ABSTRACT
Identification of specific oncogenic gene changes has enabled the modern generation of targeted cancer therapeutics. In high-grade serous ovarian cancer (OV), the bulk of genetic changes is not somatic point mutations, but rather somatic copy-number alterations (SCNAs). The impact of SCNAs on tumour biology remains poorly understood. Here we build haploinsufficiency network analyses to identify which SCNA patterns are most disruptive in OV. Of all KEGG pathways (N=187), autophagy is the most significantly disrupted by coincident gene deletions. Compared with 20 other cancer types, OV is most severely disrupted in autophagy and in compensatory proteostasis pathways. Network analysis prioritizes MAP1LC3B (LC3) and BECN1 as most impactful. Knockdown of LC3 and BECN1 expression confers sensitivity to cells undergoing autophagic stress independent of platinum resistance status. The results support the use of pathway network tools to evaluate how the copy-number landscape of a tumour may guide therapy.
Subject(s)
Alleles , Haploinsufficiency/genetics , Mutation/genetics , Ovarian Neoplasms/genetics , Autophagy/genetics , Cell Line, Tumor , Cell Proliferation/genetics , DNA Copy Number Variations/genetics , Drug Delivery Systems , Female , Genes, Neoplasm , Humans , Ovarian Neoplasms/metabolism , Ovarian Neoplasms/pathology , Proteostasis/geneticsABSTRACT
High-risk neuroblastoma is associated with an overall survival rate of 30-50%. Neuroblastoma-expressed cell adhesion receptors of the integrin family impact cell adhesion, migration, proliferation and survival. Integrin α4 is essential for neural crest cell motility during development, is highly expressed on leukocytes, and is critical for transendothelial migration. Thus, cancer cells that express this receptor may exhibit increased metastatic potential. We show that α4 expression in human and murine neuroblastoma cell lines selectively enhances in vitro interaction with the alternatively spliced connecting segment 1 of fibronectin, as well as vascular cell adhesion molecule-1 and increases migration. Integrin α4 expression enhanced experimental metastasis in a syngeneic tumor model, reconstituting a pattern of organ involvement similar to that seen in patients. Accordingly, antagonism of integrin α4 blocked metastasis, suggesting adhesive function of the integrin is required. However, adhesive function was not sufficient, as mutants of integrin α4 that conserved the matrix-adhesive and promigratory function in vitro were compromised in their metastatic capacity in vivo. Clinically, integrin α4 is more frequently expressed in non-MYNC amplified tumors, and is selectively associated with poor prognosis in this subset of disease. These results reveal an unexpected role for integrin α4 in neuroblastoma dissemination and identify α4 as a potential prognostic indicator and therapeutic target.
Subject(s)
Gene Expression Regulation, Neoplastic , Integrin alpha4/genetics , Liver Neoplasms/genetics , Nervous System Neoplasms/genetics , Neuroblastoma/genetics , Nuclear Proteins/genetics , Oncogene Proteins/genetics , Animals , Cell Adhesion , Cell Line, Tumor , Cell Movement , Humans , Integrin alpha4/metabolism , Intercellular Signaling Peptides and Proteins , Liver Neoplasms/metabolism , Liver Neoplasms/secondary , Lymphatic Metastasis , Mice , N-Myc Proto-Oncogene Protein , Neoplasm Transplantation , Nervous System Neoplasms/metabolism , Nervous System Neoplasms/pathology , Neuroblastoma/metabolism , Neuroblastoma/secondary , Nuclear Proteins/metabolism , Oncogene Proteins/metabolism , Peptides/genetics , Peptides/metabolism , Prognosis , Signal Transduction , Survival Analysis , Vascular Cell Adhesion Molecule-1/genetics , Vascular Cell Adhesion Molecule-1/metabolismABSTRACT
Caspase-8 can trigger cell death following prodomain-mediated recruitment to the 'death-inducing signaling complex.' The prodomain consists of two death effector domain (DED) motifs that undergo homotypic interactions within the cell. Aside from mediating recruitment of procaspase-8, the prodomains have also been implicated in regulating cell survival, proliferation, death, senescence, differentiation, and substrate attachment. Here, we perform the initial characterization of a novel isoform of caspase-8, designated caspase-8 isoform 6 (Casp-8.6), which encodes both prodomain DEDs followed by a unique C-terminal tail. Casp-8.6 is detected in cells of the hematopoietic compartment as well as several other tissues. When Casp-8.6 expression is reconstituted in caspase-8-deficient cells, Casp-8.6 does not significantly impact cellular proliferation, contrasting with our previous results using a domain-defined 'DED-only' construct that lacks the C-terminal tail. Like the DED-only construct, Casp-8.6 also robustly forms 'death effector' filaments, but in contrast to the DED construct, it does not exhibit a dependence upon intact microtubules to scaffold filament formation. Both types of death effector filaments promote apoptosis when expressed in the presence of full length caspase-8 (isoform 1). Together, the results implicate Casp-8.6 as a new physiological modulator of apoptosis.
