Vasostatin, a Calreticulin Fragment, Inhibits Angiogenesis and Suppresses Tumor Growth

Abstract

An endothelial cell inhibitor was purified from supernatant of an Epstein-Barr virus–immortalized cell line and identified as fragments of calreticulin. The purified recombinant NH2-terminal domain of calreticulin (amino acids 1–180) inhibited the proliferation of endothelial cells, but not cells of other lineages, and suppressed angiogenesis in vivo. We have named this NH2-terminal domain of calreticulin vasostatin. When inoculated into athymic mice, vasostatin significantly reduced growth of human Burkitt lymphoma and human colon carcinoma. Compared with other inhibitors of angiogenesis, vasostatin is a small, soluble, and stable molecule that is easy to produce and deliver. As an angiogenesis inhibitor that specifically targets proliferating endothelial cells, vasostatin has a unique potential for cancer treatment.

Characterization of DNA vaccines encoding the domains of calreticulin for their ability to elicit tumor-specific immunity and antiangiogenesis

“…Meanwhile, tumor treatment experiments and examination of microvessel density in nude mice and Matrigel experiments in C57BL/6 mice revealed that NCRT/E7 DNA generated a stronger antiangiogenic effect than CRT/E7 DNA. NCRT, the N-terminal domain of calreticulin, has been demonstrated to inhibit endothelial cell proliferation in response to bFGF or VEGF and angiogenesis in vivo [10,11]. By inhibiting endothelial cell growth, NCRT would likely reduce tumor neovascularization to inhibit tumor growth.…”

“…Previous studies have shown that CRT can be complexed with peptides in vitro to elicit peptide-specific CD8 + T cell responses through exogenous administration [9]. Recently, full-length calreticulin has been reported to be an endothelial cell inhibitor and exerts antitumor effects in vivo via antiangiogenesis [10][11][12]). …”

“…The N domain interacts with the DNA-binding domain of the glucocorticoid receptor in vitro [14], with rubella virus RNA [15], with α-integrin [16], and with protein disulphide-isomerase (PDI) and ER protein 57 (ERp57) [17]. The N domain of calreticulin also inhibits proliferation of endothelial cells and suppresses angiogenesis [10]. The P domain (residues 181-280) is rich in proline and contains two sets of three sequence repeats.…”

A gene therapy for cancer based on the angiogenesis inhibitor, vasostatin

“…6,7,11,12 Vasostatin, the N-terminal domain of calreticulin inclusive of amino acids 1-180, is a potent angiogenesis inhibitor, isolated from culture supernatants of an Epstein-Barr virus-immortalized cell line. [13][14][15] Purified recombinant vasostatin selectively inhibits basic fibroblast growth factor (bFGF)-induced endothelial cell proliferation in vitro and bFGF-induced angiogenesis in vivo. The recombinant vasostatin also prevented or apparently reduced growth of human Burkitt lymphoma and human colon carcinoma in murine model.…”

“…The recombinant vasostatin also prevented or apparently reduced growth of human Burkitt lymphoma and human colon carcinoma in murine model. 13,14 Direct intramuscular injection of plasmid DNA is a relatively safe alternative for gene therapy to viral vectors, 16 although the latter is a potential approach in cancer gene therapy studies. 17 It has been reported that the delivery of heterologous genes into skeletal muscle can provide the sustained production of proteins in the circulation.…”