Osteopontin increases CD44 expression and cell adhesion in RAW 264.7 murine leukemia cells

• Published in: Immunology letters Vol. 95; no. 1; pp. 109 - 112
• Main Authors: Marroquin, Carlos E., Downey, Laura, Guo, Hongtao, Kuo, Paul C.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-08-2004
• Subjects: Animals; Anisomycin - pharmacology; Cell Adhesion; Cell Line, Tumor; Extracellular matrix; Hyaluronan Receptors - genetics; Hyaluronan Receptors - metabolism; Hyaluronate; Leukemia - genetics; Leukemia - metabolism; Leukemia - pathology; Metastasis; Mice; Neoplasms, Experimental - genetics; Neoplasms, Experimental - metabolism; Neoplasms, Experimental - pathology; Oligopeptides - pharmacology; Osteopontin; RNA, Messenger - metabolism; Sialoglycoproteins - metabolism; Sialoglycoproteins - pharmacology; Hyaluronate; Extracellular matrix; Metastasis
• ISSN: 0165-2478; 1879-0542
• DOI: 10.1016/j.imlet.2004.06.001

Background: Osteopontin (OPN) is an inducible cell attachment protein which binds α
vβ
3-integrin and CD44 receptors to promote tumor metastasis. We hypothesized that OPN alters expression of its CD44 receptor to promote neoplastic cell migration.
Methods: RAW264.7 cells were stimulated with OPN (0–10
nM) for 0–12
hours to determine the time- and concentration-dependence of CD44 protein and mRNA expression. In selected instances, a competitive ligand for the α
vβ
3-integrin, GRGDSP (50
nM), or an inhibitor of protein synthesis, anisomycin (10
μg/ml), was added. Cell adhesion to hyaluronan was assayed with the crystal violet assay.
Results: OPN upregulates plasma membrane total CD44 protein in a concentration-(ANOVA
P0.001) and time-dependent (ANOVA
P0.001) fashion. CD44v6 is not altered. Cell adhesion to hyaluronate increases in parallel with CD44 expression. Steady state mRNA levels for CD44 are not altered by OPN. 5
nM OPN increases CD44 protein half-life from 105 ± 11
minutes to 278 ± 15
minutes. (
P<0.03) Blockade of either α
vβ
3-integrin ablates the OPN-dependent increase in CD44.
Conclusions: These data indicate that OPN increases plasma membrane CD44 expression and cell adhesion by binding to its α
vβ
3-integrin receptor. We conclude that OPN may promote tumor metastatic behavior by CD44 expression.