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Vaccines are proving to be highly effective in controlling hospitalization and deaths associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as shown by clinical trials and real-world evidence. However, a deadly second wave of coronavirus disease 2019 (COVID-19), infected by SARS-CoV-2 variants, especially the Delta (B.1.617.2) variant, with an increased number of post-vaccination breakthrough infections were reported in the world recently. Actually, Delta variant not only resulted in a severe surge of vaccine breakthrough infections which was accompanied with high viral load and transmissibility, but also challenged the development of effective vaccines. Therefore, the biological characteristics and epidemiological profile of Delta variant, the current status of Delta variant vaccine breakthrough infections and the mechanism of vaccine breakthrough infections were discussed in this article. In addition, the significant role of the Delta variant spike (S) protein in the mechanism of immune escape of SARS-CoV-2 was highlighted in this article. In particular, we further discussed key points on the future SARS-CoV-2 vaccine research and development, hoping to make a contribution to the early, accurate and rapid control of the COVID-19 epidemic.

Biliary atresia (BA) is a severe inflammatory and fibrosing neonatal cholangiopathy disease characterized by progressive obstruction of extrahepatic bile ducts, resulting in cholestasis and progressive hepatic failure. Cholestasis may play an important role in the inflammatory and fibrotic pathological processes, but its specific mechanism is still unclear. Necroptosis mediated by Z-DNA-binding protein 1 (ZBP1)/phosphorylated-mixed lineage kinase domain-like pseudokinase (p-MLKL) is a prominent pathogenic factor in inflammatory and fibrotic diseases, but its function in BA remains unclear. Here, we aim to determine the effect of macrophage necroptosis in the BA pathology, and to explore the specific molecular mechanism. We found that necroptosis existed in BA livers, which was occurred in liver macrophages. Furthermore, this process was mediated by ZBP1/p-MLKL, and the upregulated expression of ZBP1 in BA livers was correlated with liver fibrosis and prognosis. Similarly, in the bile duct ligation (BDL) induced mouse cholestatic liver injury model, macrophage necroptosis mediated by ZBP1/p-MLKL was also observed. In vitro, conjugated bile acid-glycodeoxycholate (GDCA) upregulated ZBP1 expression in mouse bone marrow-derived monocyte/macrophages (BMDMs) through sphingosine 1-phosphate receptor 2 (S1PR2), and the induction of ZBP1 was a prerequisite for the enhanced necroptosis. Finally, after selectively knocking down of macrophage S1pr2 in vivo, ZBP1/p-MLKL-mediated necroptosis was decreased, and further collagen deposition was markedly attenuated in BDL mice. Furthermore, macrophage Zbp1 or Mlkl specific knockdown also alleviated BDL-induced liver injury/fibrosis. In conclusion, GDCA/S1PR2/ZBP1/p-MLKL mediated macrophage necroptosis plays vital role in the pathogenesis of BA liver fibrosis, and targeting this process may represent a potential therapeutic strategy for BA.

Wilms tumor (WT), the most common pediatric renal malignancy, exhibits a relatively low mutational burden compared to adult cancers, which hinders the development of targeted therapies. To elucidate the molecular landscape of WT, we perform integrative proteomic, phosphoproteomic, transcriptomic, and whole-exome sequencing analyses of WT and normal kidney tissue adjacent to tumor. Our multi-omics approach uncovers prognostic genetic alterations, distinct molecular subgroups, immune microenvironment features, and potential biomarkers and therapeutic targets. Proteome- and transcriptome-based stratification identifies three molecular subgroups with unique signatures, correlating with different histopathological subtypes and putative cellular origins at different stages of embryonic kidney development. Notably, we identify EHMT2 as a promising prognostic biomarker and therapeutic target associated with epigenetic regulation and Wnt/β-catenin pathway. In this work, we provide a comprehensive molecular characterization of WT, offering valuable insights into its pathogenesis and a foundational resource for future therapeutic development. Wilms tumours are the most common malignant kidney tumour type in children, and their low mutational burden has impeded the development of targeted therapies. Here, the authors perform a proteogenomic characterisation of Wilms tumours, revealing molecular subtypes with different clinical features and identifying EHMT2 as a potential prognostic marker and therapeutic target.

Pediatric hepatoblastoma (HB) is the most common primary liver malignancy in infants and children. With great diversity and plasticity, tumor-infiltrating neutrophils were one of the most determining factors for poor prognosis in many malignant tumors. In this study, through bulk RNA sequencing for sorted blood and tumor-infiltrated neutrophils and comparison of neutrophils in tumor and para-tumor tissue by single-cell sequencing, we found that intratumoral neutrophils were composed of heterogenous functional populations at different development stages. Our study showed that terminally differentiated neutrophils with active ferroptosis prevailed in tumor tissue, whereas, in para-tumor, pre-fate naïve neutrophils were dominant and ferroptotic neutrophils dispersed in a broad spectrum of cell maturation. Gene profiling and in vitro T-cell coculture experiment confirmed that one of main functional intratumoral neutrophils was mainly immunosuppressive, which relied on the activation of ferroptosis. Combining the bulk RNA-seq, scRNA-seq data, and immunochemistry staining of tumor samples, CXCL12/CXCR4 chemotaxis pathway was suggested to mediate the migration of neutrophils in tumors as CXCR4 highly expressed by intratumoral neutrophils and its ligand CXCL12 expressed much higher level in tumor than that in para-tumor. Moreover, our study pinpointed that infiltrated CXCR4 hi neutrophils, regardless of their differential distribution of cell maturation status in HB tumor and para-tumor regions, were the genuine perpetrators for immune suppression. Our data characterized the ferroptosis-dependent immunosuppression energized by intratumoral CXCR4 expression neutrophils and suggest a potential cell target for cancer immunotherapies.

Background This study was performed to identify risk factors associated with recurrence of hepatoblastoma. Methods A retrospective study was conducted on 56 patients with hepatoblastoma from 2012 to 2015 in Beijing Children’s Hospital. Pretreatment extension stage (PRETEXT), serum alpha fetoprotein (AFP) value, change trend of tumors after treatment and some other clinical characteristics were collected and analyzed. The comparison of independent variables that were not distributed normally was performed with the log-rank test. Results Twenty-eight patients with tumour recurrence and 28 patients without recurrence were included in this study, and the median age at presentation was 46.5 (26, 71.5) months. There was a significant difference in the 3-year recurrence-free survival (RFS) probability between patients aged over 54 months and those younger than 54 months ( p  = 0.007). After neoadjuvant chemotherapy, the chance of recurrence in partial response (PR) patients was significantly lower than that in stable disease (SD) patients ( p  = 0.004). The 3-year RFS rate of patients with a reduction in AFP of more than 60% after neoadjuvant chemotherapy was significantly higher than that of patients with a reduction of less than 60% ( p  = 0.005). The postoperative follow-up revealed that patients whose postoperative AFP fell to normal levels within 6 months of the start of treatment had a 3-year RFS rate of 68.6%, which is higher than that of patients whose AFP fell below the normal range after 6 months ( p  = 0.0005). Finally, the multivariate analysis by Cox regression showed that AFP decreased by less than 60% and tumour size decreased by less than 50% after neoadjuvant chemotherapy were significant independent prognostic risk factors for the 3-year RFS rate. The other clinical features were not significantly associated with tumour recurrence in this study. Conclusions Through this study, we concluded that the prognosis of childhood HB is related to the age at presentation and the response of chemotherapy. The results of the multivariate analysis showed that AFP decreased by less than 60% and tumour size decreased by less than 50% after neoadjuvant chemotherapy were significant independent prognostic risk factors. These findings can be helpful to evaluate therapeutic effects and predict prognosis.

Importance Cancer is the main cause of death by disease in children. Children experience the highest incidence of cancer in the first year of life. However, there is no comprehensive registration system for children with tumors in China. Objective To summarize the diagnosis and treatment of infant cancer and analyze the status of standardized diagnosis and management among several treatment centers in Beijing, China, thereby providing evidence to guide further clinical research. Methods From January 1, 2010 to December 31, 2019, patients with newly diagnosed infantile malignant solid tumors were admitted to six large tertiary pediatric solid tumor diagnosis and treatment centers in Beijing. The epidemiology, clinical features, and therapeutic effects of tumors in these patients were analyzed retrospectively. All patients were followed up until March 31, 2020. Results In total, 938 patients were enrolled in this study. There were 530 boys (56.5%) and 408 girls (43.5%); the median age was 6.0 months (range, 0–12.0 months). The three most common tumors were retinoblastoma in 366 patients (39.0%), neuroblastoma in 266 patients (28.4%), hepatoblastoma in 133 patients (14.2%), and central nervous system tumors in 52 patients (5.5%). The estimated 5‐year overall survival rate was 81.3% ± 1.8%, and the 5‐year event‐free survival rate was 71.8% ± 2.9%. The 5‐year overall survival rates of non‐rhabdomyosarcoma soft tissue sarcoma, neuroblastoma, and retinoblastoma were 100%, 88% ± 2.2%, and 86.9% ±2.1%, respectively. The 5‐year event‐free survival rates were 81.1% ± 2.7% for neuroblastoma, 81.6% ± 9.8% for non‐rhabdomyosarcoma soft tissue sarcoma, and 72.7% ± 14.1% for extracranial malignant germ cell tumors. Interpretation The three most common infantile malignant solid tumors were retinoblastoma, neuroblastoma, and hepatoblastoma. Multidisciplinary combined diagnosis and treatment is needed for infantile tumors. Children experience the highest incidence of cancer in the first year of life. We summarized 10‐years data of infantile malignant solid tumors from multiple centers in Beijing, China to provide evidence to support further clinical studies.

Background Neuroblastoma (NB) is a highly heterogeneous tumor, and more than half of newly diagnosed NB are associated with extensive metastases. Accurately characterizing the heterogeneity of whole-body tumor lesions remains clinical challenge. This study aims to quantify whole-tumoral metabolic heterogeneity (WMH) derived from whole-body tumor lesions, and investigate the prognostic value of WMH in NB. Methods We retrospectively enrolled 95 newly diagnosed pediatric NB patients in our department. Traditional semi-quantitative PET/CT parameters including the maximum standardized uptake value (SUVmax), the mean standardized uptake value (SUVmean), the peak standardized uptake value (SUVpeak), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were measured. These PET/CT parameters were expressed as PSUVmax, PSUVmean, PSUVpeak, PMTV, PTLG for primary tumor, WSUVmax, WSUVmean, WSUVpeak, WMTV, WTLG for whole-body tumor lesions. The metabolic heterogeneity was quantified using the areas under the curve of the cumulative SUV-volume histogram index (AUC-CSH index). Intra-tumoral metabolic heterogeneity (IMH) and WMH were extracted from primary tumor and whole-body tumor lesions, respectively. The outcome endpoints were overall survival (OS) and progression-free survival (PFS). Survival analysis was performed utilizing the univariate and multivariate Cox proportional hazards regression. The optimal cut-off values for metabolic parameters were obtained by receiver operating characteristic curve (ROC). Results During follow up, 27 (28.4%) patients died, 21 (22.1%) patients relapsed and 47 (49.5%) patients remained progression-free survival, with a median follow-up of 35.0 months. In survival analysis, WMTV and WTLG were independent indicators of PFS, and WMH was an independent risk factor of PFS and OS. However, IMH only showed association with PFS and OS. In addition to metabolic parameters, the International Neuroblastoma Staging System (INSS) was identified as an independent risk factor for PFS, and neuron-specific enolase (NSE) served as an independent predictor of OS. Conclusion WMH was an independent risk factor for PFS and OS, suggesting its potential as a novel prognostic marker for newly diagnosed NB patients.

Background Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disease. Some children with OMS also have neuroblastoma (NB). We and others have previously documented that serum IgG from children with OMS and NB induces neuronal cytolysis and activates several signaling pathways. However, the mechanisms underlying OMS remain unclear. Here, we investigated whether nitric oxide (NO) from activated microglias and its cascade contribute to neuronal cytolysis in pediatric OMS. Methods The activation of cultured cerebral cortical and cerebellar microglias incubated with sera or IgG isolated from sera of children with OMS and NB was measured by the expression of the activation marker, cytokines, and NO. Neuronal cytolysis was determined after exposing to IgG-treated microglia-conditioned media. Using inhibitors and activators, the effects of NO synthesis and its intracellular cascade, namely soluble guanylyl cyclase (sGC) and protein kinase G (PKG), on neuronal cytolysis were evaluated. Results Incubation with sera or IgG from children with OMS and NB increased the activation of cerebral cortical and cerebellar microglias, but not the activation of astrocytes or the cytolysis of glial cells. Moreover, the cytolysis of neurons was elevated by conditioned media from microglias incubated with IgG from children with OMS and NB. Furthermore, the expression of NO, sGC, and PKG was increased. Neuronal cytolysis was relieved by the inhibitors of NO signaling, while neuronal cytolysis was exacerbated by the activators of NO signaling but not proinflammatory cytokines. The cytolysis of neurons was suppressed by pretreatment with the microglial inhibitor minocycline, a clinically tested drug. Finally, increased microglial activation did not depend on the Fab fragment of serum IgG. Conclusions Serum IgG from children with OMS and NB potentiates microglial activation, which induces neuronal cytolysis through the NO/sGC/PKG pathway, suggesting an applicability of microglial inhibitor as a therapeutic candidate.

Background Neuroblastoma (NB) tumor rupture is a rare oncology emergency with a poor prognosis. We aimed to evaluate patient clinical characteristics and risk factors for ruptured NB. Methods A retrospective study of 47 patients with confirmed NB rupture between January 2009 and January 2019 at Beijing Children’s Hospital was conducted. To identify tumor rupture risk factors in high-risk NB patients, we included 93 consecutive non-ruptured high-risk NB patients from January 2017 to January 2019. Results The median age at presentation was 29 months (adrenal and retroperitoneum origin) for 47 ruptured NB patients. Spontaneous tumor rupture occurred in 22 cases; 18 cases occurred during or after the first chemotherapy cycle, and 7 occurred after core needle biopsy. Five patients died of tumor rupture, and 17 patients’ parents refused further antitumor therapy. Among the 25 remaining patients, 6 survived without disease, 5 received ongoing treatment and achieved stable disease, and 14 died. According to multivariate logistic regression analysis, a maximum primary tumor diameter > 13.20 cm and MYCN gene amplification were independent risk factors for tumor rupture within high-risk NB. Conclusions Tumor rupture is an uncommon, life-threatening event for NB patients; these patients are most likely to have poor outcomes due to tumor recurrence or rapid progression. Several treatment modalities, including symptomatic support therapy and chemotherapy, are important for saving lives and for developing NB risk-based treatment in the future.

BackgroundPancreatoblastoma is a very rare malignant pancreatic tumor in children. Pancreatoblastoma is the most common pancreatic tumor in children less than 10 years of age, accounting for 25% of the pancreatic neoplasm. There were only a few published literatures about the standardized diagnostic and management protocol for PB in the last decade.ObjectiveTo summarize our experience in the management of pancreatoblastoma in children and adolescents with emphasis on the presentation, diagnosis, treatment, and outcomes. A management strategy will also be discussed.MethodsThis was a retrospective case-series study of all pancreatoblastoma in patients < 18 years of age who were treated at Beijing children’s hospital (BCH) from January 2002–January 2015. The diagnoses of PB were confirmed by histopathology analysis of the resected specimen. The variables being analyzed included patient demographics, age at diagnosis, clinical presentation, tumor size, metastasis if present, tumor markers (AFP), type of surgery, length of follow-up, and outcome. The assessment of the tumor location, size, extent of the tumor, and distant metastasis was made by ultrasound (US), computed tomography (CT), and/or magnetic resonance imaging (MRI).Result21 patients with pancreatoblastoma were diagnosed at a median age of 4 years, 7 girls, and 14 boys. The diagnosis of pancreatoblastoma was identified by the histology examination. The most common syndrome was abdominal mass (n = 11), followed by abdominal pain (N = 10), elevated serum AFP levels were noted in almost all cases (17/18), 17 patients with disease initially unresectable on diagnosis accepted neo-adjuvant chemotherapy consisting of CDV, OPEC, PLADO, IEV, and AVCP. All patients underwent surgery, including pancreaticoduodenectomy (Whipple’s procedure), the Pylorus-preserving pancreaticoduodenectomy (traverse-Longmire procedure), Spleen-preserving distal pancreatectomy, and distal pancreatectomy with en bloc splenectomy, Roux-en-Y end-to-end pancreatojejunostomy. In all, 13 children were disease free with a median follow-up of 53 months (range 11–156 months).ConclusionsThe pancreatoblastoma in children and adolescents is a malignant tumor. Complete resection combined with chemotherapy is associated with long-term survival. For the unresectable tumor at diagnosis, preoperative chemotherapy was recommended to reduce tumor volume. AFP is critical for diagnosis and monitoring the disease as a tumors marker.