Extracellular domain shedding of the ALK receptor mediates neuroblastoma cell migration.

Although activating mutations of the anaplastic lymphoma kinase (ALK) membrane receptor occur in ∼10% of neuroblastoma (NB) tumors, the role of the wild-type (WT) receptor, which is aberrantly expressed in most non-mutated cases, is unclear. Both WT and mutant proteins undergo extracellular domain (ECD) cleavage. Here, we map the cleavage site to Asn654-Leu655 and demonstrate that cleavage inhibition of WT ALK significantly impedes NB cell migration with subsequent prolongation of survival in mouse models. Cleavage inhibition results in the downregulation of an epithelial-to-mesenchymal transition (EMT) gene signature, with decreased nuclear localization and occupancy of ß-catenin at EMT gene promoters. We further show that cleavage is mediated by matrix metalloproteinase 9, whose genetic and pharmacologic inactivation inhibits cleavage and decreases NB cell migration. Together, our results indicate a pivotal role for WT ALK ECD cleavage in NB pathogenesis, which may be harnessed for therapeutic benefit.

Forty-five patient-derived xenografts capture the clinical and biological heterogeneity of Wilms tumor.

The lack of model systems has limited the preclinical discovery and testing of therapies for Wilms tumor (WT) patients who have poor outcomes. Herein, we establish 45 heterotopic WT patient-derived xenografts (WTPDX) in CB17 scid-/- mice that capture the biological heterogeneity of Wilms tumor (WT). Among these 45 total WTPDX, 6 from patients with diffuse anaplastic tumors, 9 from patients who experienced disease relapse, and 13 from patients with bilateral disease are included. Early passage WTPDX show evidence of clonal selection, clonal evolution and enrichment of blastemal gene expression. Favorable histology WTPDX are sensitive, whereas unfavorable histology WTPDX are resistant to conventional chemotherapy with vincristine, actinomycin-D, and doxorubicin given singly or in combination. This WTPDX library is a unique scientific resource that retains the spectrum of biological heterogeneity present in WT and provides an essential tool to test targeted therapies for WT patient groups with poor outcomes.

Chromatin modifying protein 1A (Chmp1A) of the endosomal sorting complex required for transport (ESCRT)-III family activates ataxia telangiectasia mutated (ATM) for PanC-1 cell growth inhibition.

Chromatin modifying protein 1A (Chmp1A) is a member of the Endosormal sorting complex required for transport (ESCRT)-III family whose over-expression induces growth inhibition, chromatin condensation, and p53 phosphorylation. p53 is a substrate for Ataxia telangiectasia mutated (ATM), which can be activated upon chromatin condensation. Thus, we propose that Chmp1A regulates ATM, and the nuclear localization signal (NLS) is required for ATM activation. Our data demonstrated that over-expression of full-length Chmp1A induced an increase in active, phosphorylated ATM in the nucleus, where they co-localized. It also induced an increase in phospho-p53 in the nucleus, and in vitro ATM kinase and p53 reporter activities. The intensity of phospho-p53 closely followed that of ectopically induced full-length Chmp1A, suggesting a tight correlation between Chmp1A over-expression and p53 phosphorylation. On the other hand, Chmp1A depletion (reported to promote cell growth) had minor effects on phospho-ATM and p53 expression compared to control, which had very little expression of these proteins. NLS-deleted cells showed uniform cytoplasmic-Chmp1A expression and acted like shRNA-expressing cells (cell growth promotion and minimal effect on ATM), demonstrating the significance of NLS on ATM activation and growth inhibition. C-deleted Chmp1A, detected in the cytoplasm at the enlarged vesicles, increased phospho-ATM and p53, and inhibited growth; yet it had no effect on in vitro ATM kinase or p53 reporter activities, suggesting that the C-domain is not required for ATM activation. Finally, ATM inactivation considerably reduced Chmp1A mediated growth inhibition and phosphorylation of p53, showing that Chmp1A regulates tumor growth partly through ATM signaling.