Combination of downregulating FEN1 and PD-1 blockade enhances antitumor activity of CD8+ T cells against HNSCC cells in vitro.

BACKGROUND: Programmed cell death ligand 1 (PD-L1) and human leukocyte antigen/major histocompatibility complex (HLA/MHC) are two main kinds of immunophenotypes affecting the susceptibility to anti-PD therapy. Our previous study found that down-regulation of flap endonuclease-1 (FEN1) could not only inhibit PD-L1 expression, but also upregulate HLA expression in head and neck squamous cell carcinoma (HNSCC). We aimed to clarify whether downregulating FEN1 cloud enhance the response to PD-1 blockade, and possible mechanisms in HNSCC in vitro. METHODS: Differential expression of FEN1 in HNSCC tumor and normal tissues were explored in the TIMER and TISIDB datasets. A HNSCC cells/CD8+ T cells co-culture model was established. HNSCC cell cycle and apoptosis were recorded by flow cytometry. Immune activity markers of granzyme A, granzyme B, and PRF1 expressed in the CD8+ T cells, and IFN-γ, IL-2, and TNF-α secreted in the supernatants were detected by western blot, ELISA, respectively. RESULTS: FEN1 was highly expressed in HNSCC and associated with low immune infiltration. Downregulating FEN1 could induce HLA class I expression, and inhibit PD-L1 expression in HNSCC cells. Functionally, FEN1 knockdown enhanced the response to αPD-1 mAb by mediating G2/M phase arrest, apoptosis of HNSCC cells. Mechanistically, targeting FEN1 synergized with αPD-1 mAb could reinforce the antitumor response of CD8+ T cells against HNSCC cells, as indicated by increasing granzyme A, granzyme B, and PRF1 expressions, and promoting IFN-γ, IL-2, and TNF-α secretions. CONCLUSION: These findings might offer a potential combined strategy for patients resistant to anti-PD therapy via combining FEN1 knockdown and PD-1 blockade.

Long non-coding RNA DLGAP1-AS1 modulates the development of non-small-cell lung cancer via the microRNA-193a-5p/DTL axis.

Non-small cell lung cancer (NSCLC) is one of the most malignant cancers worldwide. A growing number of studies have suggested that long noncoding RNAs (lncRNAs) play a key role in the progression of non-small cell lung cancer (NSCLC). Here, we report a novel lncRNA DLGAP1 antisense RNA 1 (DLGAP1-AS1) that exhibits oncogenic properties in NSCLC. The lncRNA DLGAP1-AS1 and denticleless protein homolog (DTL) presented upregulated expression, but microRNA-193a-5p (miR-193a-5p) showed downregulated expression in cancerous tissues of human lung samples from 48 patients with NSCLC. Partial loss of lncRNA DLGAP1-AS1 reduced malignant cell viability, migration, and invasion but induced apoptosis. Dual-luciferase reporter gene, RNA pull-down and RNA binding protein immunoprecipitation assays demonstrated enrichment of lncRNA DLGAP1-AS1 in miR-193a-5p and Argonaute 2, suggesting that lncRNA DLGAP1-AS1 modulated DTL, a putative target of miR-193a-5p. We also found that restoration of miR-193a-5p rescued NSCLC cell biological functions affected by overexpression of lncRNA DLGAP1-AS1. Silencing lncRNA DLGAP1-AS1 was found to reduce the tumorigenesis of NSCLC cells xenografted into nude mice, which was rescued by DTL overexpression. In conclusion, our study highlights a novel regulatory network of the lncRNA DLGAP1-AS1/miR-193a-5p/DTL axis in NSCLC, providing a potential therapeutic strategy for NSCLC.

Kikuchi-Fujimoto disease: a case report and the evaluation of diagnostic procedures.

BACKGROUND: Kikuchi-Fujimoto disease, known as histiocytic necrotizing lymphadenitis, is a benign, self-limiting and systemic disorder involving lymph nodes with unknown aetiology. First reported in Japan, there has been an increase in its incidence globally. Because of its non-specific clinical features, the disease can be easily mistaken for other forms of lymphadenitis with a high rate of misdiagnosis and mistreatment, posing a considerable challenge. CASE PRESENTATION: A case of young Chinese woman with fever and cervical lymphadenopathy is presented. Physical examinations and imaging techniques were used to rule out common forms of lymphadenitis (e.g. cat-scratch disease and tuberculous lymphadenitis). Laboratory tests were then conducted to exclude others such as systemic lupus erythematosus and non-Hodgkin lymphoma. After Kikuchi-Fujimoto disease was identified, the patient was managed with symptomatic treatments. Our case was compared with relevant cases in the literature. A diagnostic flow chart was proposed to facilitate the diagnosis and treatment. CONCLUSIONS: With its shared clinical features, Kikuchi-Fujimoto disease can be mistaken for other forms of lymphadenitis. A combined use of medical imaging and laboratory tests is the effective way to avoid misdiagnosis.

MOC1 cleaves Holliday junctions through a cooperative nick and counter-nick mechanism mediated by metal ions.

Holliday junction resolution is a crucial process in homologous recombination and DNA double-strand break repair. Complete Holliday junction resolution requires two stepwise incisions across the center of the junction, but the precise mechanism of metal ion-catalyzed Holliday junction cleavage remains elusive. Here, we perform a metal ion-triggered catalysis in crystals to investigate the mechanism of Holliday junction cleavage by MOC1. We capture the structures of MOC1 in complex with a nicked Holliday junction at various catalytic states, including the ground state, the one-metal ion binding state, and the two-metal ion binding state. Moreover, we also identify a third metal ion that may aid in the nucleophilic attack on the scissile phosphate. Further structural and biochemical analyses reveal a metal ion-mediated allosteric regulation between the two active sites, contributing to the enhancement of the second strand cleavage following the first strand cleavage, as well as the precise symmetric cleavage across the Holliday junction. Our work provides insights into the mechanism of metal ion-catalyzed Holliday junction resolution by MOC1, with implications for understanding how cells preserve genome integrity during the Holliday junction resolution phase.