Fibrinogen E fragment selectively disrupts the vasculature and inhibits the growth of tumours in a syngeneic murine model

Abstract

We recently demonstrated that a fragment of human fibrinogen, fibrinogen E fragment, inhibits the migration and differentiation of human endothelial cells in vitro. Here we show that it exerts similar effects on murine endothelial cells in vitro, and selectively disrupts tumour endothelium in vivo, causing widespread intravascular thrombosis and retarding the growth of CT26 tumours in a syngeneic murine model.

A Multiphase Model Describing Vascular Tumour Growth

“…Further, tumours implanted beneath the skin of mice remain approximately spherical during growth, in a manner reminiscent of multicell spheroids cultured in vitro. These tumours develop a central necrotic core, surrounded by a region of proliferating cells in which the volume fraction of blood vessels appears to be approximately constant (Brown et al, 2002). The rate at which a tumour's volume increases over time seems to be strongly tumour specific, with growth rates that are linear (for murine tumours (Brown et al, 2002)), quadratic (for a human glioblastoma multiform (Kozin et al, 2001) and for tumours derived from Neuro2a cells (Todo et al, 2001), implanted into the flank of mice), or cubic (for tumours derived from murine lewis lung carcinoma cells (Liao et al, 2000) and for tumours derived from murine breast carcinoma cells (Candido et al, 2001), implanted into the flank of mice) reported in the literature.…”

A novel fragment derived from the β chain of human fibrinogen, β43–63, is a potent inhibitor of activated endothelial cells in vitro and in vivo

“…It inhibits the migration and differentiation of human ECs in response to VEGF, EGF and FGF2 in vitro (Bootle-Wilbraham et al, 2000) and is cytotoxic for activated ECs in vitro. These effects may explain why FgnE selectively disrupts tumour endothelium, causing widespread intravascular thrombosis and tumour necrosis in vivo (Brown et al, 2002). We also showed that alphastatin, a 24-amino-acid peptide fragment derived from the N terminus of the a chain of FgnE, mimics many of the anti-angiogenic effects of FgnE in vitro as well as its anti-vascular effects in vivo.…”

“…Interestingly, in contrast to FgnE and alphastatin that inhibit tumour growth by causing vascular damage and an increase in intravessel thrombosis within the tumours rather than by antiangiogenic mechanisms (Brown et al, 2002;Staton et al, 2004), b43 -63 caused a significant decrease in tumour vascularisation (ie was anti-angiogenic) without any evidence of thrombosis. This decrease in vessel counts could account for the increase in tumour necrosis, and decrease in tumour growth and suggests that should the control tumours not have ulcerated and therefore the experiment be continued beyond 10 days treatment, a greater Anti-angiogenic effects of b43 -63effect on tumour growth would have been observed.…”

“…CBA/Gy mice (Gray cancer Institute, Northwood, UK) were anaesthetised by isofluorane inhalation and inoculated subcutaneously with 10 6 viable CaNT tumour cells. Tumour volume was determined at regular intervals by caliper measurement (accurate to 0.1 mm) in two dimensions as described previously (Brown et al, 2002) using the equation: volume ¼ (a 2 Â b)/2, where a is the smaller and b the larger diameter of the two. When tumours had grown to 100-150 mm 3 , mice were injected i.p.…”

“…Formalinfixed sections were stained for H&E and tumour necrosis assessed semi-quantitatively using a Chalkley grid method (% necrosis) (Brown et al, 2002). Zinc-fixed sections were exposed to a rat monoclonal anti-murine CD31 (1 : 100; Pharmingen, San Diego, CA, USA) specific for ECs, for 60 min at room temperature, and immunoreactivity detected using the ABC rat elite kit (Vector Laboratories, UK) and diaminobenzidine.…”