Nucleolin expressed at the cell surface is a marker of endothelial cells in angiogenic blood vessels

Abstract

A tumor-homing peptide, F3, selectively binds to endothelial cells in tumor blood vessels and to tumor cells. Here, we show that the cell surface molecule recognized by F3 is nucleolin. Nucleolin specifically bound to an F3 peptide affinity matrix from extracts of cultured breast carcinoma cells. Antibodies and cell surface biotin labeling revealed nucleolin at the surface of actively growing cells, and these cells bound and internalized fluorescein-conjugated F3 peptide, transporting it into the nucleus. In contrast, nucleolin was exclusively nuclear in serum-starved cells, and F3 did not bind to these cells. The binding and subsequent internalization of F3 were blocked by an antinucleolin antibody. Like the F3 peptide, intravenously injected antinucleolin antibodies selectively accumulated in tumor vessels and in angiogenic vessels of implanted “matrigel” plugs. These results show that cell surface nucleolin is a specific marker of angiogenic endothelial cells within the vasculature. It may be a useful target molecule for diagnostic tests and drug delivery applications.

ADAMTS-2 functions as anti-angiogenic and anti-tumoral molecule independently of its catalytic activity

“…Nucleolin was initially described as a nucleolar protein participating in the transcriptional control of ribosomal RNA genes, in ribosomes maturation and assembly, and in the nucleocytoplasmic transport of ribosomal components [40,41]. It has also been shown that nucleolin can translocate to the plasma membrane in some specific cell types such as endothelial cells and many transformed cells [42]. When present at the cell surface, it has been shown that nucleolin can interact with Erb B receptors or serves as a receptor for L-selectin, midkine and, most interestingly, endostatin [43], a potent antiangiogenic fragment of collagen XVIII.…”

Unraveling the mysteries of endostatin

“…Nucleolin has critical and fundamental effects on cell proliferation including organization of nucleolar chromatin, packaging of pre-RNA, rDNA transcription, and ribosome assembly (84)(85)(86). Interestingly, in angiogenic conditions, nucleolin can be mobilized from nucleus to cell surface of endothelium, which is considered as a marker for angiogenic vasculature (87,88). Compared with other reported receptors, cell surface nucleolin has a tissue specific distribution and is only expressed on angiogenic blood vessels but not mature ones.…”

RNA-binding protein nucleolin in disease

“…Nucleolin is modified by ADP-ribosylation, 117 but the some tumor cells. 91 Although these ligands can impair nucleolin binding to target mRNAs, it is not yet known if their antitumor actions are explained by nucleolin's altered RNA-binding activity.…”

“…[88][89][90] Nucleolin was found to be the receptor of endostatin and peptides F3 and N6L. [91][92][93] Besides tumorigenesis, angiogenesis and signaling pathways, cell-surface nucleolin also participates in viral and bacterial infection. For example, HIV inhibitors such as pleiotrophin (PTN), the pseudopeptide HB-19, and the cytokine midkine bind specifically to cell surface-expressed nucleolin and inhibit HIV entry, indicating that nucleolin facilitates viral entry to the host cell.…”