Strain Dependency of Cell‐type Specificity and Onset of Lymphoma Development in Eμ‐ myc Transgenic Mice

c‐myc is a nuclear proto‐oncogene that, when activated, induces malignancies in a variety of tissues. Most murine plasmacytomas and human Burkitt's lymphomas have been shown to carry a chromosomal translocation involving c‐myc and immunoglobulin genes. To study genetic or epigenetic factors that affect mye ‐induced lymphoid cell tumors, we previously introduced the Eμ‐ mycΔ A gene lacking its own promoter and first exon into two inbred strains of mice, C57BL/6 and C3H/HeJ. We observed three characteristic features in our transgenic mice. First, T cell lymphoma predominated in the C3H background. Second, both pre‐B and B cell lymphoma developed at equal frequency in C57BL/6 transgenic mice. Third, the average age of onset is earlier than that reported by other investigators. To test whether these characteristics are due either to the lack of the promoter region and first exon of the c‐myc gene in the construct or to the genetic background of the mice, we introduced Eμ‐ myc gene containing the complete c‐myc gene into fertilized eggs of C57BL/6 and C3H/HeJ mice. The cell‐type specificity, differentiation‐stage specificity and the average age at onset of lymphoma development were not affected by the transgene construct.