Characteristics of cloned cells of mixed müllerian tumor of the human uterus carcinoma cells showing myogenic differentiation in vitro

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Abstract
Background. To elucidate the relationship between the epithelial and mesenchymal elements of malignant mixed Müllerian tumors (MMMT), the authors examined the biologic properties of two clones of different cell types (designated as FU‐MMT‐2‐C1 and FU‐MMT‐2‐S1) established from a uterine MMMT cell line (FU‐MMT‐2), which they previously have reported. Methods and Results. By morphologic and immuno‐cytochemical analyses, FU‐MMT‐2‐C1 exhibited features of adenocarcinoma cells, whereas FU‐MMT‐2‐S1 showed characteristics of sarcoma cells with myogenic differentiation. Some FU‐MMT‐2‐C1 cells at confluence differentiated spontaneously into myogenic mesenchymal cells in vitro. In addition, transitional‐type cells between epithelial cells and sarcomatous cells were observed in the areas of mesenchymal differentiation in FU‐MMT‐2‐C1 by light and electron microscopic study. Ultrastructurally, the transitional‐type cells represented biphasic morphologic characteristics consisting of epithelial and myogenic features, which proved to coexpress epithelial, mesenchymal, and muscle markers by double immunoenzymatic staining. However, no epithelial differentiations were apparent in the sarcoma clone FU‐MMT‐2‐S1. FU‐MMT‐2‐C1 produced tumor in nude mice, the histologic study of which showed a mixture of adenocarcinoma and myogenic sarcomatous elements that resembled the original tumor. Cytogenetic studies demonstrated that these two clones were monoclonal in origin because of the presence of common karyotypic abnormalities in both cells. In addition, the amplified (approximately fourfold to eightfold) c‐myc oncogene was found in the cloned cells and the original tumor cells. Conclusions. The current results strongly support the theory of single cell origin in uterine MMMT and suggest that the mesenchymal elements originated from primitive Müllerian epithelial cells capable of differentiating into epithelial, mesenchymal, or both elements.