Trichosanthin suppresses HeLa cell proliferation through inhibition of the PKC/MAPK signaling pathway

Mechanisms of Xuefu Zhuyu Tang in the Treatment of Diabetic Erectile Dysfunction in Rats Through the Regulation of Vascular Endothelial Function by CaSR/PLC/PKC and MEK/ERK/RSK Pathways

Xuefu zhuyu Tang (XFZYT) is a classic formula used for promoting blood circulation and resolving blood stasis in Traditional Chinese Medicine. Clinical data have indicated that XFZYT plays a significant therapeutic role in diabetes-induced erectile dysfunction (DIED) disease, but the underlying mechanism remains elusive. Male Sprague-Dawley (SD) rats were randomly categorized into normal, model, and treatment groups. The diabetic rat model was established via intraperitoneal injection of streptozotocin. DIED rats were screened using apomorphine, and the number of erections was measured after 8 weeks of XFZYT treatment. Serum nitric oxide (NO) and endothelin-1 levels as well as penile tissue structure alterations were assessed by hematoxylin-eosin staining and electron microscopy. CaSR/PLC/PKC and MEK/ERK/RSK pathway-related proteins in the penile tissue were detected by western blotting (WB) analysis and polymerase chain reaction (PCR). Compared with the blank group, the model group rats showed a significant decrease in weight and erectile function. The pathological damage in the penile tissues of the model rats was indicated by a significantly decreased serum NO level and an increased endothelin-1 content. After treatment with XFZYT, the protein expression of CaSR, PLCβ1, PKCβ, MEK1, ERK1, and RSK1 in the penile tissue was significantly increased. Overall, the treatment group showed significant improvements in the evaluated indexes. In conclusion, this study revealed that XFZYT improves erectile function in diabetic rats, and the underlying mechanism might be linked with the regulation of CaSR/PLC/PKC and related molecules of the MEK/ERK/RSK pathway, which promotes the vascular endothelial diastolic effect.

Polypeptides from traditional Chinese medicine: Comprehensive review of perspective towards cancer management

Cancer has always been a focus of global attention, and the difficulty of treatment and poor prognosis have always plagued humanity. Conventional chemotherapeutics and treatment with synthetic disciplines will cause adverse side effects and drug resistance. Therefore, searching for a safe, valid, and clinically effective drug is necessary. At present, some natural compounds have proved to have the potential to fight cancer. Polypeptides obtained from traditional Chinese medicine are good anti-cancer ingredients. The anticancer activity has been fully demonstrated in vivo and in vitro. However, most of the functional studies on traditional Chinese medicine polypeptides are at the stage of basic experimental research, and fewer of them have been applied to clinical trials. Hence, this review mainly discusses the chemical structure, extraction, separation and purification methods, the anti-cancer mechanism, and structure-activity relationships of traditional Chinese medicine polypeptides. It provides theoretical support for strengthening the rapid separation and purification and the overall efficacy and mechanism of action, as well as the industrialization and clinical application of traditional Chinese medicine polypeptides.

Advances on Delivery of Cytotoxic Enzymes as Anticancer Agents

Cancer is one of the most serious human diseases, causing millions of deaths worldwide annually, and, therefore, it is one of the most investigated research disciplines. Developing efficient anticancer tools includes studying the effects of different natural enzymes of plant and microbial origin on tumor cells. The development of various smart delivery systems based on enzyme drugs has been conducted for more than two decades. Some of these delivery systems have been developed to the point that they have reached clinical stages, and a few have even found application in selected cancer treatments. Various biological, chemical, and physical approaches have been utilized to enhance their efficiencies by improving their delivery and targeting. In this paper, we review advanced delivery systems for enzyme drugs for use in cancer therapy. Their structure-based functions, mechanisms of action, fused forms with other peptides in terms of targeting and penetration, and other main results from in vivo and clinical studies of these advanced delivery systems are highlighted.

The use of miR122 and its target sequence in adeno-associated virus-mediated trichosanthin gene therapy

OBJECTIVE

Plant-derived cytotoxic transgene expression, such as trichosanthin (tcs), regulated by recombinant adeno-associated virus (rAAV) vector is a promising cancer gene therapy. However, the cytotoxic transgene can hamper the vector production in the rAAV producer cell line, human embryonic kidney (HEK293) cells. Here, we explored microRNA-122 (miR122) and its target sequence to limit the expression of the cytotoxic gene in the rAAV producer cells.

METHODS

A miR122 target (122T) sequence was incorporated into the 3' untranslated region of the tcs cDNA sequence. The firefly luciferase (fluc) transgene was used as an appropriate control. Cell line HEK293-mir122 was generated by the lentiviral vector-mediated genome integration of the mir122 gene in parental HEK293 cells. The effects of miR122 overexpression on cell growth, transgene expression, and rAAV production were determined.

RESULTS

The presence of 122T sequence significantly reduced transgene expression in the miR122-enriched Huh7 cell line (in vitro), fresh human hepatocytes (ex vivo), and mouse liver (in vivo). Also, the normal liver physiology was unaffected by delivery of 122T sequence by rAAV vectors. Compared with the parental cells, the miR122-overexpressing HEK293-mir122 cell line showed similar cell growth rate and expression of transgene without 122T, as well as the ability to produce liver-targeting rAAV vectors. Fascinatingly, the yield of rAAV vectors carrying the tcs-122T gene was increased by 77.7-fold in HEK293-mir122 cells. Moreover, the tcs-122T-containing rAAV vectors significantly reduced the proliferation of hepatocellular carcinoma cells without affecting the normal liver cells.

CONCLUSION

HEK293-mir122 cells along with the 122T sequence provide a potential tool to attenuate the cytotoxic transgene expression, such as tcs, during rAAV vector production.

Trichosanthin inhibits cervical cancer by regulating oxidative stress-induced apoptosis

Based on many studies, trichosanthin (TCS) has an antiviral effect that regulates immune response, and targets cancer cells to exert broad-spectrum anti-tumor pharmacological activities. It is speculated that TCS may be a potential natural active drug for preventing as well as treating cervical cancer. But the clearer impact along with underlying TCS mechanism on cervical cancer are still unclear. The purpose of this study is to investigate the function and potential mechanism of TCS in cervical cancer. We measured the viability of cervical cancer cell lines (HeLa & caski cells) using CCK-8 analysis, detected cell proliferation efficiency through Ki-67 staining, analyzed cell apoptosis rate via flow cytometry as well as annexin V-FITC/PI double staining, performed apoptosis-related protein expression through western blotting, evaluated cell migration along with invasion by wound as well as transwell assays, carried out MMP via JC-1 and Rh123 fluorescent probes, as well as detected intracellular ATP and ROS levels by flow cytometry, respectively, to evaluate the effects of TCS. We found that TCS inhibited viability along with proliferation, induced apoptosis, as well as inhibited HeLa & caski cell migration along with invasion in a time- and dose-dependent manner. Additionally, TCS also reduced MMP, and the production of adenosine triphosphate, as well as induced the increase of intracellular reactive oxygen species in cancer cell lines. In accordance with the present studies, TCS inhibits HeLa & caski cell proliferation along with migration but promotes their apoptosis, which may be mediated by regulating oxidative stress.

Mechanisms of oxidative stress in methylmercury-induced neurodevelopmental toxicity

Methylmercury (MeHg) is a long-lasting organic environmental pollutant that poses a great threat to human health. Ingestion of seafood containing MeHg is the most important way by which it comes into contact with human body, where the central nervous system (CNS) is the primary target of MeHg toxicity. During periods of pre-plus postnatal, in particular, the brain of offspring is vulnerable to specific developmental insults that result in abnormal neurobehavioral development, even without symptoms in mothers. While many studies on neurotoxic effects of MeHg on the developing brain have been conducted, the mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity is less clear. Hitherto, no single process can explain the many effects observed in MeHg-induced neurodevelopmental toxicity. This review summarizes the possible mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity, highlighting modulation of Nrf2/Keap1/Notch1, PI3K/AKT, and PKC/MAPK molecular pathways as well as some preventive drugs, and thus contributes to the discovery of endogenous and exogenous molecules that can counteract MeHg-induced neurodevelopmental toxicity.

Toxic proteins application in cancer therapy

Ribosome inactivating proteins (RIPs) as family of anti-cancer drugs recently received much attention due to their interesting anti-cancer mechanism. In spite of small drugs, RIPs use the large-size effect (LSE) to prevent the efflux process governed by drug resistance transporters (DRTs) which prevents inside of the cells against drug transfection. There are many clinical translation obstacles that severely restrict their applications especially their delivery approach to the tumor cells. As the main goal of this review, we will focus on trichosanthin (TCS) and gelonin (Gel) and other types, especially scorpion venom-derived RIPs to clarify that they are struggling with what types of bio-barriers and these challenges could be solved in cancer therapy science. Then, we will try to highlight recent state-of-the-arts in delivery of RIPs for cancer therapy.

Advances on Tumor-Targeting Delivery of Cytotoxic Proteins

Great attention has been paid to cytotoxic proteins (e.g., ribosome-inactivating proteins, RIPs) possessing high anticancer activities; unlike small drugs, cytotoxic proteins can effectively retain inside the cells and avoid drug efflux mediated by multidrug resistance transporters due to the large-size effect. However, the clinical translation of these proteins is severely limited because of various biobarriers that hamper their effective delivery to tumor cells. Hence, in order to overcome these barriers, many smart drug delivery systems (DDS) have been developed. In this review, we will introduce two representative type I RIPs, trichosanthin (TCS) and gelonin (Gel), and overview the major biobarriers for protein-based cancer therapy. Finally, we outline advances on the development of smart DDS for effective delivery of these cytotoxic proteins for various applications in cancer treatment.

Structural and Functional Investigation and Pharmacological Mechanism of Trichosanthin, a Type 1 Ribosome-Inactivating Protein

Trichosanthin (TCS) is an RNA N-glycosidase that depurinates adenine-4324 in the conserved α-sarcin/ricin loop (α-SRL) of rat 28 S ribosomal RNA (rRNA). TCS has only one chain, and is classified as type 1 ribosome-inactivating protein (RIP). Our structural studies revealed that TCS consists of two domains, with five conserved catalytic residues Tyr70, Tyr111, Glu160, Arg163 and Phe192 at the active cleft formed between them. We also found that the structural requirements of TCS to interact with the ribosomal stalk protein P2 C-terminal tail. The structural analyses suggest TCS attacks ribosomes by first binding to the C-terminal domain of ribosomal P protein. TCS exhibits a broad spectrum of biological and pharmacological activities including anti-tumor, anti-virus, and immune regulatory activities. This review summarizes an updated knowledge in the structural and functional studies and the mechanism of its multiple pharmacological effects.

Ribosome-inactivating proteins (RIPs) and their important health promoting property

Ribosome-inactivating proteins (RIPs), widely present in plants, certain fungi and bacteria, can inhibit protein synthesis by removing one or more specific adenine residues from the large subunit of ribosomal RNAs (rRNAs).

Trichosanthin suppresses the proliferation of glioma cells by inhibiting LGR5 expression and the Wnt/β-catenin signaling pathway

Studies have indicated that trichosanthin (TCS), a bioactive protein extracted and purified from the tuberous root of Trichosanthes kirilowii (a well-known traditional Chinese medicinal plant), produces antitumor effects on various types of cancer cells. However, the effects of TCS on glioma cells are poorly understood. The objective of this study was to investigate the antitumor effects of TCS on the U87 and U251 cell lines. The in vitro effects of TCS on these two cell lines were determined using a Cell Counting Kit-8 (CCK-8) assay, Annexin V-FITC staining, DAPI staining, Transwell assays, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assays, 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-imidacar-bocyanine iodide (JC-1) staining and western blotting, which was utilized to assess the expression of leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) and key proteins in the Wnt/β-catenin signaling pathway. Our data indicated that TCS inhibited the proliferation of glioma cells in a dose- and time-dependent manner and played a role in inhibiting glioma cell invasion and migration. Additional investigation revealed that the expression levels of LGR5 and of key proteins in the Wnt/β-catenin signaling pathway were markedly decreased after TCS treatment. The results suggest that TCS may induce apoptosis in glioma cells by targeting LGR5 and repressing the Wnt/β-catenin signaling pathway. In the future, in vivo experiments should be conducted to examine the potential use of this compound as a novel therapeutic agent for gliomas.

Low concentrations of trichosanthin induce apoptosis and cell cycle arrest via c-Jun N-terminal protein kinase/mitogen-activated protein kinase activation

Trichosanthin (TCS) is a type I ribosome--inactivating protein, which inhibits cell viability in human epithelial type 2 (HEp-2) and AMC-HN-8 human laryngeal epidermoid carcinoma cells. Although TCS is a potential chemotherapeutic agent, its mechanism of action remains to be elucidated. In the present study, HEp-2 and AMC-HN-8 cells were treated with different concentrations of TCS combined with or without cisplatin. After 5 days of successive treatment, different experimental groups were detected using a cell counting kit-8 and the collected supernatants were analyzed using a lactate dehydrogenase kit. Flow cytometric assays were performed to detect apoptosis and cell cycle arrest in the HEp-2 and AMC-HN-8 cells, reverse transcription quantitative polymerase chain reaction was performed to detect the levels of p27, p21WAF and western blot analysis was performed to detect changes in c-Jun N-terminal protein kinase (JNK)/phosphorylated (phospho)-JNK, p38/phospho-p38, extracellular signal-regulated kinase (ERK)/phospho-ERK, caspase-3 and caspase-9 in the HEp-2 and AMC-HN-8 cancer cells. TCS significantly inhibited the cell viability of the HEp-2 and AMC-HN-8 cells, independently of necrosis. TCS induced apoptosis and increased the percentage of HEp-2 and AMC-HN-8 cells in the S-phase of the cell cycle. In addition, the JNK/mitogen-activated protein kinase (MAPK) pathway was activated by TCS in the HEp-2 and AMC-HN-8 cells. Low concentrations of TCS also induced apoptosis and S-phase cell cycle arrest in the HEp-2 and AMC-HN-8 cells. The antitumor effects of TCS may be associated with JNK/MAPK activation.

Different mechanism of LPS-induced calcium increase in human lung epithelial cell and microvascular endothelial cell: a cell culture study in a model for ARDS

Acute respiratory distress syndrome (ARDS) is a contemporary term incorporating the historic 'acute lung injury' and the colloquial term 'shock lung'. ARDS remains a serious and enigmatic human disease, causing significant mortality. The mechanisms involved at the alveolar cell/capillary endothelial interface have been explored but to date we lack clarity on the role of intracellular calcium ([Ca(2+)]i) fluxes across this interface. To explore the mechanisms of Ca(2+) induced inflammatory reaction in epithelial cells and pulmonary microvascular endothelial cells (HMVEC) located at the two sides of blood-air barrier, lung epithelial A549 and HMVEC cells were treated with LPS. Our results demonstrated that LPS evoked the increase of [Ca(2+)]i, TNF-α and IL-8 in both cells types. The [Ca(2+)]i increases involved intracellular but not extracellular Ca(2+) sources in A549, but both intracellular and extracellular Ca(2+) sources in HMVEC cells. The effects of LPS on both cells types were completely inhibited by the combination of LPS and CaSR-targeted siRNA. Furthermore, LPS-inhibited cell proliferations were significantly reversed by the combined treatment. Therefore, LPS induced different mechanisms of [Ca(2+)]i increase during the activation of CaSR in A549 and HMVEC cells, which translates into functional outputs related to ARDS.

miR-181b promotes cell proliferation and reduces apoptosis by repressing the expression of adenylyl cyclase 9 (AC9) in cervical cancer cells

MicroRNAs are a class of small, endogenous, non-coding RNAs that function as post-transcriptional regulators. In this study, we found that miR-181b promoted cell proliferation and inhibited cell apoptosis in cervical cancer cells. And we validated a new miR-181b target gene, adenylyl cyclase 9 (AC9). miR-181b restricted cAMP production by post-transcriptionally downregulating AC9 expression. Phenotypic experiments indicated that miR-181b and AC9 exerted opposite effects on cell proliferation and apoptosis.

Cyclic AMP-response element regulated cell cycle arrests in cancer cells

Recently, we have demonstrated that trichosanthin (TCS), a promising agent for the treatment of cervical adenocarcinoma, inhibited HeLa cell proliferation through the PKC/MAPK/CREB signal pathway. Furthermore, TCS down-regulated Bcl-2 expression was abrogated by a decoy oligonucleotide (OGN) to the cyclic AMP-responsive element (CRE). The decoy OGN blocked the binding of CRE-binding protein (CREB) to Bcl-2. These results suggested that CRE-mediated gene expression may play a pivotal role in HeLa cell proliferation. However, little is known about the effect of TCS on cell cycle arrests, particularly, whether the genes involved in cell cycle were regulated by CRE. Our present study shows that the arrests of S, G1 and G2/M phases were accompanied by the significant down-regulation of cyclin A, D1 and CDK 2, 4 in HeLa cells, cyclin D1, E and CDK 2, 4 in Caski and C33a cells, and cyclin A, B1, E and CDK 2 in SW1990 cells. However, the cell cycle arrests were reversed via the significant up-regulation of cyclin A and D1, by the combined treatment of TCS and CRE. In conclusion, these data demonstrate for the first time that specific cell cycle arrests in cancer cells can be induced by TCS by inhibiting the binding of CREB to CRE on genes related to cell proliferation.

Anti-tumor action of trichosanthin, a type 1 ribosome-inactivating protein, employed in traditional Chinese medicine: a mini review

Trichosanthin (TCS) as a midterm abortifacient medicine has been used clinically in traditional Chinese medicine for centuries. Additionally, TCS manifests a host of pharmacological properties, for instance, anti-HIV and anti-tumor activities. TCS has been reported to inhibit cell growth of a diversity of cancers, including cervical cancer, choriocarcinoma, and leukemia/lymphoma, etc. This article purported to review the various anti-tumor activities of TCS and the mechanism of apoptosis it induced in these tumor cells. These research progresses provide an insight into cancer research and treatment as well as disclose new pharmacological properties of the ancient but popular Chinese medicine.

Synergistic effects of amyloid peptides and lead on human neuroblastoma cells

Aggregated amyloid peptides (AP), major components of senile plaques, have been considered to play a very important and crucial role in the development and neuro-pathogenesis of Alzheimer's disease (AD). In the present in vitro, study the synergistic effects of Pb(2+), a heavy metal, and AP on the human neuroblastoma SH-SY5Y cells were investigated. The cells treated with Pb(2+) (0.01-10 μM) alone exhibited a significant decrease in viability and IC(50) was 5 μM. A similar decrease in viability was also observed when the cells were exposed to AP, Aβ1-40 (20-120 μM) and Aβ25-35 (2.5-15 μM) for 48 hrs. The IC(50) values were 60 μM and 7.5 μM for Aβ1-40 and Aβ25-35 respectively. To assess the synergistic effects the cells were exposed to IC(50) of both AP and Pb(2+), which resulted in further reduction of the viability. The study was extended to determine the lactate dehydrogenase (LDH) release to assess the cytotoxic effects, 8-isoprostane for extent of oxidative damage, COX 1 and 2 for inflammation related changes, p53 protein for DNA damage and protein kinases A and C for signal transduction. The data suggest that the toxic effects of AP were most potent in the presence of Pb(2+), resulting in an aggravated clinical pathological condition. This could be attributed to the oxidative stress, inflammation neuronal apoptosis and an alteration in the activities of the signaling enzymes.

Inhibition of gap junction channel attenuates the migration of breast cancer cells

Gap junction provides intercellular communications that play a critical role in invasion of metastatic cancer cells. However, the effects of inhibiting this pathway in breast cancer cell migration have not been investigated. Here, we present data demonstrating that functional blockade of gap junctions during the formation of monolayer decreased the levels of aligned fibers of actin between neighboring breast cancer cells. Furthermore, gap junction inhibitors attenuated the invasion ability of highly metastatic MDA-MB-231 cells, but had no significant effects on less invasive MCF-7 cells, which caused by shRANKL. Our work is the first to demonstrate the inhibitory effect of gap junction channel inhibitors on the migration of highly invasive breast cancer cells.

Trichosanthin enhances anti-tumor immune response in a murine Lewis lung cancer model by boosting the interaction between TSLC1 and CRTAM

Trichosanthin (TCS), extracted from the Chinese medicinal herb Trichosanthes kirilowi, has shown promise for the inhibition of tumor growth. However, its immunomodulatory effect on tumor-host interaction remains unknown. In this study, we focused on the effect of TCS on murine anti-tumor immune response in the 3LL Lewis lung carcinoma tumor model and explored the possible molecular pathways involved. In addition to inhibiting cell proliferation and inducing apoptosis in the 3LL tumor, TCS retarded tumor growth and prolonged mouse survival more significantly in C57BL/6 immunocompetent mice than in nude mice. This reflected the fact that the host immune system was involved in tumor eradication. Using FACS analysis, we found that TCS increased the percentage of effector T cells, particularly Interferon-gamma (IFN-γ) producing CD4(+) and CD8(+) T cells from tumor-bearing mice. TCS also promoted the vigorous proliferation of antigen-specific effector T cells, markedly increased Th1 cytokine secretion and elicited more memory T cells in tumor-bearing mice, consequently enhancing the anti-tumor response and inducing immune protection. Furthermore, we found that TCS upregulated the expression of tumor suppressor in lung cancer 1 (TSLC1) in 3LL tumor cells and the expression of its ligand, class I-restricted T cell-associated molecule (CRTAM), in effector T cells. Blocking TSLC1 expression with small interfering RNA (siRNA) significantly eliminated the effects of TCS on the proliferation and cytokine secretion of effector T cells, suggesting that TCS enhances anti-tumor immune response at least partially by boosting the interaction between TSLC1 and CRTAM. Collectively, our data demonstrate that TCS not only affects tumor cells directly, but also enhances anti-tumor immunity via the interaction between TSLC1 and CRTAM. These findings may lead to the development of a novel approach for tumor regression.

Possible mechanisms of trichosanthin-induced apoptosis of tumor cells

Trichosanthin (TCS) is a type I ribosome-inactivating protein that is isolated from the root tubers of the Chinese medicinal herb Trichosanthes kirilowii Maximowicz. TCS has been used as an abortifacient for 1,500 years in China because of its high toxicity on trophoblasts. Over the past 20 years, TCS has been the subject of much research because of its potential antitumor activities. Many reports have revealed that TCS is cytotoxic in a variety of tumor cell lines in vitro and in vivo. Monoclonal antibody-conjugated TCS could enhance its antitumor efficacy; thus, TCS is considered to be a potential biological agent for cancer treatment. TCS is able to inhibit protein synthesis and consequently induce necrosis. Recent studies have demonstrated that TCS does indeed induce apoptosis in several tumor cell lines. Although TCS-induced apoptosis of tumor cell lines is now well known, the underlying mechanisms remain to be elucidated. The purpose of this review was to investigate the effects of TCS and its possible mechanisms of action, based on published literature and the results of our own studies.

Increase of cytosolic calcium induced by trichosanthin suppresses cAMP/PKC levels through the inhibition of adenylyl cyclase activity in HeLa cells

Increase of cytosolic free calcium played a pivotal role in apoptotic cells induced by trichosanthin. However, little is known about the influence of cytosolic calcium increase on adenylyl cyclase activity and intracellular cAMP signaling pathway in HeLa cells. The present study showed that an influx of extracellular Ca2+ initiated by trichosanthin was required for the suppression of adenylyl cyclase activity and decrease of intracellular cAMP level. Furthermore, this inhibition was abolished by activation of PKC rather than PKA. Therefore, our results suggested that increase of cytosolic calcium induced by trichosanthin inhibits cAMP levels via suppression of adenylyl cyclase activity.

Effects of fractal surface on C6 glioma cell morphogenesis and differentiation in vitro

Neurons and glial cells in the brain are surrounded by a fractal environment. A fractal alkylketene dimmer (AKD) surface was shown to provide such a biomimetic environment for glial cell culture. However, little is known about the effects of fractal surface on the complexity of cell morphology. In particular, whether fractal surface induces glial cell differentiation remains to be elucidated. The present work, thus determined the fractal dimension (FD) of cell complexity with a geometrically calculational parameter, the expressions of GFAP gene and protein in C6 glioma cells on fractal AKD, non-fractal AKD and PLL-coated surfaces. Fractal surface suppressed the proliferation of glioma cell, and significantly increased the length and number of cell process. Furthermore, the enhanced values of FD were accompanied with the expressions of GFAP gene and protein, especially that of gene. However, cells on non-fractal and PLL surface proliferated gradually along with the culture time, showing the fibroblast-like morphology, and accompanied with the consistent expressions of GFAP gene and protein. These results suggested that C6 glioma cell differentiation can be induced by fractal AKD surface.

Low-density lipoprotein receptor-related protein 1 is an essential receptor for trichosanthin in 2 choriocarcinoma cell lines

Type-I ribosome-inactivating protein-trichosanthin (TCS) exhibits selective cytotoxicity toward different types of cells. It is believed that the cytotoxicity results from the inhibition of ribosomes to decrease protein synthesis, thereby indicating that there are specific mechanisms for TCS entry into target cells to reach the ribosomes. Low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) is a large scavenger receptor that is responsible for the binding and endocytosis of diverse biological ligands on the cell surface. In this study, we demonstrated that 2 choriocarcinoma cell lines can significantly bind and internalize TCS. In contrast, Hela cell line displayed no obvious TCS binding and endocytosis. Furthermore LRP1 gene silencing in JAR and BeWo cell lines blocked TCS binding; TCS could also interact with LRP1.The results of our study established that LRP1 was a major receptor for phagocytosis of TCS in JAR and BeWo cell lines and might be the molecular basis of TCS abortificient and anti-choriocarcinoma activity.

Increase in cytosolic calcium maintains plasma membrane integrity through the formation of microtubule ring structure in apoptotic cervical cancer cells induced by trichosanthin

This study investigates the role of dysregulated cytosolic free calcium ([Ca(2+)]c) homeostasis on microtubule (MT) ring structure in apoptotic cervical cancer (HeLa) cells induced by trichosanthin (TCS), a type I ribosome inactivating protein (RIP). The TCS-induced decrease in cell viability was significantly enhanced in combination with the specific calcium chelator, EGTA-AM. Sequestration of [Ca(2+)]c markedly disrupted the special MT ring structure. Furthermore, TCS tended to increase LDH release, whereas no significant differences were observed until 48 h of the treatment. In contrast, combined addition of EGTA-AM or colchicine (an inhibitor of tubulin polymerization) significantly reinforced LDH release. The data suggest that TCS-elevated [Ca(2+)]c maintains plasma membrane integrity via the formation of the MT ring structure in apoptotic HeLa cells.

CREB, a possible upstream regulator of Bcl-2 in trichosanthin-induced HeLa cell apoptosis

Our previous reports indicated that cyclic AMP response element-binding (CREB) protein was involved in the regulation of Bcl-2 expression in apoptotic HeLa cells induced by trichosanthin (TCS). Here we presented that blockade the binding site of CREB to Bcl-2 by a CRE decoy oligonucleotide abrogated the TCS-decreased Bcl-2 expression. Furthermore, overexpression of phosphorylated CREB (p-CREB) in cells transfected with p-CREB/GFP fusion construct resulted in an increase of Bcl-2 protein content, however, this increase was attenuated by TCS treatment. Therefore, this data supports the hypothesis that CREB is a possible upstream regulator of Bcl-2 in apoptotic HeLa cells induced by TCS. The study provides new insights into understanding the mechanism of TCS in the treatment of cervical cancer.