Molecular and cytological features of the mouse B-cell lymphoma line iMyc(Eμ)-1

BACKGROUND: Myc-induced lymphoblastic B-cell lymphoma (LBL) in iMyc(Eμ )mice may provide a model system for the study of the mechanism by which human MYC facilitates the initiation and progression of B cell and plasma cell neoplasms in human beings. We have recently shown that gene-targeted iMyc(Eμ )mice that carry a His(6)-tagged mouse Myc cDNA, Myc(His), just 5' of the immunoglobulin heavy-chain enhancer, Eμ, are prone to B cell and plasma cell tumors. The predominant tumor (~50%) that arose in the iMyc(Eμ )mice on the mixed genetic background of segregating C57BL/6 and 129/SvJ alleles was LBL. The purpose of this study was to establish and characterize a cell line, designated iMyc(Eμ)-1, for the in-depth evaluation of LBL in vitro. METHODS: The morphological features and the surface marker expression profile of the iMyc(Eμ)-1 cells were evaluated using cytological methods and FACS, respectively. The cytogenetic make-up of the iMyc(Eμ)-1 cells was assessed by spectral karyotyping (SKY). The expression of the inserted Myc(His )gene was determined using RT-PCR and qPCR. Clonotypic immunoglobulin gene arrangements were detected by Southern blotting. The global gene expression program of the iMyc(Eμ)-1 cells and the expression of 768 "pathway" genes were determined with the help of the Mouse Lymphochip(© )and Superarray(© )cDNA micro- and macroarrays, respectively. Array results were verified, in part, by RT-PCR and qPCR. RESULTS: Consistent with their derivation from LBL, the iMyc(Eμ)-1 cells were found to be neoplastic IgM(high)IgD(low )lymphoblasts that expressed typical B-cell surface markers including CD40, CD54 (ICAM-1), CD80 (B7-1) and CD86 (B7-2). The iMyc(Eμ)-1 cells harbored a reciprocal T(9;11) and three non-reciprocal chromosomal translocations, over-expressed Myc(His )at the expense of normal Myc, and exhibited gene expression changes on Mouse Lymphochip(© )microarrays that were consistent with Myc(His)-driven B-cell neoplasia. Upon comparison to normal B cells using eight different Superarray(© )cDNA macroarrays, the iMyc(Eμ)-1 cells showed the highest number of changes on the NFκB array. CONCLUSION: The iMyc(Eμ)-1 cells may provide a uniquely useful model system to study the growth and survival requirements of Myc-driven mouse LBL in vitro.