A gradient-driven mathematical model of antiangiogenesis

In this paper, we present a mathematical model describing the angiogenic re sponse of endothelial cells to a secondary tumour. It has been observed exp erimentally that while the primary tumour remains in situ, any secondary tu mours that may be present elsewhere in the host can go undetected, whereas removal of the primary tumour often leads to the sudden appearance of these hitherto undetected metastases-so-called occult metastases. In this paper, a possible explanation for this suppression of secondary tumours by the pr imary tumour is given in terms of the presumed migratory response of endoth elial cells in the neighbourhood of the secondary tumour. Our model assumes that the endothelial cells respond chemotactically to two opposing chemica l gradients: a gradient of tumour angiogenic factor, set up by the secretio n of angiogenic cytokines from the secondary tumour; and a gradient of angi ostatin, set up in the tissue surrounding any nearby vessels. The angiostat in arrives there through the blood system (circulation), having been origin ally secreted by the primary tumour. This gradient-driven endothelial cell migration therefore provides a possible explanation of how secondary tumour s (occult metastases) can remain undetected in the presence of the primary tumour yet suddenly appear upon surgical removal of the primary tumour. (C) 2000 Elsevier Science Ltd. All rights reserved.