PHENOTYPIC CHANGES IN LIPOPOLYSACCHARIDE-TREATED CLONED CELLS DERIVEDFROM TRANSPLANTABLE RAT MALIGNANT FIBROUS HISTIOCYTOMA

To investigate a possible phenotypic modulation, MT-8L and MT-9L cells were induced by in vitro culture of undifferentiated MT-8 and fibrohi stiocytic MT-9 cells, which had been established from a rat malignant fibrous histiocytoma (MFH), in the medium containing 10 mu g lipopolys accharide: (LPS)/m/. MT-8L and MT-9L gave greater positive reactions f or histiocytic lysosomal markers and showed ultrastructures of histioc ytic natures. In MT-8L, alpha-smooth muscle actin-positive myofibrobla stic cells also significantly increased in number. MT-8L expressed bot h histiocytic and myofibroblastic phenotypes. MT-8L-induced tumors con sisted mainly of storiform type MFH, differing from undifferentiated s arcoma type induced by MT-8. MT-9L and MT-9 tumors showed a storiform pattern. A phenotypic modulation of MFH cells was easily induced by LP S treatment.