Mitochondrial/Cell-Surface Protein p32/gC1qR as a Molecular Target in Tumor Cells and Tumor Stroma

A tumor homing peptide, LyP-1, selectively binds to tumor-associated lymphatic vessels and tumor cells in certain tumors and exhibits an antitumor effect. Here, we show that the protein known as p32 or gC1q receptor is the receptor for LyP-1. Various human tumor cell lines were positive for p32 expr...

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Bibliographic Details
Published in:Cancer research (Chicago, Ill.) Ill.), 2008-09, Vol.68 (17), p.7210-7218
Main Authors: FOGAL, Valentina, LIANGLIN ZHANG, KRAJEWSKI, Stan, RUOSLAHTI, Erkki
Format: Article
Language:English
Subjects:
Antineoplastic agents
Biological and medical sciences
Cell Line, Tumor
Cell Separation
Flow Cytometry
Humans
Medical sciences
Membrane Glycoproteins - metabolism
Pharmacology. Drug treatments
Protein Tyrosine Phosphatase, Non-Receptor Type 22 - metabolism
Receptors, Complement - metabolism
Tumors
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Summary:A tumor homing peptide, LyP-1, selectively binds to tumor-associated lymphatic vessels and tumor cells in certain tumors and exhibits an antitumor effect. Here, we show that the protein known as p32 or gC1q receptor is the receptor for LyP-1. Various human tumor cell lines were positive for p32 expression in culture, and the expression was increased in xenograft tumors grown from the positive cell lines. Fluorescence-activated cell sorting analyses with anti-p32 antibodies showed that p32-positive cell lines expressed p32 at the cell surface. These cells bound and internalized LyP-1 peptide in proportion to the cell-surface expression level, which correlated with malignancy rather than total p32 expression in the cells. Like the LyP-1 peptide, p32 antibodies highlighted hypoxic areas in tumors, where they bound to both tumor cells and cells that expressed macrophage/myeloid cell markers and often seemed to be incorporated into the walls of tumor lymphatics. Significant p32 expression was common in human cancers and the p32 levels were often greatly elevated compared with the corresponding normal tissue. These results establish p32, particularly its cell-surface-expressed form, as a new marker of tumor cells and tumor-associated macrophages/myeloid cells in hypoxic/metabolically deprived areas of tumors. Its unique localization in tumors and its relative tumor specificity may make p32 a useful target in tumor diagnosis and therapy.
ISSN:0008-5472
1538-7445
DOI:10.1158/0008-5472.can-07-6752