Bone marrow pre-B expansion by SL/Kh-Bomb1 locus: Not sufficient for lymphomagenesis

The pre-B lymphoma in SL/Kh mice is a polygenic trait involving a number of host genes. In prelymphoma-stage bone marrow, transient pre-B cell expansion is induced by a host locus, Bomb1, and later followed by the emergence of a monoclonal population with a similar phenotype. To determine whether these pre-B cells represent precursors of lymphomas, we generated a congenic strain, NFS.SL/Kh-Bomb1 mice, by marker-assisted backcrossing to NFS. The congenic mice showed pre-B cell expansion, but pre-B lymphomas were not observed, even after 1 year of observation, irrespective of murine leukemia virus inoculation. Disturbed early B cell differentiation per se is not sufficient for SL/Kh lymphomagenesis.