Inflammatory exposure drives long-lived impairment of hematopoietic stem cell self-renewal activity and accelerated aging.

Hematopoietic stem cells (HSCs) mediate regeneration of the hematopoietic system following injury, such as following infection or inflammation. These challenges impair HSC function, but whether this functional impairment extends beyond the duration of inflammatory exposure is unknown. Unexpectedly, we observed an irreversible depletion of functional HSCs following challenge with inflammation or bacterial infection, with no evidence of any recovery up to 1 year afterward. HSCs from challenged mice demonstrated multiple cellular and molecular features of accelerated aging and developed clinically relevant blood and bone marrow phenotypes not normally observed in aged laboratory mice but commonly seen in elderly humans. In vivo HSC self-renewal divisions were absent or extremely rare during both challenge and recovery periods. The progressive, irreversible attrition of HSC function demonstrates that temporally discrete inflammatory events elicit a cumulative inhibitory effect on HSCs. This work positions early/mid-life inflammation as a mediator of lifelong defects in tissue maintenance and regeneration.

Base editing sensor libraries for high-throughput engineering and functional analysis of cancer-associated single nucleotide variants.

Base editing can be applied to characterize single nucleotide variants of unknown function, yet defining effective combinations of single guide RNAs (sgRNAs) and base editors remains challenging. Here, we describe modular base-editing-activity 'sensors' that link sgRNAs and cognate target sites in cis and use them to systematically measure the editing efficiency and precision of thousands of sgRNAs paired with functionally distinct base editors. By quantifying sensor editing across >200,000 editor-sgRNA combinations, we provide a comprehensive resource of sgRNAs for introducing and interrogating cancer-associated single nucleotide variants in multiple model systems. We demonstrate that sensor-validated tools streamline production of in vivo cancer models and that integrating sensor modules in pooled sgRNA libraries can aid interpretation of high-throughput base editing screens. Using this approach, we identify several previously uncharacterized mutant TP53 alleles as drivers of cancer cell proliferation and in vivo tumor development. We anticipate that the framework described here will facilitate the functional interrogation of cancer variants in cell and animal models.

Senescence induction dictates response to chemo- and immunotherapy in preclinical models of ovarian cancer.

High-grade serous ovarian carcinoma (HGSOC) is a cancer with dismal prognosis due to the limited effectiveness of existing chemo- and immunotherapies. To elucidate mechanisms mediating sensitivity or resistance to these therapies, we developed a fast and flexible autochthonous mouse model based on somatic introduction of HGSOC-associated genetic alterations into the ovary of immunocompetent mice using tissue electroporation. Tumors arising in these mice recapitulate the metastatic patterns and histological, molecular, and treatment response features of the human disease. By leveraging these models, we show that the ability to undergo senescence underlies the clinically observed increase in sensitivity of homologous recombination (HR)-deficient HGSOC tumors to platinum-based chemotherapy. Further, cGas/STING-mediated activation of a restricted senescence-associated secretory phenotype (SASP) was sufficient to induce immune infiltration and sensitize HR-deficient tumors to immune checkpoint blockade. In sum, our study identifies senescence propensity as a predictor of therapy response and defines a limited SASP profile that appears sufficient to confer added vulnerability to concurrent immunotherapy and, more broadly, provides a blueprint for the implementation of electroporation-based mouse models to reveal mechanisms of oncogenesis and therapy response in HGSOC.

Safety and activity of selinexor in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents: a single-centre, single-arm, phase 2 trial.

BACKGROUND: The median overall survival of patients with high-risk myelodysplastic syndromes refractory to hypomethylating agents is less than 6 months. Currently, no standard therapy for such patients exists. Preclinical studies have shown that inhibition of the nuclear export protein exportin 1 (XPO1) causes nuclear accumulation of p53 and disruption of NF-κB signalling, both relevant targets for myelodysplastic syndromes. We therefore aimed to assess the safety and activity of selinexor in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents. METHODS: We did a single-centre, single-arm, phase 2 trial at the Memorial Sloan Kettering Cancer Center in the USA. We included patients 18 years or older with high-risk myelodysplastic syndromes or oligoblastic acute myeloid leukaemia (defined as blasts ≥20% but ≤30%) refractory to hypomethylating agents and with an Eastern Cooperative Oncology Group performance status score of 0-2. Eligible patients received 3-week long cycles of oral selinexor (60 mg twice per week for 2 weeks, followed by 1 week off). The primary outcome was overall response rate. Complete remission, partial remission, marrow complete remission, or haematological improvement were included in the response categories for assessing the primary endpoint. The activity analysis included all patients who completed at least one full-scheduled post-treatment disease assessment. All patients who were given selinexor were included in the safety analysis. This study is registered with ClinicalTrials.gov, NCT02228525. FINDINGS: Between Sept 23, 2014, and March 13, 2018, 25 patients were enrolled on this study. The median follow-up was 8·5 months (IQR 3·1-12·2). Two patients did not meet the full eligibility criteria after baseline assessment; therefore, 23 patients were evaluable for activity assessment. In the 23 evaluable patients, overall response rate was 26% (95% CI 10-48) in six patients with marrow complete remission, with an additional 12 patients (52%, 95% CI 31-73) achieving stable disease. The most common grade 3 or 4 adverse events were thrombocytopenia (eight [32%] of 25 patients) and hyponatraemia (five [20%]). There were no drug-related serious adverse events and no treatment-related deaths. INTERPRETATION: Selinexor showed responses in patients with myelodysplastic syndromes or oligoblastic acute myeloid leukaemia refractory to hypomethylating agents. Adverse events were manageable with supportive care implementation. Further studies are needed to compare selinexor with supportive care alone, and to identify patient subgroups that might benefit the most from selinexor treatment. FUNDING: Karyopharm Therapeutics.

Perception of the 2020 SARS-CoV-2 pandemic among medical professionals in Germany: results from a nationwide online survey.

Background: The COVID-19 pandemic represents an unprecedented global challenge and implicates a wide range of burden on medical professionals. Here, we evaluated the perception of the COVID-19 pandemic among medical professionals in Germany. Methods: A total of n = 2827 medical professionals participated in an online survey between 27 March and 11 April. Results: While most participants stated that Germany was well prepared and rated the measures taken by their employer as positive, subgroup analyses revealed decisive differences. The preventive measures were rated significantly worse by nurses compared to doctors (p < 0.001) and by participants from ambulatory healthcare centres compared to participants from maximum-care hospitals (p < 0.001). Importantly, shortage of protective medical equipment was reported more commonly in the ambulatory sector (p < 0.001) and in East German federal states (p = 0.004). Moreover, the majority of health care professionals (72.4%) reported significant restrictions of daily work routine. Finally, over 60% of medical professionals had concerns regarding their own health, which were more pronounced among female participants (p = 0.024). Conclusion: This survey may indicate starting points on how medical professionals could be supported in carrying out their important activities during the ongoing and future healthcare challenges.

Oncogenic Role of Fusion-circRNAs Derived from Cancer-Associated Chromosomal Translocations.

Chromosomal translocations encode oncogenic fusion proteins that have been proven to be causally involved in tumorigenesis. Our understanding of whether such genomic alterations also affect non-coding RNAs is limited, and their impact on circular RNAs (circRNAs) has not been explored. Here, we show that well-established cancer-associated chromosomal translocations give rise to fusion circRNAs (f-circRNA) that are produced from transcribed exons of distinct genes affected by the translocations. F-circRNAs contribute to cellular transformation, promote cell viability and resistance upon therapy, and have tumor-promoting properties in in vivo models. Our work expands the current knowledge regarding molecular mechanisms involved in cancer onset and progression, with potential diagnostic and therapeutic implications.

The dark matter of the cancer genome: aberrations in regulatory elements, untranslated regions, splice sites, non-coding RNA and synonymous mutations.

Cancer is a disease of the genome caused by oncogene activation and tumor suppressor gene inhibition. Deep sequencing studies including large consortia such as TCGA and ICGC identified numerous tumor-specific mutations not only in protein-coding sequences but also in non-coding sequences. Although 98% of the genome is not translated into proteins, most studies have neglected the information hidden in this "dark matter" of the genome. Malignancy-driving mutations can occur in all genetic elements outside the coding region, namely in enhancer, silencer, insulator, and promoter as well as in 5'-UTR and 3'-UTR Intron or splice site mutations can alter the splicing pattern. Moreover, cancer genomes contain mutations within non-coding RNA, such as microRNA, lncRNA, and lincRNA A synonymous mutation changes the coding region in the DNA and RNA but not the protein sequence. Importantly, oncogenes such as TERT or miR-21 as well as tumor suppressor genes such as TP53/p53, APC, BRCA1, or RB1 can be affected by these alterations. In summary, coding-independent mutations can affect gene regulation from transcription, splicing, mRNA stability to translation, and hence, this largely neglected area needs functional studies to elucidate the mechanisms underlying tumorigenesis. This review will focus on the important role and novel mechanisms of these non-coding or allegedly silent mutations in tumorigenesis.