Expression of multiple isozymes of granulocyte, monocyte, and macrophage esterases in polycythemic Friend erythroleukemia cells

We examined the expression of cytochemical markers of myeloid and monocyte-macrophage differentiation in conjunction with ultrastructural studies of different malignant erythroleukemic cells isolated from mice infected with the Friend polycythemic virus complex (FLV-P). The amounts of fluoride-sensitive and resistant nonspecific esterase activity increased with the progression of malignancy. Isoelectric focusing resolved this enzyme activity into 13 isozymes in the most malignant Friend cell type tested. These same isozymes were found in the adherent cell population of normal spleens. Two of these isozymes were shown to have chloroacetate esterase activity characteristic of granulocytes. Despite these myeloid and monocyte characteristics, light and electron microscopy showed no morphological evidence of differentiation in either of these lineages. This study demonstrates that the Friend erythroleukemic cell contains markers of three different hemopoietic cell types. The expression of myeloid, monocytic, and erythroid traits in these erythroleukemic cells can be used to monitor their malignant progression.