SOX11 is a novel binding partner and endogenous inhibitor of SAMHD1 ara-CTPase activity in mantle cell lymphoma.

ABSTRACT: Sterile alpha motif and histidine-aspartate (HD) domain-containing protein 1 (SAMHD1) is a deoxynucleoside triphosphate triphosphohydrolase with ara-CTPase activity that confers cytarabine (ara-C) resistance in several hematological malignancies. Targeting SAMHD1's ara-CTPase activity has recently been demonstrated to enhance ara-C efficacy in acute myeloid leukemia. Here, we identify the transcription factor SRY-related HMG-box containing protein 11 (SOX11) as a novel direct binding partner and first known endogenous inhibitor of SAMHD1. SOX11 is aberrantly expressed not only in mantle cell lymphoma (MCL), but also in some Burkitt lymphomas. Coimmunoprecipitation of SOX11 followed by mass spectrometry in MCL cell lines identified SAMHD1 as the top SOX11 interaction partner, which was validated by proximity ligation assay. In vitro, SAMHD1 bound to the HMG box of SOX11 with low-micromolar affinity. In situ crosslinking studies further indicated that SOX11-SAMHD1 binding resulted in a reduced tetramerization of SAMHD1. Functionally, expression of SOX11 inhibited SAMHD1 ara-CTPase activity in a dose-dependent manner resulting in ara-C sensitization in cell lines and in a SOX11-inducible mouse model of MCL. In SOX11-negative MCL, SOX11-mediated ara-CTPase inhibition could be mimicked by adding the recently identified SAMHD1 inhibitor hydroxyurea. Taken together, our results identify SOX11 as a novel SAMHD1 interaction partner and its first known endogenous inhibitor with potentially important implications for clinical therapy stratification.

SOX11 is a novel binding partner and endogenous inhibitor of SAMHD1 ara-CTPase activity in mantle cell lymphoma.

The sterile alpha motif and histidine-aspartate (HD) domain containing protein 1 (SAMHD1) is a deoxynucleoside triphosphate triphosphohydrolase with ara-CTPase activity that confers cytarabine (ara-C) resistance in several haematological malignancies. Targeting SAMHD1's ara-CTPase activity has recently been demonstrated to enhance ara-C efficacy in acute myeloid leukemia. Here, we identify the transcription factor SRY-related HMG-box containing protein 11 (SOX11) as a novel direct binding partner and first known endogenous inhibitor of SAMHD1. SOX11 is aberrantly expressed not only in mantle cell lymphoma (MCL), but also in some Burkitt lymphomas. Co-immunoprecipitation of SOX11 followed by mass spectrometry in MCL cell lines identified SAMHD1 as the top SOX11 interaction partner which was validated by proximity ligation assay. In vitro, SAMHD1 bound to the HMG box of SOX11 with low-micromolar affinity. In situ crosslinking studies further indicated that SOX11-SAMHD1 binding resulted in a reduced tetramerization of SAMHD1. Functionally, expression of SOX11 inhibited SAMHD1 ara-CTPase activity in a dose-dependent manner resulting in ara-C sensitization in cell lines and in a SOX11-inducible mouse model of MCL. In SOX11-negative MCL, SOX11-mediated ara-CTPase inhibition could be mimicked by adding the recently identified SAMHD1 inhibitor hydroxyurea. Taken together, our results identify SOX11 as a novel SAMHD1 interaction partner and its first known endogenous inhibitor with potentially important implications for clinical therapy stratification.

Specific properties of shRNA-mediated CCR5 downregulation that enhance the inhibition of HIV-1 infection in combination with shRNA targeting HIV-1 rev.

Treatment with RNAi against HIV-1 transcripts efficiently inhibits viral replication but induces selection of escape mutants; therefore, the CCR5 coreceptor was suggested as an additional target. Blocking viral and host transcripts improved the antiviral effect. We have used short hairpin RNA (shRNA) targeting the human CCR5 (shCCR5) or the HIV-1 rev (shRev) transcripts to demonstrate distinctive properties of anti-CCR5 shRNA: shCCR5 induced more sustained protection than shRev; partial reduction in CCR5 expression substantially decreased HIV-1 infection, and shCCR5 performed better than shRev in the mixed shRNA-treated and untreated cultures. These observations indicate that CCR5 inhibitors should be conveniently included in HIV-1 gene silencing treatment schedules when only a certain cell fraction is protected to further reduce endogenous virus in a properly ART-treated HIV-1 infected individual.

Expression of GNAZ, encoding the Gαz protein, predicts survival in mantle cell lymphoma.

Mantle cell lymphoma (MCL), a malignancy of B-lymphocytes, has a poor prognosis. It is thus necessary to improve the understanding of the pathobiology of MCL and identify factors contributing to its aggressiveness. Our studies, based on Affymetrix data from 17 MCL biopsies, real-time quantitative polymerase chain reaction data from 18 sorted primary MCL cells and 108 MCL biopsies compared to non-malignant tissue, reveals that GNAZ expression predicts poor clinical outcome of MCL patients (Cox regression, P = 0·014) and lymphocytosis (Mann-Whitney, P = 0·011). We show that GNAZ translates to Gαz protein - a signalling molecule within the G-protein coupled receptor network. Our findings suggest that GNAZ/Gαz contribute to the MCL pathobiology.

Susceptibility to infections, without concomitant hyper-IgE, reported in 1976, is caused by hypomorphic mutation in the phosphoglucomutase 3 (PGM3) gene.

Phosphoglucomutase 3 (PGM3) is an enzyme converting N-acetyl-glucosamine-6-phosphate to N-acetyl-glucosamine-1-phosphate, a precursor important for glycosylation. Mutations in the PGM3 gene have recently been identified as the cause of novel primary immunodeficiency with a hyper-IgE like syndrome. Here we report the occurrence of a homozygous mutation in the PGM3 gene in a family with immunodeficient children, described already in 1976. DNA from two of the immunodeficient siblings was sequenced and shown to encode the same homozygous missense mutation, causing a destabilized protein with reduced enzymatic capacity. Affected individuals were highly prone to infections, but lack the developmental defects in the nervous and skeletal systems, reported in other families. Moreover, normal IgE levels were found. Thus, belonging to the expanding group of congenital glycosylation defects, PGM3 deficiency is characterized by immunodeficiency, with or without increased IgE levels, and with variable forms of developmental defects affecting other organ systems.

Prognostic role of SOX11 in a population-based cohort of mantle cell lymphoma.

The prognostic role of the transcription factor SOX11 in mantle cell lymphoma (MCL) is controversial. We investigated prognostic markers in a population-based cohort of 186 MCL cases. Seventeen patients (9%) did not require any therapy within the first 2 years after diagnosis and were retrospectively defined as having an indolent disease. As expected, indolent MCL had less frequent B symptoms and extensive nodal involvement and 88% of these cases expressed SOX11. In our cohort 13 cases (7.5%) lacked nuclear SOX11 at diagnosis. SOX11(-) MCL had a higher frequency of lymphocytosis, elevated level of lactate dehydrogenase (LDH), and p53 positivity. The overall survival in the whole cohort, excluding 37 patients receiving autologous stem cell transplantation, was 3.1 year and in patients with indolent or nonindolent disease, 5.9 and 2.8 years, respectively (P = .004). SOX11(-) cases had a shorter overall survival, compared with SOX11(+) cases, 1.5 and 3.2 years, respectively (P = .014). In multivariate analysis of overall survival, age > 65 (P = .001), Eastern Cooperative Oncology Group score ≥ 2 (P = .022), elevated LDH level (P = .001), and p53 expression (P = .001) remained significant, and SOX11 lost significance. We conclude that most indolent MCLs are SOX11(+) and that SOX11 cannot be used for predicting an indolent disease course.

Bruton's tyrosine kinase (Btk): function, regulation, and transformation with special emphasis on the PH domain.

Bruton's agammaglobulinemia tyrosine kinase (Btk) is a cytoplasmic tyrosine kinase important in B-lymphocyte development, differentiation, and signaling. Btk is a member of the Tec family of kinases. Mutations in the Btk gene lead to X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Activation of Btk triggers a cascade of signaling events that culminates in the generation of calcium mobilization and fluxes, cytoskeletal rearrangements, and transcriptional regulation involving nuclear factor-kappaB (NF-kappaB) and nuclear factor of activated T cells (NFAT). In B cells, NF-kappaB was shown to bind to the Btk promoter and induce transcription, whereas the B-cell receptor-dependent NF-kappaB signaling pathway requires functional Btk. Moreover, Btk activation is tightly regulated by a plethora of other signaling proteins including protein kinase C (PKC), Sab/SH3BP5, and caveolin-1. For example, the prolyl isomerase Pin1 negatively regulates Btk by decreasing tyrosine phosphorylation and steady state levels of Btk. It is intriguing that PKC and Pin1, both of which are negative regulators, bind to the pleckstrin homology domain of Btk. To this end, we describe here novel mutations in the pleckstrin homology domain investigated for their transforming capacity. In particular, we show that the mutant D43R behaves similar to E41K, already known to possess such activity.

The role of cannabinoid receptors and the endocannabinoid system in mantle cell lymphoma and other non-Hodgkin lymphomas.

The initiating oncogenic event in mantle cell lymphoma (MCL) is the translocation of cyclin D1, t(11;14)(q13;q32). However, other genetic aberrations are necessary for an overt lymphoma to arise. Like other B cell lymphomas, MCL at some points during the oncogenesis is dependent on interactions with other cells and factors in the microenvironment. The G protein coupled receptors cannabinoid receptors 1 and 2 (CB1 and CB2) are expressed at low levels on non-malignant lymphocytes and at higher levels in MCL and other lymphoma subtypes. In this review we give an overview of what is known on the role of the cannabinoid receptors and their ligands in lymphoma as compared to non-malignant T and B lymphocytes. In MCL cannabinoids mainly reduce cell proliferation and induce cell death. Importantly, our recent findings demonstrate that cannabinoids may induce either apoptosis or another type of programmed cell death, cytoplasmic vacuolation/paraptosis in MCL. The signalling to death has been partly characterized. Even though cannabinoid receptors seem to be expressed in many other types of B cell lymphoma, the functional role of cannabinoid receptor targeting is yet largely unknown. In non-malignant B and T lymphocytes, cannabinoid receptors are up-regulated in response to antigen receptor signalling or CD40. For T lymphocytes IL-4 has also a crucial role in transcriptional regulation of CB1. In lymphocytes, cannabinoid act in several ways - by affecting cell migration, cytokine response, at high doses inhibit cell proliferation and inducing cell death. The possible role for the endocannabinoid system in the immune microenvironment of lymphoma is discussed.

2-Arachidonoylglycerol Modulates CXCL12-Mediated Chemotaxis in Mantle Cell Lymphoma and Chronic Lymphocytic Leukemia.

To survive chemotherapy, lymphoma cells can relocate to protective niches where they receive support from the non-malignant cells. The biolipid 2-arachidonoylglycerol (2-AG), an agonist for the cannabinoid receptors CB1 and CB2, is released by stromal cells in the bone marrow. To investigate the role of 2-AG in lymphoma, we analyzed the chemotactic response of primary B-cell lymphoma cells enriched from peripheral blood of twenty-two chronic lymphocytic leukemia (CLL) and five mantle cell lymphoma (MCL) patients towards 2-AG alone and/or to the chemokine CXCL12. The expression of cannabinoid receptors was quantified using qPCR and the protein levels visualized by immunofluorescence and Western blot. Surface expression of CXCR4, the main cognate receptor to CXCL12, was analyzed by flow cytometry. Phosphorylation of key downstream signaling pathways activated by 2-AG and CXCL12 were measured by Western blot in three MCL cell lines and two primary CLL samples. We report that 2-AG induces chemotaxis in 80% of the primary samples, as well as 2/3 MCL cell lines. 2-AG induced in a dose-dependent manner, the migration of JeKo-1 cell line via CB1 and CB2. 2-AG affected the CXCL12-mediated chemotaxis without impacting the expression or internalization of CXCR4. We further show that 2-AG modulated p38 and p44/42 MAPK activation. Our results suggest that 2-AG has a previously unrecognized role in the mobilization of lymphoma cells by effecting the CXCL12-induced migration and the CXCR4 signaling pathways, however, with different effects in MCL compared to CLL.

Clinical significance of the WHO grades of follicular lymphoma in a population-based cohort of 505 patients with long follow-up times.

The prognostic value of grading follicular lymphoma has been debated since the 1980s. There is consensus that World Health Organization (WHO) grades 1 and 2 are indolent, but not whether grades 3A or 3B are aggressive. We retrospectively reviewed the follicular lymphoma diagnoses according to the 2008 WHO classification in all diagnostic specimens from a population-based cohort of 505 patients with a median follow-up time of 10·0years (range, 4·6-16·0). After excluding 43 patients with concomitant diffuse large B-cell lymphoma, 345 remained with grade 1-2, 94 with grade 3A, and 23 with grade 3B follicular lymphoma. Grades 1-2 and 3A seemed equally indolent, with indistinguishable clinical courses, even in patients receiving anthracyclines. Compared with grades 1-3A and independently of clinical factors, grade 3B correlated with higher mortality (P=0·008), but outcome was improved after upfront anthracycline-containing therapy (P=0·015). In contrast to grade 1-3A patients, grade 3B patients experienced no relapses or deaths beyond 5years of follow-up. Furthermore, patients with grade 3B were predominantly male and seldom presented with bone-marrow involvement. We conclude that follicular lymphoma grade 1-3A is indolent and incurable with conventional therapy. Grade 3B appears to be an aggressive but curable disease.

Clinical effects of a single dose of cannabinoids to patients with chronic lymphocytic leukemia.

This phase II clinical trial investigates a one-time oromucosal dose of tetrahydrocannabinol/cannabidiol (THC/CBD) in 23 patients with indolent leukemic B cell lymphomas. Primary endpoint was a significant reduction in leukemic B cells. Grade 1 - 2 adverse events were seen in 91% of the patients; most common were dry mouth (78%), vertigo (70%), and somnolence (43%). After THC/CBD a significant reduction in leukemic B cells (median, 11%) occurred within two hours (p = .014), and remained for 6 h without induction of apoptosis or proliferation. Normal B cells and T cells were also reduced. CXCR4 expression increased on leukemic cells and T cells. All effects were gone by 24 h. Our results show that a single dose of THC/CBD affects a wide variety of leukocytes and only transiently reduce malignant cells in blood. Based on this study, THC/CBD shows no therapeutic potential for indolent B cell lymphomas (EudraCT trial no. 2014-005553-39).

Clinical and biological impact of SAMHD1 expression in mantle cell lymphoma.

SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase (dNTPase) that restricts viral replication in infected cells and limits the sensitivity to cytarabine by hydrolysing its active metabolite, as recently shown in acute myeloid leukemia. Cytarabine is an essential component in the Nordic mantle cell lymphoma protocols (MCL2 and MCL3) for induction and high-dose chemotherapy treatment before autologous stem cell transplantation for younger patients with mantle cell lymphoma (MCL). We here investigated the expression of SAMHD1 in a population-based cohort of MCL (N = 150). SAMHD1 was highly variably expressed in MCL (range, 0.4% to 100% of positive tumor cells). Cases with blastoid/pleomorphic morphology had higher SAMHD1 expression (P = 0.028) and SAMHD1 was also correlated to tumor cell proliferation (P = 0.016). SAMHD1 expression showed moderate correlation to the expression of the transcriptional regulator SOX11 (P = 0.036) but genetic silencing of SOX11 and SAMHD1 by siRNA in MCL cell lines did not suggest mutual regulation. We hypothesized that expression of SAMHD1 could predict short time to progression in patients treated with Cytarabine as part of high-dose chemotherapy. Despite the correlation with known biological adverse prognostic factors, neither low or high SAMHD1 expression correlated to PFS or OS in patients treated according to the Nordic MCL2 or MCL3 protocols (N = 158).

High expression of 5-lipoxygenase in normal and malignant mantle zone B lymphocytes.

BACKGROUND: Human B lymphocytes can produce leukotriene B4 but the biological function of the 5-lipoxygenase (5-LO) pathway in B cells is unclear. In order to better understand and define the role of 5-LO in B cells, we investigated the expression of 5-LO mRNA and protein in subsets of B cells from human tonsils and different types of B cell lymphoma. RESULTS: Based on RT-PCR and western blot/immunohistochemical staining, with a polyclonal antibody raised against 5-LO, high expression of 5-LO was found in mantle zone B cells from tonsils. By contrast, only a weak expression of 5-LO was detected in germinal centre cells and no expression in plasma cells from tonsils. This pattern of 5-LO expression was preserved in malignant lymphoma with high expression in mantle B cell lymphoma (MCL) and weak or no expression in follicular lymphoma. Primary leukemized MCL, so called B-prolymphocytic leukaemia cells, and MCL cell lines also expressed 5-LO and readily produced LTB4 after activation. CONCLUSION: The present report demonstrates the expression of 5-LO mainly in normal and malignant mantle zone B cells while the expression is low or absent in germinal centre B cells and plasma cells, indicating a role of the 5-LO pathway in B cells before the cells finally differentiate to plasma cells.

Expression of cannabinoid receptors type 1 and type 2 in non-Hodgkin lymphoma: growth inhibition by receptor activation.

Endogenous and synthetic cannabinoids exert antiproliferative and proapoptotic effects in various types of cancer and in mantle cell lymphoma (MCL). In this study, we evaluated the expression of cannabinoid receptors type 1 and type 2 (CB1 and CB2) in non-Hodgkin lymphomas of B cell type (n = 62). A majority of the lymphomas expressed higher mRNA levels of CB1 and/or CB2 as compared to reactive lymphoid tissue. With the exception of MCL, which uniformly overexpresses both CB1 and CB2, the levels of cannabinoid receptors within other lymphoma entities were highly variable, ranging from 0.1 to 224 times the expression in reactive lymph nodes. Low levels of the splice variant CB1a, previously shown to have a different affinity for cannabinoids than CB1, were detected in 44% of the lymphomas, while CB1b expression was not detected. In functional studies using MCL, Burkitt lymphoma (BL), chronic lymphatic leukemia (CLL) and plasma cell leukemia cell lines, the stable anandamide analog R(+)-methanandamide (R(+)-MA) induced cell death only in MCL and CLL cells, which overexpressed both cannabinoid receptors, but not in BL. In vivo treatment with R(+)-MA caused a significant reduction of tumor size and mitotic index in mice xenografted with human MCL. Together, our results suggest that therapies using cannabinoid receptor ligands will have efficiency in reducing tumor burden in malignant lymphoma overexpressing CB1 and CB2.

The subcellular Sox11 distribution pattern identifies subsets of mantle cell lymphoma: correlation to overall survival.

Gene expression analysis demonstrated high expression of the neuronal transcription factor SOX11 in mantle cell lymphoma (MCL). In contrast to follicular lymphoma, small lymphocytic lymphoma and reactive lymphoid tissue, most MCLs tested (48/53 patients) expressed sox11 protein in the nucleus. Therefore nuclear sox11 expression represents a new tumour marker for a subset of MCL. However, 5/53 MCL cases expressed sox11 only in the cytoplasm; these MCL patients had a shorter survival compared to MCL with nuclear sox11 expression. These results suggest sox11 expression as a new diagnostic marker in MCL that could be related to the clinical and biological behaviour of MCL.

A subset of CD5- diffuse large B-cell lymphomas expresses nuclear cyclin D1 with aberrations at the CCND1 locus.

In 231 diffuse large B-cell lymphomas, the expression of cyclin D1 and CD5 was evaluated. All cases were CD5-. Ten (4.3%) were positive for cyclin D1 and were subjected to fluorescence in situ hybridization at the CCND1 locus. One case showed the t(11;14). In another case, the telomeric probe signal for cyclin D1 was lost in most tumor cells, and in a small proportion of the cells, there were fluorescence signals indicative of the t(11;14). Two other cases displayed additional cyclin D1 signals in the absence of the t(11;14). All cases but 1 were positive for bcl-6 or MUM1, disfavoring the possibility of misdiagnosed blastoid variants of CD5- mantle cell lymphomas. Thus, contrary to the current view, there seems to exist a certain number of cyclin D1+ and CD5- diffuse large B-cell lymphomas, some of which have structural aberrations at the CCND1 locus, including the t(11;14).

CD8+ T-cell content in diagnostic lymph nodes measured by flow cytometry is a predictor of survival in follicular lymphoma.

PURPOSE: Follicular lymphoma is a heterogeneous disease with variable prognosis and clinical course. We hypothesized that the presence of nonmalignant T cells in the microenvironment of the tumor may affect the outcome. EXPERIMENTAL DESIGN: Using flow cytometry, we evaluated the T-cell subsets in the lymph node microenvironment of follicular lymphoma. All patients in South Stockholm County with indolent follicular lymphoma and with flow cytometry done on a diagnostic lymph node between 1994 and 2004 were included (N = 139). Diagnosis and grade (1, 2, and 3a) were confirmed by re-review. Flow cytometry results were reanalyzed. Lymphocyte subsets, the Follicular Lymphoma International Prognostic Index, grade, and clinical characteristics were evaluated in univariable and multivariable Cox analysis with respect to overall survival (OS) and disease-specific survival (DSS). RESULTS: Higher CD8+ T-cell levels correlated with longer OS and DSS, independently of the Follicular Lymphoma International Prognostic Index (OS, P = 0.017; DSS, P = 0.020) and independently of all other prognostic factors (OS, P = 0.001; DSS, P = 0.004). Median OS was not reached for patients in the upper quarter of CD8+ T-cell levels (>8.6%), 10.4 years for patients in the middle half (4.2-8.6%), and 6.0 years for patients in the lower quarter (<4.2%). Furthermore, patients who had not required treatment within 6 months from diagnosis had more CD8+ T cells (P = 0.011). CONCLUSIONS: Higher levels of CD8+ T cells predict a better prognosis, and these data support an important role for nonmalignant immune cells in the biology of follicular lymphoma. Evaluating the CD8+ T cells by flow cytometry at diagnosis may provide prognostic information.

CGH of microdissected Kaposi's sarcoma lesions reveals recurrent loss of chromosome Y in early and additional chromosomal changes in late tumour stages.

BACKGROUND: It is still unclear if Kaposi's sarcoma (KS) is a monoclonal cell proliferation or a polyclonal, hyperplastic, reactive process. Reports on KS cytogenetics are few and restricted to late stage disease and cell lines. METHOD: We analysed 27 KS, early and late, AIDS related (AKS) and endemic (EKS) by laser microdissection, global DNA amplification and comparative genomic hybridization (CGH). RESULT: Loss of Y chromosome was detected in 20/23 male KS, which was the only recurrent chromosomal aberration in all nine male early (patch) KS. Only one patch EKS showed in addition to the Y loss a loss of Xq. Late (nodular) AKS and EKS showed recurrent copy number changes in chromosomes 16, 17, 21, X and Y, as well as other random changes. The loss of chromosome 16, 17 and Y was confirmed by interphase fluorescence in situ hybridization (FISH) on paraffin sections. EKS showed a higher number of chromosomal abnormalities than AKS, indicating that rapid growth of AKS is less dependent on genetic changes than is EKS, possibly because of the immunosuppressed host environment in AKS. CONCLUSION: Clonal loss of chromosome Y was detected in all early male KS, while additional chromosomal aberrations appeared during development to late KS. This increase in chromosomal abnormalities during tumour growth indicates genetic instability and the selection of survival cell clones establishing late, aggressive sarcoma growth. Our data support the view that KS (in males) develops into a clonal tumour yet initially is a hyperplastic reactive cell proliferation.