Apoptosis and proliferative activity of non-Hodgkin's lymphomas: comparison with expression of bcl-2, p53 and c-myc proteins

Effects of targeting sumoylation processes during latent and induced Epstein-Barr virus infections using the small molecule inhibitor ML-792

As the second leading cause of death in the United States, cancer has a considerable impact on society, and one cellular process that is commonly dysregulated in many cancers is the post-translational modification of proteins by the Small Ubiquitin-like Modifier (SUMO; sumoylation). We documented that sumoylation processes are up-regulated in lymphoma tissues in the presence of Latent Membrane Protein-1 (LMP1), the principal oncoprotein of Epstein-Barr virus (EBV). LMP1-mediated dysregulation of cellular sumoylation processes contributes to oncogenesis, modulates innate immune responses, and aids the maintenance of viral latency. Manipulation of protein sumoylation has been proposed for anti-cancer and anti-viral therapies; however, known inhibitors of sumoylation do not only target sumoylation processes. Recently, a specific and selective small-molecule inhibitor of sumoylation (ML-792) was identified; however, nothing is known about the effect of ML-792 on LMP1-mediated dysregulation of cellular sumoylation or the EBV life-cycle. We hypothesized that ML-792 modulates viral replication and the oncogenic potential of EBV LMP1 by inhibiting protein sumoylation. Results showed that ML-792 inhibited sumoylation processes in multiple EBV-positive B cell lines and EBV-positive nasopharyngeal carcinoma cell lines but not in their EBV-negative counterparts. Focusing on its effect on B cells, ML-792 inhibited B-cell growth and promoted cell death at very low doses. ML-792 also modulated LMP1-induced cell migration and cell adhesion, which suggests the abrogation of the oncogenic potential of LMP1. Finally, while higher concentrations of ML-792 were sufficient to induce low levels EBV spontaneous reactivation, they decreased the production of new infectious virus following an induced reactivation and the infection of new cells, suggesting that ML-792 has anti-viral potential. Together, these findings suggest that ML-792 may be a potential therapeutic drug to treat EBV-associated lymphoid malignancies by targeting oncogenesis and the EBV life-cycle.

TAF Family Proteins and MEF2C Are Essential for Epstein-Barr Virus Super-Enhancer Activity

Super-enhancers (SEs) are clusters of enhancers marked by extraordinarily high and broad chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) signals for H3K27ac or other transcription factors (TFs). SEs play pivotal roles in development and oncogenesis. Epstein-Barr virus (EBV) super-enhancers (ESEs) are co-occupied by all essential EBV oncogenes and EBV-activated NF-κB subunits. Perturbation of ESEs stops lymphoblastoid cell line (LCL) growth. To further characterize ESEs and identify proteins critical for ESE function, MYC ESEs were cloned upstream of a green fluorescent protein (GFP) reporter. Reporters driven by MYC ESEs 525 kb and 428 kb upstream of MYC (525ESE and 428ESE) had very high activities in LCLs but not in EBV-negative BJAB cells. EBNA2 activated MYC ESE-driven luciferase reporters. CRISPRi targeting 525ESE significantly decreased MYC expression. Genome-wide CRISPR screens identified factors essential for ESE activity. TBP-associated factor (TAF) family proteins, including TAF8, TAF11, and TAF3, were essential for the activity of the integrated 525ESE-driven reporter in LCLs. TAF8 and TAF11 knockout significantly decreased 525ESE activity and MYC transcription. MEF2C was also identified to be essential for 525ESE activity. Depletion of MEF2C decreased 525ESE reporter activity, MYC expression, and LCL growth. MEF2C cDNA resistant to CRIPSR cutting rescued MEF2C knockout and restored 525ESE reporter activity and MYC expression. MEF2C depletion decreased IRF4, EBNA2, and SPI1 binding to 525ESE in LCLs. MEF2C depletion also affected the expression of other ESE target genes, including the ETS1 and BCL2 genes. These data indicated that in addition to EBNA2, TAF family members and MEF2C are essential for ESE activity, MYC expression, and LCL growth.IMPORTANCE SEs play critical roles in cancer development. Since SEs assemble much bigger protein complexes on enhancers than typical enhancers (TEs), they are more sensitive than TEs to perturbations. Understanding the protein composition of SEs that are linked to key oncogenes may identify novel therapeutic targets. A genome-wide CRISPR screen specifically identified proteins essential for MYC ESE activity but not simian virus 40 (SV40) enhancer. These proteins not only were essential for the reporter activity but also were also important for MYC expression and LCL growth. Targeting these proteins may lead to new therapies for EBV-associated cancers.

The BCL-2 protein in precursor B acute lymphoblastic leukemia in children

The BCL-2 protein plays an important role in controlling apoptosis. Disorders of this process can lead to the emergence and development of acute lymphoblastic leukemia (ALL) and can determine the resistance of leukemic cells to chemotherapy. The levels of BCL-2 mRNA were determined in 20 children with pre-B ALL using RT-polymerase chain reaction and the percentage of BCL-2+ cells in 51 patients using flow cytofluorometry. Similar levels of BCL-2 mRNA (P=0.18) with a higher percentage of cells BCL-2+ (P=0.04) were shown in the bone marrow of patients with pre-B ALL compared to normal peripheral blood mononuclear cells. We could not find any connection between the level of BCL-2 mRNA or the percentage of BCL-2+ cells and selected clinical features. A high percentage of BCL-2+ cells and high levels of BCL-2 mRNA did not affect the 5-year overall survival probability nor the 5-year relapse-free survival probability. These results may indicate a high activity of mechanisms promoting the development of the final form of the BCL-2 protein from mRNA in leukemic cells. A high BCL-2 level does not affect the clinical course or worsen the prognosis in children with ALL.

c-Myc and Rel/NF-kappaB are the two master transcriptional systems activated in the latency III program of Epstein-Barr virus-immortalized B cells

The Epstein-Barr virus (EBV) latency III program imposed by EBNA2 and LMP1 is directly responsible for immortalization of B cells in vitro and is thought to mediate most immunodeficiency-related posttransplant lymphoproliferative diseases in vivo. To answer the question whether and how this proliferation program is related to c-Myc, we have established the transcriptome of both c-Myc and EBV latency III proliferation programs using a Lymphochip specialized microarray. In addition to EBV-positive latency I Burkitt lymphoma lines and lymphoblastoid cell lines (LCLs), we used an LCL expressing an estrogen-regulatable EBNA2 fusion protein (EREB2-5) and derivative B-cell lines expressing a constitutively active or tetracycline-regulatable c-myc gene. A total of 897 genes were found to be fourfold or more up- or downregulated in either one or both proliferation programs compared to the expression profile of resting EREB2-5 cells. A total of 661 (74%) of these were regulated similarly in both programs. Numerous repressed genes were known targets of STAT1, and most induced genes were known to be upregulated by c-Myc and to be involved in cell proliferation. In keeping with the gene expression patterns, inactivation of c-Myc by a chemical inhibitor or by conditional expression of dominant-negative c-Myc and Max mutants led to proliferation arrest of LCLs. Most genes differently regulated in both proliferation programs corresponded to genes induced by NF-kappaB in LCLs, and many of them coded for immunoregulatory and/or antiapoptotic molecules. Thus, c-Myc and NF-kappaB are the two main transcription factors responsible for the phenotype, growth pattern, and biological properties of cells driven into proliferation by EBV.

Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry

Acquired chromosomal anomalies (most commonly translocations) in lymphoma and leukemia usually result in either activation of a quiescent gene (by means of immunoglobulin or T-cell-receptor promotors) and expression of an intact protein product, or creation of a fusion gene encoding a chimeric protein. This review summarizes current immunocytochemical studies of these 2 categories of oncogenic protein, with emphasis on the clinical relevance of their detection in diagnostic samples. Among the quiescent genes activated by rearrangement, expression of cyclin D1 (due to rearrangement of the CCND1 [BCL-1] gene) is a near-specific marker of t(11;14) in mantle cell lymphoma; BCL-2 expression distinguishes follicular lymphoma cells from their nonneoplastic counterparts in reactive germinal centers and appears to be an independent prognostic marker in diffuse large cell lymphoma; and TAL-1 (SCL) expression identifies T-cell acute lymphoblastic neoplasms in which this gene is activated. The protein products of other genes activated by chromosomal rearrangement have a role as markers of either lineage (eg, PAX-5 [B-cell-specific activator protein] for B cells, including B-lymphoblastic neoplasms), or maturation stage (eg, BCL-6 for germinal-center and activated B cells and MUM-1/IRF4 for plasma cells). Currently, no hybrid protein encoded by fusion genes is reliably detectable by antibodies recognizing unique junctional epitopes (ie, epitopes absent from the wild-type constituent proteins). Nevertheless, staining for promyelocytic leukemia (PML) protein will detect acute PML with t(15;17) because the microspeckled nuclear labeling pattern for PML-RARalpha is highly distinctive. Similarly, antibodies to the anaplastic lymphoma kinase (ALK) tyrosine kinase are valuable (because wild-type ALK is not found in normal lymphoid tissue) in detecting neoplasms (CD30-positive large T-cell lymphomas) with t(2;5) or its variants. Thus, immunocytochemical detection of the products of many rearranged genes in lymphoma and leukemia can be clinically informative and provide information on cellular and subcellular protein expression that cannot be inferred from studies based on messenger RNA.

SIV-associated lymphomas in rhesus monkeys (Macaca mulatta) in comparison with HIV-associated lymphomas

A retrospective study was performed to characterize malignant lymphomas of 16 Simian immunodeficiency virus (SIV)-infected rhesus monkeys (Macaca mulatta), 2-9 years of age, on the basis of clinical data, histologic and immunophenotypic results, and cell death indices compiled with the TdT-mediated X-duTP nick end labeling method. We particularly focused on providing immunohistochemical evidence of expression products of EBNA2, Bc12, c-Myc, P21, P53, and Bc16. Results were compared with data from the literature on human HIV-associated lymphomas. According to the updated Kiel classification, the lymphomas were classified as 11 centroblastic lymphomas, three immunoblastic lymphomas, one Burkitt-like lymphoma, and one immunocytoma. Using antibodies to CD20, the B-cell origin of tumor cells was demonstrated. SIV antigen was not demonstrated in the tumor cells. Infection with rhesus lymphocryptovirus was present in 94% of the monkeys. Lymphomas revealed expression of Bc12 in 15/16 (94%), c-Myc in 14/16 (88%), P21 in 10/ 16 (63%), P53 in 12/16 (75%), and Bc16 in 1/16 (6%) monkeys. This study provided evidence that the expression of these gene products, which are thought to play an important role in cell proliferation and apoptosis in HIV- and non-HIV-associated lymphomas, are also involved in the pathogenesis of lymphomas in SIV-infected rhesus monkeys. A tentative relationship between the described gene products and the cell death indices was established for the expression of Bc12. The present primate model represents a suitable animal model for studying the pathogenesis of AIDS-associated lymphomas.

Survivin expression in tumor cell nuclei is predictive of a favorable prognosis in gastric cancer patients

One hundred and thirty three gastric cancer cases were investigated immunohistochemically to clarify the biological role of survivin in gastric cancer cells using a commercially available anti-survivin antibody (SURV11A). Five gastric cancer cell lines were employed to assess localization of survivin by reverse-transcription-polymerase chain reaction (RT-PCR) Southern blotting, Western blotting and immunofluorescence, signals being found in both nucleus and cytoplasm. Survivin nuclear staining of gastric cancer cells was evident in 109 of 133 cases (82.0%) and associated with a favorable prognosis, being an independent prognosticator on multivariate analysis. Survivin nuclear positivity also correlated with younger age and lower incidence of vessel cancer invasion. In contrast, survivin cytoplasmic positivity was noted in 117 cases (88.0%) and did not correlate with any factor of progression or prognosis. The results indicate that survivin is present in the majority of gastric cancer cells but a nuclear localization may play an important physiological role in hindering tumor progression.

Negative regulation of bcl-2 expression by p53 in hematopoietic cells

The p53 protein activates promoters containing p53 binding sites, and it represses other promoters. We examined the effect of p53 on bcl-2 expression in both the DHL-4 B cell line and the K562 erythroleukemia line. Transient transfection analyses revealed that wild-type p53 repressed the bcl-2 full-length promoter. The region of the bcl-2 promoter that was responsive to p53 was mapped to the bcl-2 P2 minimal promoter region, and we showed that p53 and the TATA binding protein bound to the bcl-2 TATA sequence. The TATA binding protein, p53, histone deacetylase-1 and mSin3a could be co-immunoprecipitated from K562 cell nuclear extract. The TATA binding protein and mSin3a could be recovered in a complex at the bcl-2 promoter TATA sequence, however, the formation of this complex was not dependent on the presence of p53. Treatment of K562 cells with the histone deacetylase inhibitor, trichostatin A, resulted in an increase in bcl-2 promoter activity whether p53 was present or not. Therefore, we demonstrated that p53 and the histone deacetylases repress the bcl-2 promoter independently. Similar results were obtained when endogenous bcl-2 mRNA or protein levels were measured in response to either p53 or trichostatin A, and p53 expression resulted in enhanced apoptosis. RNase protection assays demonstrated that transcription from the endogenous 3' bcl-2 promoter was decreased by p53. The regions of p53 that were required for repression of the bcl-2 promoter were defined. We conclude that the TATA sequence in the bcl-2 P2 minimal promoter is the target for repression by p53, and that the interaction between p53 and TBP is most likely responsible for the repression. Mutation of p53 may play a role in the up-regulation of bcl-2 expression in some B cell lymphomas.

Digital ulcers and necroses: novel manifestations of angiocentric lymphoma

We describe a patient with angiocentric lymphoma whose presenting features were multiple areas of digital ulceration and necrosis, including deep ulcers on both great toes. He lacked the lateral halves of both earlobes because of multiple ulcers. Skin biopsy revealed a patchy and diffuse infiltrate of lymphoid cells with nuclear atypia in the dermis and subcutaneous tissue. Angiocentric and angiodestructive features of the lymphoid cells, a prominent histiocytic infiltrate and some epithelioid cell granulomas were found. The results of immunohistochemical staining showed a T-cell phenotype, and showed positive staining for apoptosis. He died in July 1999. Peripheral vascular disturbances including Raynaud's phenomenon, digital skin ulcers and necroses are novel clinical symptoms in patients with angiocentric lymphoma, which should be added to the differential diagnosis in patients with peripheral vascular disturbances.

Cell dynamics and expression of tumor necrosis factor (TNF)-alpha, interleukin-6, and TNF receptors in angioimmunoblastic lymphadenopathy-type T cell lymphoma

Angioimmunoblastic lymphadenopathy (AILD)-type T cell lymphoma is histologically characterized by a mixed infiltrate of atypical T cells and B cells including B immunoblasts and plasma cells as well as eosinophils accompanied by proliferation of high endothelial venules. These morphological peculiarities are widely believed to reflect an abnormal pattern of cytokine expression. To clarify the cell dynamics and cytokine expression pattern in the lymph nodes of AILD-type T cell lymphoma, the frequency of proliferating/apoptotic cells and localization of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 producing cells were determined. Double staining was performed for (1) cell markers and Ki-67 antigen, (2) cell markers and the terminal deoxytransferase-mediated dUTP nick end labeling (TUNEL) method, or (3) cell markers and cytokines. The proliferating cell ratio in atypical T cells of AILD-type T cell lymphoma determined by Ki-67 labeling was 20.2+/-5.0%, while other peripheral T cell lymphomas (PTL) exhibited a ratio of 32.9+/-2.5%. TUNEL-positive apoptotic cells were 0.8+/-0.1% of total cells in AILD-type T cell lymphoma. They were dominantly atypical cells with positive T cell markers. In contrast, lymphoma cells in other types of PTL or paracortical cells in reactive follicular hyperplasia had only 0.3+/-0.1 or 0.4+/-0.1% TUNEL-positive cells, respectively. Thus, lymphoma cells in AILD-type T cell lymphoma demonstrated suppressed proliferating activity and enhanced apoptosis when compared to other types of PTL. TNF-alpha-producing cells were observed in all of the lymph nodes from AILD-type T cell lymphoma cases (15/15) and positive staining was obtained in the majority of atypical T cells and scattered macrophages. In contrast, IL-6 was localized to clusters of atypical T cells in some of the cases (9/15). Further, the expression of TNF-alpha, IL-6, and TNF receptors I and II (TNFRI and TNFRII) was examined by RT-PCR. The TNF-alpha message (2/2) and IL-6 message (2/2) was present in the lymph nodes of AILD-type T cell lymphoma by examination using RT-PCR, while both messages were negative in control cases (0/7). As far as an expression of mRNA for TNF receptors in AILD-type T cell lymphoma cases, mRNA for TNFRI was definitely expressed in both of the cases (2/2) while TNFRII mRNA was weakly expressed in one case (1/2). Overexpression of TNF-alpha as well as TNFRI may play a role in controlling T cell proliferation through an autocrine (T cell-T cell interaction) and paracrine (macrophage-T cell interaction) fashion. IL-6, which was also expressed by part of lymphoma cells of AILD-type T cell lymphoma, facilitates the proliferation of B cells, plasma cells, and T cells or endothelial cells in the lymph nodes of AILD-type T cell lymphoma.

Prognostic significance of Ki-67, p53, and Bcl-2 expression in prostate cancer patients with lymph node metastases: a retrospective immunohistochemical analysis

The prognostic significance of Ki-67, p53, and Bcl-2 expression was evaluated in prostate cancer patients with lymph node metastases. Immunohistochemical staining of archived material obtained from 56 patients was performed by the streptavidin-biotin method. Univariate survival analysis showed that a Ki-67 labeling index (Ki-67 LI) of > or = 8.4 in the primary tumor identified a group of patients with a significantly poorer prognosis (P < 0.001). furthermore, a Ki-67 LI of > or = 8.7 in the nodal metastatic tumor was also associated with a poorer prognosis (P < 0.01). Multivariate analysis showed that the Ki-67 LI of primary tumors (P < 0.01) and lymph node metastases (P < 0.01) had independent prognostic value. p53 and Bcl-2 expression had no prognostic value in patients with prostate cancer and lymph node involvement. The Ki-67 LI has more prognostic value than p53 and Bcl-2 expression for patients with prostate cancer that has spread to the lymph nodes.

Apoptosis, proliferative activity and Bcl-2 expression in Epstein-Barr-virus-positive non-Hodgkin's lymphomas

In order to clarify the effects of Epstein-Barr virus (EBV) infection on apoptosis and proliferative activity of non-Hodgkin's lymphoma, 135 Japanese lymphoma cases were investigated for the presence of viral RNA and its correlation with bcl-2 protein (Bcl-2) expression. In addition, the role of EBV in lymphoma-genesis was also studied in terms of EBV genotyping and specific deletion in the gene for the latent membrane protein 1 (LMP-1). EBER-1 RNA in situ hybridization revealed EBV in 18 cases (13.3%), comprising 12 of 44 T cell (27.3%) and 6 of 91 B cell (6.6%) lymphomas. Type A EBV was found in all 18 cases (100%), and 17 of the 17 (100%) evaluable cases showed a 30-bp deletion within the 3' end of LMP-1. Comparison of apoptotic indices (AI), assessed by DNA nick-end labelling, and proliferative activity, estimated in terms of Ki-67 labelling and mitotic indices (KI and MI), demonstrated an overall correlation among AI, KI and MI increases in association with Bcl-2 negativity, indicating a close relation between apoptosis and proliferation. EBV-positive cases showed significantly elevated AI values, independent of Bcl-2 positivity, with no change in KI and MI. These results indicate that EBV in Japanese non-Hodgkin's lymphomas is exclusively of type A with a specific deletion in LMP-1 and that it tends to be present in T cell lymphomas. Moreover, EBV up-regulates apoptosis without any relation to Bcl-2 expression and exerts only minor effects on proliferation.