p53 Gene Expression and 2-Methoxyestradiol Treatment Differentially Induce Nuclear Factor Kappa B Activation in Human Lung Cancer Cells with Different p53 Phenotypes

Induction of 2-hydroxycatecholestrogens O-methylation: A missing puzzle piece in diagnostics and treatment of lung cancer

Lung cancer is one of the most common cancers worldwide, causing nearly one million deaths each year. Herein, we present the effect of 2-methoxyestradiol (2-ME), the endogenous metabolite of 17β-estradiol (E2), on non-small cell lung cancer (NSCLC) cells. We observed that 2-ME reduced the viability of lung adenocarcinoma in two-dimensional (2D) and three-dimensional (3D) spheroidal A549 cell culture models. Molecular modeling was carried out aiming to visualize amino acid residues within binding pockets of the acyl-protein thioesterases, namely 1 (APT1) and 2 (APT2), and thus to identify which ones were more likely involved in the interaction with 2-ME. Our findings suggest that 2-ME acts as an APT1 inhibitor enhancing protein palmitoylation and oxidative stress phenomena in the lung cancer cell. In order to support our data, metabolomics of blood serum from NSCLC patients was also performed. Moreover, computational analysis suggests that 2-ME as compared to other estrogen metabolism intermediates is relatively safe in terms of its possible non-receptor bioactivity within healthy human cells due to a very low electrophilic potential and hence no substantial risk of spontaneous covalent modification of biologically protective nucleophiles. We propose that 2-ME can be used as a selective tumor biomarker in the course of certain types of lung cancers and possibly as a therapeutic adjuvant or neoadjuvant.

2-Methoxyestradiol prevents monocyte adhesion to vascular endothelial cells via downregulation of VCAM-1 expression

2-Methoxyestradiol (2-ME) reduces atherosclerotic lesion formation. However, the underlying mechanisms remain largely unknown. In this work, we investigated the effect of 2-ME on monocyte adhesion to vascular endothelial cells. Lipopolysaccharides (LPS) greatly increased the attachment of monocyte onto cultured human umbilical vascular endothelial cells (HUVECs), which was inhibited by 2-ME in a dose- and time-dependent manner, or by the vascular cell adhesion protein-1 (VCAM-1) neutralizing antibody, suggesting that a functional releationship between 2-ME and VCAM-1 may exist. In accordance with this, treatment with 2-ME (10(-)(7)-10(-)(5) M) for 6-48 h downregulated VCAM-1 protein expression. Meanwhile, the nuclear factor κB (NF-κB) p65 subunit activity and its nuclear translocation was inhibited by 2-ME in HUVECs. The PI3K inhibitor wortmannin or the specific Akt siRNA both inhibited the effects of 2-ME, suggesting that 2-ME inhibited p65 activity via PI3K/Akt signaling. In conclusion, 2-ME inhibits VCAM-1 expression and thus prevents monocyte adhesion to vascular endothelial cells via regulation of PI3K/Akt and NF-κB signaling. These findings will be helpful for better understanding the mechanisms through which 2-ME improves endothelial function.

Polymer-related off-target effects in non-viral siRNA delivery

Since off-target effects in non-viral siRNA delivery are quite common but not well understood, in this study various polymer-related effects observed in transfection studies were described and their mechanisms of toxicity were investigated. A variety of stably luciferase-expressing cell lines was compared concerning polymer-mediated effects after transfection with polyplexes of siRNA and poly(ethylene imine) (PEI) or poly(ethylene glycol)-grafted PEI (PEG-PEI). Cell viability, LDH release, gene expression profiles of apoptosis-related genes and promoter activation were investigated. Interestingly, PEG-PEI, which is generally better tolerated than PEI, was found to activate apoptosis in a cell line- and concentration-dependent manner. While both polymers showed sigmoidal dose-response of cell viability in L929 cells (IC(50)(PEI) = 6 μg/ml, IC(50)(PEG-PEI) = 11 μg/ml), H1299/Luc cells exhibited biphasic dose-response for PEG-PEI and stronger apoptosis at 2 μg/ml than at 20 μg/ml PEG-PEI, as shown in TUNEL assays. Gene expression profiling confirmed that H1299/Luc cells underwent apoptosis via thousand-fold activation of TNF receptor-associated factors. Additionally, it was demonstrated that NFkB-mediated CMV promoter activation in stably transfected cells can lead to increased target gene levels after transfection instead of siRNA-mediated knockdown. With these results, polymeric vectors were shown not to be inert substances. Therefore, alterations in gene expression caused by the delivery agent must be known to correctly interpret gene-silencing experiments, to understand the mechanisms of off-target effects, and most of all to further develop vectors with reduced side effects. Taking these observations into account, one established cell line was eventually identified to be suitable for RNAi experiments. As shown by these experiments, materials that have been used for many years can elicit unexpected off-target effects. Therefore, non-viral vectors must be screened for several levels of toxicity to make them promising candidates.