Mutation Status and Glucose Availability Affect the Response to Mitochondria-Targeted Quercetin Derivative in Breast Cancer Cells.

Mitochondria, the main cellular power stations, are important modulators of redox-sensitive signaling pathways that may determine cell survival and cell death decisions. As mitochondrial function is essential for tumorigenesis and cancer progression, mitochondrial targeting has been proposed as an attractive anticancer strategy. In the present study, three mitochondria-targeted quercetin derivatives (mitQ3, 5, and 7) were synthesized and tested against six breast cancer cell lines with different mutation and receptor status, namely ER-positive MCF-7, HER2-positive SK-BR-3, and four triple-negative (TNBC) cells, i.e., MDA-MB-231, MDA-MB-468, BT-20, and Hs 578T cells. In general, the mito-quercetin response was modulated by the mutation status. In contrast to unmodified quercetin, 1 µM mitQ7 induced apoptosis in breast cancer cells. In MCF-7 cells, mitQ7-mediated apoptosis was potentiated under glucose-depleted conditions and was accompanied by elevated mitochondrial superoxide production, while AMPK activation-based energetic stress was associated with the alkalization of intracellular milieu and increased levels of NSUN4. Mito-quercetin also eliminated doxorubicin-induced senescent breast cancer cells, which was accompanied by the depolarization of mitochondrial transmembrane potential. Limited glucose availability also sensitized doxorubicin-induced senescent breast cancer cells to apoptosis. In conclusion, we show an increased cytotoxicity of mitochondria-targeted quercetin derivatives compared to unmodified quercetin against breast cancer cells with different mutation status that can be potentiated by modulating glucose availability.

Electrospun fiber-based micro- and nano-system for delivery of high concentrated quercetin to cancer cells.

The anticancer potential of quercetin (Q), a plant-derived flavonoid, and underlining molecular mechanisms are widely documented in cellular models in vitro. However, biomedical applications of Q are limited due to its low bioavailability and hydrophilicity. In the present study, the electrospinning approach was used to obtain polylactide (PLA) and PLA and polyethylene oxide (PEO)-based micro- and nanofibers containing Q, namely PLA/Q and PLA/PEO/Q, respectively, in a form of non-woven fabrics. The structure and physico-chemical properties of Q-loaded fibers were characterized by scanning electron and atomic force microscopy (SEM and AFM), X-ray powder diffraction (XRD), differential scanning calorimetry (DSC), goniometry and FTIR and Raman spectroscopy. The anticancer action of PLA/Q and PLA/PEO/Q was revealed using two types of cancer and nine cell lines, namely osteosarcoma (MG-63, U-2 OS, SaOS-2 cells) and breast cancer (SK-BR-3, MCF-7, MDA-MB-231, MDA-MB-468, Hs 578T, and BT-20 cells). The anticancer activity of Q-loaded fibers was more pronounced than the action of free Q. PLA/Q and PLA/PEO/Q promoted cell cycle arrest, oxidative stress and apoptotic cell death that was not overcome by heat shock protein (HSP)-mediated adaptive response. PLA/Q and PLA/PEO/Q were biocompatible and safe, as judged by in vitro testing using normal fibroblasts. We postulate that PLA/Q and PLA/PEO/Q with Q releasing activity can be considered as a novel and more efficient micro- and nano-system to deliver Q and eliminate phenotypically different cancer cells.

Non-targeting siRNA-mediated responses are associated with apoptosis in chemotherapy-induced senescent skin cancer cells.

It is widely accepted that siRNA transfection can promote some off-target effects in the genome; however, little is known about how the cells can respond to the presence of non-viral dsRNA. In the present study, non-targeting control siRNA (NTC-siRNA) was used to evaluate its effects on the activity of pathogen and host-derived nucleic acid-associated signaling pathways such as cGAS-STING, RIG-I, MDA5 and NF-κB in A431 skin cancer cells and BJ fibroblasts. NTC-siRNA treatment promoted cytotoxicity in cancer cells. Furthermore, NTC-siRNA-treated doxorubicin-induced senescent cancer cells were more prone to apoptotic cell death compared to untreated doxorubicin-induced senescent cancer cells. NTC-siRNA stimulated the levels of NF-κB, APOBECs, ALY, LRP8 and phosphorylated STING that suggested the involvement of selected components of nucleic acid sensing pathways in NTC-siRNA-mediated cell death response in skin cancer cells. NTC-siRNA-mediated apoptosis in cancer cells was not associated with IFN-ß-based pro-inflammatory response and TRDMT1-based adaptive response. In contrast, in NTC-siRNA-treated fibroblasts, an increase in the levels of RIG-I and IFN-ß was not accompanied by affected cell viability. We propose that the use of NTC-siRNA in genetic engineering may provoke a number of unexpected effects that should be carefully monitored. In our experimental settings, NTC-siRNA promoted the elimination of doxorubicin-induced senescent cancer cells that may have implications in skin cancer therapies.

RNA 5-methylcytosine status is associated with DNMT2/TRDMT1 nuclear localization in osteosarcoma cell lines.

Osteosarcoma (OS) is a pediatric malignant bone tumor with unsatisfying improvements in survival rates due to limited understanding of OS biology and potentially druggable targets. The present study aims to better characterize osteosarcoma U-2 OS, SaOS-2, and MG-63 cell lines that are commonly used as in vitro models of OS. We focused on evaluating the differences in cell death pathways, redox equilibrium, the activity of proliferation-related signaling pathways, DNA damage response, telomere maintenance, DNMT2/TRDMT1-based responses and RNA 5-methylcytosine status. SaOS-2 cells were characterized by higher levels of superoxide and nitric oxide that promoted AKT and ERK1/2 activation thus modulating cell death pathways. OS cell lines also differed in the levels and localization of DNA repair regulator DNMT2/TRDMT1. SaOS-2 cells possessed the lowest levels of total, cytoplasmic and nuclear DNMT2/TRDMT1, whereas in MG-63 cells, the highest levels of nuclear DNMT2/TRDMT1 were associated with the most pronounced status of RNA 5-methylcytosine. In silico analysis revealed potential phosphorylation sites at DNMT2/TRDMT1 that may be related to the regulation of DNMT2/TRDMT1 localization. We postulate that redox homeostasis, proliferation-related pathways and DNMT2/TRDMT1-based effects can be modulated as a part of anti-osteosarcoma strategy reflecting diverse phenotypic features of OS cells.

Deficiency of TRDMT1 impairs exogenous RNA-based response and promotes retrotransposon activity during long-term culture of osteosarcoma cells.

TRDMT1 methyltransferase is postulated to be a novel target in anticancer therapy as TRDMT1-mediated RNA methylation is involved in DNA damage response (DDR) and TRDMT1 deficient cells are sensitive to PARP1 inhibitors. However, the effects of TRDMT1 gene knockout (KO) during cancer cell selection upon drug stimulation and the involvement of exogenous RNA were not addressed. In the present study, osteosarcoma (OS) cells lacking active TRDMT1 gene were subjected to short-term treatment of etoposide in the presence of exogenous RNA and long-term effects were analyzed after drug removal. Changes in cell proliferation and cell viability, genetic stability and DDR, telomere length and shelterin complex, retrotransposon activity and the levels of selected pro-inflammatory cytokines were considered. Long-term selection of TRDMT1 KO OS cells resulted in modified DDR, changes in telomere length and increased retrotransposon activity that was modulated by the addition of exogenous RNA. Thus, TRDMT1 gene KO may promote cellular and genetic heterogeneity that may modulate cancer cell responses to chemotherapeutic drugs.

Changes in γH2AX and H4K16ac levels are involved in the biochemical response to a competitive soccer match in adolescent players.

The aim of this study was to examine novel putative markers of the response to the competitive soccer match in adolescent players, such as changes in global levels of γH2AX and H4K16ac in the chromatin of peripheral mononuclear blood cells (PMBCs) and a Fourier-transform infrared spectroscopy (FTIR)-based biochemical fingerprint of serum. These characteristics were examined with reference to the physiological and metabolic aspects of this response. Immediately post-match we noticed: (1) a systemic inflammatory response, manifesting as peaks in leukocyte count and changes in concentrations of IL-6, TNFα, and cortisol; (2) a peak in plasma lactate; (3) onset of oxidative stress, manifesting as a decline in GSH/GSSG; (4) onset of muscle injury, reflected in an increase in CK activity. Twenty-four hours post-match the decrease in GSH/GSSG was accompanied by accumulation of MDA and 8-OHdG, macromolecule oxidation end-products, and an increase in CK activity. No changes in SOD1 or GPX1 levels were found. Repeated measures correlation revealed several associations between the investigated biomarkers. The FTIR analysis revealed that the match had the greatest impact on serum lipid profile immediately post-game. In turn, increases in γH2AX and H4K16ac levels at 24 h post-match indicated activation of a DNA repair pathway.

A Dual Face of APE1 in the Maintenance of Genetic Stability in Monocytes: An Overview of the Current Status and Future Perspectives.

Monocytes, which play a crucial role in the immune system, are characterized by an enormous sensitivity to oxidative stress. As they lack four key proteins responsible for DNA damage response (DDR) pathways, they are especially prone to reactive oxygen species (ROS) exposure leading to oxidative DNA lesions and, consequently, ROS-driven apoptosis. Although such a phenomenon is of important biological significance in the regulation of monocyte/macrophage/dendritic cells' balance, it also a challenge for monocytic mechanisms that have to provide and maintain genetic stability of its own DNA. Interestingly, apurinic/apyrimidinic endonuclease 1 (APE1), which is one of the key proteins in two DDR mechanisms, base excision repair (BER) and non-homologous end joining (NHEJ) pathways, operates in monocytic cells, although both BER and NHEJ are impaired in these cells. Thus, on the one hand, APE1 endonucleolytic activity leads to enhanced levels of both single- and double-strand DNA breaks (SSDs and DSBs, respectively) in monocytic DNA that remain unrepaired because of the impaired BER and NHEJ. On the other hand, there is some experimental evidence suggesting that APE1 is a crucial player in monocytic genome maintenance and stability through different molecular mechanisms, including induction of cytoprotective and antioxidant genes. Here, the dual face of APE1 is discussed.