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 rearrangement 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 factor 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, and inhibits thymic involution, such that mature animals have elevated numbers of thymocytes and circulating mature T cells. In a significant proportion of older animals, high grade T cell lymphomas develop, demonstrating that v-Myb is oncogenic in T cells.