B-cell-specific conditional expression of Myd88p.L252P leads to the development of diffuse large B-cell lymphoma in mice.

The adaptor protein MYD88 is critical for relaying activation of Toll-like receptor signaling to NF-κB activation. MYD88 mutations, particularly the p.L265P mutation, have been described in numerous distinct B-cell malignancies, including diffuse large B-cell lymphoma (DLBCL). Twenty-nine percent of activated B-cell-type DLBCL (ABC-DLBCL), which is characterized by constitutive activation of the NF-κB pathway, carry the p.L265P mutation. In addition, ABC-DLBCL frequently displays focal copy number gains affecting BCL2 Here, we generated a novel mouse model in which Cre-mediated recombination, specifically in B cells, leads to the conditional expression of Myd88(p.L252P) (the orthologous position of the human MYD88(p.L265P) mutation) from the endogenous locus. These mice develop a lymphoproliferative disease and occasional transformation into clonal lymphomas. The clonal disease displays the morphologic and immunophenotypical characteristics of ABC-DLBCL. Lymphomagenesis can be accelerated by crossing in a further novel allele, which mediates conditional overexpression of BCL2 Cross-validation experiments in human DLBCL samples revealed that both MYD88 and CD79B mutations are substantially enriched in ABC-DLBCL compared with germinal center B-cell DLBCL. Furthermore, analyses of human DLBCL genome sequencing data confirmed that BCL2 amplifications frequently co-occurred with MYD88 mutations, further validating our approach. Finally, in silico experiments revealed that MYD88-mutant ABC-DLBCL cells in particular display an actionable addiction to BCL2. Altogether, we generated a novel autochthonous mouse model of ABC-DLBCL that could be used as a preclinical platform for the development and validation of novel therapeutic approaches for the treatment of ABC-DLBCL.

Spontaneous regression of a metastatic carcinoma transmitted by a kidney graft.

Transmission of a malignancy from a donor's organ to the recipient of the graft is a rare event, though it is a severe complication that can result in a poor outcome. Usually, immunosuppressive therapy is discontinued and the allograft is removed. However, treatment of patients with the disseminated cancers implies that after the graft removal and cessation of the immunosuppression, radiotherapy, chemotherapy, or immunotherapy with alpha-interferon (INF-α) or interleukin-2 (IL-2) are required. The case report presents a clinical case of a transmitted kidney graft with multiple metastases (MTS) in a 31-year-old woman with the spontaneous regression of the metastatic cancer after transplantectomy and cancellation of the immunosuppressive therapy. Obviously, the determining factor is the recognition of the tumor by the effectors of the antitumor immunity due to the human leukocyte antigen (HLA) mismatch between the donor and the recipient. Therefore, cancellation of the immunosuppressive therapy in cases of transferal of a malignancy with a transplanted organ allows the effectors of the immune system to distinguish the tumor as a foreign tissue and effectively eliminate this neoplasm.