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International audience; The persistence of cancer cells resistant to therapy remains a major clinical challenge. In triple-negative breast cancer, resistance to chemotherapy results in the highest recurrence risk among breast cancer subtypes. The drug-tolerant state seems largely defined by nongenetic features, but the underlying mechanisms are poorly understood. Here, by monitoring epigenomes, transcriptomes and lineages with single-cell resolution, we show that the repressive histone mark H3K27me3 (trimethylation of histone H3 at lysine 27) regulates cell fate at the onset of chemotherapy. We report that a persister expression program is primed with both H3K4me3 (trimethylation of histone H3 at lysine 4) and H3K27me3 in unchallenged cells, with H3K27me3 being the lock to its transcriptional activation. We further demonstrate that depleting H3K27me3 enhances the potential of cancer cells to tolerate chemotherapy. Conversely, preventing H3K27me3 demethylation simultaneously to chemotherapy inhibits the transition to a drug-tolerant state, and delays tumor recurrence in vivo. Our results highlight how chromatin landscapes shape the potential of cancer cells to respond to initial therapy.

SUMMARYDefects in double-strand repair mechanisms - both through germline or somatic inactivation of repair genes - is a hallmark of basal-like breast cancers. In this genetically-unstable context, a recurrent shift in cell identity occurs within the mammary epithelium. Basal-like tumors have indeed been proposed to originate from luminal progenitor (LP) cells yet tumor-initiating events remain poorly understood. Here, we map state transitions at the onset of basal-like tumorigenesis, using a Brca-1 deficient mouse model launching tumorigenesis in multiple LP cells. Combining single-cell transcriptomics to spatial multiplex imaging, we identify a population of cycling p16-expressing cells, emerging from the luminal progenitor compartment, undergoing partial epithelial-to-mesenchymal transition and losing luminal identity. Pseudo-temporal analyses position these cells as a transitory pre-tumoral state between aberrant Brca1-deficient luminal progenitors and growing tumor cells. In patients, the p16 pre-tumoral signature is found in early stage basal-like tumors, that rarely recur. Concomitant to p16 activation, we show that LP cells undergo an epigenomic crisis attested by the general re-organization of their heterochromatin. They accumulate multiple H3K27me3 micro-foci - reminiscent of the formation of senescence-associated heterochromatin foci (SAHFs) - and lose their inactive X (Xi). Both p16 activation and heterochromatin reorganization are hallmarks of human basal-like breast tumors; we propose that these events occur during initial LP transformation and are scars of an initial transitory senescent-like state.

Network meta-analysis was used to derive estimates of the relative efficacy of inclisiran, evolocumab, alirocumab, bempedoic acid, and ezetimibe in patients with hypercholesterolemia and/or at increased cardiovascular risk due to elevated low-density lipoprotein cholesterol taking maximum tolerated dose statins. Clinical trials published through February 2021 comparing percent change from baseline in low-density lipoprotein cholesterol were identified via a systematic review. Bayesian network meta-analyses were performed for patients with atherosclerotic cardiovascular disease and/or high cardiovascular risk on maximally tolerated statins in the base case, which included 23 trials. Results from the base-case analyses demonstrated that inclisiran, evolocumab, and alirocumab provide superior efficacy over placebo, bempedoic acid, and ezetimibe in terms of reduction in low-density lipoprotein cholesterol. Inclisiran was also comparable to alirocumab (mean difference: 0.78% [95% CrI: −8.35, 9.88]) and evolocumab (8.16%, [95% CrI: −1.82, 18.49]). Findings of a scenario which also included trials conducted in patients with heterozygous familial hypercholesterolemia were consistent with the base case. There was evidence of statistical heterogeneity across the included trials, roughly equivalent to variation of 5–10% change in low-density lipoprotein cholesterol, suggesting that any differences between treatments that were greater than 5–10% are generalizable. This study provides insight regarding the comparative efficacy of drugs for which no head-to-head trials exist and suggests that inclisiran, alirocumab, and evolocumab are expected to provide similar clinically meaningful improvements in low-density lipoprotein cholesterol in patients with hypercholesterolemia on maximally tolerated statins who are at increased cardiovascular risk.

Aims: Model how moving from current disease-modifying drug (DMD) prescribing patterns for relapsing-remitting multiple sclerosis (RRMS) observed in the United Kingdom (UK) to prescribing patterns based on patient preferences would impact health outcomes over time. Materials and methods: A cohort-based Markov model was used to measure the effect of DMDs on long-term health outcomes for individuals with RRMS. Data from a discrete choice experiment were used to estimate the market shares of DMDs based on patient preferences (i.e. preference shares). These preference shares and real-world UK market shares were used to calculate the effect of prescribing behavior on relapses, disability progression, and quality-adjusted life-years (QALYs). The incremental benefit of patient-centered prescribing over current practices for the UK RRMS population was then estimated; scenario and sensitivity analyses were also conducted. Results: Compared to current prescribing practices, when UK patients with RRMS were treated following patient preferences, health outcomes were improved. This population was expected to experience 501,690 relapses and gain 1,003,263 discounted QALYs over 50 years under patient-centered prescribing practices compared to 538,417 relapses and 958,792 discounted QALYs under current practices (−6.8% and +4.6%, respectively). Additionally, less disability progression was observed when prescribed treatment was based on patient preferences. In a scenario analysis where only oral treatments were considered, the results were similar, although the magnitude of benefit was smaller. Number of relapses was most sensitive to how the annualized relapse rate was modeled; disability progression was most sensitive to mortality rate assumptions. Limitations: Treatment efficacy estimates applied to various models in this study were based on data derived from clinical trials, rather than real-world data; the impact of patient-centered prescribing on treatment adherence and/or switching was not modeled. Conclusions: The population of UK RRMS patients may experience overall health gains if patient preferences are better incorporated into prescribing practices.

SUMMARYCD44 is a transmembrane glycoprotein that is linked to various biological processes reliant on the epigenetic plasticity of cells, including development, inflammation, immune responses, wound healing and cancer progression. While thoroughly studied, functional regulatory roles of this so-called ‘cell surface marker’ remain elusive. Here, we report the discovery that CD44 mediates endocytosis of iron interacting with hyaluronates in tumorigenic cell lines and primary cancer cells. We found that this glycan-mediated iron endocytosis mechanism is enhanced during epithelial-mesenchymal transition, unlike the canonical transferrin-dependent pathway. This transition is further characterized by molecular changes required for iron-catalyzed oxidative demethylation of the repressive histone mark H3K9me2 that governs the expression of mesenchymal genes.CD44itself is transcriptionally regulated by nuclear iron, demonstrating a positive feedback loop, which is in contrast to the negative regulation of transferrin receptor by excess iron. Finally, we show that epigenetic plasticity can be altered by interfering with iron homeostasis using small molecules. This comprehensive study reveals an alternative iron uptake mechanism that prevails in the mesenchymal state of mammalian cells, illuminating a central role of iron as a rate-limiting regulator of epigenetic plasticity.

Specimens produced from technically pure iron and two different heats of ferritic/martensitic steel T91 are investigated after exposure to oxygen-containing flowing lead–bismuth eutectic (LBE) at 400 °C, 10−7 mass% dissolved oxygen, and flow velocity of 2 m/s, for exposure times between around 1000 and 13,000 h. The occurring phenomena are analyzed and quantified using metallographic cross sections prepared after exposure. While pure iron mostly shows solution underneath or in the absence of a detached and buckled oxide scale, solution in T91 occurs only in a few spots on the sample surface. However, in the case of one of the investigated heats, a singular event of exceptionally severe solution-based corrosion is observed. The results are compared especially with findings at 450 and 550 °C and otherwise similar conditions as well as austenitic steels tested in the identical experimental run.