Inhibition of YTHDF2 triggers proteotoxic cell death in MYC-driven breast cancer.

RNA-binding proteins (RBPs) are critical regulators of post-transcriptional gene expression, and aberrant RBP-RNA interactions can promote cancer progression. Here, we interrogate the function of RBPs in cancer using pooled CRISPR-Cas9 screening and identify 57 RBP candidates with distinct roles in supporting MYC-driven oncogenic pathways. We find that disrupting YTHDF2-dependent mRNA degradation triggers apoptosis in triple-negative breast cancer (TNBC) cells and tumors. eCLIP and m6A sequencing reveal that YTHDF2 interacts with mRNAs encoding proteins in the MAPK pathway that, when stabilized, induce epithelial-to-mesenchymal transition and increase global translation rates. scRibo-STAMP profiling of translating mRNAs reveals unique alterations in the translatome of single cells within YTHDF2-depleted solid tumors, which selectively contribute to endoplasmic reticulum stress-induced apoptosis in TNBC cells. Thus, our work highlights the therapeutic potential of RBPs by uncovering a critical role for YTHDF2 in counteracting the global increase of mRNA synthesis in MYC-driven breast cancers.

Two mechanisms of chromosome fragility at replication-termination sites in bacteria.

Chromosomal fragile sites are implicated in promoting genome instability, which drives cancers and neurological diseases. Yet, the causes and mechanisms of chromosome fragility remain speculative. Here, we identify three spontaneous fragile sites in the Escherichia coli genome and define their DNA damage and repair intermediates at high resolution. We find that all three sites, all in the region of replication termination, display recurrent four-way DNA or Holliday junctions (HJs) and recurrent DNA breaks. Homology-directed double-strand break repair generates the recurrent HJs at all of these sites; however, distinct mechanisms of DNA breakage are implicated: replication fork collapse at natural replication barriers and, unexpectedly, frequent shearing of unsegregated sister chromosomes at cell division. We propose that mechanisms such as both of these may occur ubiquitously, including in humans, and may constitute some of the earliest events that underlie somatic cell mosaicism, cancers, and other diseases of genome instability.

Spliceosome-targeted therapies trigger an antiviral immune response in triple-negative breast cancer.

Many oncogenic insults deregulate RNA splicing, often leading to hypersensitivity of tumors to spliceosome-targeted therapies (STTs). However, the mechanisms by which STTs selectively kill cancers remain largely unknown. Herein, we discover that mis-spliced RNA itself is a molecular trigger for tumor killing through viral mimicry. In MYC-driven triple-negative breast cancer, STTs cause widespread cytoplasmic accumulation of mis-spliced mRNAs, many of which form double-stranded structures. Double-stranded RNA (dsRNA)-binding proteins recognize these endogenous dsRNAs, triggering antiviral signaling and extrinsic apoptosis. In immune-competent models of breast cancer, STTs cause tumor cell-intrinsic antiviral signaling, downstream adaptive immune signaling, and tumor cell death. Furthermore, RNA mis-splicing in human breast cancers correlates with innate and adaptive immune signatures, especially in MYC-amplified tumors that are typically immune cold. These findings indicate that dsRNA-sensing pathways respond to global aberrations of RNA splicing in cancer and provoke the hypothesis that STTs may provide unexplored strategies to activate anti-tumor immune pathways.

Ultrastructure Characteristics of Different Chinese Medicine Syndromes of Helicobacter pylori-Correlated Gastric Diseases.

OBJECTIVE: To explore the ultrastructure characteristics of patients with dampness-heat of Pi (Spleen)-Wei (Stomach) syndrome (DHPW) and Pi-qi deficiency syndrome (PQD), both of which are Helicobacter pylori (Hp)-correlated gastric diseases (HPCG), and implicate a helpful hint for the clinical microcosmic syndrome differentiation. METHODS: Fourteen gastric mucosa samples from 6 chronic gastritis (CG) and 6 active peptic ulcer (including 8 DHPW, 4 PQD) as well as 2 healthy volunteers were collected and tested for Hp infection. The ultrastructure of gastric mucosa was observed under the transmission electron microscope (TEM). RESULTS: Among 14 gastric mucosa samples, 8 of them were Hp positive (6 DHPW and 2 PQD), which were all accordance with the results screened by supermicro-pathological method. Under TEM, the normal gastric mucosa, with tidy microvilli and abundant in mucus granules, mitochondria and rough endoplasmic reticulum distributed evenly, and with smooth nucleus membrane. But in those specimens of DHPW with Hp infection, microvilli were presented with burr shape. Especially, those samples from dampness-heat syndrome with predominant heat type (DHSH) patients were more obvious, with microvilli damaged, mitochondria concentrated and distributed in disorder, secretory tubule extended. In dampness-heat syndrome with predominant dampness type (DHSD) patients, mucus granules aggregated obviously, mitochondria swelled and blurred, and rough endoplasmic reticulum crowded. For 2 samples of DHPW without Hp infection, their microvilli were intact, with mitochondria increased and gathered but well-distributed, and secretory tubule extended mildly. In 2 PQD patients with Hp positive, the specimens of microvilli were sparse, and their mucus granules and mitochondria were decreased, with fractured crests and vacuole, secretory tubules extension to nucleus membrane, and rough endoplasmic reticulum extension in a pool-like way, and nucleus condensed. The 2 samples from PQD patients without Hp infection were characterized with intact microvilli, decreased mitochondria, fractured crest and extended rough endoplasmic reticulum in a pool-like way. CONCLUSION: It's obviously different in ultrastructure of DHPW and PQD patients under TEM, which may give a helpful hint for the microcosmic syndrome differentiation of HPCG.

Interleukin-12 and interferon-γ acting on damp-heat of spleen- stomach syndrome triggered by Helicobacter pylori.

OBJECTIVE: To investigate the expression of and interleukin-12 (IL-12) and interferon-γ (IFN-γ) in relation to the pathology of damp-heat of spleen-stomach syndrome (DHSS) induced by Helicobacter pylori (H. pylori) infection. METHODS: In total, 114 individual gastric mucosal specimens including 83 DHSS, 19 spleen-qi deficiency syndrome (SQD) and 12 from healthy volunteers (CON) were collected by gastroscopy. To explore the relationship between the two syndromes and H. pylori infection, individual samples were tested using rapid urease and methylene blue tests. Hematoxylin and eosin stained sections were examined to grade for the degree of inflammation and inflammatory activity, and expression of IL-12 and IFN-γ was investigated by immunohistochemistry. RESULTS: Statistically significant differences in the degree of inflammation and inflammatory activity were observed between the groups of specimens: DHSS, SQD and CON (P < 0.05). Additionally, greater intestinal metaplasia (IM) and dysplasia were observed in the DHSS group, especially those with H. pylori infection. Expression of both IFN-γ; and IL-12 was higher in DHSS samples infected with H. pylori than in uninfected samples and in the CON (P < 0.05) but not in the SQD (P > 0.05) groups. Intriguingly, in gastric specimens exhibiting IM and dysplasia, IL-12 translocated from the nucleus into the cytoplasm. CONCLUSION: Our findings suggest that IL-12 and IFN-γ are involved in DHSS pathology, but not in SQD, acting as healthy-Qi. DHSS is not just the consequence of those two cytokines but results from the cross-talk between a number of cytokines and/or other proteins, which may warrant further investigation in DHSS patients infected with H. pylori.

Cellular Phenotypic Analysis of Macrophage Activation Unveils Kinetic Responses of Agents Targeting Phosphorylation.

Macrophages are highly plastic cells, which serve as sentinels of the host immune system due to their ability to recognize and respond to microbial products rapidly and dynamically. Appropriate regulation of macrophage activation is essential for pathogen clearance or preventing autoimmune diseases. However, regularly used endpoint assays for analyzing macrophage functions have the limitations of being static and non-high throughput. In this study, we introduced a real-time and convenient method based on changes in cellular impedance that are detected by microelectronic biosensors. This new method can record the time/dose-dependent cell response profiles (TCRPs) of macrophages in real time and generates physiologically relevant data. The TCRPs generated from classically interferon-γ/lipopolysaccharide-activated macrophages showed considerable consistency with the data generated from standard endpoint assays. We further explored this approach by using it for global screening of a library of protein tyrosine kinase/phosphatase (PTK/PTP) inhibitors to investigate their impact on macrophage activation. Collectively, our findings suggest that the cellular impedance-based assay provides a promising approach for dynamically monitoring macrophage functions in a convenient and high-throughput manner.

Scaffolding protein Gab1 regulates myeloid dendritic cell migration in allergic asthma.

Asthma is a common allergic disorder involving a complex interplay among multiple genetic and environmental factors. Recent studies identified genetic variants of human GAB1 as a novel asthma susceptibility factor. However, the functions of Gab1 in lung remain largely unexplored. In this study, we first observed an elevation of Gab1 level in peripheral blood mononuclear cells from asthmatic patients during acute exacerbation compared with convalescence. Mice with a selectively disrupted Gab1 in myeloid dendritic cells (mDCs) considerably attenuated allergic inflammation in experimental models of asthma. Further investigations revealed a prominent reduction in CCL19-mediated migration of Gab1-deficient mDCs to draining lymph nodes and subsequent impairment of Th2-driven adaptive activation. Mechanistically, Gab1 is an essential component of the CCL19/CCR7 chemokine axis that regulates mDC migration during asthmatic responses. Together, these findings provide the first evidence for the roles of Gab1 in lung, giving us deeper understanding of asthmatic pathogenesis.

CDK7-dependent transcriptional addiction in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive form of breast cancer that exhibits extremely high levels of genetic complexity and yet a relatively uniform transcriptional program. We postulate that TNBC might be highly dependent on uninterrupted transcription of a key set of genes within this gene expression program and might therefore be exceptionally sensitive to inhibitors of transcription. Utilizing kinase inhibitors and CRISPR/Cas9-mediated gene editing, we show here that triple-negative but not hormone receptor-positive breast cancer cells are exceptionally dependent on CDK7, a transcriptional cyclin-dependent kinase. TNBC cells are unique in their dependence on this transcriptional CDK and suffer apoptotic cell death upon CDK7 inhibition. An "Achilles cluster" of TNBC-specific genes is especially sensitive to CDK7 inhibition and frequently associated with super-enhancers. We conclude that CDK7 mediates transcriptional addiction to a vital cluster of genes in TNBC and CDK7 inhibition may be a useful therapy for this challenging cancer.