Molecular specialization of breast vasculature: A breast-homing phage-displayed peptide binds to aminopeptidase P in breast vasculature

Abstract

In vivo phage display identifies peptides that selectively home to the vasculature of individual organs, tissues, and tumors. Here we report the identification of a cyclic nonapeptide, CPGPE-GAGC, which homes to normal breast tissue with a 100-fold selectivity over nontargeted phage. The homing of the phage is inhibited by its cognate synthetic peptide. Phage localization in tissue sections showed that the breast-homing phage binds to the blood vessels in the breast, but not in other tissues. The phage also bound to the vasculature of hyperplastic and malignant lesions in transgenic breast cancer mice. Expression cloning with a phage-displayed cDNA library yielded a phage that specifically bound to the breast-homing peptide. The cDNA insert was homologous to a fragment of aminopeptidase P. The homing peptide bound aminopeptidase P from malignant breast tissue in affinity chromatography. Antibodies against aminopeptidase P inhibited the in vitro binding of the phage-displayed cDNA to the peptide and the in vivo homing of phage carrying the peptide. These results indicate that aminopeptidase P is the receptor for the breast-homing peptide. This peptide may be useful in designing drugs for the prevention and treatment of breast cancer.endothelial cells ͉ vascular targeting ͉ breast cancer T he vascular beds of individual tissues differ in structure and metabolic function, and in expression of organ-specific adhesion molecules (1). Such specialization is particularly striking in lymphoid tissues where the high endothelia are composed of cells that express unique adhesion molecules for lymphocyte homing (2). Furthermore, metastasis into preferred organs by certain tumors may depend on interactions between tumor cells and organ-specific molecules in the vasculature of the target organ (3).Our laboratory has shown that peptide libraries displayed on phage can be screened in vivo for phage that home to a specific target, and we and others have shown that peptides capable of homing to the vasculature of various individual tissues can be isolated in this manner (4 -6). In vivo selections have also successfully identified peptides that home to tumor vasculature and the vasculature of other pathological lesions (7,8). Some of the tumor-homing peptides recognize known markers of sprouting endothelial cells and angiogenic tumor vasculature, such as the ␣ v ␤ 3 , ␣ v ␤ 5 , and ␣ 5 ␤ 1 integrins (7, 9), matrix metalloproteases (10 -12), and NG2 proteoglycan (13,14). A group of tumor-homing peptides containing the sequence motif NGR were used to identify aminopeptidase N as a new marker of angiogenic vasculature (15). Only one homing peptide receptor in the vasculature of normal tissues has been identified so far; membrane dipeptidase is selectively expressed in lung vasculature and serves as a receptor for a set of lung-homing peptides (16).Homing peptides show promise in the delivery of drugs and other therapies into designated target sites. Thus, peptides identified by phage display have been used to target doxorubicin, proap...

Peptides targeting inflamed synovial vasculature attenuate autoimmune arthritis

“…The CX7C library displayed on the T7Select415-1 phage (Novagen) was prepared as described previously (9,14). This library was subjected to sequential ex vivo and in vivo phage selection.…”

“…The molecular differences in the vascular endothelium of various tissues/organs have been termed as "molecular addresses" or "zip codes" (9)(10)(11). For example, a nonapeptide was found to home to normal breast tissue and to bind to aminopeptidase P in breast vasculature (14). Similarly, peptides homing specifically to brain, kidney, lung, heart, skin, pancreas, retina, and prostate have been identified (9).…”

Leukemia targeting ligands isolated from phage display peptide libraries

“…A number of peptides binding specific cell surface markers were recovered from a variety of tissues in vivo and cell types in vitro. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Peptide ligands selectively binding to certain cell types can be linked to therapeutic compounds to target them to the site of interest. [22][23][24]29,31,32 Thus, the use of phage display may lead to the identification of novel ligands that can be used for targeted therapies even without prior knowledge about the identity of the target receptor.…”

Characterization of a specific phage-displayed peptide binding to vasculature of human gastric cancer

“…Vascular beds in different locations-particularly in tumors-express surface proteins (''vascular zip codes'') and such vascular 'addresses' may provide the means by which systemically administered therapies can be targeted to specific tissues. [2][3][4][5][6][7] In this article, we attempt to obtain some specific "vascular zip codes" for gastric cancer using phage displayed peptide library screening in vivo.…”