Stem Cells and Experimental Leukemia Can Be Distinguished by Lipid Raft Protein Composition

Abstract

The stable transfection of the canine CD34(-) multipotent cell line DO64 with retroviral constructs containing the cDNA for the canine major histocompatibility complex (MHC) class II DR genes led to the cell clone DO64#14, which is characterized by malignant transformation and tumor growth in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. The additional expression of p27(kip-1) in the transformed cell clone partially reversed the malignant phenotype. Because several proteins associated with lipid rafts are involved in signal transduction and because changes of lipid raft composition are linked to the pathogenesis of leukemias, raft-associated proteins in DO64 cells and the deduced transformed cell clones were compared using a proteomic approach. Raft-associated proteins were separated by two-dimensional electrophoresis and identified by MALDI-TOF-MS. Here we show that the stem cell line DO64 and the deduced cell clones can clearly be distinguished by differences in the expression of a number of raft-associated proteins, namely caveolin-1, flotillin- 1, vimentin, galectin-3, and glyceraldehyde-3-phosphate dehydrogenase. All identified proteins play an important role in cellular functions and may therefore participate in raft-mediated leukemic transformation. Therefore, our study suggests that the analysis of lipid raft protein composition may be useful for the identification of molecular markers of the transformation process.

Endogenous Galectin-3 Is Localized in Membrane Lipid Rafts and Regulates Migration of Dendritic Cells

“…Galectin-3 has been shown to be present in lipid rafts in HeLa cells (Foster et al , 2003) and transformed canine hematopoietic stem cells (Osterhues et al , 2006), although the possibility that galectin-3 is associated with glycoprotein ligands present in raft isolates was not addressed in these studies. Another member of this family, galectin-4, has been identified in highly detergent-resistant superrafts of intestinal microvilli and proposed to function by stabilizing raft assemblies through high-affinity interaction with sulfated raft lipids (Hansen et al , 2001; Ideo et al , 2005).…”

Restoration of caveolin‐1 expression suppresses growth, membrane‐type‐4 metalloproteinase expression and metastasis‐associated activities in colon cancer cells

“…Isolation of lipid rafts was performed as previously described with slight changes. Cells lysates were adjusted to 40% sucrose and layered on the bottom of an ultracentrifuge tube.…”

Galectins in epithelial functions

“…Galectin-3 promotes the raft-dependent endocytosis of integrins and also localizes to clathrin-independent carriers (CLICs) possibly playing a role in raft-dependent endocytosis 69 , 70 . Galectin-3 has also been reported to be endocytosed in recycling endosomes, and associated binding to caveolin-1 and flotillin-1 has been documented 71 . In non-polarized breast cancer cells, Galectin-3 is endocytosed via a caveolae-like, raft-dependent pathway 69 .…”