ABSTRACT
Many investigators have reported the occurrence of hematological disorders affecting the mature cells as well as the committed stem cells in mice transplanted with a variety of tumors. A pluripotent stem cell is characterized by its capacity for self renewal and commitment to different hematopoietic lineages. Another important criterion of a primitive hematopoietic cell is its ability to allow long-term reconstitution of hematopoiesis. Culture systems were devised which allow the in vitro growth of colonies containing cells belonging to two or more lineages. These colonies, called mixed colonies or Colony-forming unit-GEMM, were found initially in the mouse fetal liver and then in adult murine marrow and blood. The EMT6 tumor originated from a mammary carcinoma in a BALB/c mouse which can be maintained in vitro or in vivo as described by Rockwell et al. The release by malignant cells of growth factor involved in normal conditions in the regulation of hematopoiesis should be emphasized.
