RESUMO
Micronuclei are extra-nuclear bodies containing whole chromosomes that were not incorporated into the nucleus after cell division or damaged chromosome fragments. Even though the link between micronuclei and DNA damage is described for a long time, little is known about the functional organization of micronuclei and their contribution to tumorigenesis. We showed fusions between micronuclear membranes and lysosomes by electron microscopy and linked lysosome function to DNA damage levels in micronuclei. In addition, micronuclei drastically differ from primary nuclei in nuclear envelope composition, with a significant increase in the relative amount of nuclear envelope proteins LBR and emerin and a decrease in nuclear pore proteins. Strikingly, micronuclei lack active proteasomes, as the processing subunits and other factors of the ubiquitin proteasome system. Moreover, micronuclear chromatin shows a higher degree of compaction as compared to primary nuclei. The specific aberrations identified in micronuclei and the potential functional consequences of these defects may contribute to the role of micronuclei in catastrophic genomic rearrangements.
Assuntos
Núcleo Celular/ultraestrutura , Cromatina/ultraestrutura , Cromotripsia , Instabilidade Genômica , Membrana Nuclear/ultraestrutura , Complexo de Endopeptidases do Proteassoma/fisiologia , Linhagem Celular , Núcleo Celular/metabolismo , Núcleo Celular/patologia , Cromatina/química , Dano ao DNA , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Fibroblastos/ultraestrutura , Expressão Gênica , Humanos , Lisossomos/metabolismo , Lisossomos/ultraestrutura , Fusão de Membrana , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Testes para Micronúcleos , Nocodazol/farmacologia , Membrana Nuclear/química , Membrana Nuclear/metabolismo , Membrana Nuclear/patologia , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Complexo de Endopeptidases do Proteassoma/ultraestrutura , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Epitélio Pigmentado da Retina/efeitos dos fármacos , Epitélio Pigmentado da Retina/metabolismo , Epitélio Pigmentado da Retina/ultraestrutura , Receptor de Lamina BRESUMO
In chronic lymphocytic leukemia (CLL), monocytes and macrophages are skewed toward protumorigenic phenotypes, including the release of tumor-supportive cytokines and the expression of immunosuppressive molecules such as programmed cell death 1 ligand 1 (PD-L1). To understand the mechanism driving protumorigenic skewing in CLL, we evaluated the role of tumor cell-derived exosomes in the cross-talk with monocytes. We carried out RNA sequencing and proteome analyses of CLL-derived exosomes and identified noncoding Y RNA hY4 as a highly abundant RNA species that is enriched in exosomes from plasma of CLL patients compared with healthy donor samples. Transfer of CLL-derived exosomes or hY4 alone to monocytes resulted in key CLL-associated phenotypes, including the release of cytokines, such as C-C motif chemokine ligand 2 (CCL2), CCL4, and interleukin-6, and the expression of PD-L1. These responses were abolished in Toll-like receptor 7 (TLR7)-deficient monocytes, suggesting exosomal hY4 as a driver of TLR7 signaling. Pharmacologic inhibition of endosomal TLR signaling resulted in a substantially reduced activation of monocytes in vitro and attenuated CLL development in vivo. Our results indicate that exosome-mediated transfer of noncoding RNAs to monocytes contributes to cancer-related inflammation and concurrent immune escape via PD-L1 expression.