Anaplastic plasmacytomas: relationships to normal memory B cells and plasma cell neoplasms of immunodeficient and autoimmune mice.

Anaplastic plasmacytomas (APCTs) from NFS.V(+) congenic mice and pristane-induced plasmacytic PCTs from BALB/c mice were previously shown to be histologically and molecularly distinct subsets of plasma cell neoplasms (PCNs). Here we extended these comparisons, contrasting primary APCTs and PCTs by gene expression profiling in relation to the expression profiles of normal naïve, germinal centre, and memory B cells and plasma cells. We also sequenced immunoglobulin genes from APCT and APCT-derived cell lines and defined surface phenotypes and chromosomal features of the cell lines by flow cytometry and by spectral karyotyping and fluorescence in situ hybridization. The results indicate that APCTs share many features with normal memory cells and the plasma cell-related neoplasms (PLs) of FASL-deficient mice, suggesting that APCTs and PLs are related and that both derive from memory B cells. Published in 2010 by John Wiley & Sons, Ltd.

Irradiated Blm-deficient mice are a highly tumor prone model for analysis of a broad spectrum of hematologic malignancies.

Mutations in the BLM gene cause human Bloom syndrome (BS), an autosomal recessive disorder of growth retardation, immunodeficiency and cancer predisposition. Homozygous null Blm(m3/m3) mice are cancer prone with a 5-fold increased risk of cancer compared with Blm(m3/+) and Blm(+/+) mice. Irradiation of Blm(m3/m3) mice increased the risk to 28-fold. Tumors occurred mainly in the hematopoietic system and were similar to those in BS based on detailed histologic and immunohistochemical analyses. Irradiated Blm-deficient mice thus provide a novel model for understanding accelerated malignancies in BS and a new platform for investigating the molecular basis for a wide range of hematopoietic neoplasms.

Anaplastic, plasmablastic, and plasmacytic plasmacytomas of mice: relationships to human plasma cell neoplasms and late-stage differentiation of normal B cells.

We have compared histologic features and gene expression profiles of newly identified plasmacytomas from NFS.V(+) congenic mice with plasmacytomas of IL6 transgenic, Fasl mutant, and SJL-beta2M(-/-) mice. NFS.V(+) tumors comprised an overlapping morphologic spectrum of high-grade/anaplastic, intermediate-grade/plasmablastic, and low-grade/plasmacytic cases with similarities to subsets of human multiple myeloma and plasmacytoma. Microarray and immunohistochemical analyses of genes expressed by the most prevalent tumors, plasmablastic plasmacytomas, showed them to be most closely related to immunoblastic lymphomas, less so to plasmacytomas of Fasl mutant and SJL mice, and least to plasmacytic plasmacytomas of IL6 transgenic mice. Plasmablastic tumors seemed to develop in an inflammatory environment associated with gene signatures of T cells, natural killer cells, and macrophages not seen with plasmacytic plasmacytomas. Plasmablastic plasmacytomas from NFS.V(+) and SJL-beta2M(-/-) mice did not have structural alterations in Myc or T(12;15) translocations and did not express Myc at high levels, regular features of transgenic and pristane-induced plasmacytomas. These findings imply that, as for human multiple myeloma, Myc-independent routes of transformation contribute to the pathogenesis of these tumors. These findings suggest that plasma cell neoplasms of mice and humans exhibit similar degrees of complexity. Mouse plasmacytomas, previously considered to be homogeneous, may thus be as diverse as their human counterparts with respect to oncogenic mechanisms of plasma cell transformation. Selecting specific types of mouse plasmacytomas that relate most closely to subtypes of human multiple myeloma may provide new opportunities for preclinical testing of drugs for treatment of the human disease.

Expression of the cyclin-dependent kinase inhibitor p27 and its deregulation in mouse B cell lymphomas.

CDKN1B (p27) regulates cell-cycle progression at the G1-S transition by suppressing the cyclin E/CDK2 kinase complex. In normal lymphocytes and most human B cell non-Hodgkin lymphomas (NHL), there is an inverse correlation between proliferative activity and expression of p27; however, a subset of NHL with high mitotic indices expresses p27, which is inactive due to sequestration in nuclear protein complexes or due to cytoplasmic retention. Our studies of mouse B cell NHL also identified cases with high proliferative activity and high levels of p27 at a surprisingly high frequency. Here, p27 was complexed with D-type cyclins 1 and 3 and with the COPS9 protein, JAB1. In addition, we found cytoplasmic sequestration following phosphorylation by activated AKT.

Histologic and molecular characterizations of megakaryocytic leukemia in mice.

Six cases of megakaryocytic leukemia (MKL) were identified and analyzed for morphology and molecular features. MKL were composed of megakaryocyte lineage cells ranging from immature to quite mature cells. VWF, GATA1 and RUNX1 were strongly expressed in megakaryocytes in both normal spleen and MKL as analyzed by immunohistochemistry (IHC). Altered expression of Meis1, Pbx1 and Psen2 and Lef1 in MKL detected with oligonucleotide microarrays was confirmed by qPCR and IHC. This is the first report of spontaneous MKL in mice, defining VWF as a biomarker for diagnosis and suggesting possible involvement of a series of genes in disease pathogenesis.

High-throughput retroviral tagging for identification of genes involved in initiation and progression of mouse splenic marginal zone lymphomas.

Human B-cell lymphomas are frequently associated with specific genetic changes caused by chromosomal translocations that activate proto-oncogenes. For lymphomas of mice expressing murine leukemia virus, mutagenic proviral insertions are thought to play a similar role. Here we report studies designed to determine whether specific retroviral integration sites might be associated with a specific subset of mouse B-cell lymphomas and if the genes associated with these sites are regularly altered in expression. We studied splenic marginal zone lymphomas (MZL) of NFS.V(+) mice that are unusual in exhibiting frequent progression from low to high grade, potentially allowing assignment of cancer genes to processes of initiation and progression. We used inverse PCR to clone and analyze 212 retroviral integration sites from 43 MZL at different stages of progression. Sixty-two marked common integration sites and included 31 that had been marked previously. Among the new common integration sites, seven were unique to MZL. Using microarrays and real-time quantitative PCR analysis, we defined differential patterns of gene expression in association with disease progression for Gfi1, Sox4, Brca2, Snf1lk, Nfkb1, Pou2af1, Prdm1, Stat6, and Blnk. Heightened expression of Gfi1 distinguishes MZL from other lymphoma types. The combined use of proviral tagging and analyses of gene expression thus provides a powerful approach to understanding of genes that collaborate in tumorigenesis.

Bethesda proposals for classification of nonlymphoid hematopoietic neoplasms in mice.

The hematopathology subcommittee of the Mouse Models of Human Cancers Consortium recognized the need for a classification of murine hematopoietic neoplasms that would allow investigators to diagnose lesions as well-defined entities according to accepted criteria. Pathologists and investigators worked cooperatively to develop proposals for the classification of lymphoid and nonlymphoid hematopoietic neoplasms. It is proposed here that nonlymphoid hematopoietic neoplasms of mice be classified in 4 broad categories: nonlymphoid leukemias, nonlymphoid hematopoietic sarcomas, myeloid dysplasias, and myeloid proliferations (nonreactive). Criteria for diagnosis and subclassification of these lesions include peripheral blood findings, cytologic features of hematopoietic tissues, histopathology, immunophenotyping, genetic features, and clinical course. Differences between murine and human lesions are reflected in the terminology and methods used for classification. This classification will be of particular value to investigators seeking to develop, use, and communicate about mouse models of human hematopoietic neoplasms.

Bethesda proposals for classification of lymphoid neoplasms in mice.

A consensus system for classification of mouse lymphoid neoplasms according to their histopathologic and genetic features has been an elusive target for investigators involved in understanding the pathogenesis of spontaneous cancers or modeling human hematopoietic diseases in mice. An international panel of scientists with expertise in mouse and human hematopathology joined with the hematopathology subcommittee of the Mouse Models for Human Cancers Consortium to develop criteria for definition and classification of these diseases together with a standardized nomenclature. The fundamental elements contributing to the scheme are clinical features, morphology, immunophenotype, and genetic characteristics. The resulting classification has numerous parallels to the World Health Organization classification of human lymphoid tumors while recognizing differences that may be species specific. The classification should facilitate communications about mouse models of human lymphoid diseases.