Mast cells and tumor angiogenesis.

Tumor angiogenesis factor (TAF) elicits a strong vasoproliferative response when implanted upon the chorioallantoic membrane (CAM) of the chick embryo. This response is first observed stereomicroscopically 2-3 days after implantation. A 40-fold increase in mast cell density is observed within the vicinity of this implant by 24 h. Mast cells that have been isolated from retired breeder Sprague-Dawley rats fail to evoke a vascular reaction when implanted on the CAM. An intermediate role for the mast cell in tumor angiogenesis is suggested.