Dataset Information

Physical contact with endothelial cells through ?1- and ?2- integrins rescues chronic lymphocytic leukemia cells from spontaneous and drug-induced apoptosis and induces a peculiar gene expression profile in leukemic cells.

ABSTRACT:

Background

Chronic lymphocytic leukemia B cells display prolonged survival in vivo, but when cultured in vitro rapidly undergo spontaneous apoptosis. We hypothesize that interactions with endothelial cells in infiltrated tissues and during recirculation may have a pathogenic role in chronic lymphocytic leukemia.

Design and methods

We evaluated apoptosis of leukemic cells after co-culture on a monolayer of human umbilical vein endothelial cells with addition of fludarabine and antibodies that block adhesion. Then, we compared microarray-based gene expression profiles between leukemic cells at baseline and after co-culture.

Results

We found that the endothelial layer protected leukemic cells from apoptosis inducing a 2-fold mean decrement in apoptotic cells after 2 days of co-culture. Moreover, the endothelial layer decreased the sensitivity of chronic lymphocytic leukemia B cells to fludarabine-induced apoptosis. Physical contact with endothelium mediated by both ?(1)- and ?(2)- integrins is essential for the survival advantage of leukemic cells. In particular, blocking CD106 on endothelial cells or CD18 on leukemic B cells led to the almost complete abrogation of the survival advantage (>70% inhibition of viability). However, a reduction of apoptosis was also measured in leukemic cells cultured in conditioned medium collected after 2 days of co-culture, implying that survival is partially mediated by soluble factors. Overall, the contact with endothelial cells modulated 1,944 genes in chronic lymphocytic leukemia B cells, establishing a peculiar gene expression profile: up-regulation of angiogenesis-related genes, an increase of genes involved in TGF? and Wnt signaling pathways, secretion of cytokines recruiting stromal cells and macrophages and up-regulation of anti-apoptotic molecules such as Bcl2 and Survivin.

Conclusions

Our study supports the notion that endothelial cells are major players in the chronic lymphocytic leukemia microenvironment. Adhesion to endothelium strongly supports survival, protects from drug-induced apoptosis and extensively modifies the gene expression profile of leukemic cells.

SUBMITTER: Maffei R

PROVIDER: S-EPMC3366665 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Publications

Physical contact with endothelial cells through β1- and β2- integrins rescues chronic lymphocytic leukemia cells from spontaneous and drug-induced apoptosis and induces a peculiar gene expression profile in leukemic cells.

Maffei Rossana R Fiorcari Stefania S Bulgarelli Jenny J Martinelli Silvia S Castelli Ilaria I Deaglio Silvia S Debbia Giulia G Fontana Marcella M Coluccio Valeria V Bonacorsi Goretta G Zucchini Patrizia P Narni Franco F Torelli Giuseppe G Luppi Mario M Marasca Roberto R

Haematologica 20111229 6

<h4>Background</h4>Chronic lymphocytic leukemia B cells display prolonged survival in vivo, but when cultured in vitro rapidly undergo spontaneous apoptosis. We hypothesize that interactions with endothelial cells in infiltrated tissues and during recirculation may have a pathogenic role in chronic lymphocytic leukemia.<h4>Design and methods</h4>We evaluated apoptosis of leukemic cells after co-culture on a monolayer of human umbilical vein endothelial cells with addition of fludarabine and anti ...[more]

PMID: 22207686

Similar Datasets

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).