Mammalian switch/sucrose nonfermentable (mSWI/SNF) ATPase degraders have been shown to be effective in enhancer-driven cancers by functioning to impede oncogenic transcription factor chromatin accessibility. Here, we developed AU-24118, an orally bioavailable proteolysis-targeting chimera (PROTAC) degrader of mSWI/SNF ATPases (SMARCA2 and SMARCA4) and PBRM1. AU-24118 demonstrated tumor regression in a model of castration-resistant prostate cancer (CRPC) which was further enhanced with combination enzalutamide treatment, a standard of care androgen receptor (AR) antagonist used in CRPC patients. Importantly, AU-24118 exhibited favorable pharmacokinetic profiles in preclinical analyses in mice and rats, and further toxicity testing in mice showed a favorable safety profile. As acquired resistance is common with targeted cancer therapeutics, experiments were designed to explore potential mechanisms of resistance that may arise with long-term mSWI/SNF ATPase PROTAC treatment. Prostate cancer cell lines exposed to long-term treatment with high doses of a mSWI/SNF ATPase degrader developed SMARCA4 bromodomain mutations and ABCB1 (ATP binding cassette subfamily B member 1) overexpression as acquired mechanisms of resistance. Intriguingly, while SMARCA4 mutations provided specific resistance to mSWI/SNF degraders, ABCB1 overexpression provided broader resistance to other potent PROTAC degraders targeting bromodomain-containing protein 4 and AR. The ABCB1 inhibitor, zosuquidar, reversed resistance to all three PROTAC degraders tested. Combined, these findings position mSWI/SNF degraders for clinical translation for patients with enhancer-driven cancers and define strategies to overcome resistance mechanisms that may arise.

BACKGROUND: Aberrant expression of SWI/SNF complex subunits is closely associated with tumorigenesis. The clinicopathological and prognostic significance of altered SMARCA2 and SMARCA4 subunits has not been well evaluated in gastric adenocarcinoma.
METHODS: We collected 1271 postoperative cases of gastric adenocarcinoma and then constructed tissue microarrays (TMA), from which we obtained the immunohistochemistry expression of SMARCA2 and SMARCA4. Next, we screened the variables related to the loss of SMARCA2 and SMARCA4 by univariate correlation analysis and multivariate logistic regression analysis. Then, we identified the variables related to prognosis by univariate and multivariate Cox regression analysis. Finally, we constructed a nomogram prognostic model and evaluated it.
RESULTS: The loss of SMARCA2 and SMARCA4 occurred in 236 (18.57%) and 86 (6.77%) cases, respectively, including 26 cases of co-loss. After multivariate logistic regression, variables independently associated with SMARCA2 loss were T stage, differentiation status, WHO histological classification, and EBER. Variables independently associated with SMARCA4 loss were differentiation status, WHO histological classification, PD-L1, and MMR. Survival analysis revealed that the SMARCA2 and SMARCA4 lost groups showed worse survival than the corresponding present groups (P = 0.032 and P = 0.0048, respectively). Univariate and multivariate Cox analyses identified independent prognostic factors, including age, T stage, N stage, M stage, SMARCA2, and chemotherapy.
CONCLUSIONS: The loss of SMARCA2 and SMARCA4 correlated with poor differentiation, leading to a worse prognosis. SMARCA2, as an independent prognostic factor, combined with other clinicopathological variables, established a novel nomogram prognostic model, which outperformed the AJCC TNM model.

BACKGROUND: The switch/sucrose nonfermentable (SWI/SNF) complex is an evolutionarily conserved chromatin remodeling complex that displays dysfunction in many tumors, especially undifferentiated carcinoma. Cancer stem cells (CSC), a special type of undifferentiated cancer cells with stem cell-like properties, play an essential role in tumor cell proliferation, invasion, and metastasis. In undifferentiated gastric carcinomas, the association of SWI/SNF complexes with clinicopathological features, CSC phenotype, and the prognosis is not fully understood.
METHODS: We collected a cohort of 21 patients with undifferentiated/dedifferentiated gastric carcinoma. We next performed immunohistochemistry staining for the five subunits of the SWI/SNF complex (ARID1A, ARID1B, SMARCA2, SMARCA4, and SMARCB1), and four mismatch repair proteins (MLH1, PMS2, MSH2, and MSH6), as well as other markers such as p53, PD-L1, and cancer stem cell (CSC) markers (SOX2, SALL4). Then, we investigated the correlation of SWI/SNF complex subunits with clinicopathological characters and performed prognostic analysis.
RESULTS: We observed SMARCA2 loss in 12 cases (57.14%), followed by ARID1A (5 cases, 23.81%) and SMARCA4 (3 cases, 14.29%). Fourteen cases (66.67%) lost any one of the SWI/SNF complex subunits, including 3 cases with SMARCA2 and ARID1A co-loss, and 3 cases with SMARCA2 and SMARCA4 co-loss. Correlation analysis revealed that the CSC phenotype occurred more frequently in the SWI/SNF complex deficient group (P = 0.0158). Survival analysis revealed that SWI/WNF complex deficiency, undifferentiated status, CSC phenotype, and the loss of SMARCA2 and SMARCA4 resulted in worse survival. Univariate and multivariate Cox regression analyses screened out three independent factors associated with worse prognosis: undifferentiated status, SWI/SNF complex deficiency, and lymph node metastasis.
CONCLUSIONS: The SWI/SNF complex deficiency was more likely to result in a CSC phenotype and worse survival and was an independent prognostic factor in undifferentiated/dedifferentiated gastric carcinoma.

Objective: Paternal sperm mosaicism has few consequences for fathers for mutations being restricted to sperm. However, it could potentially underlie severe sporadic disease in their offspring. Here, we present a live birth of a female infant from a father with low-level sperm DNA mosaicism achieved via preimplantation genetic testing for monogenic disorders (PGT-M). Methods: A couple with the father carrying sperm DNA mosaicism received standard in vitro fertilization treatment, with intracytoplasmic sperm injection, embryo biopsy, polymerase chain reaction, and DNA analysis. Only one unaffected embryo was transferred to the uterine cavity. Amniocentesis was performed at the 16th week of gestation by copy-number variation-sequencing, karyotyping, and Sanger sequencing. Results: Eight surviving embryos were biopsied during the blastocyst stage. Karyomapping and Sanger sequencing were applied to detect the euploidy and paternal mutation. After performing PGT-M, followed by successful pregnancy, the prenatal genetic diagnoses revealed that the fetus was unaffected, and one healthy girl was born. Conclusion: This is the first reported live birth with unaffected children achieved via PGT for a low-level germline mosaicism father. It not only opens the possibility of preventing the recurrent monogenic disease of children among gonadal mosaicism families but also alerts clinicians to consider gonadal mosaicism as the source of DMNs.

As a clinical subtype of SWI/SNF-related intellectual disability syndromes, Nicolaides-Baraitser syndrome (NCBRS, OMIM601358) has a unique genotype-phenotype. Due to the scarcity of the number of cases reported and the limitations of diagnosis methods, so far only more than 80 cases have been reported worldwide. In this article, a new patient with a de novo mutation was followed up for 10 years; it includes the epilepsy treatment process, the characteristics of NBCRS with seizures, typical faces, sparse hair, prominent interphalangeal joints, and intellectual disability, and we also summarized the genotype-phenotype of the 80 reported cases for comparison. Due to insufficient studies and lack of attention paid to the syndrome, it is believed that the actual number of cases should be far more than the reported number. The syndrome is phased and progressive. The genotype-phenotype correlation of the disease is related to the location of the gene locus, especially closely related to the SNF2 ATPase domain. CONCLUSIONS: The understanding of NCBRS is lagging, we need to strengthen the screening process of the phenotypic disease with intellectual disability, and perfecting multiple types of diagnostic techniques will help the discovery of the disease; its clinical features are staged and are slowly progressive, and long-term prognosis must be taken precautious with long-term follow-up required.

SMARCA2, an evolutionarily conserved catalytic ATPase subunit of SWI/SNF complexes, has been implicated in development and diseases; however, its role in mammalian ovarian function and female fertility is unknown. Here, we identified and characterized the 3\'-UTR of the porcine SMARCA2 gene and identified a novel adenylate number variation. Notably, this mutation was significantly associated with sow litter size traits and SMARCA2 levels, due to its influence on the stability of SMARCA2 mRNA in ovarian granulosa cells (GCs). Immunohistochemistry and functional analysis showed that SMARCA2 is involved in the regulation of follicular atresia by inhibiting GC apoptosis. In addition, miR-29c, a pro-apoptotic factor, was identified as a functional miRNA that targets SMARCA2 in GCs and mediates regulation of SMARCA2 expression via the NORFA-SMAD4 axis. Although a potential miR-29c-responsive element was identified within NORFA, negative regulation of miR-29c expression by NORFA was not due to activity as a competing endogenous RNA. In conclusion, our findings demonstrate that SMARCA2 is a candidate gene for sow litter size traits, because it regulates follicular atresia and GC apoptosis. Additionally, we have defined a novel candidate pathway for sow fertility, the NORFA-TGFBR2-SMAD4-miR-29c-SMARCA2 pathway.This article has an associated First Person interview with the first author of the paper.

The SWI/SNF complex is a multimeric chromatin remodeling complex that has vital roles in regulating gene expression and cancer development. However, to date few studies have deeply explored the mechanism of SMARCA2 inactivation. We applied multi-omics analysis to explore the mechanism of SMARCA2 inactivation in The Cancer Genome Atlas (TCGA) database and performed the dCas9-DNMT3a system to evaluate the role of promoter methylation in SMARCA2 transcriptional regulation. We also assessed the tumor suppressing roles of SMARCA2 in lung cancer development by in vitro experiments. SMARCA2 promoter hypermethylation was significantly associated with decreased expression of SMARCA2. This result was further confirmed in the results of our own tissues. In addition, we observed that the mRNA level decreased by about 3 folds while the CpG island of promoter is nearly 30% hypermethylated by dCas9-DNMT3a system in H1299 cells. We identified SMARCA2 as a tumor suppressor gene whose expression was downregulated in lung cancers. Its inactivation was significantly associated with the poor survival of lung cancer patients [hazard ratio, HR = 0.35 (0.27-0.45)]. Besides, we found that SMARCA2 was a tumor suppressor and can significantly inhibit lung cancer cell vitality. We found that promoter hypermethylation contribute to the inactivation of SMARCA2. We also verified its oncogenetic roles of BRM inactivation in lung adenocarcinoma, which may provide a potential target for the clinical treatment.

SMARCA2 is a critical catalytic subunit of the switch/sucrose non-fermenting (SWI/SNF) chromatin remodeling complexes. Dysregulation of SMARCA2 is associated with several diseases, including some cancers. SMARCA2 is multi-domain protein containing a bromodomain (BRD) that specifically recognizes acetylated lysine residues in histone tails, thus playing an important role in chromatin remodeling. Many potent and specific inhibitors targeting other BRDs have recently been discovered and have been widely used for cancer treatments and biological research. However, hit discovery targeting SMARCA2-BRD is particularly lacking. To date, there is a paucity of reported high-throughput screening (HTS) assays targeting the SMARCA2-BRD interface. In this study, we developed an AlphaScreen HTS system for the discovery of SMARCA2-BRD inhibitors and optimized the physicochemical conditions including pH, salt concentrations and detergent levels. Through an established AlphaScreen-based high-throughput screening assay against an in-house compound library, DCSM06 was identified as a novel SMARCA2-BRD inhibitor with an IC50 value of 39.9±3.0 μmol/L. Surface plasmon resonance demonstrated the binding between SMARCA2-BRD and DCSM06 (Kd=38.6 μmol/L). A similarity-based analog search led to identification of DCSM06-05 with an IC50 value of 9.0±1.4 μmol/L. Molecular docking was performed to predict the binding mode of DCSM06-05 and to decipher the structural basis of the infiuence of chemical modifications on inhibitor potency. DCSM06-05 may be used as a starting point for further medicinal chemistry optimization and could function as a chemical tool for SMARCA2-related functional studies.

MiR-375 is an important small non-coding RNA that is specifically expressed in islet cells of the pancreas. miR-375 is required for normal pancreatic genesis and influences not only β-cell mass but also α-cell mass. miR-375 is also important to glucose-regulated insulin secretion through the regulation of the expression of Mtpn and Pdk1 genes. When human embryonic stem cells (hESCs) differentiate into endodermal lineages, miR-375 is highly expressed in the definitive endoderm, which suggests that miR-375 may have a distinct role in early development. miR-375 plays an important role in the complex regulatory network of pancreatic development, which could be regulated by pancreatic genes, such as NeuroD1, Ngn3, Pdx1 and Hnf6; additionally, miR-375 regulates genes related to pancreas development, cell growth and proliferation and insulin secretion genes to exert its function. Because of the special role of miR-375, it may be a potential target to treat diabetes. Antagonising miR-375 may enhance the effects of exendin-4 in patients, and controlling the expression of miR-375 could assist mature hESCs-derived β-cells.