Abstract
Previous studies on the tumourigenic conversion of early passage rat embryo cells by the polyoma virus early genes have suggested a multigenic control of tumourigenesis. Thus, the large T gene can immortalize early passage rat cells and can relieve the serum dependence of normal and transformed cells. The middle T gene alone cannot immortalize early passage cells; however, it can induce cells of established cell lines to become anchorage-independent and tumourigenic. Here we show that when linked to transcriptional enhancers, the polyoma virus middle T gene can trigger the complete malignant transformation of early passage rodent cells. Therefore, the polyoma virus middle T gene does not require a cooperating oncogene to induce malignant conversion of these cells.