Galloflavin, a new lactate dehydrogenase inhibitor, induces the death of human breast cancer cells with different glycolytic attitude by affecting distinct signaling pathways

Galloflavin (GF), a recently identified lactate dehydrogenase inhibitor, hinders the proliferation of cancer cells by blocking glycolysis and ATP production. The aim of the present experiments was to study the effect of this compound on breast cancer cell lines reproducing different pathological subtypes of this tumor: MCF-7 (the well differentiated form), MDA-MB-231 (the aggressive triple negative tumor) and MCF-Tam (a sub-line of MCF-7 with acquired tamoxifen resistance). We observed marked differences in the energetic metabolism of these cell lines. Compared to MCF-7 cells, both MDA-MB-231 and MCF-Tam cells exhibited higher LDH levels and glucose uptake and showed lower capacity of oxygen consumption. In spite of these differences, GF exerted similar growth inhibitory effects. This result was explained by the finding of a constitutively activated stress response in MDA-MB-231 and MCF-Tam cells, which reproduce the poor prognosis tumor forms. As a further proof, different signaling pathways were found to be involved in the antiproliferative action of GF. In MCF-7 cells we observed a down regulation of the ERα-mediated signaling needed for cell survival. On the contrary, in MCF-Tam and MDA-MB-231 cells growth inhibition appeared to be contributed by an oxidative stress condition. The prevalent mechanism of cell death was found to be apoptosis induction. Because of the clinical relevance of breast cancer forms having the triple negative and/or chemoresistant phenotype, our results showing comparable effects of GF even on aggressively growing cells encourage further studies to verify the potential of this compound in improving the chemotherapy of breast cancer.

Synthesis and characterization of a new family of electroactive alkali metal doped mesoporous Nb, Ta, and Ti oxides and evidence for an Anderson transition in reduced mesoporous titanium oxide

Recently we reported that mesoporous niobium oxide can be chemically reduced by Na-naphthalene while fully retaining its mesostructure. This was the first report of a molecular sieve acting as a stoichiometric electron acceptor. Herein we expand on the initial work by presenting a detailed study on Li-, Na-, K-, Rb-, and Cs-reduced samples of mesoporous Nb oxide, as well as Li-reduced mesoporous Ta and Ti oxides. While the Nb- and Ta-based materials fully retained their structure on reduction as determined by X-ray diffraction (XRD) and nitrogen adsorption, the Li-reduced Ti material retained high surface area and narrow pore size distribution, but lost its diffraction pattern, indicating an increased level of disorder in this material. X-ray photoelectron spectroscopy (XPS) and UV-visible reflectance spectroscopy revealed that all reduced mesoporous oxides studied have a similar electronic structure, corresponding to the presence of a disordered impurity band in the material lying between the valence band and the conduction band. Electron paramagnetic resonance (EPR) studies suggest that the electron in this impurity level is unpaired and best described as a free electron, only loosely bound to the alkali or transition metal. SQUID magnetometry showed that all reduced materials are paramagnetic, further confirming the presence of unpaired electrons in the structure. All materials in this study were insulating with the exception of the Li-reduced mesoporous Ti material, which was highly conducting, possibly due to an Anderson transition. Electrochemical studies on the unreduced mesoporous oxides demonstrated that while the Ta and Nb materials are capacitors with only a small degree of reversible electrochemical behavior in the bulk sample, the Ti material was an electrical conductor with fully reversible redox behavior.