A new parameter for discriminating malignantly transformed cell lines from nontransformed counterparts: culture in liquid medium containing neutral protease.

Growth properties of malignantly transformed cell lines and their nontransformed counterparts were studied in the presence of a bacterial neutral protease (Dispase I). Among 10 transformed cell lines, 7 lines could proliferate in the presence of the protease in a floating state. Nontransformed cell lines and non-established cell strains failed to grow in this culture condition. The ability to grow in the presence of the protease was well correlated with their ability for anchorage-independent growth and tumorigenicity, and this provides a convenient primary test for evaluating cellular tumorigenicity.