Project description:Chronic lymphocytic leukemic B cells (CLL) reside in close contact with activated endothelial cells (EC) in infiltrated tissues. Here, we investigated the interactions between EC and CLL cells, highlighting molecular networks involved in this cellular crosstalk. We co-cultured purified CLL cells on HUVEC monolayer (HC) or in medium alone. We found that EC protected CLL from spontaneous apoptosis. A 2.2-fold increase in relative viability in IGHV mutated CLL and a 6.1-fold increase in IGHV unmutated CLL was detected in co-culture. Moreover, the endothelial cell layer decreased the in vitro sensitivity of CLL cells to Fludarabine-induced apoptosis. Physical contact with EC is essential for protection to apoptosis. The insertion of a microporous membrane or blocking adhesion with anti-CD106 and anti-CD18 antibodies determined the complete abrogation of apoptosis protection. On the other hand, a reduction of apoptosis was measured in CLL cells cultured with conditioned medium collected from HC, implying that survival is partially mediated by soluble factors. Overall 1944 genes were modulated in CLL by co-culture. The EC contact seem to determine on CLL a kind of microenvironmental-driven angiogenic switch, improve the secretion of cytokines regulating tissue elements such as stromal cells and macrophages and also increase anti-apoptotic molecules. Our study support the line of evidence indicating endothelial cells as a major player in the CLL-infiltrated microenvironments are able to create a vicious cycle of cooperation that strongly sustains leukemic cell survival, protects CLL from drug-induced apoptosis and widely modifies CLL phenotype. Large-scale gene expression profiling (GEP) was performed on total RNA extracted from purified CD19+ cells isolated from 9 individual CLL patients which were separated in 3 experimental subsets: (i) freshly isolated cells (CLL baseline), (ii) CLL cells cultured in medium alone for 48 hours (CLL only) and (iii) CLL cells co-cultured 48h on HUVEC layer (CLL HC).

Project description:Bi-directional communication with the microenvironment is essential for homing and survival of cancer cells with implications for disease biology and behaviour. In chronic lymphocytic leukemia (CLL) the role of the microenvironment on malignant cell behaviour is well described. However, how CLL cells engage and recruit nurturing cells is poorly characterised. Here we demonstrate that CLL cells secrete exosomes that are nanovesicles originating from the fusion of multivesicular bodies with the plasma membrane, to shuttle proteins, lipids, microRNAs (miR) and mRNAs to recipient cells. We characterise and confirm the size (50 - 100 nm) and identity of the CLL-derived exosomes by Electron microscopy (EM), Atomic force microscopy (AFM), flow cytometry and western blotting using both exosomes-specific and CLL-specific markers. Incubation of CLL-exosomes, derived either from cell culture supernatants or from patient plasma, with human stromal cells shows that they are readily taken up into endosomes, and induce expression of genes such as c-fos and ATM as well as enhance proliferation of recipient HS-5 cells. Furthermore, we show that CLL exosomes encapsulate abundant small RNAs and are enriched in certain miRs and specifically hsa-miR-202-3p. We suggest that such specific packaging of miR-202-3p impacts on the expression of 'suppressor of fused' (Sufu), a Hedgehog (Hh) signalling intermediate, in the parental CLL cells. Thus, our data show that CLL cells secrete exosomes that alter the transcriptome and behaviour of recipient cells. Such communication with microenvironment is likely to have an important role in CLL disease biology. miR analysis was carried out on 3 exosomal samples and 3 corresponding cellular samples from CLL patients. Exosomes are a discrete population of small (50-100 nm diameter) EVs of endosomal origin with a lipid membrane bilayer and a cup-shaped morphology. We used common reference design which allows visualization of variations between the samples. Each sample equals one array and each sample compared with common reference (Pool). The pool or common reference was a collection of 23 RNA samples isolated from 23 CLL cases. We hypothesised that CLL derived exosomes should contain unique miRs that are reflective of CLL cell content and additionally relevant for disease biology.

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Effect of NF-kappaB activation in bone marrow stromal cells co-cultured with CLL cells

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