T-CELL LYMPHOMAS IN V-MYB TRANSGENIC MICE

v-Myb, the transforming protein of avian myeloblastosis virus, causes acute myeloid leukemia in chickens. Similarly, truncation and rearrang ement of the c-myb proto-oncogene to yield a v-Myb-like protein leads to myeloid and B cell lymphomas in chickens and mice, and may be a fac tor in a number of human cancers. To study the effects of deregulation of v-Myb on T cell development, we have generated lines of transgenic mice in which the v-Myb oncoprotein is expressed in a T-cell-specific fashion. Analysis of T cell development in the v-Myb transgenic mice shows that ectopic expression of v-Myb affects the ratio of helper to cytotoxic T cells, by increasing the number of CD4(+) helper cells, an d inhibits thymic involution, such that mature animals have elevated n umbers of thymocytes and circulating mature T cells. In a significant proportion of older animals, high grade T cell lymphomas develop, demo nstrating that v-Myb is oncogenic in T cells.