Ukrain modulates glial fibrillary acidic protein, but not connexin 43 expression, and induces apoptosis in human cultured glioblastoma cells

Anti-tumor effects of vitamin D in glioblastoma: mechanism and therapeutic implications

Glioma is the most prevalent primary brain tumor in adults among which glioblastoma is the most malignant and lethal subtype. Its common resistance to conventional chemotherapeutics calls for the development of alternative or concomitant treatment. Taking advantage of its endocrine function as a neurosteroid, vitamin D has become a target of interest to be used in conjunction with different chemotherapies. In this article, we review the mechanisms through which vitamin D and its analogs induce anti-tumor activity in glioblastoma, and the practical issues relevant to their potential application based on in vitro and in vivo studies. Vitamin D has largely been reported to promote cell cycle arrest and induce cell death to suppress tumor growth in glioblastoma. Glioblastoma cells treated with vitamin D have also shown reduced migratory and invasive phenotypes, and reduced stemness. It is worth noting that vitamin D analogs are able to produce similar inhibitory actions without causing adverse effects such as hypercalcemia in vivo. Upregulation of vitamin D receptors by vitamin D and its analogs may also play a role in enhancing its anti-tumor activity. Based on current findings and taking into consideration its potential cancer-protective effects, the clinical application of vitamin D in glioblastoma treatment and prevention will be discussed. With some study findings subject to controversy, further investigation is warranted to elucidate the mechanism of action of vitamin D and to evaluate relevant issues regarding its treatment efficacy and potential clinical application.

Current Progress of Phytomedicine in Glioblastoma Therapy

Glioblastoma multiforme, an intrusive brain cancer, has the lowest survival rate of all brain cancers. The chemotherapy utilized to prevent their proliferation and propagation is limited due to modulation of complex cancer signalling pathways. These complex pathways provide infiltrative and drug evading properties leading to the development of chemotherapy resistance. Therefore, the development and discovery of such interventions or therapies that can bypass all these resistive barriers to ameliorate glioma prognosis and survival is of profound importance. Medicinal plants are comprised of an exorbitant range of phytochemicals that have the broad-spectrum capability to target intrusive brain cancers, modulate anti-cancer pathways and immunological responses to facilitate their eradication, and induce apoptosis. These phytocompounds also interfere with several oncogenic proteins that promote cancer invasiveness and metastasis, chemotherapy resistance and angiogenesis. These plants are extremely vital for promising anti-glioma therapy to avert glioma proliferation and recurrence. In this review, we acquired recent literature on medicinal plants whose extracts/bioactive ingredients are newly exploited in glioma therapeutics, and also highlighted their mode of action and pharmacological profile.

Chelidonine selectively inhibits the growth of gefitinib-resistant non-small cell lung cancer cells through the EGFR-AMPK pathway

Tyrosine kinase inhibitors (TKIs) have been widely used for the clinical treatment of patients with non-small cell lung cancer (NSCLC) harboring mutations in the EGFR. Unfortunately, due to the secondary mutation in EGFR, eventual drug-resistance is inevitable. Therefore, to overcome the resistance, new agent is urgently required. Chelidonine, extracted from the roots of Chelidonium majus, was proved to effectively suppress the growth of NSCLC cells with EGFR double mutation. Proteomics analysis indicated that mitochondrial respiratory chain was significantly inhibited by chelidonine, and inhibitor of AMPK effectively blocked the apoptosis induced by chelidonine. Molecular dynamics simulations indicated that chelidonine could directly bind to EGFR and showed a much higher binding affinity to EGFR^L858R/T790M than EGFR^WT, which demonstrated that chelidonine could selectively inhibit the phosphorylation of EGFR in cells with EGFR double-mutation. In vivo study revealed that chelidonine has a similar inhibitory effect like second generation TKI Afatinib. In conclusion, targeting EGFR and inhibition of mitochondrial function is a promising anti-cancer therapeutic strategy for inhibiting NSCLC with EGFR mutation and TKI resistance.

Greater Celandine's Ups and Downs-21 Centuries of Medicinal Uses of Chelidonium majus From the Viewpoint of Today's Pharmacology

As antique as Dioscorides era are the first records on using Chelidonium as a remedy to several sicknesses. Inspired by the "signatura rerum" principle and an apparent ancient folk tradition, various indications were given, such as anti-jaundice and cholagogue, pain-relieving, and quite often mentioned-ophthalmological problems. Central and Eastern European folk medicine has always been using this herb extensively. In this region, the plant is known under many unique vernacular names, especially in Slavonic languages, associated or not with old Greek relation to "chelidon"-the swallow. Typically for Papaveroidae subfamily, yellow-colored latex is produced in abundance and leaks intensely upon injury. Major pharmacologically relevant components, most of which were first isolated over a century ago, are isoquinoline alkaloids-berberine, chelerythrine, chelidonine, coptisine, sanguinarine. Modern pharmacology took interest in this herb but it has not ended up in gaining an officially approved and evidence-based herbal medicine status. On the contrary, the number of relevant studies and publications tended to drop. Recently, some controversial reports and sometimes insufficiently proven studies appeared, suggesting anticancer properties. Anticancer potential was in line with anecdotical knowledge spread in East European countries, however, in the absence of directly-acting cytostatic compounds, some other mechanisms might be involved. Other properties that could boost the interest in this herb are antimicrobial and antiviral activities. Being a common synanthropic weed or ruderal plant, C. majus spreads in all temperate Eurasia and acclimates well to North America. Little is known about the natural variation of bioactive metabolites, including several aforementioned isoquinoline alkaloids. In this review, we put together older and recent literature data on phytochemistry, pharmacology, and clinical studies on C. majus aiming at a critical evaluation of state-of-the-art from the viewpoint of historical and folk indications. The controversies around this herb, the safety and drug quality issues and a prospective role in phytotherapy are discussed as well.

Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide-based glioblastoma chemotherapy

Temozolomide (TMZ), an alkylating agent, is recommended as the initial treatment for high-grade glioblastoma. TMZ is widely used, but its short half-life and the frequency of tumor resistance limit its therapeutic efficacy. In the present study, the anticancer effect of vitamin D (VD) combined with TMZ upon glioblastoma was determined, and the underlying mechanism of this effect was identified. Through cell viability, clonogenic and wound healing assays, the current study demonstrated that treatment of a C6 glioblastoma cell line with TMZ and VD resulted in significantly increased in vitro antitumor effects compared with either VD or TMZ alone. Autophagy, hypothesized to be the dominant mechanism underlying TMZ-based tumor cell death, was maximally activated in TMZ and VD co-treated C6 cells. This was demonstrated by ultrastructural observations of autophagosomes, increased size and number of microtubule-associated protein 1 light chain 3 (LC3) puncta and increased conversion of LC3-I to LC3-II. However, the extent of apoptosis was not significantly different between cells treated with TMZ and VD and those treated with TMZ alone. Addition of the autophagy inhibitor 3-methyladenine markedly inhibited the anticancer effect of TMZ and VD treatment, indicating that the chemosensitizing effect of VD in TMZ-based glioblastoma therapy is generated through enhancement of cytotoxic autophagy. TMZ and VD co-treatment also significantly inhibited tumor progression and prolonged survival duration in rat glioblastoma orthotopic xenograft models when compared with TMZ treatment alone. These in vivo results are concordant with the aforementioned in vitro results, together revealing that the combined use of TMZ and VD exerts synergistic antitumor effects on rat models of glioblastoma and may represent an effective therapeutic strategy.

Pancreatic cancer cells retain the epithelial-related phenotype and modify mitotic spindle microtubules after the administration of ukrain in vitro

The aim of this study is to characterize the phenotype of pancreatic ductal adenocarcinoma (PDAC) cells in relation to the expression of epithelial-to-mesenchymal transition (EMT) markers and determine whether ukrain, an anticancer drug based on the alkaloids extracted from greater celandine, modulates in vitro the malignant behavior of PDAC cells in order to extend our understanding of its therapeutic potential. Three cell lines (HPAF-II, HPAC, and PL45) were treated with ukrain (5, 10, and 20 μmol/l) for 48 h or left untreated (control). Cell proliferation was assessed by growth curves. Apoptosis was determined by Hoechst nuclear staining and by cytochrome c and caspase-8 expressions. The EMT markers E-cadherin, β-catenin, and vimentin, as well as actin and tubulin cytoskeletons, were analyzed by immunofluorescence. Interphase and mitotic microtubules as well as abnormal mitotic figures were studied by fluorescence microscopy after tubulin immunolabeling. Ukrain strongly suppressed cell proliferation and induced apoptosis possibly through an extrinsic pathway as cytochrome c immunoreactivity suggested that the integrity of the mitochondria was not affected. Tubulin expression indicated an antiproliferative effect of ukrain on the basis of alterations in mitotic spindle microtubule dynamics, leading to abnormal mitosis. Membranous E-cadherin/β-catenin immunoreactivity was similarly expressed in control-treated and ukrain-treated cells, although the drug upregulated E-cadherin in cell lysates. Our results suggest that ukrain exerts its chemotherapeutic action on PDAC cells targeting mitotic spindle microtubules, leading to abnormal mitosis and apoptosis, and favoring cell cohesiveness. The differentiated epithelial phenotype of HPAF-II, HPAC, and PL45 cell lines concomitant with a highly invasive potential suggests that further experiments will be necessary to definitively clarify the role of EMT in PDAC progression.

A molecular screening approach to identify and characterize inhibitors of glioblastoma stem cells

Glioblastoma (GBM) is among the most lethal of all cancers. GBM consist of a heterogeneous population of tumor cells among which a tumor-initiating and treatment-resistant subpopulation, here termed GBM stem cells, have been identified as primary therapeutic targets. Here, we describe a high-throughput small molecule screening approach that enables the identification and characterization of chemical compounds that are effective against GBM stem cells. The paradigm uses a tissue culture model to enrich for GBM stem cells derived from human GBM resections and combines a phenotype-based screen with gene target-specific screens for compound identification. We used 31,624 small molecules from 7 chemical libraries that we characterized and ranked based on their effect on a panel of GBM stem cell-enriched cultures and their effect on the expression of a module of genes whose expression negatively correlates with clinical outcome: MELK, ASPM, TOP2A, and FOXM1b. Of the 11 compounds meeting criteria for exerting differential effects across cell types used, 4 compounds showed selectivity by inhibiting multiple GBM stem cells-enriched cultures compared with nonenriched cultures: emetine, n-arachidonoyl dopamine, n-oleoyldopamine (OLDA), and n-palmitoyl dopamine. ChemBridge compounds #5560509 and #5256360 inhibited the expression of the 4 mitotic module genes. OLDA, emetine, and compounds #5560509 and #5256360 were chosen for more detailed study and inhibited GBM stem cells in self-renewal assays in vitro and in a xenograft model in vivo. These studies show that our screening strategy provides potential candidates and a blueprint for lead compound identification in larger scale screens or screens involving other cancer types.

Transcriptional down regulation of hTERT and senescence induction in HepG2 cells by chelidonine

AIM: To investigate the potential effects of chelidonine, the main alkaloid of Chelidonium majus, on telomerase activity and its regulation in HepG2 cells.

METHODS: Cytotoxicity of chelidonine for HepG2 cells was determined by neutral red assay. A modified polymerase chain reaction (PCR)-based telomerase repeat amplification protocol was used to estimate relative telomerase activity in chelidonine-treated cells in comparison with the untreated control cells. Relative expression level of the catalytic subunit of telomerase (hTERT) gene and P-glycoprotein (pgp) were estimated using semi-quantitative real-time reverse transcription-PCR (RT-PCR). Cell senescence in treated cells was demonstrated using a β-galactosidase test.

RESULTS: Cytotoxicity of chelidonine in HepG2 cells was not dose-dependent and tended to reach plateau immediately after the living cells were reduced in number to slightly higher than 50%. However, 12 &mgr;mol/L concentration of chelidonine was considered as LD₅₀, where the maximal attainable effects were realized. Real-time RT-PCR data showed that the expression of pgp increased three-fold in chelidonine treated HepG2 cells in comparison with the untreated controls. Morphologically, treated HepG2 cells showed apoptotic features after 24 h and a small fraction of cells appeared with single blister cell death. The relative expression level of Bcl-2 dropped to less than 50% of control cells at a sub-apoptotic concentration of chelidonine and subsequently increased to higher than 120% at LD₅₀. Telomerase activity was reduced considerably after administration of very low doses of chelidonine, whereas higher concentrations of chelidonine did not remarkably enhance the effect. Real-time RT-PCR experiments indicated a drastic decrease in expression level of hTERT subunit of telomerase under treatment with chelidonine. Repeated treatment of cells with very low doses of chelidonine caused a decline in growth rate by 4 wk and many of the cells appeared to be aged with large volume and dark staining in the β-galactosidase assay.

CONCLUSION: Chelidonine reduces telomerase activity through down-regulation of hTERT expression. Senescence induction might not be directly caused by reducing telomerase activity as it occurs after a few population doublings.