Surfactant as a release agent opposing the adhesion of tumor cells in determining malignancy

It is well established that adhesion of metastatic cells to the endothelium of the host organ is of major importance in initiating their arrest prior to invasion. However, wherever there is the potential for adhesion and subsequent disruption of normal physiological function in several other situations in vivo unrelated to cancer, the body provides a release agent in the form of surface-active phospholipids. It is proposed here that these surfactants also oppose the inherent adhesiveness of circulating tumour cells, arrest depending upon the relative potencies of glue and anti-glue. Thus, malignancy is determined not just by the "stickiness" of the metastatic emboli but by a general deficiency of surfactant or one of the host in failing to provide an adequately adsorbed layer of this release agent repelling adhesion and overall "rooting" of the seed cells. Moreover, a difference in surface activity of the release agent(s) at different sites can provide an explanation for any differential affinity observed when comparing the detachment of a cell from a primary tumour with its attachment to the host or any difference in metastatic potential of the same cells in different organs.