BCL3 and neoplasm: To confirm our observation in LM2 cells, we generatedBcl-3-sufficient and Bcl-3-deficient MMTV-PyMT mice, anaggressive transgenic mouse model of murine mammary adenocarcinomadevelopment (MMTV-polyoma middle T (PyMT) mice).33 We found no gross histopathologic orquantitative differences between the groups based on primary tumordevelopment or tumor burden (Supplementary Figure2a).