ALBERT

Description: We have recently demonstrated the presence of Kaposi's sarcoma–associated herpesvirus (KSHV) in cultured bone marrow (BM) stromal dendritic cells from all patients with myeloma studied. To show that these findings were not an artifact of tissue culture, we performed in situ hybridization (ISH) and polymerase chain reaction (PCR) to detect KSHV in BM core biopsies. Using ISH to open reading frame-72 (ORF 72), we localized KSHV to BM dendritic cells in 17 of 20 patients with myeloma, 2 patients with plasmacytosis associated with the acquired immunodeficiency syndrome, and 1 case of aplastic anemia. In contrast, BM from normal subjects (n = 4) and patients with lymphoma and leukemia (n = 21) did not contain KSHV. PCR amplification with KSHV primers demonstrated product in fresh BM biopsy samples from 6 of 7 myeloma patients, whereas three normal marrows contained no amplified product. These findings suggest that KSHV, possibly through alterations in the BM microenvironment and production of viral interleukin-6 (vIL-6), may stimulate and maintain abnormal plasma cell proliferation in myeloma and related disorders.

Description: Abstract 2968 Poster Board II-944 Previously, we identified and validated PIM1 as a differentially expressed gene in mantle cell lymphoma (MCL) patient samples. Further, we have shown PIM1 to be a significant prognostic biomarker in MCL. PIM1 is a serine/threonine kinase that is transcriptionally regulated by cytokines, mitogens, and numerous growth factors. PIM1 cooperates with other oncogenes in tumorigenesis and has been implicated in the development of leukemias, lymphomas, late progression events, and most recently in prostate cancer. PIM1 is overexpressed in aggressive lymphomas, such as the blastoid variant of MCL, and the ABC-subtype of diffuse large B-cell lymphomas (DLBCL). Here, we tested the in vivo cooperation of PIM1 with TCL1 in murine lymphomagenesis by producing double transgenic murine strains. PIM1 transgenic mice overexpress murine PIM1 under the control of the immunoglobulin enhancer Eμ. TCL1 transgenic mice (pEμ-B29-TCL1) fail to down-regulate TCL1 expression in mature B and T cells and provide a unique model for mature B-cell malignancies. We hypothesized that PIM1 would either accelerate TCL1-driven lymphomagenesis, result in the development of immature lymphomas, or both. Lymphoid malignancies were examined by immunohistochemistry and classified by a hematopathologist according to “Mouse Models of Human Blood Cancers” (Li et al., 2008). A Kaplan-Meier plot demonstrated statistically significant acceleration of lymphomagenesis in the PIM1/TCL1 transgenic mice when compared with the single transgenic strains. The median lymphoma-free survival for TCL1 single transgenic mice, PIM1 single transgenic mice, or PIM1/TCL double transgenic mice were 10.0 months, 16.0 months, and 8.5 months, respectively. The results were statistically significant: TCL1 vs. PIM1/TCL1 (p=0.0008), PIM1 vs. PIM1/TCL1 (p12 months of age) B-cell lymphomas. The most common lymphomas in PIM1 single transgenic were low-grade B-cell lymphomas [12 of 31 (38.7%)], mainly follicular lymphomas. A minority of PIM1 single transgenic mice developed aggressive lymphomas [6 of 31 (19.4%)], including DLBCL and Burkitt's lymphoma. In contrast, the majority of TCL1 transgenic mice developed aggressive B-cell lymphomas [21 of 36 (58.3%)], mainly DLBCL, lymphohistiocytic subtype. The majority of PIM1/TCL1 double transgenic mice also developed aggressive B-cell lymphomas [20 of 34 (58.8%)], mainly DLBCL, lymphohistiocytic subtype. The low-grade lymphomas that developed in PIM1/TCL1 mice included 5 cases of lymphoplasmacytic lymphoma (LPL); one of these cases had transformed in addition to a DLBCL. Further, endogenous expression of PIM kinase family members was investigated in a human lymphoma cell line bank (n=40) by quantitative real-time PCR. PIM1, PIM2, and PIM3 were found to be overexpressed in cell lines derived from human lymphoid malignancies of multiple histologies. In summary, aberrant PIM1 overexpression in TCL1 transgenic mice accelerated the development of mature, aggressive B-cell lymphomas. The classification of lymphomas in PIM1/TCL1 mice revealed similar histologies as in TCL1 single transgenic mice, mainly DLBCL. Single transgenic PIM1 mice developed low-grade B-cell lymphomas after prolonged observation time. The expression of all 3 PIM kinase family members in human lymphomas implies that pan-PIM kinase inhibitors should be developed as a potential mechanism of drug resistance to more restricted PIM inhibitors could be compensatory overexpression of the non-targeted Pim family members. A clinical trial with a pan-PIM inhibitor is currently ongoing. Disclosures: No relevant conflicts of interest to declare.

Description: We have recently demonstrated the presence of Kaposi's sarcoma–associated herpesvirus (KSHV) in cultured bone marrow (BM) stromal dendritic cells from all patients with myeloma studied. To show that these findings were not an artifact of tissue culture, we performed in situ hybridization (ISH) and polymerase chain reaction (PCR) to detect KSHV in BM core biopsies. Using ISH to open reading frame-72 (ORF 72), we localized KSHV to BM dendritic cells in 17 of 20 patients with myeloma, 2 patients with plasmacytosis associated with the acquired immunodeficiency syndrome, and 1 case of aplastic anemia. In contrast, BM from normal subjects (n = 4) and patients with lymphoma and leukemia (n = 21) did not contain KSHV. PCR amplification with KSHV primers demonstrated product in fresh BM biopsy samples from 6 of 7 myeloma patients, whereas three normal marrows contained no amplified product. These findings suggest that KSHV, possibly through alterations in the BM microenvironment and production of viral interleukin-6 (vIL-6), may stimulate and maintain abnormal plasma cell proliferation in myeloma and related disorders.

Description: Previously, we identified and validated PIM-1 as a differentially expressed gene in mantle cell lymphoma (MCL) patient samples. Further, we have shown PIM-1 to be a significant prognostic biomarker in MCL. PIM-1 is an oncogenic serine/threonine kinase that is transcriptionally regulated by cytokines, mitogens, and numerous growth factors. It cooperates with other oncogenes in tumorigenesis and has been implicated in the development of leukemias, lymphomas, late progression events, and most recently in prostate cancer. PIM-1 is overexpressed in aggressive lymphomas, such as the blastoid variant of MCL, and the ABC-type of DLBCL. Here we tested the in vivo cooperation of PIM-1 with TCL1 in murine lymphomagenesis by producing double transgenic murine strains. PIM-1 transgenic mice overexpress murine PIM-1 under the control of the immunoglobulin enhancer Eμ. TCL1 transgenic mice (pEμ -B29-TCL1) fail to downregulate TCL1 expression in mature B and T cells and provide a unique model for mature B-cell malignancies, including Burkitt-like lymphoma (BLL), DLBCL, marginal zone lymphoma, and B-cell chronic lymphocytic leukemia. We hypothesized that PIM-1 would either accelerate TCL1-driven lymphomagenesis, result in the development of immature lymphomas, or both. Lymphoid malignancies were examined by immunohistochemistry and flow cytometry and classified according to the mouse models of human cancer consortium (MMHCC) ‘Bethesda’ classification scheme. Forty double transgenic mice (PIM-1/TCL1) have been generated and observed for a median follow-up of 9 months. To date, 8/40 (20 %) of the PIM-1/TCL1 mice developed lymphomas, in contrast to 9/88 (10%) PIM-1 and 11/49 (22%) TCL1 transgenic mice, with a median follow-up of 7 and 15 months, respectively. A Kaplan-Meyer plot demonstrated statistically significant acceleration of lymphomagenesis in the PIM-1/TCL1 transgenic mice when compared with single TCL1 transgenic mice (p=0.037). PIM-1 transgenic mice developed early (〈 7 months of age) T-cell lymphoblastic lymphomas and late (〉 20 months of age) DLBCL. TCL1 transgenic mice developed DLBCL, with single occurrences of lymphoblastic, lymphocytic and Burkitt lymphomas. PIM-1/TCL1 transgenic mice developed DLBCL, frequently with extranodal involvement (spleen, liver and lung). A single case of follicular lymphoma was seen. In addition, endogenous expression of PIM kinase family members was investigated in a human lymphoma cell line bank (n=40) by quantitative real-time PCR. PIM-1, PIM-2, and also PIM-3 were found to be overexpressed in cell lines derived from human lymphoid malignancies of multiple histologies. In summary, aberrant PIM-1 overexpression in TCL1 transgenic mice accelerated the development of mature B-cell lymphomas. To date, the classification of lymphomas in PIM-1/TCL1 mice revealed similar histologies as in TCL1 single transgenic mice, mainly DLBCL. The expression of all 3 PIM kinase family members in lymphomas implies that pan-PIM kinase inhibitors should be developed as a potential mechanism of resistance to more restricted PIM inhibitors could be compensatory overexpression of the non-targeted family members.