Barrier-to-autointegration factor 1: A novel biomarker for gastric cancer

Cytoplasmic Shotgun Proteomic Points to Key Proteins and Pathways in Temozolomide-Resistant Glioblastoma Multiforme

Temozolomide (TMZ) is the first line of chemotherapy to treat primary brain tumors of the type glioblastoma multiforme (GBM). TMZ resistance (TMZR) is one of the main barriers to successful treatment and is a principal factor in relapse, resulting in a poor median survival of 15 months. The present paper focuses on proteomic analyses of cytosolic fractions from TMZ-resistant (TMZR) LN-18 cells. The experimental workflow includes an easy, cost-effective, and reproducible method to isolate subcellular fraction of cytosolic (CYTO) proteins, mitochondria, and plasma membrane proteins for proteomic studies. For this study, enriched cytoplasmic fractions were analyzed in replicates by nanoflow liquid chromatography tandem high-resolution mass spectrometry (nLC-MS/MS), and proteins identified were quantified using a label-free approach (LFQ). Statistical analysis of control (CTRL) and temozolomide-resistant (TMZR) proteomes revealed proteins that appear to be differentially controlled in the cytoplasm. The functions of these proteins are discussed as well as their roles in other cancers and TMZ resistance in GBM. Key proteins are also described through biological processes related to gene ontology (GO), molecular functions, and cellular components. For protein-protein interactions (PPI), network and pathway involvement analyses have been performed, highlighting the roles of key proteins in the TMZ resistance phenotypes. This study provides a detailed insight into methods of subcellular fractionation for proteomic analysis of TMZ-resistant GBM cells and the potential to apply this approach to future large-scale studies. Several key proteins, protein-protein interactions (PPI), and pathways have been identified, underlying the TMZ resistance phenotype and highlighting the proteins' biological functions.

Inhibition of tumor intrinsic BANF1 activates antitumor immune responses via cGAS-STING and enhances the efficacy of PD-1 blockade

BACKGROUND

BANF1 is well known as a natural opponent of cyclic GMP-AMP synthase (cGAS) activity on genomic self-DNA. However, the roles of BANF1 in tumor immunity remain unclear. Here, we investigate the possible impact of BANF1 on antitumor immunity and response to immunotherapy.

METHODS

The Cancer Genome Atlas public data were analyzed to evaluate the relevance of the expression of BANF1, patients' survival and immune cell infiltration. We monitored tumor growth and explored the antitumor efficacy of targeting tumor-intrinsic BANF1 in combination with anti-programmed cell death protein-1 (PD-1) in MC38 or B16F10 tumor models in both immunocompetent and immunodeficient mice. Flow cytometry, immunofluorescence and T cells depletion experiments were used to validate the role of BANF1 in tumor immune microenvironment reprogramming. RNA sequencing was then used to interrogate the mechanisms how BANF1 regulated antitumor immunity.

RESULTS

We show that upregulated expression of BANF1 in tumor tissues is significantly associated with poor survival and is negatively correlated with immune cell infiltration. Deficiency of BANF1 in tumor cells markedly antagonizes tumor growth in immunocompetent but not immunocompromised mice, and enhances the response to immunotherapy in murine models of melanoma and colon cancer. In the immunotherapy clinical cohort, patients with high BANF1 expression had a worse prognosis. Mechanistically, BANF1 knockout activates antitumor immune responses mediated by cGAS-synthase-stimulator of interferon genes (cGAS-STING) pathway, resulting in an immune-activating tumor microenvironment including increased CD8+ T cell infiltration and decreased myeloid-derived suppressor cell enrichment.

CONCLUSIONS

BANF1 is a key regulator of antitumor immunity mediated by cGAS-STING pathway. Therefore, our study provides a rational that targeting BANF1 is a potent strategy for enhancing immunotherapy for cancer with BANF1 upregulation.

Identification of Parkinson's disease-associated chromatin regulators

Parkinson's disease (PD) is a common neurological disorder that causes quiescent tremors, motor delays, depression, and sleep disturbances. Existing treatments can only improve symptoms, not stop progression or cure the disease, but effective treatments can significantly improve patients' quality of life. There is growing evidence that chromatin regulatory proteins (CRs) are involved in a variety of biological processes, including inflammation, apoptosis, autophagy, and proliferation. But the relationship of chromatin regulators in Parkinson's disease has not been studied. Therefore, we aim to investigate the role of CRs in the pathogenesis of Parkinson's disease. We collected 870 chromatin regulatory factors from previous studies and downloaded data on patients with PD from the GEO database. 64 differentially expressed genes were screened, the interaction network was constructed and the key genes with the top 20 scores were calculated. Then we discussed its correlation with the immune function of PD. Finally, we screened potential drugs and miRNAs. Five genes related to the immune function of PD, BANF1, PCGF5, WDR5, RYBP and BRD2, were obtained by using the absolute value of correlation greater than 0.4. And the disease prediction model showed good predictive efficiency. We also screened 10 related drugs and 12 related miRNAs, which provided a reference for the treatment of PD. BANF1, PCGF5, WDR5, RYBP and BRD2 are related to the immune process of Parkinson's disease and can predict the occurrence of Parkinson's disease, which is expected to become a new target for the diagnosis and treatment of Parkinson's disease.

Interaction of obtusilactone B and related butanolide lactones with the barrier-to-autointegration factor 1 (BAF1). A computational study

The barrier-to-autointegration factor 1 (BAF1) protein is a DNA-binding protein implicated in nuclear envelop repair and reformation after mitosis. This nuclear protein is frequently overexpressed in cancer cells and plays a role in the occurrence and development of different tumors. It is a potential therapeutic target for gastric cancer, breast cancer and other malignancies. For this reason, BAF1 inhibitors are searched. The butanolide lactone obtusilactone B (Ob-B) has been found to inhibit VRK1-dependent phosphorylation of BAF1, upon direct binding to the nuclear protein. Taking advantage of the known crystallographic structure of BAF1, we have elaborated molecular models of Ob-B bound to BAF1 to delimit the binding site and binding configuration. The long endoolefinic alkyl side chain of Ob-B extends into a small groove on the protein surface, and the adjacent exomethylene-γ-lactone moiety occupies a pocket comprising to the Ser-4 phosphorylation site of BAF1. Twenty butanolide lactones structurally close to ObB were screened for BAF1 binding. Several natural products with BAF1-binding capacity potentially superior to Ob-B were identified, including mahubanolide, kotomolide B, epilitsenolide D2, and a few other known anticancer plant natural products. Our study provides new ideas to guide the discovery and design of BAF1 inhibitors.

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Obtusilactone B (Ob-B) is an anticancer inhibitor of VRK1-mediated BAF1 phosphorylation.

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Molecular models of Ob-B bound to BAF1 have been constructed and the binding site determined.

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Screening of 20 butanolide lactones led to the identification of new potential BAF1 binders.

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Mahubanolide, kotomolide B and epilitsenolide D2 emerge as potential BAF1 inhibitors.

Diverse cellular functions of barrier-to-autointegration factor and its roles in disease

Barrier-to-autointegration factor (BAF; encoded by BANF1) is a small highly conserved, ubiquitous and self-associating protein that coordinates with numerous binding partners to accomplish several key cellular processes. By interacting with double-stranded DNA, histones and various other nuclear proteins, including those enriched at the nuclear envelope, BAF appears to be essential for replicating cells to protect the genome and enable cell division. Cellular processes, such as innate immunity, post-mitotic nuclear reformation, repair of interphase nuclear envelope rupture, genomic regulation, and the DNA damage and repair response have all been shown to depend on BAF. This Review focuses on the regulation of the numerous interactions of BAF, which underlie the mechanisms by which BAF accomplishes its essential cellular functions. We will also discuss how perturbation of BAF function may contribute to human disease.

Downregulation of VRK1 reduces the expression of BANF1 and suppresses the proliferative and migratory activity of esophageal cancer cells

Esophageal squamous cell carcinoma (ESCC) is a common malignancy worldwide. The disease has a poor prognosis and a low 5-year survival rate. Therefore, it is necessary to identify new strategies to optimize the treatment of ESCC. Vaccinia-related kinase (VRK1) and barrier-to-autointegration factor 1 (BANF1) are overexpressed in ESCC. In the present study, the roles of VRK1 and BANF1 were explored in the development of ESCC. In the present study, the effects of small interfering (si)RNA-induced downregulation of VRK1 on BANF1 expression were investigated as well as the effects on proliferative and migratory activity of ESCC cells. Western blot analysis indicated that the protein expression levels of BANF1 were decreased following siRNA depletion of VRK1. Furthermore, the depletion of VRK1 expression inhibited the proliferation and migration of ESCC cell lines, and flow cytometry analysis indicated that the depletion of VRK1 triggered cell cycle arrest mainly in the S phase. These results suggested that VRK1 and BANF1 may have pivotal roles in the progression of ESCC.

Absence of Nuclear p16 Is a Diagnostic and Independent Prognostic Biomarker in Squamous Cell Carcinoma of the Cervix

The tumor-suppressor protein p16 is paradoxically overexpressed in cervical cancer (CC). Despite its potential as a biomarker, its clinical value and the reasons for its failure in tumor suppression remain unclear. Our purpose was to determine p16 clinical and biological significance in CC. p16 expression pattern was examined by immunohistochemistry in 78 CC cases (high-grade squamous intraepithelial lesions (HSILs) and squamous cell carcinomas of the cervix –SCCCs). CC cell proliferation and invasion were monitored by real-time cell analysis and Transwell^® invasion assay, respectively. Cytoplasmic p16 interactors were identified from immunoprecipitated extracts by liquid chromatography-tandem mass spectrometry, and colocalization was confirmed by double-immunofluorescence. We observed that SCCCs showed significantly more cytoplasmic than nuclear p16 expression than HSILs. Importantly, nuclear p16 absence significantly predicted poor outcome in SCCC patients irrespective of other clinical parameters. Moreover, we demonstrated that cytoplasmic p16 interacted with CDK4 and other unreported proteins, such as BANF1, AKAP8 and AGTRAP, which could sequester p16 to avoid nuclear translocation, and then, impair its anti-tumor function. Our results suggest that the absence of nuclear p16 could be a diagnostic biomarker between HSIL and SCCC, and an independent prognostic biomarker in SCCC; and explain why p16 overexpression fails to stop CC growth.

Expression and Prognostic Significance of BANF1 in Triple-Negative Breast Cancer

Aim

To investigate the expression of barrier-to-autointegration factor 1 (BANF1) and its prognostic significance in triple-negative breast cancer (TNBC).

Methods

BANF1 immunohistochemical detection was performed in 60 TNBC specimens and 30 normal control tissues. Real-time PCR was performed to assess the expression of BANF1 gene in TNBC tissues and their correlations with proliferation and metastasis. Kaplan-Meier survival analysis was used to assess the effect of BANF1 expression on the relapse-free survival (RFS) of TNBC patients. Univariable and multivariable Cox proportional hazards regression model analysis was used to confirm independent prognostic factors.

Results

Expression of BANF1 in TNBC was significantly higher than that of the normal control group (p<0.001), and it was related to the status of lymph node metastasis and TNM staging (p<0.05), and not related to age and tumor size (p>0.05). BANF1 expression has a positive correlation with MKI67 and MTA1 expression (p<0.01). Univariable analysis showed that expression of BANF1, the status of lymph node metastasis and TNM stage were related to the relapse-free survival (RSF) of TNBC patients (p<0.001, p=0.001, p=0.013, respectively). Multivariable Cox regression indicated that the status of lymph node metastasis was an independent prognostic factor for TNBC patients (p<0.001). The survival curve suggested that the survival times for TNBC patients with high BANF1 expression have no difference compared with that for the low-expression patients (p>0.05).

Conclusion

Expression of BANF1 may play a role in the occurrence and development of TNBC. Lymph node metastasis was the only independent prognostic factor predicts a poor prognosis.