Germ Line Insertions of Moloney Murine Leukemia Virus in the TLL Mouse Causes Site-specific Differences in Lymphoma/Leukemia Frequency and Tumor Immunophenotype

Abstract

Background: Moloney murine leukemia virus (Mo-MLV) has proven valuable for studies of the pathogenesis of malignant lymphoma. Inoculation of newborn mice induces T cell lymphoma with 100% incidence. The TLL (T cell lymphoma/leukemia)-strain was previously established and was shown to spontaneously develop T cell lymphoma at high frequency. Materials and Methods: Differential screening of cDNA libraries was performed to discover an involvement of Mo-MLV and genomic sequencing was used to identify the chromosomal position of Mo-MLV proviral integration sites. Immunophenotypes of the tumors were established by flow cytometry. Disease frequency curves were created according to the Kaplan-Meier method. Results: Two independent Mo-MLV germ line integrations were characterized on chromosomes 2 and 14, giving rise to two substrains of mice denoted TLL-2 and TLL-14. The chromosomal position of the integrated provirus affected the frequency of disease, as well as the immunophenotype of the tumors. Conclusion: The data suggest that factors influencing the transcriptional activity of the chromosomal regions, leading to differences in proviral expression, could underlie the observed difference in tumor frequency.