RT Journal Article SR Electronic T1 Plasma Membrane Nucleolin Is a Receptor for the Anticancer Aptamer AS1411 in MV4-11 Leukemia Cells JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 984 OP 991 DO 10.1124/mol.109.055947 VO 76 IS 5 A1 Sridharan Soundararajan A1 Li Wang A1 Vijayalakshmi Sridharan A1 Weiwei Chen A1 Nigel Courtenay-Luck A1 David Jones A1 Eleanor K. Spicer A1 Daniel J. Fernandes YR 2009 UL http://molpharm.aspetjournals.org/content/76/5/984.abstract AB AS1411 is a DNA aptamer that is in phase II clinical trials for relapsed or refractory acute myeloid leukemia and for renal cell carcinoma. AS1411 binds to nucleolin, a protein that is overexpressed in the cytoplasm and on the plasma membrane of some tumor cells compared with normal cells. Studies were performed to determine whether cell surface nucleolin is a receptor for AS1411 in the acute myeloid leukemia cell line MV4-11. Biotinylation of MV4-11 cell surface proteins followed by immunoblotting of the biotinylated proteins showed that full-length (106 kDa) and truncated forms of nucleolin were present on the cell surface. In contrast, K-562 cells, which are 4-fold less sensitive than MV4-11 cells to AS1411, showed no full-length nucleolin and lesser amounts of the truncated forms of nucleolin on the cell surface. Incubation of MV4-11 cells with [32P]AS1411 and immunoprecipitation of the plasma membrane fraction with anti-nucleolin antibody demonstrated the presence of [32P]AS1411-nucleolin complexes. Anti-nucleolin antibody inhibited binding of fluorescein isothiocyanate (FITC)-AS1411 to plasma membrane nucleolin 56 ± 10% SE (P < 0.01) compared with cells incubated with FITC-AS1411 only. Cellular uptake of [32P]AS1411 into MV4-11 cells was blocked by a 20-fold excess of unlabeled AS1411 but not by a 20-fold excess of the biologically inactive oligonucleotide CRO-26. Uptake was approximately 3-fold faster into MV4-11 cells than into K-562 cells. Partial knockdown of plasma membrane and cytosolic nucleolin in MCF-7 cells resulted in a 3-fold decrease in AS1411 uptake. These results provide evidence that plasma membrane nucleolin is a functional receptor for AS1411 in MV4-11 cells. © 2009 The American Society for Pharmacology and Experimental Therapeutics