MYC and/or IL-6 driven mouse models of human Burkitt lymphoma (BL) and multiple myeloma (MM). (A) Overview of transgenic (Tg) mice used in this study. IL6 mice harbor a widely expressed human interleukin-6 transgene designated H2-Ld-hIL6 [40,41]. MYC mice contain a mouse Myc (c-myc) cDNA transgene that has been inserted in the immunoglobulin heavy-chain locus with the help of gene targeting in embryonic stem cells . IL6MYC mice were generated by intercrossing homozygous-Tg MYC mice and heterozygous-Tg IL6 mice, followed by selection of double-Tg offspring. All mice were on the genetic background of BALB/c (C). (B) Photomicrograph of a representative histologic section of the type of myeloma-like plasma cell tumor that arises consistently in both IL6 and IL6MYC mice (H&E, original magnification 40x). Compared to IL6 mice, tumor onset is shorter and tumor incidence is higher in IL6MYC mice. (C) Representative tissue section of the main type of tumors observed in MYC mice: Burkitt-like lymphoblastic B-cell lymphoma that exhibits the typical “starry sky” morphology due to tingible body macrophages that engulf apoptotic tumor cells (H&E, original magnification 40x).