HIV-1 Tat mimetic of VEGF correlates with increased microvessels density in AIDS-related diffuse large B-cell and Burkitt lymphomas.

Angiogenic switch marks the beginning of tumor's strategy to acquire independent blood supply. In some subtypes of non-Hodgkin's lymphomas, higher local vascular endothelial growth factor (VEGF) expression correlates with increased microvessel density. However, this local VEGF expression is higher only in tumors with elevated expression of the receptors of the growth factor, suggesting an autocrine growth-promoting feedback loop. Several studies have indicated that VEGF receptors are also targeted by Tat protein from the HIV-1-infected cells. Given the similarity of the basic region of Tat to the angiogenic factors (basic fibroblast growth factor, VEGF), Tat mimics these proteins and binds to their receptors. We evaluated the role of HIV-1 Tat in regulating the level of VEGF expression and microvessel density in the AIDS-related diffuse large B-cell (DLBCL) and Burkitt lymphomas (BL). By luciferase assay, we showed that VEGF promoter activity was downregulated in vitro in cells transfected with Tat. Reduced VEGF protein expression in primary HIV-1 positive BL and DLBCL, compared to the negative cases, supported the findings of promoter downregulation from the cell lines. Microvascular density assessed by CD34 expression was, however, higher in HIV-1 positive than in HIV-1 negative tumors. These results suggest that Tat has a wider angiogenic role, besides the regulation of VEGF expression. Thus, targeting Tat protein itself and stabilizing transient silencing of VEGF expression or use of monoclonal antibodies against their receptors in the AIDS-associated tumors will open a window for future explorable pathways in the management of angiogenic phenotypes in the AIDS-associated non-Hodgkin's lymphomas.

The effects of HIV-1 Tat protein on cell cycle during cervical carcinogenesis.

The role of HPV in the carcinogenesis of intraepithelial and invasive anogenital lesions is currently well established. E6 and E7 oncoproteins of high-risk HPV genotypes are known to inactivate p53 and pRb pathways. Several studies have described an increased prevalence and recurrence of both cervical HPV infection and invasive cervical cancer among HIV-1 positive women compared to HIV-1 negative cases. For these reasons, cervical cancer is considered an AIDS-defining neoplasm. Unlike other AIDS-associated neoplasms, the occurrence of cervical cancer is independent of immune suppression. HIV-1 infection in patients with high grade precancerous lesions and invasive cervical cancers results in a therapy refractory and more aggressive disease phenotype, which is not yet well understood at the molecular level. An upregulation of HPV E6 and E7 gene expressions by HIV-1 proteins such as Tat has been documented by some authors. However, the role of HIV-1 in cervical carcinomas is still unclear. It is already known that HIV-1 Tat protein is able to influence cell cycle progression. Altogether, these facts led us to investigate the effects of Tat on the expression of cell cycle regulator genes. After transfection of HeLa cells with Tat, we analyzed the expression of cell cycle regulators from these cells by IHC and Real-time PCR. A significant reduction in the expression of cell cycle inhibitors of transcription and an increase in the levels of proliferation markers were observed. These results suggest that HIV-1 may enhance cervical carcinogenesis by promoting cell cycle progression. We also found that this HIV-1 Tat-induced cell proliferation was not dependent on the E2F family of transcription factors, and therefore postulate that Sp factors may be involved.

IRTA1+ monocytoid B cells in reactive lymphadenitis show a unique topographic distribution and immunophenotype and a peculiar usage and mutational pattern of IgVH genes.

The origin and function of monocytoid B cells (MBCs) are poorly understood. Taking advantage of their strong expression of IRTA1 (a receptor that is also associated with MALT marginal zone B cells), we have comprehensively analysed MBCs in 25 cases of lymphadenitis of different aetiologies, shedding new light on the topographical distribution, immunophenotype and IgV(H) gene usage and mutational profile of this B cell subset. IRTA1(+) MBCs, although predominantly located in the subcapsular and intermediary sinuses, were also observed scattered within germinal centres (GCs) in all lymphadenitis cases examined. The molecular characterization of IgV(H) genes revealed that IRTA1(+) MBCs residing in different areas of the lymph node (subcapsular sinus, intermediary sinuses and GCs) can be clonally related (with intraclonal variation), and that those located in GCs are consistently more mutated and selected for expression of a functional antigen receptor than those located in the sinuses. Moreover, by contrast, IRTA1(+) MBCs in GCs express the memory B cell marker CD27. Finally, in toxoplasmic lymphadenitis, the IRTA1(+) MBC population shows a highly preferential usage of the V(H) genes 3-7 and 3-30 (without any obvious peculiarity in their CDR3s), possibly suggesting that a superantigen expressed by Toxoplasma gondii may be involved in the early activation of this B cell subset.

HIV-associated malignant lymphomas in Kenya (Equatorial Africa)

The clinical and pathological features of acquired immune deficiency syndrome (AIDS)-related lymphomas, including their relationship with other viruses, such as Epstein-Barr virus (EBV) and human herpes virus-8 (HHV8), have been the subject of several studies from North America and Europe. No consistent data have been reported in Africa, where AIDS runs an epidemiological and clinical course different from that observed in Western countries. We retrospectively evaluated the presence of human immunodeficiency virus (HIV), HHV8, and EBV in 146 cases of malignant lymphomas collected in Kenya (Equatorial Africa), with the use of polymerase chain reaction (PCR) and in situ hybridization (ISH). The PCR technique confirmed HIV infection in 16 HIV-seropositive subjects (11%) and showed the presence of HIV sequences in five additional cases (3%) in which the occurrence of lymphoma was the only clinical manifestation. Our findings suggest that AIDS-related lymphomas are not pathogenetically homogenous, and different mechanisms may contribute to lymphomagenesis in these severely immunocompromised patients. In our series, no association of Hodgkin's disease (HD) with HIV infection could be shown. Among non-HIV-related lymphomas, EBV was present in 94% of Burkitt lymphoma (BL) occurring in patients younger than 15 years of age, in 87% of HD independently of age, sex, and histological types, in 60% of anaplastic large cell lymphoma (ALCL), and to a lesser extent (13%) in large B-cell lymphoma (LBCL) cases. Only one tumor, a case of HD, showed HHV8 by PCR.

Updating on in-vivo and in-vitro effects of heparin and other glycosaminoglycans (mesoglycan) on arterial endothelium: a morphometrical study.

Glycosaminoglycans, which include heparin, heparansulfate and dermatansulfate, are substances that exhibit many significant biological activities. In-vitro and in-vivo experiments for studying the effects of heparin and an association of heparan-like glycosaminoglycan and dermatansolfate (mesoglycan) on aortic arterial endothelium were performed. The studies were developed by means of computerized morphometric techniques. The in-vitro tests, performed on bovine aortic endothelial cells, have revealed an increase in survival rate, enhancement of cell density at confluence, and increase of nucleus/cytoplasm ratio, after "in-vitro" administration of heparin or mesoglycan. The in-vivo tests have revealed a minor development of aortic intimal lipid deposition in mesoglycan-treated hypercholesterolaemic rabbits. Our morphometrical results confirmed by statistical tests strongly support the data collected in the literature over many years on the protective effects of mesoglycan and heparin on endothelium.

Thromboresistance of the arterial wall: the role of heparin and glycosaminoglycans.

Thromboresistance of the arterial wall is the result of many factors which dynamically interact with each other. Glycosaminoglycans (GAG), among which heparin, synthesized by endothelial cells, smooth muscle cells, and fibroblasts, play an important role in determining vessel wall non-thrombogenicity. We are describing morphological-morphometrical characterization (increase in endothelial cell density and nucleus/cytoplasm ratio) of bovine aortic endothelial cells grown in the presence of heparin and other GAGs.

Reduction of pinocytotic vesicle surface density in cultured bovine aortic endothelial cells. A quantitative ultrastructural freeze-etching study.

The development of culture techniques for endothelium of the large vessels has stimulated many studies to understand endothelial functions in normal and pathological conditions. In this report we describe that in primary cultures the mean surface density of pinocytotic vesicles, evaluated by computerized morphometric analysis of endothelial cell plasma-membrane, dramatically decreases with respect to that of the cells immediately detached from the arterial wall (6.7 +/- 1.1 microns2 against 19.5 +/- 2.2 microns2, p less than 0.001). The results are unchanged if the cells are enzymatically or mechanically detached from the vessel wall or from the culture flask. After the first passage, the mean surface density of pinocytotic vesicles decreases further (2.5 +/- 1.3 microns2 p less than 0.01). After the 2nd and the 3rd passages, the morphometrical values of endothelial cell plasma-membrane remain low (1.5 +/- 0.2 microns2; 2.5 +/- 0.2 microns2). When endothelial cultures are employed to study pathological aspects of disease, not only the aging process but also the possible occurrence of early changes have to be taken into consideration.