Mutation of genes related to the SWI/SNF chromatin remodeling complex is detected in 20% of all cancers. The SWI/SNF chromatin remodeling complex comprises about 15 subunits and is classified into three subcomplexes: cBAF, PBAF, and ncBAF. Previously, we showed that ovarian clear cell carcinoma cells deficient in ARID1A, a subunit of the cBAF complex, are synthetic lethal with several genes required for glutathione (GSH) synthesis and are therefore sensitive to the GSH inhibitor eprenetapopt (APR-246). However, we do not know whether cancer cells deficient in SWI/SNF components other than ARID1A are selectively sensitive to treatment with eprenetapopt. Here, we show that SMARCA4-, SMARCB1-, and PBRM1-deficient cells are more sensitive to eprenetapopt than SWI/SNF-proficient cells. We found that deficiency of SMARCA4, SMARCB1, or PBRM1 attenuates transcription of the SLC7A11 gene (which supplies cysteine as a raw metabolic material for GSH synthesis) by the failure of recruitment of cBAF and PBAF to the promotor and enhancer regions of the SLC7A11 locus, thereby reducing basal levels of GSH. In addition, eprenetapopt decreased the amount of intracellular GSH and increased the intracellular amount of reactive oxygen species (ROS), followed by induction of apoptosis. Taken together, eprenetapopt could be a promising selective agent for SWI/SNF-deficient cancer cells derived from SMARCA4-deficient lung cancers, SMARCB1-deficient rhabdoid tumors, and PBRM1-deficient kidney cancers.
© 2024. The Author(s).

Summary Neurons and astrocytes play critical yet divergent roles in brain physiology and neurological conditions. Intracellular organelles are integral to cellular function. However, an in-depth characterization of organelles in live brain cells has not been performed. Here, we used multispectral imaging to simultaneously visualize six organelles – endoplasmic reticulum (ER), lysosomes, mitochondria, peroxisomes, Golgi, and lipid droplets – in live primary rodent neurons and astrocytes. We generated a dataset of 173 Z-stack and 99 time-lapse images accompanied by quantitative analysis of 1418 metrics (the “organelle signature”). Comparative analysis revealed clear cell-type specificity in organelle morphology and interactions. Neurons were characterized by prominent mitochondrial composition and interactions, while astrocytes contained more lysosomes and lipid droplet interactions. Additionally, neurons displayed a more robust organelle response than astrocytes to acute oxidative or ER stress. Our data provide a systems-level characterization of neuron and astrocyte organelles that can be a reference for understanding cell- type-specific physiology and disease.

Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are pathologically activated neutrophils that potently impair immunotherapy responses. The chemokine receptor CXCR4, a central regulator of hematopoiesis, represents an attractive PMN-MDSC target1. Here, we fused a secreted CXCR4 partial agonist TFF2 to mouse serum albumin (MSA) and demonstrated that TFF2-MSA peptide synergized with anti-PD-1 to induce tumor regression or eradication, inhibited distant metastases, and prolonged survival in multiple gastric cancer (GC) models. Using histidine decarboxylase (Hdc)-GFP transgenic mice to track PMN-MDSC in vivo , we found TFF2-MSA selectively reduced the immunosuppressive Hdc-GFP + CXCR4 hi tumor PMN-MDSCs while preserving proinflammatory neutrophils, thereby boosting CD8 + T cell-mediated anti-tumor response together with anti-PD-1. Furthermore, TFF2-MSA systemically reduced PMN-MDSCs and bone marrow granulopoiesis. In contrast, CXCR4 antagonism plus anti-PD-1 failed to provide a similar therapeutic benefit. In GC patients, expanded PMN-MDSCs containing a prominent CXCR4 + LOX-1 + subset are inversely correlated with the TFF2 level and CD8 + T cells in circulation. Collectively, our studies introduce a strategy of using CXCR4 partial agonism to restore anti-PD-1 sensitivity in GC by targeting PMN-MDSCs and granulopoiesis.

The placenta an essential extraembryonic organ that supports the fetus throughout gestation. The interactions between the placenta and the maternal immune system during the first trimester have not been wholly characterized despite their close physical association and hemi-allogeneic relationship. The most abundant type of immune cell in the uterus in the first trimester is the decidual natural killer cell (dNK). Despite their name, dNKs play supportive roles during pregnancy by remodelling uterine spiral arteries. We present evidence suggesting that the matrix metalloproteinases (MMPs) that dNKs secrete to promote this remodelling also drive placental development. This study used a novel co-culture system of dNKs and trophoblast organoids, which are mini-organs representing two to three different cell types of the human placenta. We found that co-cultures for one week led to significant (p=0.020) increases in the organoid area. We also observed significant decreases in trophoblast stemness markers and upregulation of gene sets associated with extravillous trophoblast (EVT) development through bulk RNA sequencing and immunohistochemical examinations. These changes were accompanied by significant (p<0.001) increases in collagen subunit gene expression in the organoids, with simultaneous significant decreases (p<0.001) in the proportion of organoid area occupied by collagen as determined through Massons Trichrome. Cultures containing dNKs also contained significantly higher MMP1, 3, 9, and 10 levels in their culture media, each of which can break down collagen. These findings demonstrate that dNKs promote changes concordant with trophoblast differentiation towards EVTs and villous branching morphogenesis.

The E4 variant of APOE strongly predisposes individuals to late-onset Alzheimer's disease. We demonstrate that in response to lipogenesis, apolipoprotein E (APOE) in astrocytes can avoid translocation into the endoplasmic reticulum (ER) lumen and traffic to lipid droplets (LDs) via membrane bridges at ER-LD contacts. APOE knockdown promotes fewer, larger LDs after a fatty acid pulse, which contain more unsaturated triglyceride after fatty acid pulse-chase. This LD size phenotype was rescued by chimeric APOE that targets only LDs. Like APOE depletion, APOE4-expressing astrocytes form a small number of large LDs enriched in unsaturated triglyceride. Additionally, the LDs in APOE4 cells exhibit impaired turnover and increased sensitivity to lipid peroxidation. Our data indicate that APOE plays a previously unrecognized role as an LD surface protein that regulates LD size and composition. APOE4 causes aberrant LD composition and morphology. Our study contributes to accumulating evidence that APOE4 astrocytes with large, unsaturated LDs are sensitized to lipid peroxidation, which could contribute to Alzheimer's disease risk.
© 2024 Windham et al.