NRF2 activation by cysteine as a survival mechanism for triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) is a very aggressive and heterogeneous group of tumors. In order to develop effective therapeutic strategies, it is therefore essential to identify the subtype-specific molecular mechanisms underlying disease progression and resistance to chemotherapy. TNBC cells are highly dependent on exogenous cystine, provided by overexpression of the cystine/glutamate antiporter SLC7A11/xCT, to fuel glutathione synthesis and promote an oxidative stress response consistent with their high metabolic demands. Here we show that TNBC cells of the mesenchymal stem-like subtype (MSL) utilize forced cystine uptake to induce activation of the transcription factor NRF2 and promote a glutathione-independent mechanism to defend against oxidative stress. Mechanistically, we demonstrate that NRF2 activation is mediated by direct cysteinylation of the inhibitor KEAP1. Furthermore, we show that cystine-mediated NRF2 activation induces the expression of important genes involved in oxidative stress response, but also in epithelial-to-mesenchymal transition and stem-like phenotype. Remarkably, in survival analysis, four upregulated genes (OSGIN1, RGS17, SRXN1, AKR1B10) are negative prognostic markers for TNBC. Finally, expression of exogenous OSGIN1, similarly to expression of exogenous NRF2, can prevent cystine depletion-dependent death of MSL TNBC cells. The results suggest that the cystine/NRF2/OSGIN1 axis is a potential target for effective treatment of MSL TNBCs.

Single-cell atlas of the aging mouse colon.

We performed massive single-cell sequencing in the aging mouse colonic epithelium and immune cells. We identified novel compartment-specific markers as well as dramatic aging-associated changes in cell composition and signaling pathways, including a shift from absorptive to secretory epithelial cells, depletion of naive lymphocytes, and induction of eIF2 signaling. Colon cancer is one of the leading causes of death within the western world, incidence of which increases with age. The colonic epithelium is a rapidly renewing tissue, tasked with water and nutrient absorption, as well as hosting intestinal microbes. The colonic submucosa is populated with immune cells interacting with and regulating the epithelial cells. However, it is unknown whether compartment-specific changes occur during aging and what impact this would cause. We show that both epithelial and immune cells differ significantly between colonic compartments and experience significant age-related changes in mice. We found a shift in the absorptive-secretory cell balance, possibly linked to age-associated intestinal disturbances, such as malabsorption. We demonstrate marked changes in aging immune cells: population shifts and interactions with epithelial cells, linking cytokines (Ifn-γ, Il1B) with the aging of colonic epithelium. Our results provide new insights into the normal and age-associated states of the colon.

Characterization of Novel α-Mangostin and Paeonol Derivatives With Cancer-Selective Cytotoxicity.

α-Mangostin (aMan) and Paeonol (Pae) have shown anticancer and anti-inflammatory properties. However, these two natural compounds have no clinical value because of their low solubility and low membrane permeability. In this study, we screened chemically synthesized derivatives from these two natural compounds as potential novel chemicals that increase cancer cell cytotoxicity over nontransformed human cells. We found that two derivative compounds, named α-Mangostin-1 (aMan1) and Paeonol-1 (Pae1) more efficiently and more specifically induced cytotoxicity in HCT116, HT29, and SW48 colorectal cancer cell lines than the parental compounds. Both aMan1 and Pae1 arrested HCT116 cells in the G1 phase and HT29 and SW48 cells in the G2-M phase of the cell cycle. Both aMan1 and Pae1 induced apoptosis in human colorectal cancer cells, through a caspase-dependent mechanism. aMan1 and Pae1 induced selective transcriptional responses in colorectal cancer cells involving genes related to metabolic stress and DNA damage response signaling pathways. Finally, experiments on primary colon organoids showed that both derivatives were able to kill cancer-derived organoids without affecting the viability of organoids derived from healthy tissue, where the parental compounds and the currently used chemotherapeutic drug irinotecan failed. In conclusion, our findings expand the knowledge of natural compound derivatives as anticancer agents and open new avenues of research in the derivation of lead compounds aimed at developing novel chemotherapeutic drugs for colorectal cancer treatment that selectively target cancer, but not healthy cells.

Establishment of a fluorescent reporter of RNA-polymerase II activity to identify dormant cells.

Dormancy, a reversible quiescent cellular state characterized by greatly reduced metabolic activity, protects from genetic damage, prolongs survival and is crucial for tissue homeostasis and cellular response to injury or transplantation. Dormant cells have been characterized in many tissues, but their identification, isolation and characterization irrespective of tissue of origin remains elusive. Here, we develop a live cell ratiometric fluorescent Optical Stem Cell Activity Reporter (OSCAR) based on the observation that phosphorylation of RNA Polymerase II (RNApII), a hallmark of active mRNA transcription elongation, is largely absent in dormant stem cells from multiple lineages. Using the small intestinal crypt as a model, OSCAR reveals in real time the dynamics of dormancy induction and cellular differentiation in vitro, and allows the identification and isolation of several populations of transcriptionally diverse OSCARhigh and OSCARlow intestinal epithelial cell states in vivo. In particular, this reporter is able to identify a dormant OSCARhigh cell population in the small intestine. OSCAR therefore provides a tool for a better understanding of dormant stem cell biology.

Antioxidant activity of gilan Mentha pulegium during growth.

Antioxidant activity and total phenolic contents of methanolic and hydroalcoholic-acetone extracts of Iranian Mentha pulegium in two stages of maturity were investigated. The aim was to investigate the most suitable solvent for extraction of antioxidants and to find the correlation existed between plant growth stage and its antioxidant capacity. In vitro antioxidant properties of the extracts were examined by 1, 1 diphenyl-2-picrylhydrazyl (DPPH) and Ferric Reducing/Antioxidant Power (FRAP) methods. Moreover, total phenolic contents were determined by the Folin-Ciocalteu method. On the other hand, the phenolic compounds were analyzed by chromatographic methods, TLC and SPE-reversed phase-HPLC. The results revealed that the antioxidant capacities and total phenol contents of the extracts in flowering season were higher than pre-flowering season. A positive relationship was found between the results obtained from three different assay methods used, i.e. FRAP, DPPH and phenol contents. The TLC chromatogram of the two extracts showed differences in the number of separated compounds of extracts. HPLC results indicated that the fraction collected with washing buffer (pH = 6) had highest antioxidant activity.