Increased actin nucleating activity in tumorigenic cells

The kinetics of actin polymerization has been used to quantitate the relative levels of actin nucleating activity in extracts from a number of related tumorigenic and non-tumorigenic cells. The level of nucleating activity was significantly elevated in the tumorigenic compared with the non-tumorigenic cell extracts whether the results were expressed on the basis of per protein (2-3 fold increase) or per total endogenous cellular actin (3-4 fold increase). It is concluded that this activity is probably due to an actin filament capping/severing regulatory protein(s) and that this protein(s) may be, at least partially, responsible for the microfilament disruption observed in transformed cells.