Mice bearing the E mu-myc and E mu-pim-1 transgenes develop pre-B-cell leukemia prenatally.

Previously, it has been shown that E mu-pim-1 transgenic mice are predisposed to T-cell lymphomas, whereas E mu-myc transgenic mice are predisposed to pre-B-cell lymphomas. Here we show that double-transgenic E mu-myc E mu-pim-1 mice exhibit pre-B-cell leukemia in utero. Upon transplantation into recipient mice, embryo-derived double-transgenic leukemic cells frequently progressed to highly malignant monoclonal tumors, indicating that additional (epi)genetic events had occurred during the progression of the disease.