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.
Haematologica, 2012/6;97(6):952-60.
Maffei R[1], Fiorcari S, Bulgarelli J, Martinelli S, Castelli I, Deaglio S, Debbia G, Fontana M, Coluccio V, Bonacorsi G, Zucchini P, Narni F, Torelli G, Luppi M, Marasca R
Affiliations
PMID: 22207686DOI: 10.3324/haematol.2011.054924
Impact factor: 11.047
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 β(1)- and β(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 TGFβ 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.
MeSH terms
Antibodies, Neutralizing; Antineoplastic Agents; Apoptosis; B-Lymphocytes; CD18 Antigens; Cell Adhesion; Cell Communication; Coculture Techniques; Culture Media, Conditioned; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Human Umbilical Vein Endothelial Cells; Humans; Integrin beta1; Leukemia, Lymphocytic, Chronic, B-Cell; Neoplasm Proteins; Primary Cell Culture; Signal Transduction; Vascular Cell Adhesion Molecule-1; Vidarabine
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