title: Caspase-3-dependent cleavage of Bcl-xL in the stroma exosomes is required for their uptake by hematological malignant cells.
abstract: The intercellular crosstalk between hematological malignancies and the tumor microenvironment is mediated by cell-to-cell interactions and soluble factors. One component of the secretome that is gaining increasing attention is the extracellular vesicles and, in particular, the exosomes. Apart from the role as vectors of molecular information, exosomes have been shown to possess intrinsic biological activity. In this study, we found that caspase-3 is activated in L88 bone marrow stroma cell-derived exosomes and identified 1 of the substrates to be the antiapoptotic protein Bcl-xL. The cleaved Bcl-xL is found in a panel of normal and cancer cell-derived exosomes and is localized on the outer leaflet of the exosomal membrane. Incubation of the exosomes with a caspase-3 inhibitor or the pan-caspase inhibitor prevents the cleavage of Bcl-xL. Importantly, MCF-7 cell-derived exosomes that are caspase-3-deficient are enriched in full-length Bcl-xL, whereas ectopic expression of caspase-3 restores the cleavage of Bcl-xL. Chemical inhibition of Bcl-xL with ABT737 or molecular inhibition by using the D61A and D76A Bcl-xL mutant leads to a significant decrease in the uptake of exosomes by hematopoietic malignant cells. These data indicate that the cleaved Bcl-xL is required for the uptake of exosomes by myeloma and lymphoma cells, leading to their increased proliferation. In summary, we demonstrate for the first time that Bcl-xL is an exosomal caspase-3 substrate and that this processing is required for the uptake of exosomes by recipient cells.
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Ioulia
authors.initials: I
authors.lastname: Vardaki
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Claire
authors.initials: C
authors.lastname: Sanchez
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Pedro
authors.initials: P
authors.lastname: Fonseca
authors.affiliation: Department of Environmental Medicine, and.
authors.forename: Magnus
authors.initials: M
authors.lastname: Olsson
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Chioureas
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: George
authors.initials: G
authors.lastname: Rassidakis
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Anders
authors.initials: A
authors.lastname: Ullén
authors.affiliation: Department of Environmental Medicine, and.
authors.forename: Boris
authors.initials: B
authors.lastname: Zhivotovsky
authors.affiliation: Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Björkholm
authors.affiliation: Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet and Karolinska University Hospital Solna, Stockholm, Sweden; and.
authors.forename: Theocharis
authors.identifier: 0000-0001-5754-6950
authors.initials: T
authors.lastname: Panaretakis
mesh_terms: D019943:Amino Acid Substitution; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism*; D055354:Exosomes / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D061986:MCF-7 Cells; D008297:Male; D009101:Multiple Myeloma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020125:Mutation, Missense; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: C494811:BCL2L1 protein, human; D051020:bcl-X Protein; C505407:CASP3 protein, human; D053148:Caspase 3