Cytotoxicity, Proapoptotic Activity and Drug-like Potential of Quercetin and Kaempferol in Glioblastoma Cells: Preclinical Insights.

Despite the increasing understanding of the pathogenesis of glioblastoma (GBM), treatment options for this tumor remain limited. Recently, the therapeutic potential of natural compounds has attracted great interest. Thus, dietary flavonoids quercetin (QCT) and kaempferol (KMF) were investigated as potential cytostatic agents in GBM. Moreover, the physicochemical properties of QCT and KMF, determining their bioavailability and therapeutic efficiency, were evaluated. We proved that both polyphenols significantly reduced the viability of GBM cells. We also demonstrated that both QCT and KMF evoked the cytotoxic effect in T98G cells via induction of apoptotic cell death as shown by increased activity of caspase 3/7 and caspase 9 together with an overexpression of the cleaved form of PARP. Apoptosis was additionally accompanied by the activation of stress responses in QCT- and KMF-treated cells. Both polyphenols caused oxidative stress and endoplasmic reticulum (ER) stress, as demonstrated by the increased generation of reactive oxygen species (ROS), deregulated expressions of superoxide dismutases (SOD2 and Sod1 on protein and transcriptomic levels, respectively), as well as an overexpression of ERO1α, GRP78, p-JNK, and an up-regulation of Chop, Atf4 and Atf6α genes. The antitumor effect of QCT and KMF was also confirmed in vivo, showing reduced growth of tumor xenografts in the chick chorioallantoic membrane (CAM) experiment. Moreover, electrophoretic light scattering (ELS) was used to measure the zeta potential of cell membranes upon exposition to QCT and KMF. Additionally, on the basis of existing physicochemical data, the drug-likeness score of QCT and KMF was evaluated. Analyses showed that both compounds accomplish Lipinski's Rule of 5, and they both fit into the criteria of good central nervous system (CNS) drugs. Altogether, our data support the idea that QCT and KMF might be plausible candidates for evaluation as therapeutic agents in preclinical models of glioblastoma.

The Pseudokinase TRIB3 Negatively Regulates the HER2 Receptor Pathway and Is a Biomarker of Good Prognosis in Luminal Breast Cancer.

BACKGROUND: Tribbles pseudokinase 3 (TRIB3) has been proposed to both promote and restrict cancer generation and progression. However, the precise mechanisms that determine this dual role of TRIB3 in cancer remain to be understood. In this study we aimed to investigate the role of TRIB3 in luminal breast cancer, the most frequent subtype of this malignancy. METHODS: We genetically manipulated TRIB3 expression in a panel of luminal breast cancer cell lines and analyzed its impact on cell proliferation, and the phosphorylation, levels, or subcellular localization of TRIB3 and other protein regulators of key signaling pathways in luminal breast cancer. We also analyzed TRIB3 protein expression in samples from luminal breast cancer patients and performed bioinformatic analyses in public datasets. RESULTS: TRIB3 enhanced the proliferation and AKT phosphorylation in luminal A (HER2-) but decreased them in luminal B (HER2+) breast cancer cell lines. TRIB3 negatively regulated the stability of HER2 in luminal B breast cancer cell lines. TRIB3 expression was associated with increased disease-free survival and a better response to therapy in luminal breast cancer patients. CONCLUSIONS: Our findings support the exploration of TRIB3 as a potential biomarker and therapeutic target in luminal breast cancer.

Midkine signaling maintains the self-renewal and tumorigenic capacity of glioma initiating cells.

Glioblastoma (GBM) is one of the most aggressive forms of cancer. It has been proposed that the presence within these tumors of a population of cells with stem-like features termed Glioma Initiating Cells (GICs) is responsible for the relapses that take place in the patients with this disease. Targeting this cell population is therefore an issue of great therapeutic interest in neuro-oncology. We had previously found that the neurotrophic factor MIDKINE (MDK) promotes resistance to glioma cell death. The main objective of this work is therefore investigating the role of MDK in the regulation of GICs. Methods: Assays of gene and protein expression, self-renewal capacity, autophagy and apoptosis in cultures of GICs derived from GBM samples subjected to different treatments. Analysis of the growth of GICs-derived xenografts generated in mice upon blockade of the MDK and its receptor the ALK receptor tyrosine kinase (ALK) upon exposure to different treatments. Results: Genetic or pharmacological inhibition of MDK or ALK decreases the self-renewal and tumorigenic capacity of GICs via the autophagic degradation of the transcription factor SOX9. Blockade of the MDK/ALK axis in combination with temozolomide depletes the population of GICs in vitro and has a potent anticancer activity in xenografts derived from GICs. Conclusions: The MDK/ALK axis regulates the self-renewal capacity of GICs by controlling the autophagic degradation of the transcription factor SOX9. Inhibition of the MDK/ALK axis may be a therapeutic strategy to target GICs in GBM patients.

Targeting Glioma Initiating Cells with A combined therapy of cannabinoids and temozolomide.

Glioblastoma multiforme (GBM) is the most frequent and aggressive type of brain tumor due, at least in part, to its poor response to current anticancer treatments. These features could be explained, at least partially, by the presence within the tumor mass of a small population of cells termed Glioma Initiating Cells (GICs) that has been proposed to be responsible for the relapses occurring in this disease. Thus, the development of novel therapeutic approaches (and specifically those targeting the population of GICs) is urgently needed to improve the survival of the patients suffering this devastating disease. Previous observations by our group and others have shown that Δ9-Tetrahydrocannabinol (THC, the main active ingredient of marijuana) and other cannabinoids including cannabidiol (CBD) exert antitumoral actions in several animal models of cancer, including gliomas. We also found that the administration of THC (or of THC + CBD at a 1:1 ratio) in combination with temozolomide (TMZ), the benchmark agent for the treatment of GBM, synergistically reduces the growth of glioma xenografts. In this work we investigated the effect of the combination of TMZ and THC:CBD mixtures containing different ratios of the two cannabinoids in preclinical glioma models, including those derived from GICs. Our findings show that TMZ + THC:CBD combinations containing a higher proportion of CDB (but not TMZ + CBD alone) produce a similar antitumoral effect as the administration of TMZ together with THC and CBD at a 1:1 ratio in xenografts generated with glioma cell lines. In addition, we also found that the administration of TMZ + THC:CBD at a 1:1 ratio reduced the growth of orthotopic xenografts generated with GICs derived from GBM patients and enhanced the survival of the animals bearing these intracranial xenografts. Remarkably, the antitumoral effect observed in GICs-derived xenografts was stronger when TMZ was administered together with cannabinoid combinations containing a higher proportion of CBD. These findings support the notion that the administration of TMZ together with THC:CBD combinations - and specifically those containing a higher proportion of CBD - may be therapeutically explored to target the population of GICs in GBM.

Study of puupehenone and related compounds as inhibitors of angiogenesis.

Puupehenone, a sesquiterpene produced by certain sponges, was selected in the course of a blind screening for new potential inhibitors of angiogenesis. In our study, we compare the potential anti-angiogenic activities of puupehenone and another 11 related compounds that were either natural products from marine origin or their synthetic derivatives. The effects of these compounds were determined with cell growth and differentiation assays on bovine aorta endothelial cells. Our results show that these compounds are weak inhibitors to cell growth and are not selective for endothelial cells. However, contrary to cell growth, the differentiation of endothelial cells into tubular structures was completely inhibited by 7 of these compounds at concentrations equal or lower than 3 microM. Three of these compounds, isozonarol, 8-epipuupehedione and 8 epi-9,11-dihydropuupehedione, completely inhibited the in vivo angiogenesis in the CAM assay at doses equal or lower than 30 nmol/egg. Further characterisation showed that these 3 terpenes also inhibited endothelial cell production of urokinase and invasion. One compound (8-epipuupehedione) inhibited endothelial cell migration in a dose-dependent manner. The anti-angiogenic properties of the selected compounds, the simplicity of their structures and the feasibility of their synthesis make them attractive drugs for further evaluation in the treatment of angiogenesis-related pathologies.

Synthesis and biological evaluation of new 1,5-diazaanthraquinones with cytotoxic activity.

A series of 1,5-diazaanthraquinone derivatives was synthesized and their in vitro cytotoxic activities were evaluated against several human cancer cell lines. The 1,5-diazaanthraquinone chromophore has been synthesized either on the basis of hetero Diels-Alder reactions involving different quinoline-5,8-diones and alpha,beta-unsaturated aldehyde N,N-dimethylhydrazones or by thermolysis of different arylaminomethylene Meldrum's acid derivatives. Some of these compounds showed cytotoxic activity comparable to that of mitoxantrone against most of the cell lines tested. Compounds 20, 30, 31 and 37 were 4-54 times more potent that mitoxantrone against A549, H116, PSN1 and T98G cancer cell lines but, interestingly, they were 3-16 times less potent against the human breast carcinoma SKBR3. Some structure-activity relationships are described, the most significant one being the increase in cytotoxicity resulting from the introduction of a halogen atom at the C-4 position.

Synthesis and structure-activity relationships of 1,5-diazaanthraquinones as antitumour compounds.

1,5-Diazaanthraquinone derivatives were synthesized employing single and double hetero Diels-Alder strategies. Their in vitro antitumour activity was assayed using three cell lines. Some of these compounds, specially those bearing methyl or ethyl groups at the C-3,7 positions or chloro at C-4 and methyl at C-7, showed IC(50) values in the 10(-8)M range for human lung carcinoma and human melanoma, which makes them attractive candidates for further development as anticancer agents.