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Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype. Non-available targeted therapy for TNBC represents its biggest treatment challenge. Thus, finding new promising effective drugs is urgently needed. In the present study, we investigated how berberine, a natural isoquinoline, impairs the survival of TNBC cells in both cellular and molecular levels. Our experimental model was based on the use of eight TNBC cell lines: MDA-MB-468, MDA-MB-231, HCC70, HCC38, HCC1937, HCC1143, BT-20, and BT-549. Berberine was cytotoxic against all treated TNBC cell lines. The most sensitive cell lines were HCC70 (IC50 = 0.19 µM), BT-20 (IC50 = 0.23 µM) and MDA-MB-468 (IC50 = 0.48 µM). Using flow cytometry techniques, berberine, at 0.5 and 1 µM for 120 and 144 h, not only induced cell cycle arrest, at G1 and/or G2/M phases, but it also triggered significant apoptosis. At the molecular level, these results are consistent with the expression of their related proteins using Western blot assays. Interestingly, while berberine was cytotoxic against TNBC cells, it had no effect on the viability of normal human breast cells MCF10A cultured in a 3D matrigel model. These results suggest that berberine may be a good potential candidate for TNBC drug development.

Anti‐cancer drugs often increase reactive oxygen species (ROS) and cause DNA damage. Here, we highlight a new cross talk between chronic oxidative stress and the histone variant H2AX, a key player in DNA repair. We observe that persistent accumulation of ROS, due to a deficient JunD‐/Nrf2‐antioxidant response, reduces H2AX protein levels. This effect is mediated by an enhanced interaction of H2AX with the E3 ubiquitin ligase RNF168, which is associated with H2AX poly‐ubiquitination and promotes its degradation by the proteasome. ROS‐mediated H2AX decrease plays a crucial role in chemosensitivity. Indeed, cycles of chemotherapy that sustainably increase ROS reduce H2AX protein levels in Triple‐Negative breast cancer (TNBC) patients. H2AX decrease by such treatment is associated with an impaired NRF2‐antioxidant response and is indicative of the therapeutic efficiency and survival of TNBC patients. Thus, our data describe a novel ROS‐mediated regulation of H2AX turnover, which provides new insights into genetic instability and treatment efficacy in TNBC patients. Synopsis This work gives new insights into the regulation of H2AX protein turnover under chronic oxidative stress that affects DNA damage response. H2AX degradation upon chronic stress sensitizes tumour cells to chemotherapy and is indicative of better survival in triple‐negative breast cancer patients. Physiological conditions of chronic oxidative stress, mediated by the loss of JunD or Nrf2 transcription factors, are associated with a reduced protein level of the histone variant H2AX. Under conditions of chronic stress due to junD or Nrf2 deficiency, H2AX protein is targeted for degradation by the proteasome. ROS‐dependent H2AX degradation is mediated by enhanced interaction of H2AX protein with the E3 ubiquitin ligase RNF168. H2AX decrease by chronic oxidative stress increases tumour cell genomic instability and death. Chemosensitivity and survival of triple‐negative breast cancer patients are improved by stress‐mediated H2AX degradation following successive cycles of chemotherapy. Graphical Abstract This work gives new insights into the regulation of H2AX protein turnover under chronic oxidative stress that affects DNA damage response. H2AX degradation upon chronic stress sensitizes tumour cells to chemotherapy and is indicative of better survival in triple‐negative breast cancer patients.

Between 30% and 70% of patients with breast cancer have pre-existing chronic conditions, and more than half are on long-term non-cancer medication at the time of diagnosis. Preliminary epidemiological evidence suggests that some non-cancer medications may affect breast cancer risk, recurrence, and survival. In this nationwide cohort study, we assessed the association between medication use at breast cancer diagnosis and survival. We included 235,368 French women with newly diagnosed non-metastatic breast cancer. In analyzes of 288 medications, we identified eight medications positively associated with either overall survival or disease-free survival: rabeprazole, alverine, atenolol, simvastatin, rosuvastatin, estriol (vaginal or transmucosal), nomegestrol, and hypromellose; and eight medications negatively associated with overall survival or disease-free survival: ferrous fumarate, prednisolone, carbimazole, pristinamycin, oxazepam, alprazolam, hydroxyzine, and mianserin. Full results are available online from an interactive platform ( https://adrenaline.curie.fr ). This resource provides hypotheses for drugs that may naturally influence breast cancer evolution. Preliminary epidemiological evidence suggests that some non-cancer medications may affect breast cancer risk, recurrence, and survival. In this study, the authors utilized a nationwide database of breast cancer patients to estimate the association between frequently used drugs taken prior to diagnosis and breast cancer prognosis. And they identified 16 drugs associated with breast cancer outcomes.

Membrane type 1-matrix metalloproteinase (MT1-MMP), a membrane-tethered protease, is key for matrix breakdown during cancer invasion and metastasis. Assembly of branched actin networks by the Arp2/3 complex is required for MT1-MMP traffic and formation of matrix-degradative invadopodia. Contrasting with the well-established role of actin filament branching factor cortactin in invadopodia function during cancer cell invasion, the contribution of coronin-family debranching factors to invadopodia-based matrix remodeling is not known. Here, we investigated the contribution of coronin 1C to the invasive potential of breast cancer cells. We report that expression of coronin 1C is elevated in invasive human breast cancers, correlates positively with MT1-MMP expression in relation with increased metastatic risk and is a new independent prognostic factor in breast cancer. We provide evidence that, akin to cortactin, coronin 1C is required for invadopodia formation and matrix degradation by breast cancer cells lines and for 3D collagen invasion by multicellular spheroids. Using intravital imaging of orthotopic human breast tumor xenografts, we find that coronin 1C accumulates in structures forming in association with collagen fibrils in the tumor microenvironment. Moreover, we establish the role of coronin 1C in the regulation of positioning and trafficking of MT1-MMP-positive endolysosomes. These results identify coronin 1C as a novel player of the multi-faceted mechanism responsible for invadopodia formation, MT1-MMP surface exposure and invasiveness in breast cancer cells.

In this paper, we study non-isochoric models for mixtures of solid particles, at high volume concentration, and a gas. One of the motivations for this work concerns geophysics and more particularly the pyroclastic density currents, whose dense basal parts are precisely mixtures of pyroclasts and lithic fragments and air. They are extremely destructive phenomena, capable of devastating urbanised areas, and are known to propagate over long distances, even over almost flat topography. Fluidisation of these dense granular flows by pore gas pressure is one response that could explain this behaviour and must therefore be taken into account in the models. Starting from a solid–gas mixing model and invoking the compressibility of the gas through a law of state, we rewrite the conservation of mass equation of the gas phase into an equation of the pore gas pressure whose net effect is to reduce the friction between the particles. The momentum equation of the solid phase is completed by generic constitutive laws, specified as in Schaeffer et al. (J. Fluid Mech., vol. 874, 2019, pp. 926–951) by a yield function and a dilatancy function. Therefore, the divergence of the velocity field, which reflects the ability of the granular flow to expand or compress, depends on the volume fraction, pressure, strain rate and inertial number. In addition, we require the dilatancy function to describe the rate of volume change of the granular material near an isochoric equilibrium state, i.e. at constant volume. This property ensures that the volume fraction, which is the solution to the conservation of mass equation, is positive and finite at all times. We also require that the non-isochoric fluidised model be linearly stable and dissipate energy (over time). In this theoretical framework, we derive the dilatancy models corresponding to classical rheologies such as Drucker–Prager and $\\mu (I)$ (with or without expansion effects). The main result of this work is to show that it is possible to obtain non-isochoric and fluidised granular models satisfying all the properties necessary to correctly account for the physics of granular flows and which are well posed, at least linearly stable.

TNBC is a highly heterogeneous and aggressive breast cancer subtype associated with high relapse rates, and for which no targeted therapy yet exists. Protein arginine methyltransferase 5 (PRMT5), an enzyme which catalyzes the methylation of arginines on histone and non‐histone proteins, has recently emerged as a putative target for cancer therapy. Potent and specific PRMT5 inhibitors have been developed, but the therapeutic efficacy of PRMT5 targeting in TNBC has not yet been demonstrated. Here, we examine the expression of PRMT5 in a human breast cancer cohort obtained from the Institut Curie, and evaluate the therapeutic potential of pharmacological inhibition of PRMT5 in TNBC. We find that PRMT5 mRNA and protein are expressed at comparable levels in TNBC, luminal breast tumors, and healthy mammary tissues. However, immunohistochemistry analyses reveal that PRMT5 is differentially localized in TNBC compared to other breast cancer subtypes and to normal breast tissues. PRMT5 is heterogeneously expressed in TNBC and high PRMT5 expression correlates with poor prognosis within this breast cancer subtype. Using the small‐molecule inhibitor EPZ015666, we show that PRMT5 inhibition impairs cell proliferation in a subset of TNBC cell lines. PRMT5 inhibition triggers apoptosis, regulates cell cycle progression and decreases mammosphere formation. Furthermore, EPZ015666 administration to a patient‐derived xenograft model of TNBC significantly deters tumor progression. Finally, we reveal potentiation between EGFR and PRMT5 targeting, suggestive of a beneficial combination therapy. Our findings highlight a distinctive subcellular localization of PRMT5 in TNBC, and uphold PRMT5 targeting, alone or in combination, as a relevant treatment strategy for a subset of TNBC. Alternatives to current treatments are direly needed for patients with triple‐negative breast cancers (TNBC). The present study endorses PRMT5 as a novel therapeutic target in TNBC. PRMT5 pharmacological inhibition decreases viability in a subset of TNBC cell lines, mitigates early‐stage tumor progression in vivo, and displays additive/synergistic effects in combination with EGFR inhibition. Importantly, this study shows distinctive PRMT5 subcellular localization in TNBC, underlining the importance of site‐specific PRMT5 activity in the context of breast cancers.

Triple negative breast cancers (TNBCs) represent 15–20% of all breast cancers and are associated with higher recurrence and distant metastasis rate. Standard of care for early stage TNBC is anthracyclines combined with cyclophosphamide (AC) followed by taxanes, in the neo‐adjuvant or adjuvant setting. This work aimed to identify predictive biomarkers of AC response in patient‐derived xenograft (PDX) models of TNBC and to validate them in the clinical setting. By gene and protein expression analysis of 39 PDX with different responses to AC, we found that high expression of HORMAD1 was associated with better response to AC. Both gene and protein expression were associated with promoter hypomethylation. In a cohort of 526 breast cancer patients, HORMAD1 was overexpressed in 71% of TNBC. In a second cohort of 186 TNBC patients treated with AC, HORMAD1 expression was associated with longer metastasis‐free survival (MFS). In summary, HORMAD1 overexpression was predictive of an improved response to AC in PDX and is an independent prognostic factor in TNBC patients treated with AC.

Reverse phase protein array (RPPA) is a powerful dot-blot technology that allows studying protein expression levels as well as post-translational modifications in a large number of samples simultaneously. Yet, correct interpretation of RPPA data has remained a major challenge for its broad-scale application and its translation into clinical research. Satisfying quantification tools are available to assess a relative protein expression level from a serial dilution curve. However, appropriate tools allowing the normalization of the data for external sources of variation are currently missing. Here we propose a new method, called NormaCurve, that allows simultaneous quantification and normalization of RPPA data. For this, we modified the quantification method SuperCurve in order to include normalization for (i) background fluorescence, (ii) variation in the total amount of spotted protein and (iii) spatial bias on the arrays. Using a spike-in design with a purified protein, we test the capacity of different models to properly estimate normalized relative expression levels. The best performing model, NormaCurve, takes into account a negative control array without primary antibody, an array stained with a total protein stain and spatial covariates. We show that this normalization is reproducible and we discuss the number of serial dilutions and the number of replicates that are required to obtain robust data. We thus provide a ready-to-use method for reliable and reproducible normalization of RPPA data, which should facilitate the interpretation and the development of this promising technology. The raw data, the scripts and the normacurve package are available at the following web site: http://microarrays.curie.fr.

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer with high risk of relapse and metastasis. TNBC is a heterogeneous disease comprising different molecular subtypes including those with mesenchymal features. The tyrosine kinase AXL is expressed in mesenchymal cells and plays a role in drug resistance, migration and metastasis. We confirm that AXL is more expressed in mesenchymal TNBC cells compared to luminal breast cancer cells, and that its invalidation impairs cell migration while having no or little effect on cell viability. Here, we found that AXL controls directed migration. We observed that AXL displays a polarized localization at the Golgi apparatus and the leading edge of migratory mesenchymal TNBC cells. AXL co-localizes with F-actin at the front of the cells. In migratory polarized cells, the specific AXL inhibitor R428 displaces AXL and F-actin from the leading edge to a lateral area localized between the front and the rear of the cells where both are enriched in protrusions. In addition, R428 treatment disrupts the polarized localization of the Golgi apparatus towards the leading edge in migratory cells. Immunohistochemical analysis of aggressive chemo-resistant TNBC samples obtained before treatment reveals inter- and intra-tumor heterogeneity of the percentage of AXL expressing tumor cells, and a preference of these cells to be in contact with the stroma. Taken together, our study demonstrates that AXL controls directed cell migration most likely by regulating cell polarity.

ARHGAP21 is a Rho family GTPase‐activating protein (RhoGAP) that controls the Arp2/3 complex and F‐actin dynamics at the Golgi complex by regulating the activity of the small GTPase Cdc42. ARHGAP21 is recruited to the Golgi by binding to another small GTPase, ARF1. Here, we present the crystal structure of the activated GTP‐bound form of ARF1 in a complex with the Arf‐binding domain (ArfBD) of ARHGAP21 at 2.1 Å resolution. We show that ArfBD comprises a PH domain adjoining a C‐terminal α helix, and that ARF1 interacts with both of these structural motifs through its switch regions and triggers structural rearrangement of the PH domain. We used site‐directed mutagenesis to confirm that both the PH domain and the helical motif are essential for the binding of ArfBD to ARF1 and for its recruitment to the Golgi. Our data demonstrate that two well‐known small GTPase‐binding motifs, the PH domain and the α helical motif, can combine to create a novel mode of binding to Arfs.