Molecular and genetic alterations associated with therapy resistance and relapse of acute myeloid leukemia

Background The majority of individuals with acute myeloid leukemia (AML) respond to initial chemotherapy and achieve a complete remission, yet only a minority experience long-term survival because a large proportion of patients eventually relapse with therapy-resistant disease. Relapse therefore represents a central problem in the treatment of AML. Despite this, and in contrast to the extensive knowledge about the molecular events underlying the process of leukemogenesis, information about the mechanisms leading to therapy resistance and relapse is still limited. Purpose and content of review Recently, a number of studies have aimed to fill this gap and provided valuable information about the clonal composition and evolution of leukemic cell populations during the course of disease, and about genetic, epigenetic, and gene expression changes associated with relapse. In this review, these studies are summarized and discussed, and the data reported in them are compiled in order to provide a resource for the identification of molecular aberrations recurrently acquired at, and thus potentially contributing to, disease recurrence and the associated therapy resistance. This survey indeed uncovered genetic aberrations with known associations with therapy resistance that were newly gained at relapse in a subset of patients. Furthermore, the expression of a number of protein coding and microRNA genes was reported to change between diagnosis and relapse in a statistically significant manner. Conclusions Together, these findings foster the expectation that future studies on larger and more homogeneous patient cohorts will uncover pathways that are robustly associated with relapse, thus representing potential targets for rationally designed therapies that may improve the treatment of patients with relapsed AML, or even facilitate the prevention of relapse in the first place.(VLID)484849

Endosomal Organizers of post-Golgi trafficking in polarized epithelial cells

Epithelial cells are characterized by a polarized organization of their plasma membrane which is divided into apical and basolateral domains. This architecture is maintained by highly specific cargo sorting machinery that efficiently delivers newly synthesized polypeptides to their correct target membrane. After TGN exit apical cargo is segregated by at least two distinct sorting mechanisms into lipid-raft-dependent or lipid-raft-independent apical pathways in MDCK cells. The aim of this study was the identification of proteins which are essential for the transport of apically sorted proteins. In the first part of the current study, a member of kinesin-1 group, KIF5C, was identified as a kinesin motor for apical trafficking of sucrase-isomaltase, the marker for the raft-associated pathway, and of non-raft-associated p75. KIF5C was found by mass spectrometry in vesicle enriched fractions and on immunoisolated post-Golgi vesicles carrying apical cargo. KIF5C associates with vesicles of both raft-dependent and raft-independent pathways directly after TGN exit. The specific knockdown of KIF5C interfered the apical trafficking of both raft-associated and non-raft associated marker proteins significantly (Astanina and Jacob, 2010). In the second part, annexin XIIIb was identified in raft-independent apical trafficking by mass spectrometry, immunoblotting and confocal microscopy. Annexin XIIIb accumulated in endosomal compartments that are traversed by raft-dependent and raft-independent apical cargo after TGN release. Finally, a specific reduction of annexin XIIIb expression by RNA interference resulted in a significant decrease in the apical delivery of the raft- as well as non-raft apical markers (Astanina et al., 2010). Taken together, both proteins – KIF5C and annexin XIIIb – act as endosomal organizers of apical protein trafficking in polarized epithelial cells. Based on the confocal microscopy studies and TGN release experiments we came to the conclusion that both proteins function on the first transport steps after TGN exit and accomplish trafficking of raft-associated, as well as non-raft-associated apical cargo

Endosomal Organizers of post-Golgi trafficking in polarized epithelial cells

Epithelial cells are characterized by a polarized organization of their plasma membrane which is divided into apical and basolateral domains. This architecture is maintained by highly specific cargo sorting machinery that efficiently delivers newly synthesized polypeptides to their correct target membrane. After TGN exit apical cargo is segregated by at least two distinct sorting mechanisms into lipid-raft-dependent or lipid-raft-independent apical pathways in MDCK cells. The aim of this study was the identification of proteins which are essential for the transport of apically sorted proteins. In the first part of the current study, a member of kinesin-1 group, KIF5C, was identified as a kinesin motor for apical trafficking of sucrase-isomaltase, the marker for the raft-associated pathway, and of non-raft-associated p75. KIF5C was found by mass spectrometry in vesicle enriched fractions and on immunoisolated post-Golgi vesicles carrying apical cargo. KIF5C associates with vesicles of both raft-dependent and raft-independent pathways directly after TGN exit. The specific knockdown of KIF5C interfered the apical trafficking of both raft-associated and non-raft associated marker proteins significantly (Astanina and Jacob, 2010). In the second part, annexin XIIIb was identified in raft-independent apical trafficking by mass spectrometry, immunoblotting and confocal microscopy. Annexin XIIIb accumulated in endosomal compartments that are traversed by raft-dependent and raft-independent apical cargo after TGN release. Finally, a specific reduction of annexin XIIIb expression by RNA interference resulted in a significant decrease in the apical delivery of the raft- as well as non-raft apical markers (Astanina et al., 2010). Taken together, both proteins – KIF5C and annexin XIIIb – act as endosomal organizers of apical protein trafficking in polarized epithelial cells. Based on the confocal microscopy studies and TGN release experiments we came to the conclusion that both proteins function on the first transport steps after TGN exit and accomplish trafficking of raft-associated, as well as non-raft-associated apical cargo

Additional file 3: Table S3. of Molecular and genetic alterations associated with therapy resistance and relapse of acute myeloid leukemia

Non-synonymous mutations recurrently acquired (Table S3A) or lost (Table S3B) at relapse of AML as determined by next generation sequencing based methods. (XLSX 22 kb

Lipid droplets as a novel cargo of tunnelling nanotubes in endothelial cells

Intercellular communication is a fundamental process in the development and functioning of multicellular organisms. Recently, an essentially new type of intercellular communication, based on thin membrane channels between cells, has been reported. These structures, termed intercellular or tunnelling nanotubes (TNTs), permit the direct exchange of various components or signals (e.g., ions, proteins, or organelles) between non-adjacent cells at distances over 100 μm. Our studies revealed the presence of tunnelling nanotubes in microvascular endothelial cells (HMEC-1). The TNTs were studied with live cell imaging, environmental scanning electron microscopy (ESEM), and coherent anti-Stokes Raman scattering spectroscopy (CARS). Tunneling nanotubes showed marked persistence: the TNTs could connect cells over long distances (up to 150 μm) for several hours. Several cellular organelles were present in TNTs, such as lysosomes and mitochondria. Moreover, we could identify lipid droplets as a novel type of cargo in the TNTs. Under angiogenic conditions (VEGF treatment) the number of lipid droplets increased significantly. Arachidonic acid application not only increased the number of lipid droplets but also tripled the extent of TNT formation. Taken together, our results provide the first demonstration of lipid droplets as a cargo of TNTs and thereby open a new field in intercellular communication research

Lipid droplets as a novel cargo of tunnelling nanotubes in endothelial cells

Intercellular communication is a fundamental process in the development and functioning of multicellular organisms. Recently, an essentially new type of intercellular communication, based on thin membrane channels between cells, has been reported. These structures, termed intercellular or tunnelling nanotubes (TNTs), permit the direct exchange of various components or signals (e.g., ions, proteins, or organelles) between non-adjacent cells at distances over 100 μm. Our studies revealed the presence of tunnelling nanotubes in microvascular endothelial cells (HMEC-1). The TNTs were studied with live cell imaging, environmental scanning electron microscopy (ESEM), and coherent anti-Stokes Raman scattering spectroscopy (CARS). Tunneling nanotubes showed marked persistence: the TNTs could connect cells over long distances (up to 150 μm) for several hours. Several cellular organelles were present in TNTs, such as lysosomes and mitochondria. Moreover, we could identify lipid droplets as a novel type of cargo in the TNTs. Under angiogenic conditions (VEGF treatment) the number of lipid droplets increased significantly. Arachidonic acid application not only increased the number of lipid droplets but also tripled the extent of TNT formation. Taken together, our results provide the first demonstration of lipid droplets as a cargo of TNTs and thereby open a new field in intercellular communication research