The objective of this project is to study the specific tumor cell inhibition of aggregation previously reported. We will study the generality of this effect, especially with regard to human cancer cells, and the mechanism which may account for this inhibition. Specifically we will test a variety of human tumors and normal tissues for the effect of their presence on the aggregation of embryonic cells. We will also utilize a variety of metabolic inhibition and surface active agents to detect subtle changes in both normal and cancer cells which may effect their interactions with other cells. This "sensor" system may have clinical applications as well.