Gastric SMARCA4-deficient undifferentiated tumor (SMARCA4-UT): a clinicopathological analysis of four rare cases.

BACKGROUND: SMARCA4, as one of the subunits of the SWI/SNF chromatin remodeling complex, drives SMARCA4-deficient tumors. Gastric SMARCA4-deficient tumors may include gastric SMARCA4-deficient carcinoma and gastric SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Gastric SMARCA4-UT is rare and challenging to diagnose in clinical practice. The present report aims to provide insight into the clinicopathological characteristics and genetic alterations of gastric SMARCA4-UTs. RESULTS: We retrospectively reported four rare cases of gastric SMARCA4-UTs. All four cases were male, aged between 61 and 82 years. These tumors presented as ulcerated and transmural masses with infiltration, staged as TNM IV in cases 1, 2 and 4, and TNM IIIA in case 3. Pathologically, four cases presented solid architecture with undifferentiated morphology. Cases 2 and 3 showed focal necrosis and focal rhabdoid morphology. Immunohistochemical staining showed negative expression of epithelial markers and deficient expression of SMARCA4. Furthermore, positivity for Syn (cases 1, 2 and 3) and SALL4 (cases 1 and 2) were observed. Mutant p53 expression occurred in four cases, resulting in strong and diffuse staining of p53 expression in cases 1, 2 and 4, and complete loss in case 3. The Ki67 proliferative index exceeded 80%. 25% (1/4, case 4) of cases had mismatch repair deficiency (dMMR). Two available cases (cases 1 and 3) were detected with SMRACA4 gene alterations. The response to neoadjuvant therapy was ineffective in case 1. CONCLUSIONS: Gastric SMARCA4-UT is a rare entity of gastric cancer with a poor prognosis, predominantly occurs in male patients. The tumors are typically diagnosed at advanced stages and shows a solid architecture with undifferentiated morphology. Negative expression of epithelial markers and complete loss of SMARCA4 immunoexpression are emerging as a useful diagnostic tool for rare gastric SMARCA4-UTs.

Successful treatment with tislelizumab plus chemotherapy for SMARCA4-deficient undifferentiated tumor: a case report.

SMARCA4-deficient undifferentiated tumor (SMARCA4-dUT) is a devastating subtype of thoracic tumor with SMARCA4 inactivation and is characterized by rapid progression, poor prognosis, and high risk of postoperative recurrence. However, effective treatments for SMARCA4-dUT are lacking. Herein, we describe a patient with SMARCA4-dUT who exhibited an impressive response to the anti-programmed cell death protein-1 (PD-1) antibody (tislelizumab) in combination with conventional chemotherapy (etoposide and cisplatin). To the best of our knowledge, this is the first case of SMARCA4-dUT treated with chemotherapy, comprising etoposide and cisplatin, combined with anti-PD-1 inhibitors. Immunotherapy combined with etoposide and cisplatin may be a promising strategy to treat SMARCA4-dUT.

Marked Response to Nivolumab by a Patient With SMARCA4-Deficient Undifferentiated Urothelial Carcinoma Showing High PD-L1 Expression: A Case Report.

BACKGROUND: SMARCA4 is a component gene of the SWI/SNF (SWItch/Sucrose NonFermentable) chromatin remodeling complex; undifferentiated tumors associated with its functional deletion have been described in several organs. However, no established treatment for these tumors currently exists. CASE: In this study, we report a case of a SMARCA4-deficient undifferentiated urothelial carcinoma with high PD-L1 expression that was effectively treated with nivolumab after early relapse following treatment for non-invasive bladder cancer. The histological morphology of the rhabdoid-like undifferentiated tumor of unknown primary led us to suspect a SWI/SNF-deficient tumor, and subsequent immunostaining led to the diagnosis of a SMARCA4-deficient undifferentiated tumor. This effort also led to the identification of the developmental origin of this SMARCA4-deficient undifferentiated tumor as a non-invasive bladder cancer. We also carried out a detailed immune phenotypic assay on peripheral T cells. In brief, a phenotypic change of CD8+T cells from naive to terminally differentiated effector memory cells was observed. CONCLUSION: Regardless of the organ of cancer origin or cancer type, SWI/SNF-deficient tumors should be suspected in undifferentiated and dedifferentiated tumors, and immune checkpoint inhibitors may be considered as a promising treatment option for this type of tumor. The pathogenesis of SMARCA4-deficient anaplastic tumors awaits further elucidation for therapeutic development.

Epicardial SMARCA4 deletion exacerbates cardiac injury in myocardial infarction and is related to the inhibition of epicardial epithelial-mesenchymal transition.

The reactivated adult epicardium produces epicardium-derived cells (EPDCs) via epithelial-mesenchymal transition (EMT) to benefit the recovery of the heart after myocardial infarction (MI). SMARCA4 is the core catalytic subunit of the chromatin re-modeling complex, which has the potential to target some reactivated epicardial genes in MI. However, the effects of epicardial SMARCA4 on MI remain uncertain. This study found that SMARCA4 was activated over time in epicardial cells following MI, and some of activated cells belonged to downstream differentiation types of EPDCs. This study used tamoxifen to induce lineage tracing and SMARCA4 deletion from epicardial cells in Wt1-CreER;Smarca4fl/fl;Rosa26-RFP adult mice. Epicardial SMARCA4 deletion reduces the number of epicardial cells in adult mice, which was related to changes in the activation, proliferation, and apoptosis of epicardial cells. Epicardial SMARCA4 deletion reduced collagen deposition and angiogenesis in the infarcted area, exacerbated cardiac injury in MI. The exacerbation of cardiac injury was related to the inhibition of generation and differentiation of EPDCs. The alterations in EPDCs were associated with inhibited transition between E-CAD and N-CAD during the epicardial EMT, coupled with the down-regulation of WT1, SNAIL1, and PDGF signaling. In conclusion, this study suggests that Epicardial SMARCA4 plays a critical role in cardiac injury caused by MI, and its regulatory mechanism is related to epicardial EMT. Epicardial SMARCA4 holds potential as a novel molecular target for treating MI.

Rare SMARCA4-deficient thoracic tumor: Insights into molecular characterization and optimal therapeutics methods.

INTRODUCTIONS: The 2021 WHO Classification of Thoracic Tumors recognized SMARCA4-deficient undifferentiated thoracic tumors (SMARCA4-dUT) as a distinct entity that shows a striking overlap in demographic and molecular profiles with SMARCA4-deficient non-small lung cancer (SMARCA4-dNSCLC). The implications of SMARCA4 deficiency based on immunohistochemistry remain unclear. We aimed to investigate molecular characteristics of SMARCA4-deficient thoracic tumors (SDTT) and explore optimal therapeutics. METHODS: From June.15, 2018, to Nov.15, 2023, a large cohort including patients diagnosed with SMARCA4-deficient (N = 196) and SMARCA4-intact (N = 438) thoracic tumors confirmed by immunohistochemistry at SYSUCC were screened. Clinicopathologic and molecular characteristics were identified and compared. External SRRSH cohort (N = 34) was combined into a pooled cohort to compare clinical outcome of first-line therapy efficacy. RESULTS: SDTT is male predominance with smoking history, high tumor burden, and adrenal metastases. The relationship between SMARCA4 mutation and protein expression is not completely parallel. The majority of SMARCA4-deficient patients harbor truncating (Class-I) SMARCA4 mutations, whereas class-II alterations and wild-type also exist. Compared with SMARCA4-intact thoracic tumors, patients with SDTT displayed a higher tumor mutation burden (TMB) and associated with a shorter median OS (16.8 months vs. Not reached; P < 0.001). Notably, SMARCA4 protein deficiency, rather than genetic mutations, played a decisive role in these differences. SDTT is generally resistant to chemotherapy, while sensitive to chemoimmunotherapy (median PFS: 7.5 vs. 3.5 months, P < 0.001). In particular, patients with SMARCA4 deficient thoracic tumors treated with paclitaxel-based chemoimmunotherapy achieved a longer median PFS than those with pemetrexed-based chemoimmunotherapy (10.0 vs. 7.3 months, P = 0.028). CONCLUSIONS: SMARCA4 protein deficiency, rather than genetic mutations, played a decisive role in its characteristics of higher TMB and poor prognosis. Chemoimmunotherapy serves as the optimal option in the current treatment regimen. Paclitaxel-based chemoimmunotherapy performed better than those with pemetrexed-based chemoimmunotherapy.

SMARCA4 deficiency and mutations are frequent in large cell lung carcinoma and are prognostically significant.

SMARCA4 mutation has emerged as a marker of poor prognosis in lung cancer and has potential predictive value in cancer treatment, but recommendations for which patients require its investigation are lacking. We comprehensively studied SMARCA4 alterations and the clinicopathological significance in a large cohort of immunohistochemically-subtyped non-small cell lung cancer (NSCLC). A total of 1416 patients was studied for the presence of SMARCA4 deficiency by immunohistochemistry (IHC). Thereafter, comprehensive sequencing of tumours was performed for 397 of these patients to study the mutational spectrum of SWI/SNF and SMARCA4 aberrations. IHC evidence of SMARCA4 deficiency was found in 2.9% of NSCLC. Of the sequenced tumours, 38.3% showed aberration in SWI/SNF complex, and 9.3% had SMARCA4 mutations. Strikingly, SMARCA4 aberrations were much more prevalent in large cell carcinoma (LCC) than other histological tumour subtypes. SMARCA4-deficient and SMARCA4-mutated tumours accounted for 40.5% and 51.4% of all LCC, respectively. Multivariable analyses confirmed SMARCA4 mutation was an independent prognostic factor in lung cancer. The immunophenotype of a subset of these tumours frequently showed TTF1 negativity and HepPAR1 positivity. SMARCA4 mutation or its deficiency was associated with positive smoking history and poor prognosis. It also demonstrated mutual exclusion with EGFR mutation. Taken together, the high incidence of SMARCA4 aberrations in LCC may indicate its diagnostic and prognostic value. Our study established the necessity of SMARCA4 IHC in the identification of SMARCA4-aberrant tumours, and this may be of particular importance in LCC and tumours without known driver events.

All That Is Small Is Not a Small-Cell Carcinoma: Thoracic SMARCA4-Deficient Undifferentiated Tumors Masquerading as SCLC.

Small-cell lung carcinoma (SCLC) cell lines have been widely utilized as a preclinical model of this highly aggressive disease. However, since their creation decades ago, novel tumor entities have been defined that might clinicopathologically mimic SCLC, which notably includes thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). Multiomic reassessment of the presumed SCLC cell lines with high YAP1 expression reveals that nearly all of these tumors represent unsuspected SMARCA4-UT. See related article by Ng et al., p. 1846.

Under the Microscope: A Case Report of Thoracic SMARCA4-Deficient Undifferentiated Tumor with Review of the Literature.

OBJECTIVE: SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a highly malignant neoplasm with an undifferentiated or rhabdoid phenotype, posing a diagnostic challenge. This case report aims to create awareness about this rare neoplasm while dealing with cases presenting with undifferentiated morphology. CASE REPORT: A 55-year-old gentleman with constitutional symptoms and lymphadenopathy. Imaging revealed a mass lesion in the right upper lobe of the lung. A biopsy of the cervical lymph node showed diffusely effaced architecture replaced by sheets of undifferentiated pleomorphic cells with vesicular nuclei, prominent nucleoli, eosinophilic cytoplasm, and multiple necrotic foci. An extensive immunohistochemistry (IHC) panel was applied, which showed positivity for synaptophysin, vimentin, and focal CD34 and EMA expression. Other markers like pan-cytokeratin, p40, TTF1, CD56, INSM1, calretinin, CD45, SOX10, S100, CD30, CD117, SMA, and Desmin were negative, with INI1 retained. The IHC panel excluded the morphological differentials of carcinoma, lymphoma, rhabdomyosarcoma, melanoma, and germ cell tumor. Further literature review led to the possibility of the SMARCA4-UT entity, which had a morphology and IHC profile similar to the present case. Testing for SMARCA4 (BRG-1) by IHC showed a complete loss in the tumor cells, favoring the diagnosis of Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT). CONCLUSION: SMARCA4-UTs are rare, highly aggressive, and poorly differentiated thoracic tumors. Recognizing them is vital as there is potential for therapeutic interventions such as immunotherapy and SMARCA4-targeted therapies, offering promising prospects for the future.

SMARCA4 / BRG1 -deficient Uterine Neoplasm With Hybrid Adenosarcoma and Carcinoma Features: Expanding the Molecular-morphologic Spectrum of SMARCA4 -driven Gynecologic Malignancies.

SMARCA4 gene encodes BRG1 , a member of the SWItch/sucrose non-fermentable protein family involved in epigenetic transcriptional regulation of important cellular processes. In the uterine corpus, SMARCA4 / BRG1 deficiency is associated with a novel class of undifferentiated uterine sarcomas, characterized by younger age onset, rhabdoid histology, focal phyllodiform architecture, high-risk pathologic findings, and dismal prognosis. Herein, we report a case of a 34-year-old Asian woman with a SMARCA4 / BRG1 -deficient uterine tumor fulfilling the clinicopathologic features of an undifferentiated uterine sarcoma. However, the tumor exhibited several unique features that have not been previously emphasized, including (1) conspicuous phyllodiform architecture recapitulating conventional adenosarcoma, (2) rhabdoid tumor cells forming cords and keratin-positive cohesive epithelial islands, and (3) cooccurrence with a spatially distinct and discrete endometrial complex atypical hyperplasia from the rest of the proliferation. By immunohistochemistry, the tumor cells were diffusely positive for synaptophysin, whereas BRG1 was lost. Pertinent molecular findings included frameshift mutations in the SMARCA4 gene, mutations in histone modification and chromatin remodeling genes, including KMT2C , ARID1B , KAT6A , and NCOR1 , and mutations in Wnt signaling involving APC and CTNNB1 . Copy number gain in MDM2 and CDK4 were also identified. The tumor mutation burden was intermediate (6.8/MB) and it was microsatellite stable. On balance, our case exhibited morphologic and molecular features that overlap with (1) an undifferentiated uterine sarcoma, (2) an adenosarcoma with sarcomatous overgrowth, and (3) a mixed adenosarcoma and undifferentiated endometrial carcinoma. These hybrid features further expand the molecular-morphologic spectrum of SMARCA4 / BRG1 -deficient uterine neoplasms.

Partial RAG deficiency in humans induces dysregulated peripheral lymphocyte development and humoral tolerance defect with accumulation of T-bet+ B cells.

The recombination-activating genes (RAG) 1 and 2 are indispensable for diversifying the primary B cell receptor repertoire and pruning self-reactive clones via receptor editing in the bone marrow; however, the impact of RAG1/RAG2 on peripheral tolerance is unknown. Partial RAG deficiency (pRD) manifesting with late-onset immune dysregulation represents an 'experiment of nature' to explore this conundrum. By studying B cell development and subset-specific repertoires in pRD, we demonstrate that reduced RAG activity impinges on peripheral tolerance through the generation of a restricted primary B cell repertoire, persistent antigenic stimulation and an inflammatory milieu with elevated B cell-activating factor. This unique environment gradually provokes profound B cell dysregulation with widespread activation, remarkable extrafollicular maturation and persistence, expansion and somatic diversification of self-reactive clones. Through the model of pRD, we reveal a RAG-dependent 'domino effect' that impacts stringency of tolerance and B cell fate in the periphery.

Immune-Desert Tumor Microenvironment in Thoracic SMARCA4-Deficient Undifferentiated Tumors with Limited Efficacy of Immune Checkpoint Inhibitors.

BACKGROUND: Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UT) are aggressive neoplasms. Data linking BAF alterations with tumor microenvironment (TME) and efficacy of immune checkpoint inhibitors (ICI) are contradictory. The TME of SMARCA4-UT and their response to ICI are unknown. MATERIALS AND METHODS: Patients diagnosed with SMARCA4-UT in our institution were included. Immunostainings for tertiary lymphoid structures (TLS), immune cell markers, and checkpoints were assessed. Validation was performed using an independent transcriptome dataset including SMARCA4-UT, non-small cell lung cancers (NSCLC) with/without SMARCA4 mutations, and unclassified thoracic sarcomas (UTS). CXCL9 and PD-L1 expressions were assessed in NSCLC and thoracic fibroblast cell lines, with/without SMARCA4 knockdown, treated with/without interferon gamma. RESULTS: Nine patients were identified. All samples but one showed no TLS, consistent with an immune desert TME phenotype. Four patients received ICI as part of their treatment, but the only one who responded, had a tumor with a TLS and immune-rich TME. Unsupervised clustering of the validation cohort using immune cell scores identified 2 clusters associated with cell ontogeny and immunity (cluster 1 enriched for NSCLC independently of SMARCA4 status (n = 9/10; P = .001); cluster 2 enriched for SMARCA4-UT (n = 11/12; P = .005) and UTS (n = 5/5; P = .0005). SMARCA4 loss-of-function experiments revealed interferon-induced upregulation of CXCL9 and PD-L1 expression in the NSCLC cell line with no effect on the thoracic fibroblast cell line. CONCLUSION: SMARCA4-UT mainly have an immune desert TME with limited efficacy to ICI. TME of SMARCA4-driven tumors varies according to the cell of origin questioning the interplay between BAF alterations, cell ontogeny and immunity.

Loss of SET1/COMPASS methyltransferase activity reduces lifespan and fertility in Caenorhabditis elegans.

Changes in histone post-translational modifications are associated with aging through poorly defined mechanisms. Histone 3 lysine 4 (H3K4) methylation at promoters is deposited by SET1 family methyltransferases acting within conserved multiprotein complexes known as COMPASS. Previous work yielded conflicting results about the requirement for H3K4 methylation during aging. Here, we reassessed the role of SET1/COMPASS-dependent H3K4 methylation in Caenorhabditis elegans lifespan and fertility by generating set-2(syb2085) mutant animals that express a catalytically inactive form of SET-2, the C. elegans SET1 homolog. We show that set-2(syb2085) animals retain the ability to form COMPASS, but have a marked global loss of H3K4 di- and trimethylation (H3K4me2/3). Reduced H3K4 methylation was accompanied by loss of fertility, as expected; however, in contrast to earlier studies, set-2(syb2085) mutants displayed a significantly shortened, not extended, lifespan and had normal intestinal fat stores. Other commonly used set-2 mutants were also short-lived, as was a cfp-1 mutant that lacks the SET1/COMPASS chromatin-targeting component. These results challenge previously held views and establish that WT H3K4me2/3 levels are essential for normal lifespan in C. elegans.

Characterization of Poldip2 knockout mice: Avoiding incorrect gene targeting.

POLDIP2 is a multifunctional protein whose roles are only partially understood. Our laboratory previously reported physiological studies performed using a mouse gene trap model, which suffered from three limitations: perinatal lethality in homozygotes, constitutive Poldip2 inactivation and inadvertent downregulation of the adjacent Tmem199 gene. To overcome these limitations, we developed a new conditional floxed Poldip2 model. The first part of the present study shows that our initial floxed mice were affected by an unexpected mutation, which was not readily detected by Southern blotting and traditional PCR. It consisted of a 305 kb duplication around Poldip2 with retention of the wild type allele and could be traced back to the original targeted ES cell clone. We offer simple suggestions to rapidly detect similar accidents, which may affect genome editing using both traditional and CRISPR-based methods. In the second part of the present study, correctly targeted floxed Poldip2 mice were generated and used to produce a new constitutive knockout line by crossing with a Cre deleter. In contrast to the gene trap model, many homozygous knockout mice were viable, in spite of having no POLDIP2 expression. To further characterize the effects of Poldip2 ablation in the vasculature, RNA-seq and RT-qPCR experiments were performed in constitutive knockout arteries. Results show that POLDIP2 inactivation affects multiple cellular processes and provide new opportunities for future in-depth study of its functions.

SMARCA4-Deficient Carcinoma of Uterine Cervix Resembling SCCOHT-Case Report.

Small cell carcinoma of hypercalcemic type (SCCOHT) is a rare gynaecological neoplasm, originating mostly in the ovaries. Cervical origin of this very aggressive malignancy with unknown histogenesis is an extremely rare condition, without published management recommendations. Alterations in SMARCA4 gene are supposed to play the major role in SCCOHT oncogenesis and their identification is crucial for the diagnosis. Adequate genetic counselling of the patients and their families seems to be of great importance. Optimal management and treatment approaches are not known yet but may extremely influence the prognosis of young female patients that suffer from this very resistant disease. Nowadays, a translational research seems to be the key for the further diagnostic and treatment strategies of SCCOHT. The purpose of the case report is to provide practical information and useful recommendations on the diagnosis, management, and treatment of SMARCA4-deficient carcinoma of the uterine cervix resembling SCCOHT.

Spatiotemporal coordination of the RSF1-PLK1-Aurora B cascade establishes mitotic signaling platforms.

The chromatin remodeler RSF1 enriched at mitotic centromeres is essential for proper chromosome alignment and segregation and underlying mechanisms remain to be disclosed. We here show that PLK1 recruitment by RSF1 at centromeres creates an activating phosphorylation on Thr236 in the activation loop of Aurora B and this is indispensable for the Aurora B activation. In structural modeling the phosphorylated Thr236 enhances the base catalysis by Asp200 nearby, facilitating the Thr232 autophosphorylation. Accordingly, RSF1-PLK1 is central for Aurora B-mediated microtubule destabilization in error correction. However, under full microtubule-kinetochore attachment RSF1-PLK1 positions at kinetochores, halts activating Aurora B and phosphorylates BubR1, regardless of tension. Spatial movement of RSF1-PLK1 to kinetochores is triggered by Aurora B-mediated phosphorylation of centromeric histone H3 on Ser28. We propose a regulatory RSF1-PLK1 axis that spatiotemporally controls on/off switch on Aurora B. This feedback circuit among RSF1-PLK1-Aurora B may coordinate dynamic microtubule-kinetochore attachment in early mitosis when full tension yet to be generated.

Mesenchymal/non-epithelial mimickers of neuroendocrine neoplasms with a focus on fusion gene-associated and SWI/SNF-deficient tumors.

Mimickers of neuroendocrine neoplasms (NEN) include a number of important pitfall tumors. Here, we describe our experience with mesenchymal mimics of NENs to illustrate their spectrum and draw the attention particularly to a group of mesenchymal/non-epithelial neoplasms (MN) that combine epithelioid histology with neuroendocrine (NE-) features and peculiar genetic abnormalities. In a consultation series of 4498 cases collected between 2009 and 2021, 2099 neoplasms expressing synaptophysin and/or chromograninA were reviewed and analyzed. A total of 364 (18%) were diagnosed as non-NENs, while the remaining tumors were NEN. The group of mesenchymal/non-epithelial neoplasms with NE-features (MN-NE) included 31/364 (8%) cases. These mostly malignant neoplasms showed an epithelioid morphology. While all but one tumor expressed synaptophysin, mostly patchy, only 10/29 (34%) co-expressed chromograninA. A total of 13/31 (42%) of the MN-NE showed EWSR1-related gene fusions (6 Ewing sarcomas, 5 clear cell sarcomas, and 1 desmoplastic small round cell tumor, 1 neoplasm with FUS-CREM gene fusion) and 7 (23%) were SWI/SNF (SMARCB1 or SMARCA4)-deficient neoplasms. The remaining MN-NE included synovial sarcoma, sclerosing epithelioid mesenchymal neoplasm, melanoma, alveolar soft part sarcoma, solitary fibrous tumor, and chordoma. A total of 27/31 MN-NE were from the last 8 years, and 6 of them were located in the pancreas. Eleven MN-NE were initially diagnosed as neuroendocrine carcinomas (NECs). MN-NE with epithelioid features play an increasing role as mimickers of NECs. They mostly belong to tumors with gene fusions involving the EWSR1 gene, or with SWI/SNF complex deficiency. Synaptophysin expression is mostly patchy and chromograninA expression is infrequent in MN-NE of this series and data extracted from literature.

RGC-32 Acts as a Hub to Regulate the Transcriptomic Changes Associated With Astrocyte Development and Reactive Astrocytosis.

Response Gene to Complement 32 (RGC-32) is an important mediator of the TGF-ß signaling pathway, and an increasing amount of evidence implicates this protein in regulating astrocyte biology. We showed recently that spinal cord astrocytes in mice lacking RGC-32 display an immature phenotype reminiscent of progenitors and radial glia, with an overall elongated morphology, increased proliferative capacity, and increased expression of progenitor markers when compared to their wild-type (WT) counterparts that make them incapable of undergoing reactive changes during the acute phase of experimental autoimmune encephalomyelitis (EAE). Here, in order to decipher the molecular networks underlying RGC-32's ability to regulate astrocytic maturation and reactivity, we performed next-generation sequencing of RNA from WT and RGC-32 knockout (KO) neonatal mouse brain astrocytes, either unstimulated or stimulated with the pleiotropic cytokine TGF-ß. Pathway enrichment analysis showed that RGC-32 is critical for the TGF-ß-induced up-regulation of transcripts encoding proteins involved in brain development and tissue remodeling, such as axonal guidance molecules, transcription factors, extracellular matrix (ECM)-related proteins, and proteoglycans. Our next-generation sequencing of RNA analysis also demonstrated that a lack of RGC-32 results in a significant induction of WD repeat and FYVE domain-containing protein 1 (Wdfy1) and stanniocalcin-1 (Stc1). Immunohistochemical analysis of spinal cords isolated from normal adult mice and mice with EAE at the peak of disease showed that RGC-32 is necessary for the in vivo expression of ephrin receptor type A7 in reactive astrocytes, and that the lack of RGC-32 results in a higher number of homeodomain-only protein homeobox (HOPX)+ and CD133+ radial glia cells. Collectively, these findings suggest that RGC-32 plays a major role in modulating the transcriptomic changes in astrocytes that ultimately lead to molecular programs involved in astrocytic differentiation and reactive changes during neuroinflammation.

Perspectives and Issues in the Assessment of SMARCA4 Deficiency in the Management of Lung Cancer Patients.

Lung cancers are ranked third among the cancer incidence in France in the year 2020, with adenocarcinomas being the commonest sub-type out of ~85% of non-small cell lung carcinomas. The constant evolution of molecular genotyping, which is used for the management of lung adenocarcinomas, has led to the current focus on tumor suppressor genes, specifically the loss of function mutation in the SMARCA4 gene. SMARCA4-deficient adenocarcinomas are preponderant in younger aged male smokers with a predominant solid morphology. The importance of identifying SMARCA4-deficient adenocarcinomas has gained interest for lung cancer management due to its aggressive behavior at diagnosis with vascular invasion and metastasis to the pleura seen upon presentation in most cases. These patients have poor clinical outcome with short overall survival rates, regardless of the stage of disease. The detection of SMARCA4 deficiency is possible in most pathology labs with the advent of sensitive and specific immunohistochemical antibodies. The gene mutations can be detected together with other established lung cancer molecular markers based on the current next generation sequencing panels. Sequencing will also allow the identification of associated gene mutations, notably KRAS, KEAP1, and STK11, which have an impact on the overall survival and progression-free survival of the patients. Predictive data on the treatment with anti-PD-L1 are currently uncertain in this high tumor mutational burden cancer, which warrants more groundwork. Identification of target drugs is also still in pre-clinical testing. Thus, it is paramount to identify the SMARCA4-deficient adenocarcinoma, as it carries worse repercussions on patient survival, despite having an exceptionally low prevalence. Herein, we discuss the pathophysiology of SMARCA4, the clinicopathological consequences, and different detection methods, highlighting the perspectives and challenges in the assessment of SMARCA4 deficiency for the management of non-small cell lung cancer patients. This is imperative, as the contemporary shift on identifying biomarkers associated with tumor suppressor genes such as SMARCA4 are trending; hence, awareness of pathologists and clinicians is needed for the SMARCA4-dNSCLC entity with close follow-up on new management strategies to overcome the poor possibilities of survival in such patients.

SMARCA4 deficient tumours are vulnerable to KDM6A/UTX and KDM6B/JMJD3 blockade.

Despite the genetic inactivation of SMARCA4, a core component of the SWI/SNF-complex commonly found in cancer, there are no therapies that effectively target SMARCA4-deficient tumours. Here, we show that, unlike the cells with activated MYC oncogene, cells with SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to the aberrant accumulation of H3K27me3. SMARCA4-mutant cells also show an impaired transactivation and significantly reduced levels of the histone demethylases KDM6A/UTX and KDM6B/JMJD3, and a strong dependency on these histone demethylases, so that its inhibition compromises cell viability. Administering the KDM6 inhibitor GSK-J4 to mice orthotopically implanted with SMARCA4-mutant lung cancer cells or primary small cell carcinoma of the ovary, hypercalcaemic type (SCCOHT), had strong anti-tumour effects. In this work we highlight the vulnerability of KDM6 inhibitors as a characteristic that could be exploited for treating SMARCA4-mutant cancer patients.

Bromodomain protein BRD4 directs and sustains CD8 T cell differentiation during infection.

In response to infection, pathogen-specific CD8 T cells differentiate into functionally diverse effector and memory T cell populations critical for resolving disease and providing durable immunity. Through small-molecule inhibition, RNAi studies, and induced genetic deletion, we reveal an essential role for the chromatin modifier and BET family member BRD4 in supporting the differentiation and maintenance of terminally fated effector CD8 T cells during infection. BRD4 bound diverse regulatory regions critical to effector T cell differentiation and controlled transcriptional activity of terminal effector-specific super-enhancers in vivo. Consequentially, induced deletion of Brd4 or small molecule-mediated BET inhibition impaired maintenance of a terminal effector T cell phenotype. BRD4 was also required for terminal differentiation of CD8 T cells in the tumor microenvironment in murine models, which we show has implications for immunotherapies. Taken together, these data reveal an unappreciated requirement for BRD4 in coordinating activity of cis regulatory elements to control CD8 T cell fate and lineage stability.