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Proteolytic processing of the nuclear factor (NF)-κB2 precursor protein p100 generates the active NF-κB2 subunit p52, which in turn transcriptionally up-regulates p100 expression. p100 also functions as an IκB molecule capable of repressing p52 activity. The biological significance of this negative feedback control loop has yet to be demonstrated in vivo. Here we show that mice deficient in p100 but with constitutive expression of p52 in lymphocytes developed fatal lung inflammation characterized by diffuse alveolar damage with marked peribronchial fibrosis. In contrast, their littermates with only p100 deficiency or constitutive expression of p52 in lymphocytes developed mild lung inflammation with perivascular lymphocyte infiltration and had a normal life span. The fatal lung inflammation is associated with high-level induction of interferon-γ and its inducible inflammatory chemokines, suggesting the involvement of a T-helper-1 immune response. These findings demonstrate the physiological relevance of the NF-κB2 p100 precursor protein in limiting the potentially detrimental effects of constitutive NF-κB2 signaling in lymphocytes.

Amplification of the oncogene MYCNis a tumorigenic event in the development of a subset of neuroblastomas that commonly consist of undifferentiated or poorly differentiated neuroblasts with unfavorable clinical outcome. The cellular origin of these neuroblasts is unknown. Additionally, the cellular functions and target cells of MYCN in neuroblastoma development remain undefined. Here we examine the cell types that drive neuroblastoma development in TH-MYCNtransgenic mice, an animal model of the human disease. Neuroblastoma development in these mice begins with hyperplastic lesions in early postnatal sympathetic ganglia. We show that both hyperplasia and primary tumors are composed predominantly of highly proliferative Phox2B+neuronal progenitors. MYCN induces the expansion of these progenitors by both promoting their proliferation and preventing their differentiation. We further identify a minor population of undifferentiated nestin+cells in both hyperplastic lesions and primary tumors that may serve as precursors of Phox2B+neuronal progenitors. These findings establish the identity of neuroblasts that characterize the tumor phenotype and suggest a cellular pathway by which MYCN can promote neuroblastoma development.

Cisplatin induces both acute and chronic nephrotoxicity during chemotherapy in cancer patients. Herein, we report the first study of single-nucleus RNA sequencing (snRNA-seq) of cisplatin-induced nephrotoxicity. Repeated low-dose cisplatin treatment (RLDC) led to decreases in renal function and kidney weight in mice at 9 weeks. The kidneys of these mice showed tubular degeneration and dilation. snRNA-seq identified 16 cell types and 17 cell clusters in these kidneys. Cluster-by-cluster comparison demonstrated cell type–specific changes in gene expression and identified a unique proximal tubule (PT) injury/repair cluster that co-expressed the injury marker Kim1 and the proliferation marker Ki-67. Compared with control, post-RLDC kidneys had 424 differentially expressed genes in PT cells, including tubular transporters and cytochrome P450 enzymes involved in lipid metabolism. snRNA-seq also revealed transcriptional changes in potential PT injury markers (Krt222, Eda2r, Ltbp2, and Masp1) and repair marker (Bex4). RLDC induced inflammation and proinflammatory cytokines (RelB, TNF-α, IL7, Ccl2, and Cxcl2) and the expression of fibrosis markers (fibronectin, collagen I, connective tissue growth factor, vimentin, and α-smooth muscle actin). Together, these results provide new insights into RLDC-induced transcriptional changes at the single-cell level that may contribute to the development of chronic kidney problems in cancer patients after cisplatin chemotherapy.

Activation of oncogenes underlies the pathogenesis of most human cancers. In neuroblastoma, amplification of the oncogene MYCNoccurs in ∼22% of cases and is associated with advanced stages of the disease and poor prognosis. Identification of other oncogenes that are consistently mutated or overexpressed in neuroblastoma is crucial for a molecular understanding of the pathogenic process. Here, we report that the oncogene Bmi-1is highly expressed in human neuroblastoma cell lines and primary tumors. Neuroblastoma development in MYCNtransgenic mice, an animal model for the human disease, was associated with a marked increase in the levels of Bmi-1 expression. Bmi-1 cooperated with MYCN in transformation of benign S-type neuroblastoma cells and avian neural crest cells by inhibiting the apoptotic activity of MYCN. Importantly, down-regulation of Bmi-1 impaired the ability of neuroblastoma cells to grow in soft agar and induce tumors in immunodeficient mice. Moreover, Bmi-1-knockdown neuroblastoma xenografts were characterized by a significant increase in the amount of Schwannian stroma, a histological feature associated with clinically favorable neuroblastomas. These findings suggest a crucial role for Bmi-1 in neuroblastoma pathogenesis and provide insights into the molecular basis of neuroblastoma heterogeneity.