Effects of Cytochalasin B on Human Malignant

Abstract

Human malignant melanoma cells and human squamous cell carcinoma cells were treated with cytochalasin B (CB) in vitro and observed with light and electron microscopes. When spindle‐shaped melanoma cells were treated with CB, they rounded up and their submembranous microfilaments (mf) (6 nanometers thick) vanished totally. After being released from CB after treatment for 10 days, they became flat and the submembranous mf reappeared to a nearly normal extent. Squamous cell carcinoma cells, when treated with CB, did not round up and the submembranous mf did not disappear. These results suggest that (i) submembranous microfilaments are not essential to make and keep certain types of cells round and (ii) the responses of cells to cytochalasin B are quite different in different cells.