate was the major metabolite of the cells. To identify the bioactive form of resveratrol, a mixture-containing approximately half fraction of resveratrol monosulfate was prepared by incubating trans-resveratrol with freshly prepared rat brain lysates. Medulloblastoma cells treated by 100 microM of this mixture showed attenuated cell crisis. The overall levels of the three brain-associated sulfotransferases (SULT1A1, 1C2 and 4A1) were low in medulloblastoma cells in vivo and in vitro in comparison with that in human noncancerous and rat normal cerebella; resveratrol could more or less up-regulate the production of these enzymes in UW228-3 cells but their overall level was still lower than that in normal cerebellum tissue. Our study thus demonstrated for the first time that trans-resveratrol is the bioactive form in medulloblastoma cells in which the expression of brain-associated SULTs was down-regulated, resulting in the increased intracellular bioavailability and anti-medulloblastoma efficacy of trans-resveratrol.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Multiple molecular targets of resveratrol: Anti-carcinogenic mechanisms

Plant-derived polyphenolic compounds, such as the stilbene resveratrol (trans-3,4',5-trihydroxystilbene), have been identified as potent anti-cancer agents. Extensive in vitro studies revealed multiple intracellular targets of resveratrol, which affect cell growth, inflammation, apoptosis, angiogenesis, and invasion and metastasis. These include tumor suppressors p53 and Rb; cell cycle regulators, cyclins, CDKs, p21WAF1, p27KIP and INK and the checkpoint kinases ATM/ATR; transcription factors NF-kappaB, AP-1, c-Jun, and c-Fos; angiogenic and metastatic factors, VEGF and matrix metalloprotease 2/9; cyclooxygenases for inflammation; and apoptotic and survival regulators, Bax, Bak, PUMA, Noxa, TRAIL, APAF, survivin, Akt, Bcl2 and Bcl-X(L). In addition to its well-documented anti-oxidant properties, there is increasing evidence that resveratrol exhibits pro-oxidant activity under certain experimental conditions, causing oxidative DNA damage that may lead to cell cycle arrest or apoptosis. This review summarizes in vitro mechanistic data available for resveratrol and discusses new potential anti-cancer targets and the antiproliferative mechanisms of resveratrol.

MYC prevents apoptosis and enhances endoreduplication induced by paclitaxel

Background

The role of the MYC oncogene in the apoptotic pathways is not fully understood. MYC has been reported to protect cells from apoptosis activation but also to sensitize cells to apoptotic stimuli. We have previously demonstrated that the down-regulation of Myc protein activates apoptosis in melanoma cells and increases the susceptibility of cells to various antitumoral treatments. Beyond the well-known role in the G1→S transition, MYC is also involved in the G2-M cell cycle phases regulation.

Methodology/Principal Findings

In this study we have investigated how MYC could influence cell survival signalling during G2 and M phases. We used the microtubules damaging agent paclitaxel (PTX), to arrest the cells in the M phase, in a p53 mutated melanoma cell line with modulated Myc level and activity. An overexpression of Myc protein is able to increase endoreduplication favoring the survival of cells exposed to antimitotic poisoning. The PTX-induced endoreduplication is associated in Myc overexpressing cells with a reduced expression of MAD2, essential component of the molecular core of the spindle assembly checkpoint (SAC), indicating an impairment of this checkpoint. In addition, for the first time we have localized Myc protein at the spindle poles (centrosomes) during pro-metaphase in different cell lines.

Conclusions

The presence of Myc at the poles during the prometaphase could be necessary for the Myc-mediated attenuation of the SAC and the subsequent induction of endoreduplication. In addition, our data strongly suggest that the use of taxane in antitumor therapeutic strategies should be rationally based on the molecular profile of the individual tumor by specifically analyzing Myc expression levels.

RNA interference-mediated c-MYC inhibition prevents cell growth and decreases sensitivity to radio- and chemotherapy in childhood medulloblastoma cells

BACKGROUND

With current treatment strategies, nearly half of all medulloblastoma (MB) patients die from progressive tumors. Accordingly, the identification of novel therapeutic strategies remains a major goal. Deregulation of c-MYC is evident in numerous human cancers. In MB, over-expression of c-MYC has been shown to cause anaplasia and correlate with unfavorable prognosis.

METHODS

To study the role of c-MYC in MB biology, we down-regulated c-MYC expression by using small interfering RNA (siRNA) and investigated changes in cellular proliferation, cell cycle analysis, apoptosis, telomere maintenance, and response to ionizing radiation (IR) and chemotherapeutics in a representative panel of human MB cell lines expressing different levels of c-MYC (DAOY wild-type, DAOY transfected with the empty vector, DAOY transfected with c-MYC, D341, and D425).

RESULTS

siRNA-mediated c-MYC down-regulation resulted in an inhibition of cellular proliferation and clonogenic growth, inhibition of G1-S phase cell cycle progression, and a decrease in human telomerase reverse transcriptase (hTERT) expression and telomerase activity. On the other hand, down-regulation of c-MYC reduced apoptosis and decreased the sensitivity of human MB cells to IR, cisplatin, and etoposide. This effect was more pronounced in DAOY cells expressing high levels of c-MYC when compared with DAOY wild-type or DAOY cells transfected with the empty vector.

CONCLUSION

In human MB cells, in addition to its roles in growth and proliferation, c-MYC is also a potent inducer of apoptosis. Therefore, targeting c-MYC might be of therapeutic benefit when used sequentially with chemo- and radiotherapy rather than concomitantly.

Epigenetic background of neuronal fate determination

The development of the central nervous system (CNS) starts from neural stem cells (NSCs). During this process, NSCs are specified in space- and time-related fashions, becoming spatially heterogeneous and generating a progressively restricted repertoire of cell types: neurons, astrocytes and oligodendrocytes. The processes of neurodevelopment are determined reciprocally by intrinsic and external factors which interface to program and re-program the profiling of fate-determination gene expression. Multiple signaling pathways act in a dynamic web mode to determine the fate of NSCs through modulating the activity of a distinct set of transcription factors which in turn trigger the transcription of neural fate-determination genes. Accumulating evidence reveals that during CNS development, multiple epigenetic factors regulate the activities of extracellular signaling and corresponding transcription factors in a coordinative manner, leading to the formation of a system with sophisticated structure and magic functions. This review aims to introduce recent advances in the epigenetic background of neural cell fate determination.

Inhibition of STAT3 expression and signaling in resveratrol-differentiated medulloblastoma cells

In this study, the potential influence of resveratrol (3,5,4'-trihydroxy-trans-stilbene) in signal transducer and activator of transcription 3 (STAT3) signaling of medulloblastoma cells was evaluated by checking the status of STAT3 signaling and its downstream gene expression in two medulloblastoma cell lines (UW228-2 and UW228-3) with and without resveratrol treatment. The results revealed that resveratrol induced neuronal differentiation of medulloblastoma cells. Signal transducer and activator of transcription 3 expression and phosphorylation were detected in normally cultured UW228-2 and UW228-3 cells that were apparently attenuated after resveratrol treatment. The expression of STAT3 downstream genes, survivin, cyclin D1, Cox-2, and c-Myc, was suppressed but Bcl-2 was enhanced by resveratrol. Meanwhile, the production and secretion of leukemia inhibitory factor, a STAT3 activator, became active in resveratrol-treated cells. To further ascertain the significance of STAT3 signaling for medulloblastoma cells, AG490, a selective inhibitor of STAT3 phosphorylation, was used to treat UW228-3 cells. Phosphorylation of STAT3 was inhibited by AG490 accompanied with growth suppression, differentiation-like changes, and down-regulation of survivin, cyclin D1, Cox-2, and c-Myc. Our data thus suggest the importance of STAT3 signaling in maintenance and survival of medulloblastoma cells. This signaling may be the major target of resveratrol. Enhanced leukemia inhibitory factor and Bcl-2 expressions in resveratrol-treated cells might reflect a compensatory response to the loss of STAT3 function.

Correlative analyses of notch signaling with resveratrol-induced differentiation and apoptosis of human medulloblastoma cells

Altered Notch signaling seems linked with medulloblastoma (MB) formation and resveratrol exhibits anti-medulloblastoma effects. However, the influence of resveratrol in Notch signaling of MB cells has not been described. This issue was addressed here by checking Notch1 and Notch2 statuses in three MB cell lines with and without resveratrol treatment. Notch1 and Notch2 were detected in the cytoplasm of three cell lines under normal condition, which were up-regulated by resveratrol along with differentiation, apoptosis and enhanced Hes1 nuclear translocation. Nevertheless, blockage of Notch enzymatic cleavage with gamma-seacretase inhibitors, DAPT and L-685,458, neither interrupted resveratrol-caused cellular events nor affected MB cell growth. These results demonstrate that Notch signaling has little relevance with resveratrol-induced differentiation and apoptosis and may not be a universal critical factor of MB cells.

Endothelin (ET)-1 and ET-3 promote expression of c-fos and c-jun in human choriocarcinoma via ET(B) receptor-mediated G(i)- and G(q)-pathways and MAP kinase activation

BACKGROUND AND PURPOSE

Endothelins (ETs) and their G protein-coupled receptors exert key physiological functions during normal and aberrant placental development. Trophoblast cells mediate the contact between the embryo and the mother, by establishing a transient organ, the placenta. Choriocarcinoma cells display many of the biochemical and morphological characteristics of in utero invasive trophoblast cells and may therefore be used as a suitable model to study epithelial tumour progression of foetal-derived cells.

EXPERIMENTAL APPROACH

The present study aimed at investigating ET receptor-mediated activation of the mitogen-activated protein kinase (MAPK) pathway in human choriocarcinoma.

KEY RESULTS

Both JAR and Jeg-3 choriocarcinoma cell lines expressed ET receptor subtype B (ET(B)) but not ET(A) receptor transcripts. ET(B) receptor engagement by ET-1 and ET-3 resulted in a similar time- and concentration-dependent phosphorylation of p42/44 MAPK, also known as extracellular regulated kinase 1/2. Using specific pharmacological antagonists/inhibitors, we showed that ET-1/-3-mediated signal transduction by the ET(B) receptor is transmitted via G(i)- and G(q)-dependent pathways through activation of the Src (G(i)) and protein kinase C (G(q)) axis that converge at Ras/Raf, leading to downstream activation of p42/44. On a functional level, ET(B) engagement and subsequent phosphorylation of p42/44 resulted in enhanced transcription of the immediate early response genes c-fos and c-jun, a process commonly assumed to be mediated by the ET(A) receptor, and increased cell growth and relative cell area.

CONCLUSIONS AND IMPLICATIONS

As human choriocarcinoma cells secrete ETs, pharmacological antagonism of ETs and/or ET(B) receptor-mediated signal transduction could represent a likely target therapy for choriocarcinoma.

Synthesis, chaperoning, and metabolism of proteins are regulated by NT-3/TrkC signaling in the medulloblastoma cell line DAOY

The human medulloblastoma cell line DAOY was transfected with Tropomyosin receptor kinase (TrkC), a marker for good prognostic outcome. Following TrkC-activation by its ligand neurotrophin-3, protein extracts from DAOY cells were run on 2DE with subsequent MALDI-TOF-TOF analysis and quantification in order to detect downstream effectors. Protein levels of translational, splicing, processing, chaperone, protein handling, and metabolism machineries were shown to depend on neurotrophin-3-induced TrkC activation probably representing pharmacological targets.

Expression of seven gastric cancer-associated genes and its relevance for Wnt, NF-kappaB and Stat3 signaling

The aim of the current study was to profile c-Myc, standard CD44 (CD44s), CD44v6, cyclin D1, survivin, MMP-7 and VEGF expression patterns in different gastric samples and to elucidate their relevance for Wnt, NF-kappaB and/or Stat3 activation using multiple experimental approaches. The results revealed that 87.1% (27/31) of gastric cancers and 8.7% (2/23) of noncancerous lesions (chronic gastritis and intestinal metaplasia) showed Wnt activation (Wnt(+)) that was closely related to the expression of the seven genes. Some Wnt(-) noncancerous lesions also expressed the above-mentioned genes, higher frequencies of survivin (7/8), VEGF (7/8), cyclin D1 (6/8) and c-Myc (5/8) but not CD44s (2/8), CD44v6 (3/8) and MMP-7 (2/8) being detected in the NF-kappaB(+) samples. Stat3 was activated in 37/54 gastric tissues, and in 3/4 VEGF, 4/6 c-Myc, 4/8 survivin, 2/4 MMP-7, 1/2 CD44v6, and 4/9 cyclin D1(+) but Wnt(-)/NF-kappaB(-) samples. These findings showed a close correlation in GCs between Wnt, NF-kappaB and Stat3 signaling and expression of the seven genes, the importance of NF-kappaB and Stat3 activation in regulating c-Myc, survivin, cyclin D1 and VEGF in noncancerous lesions, and the potential coordinative effects of these three signalings on GC formation presumably by promoting the transcription of their common target genes.