Pathology of AIDS-related lymphomas and other AIDS-defining neoplasms

Case Report: Immune Microenvironment and Mutation Features in a Patient With Epstein–Barr Virus Positive Large B-Cell Lymphoma Secondary to Angioimmunoblastic T-Cell Lymphoma

On rare occasions, secondary Epstein–Barr virus (EBV)-associated B-cell lymphoma can develop in patients with angioimmunoblastic T-cell lymphoma (AITL). Here, we describe the tumor microenvironment and mutation features of a patient with EBV + large B-cell lymphoma (LBCL) secondary to AITL. He was admitted to hospital due to a 1-year history of fever and enlarged right inguinal lymph nodes. A biopsy of the right inguinal lymph node demonstrated that numerous diffuse medium-sized atypical lymphocytes proliferated, together with increased extrafollicular follicular dendritic cell meshwork, and the lymphocytes expressed CD3, CD4, BCL6, CD10, PD-1, CXCL13, and Ki-67 (75%). Thus, a diagnosis of AITL was made. However, the disease progressed following treatment by CHOP regimen (cyclophosphamide, adriamycin, vincristine, and prednisone). Biopsy showed that most of the cells were positive for CD20 staining and IgH rearrangement. Analysis of 22 kinds of immune cells showed that the numbers of activated NK cells and activated memory T cells increased, while the T-follicular helper population decreased in the transformed sample. In addition, compared with the primary sample, RHOA (G17V) mutation was not detected, while JAK2 and TRIP12 gene mutations were detected in the transformed sample. Overall, we described the immune microenvironment and mutation features of a patient with EBV + LBCL secondary to AITL. This study will help us to understand the mechanisms by which AITL transforms to B-cell lymphoma.

Role of Autophagy in HIV-1 Matrix Protein p17-Driven Lymphangiogenesis

AIDS-related lymphomas (ARLs) are expected to increase in the future since combined antiretroviral therapy (cART) enhances the life expectancy of HIV-1-infected (HIV⁺) patients but does not affect the occurrence of ARLs to the same extent as that of other tumors. Lymphangiogenesis is essential in supporting growth and metastatic spreading of ARLs. HIV-1 does not infect the neoplastic B cells, but HIV-1 proteins have been hypothesized to play a key role in sustaining a prolymphangiogenic microenvironment in lymphoid organs. The HIV-1 matrix protein p17 is detected in blood and accumulates in the germinal centers of lymph nodes of HIV⁺ patients under successful cART. The viral protein displays potent lymphangiogenic activity in vitro and in vivo This is, at least in part, mediated by the secretion of the lymphangiogenic factor endothelin-1, suggesting that activation of a secretory pathway sustains the lymphangiogenic activity of p17. Here, we show that the p17 lymphangiogenic activity occurs on human lymph node-derived lymphatic endothelial cells (LN-LECs) under stress conditions only and relies entirely on activation of an autophagy-based pathway. In fact, induction of autophagy by p17 promotes lymphangiogenesis, whereas pharmacological and genetic inhibition of autophagy inhibits p17-triggered lymphangiogenesis. Similarly, the vasculogenic activity of p17 was totally inhibited in autophagy-incompetent mice. Our findings reveal a previously unrecognized role of autophagy in lymphangiogenesis and open the way to identify novel treatment strategies aimed at inhibiting aberrant tumor-driven lymphangiogenesis in HIV⁺ patients.IMPORTANCE AIDS-related lymphomas (ARLs) are the most common malignancies in HIV-1-infected (HIV⁺) patients after the introduction of combined antiretroviral therapy (cART). Lymphangiogenesis is of critical importance in sustaining growth and metastasis of ARLs. Indeed, enhanced lymphangiogenesis occurs in the lymph nodes of HIV⁺ patients under successful cART. The HIV-1 matrix protein p17 is detected in blood and accumulates in the lymph node germinal centers even in the absence of virus replication. Several findings suggest a key role for p17 as a microenvironmental factor capable of promoting lymphangiogenesis. Here, we show that p17 promotes lymphangiogenesis of human lymph node-derived lymphatic endothelial cells (LN-LECs). The lymphangiogenic activity of p17 is sustained by an autophagy-based pathway that enables LN-LECs to release prolymphangiogenic factors into the extracellular microenvironment. Our findings indicate that specific targeting of autophagy may provide an important new tool for treating ARLs.

CD4-Positive T-Cell Primary Central Nervous System Lymphoma in an HIV Positive Patient

OBJECTIVES

Primary central nervous system lymphomas (PCNSLs) in patients with human immunodeficiency virus (HIV) are predominantly B-cell lymphomas associated with Epstein-Barr virus (EBV) and rarely CD8-positive T-cell PCNSLs.

METHODS

Patient history, laboratory results, cerebrospinal fluid (CSF), imaging, and brain biopsy specimens were reviewed and tested for T-cell receptor clonality.

RESULTS

A 64-year-old HIV-positive woman sought treatment for lethargy and left-sided weakness. Brain imaging showed regional increased T2 signal with restricted diffusion in cerebral hemispheres. CSF flow cytometry revealed CD4-positive T lymphocytes with loss of CD3, CD5, and CD7. EBV-positive T-cell lymphoma was immunohistochemically confirmed on brain biopsy specimens. Molecular analysis detected clonal T-cell receptor gene rearrangement. The patient received intrathecal methotrexate and whole-brain radiation. She did not respond to treatment and was eventually placed in hospice care.

CONCLUSIONS

To our knowledge, this is the first report of CD4-positive T-cell PCNSL in an HIV-positive patient and will help to raise clinical awareness of this previously unknown entity.

HIV-1 matrix protein p17 promotes lymphangiogenesis and activates the endothelin-1/endothelin B receptor axis

OBJECTIVE

AIDS-related lymphomas are high grade and aggressively metastatic with poor prognosis. Lymphangiogenesis is essential in supporting proliferation and survival of lymphoma, as well as tumor dissemination. Data suggest that aberrant lymphangiogenesis relies on action of HIV-1 proteins rather than on a direct effect of the virus itself. HIV-1 matrix protein p17 was found to accumulate and persist in lymph nodes of patients even under highly active antiretroviral therapy. Because p17 was recently found to exert a potent proangiogenic activity by interacting with chemokine (C-X-C motif) receptors 1 and 2, we tested the prolymphangiogenic activity of the viral protein.

APPROACH AND RESULTS

Human primary lymph node-derived lymphatic endothelial cells were used to perform capillary-like structure formation, wound healing, spheroids, and Western blot assays after stimulation with or without p17. Here, we show that p17 promotes lymphangiogenesis by binding to chemokine (C-X-C motif) receptor-1 and chemokine (C-X-C motif) receptor-2 expressed on lymph node-derived lymphatic endothelial cells and activating the Akt/extracellular signal-regulated kinase signaling pathway. In particular, it was found to induce capillary-like structure formation, sprout formation from spheroids, and increase lymph node-derived lymphatic endothelial cells motility. The p17 lymphangiogenic activity was, in part, sustained by activation of the endothelin-1/endothelin receptor B axis. A Matrigel plug assay showed that p17 was able to promote the outgrowth of lymphatic vessels in vivo, demonstrating that p17 directly regulates lymphatic vessel formation.

CONCLUSIONS

Our results suggest that p17 may generate a prolymphangiogenic microenvironment and plays a role in predisposing the lymph node to lymphoma growth and metastasis. This finding offers new opportunities to identify treatment strategies in combating AIDS-related lymphomas.

The role of macrophages in the development and progression of AIDS-related non-Hodgkin lymphoma

Despite HAART, patients infected with HIV develop NHL at a significantly higher level than the noninfected population. The primary difference between lymphoma in non-HIV-infected individuals and those with ARL is that ARL is consistently high-grade and metastatic. The emergence of ARL is associated with the presence of macrophage viral reservoirs, similar to what has been observed for HAD. HIV-infected macrophages, as seen by histology and HIV p24 staining, are present in approximately half of ARLs. Macrophage reservoirs recruit additional immune cells, including monocytes/macrophages, through the release of chemoattractants. Additionally, TAM are known to promote tumor progression for most cancer types, including lymphomas. This review will highlight and discuss the role of macrophage viral reservoirs in the development and progression of ARLs and hopefully, shed light on this new and interesting field.

KSHV/HHV8-associated lymphomas

This review looks at the current state of knowledge on primary effusion lymphoma (PEL) and other Kaposi sarcoma herpesvirus (KSHV)/human herpesvirus 8 (HHV8)-associated lymphomas. In 1995, KSHV DNA sequences were identified within a distinct subgroup of acquired immunodeficiency syndrome-related non-Hodgkin lymphomas localized in body cavities and presenting as pleural, peritoneal and pericardial lymphomatous effusions. Subsequently, the spectrum of KSHV/HHV8-associated lymphomas has been expanded by the identification of cases of extracavitary solid lymphomas without serous effusions. Despite the diversification in the clinical presentation of KSHV/HHV8-associated lymphomas, the majority of the cases reported demonstrated similar morphology, immunophenotype and KSHV/HHV8 viral status. KSHV/HHV8 infection is also in multicentric Castleman disease-associated plasmablastic lymphoma. The exact oncogenic mechanisms of KSHV/HHV8 are not clearly defined. The prognosis for KSHV/HHV8-associated lymphomas is poor. Novel approaches for therapy, outside traditional chemotherapy with CHOP (cyclophosphamide, doxorubicin, prednisone, vincristine), have been suggested. These include the addition of antiviral therapy as well as inhibition of specific cellular targets.

Gastrointestinal malignancies in HIV-infected or immunosuppressed patients: pathologic features and review of the literature

The gastrointestinal (GI) tract is a common internal organ to be involved by human immunodeficiency virus (HIV)-related malignancies. It is the second most common site for Kaposi sarcoma after skin, and the commonest visceral site, for Kaposi sarcoma in AIDS patients. GI lymphomas have been documented in approximately 25% of AIDS patients with systemic lymphomas. Moreover, GI involvement of AIDS-lymphoma has been associated with poor prognosis and short survival. Several other malignancies that occur in the GI tract are also closely related to HIV-infected or immunosuppressed individuals; these include posttransplant lymphoproliferative disorder, Epstein-Barr virus-associated smooth muscle tumors, anal precancerous lesions, and squamous cell carcinoma. As a result of active antiretroviral therapy, patients infected with HIV are living longer and are consequently at increased risk for development of cancer. Therefore, it is possible that the number of AIDS-associated malignancies will rise and the pattern of tumors may change in the future. In this paper, the clinicopathologic features of GI malignancies associated with AIDS patients are reviewed and the differential diagnosis with other mimic lesions is discussed.

Left ventricular non-Hodgkin lymphoma visualized on contrast echocardiography

We present a case of AIDS-related Burkitt's type cardiac lymphoma in a middle-aged woman with Epstein-Barr virus infection and profound immunodeficiency. The original features of our case include left ventricular location, female sex, and the use of contrast echocardiography to help establish the diagnosis.

AIDS and non-AIDS diffuse large B-cell lymphomas express different antigen profiles

Based on gene expression profiling, diffuse large B-cell lymphomas arising in immunocompetent patients can be divided into germinal center and activated B-cell types. Since little is known about acquired immunodeficiency syndrome associated diffuse large B-cell lymphomas, we tested whether the protein expression of germinal center and activated B-cell markers differed between acquired immunodeficiency syndrome (AIDS) vs non-AIDS diffuse large B-cell lymphomas. We immunohistochemically stained tissue microarrays of 39 de novo diffuse large B-cell lymphomas: 12 AIDS associated and 27 non-AIDS, with germinal center (BCL6, CD10, CyclinH) and activated B-cell markers (MUM1, CD138, PAK1, CD44, BCL2). We scored each case for percent positive cells (0-19%=0; 20-49%=1; 50-100%=2). The activated B-cell and germinal center summation scores of each case were used as (x, y) coordinate data points to construct two-dimensional contour-frequency plots. The contour plot of non-AIDS diffuse large B-cell lymphomas showed two distinct clusters: a cluster with a high germinal center phenotype (cluster 1) and a cluster with a high activated B-cell phenotype (cluster 3). In contrast, the AIDS-related diffuse large B-cell lymphomas formed a single aggregate (cluster 2) (P=0.02, Fisher exact test). When the contour plots of the AIDS-related and the non-AIDS cases were superimposed, cluster 2 of the AIDS cases expressed an intermediate germinal center/activated B-cell phenotype compared to clusters 1 and 3 of the non-AIDS diffuse large B-cell lymphomas. Our results confirm that non-AIDS diffuse large B-cell lymphomas segregate into two groups with either germinal center or activated B-cell phenotype. We report the new finding that the AIDS status of the patient predicts the immunophenotype of the diffuse large B-cell lymphomas.

Plasmablastic lymphoma of the oral cavity in an HIV-positive child

A 7-year-old boy with a positive history of vertical HIV transmission presented with a painful swelling over the left upper jaw of 20 days' duration. A provisional diagnosis of non-Hodgkin's lymphoma or embryonal rhabdomyosarcoma was made. Fine-needle aspiration cytology findings were inconclusive, and incisional biopsy tissue on routine stains gave an impression of small round cell tumor with plasmacytoid features. A series of histochemical stains and immunohistochemical studies was carried out to differentiate and characterize this tumor. The salient immunostaining was negativity with all routine small round cell tumor markers and positivity with CD138 and lambda light chain restriction. The heterogeneous presentation of plasmablastic lymphoma as a variant of diffuse large B-cell lymphoma and its histogenesis is documented. Potential pitfalls and differential characterization of AIDS-plasmablastic lymphoma from other closely related tumors are addressed. The importance of excluding other common pediatric small round cell tumors by immunohistochemistry is highlighted. To the best of our knowledge, this is the first report of this entity in a vertically transmitted HIV-positive child.

AIDS-related lymphomas: from pathogenesis to pathology

Human immunodeficiency virus (HIV)-associated lymphomas include: (1) lymphomas also occurring, although sporadically, in the absence of HIV infection. The vast majority of these lymphomas are high-grade B-cell lymphomas: Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL) with centroblastic (CB) features and DLBCL with immunoblastic (IBL) features; (2) unusual lymphomas occurring more specifically in HIV-positive patients and include two rare entities, namely 'primary effusion lymphoma' (PEL) and 'plasmablastic lymphoma' of the oral cavity. The pathological heterogeneity of acquired immunodeficiency syndrome-associated non-Hodgkin's lymphomas (AIDS-NHL) reflects the heterogeneity of their associated molecular lesions. In AIDS-BL, the molecular lesions involve activation of cMYC, inactivation of P53, and infection with Epstein-Barr virus (EBV). AIDS-IBL infected with EBV are characterised by frequent expression of latent membrane protein 1--an EBV oncoprotein. The biological heterogeneity of AIDS-NHL is highlighted by their histogenetic differences. Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 (KSHV/HHV8)-associated lymphomas, which often develop in persons with advanced AIDS, present predominantly as PEL. KSHV/HHV8 has also been recently detected in solid extracavitary-based lymphomas. The KSHV/HHV8-associated solid lymphomas are (1) unusual lymphomas that occur more specifically in HIV-positive patients; (2) extracavitary and arise in nodal and/or extranodal sites; and (3) histologically, they usually display a PEL-like morphology and plasma cell-related phenotype.

Cytologic features of plasmablastic lymphoma

BACKGROUND

Plasmablastic lymphomas (PBLs) were originally described exclusively in human immunodeficiency virus (HIV)-positive patients who presented with jaw or oral mucosa involvement. Recent studies have reported this neoplasm also in patients without HIV infection and involving sites other than head and neck. This lymphoma has a heterogeneous morphologic presentation but distinct phenotype.

METHODS

Cytologic features from four cases of histologically confirmed PBL were evaluated. The cytology specimens were evaluated for criteria as follow: cellularity, cell size and shape, pleomorphism, cytoplasmic characteristics, chromatin pattern, nucleolar features, and mitotic figures.

RESULTS

Specimens evaluated were two head and neck fine needle aspiration specimens, one anal smear, and one cerebrospinal fluid specimen. Atypical lymphocytes ranged from intermediate to large in size and demonstrated slight nuclear pleomorphism. The cytoplasm varied from scant to moderate in the alcohol-fixed slides. Nuclei were round with vesicular chromatin. Nucleoli varied from a prominent one to multiple small ones. Multinucleated cells and mitotic figures were easily identified in three of four cases. Tingible-body histiocytes were seen in one case. Ancillary studies in two cases demonstrated expression of CD138 with lack of CD20 expression.

CONCLUSION

PBL is a variant of large cell lymphoma with heterogeneous cytologic findings but distinct immunophenotype. Knowledge of the cytomorphologic spectrum of PBLs and detection of CD138 expression by flow cytometry can be helpful in achieving a correct diagnosis.

AIDS-related non-Hodgkin's lymphomas

This work reviews the current status of non-Hodgkin's lymphoma (NHL) in HIV infected patients. HIV infection remains at significantly increased risk for the development of NHL. The great majority of these lymphomas are high-grade monoclonal B-cell neoplasms often occurring in unusual sites. A number of genetic abnormalities have been found but additional studies are necessary to understand the etiology and pathogenesis of NHL in the setting of HIV infection. The cases in this paper have been seen on the Hematopathology service of the Tulane Health Sciences Center.

Differential gene expression in HIV/SIV-associated and spontaneous lymphomas

Diffuse large B-cell lymphoma (DLBCL) is more prevalent and more often fatal in HIV-infected patients and SIV-infected monkeys compared to immune-competent individuals. Molecular, biological, and immunological data indicate that virus-associated lymphomagenesis is similar in both infected hosts. To find genes specifically overexpressed in HIV/SIV-associated and non-HIV/SIV-associated DLBCL we compared gene expression profiles of HIV/SIV-related and non-HIV-related lymphomas using subtractive hybridization and Northern blot analysis. Our experimental approach allowed us to detect two genes (a-myb and pub) upregulated solely in HIV/SIV-associated DLBCLs potentially involved in virus-specific lymphomagenesis in human and monkey. Downregulation of the pub gene was observed in all non-HIV-associated lymphomas investigated. In addition, we have found genes upregulated in both non-HIV- and HIV-associated lymphomas. Among those were genes both with known (set, ND4, SMG-1) and unknown functions. In summary, we have demonstrated that simultaneous transcriptional upregulation of at least two genes (a-myb and pub) was specific for AIDS-associated lymphomas.

AIDS-related cancer in the era of highly active antiretroviral therapy (HAART): a model of the interplay of the immune system, virus, and cancer. "On the offensive--the Trojan Horse is being destroyed"--Part B: Malignant lymphoma

The impact of highly active antiretroviral therapy (HAART) on the incidence of non-Hodgkin's lymphoma was less obvious initially, although primary central nervous system lymphoma (PCNSL) has dropped precipitously since the introduction of HAART. The pathogenesis of acquired immunodeficiency syndrome-related lymphoma is multifactorial. Epstein-Barr virus plays a significant role in these diseases, especially Burkitt lymphoma and PCNSL. Data regarding the effect of HAART on the natural history and treatment outcomes of these malignancies are emerging. The possibility of direct and indirect roles of human immunodeficiency virus in the carcinogenesis suggests that antiretroviral therapy may be an important component of the treatment for these malignancies. The simultaneous administration of HAART and chemotherapy does not appear to significantly alter the toxicity profile, although the information with respect to the interaction of HAART and chemotherapy is limited. The use of biological agents, for example, monoclonal antibody against CD-20, is being explored to improve the clinical outcome of this disease.

Rheumatoid arthritis and malignant lymphomas

PURPOSE OF REVIEW

The reason for the increased lymphoma risk in patients with rheumatoid arthritis (RA) has remained unclear. Reports of lymphomas in patients treated with TNF-blockers have brought renewed interest in this issue. This review summarizes data on possible associations between RA and lymphomas, including different treatments and RA disease related risk factors.

RECENT FINDINGS

Some recent studies reported increased lymphoma risks linked to RA disease activity. The hypothesis that disease-modifying drugs, and in particular methotrexate, would increase the lymphoma risk receives little support. Observation times for the TNF-blocking therapies are still short, but so far no clear increased risk for lymphoma has been observed. Presence of Epstein-Barr virus, as analyzed with EBER in situ hybridization, appears to be uncommon in RA related lymphomas. Hypothetically, an increased proliferative drive caused by self or non-self antigens may play a role in lymphoma development in RA patients, but this has to be further studied.

SUMMARY

Rheumatologists need to be aware of the increased lymphoma risk in their RA patients. The reason for the increased lymphoma risk in RA patients is still unclear, but available studies rather support the hypothesis of a link between RA disease severity and the risk of lymphoma than increased risks associated with specific treatment regimens. To facilitate the future evaluation of lymphoma risks in connection with treatment, we suggest that patients treated with new drugs should be subject to structured surveillance. Collected information should include data about RA disease activity and severity.

Plasmablastic lymphoma in HIV+ patients: an expanding spectrum

AIM

To describe an unusual human immunodeficiency virus (HIV)-associated lymphoma in uncommon sites. Plasmablastic lymphoma is a distinctive HIV-associated tumour that was first described in the jaws and oral cavity. Only two cases (stomach and lung) have been documented in extra-oral sites.

MATERIALS AND METHODS

Four cases were encountered in HIV+ patients: three in the anorectal region and one which was nasal and paranasal. The cases were routinely processed and immunohistochemistry was performed on formalin-fixed paraffin-embedded tissue.

RESULTS

The cases showed the typical morphological appearances of a high-grade, blastic non-Hodgkin's lymphoma (brisk mitotic activity and tingible body macrophages). In addition, some cells had a plasmacytoid appearance and paranuclear clearing. Immunophenotypically, the tumour cells were negative for LCA, CD20 and CD45RA. However, a small proportion of cells (5%) were immunoreactive for CD79a and the majority were positive with VS38c, indicative of plasma cell differentiation. Kappa light chain and IgG heavy chain restriction was also detected.

CONCLUSIONS

Plasmablastic lymphoma may occur in extra-oral sites and has a characteristic immunophenotype including focal expression of CD31 by the neoplastic cells. Awareness of the absence of expression of conventional B-cell markers and its presence in unusual sites should facilitate the diagnosis of plasmablastic lymphoma in HIV+ patients.

[Muscle tumor in a girl with HIV infection: extranodal non-Hodgkin's lymphoma]

Non-Hodgkin's lymphomas are the most common cancers in children with human immunodeficiency virus (HIV) infection. Extranodal disease is the most common form of clinical presentation. Treatment with aggressive chemotherapy and highly active antiretroviral therapy has improved the prognosis of these children. We present a 10-year-old severely immunocompromised girl with HIV infection and non-Hodgkin's lymphoma manifested by a muscle mass.

Gene expression patterns in AIDS versus non-AIDS-related diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is more prevalent and more often fatal in AIDS patients compared to immune-competent individuals. Potential explanations for these differences include distinct tumorigenic mechanisms and/or altered cellular microenvironments. We previously discovered that the TCL1 (T-cell leukemia-1) proto-oncogene is expressed in a high proportion of AIDS-DLBCL compared to DLBCL cases and that aberrant TCL1 expression causes DLBCL in a new transgenic mouse model. Here, we continue to search for other genes that may contribute to the differential pathogenesis of DLBCL in AIDS. Gene subtraction yielded over 1800 potential AIDS-DLBCL candidates, of which about 50% were unknown and not further considered. The remaining 50% of genes were annotated and, when combined with miniarray screening from multiple patient samples, were reduced to 18 candidate genes for extended analysis. These 18 genes showed distinct patterns of expression in both AIDS-DLBCL and DLBCL samples. However, unlike TCL1, none of these genes was preferentially associated with either AIDS-DLBCL or DLBCL. Our data suggest that the increased incidence and severity of AIDS-DLBCL compared to DLBCL is likely due to crippled immune surveillance rather than to markedly different gene expression profiles.

Epidemiology of non-Hodgkin lymphomas and other haemolymphopoietic neoplasms in people with AIDS

HIV-infected individuals have a high risk of developing non-Hodgkin lymphoma (NHL). In Europe, the prevalence of AIDS with a concurrent NHL diagnosis increased from 3.6% to 5.4% between 1994 and 2000. In population-based record linkages between cancer registries and AIDS registries in the USA, Italy, and Australia, the relative risks of NHL in people with AIDS ranged between 15 for low-grade and T-cell NHL and 400 for high-grade NHL. The corresponding relative risk of Hodgkin's disease was about 10, whereas the risks for multiple myeloma and leukaemias were in the range 2 to 5. Since the introduction of highly active antiretroviral therapy in the more developed countries (1996), most studies have suggested a decline in the incidence of some types of NHL, most notably the primary brain form. In studies from Africa, the risk of HIV-associated NHL is about ten times less than that in the more developed countries, but underascertainment and earlier death from other AIDS-related illnesses may explain the relative lack of HIV-associated lymphomas.

Emerging pathways in the development of AIDS-related lymphomas

The clinicopathological range of AIDS-related non-Hodgkin lymphomas (NHLs) includes systemic lymphomas, primary central-nervous-system lymphomas, primary effusion lymphoma, and plasmablastic lymphoma of the oral cavity. Most AIDS-related NHLs belong to one of three categories of high-grade B-cell lymphomas: Burkitt's lymphoma, centroblastic lymphoma, and immunoblastic lymphoma. The pathological heterogeneity of AIDS-related NHL reflects the heterogeneity of their associated molecular lesions. In AIDS-related Burkitt's lymphoma, the molecular lesions involve activation of c-MYC, inactivation of p53, and infection with Epstein-Barr virus (EBV). AIDS-related immunoblastic lymphomas infected with EBV are characterised by frequent expression of latent membrane protein 1-an EBV oncoprotein. The biological heterogeneity of AIDS-related NHLs is highlighted by their histogenetic differences; AIDS-related NHLs are related to distinct B-cell subgroups (eg, germinal-centre or post-germinal-centre B cells). The phenotypic pattern of AIDS-related Burkitt's lymphomas and systemic AIDS-related centroblastic lymphomas closely reflects that of B cells in germinal centres. Conversely, the phenotype of AIDS-related immunoblastic lymphomas and AIDS-related primary effusion lymphomas reflects post-germinal-centre B cells in all cases. Despite their clinicopathological, genetic, and phenotypic heterogeneity, most lymphomas in patients with AIDS carry somatic mutations of immunoglobulin and BCL-6 genes. However, the somatic hypermutation mechanism functions aberrantly in a significant proportion of AIDS-related NHLs, causing the mutation of many genes, and possibly favouring chromosomal translocation, which may be a powerful contributor to malignant transformation. New molecular and virological evidence of such pathways and a greater knowledge of other biological features of AIDS-related NHLs may lead to new targets for pathogenetically and biologically oriented therapies.

Pathogenic roles for Epstein-Barr virus (EBV) gene products in EBV-associated proliferative disorders

Epstein-Barr virus (EBV) is associated with a still growing spectrum of clinical disorders, ranging from acute and chronic inflammatory diseases to lymphoid and epithelial malignancies. Based on a combination of in vitro and in vivo findings, EBV is thought to contribute in the pathogenesis of these diseases. The different EBV gene expression patterns in the various disorders, suggest different EBV-mediated pathogenic mechanisms. In the following pages, an overview of the biology of EBV-infection is given and functional aspects of EBV-proteins are discussed and their putative role in the various EBV-associated disorders is described. EBV gene expression patterns and possible pathogenic mechanisms are discussed. In addition, expression of the cellular genes upregulated by EBV in vitro is discussed, and a comparison with the in vivo situation is made.

Acquired immunodeficiency syndrome-associated lymphomas are efficiently lysed through complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity by rituximab

Rituximab (Mabthera) and alemtuzumab (Campath(R), Mabcampath(R)) are non-conjugated IgG1 therapeutic monoclonal antibodies directed against the CD20 and CD52 surface antigens respectively. They are presently used in the therapy of indolent B-cell non-Hodgkin's lymphoma (B-NHL) and of B-cell chronic lymphocytic leukaemia, and are thought to act mainly through complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Here we have analysed the capacity of these two monoclonal antibodies to lyse cell lines of acquired immunodeficiency syndrome (AIDS)-related B-NHL through either complement activation or antibody-dependent cytotoxicity. Rituximab strongly activated both CDC and ADCC against CD20-positive AIDS-NHL cells lines, inducing up to 60-98% and 20% specific lysis respectively. In contrast, alemtuzumab was a poor activator of CDC, even in the AIDS-NHL cell lines expressing high amounts of CD52, leading to a lysis of only 1-30%, whereas it was at least as strong as rituximab in inducing ADCC of the same lines (up to 30% specific lysis). Altogether, these data offer a first in vitro rationale supporting the therapeutic use of rituximab for CD20-positive AIDS-NHL.

Expression of cyclin-dependent kinase inhibitor p27(Kip1) in AIDS-related diffuse large-cell lymphomas is associated with Epstein-Barr virus-encoded latent membrane protein 1

Knowledge of the role of cell-cycle regulators in the pathogenesis of acquired immune deficiency syndrome-related non-Hodgkin's lymphomas (AIDS-NHLs) is scarce. Here we analyzed 86 systemic AIDS-NHLs and 20 AIDS-primary central nervous system lymphomas for expression of p27(Kip1), a negative regulator of cell-cycle progression belonging to the Kip family of cyclin-dependent kinase inhibitors. In parallel, we investigated the relationship between p27(Kip1), the lymphoma proliferation index, Epstein-Barr virus status, expression of cellular cyclin D3 and cyclin D1, and B-cell differentiation stage. We report that AIDS-immunoblastic lymphomas (AIDS-IBLs), either systemic or primarily localized to the central nervous system, consistently express p27(Kip1) protein (19 of 24 and 10 of 14, respectively) despite the high proliferative rate of the lymphoma clone, suggesting a failure of p27(Kip1) to inhibit the cell cycle in AIDS-IBL. Conversely, the remaining systemic AIDS-NHLs and AIDS-primary central nervous system lymphomas preferentially fail to express p27(Kip1). Expression of p27(Kip1) in Epstein-Barr virus-positive AIDS-NHLs generally associates with latent membrane protein 1 (LMP1) expression and is related to a late stage of B-cell differentiation, characterized by the BCL-6-/MUM1+/syn-1+/- phenotypic profile, whereas it seems to be unrelated to the expression of cellular cyclins. In B cells in vitro, induction of LMP-1 expression under the control of inducible promoters up-regulates expression of p27(Kip1), thus providing a putative mechanistic explanation for the association between LMP1 and p27(Kip1) observed in vivo. Overall, these data show that AIDS-IBL pathogenesis is characterized by loss of the inverse relationship between p27(Kip1) positivity and tumor growth fraction that is otherwise generally observed in normal lymphoid tissues and in most other types of NHLs.

AIDS-related non-Hodgkin's lymphomas: from pathology and molecular pathogenesis to treatment

In the highly active antiretroviral therapy (HAART) era, AIDS-related non-Hodgkin's lymphomas (AIDS-NHL) and their treatment still represent an open issue, because HAART may not be sufficient to prevent the development of NHL. The present spectrum of AIDS-NHL includes systemic lymphomas, primary central nervous system lymphomas, and 2 rare entities, primary effusion lymphomas (PEL) and plasmablastic lymphomas of the oral cavity. The vast majority of systemic AIDS-NHL belongs to 3 high-grade B-cell lymphomas: Burkitt's lymphoma (BL), immunoblastic lymphoma (IBL), and large-cell lymphoma (LCL). The pathologic heterogeneity of AIDS-NHL is correlated with the heterogeneity of the molecular lesions associated with these lymphomas. The molecular lesions associated with AIDS-BL involve activation of c-MYC inactivation of p53, and infection by Epstein-Barr virus (EBV). EBV infection occurs in 40% of LCL cases and in 90% of IBL cases. Rearrangements of BCL-6 are detected in 20% of AIDS-LCL cases. In the presence of EBV infection, BCL-6 expressing AIDS-LCL fails to express the latent membrane protein 1 (LMP1) antigen. Conversely, AIDS-IBL are characterized by absent BCL-6 expression, absence of BCL-6 rearrangements, and frequent expression of LMP1. Consistently, the molecular pathways of viral infection and lesions of cancer-related genes associated with AIDS-NHL vary substantially in different clinicopathologic categories of the disease. The marked degree of biologic heterogeneity of AIDS-NHL is highlighted by their histogenetic differences, because AIDS-NHL are related to distinct B cell subsets (ie, germinal center [GC] or post-GC B cells). The phenotypic pattern of AIDS-BL and systemic AIDS-LCL closely reflects B cells residing in the GC, namely centroblasts and centrocytes. Conversely, the phenotype of AIDS-IBL, either systemic or localized primarily to the central nervous system, and AIDS-PEL reflects post-GC B cells in all cases. New information on the molecular and virologic pathogenesis of AIDS-NHL may serve as a point of attack for pathogenic-driven therapies. Moreover, a greater knowledge of other biologic features of these tumors may help investigators identify new potential targets for "intelligent" therapies.