Transformation of bone marrow cells from E mu-myc transgenic mice by Abelson murine leukemia virus and Harvey murine...

Transgenic mice harboring a c-myc gene subjugated to the immunoglobulin heavy chain enhancer offer a unique opportunity to investigate whether deregulated myc expression potentiates the transformation of B lymphoid cells by other oncogenes. By assessing colony formation in semi-solid medium, we have compared the potential of bone marrow cells from E mu-myc mice and their normal littermates for transformation by Harvey murine sarcoma virus and Abelson murine leukemia virus. E mu-myc bone marrow yielded more lymphoid colonies than normal marrow after infection with Harvey virus. The increased transformation frequency may reflect increased clonogenicity due to complementation between myc and ras and/or the increased number of pre-B cells in E mu-myc marrow. Surprisingly, however, the number of lymphoid colonies induced by Abelson virus was not enhanced. Our interpretation of these results is that the primary Abelson target is more primitive than the pre-B cells expressing the E mu-myc transgene and is therefore not present at increased frequency in the E mu-myc marrow. The cells from most virus-infected E mu-myc colonies failed to grow indefinitely when placed in liquid culture in the absence of a feeder layer. Thus expression of a deregulated c-myc gene together with either v-Ha-ras or v-abl does not ensure fully autonomous growth of early B lymphoid cells.