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Targeted protein degradation is a rapidly advancing and expanding therapeutic approach. Drugs that degrade GSPT1 via the [CRL4.sup.CRBN] ubiquitin ligase are a new class of cancer therapy in active clinical development with evidence of activity against acute myeloid leukemia in early-phase trials. However, other than activation of the integrated stress response, the downstream effects of GSPT1 degradation leading to cell death are largely undefined, and no murine models are available to study these agents. We identified the domains of GSPT1 essential for cell survival and show that GSPT1 degradation leads to impaired translation termination, activation of the integrated stress response pathway, and TP53-independent cell death. CRISPR/Cas9 screens implicated decreased translation initiation as protective following GSPT1 degradation, suggesting that cells with higher levels of translation are more susceptible to the effects of GSPT1 degradation. We defined 2 Crbn amino acids that prevent Gspt1 degradation in mice, generated a knockin mouse with alteration of these residues, and demonstrated the efficacy of GSPT1-degrading drugs in vivo with relative sparing of numbers and function of long-term hematopoietic stem cells. Our results provide a mechanistic basis for the use of GSPT1 degraders for the treatment of cancer, including TP53-mutant acute myeloid leukemia., Introduction The recent discovery of thalidomide analogs that degrade G1 to S phase transition 1 (GSPT1) via the [CRL4.sup.CRBN] ubiquitin ligase highlighted GSPT1 as a novel potential therapeutic target in [...]

The Drosophila trithorax group gene brahma (brm) encodes the ATPase subunit of a 2-MDa chromatinre-modeling complex, brm was identified in a screen for transcriptional activators of homeotic genes and subsequently shown to play a global role in transcription by RNA polymerase II. To gain insight into the targeting, function, and regulation of the BRM complex, we screened for mutations that genetically interact with a dominant-negative allele of brm ([brm.sup.H804R]). We first screened for dominant mutations that are lethal in combination with a [brm.sup.H804R] transgene under control of the brm promoter. In a distinct but related screen, we identified dominant mutations that modify eye defects resulting from expression of [brm.sup.H804R] in the eye-antennal imaginal disc. Mutations in three classes of genes were identified in our screens: genes encoding subunits of the BRM complex (brm, moira, and osa), other proteins directly involved in transcription (zerknullt and RpII140), and signaling molecules (Delta and vein). Expression of [brm.sup.H804R] in the adult sense organ precursor lineage causes phenotypes similar to those resulting from impaired DeltaNotch signaling. Our results suggest that signaling pathways may regulate the transcription of target genes by regulating the activity of the BRM complex.

Background: Multiple myeloma (MM) is an incurable hematologic malignancy requiring long‐term, continuous therapy. Despite its chronic and unrelenting course, studies examining quality of life (QOL), psychological distress, and perceptions of prognosis by line of therapy are lacking. Methods: The authors conducted a cross‐sectional, multisite study of patients undergoing treatment for MM (excluding maintenance) between June 2020 and January 2021. The authors conducted purposeful sampling and recruited patients to 3 cohorts based on lines of therapy: 1) newly diagnosed receiving first‐line therapy; 2) 2 to 3 lines; and 3) 4 or more lines. Patients completed validated questionnaires to assess their QOL, fatigue, psychological distress, and perceptions of prognosis. Results: A total of 180 patients with MM were enrolled (newly diagnosed [n = 60], 2 to 3 lines [n = 60], and ≥4 lines of therapy [n = 60]). QOL, symptom burden, and fatigue scores did not differ by lines of therapy. There were no statistically significant differences in psychological distress by line of therapy. The rates of clinically significant depression, anxiety, and post‐traumatic stress disorder symptoms were 23.9% (43 of 180), 23.9% (43 of 180), and 24.4% (44 of 180), respectively. Most patients (84.7%, 149 of 176) reported that their oncologist told them their cancer was incurable, but only 30.6% (53 of 173) acknowledged that they were terminally ill, and 42.0% (73 of 174) reported that they thought their cancer was incurable. Conclusions: Patients with MM undergoing treatment experience impaired QOL and elevated psychological distress across the disease continuum, regardless of line of therapy. A substantial proportion of patients with MM have significant misperceptions about their prognosis and the curability of their illness despite reporting being informed of the prognosis by their oncologist. Lay Summary: This study discusses 180 patients with MM (newly diagnosed [n = 60], 2‐3 lines [n = 60], and ≥4 lines of therapy [n = 60]). Quality of life, symptom burden, and fatigue scores do not differ by lines of therapy. There are also no statistically significant differences in psychological distress by line of therapy.The rates of clinically significant depression, anxiety, and post‐traumatic stress disorder symptoms are 23.9%, 23.9%, and 24.4%, respectively.Most patients (84.7%) report that their oncologist told them their cancer was incurable, but only 30.6% acknowledge that they are terminally ill, and 42.0% report that they thought their cancer was incurable. Patients with multiple myeloma undergoing treatment experience impaired quality of life and elevated psychological distress across the disease continuum. Although the majority reported that their oncologist had told them that their cancer is incurable, a substantial proportion still reported that they believed their cancer was curable. [ABSTRACT FROM AUTHOR]

In this issue of Cell Chemical Biology , Geng and colleagues employ a novel mouse model of humanized cereblon (Crbn) to provide insights into the immunomodulatory effects of lenalidomide and provide rationale for potential therapeutic combinations including anti-PD1 immunotherapy. [ABSTRACT FROM AUTHOR]

Background: Brief measures of physical function such as gait speed may be useful to optimize treatment intensity for older adults who have blood cancer; however, little is known about whether such assessments are already captured within oncologists' "gestalt" assessments. Methods: Gait speed was assessed in 782 patients ≥75 years of age who had blood cancer, with results reported to providers after treatment decisions were made; 408 patients required treatment when different intensities were available per National Comprehensive Cancer Network (NCCN) guidelines. We performed structured abstractions of treatment intensity recommendations into standard intensity, reduced intensity, or supportive care, based on NCCN guidelines. We modeled gait speed and survival using Cox regression and performed ordinal logistic regression to assess predictors of NCCN‐based categorizations of oncologists' treatment intensity recommendations, including gait speed. Results: The median survival by gait speed category was 10.8 months (<0.4 m/s), 18.6 months (0.4‐0.6 m/s), 34.0 months (0.6‐0.8 m/s), and unreached (>0.8 m/s). Univariable hazard ratios (HRs) for death increased for each lower category compared with ≥0.8 m/s (0.6‐0.8 m/s: HR, 1.76; 0.4‐0.6 m/s: HR, 2.30; <0.4 m/s: HR, 3.31). Gait speed predicted survival in multivariable Cox regression (all P <.05). In multivariable models including age, sex, and Eastern Cooperative Oncology Group performance status, gait speed did not predict oncologists' recommended treatment intensity (all P >.05) and did not add to a base model predicting recommended treatment intensity. Conclusion: In older adults with blood cancer who presented for treatment, gait speed predicted survival but not treatment intensity recommendation. Incorporating gait speed into decision making may improve optimal treatment selection. Gait speed predicts survival but not the intensity of recommended treatment in older adults with blood cancer. Incorporating gait speed into decision‐making may improve treatment selection. [ABSTRACT FROM AUTHOR]

Flipping the switch on T cells: Cell-based treatments such as chimeric antigen receptor (CAR) T cells have been finding increasing applications against cancer and other disorders. However, these treatments can have side effects, and it is difficult to stop the activity of an overactive cell-based therapy once it is inside a patient. To improve regulation of CAR T cell treatment, Jan et al. developed a switch-based system for activating and inactivating these cells. T cells with an OFF switch were deactivated using the drug lenalidomide, whereas those with an ON switch required both lenalidomide and a target antigen for activation, allowing control over the timing of T cell activation. Cell-based therapies are emerging as effective agents against cancer and other diseases. As autonomous "living drugs," these therapies lack precise control. Chimeric antigen receptor (CAR) T cells effectively target hematologic malignancies but can proliferate rapidly and cause toxicity. We developed ON and OFF switches for CAR T cells using the clinically approved drug lenalidomide, which mediates the proteasomal degradation of several target proteins by inducing interactions between the CRL4CRBN E3 ubiquitin ligase and a C2H2 zinc finger degron motif. We performed a systematic screen to identify "super-degron" tags with enhanced sensitivity to lenalidomide-induced degradation and used these degradable tags to generate OFF-switch degradable CARs. To create an ON switch, we engineered a lenalidomide-inducible dimerization system and developed split CARs that required both lenalidomide and target antigen for activation. Subtherapeutic lenalidomide concentrations controlled the effector functions of ON- and OFF-switch CAR T cells. In vivo, ON-switch split CARs demonstrated lenalidomide-dependent antitumor activity, and OFF-switch degradable CARs were depleted by drug treatment to limit inflammatory cytokine production while retaining antitumor efficacy. Together, the data showed that these lenalidomide-gated switches are rapid, reversible, and clinically suitable systems to control transgene function in diverse gene- and cell-based therapies. [ABSTRACT FROM AUTHOR]

PURPOSE: Conventional cytotoxic therapies increase the risk of clonal hematopoiesis and select for TP53 -mutant clones, which carry a high risk for transformation to therapy-related myelodysplastic neoplasms. In contrast, the effect of immune checkpoint blockade (ICB) on clonal hematopoiesis is unknown. METHODS: Paired peripheral-blood samples taken before and after treatment with ICB were obtained for 91 patients with either cutaneous melanoma or basal cell carcinoma. Error-corrected sequencing of a targeted panel of genes recurrently mutated in clonal hematopoiesis was performed on peripheral-blood genomic DNA. RESULTS: The average interval between acquisition of the paired samples was 180 days. Forty-one percent of the patients had clonal hematopoiesis at a variant allele frequency (VAF) > 0.01 in the pretreatment sample. There was near-complete agreement in the distribution and burden of clonal hematopoiesis mutations in the paired blood samples, with 87 of 88 mutations identified across the cohort present in paired samples, regardless of the duration between sample collection. The VAF in the paired samples also showed a high correlation, with an R 2 = 0.95 (P <.0001). In contrast to cytotoxic therapy, exposure to ICB did not lead to selection of TP53 - or PPM1D -mutant clones. However, consistent with the known effects of DNA-damaging therapy, we identified one patient who had eight unique TP53 mutations in the posttreatment blood sample after receiving two courses of radiation therapy. CONCLUSION: There was no expansion of hematopoietic clones or selection for clones at high risk for malignant transformation in patients who received ICB, observations that warrant further validation in larger cohorts. These findings highlight an important difference between ICB and conventional cytotoxic therapies and their respective impacts on premalignant genetic lesions. [ABSTRACT FROM AUTHOR]

The Saccharomyces cerevisiae protein Nhp6A is a model for the abundant and multifunctional high-mobility group B (HMGB) family of chromatin-associated proteins. Nhp6A binds DNA in vitro without sequence specificity and bends DNA sharply, but its role in chromosome biology is poorly understood. We show by whole-genome chromatin immunoprecipitation (ChIP) and high-resolution whole-genome tiling arrays (ChIP-chip) that Nhp6A is localized to specific regions of chromosomes that include ~23% of RNA polymerase II promoters. Nhp6A binding functions to stabilize nucleosomes, particularly at the transcription start site of these genes. Both genomic binding and transcript expression studies point to functionally related groups of genes that are bound specifically by Nhp6A and whose transcription is altered by the absence of Nhp6. Genomic analyses of Nhp6A mutants specifically defective in DNA bending reveal a critical role of DNA bending for stabilizing chromatin and coregulation of transcription but not for targeted binding by Nhp6A. We conclude that the chromatin environment, not DNA sequence recognition, localizes Nhp6A binding, and that Nhp6A stabilizes chromatin structure and coregulates transcription. [ABSTRACT FROM AUTHOR]

Nucleosome remodeling and covalent modifications of histones play fundamental roles in chromatin structure and function. However, much remains to be learned about how the action of ATP-dependent chromatin remodeling factors and histonemodifying enzymes is coordinated to modulate chromatin organization and transcription. The evolutionarily conserved ATP-dependent chromatin-remodeling factor ISWI plays essential roles in chromosome organization, DNA replication, and transcription regulation. To gain insight into regulation and mechanism of action of ISWI, we conducted an unbiased genetic screen to identify factors with which it interacts in vivo. We found that ISWI interacts with a network of factors that escaped detection in previous biochemical analyses, including the Sin3A gene. The Sin3A protein and the histone deacetylase Rpd3 are part of a conserved histone deacetylase complex involved in transcriptional repression. ISWI and the Sin3A/Rpd3 complex co-localize at specific chromosome domains. Loss of ISWI activity causes a reduction in the binding of the Sin3A/Rpd3 complex to chromatin. Biochemical analysis showed that the ISWI physically interacts with the histone deacetylase activity of the Sin3A/Rpd3 complex. Consistent with these findings, the acetylation of histone H4 is altered when ISWI activity is perturbed in vivo. These findings suggest that ISWI associates with the Sin3A/Rpd3 complex to support its function in vivo. [ABSTRACT FROM AUTHOR]

Multiple myeloma is an incurable plasma cell malignancy with a complex and incompletely understood molecular pathogenesis. Here we use whole-exome sequencing, copy-number profiling and cytogenetics to analyse 84 myeloma samples. Most cases have a complex subclonal structure and show clusters of subclonal variants, including subclonal driver mutations. Serial sampling reveals diverse patterns of clonal evolution, including linear evolution, differential clonal response and branching evolution. Diverse processes contribute to the mutational repertoire, including kataegis and somatic hypermutation, and their relative contribution changes over time. We find heterogeneity of mutational spectrum across samples, with few recurrent genes. We identify new candidate genes, including truncations of SP140, LTB, ROBO1 and clustered missense mutations in EGR1. The myeloma genome is heterogeneous across the cohort, and exhibits diversity in clonal admixture and in dynamics of evolution, which may impact prognostic stratification, therapeutic approaches and assessment of disease response to treatment.

The presence of hematologic malignancy-associated mutations in the blood of individuals without cytopenias or dysplasia has been termed clonal hematopoiesis of indeterminate potential (CHIP), a clinical entity associated with increased age, risk of developing hematologic malignancy, and decreased overall survival.1 Two papers in this issue of Blood take different approaches to advance our understanding of the frequency and clinical characteristics of clonal hematopoiesis. Zink et al analyze whole genome sequencing data from the blood of .11 000 healthy Icelandic individuals, and Buscarlet et al perform targeted sequencing on the blood of 2530 healthy older women. [ABSTRACT FROM AUTHOR]

Epidemiological studies show cigarette smoking enhances corneal endothelial dysfunction, but mechanisms remain unclear. Our study reveals that prolonged smoke exposure activates the aryl hydrocarbon receptor (AhR), increasing CYP1B1 expression and accelerating senescence and fibrosis in corneal endothelium, potentially reflecting adaptive responses to maintain corneal resilience. Although these molecular modifications indicate early endothelial dysfunction, no pathological changes were observed. The findings indicate that while chronic cigarette smoke exposure triggers initial molecular alterations and endothelial dysfunction, the progression to Fuchs endothelial corneal dystrophy likely requires additional environmental or genetic factors beyond smoke exposure alone. [ABSTRACT FROM AUTHOR]

Summary: Lysine 56 acetylation in the helical core of histone H3 opens yeast chromatin and enables histone gene transcription, DNA replication, and DNA repair and prevents epigenetic silencing. While K56Ac is globally abundant in yeast and flies, its presence has been uncertain in mammals. We show here using mass spectrometry and genome-wide analyses that K56Ac is present in human embryonic stem cells (hESCs), overlapping strongly at active and inactive promoters with the binding of the key regulators of pluripotency, NANOG, SOX2, and OCT4. This includes also the canonical histone gene promoters and those for the hESC-specific microRNAs. K56Ac then relocates to developmental genes upon cellular differentiation. Thus the K56Ac state more accurately reflects the epigenetic differences between hESCs and somatic cells than other active histone marks such as H3 K4 trimethylation and K9 acetylation. These results suggest that K56Ac is involved in the human core transcriptional network of pluripotency. [Copyright &y& Elsevier]