CD40 antigen is expressed by endothelial cells and tumor cells in Kaposi's sarcoma.

The CD40 antigen is a member of the tumor necrosis factor receptor/nerve growth factor receptor superfamily and is involved in cell proliferation, differentiation, and survival. Using different monoclonal antibodies, we found CD40 expression by immunohistochemistry on CD31- and CD34-positive Kaposi's sarcoma spindle cells in all tumors of 18 HIV-1 seropositive and 4 HIV-1 seronegative patients. Western blot analysis of tumor lysates detected a 48- to 50-kd glycoprotein corresponding to the CD40 antigen expressed by B lymphocytes. CD40 expression was also detectable in one of four cultures of spindle cells derived from Kaposi sarcoma tissue. Treatment of the CD40-positive spindle cells but not of the CD40-negative ones with interferon-gamma up-regulated CD40 surface expression. Besides on Kaposi sarcoma tumor cells, CD40 was distinctly present on vascular endothelial cells in areas within and adjacent to the tumors and in benign inflammatory lesions such as granulation tissue of HIV-1-negative patients. In contrast, CD34-negative endothelia of thin walled vessels, most likely lymphatics, were predominantly CD40 negative. Only faint or no CD40 expression was found on endothelial cells in normal skin. We conclude from our data that expression of the CD40 antigen by endothelial cells is up-regulated during tissue inflammation. As signaling through CD40 is able to increase cell survival, expression of CD40 by Kaposi sarcoma tumor cells might play an important role in the pathogenesis of this neoplasm.     

Kaposi's sarcoma and HIV.

Recently published informed debate affords strong indication that in patients with the Acquired Immune Deficiency Syndrome, HIV cannot, directly or indirectly, be the cause of Kaposi's sarcoma. This paper provides reasons for disallowing a current alternative theory that Kaposi's sarcoma is due to an unidentified sexually transmitted infectious agent and proposes instead that Kaposi's sarcoma is the result of prolonged and repeated exposure to nitrites and/or semen. If this alternative hypothesis is strengthened by confirmation of its predictions then the relationship of HIV to Kaposi's sarcoma, one of the principal AIDS-associated diseases, becomes somewhat remote. This may facilitate a shift of emphasis and encourage the development of alternative therapies.     

Myogenic cells in Kaposi's sarcoma: an ultrastructural study.

An ultrastructural study of a metastatic Kaposi's sarcoma in a cervical lymph node demonstrated the presence of endothelial cells, smooth muscle cells, fibroblasts and myofibroblasts. Some of these cells exhibited phagocytic activity in relation to extravasated red blood cells. The ultrastructural features favour the suggestion of an origin of Kaposi's sarcoma from pluripotential mesenchymal cells which may differentiate into more specialised cell types including endothelial, smooth muscle, fibroblastic and myofibroblastic cells.     

Kaposi's sarcoma revisited

Kaposi's sarcoma is a puzzling condition of unclear, possibly endothelial origin. It is divided into four distinct types regarding the affected population: classic in elder men of Ashkenazi Jewish and Mediterranean origin; endemic in African infants and young males; iatrogenic in patients under immunosuppressive regimens; epidemic in men having sex with men affected by AIDS. The exact etiopathogenesis of Kaposi's sarcoma continues to elude its researchers. Nonetheless, it has been discovered that human herpesvirus 8 is essential but not sufficient for sarcoma development. Also, iron exposure of populations inhabiting regions with volcanic soils has been suggested to play a pivotal role in the classic and endemic Kaposi's sarcoma etiology. The epidemic Kaposi's sarcoma is strongly associated with HIV's detrimental effect on immune system and HIV's Tat protein proangiogenic properties. Because Kaposi's sarcoma is found also in men having sex with men without AIDS, it has been proposed that certain lifestyle features (e.g. massive semen exposure and inhalant nitrites) may promote transformation of endothelial cells of both lymphatic and vascular origin. Despite numerous studies on Kaposi's sarcoma, it continues to be an incurable disease. The therapeutic approach includes local treatment and systemic administration of cytotoxic, immunomodulator and antiviral drugs. Because of the increasing prevalence of Kaposi's sarcoma, especially in certain parts of Africa, a better understanding of this condition is necessary.     

Ewing sarcoma cells express RANKL and support osteoclastogenesis

Ewing sarcoma (ES) is a primary malignant round cell tumour of bone characterized by rapid and extensive osteolysis. Cellular mechanisms underlying the rapid bone resorption in ES have not been characterized. Osteoclasts are marrow-derived multinucleated cells that effect tumour osteolysis. The role of ES tumour cells in influencing osteoclast formation and/or directly contributing to the osteolysis in ES has not been determined. Using a tissue culture bioassay, we found that lacunar resorption is not carried out by (CD99(+) ) ES tumour cells, but by (CD68(+) ) macrophage/osteoclast-like cells; this resorption occurred in the absence of the osteoclastogenic factor, receptor activator of nuclear factor κB ligand (RANKL). ES cell lines cultured directly on dentine slices did not resorb the mineral or organic components of the bone matrix. Immunohistochemistry of ES tissue microarrays, western blotting, and RT-PCR studies showed that ES cells strongly expressed both RANKL and macrophage-colony stimulating factor (M-CSF), two major osteoclastogenic factors. When co-cultured with human monocytes, ES cells induced the formation of TRAP(+) osteoclastic cells. Conditioned medium from cultured ES cells did not result in osteoclast formation, indicating that cell-cell contact is required for ES-induced osteoclastogenesis. Our findings indicate that ES cells do not resorb bone directly but that they may support osteoclast formation by a RANKL-dependent mechanism.     

Avastin enhances photodynamic therapy treatment of Kaposi's sarcoma in a mouse tumor model.

The goal of the current study was to determine if the antiangiogenic drug Avastin would improve the effectiveness of Photodynamic Therapy (PDT) in a xenograft model of Kaposi's sarcoma (KS). Human KS-Imm tumors transplanted in nude mice were treated with Photofrin-mediated PDT. Expression parameters of proangiogenic molecules were documented and the tumoricidal effectiveness of PDT combined with the VEGF inhibitor Avastin was determined. PDT induced increased expression of HIF-1alpha, VEGF, PGE2, TNF-alpha, and IL-1beta within treated KS tumor tissue. Significant overexpression of KS cell derived human VEGF and to a lesser extent overexpression of host cell derived mouse VEGF were detected within treated tumors. Combining PDT with Avastin resulted in a significant increase in the long-term responsiveness of treated KS tumors when compared to individual treatments. These results demonstrate for the first time that Avastin can improve PDT treatment effectiveness and suggest that VEGF inhibitors may ameliorate the clinical efficacy of PDT.     

Histogenesis of Kaposi's sarcoma

The origin of Kaposi's sarcoma from the endothelium and fibroblast-like cells of a vascular wall is proven on the basis of complex pathomorphological, immunomorphological, autoradiographic and electron microscopical investigation of tumour biopsies. Depending upon the predominating cell type of origin, the tumour in its different parts, may form the structures of either different variants of angiomas or fibrosarcomas.     

Human herpesvirus 8 in Kaposi's sarcoma and Kaposi's sarcoma-mimicking vascular tumors.

Kaposi''s sarcoma (KS) had been a rare and unusual vascular tumor until a recent epidemic of a disseminated and fulminant form of KS in AIDS patients. Infectious agents have been suspected of causing KS, and recently partial genomic DNA sequences of human herpesvirus 8 (HHV8) have been identified in AIDS-associated KS lesions. Since then, genomic DNA sequences of HHV8 have been isolated in other forms of KS. Although the partial genomic DNA sequence of HHV8 was reported to be, if rare, identified in vascular tumors other than Kaposi''s sarcoma (KS), the presence of HHV8 in a very large fraction of KS indicates that detection of HHV8 by PCR is a useful auxiliary tool in differentiating KS from other KS-mimicking vascular tumors. We examined whether the 233-bp segment of the viral DNA was detected in Korean patients with KS and other KS-mimicking vascular tumors. HHV8 sequences were identified in all of nine classic type of KS but not in three epithelioid hemangioendotheliomas and seven angiosarcomas. Our results confirm the relatively restricted distribution of HHV8 and also argue against the likelihood of secondary colonization of KS cells by HHV8.     

Human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) DNA in Kaposi's sarcoma lesions,AIDS Kaposi's sarcoma cell lines,endothelial Kaposi's sarcoma simulators,and the skin of immunosuppressed patients.

We used the polymerase chain reaction on 63 tissue specimens of histologically staged classic Kaposi''s sarcoma (KS) from 40 patients, 14 specimens from 14 acquired immune deficiency syndrome (AIDS)-KS cases (all from the same geographic area over a 10-year period), and peripheral blood mononuclear cells from 1 of the non-AIDS KS patients to amplify a specific 210-bp genomic sequence of the newly discovered KS-associated herpesvirus (KSHV). Also tested were 86 benign and malignant endothelial lesions, which potentially simulated each KS histological stage and were further matched by age approximation and by sex with a classical KS specimen. The lesions included hemangioma, lymphangioma, pyogenic granuloma, and angiosarcoma. KSHV was also sought in multiple well characterized vascular endothelial cell lines from AIDS-KS lesions and in 20 mainly cutaneous benign and malignant lesions from 15 immunosuppressed transplant patients. Overall, 92% of KS tissue specimens, representing 88% of classical KS and 100% of AIDS-KS patients, and in addition the sample of peripheral blood mononuclear cell DNA, were positive as visualized on ethidium bromide gels and confirmed by Southern blot hybridization (only 1 case was negative on gell visualization but positive on Southern blot), thus confirming the close association of KSHV with KS of different clinical forms. None of the various other endothelial lesion, skin lesions in immunosuppressed patients, or AIDS-KS endothelial cell lines contained amplifiable KSHV DNA, which indicates that reactivation of KSHV is not present in the skin lesions of immunosuppressed patients and probably is not a ubiquitous agent that secondarily infects proliferative endothelium. The absence of amplifiable virus DNA in the cultured endothelium of KS suggests that the stimulus for angioproliferation originates in another host cell or under conditions not reproduced in culture. The polymerase chain reaction is a specific and sensitive means of verifying KS in the differential diagnosis of angioproliferative lessons.     

Molecular analysis of clonality in Kaposi's sarcoma.

BACKGROUND: Kaposi''s sarcoma is considered to be an angioproliferative disease associated with a novel herpesvirus (KSHV/HHV8), but the precise pathophysiology of the lesion remains unclear. The study of clonality in Kaposi''s sarcoma using X linked DNA polymorphism has been difficult so far, because of a very strong prevalence of the disease in males. AIMS: To study the clonality of Kaposi''s sarcoma lesions. METHODS: An assay based on a methyl sensitive restriction digest followed by polymerase chain reaction (PCR) amplification of the highly polymorphic human androgen receptor (HUMARA) gene was used. Tissues from Kaposi''s sarcoma lesions and control tissues from the same patients were obtained from seven females, four with classic Kaposi''s sarcoma and three with AIDS associated Kaposi''s sarcoma. A cutaneous angiosarcoma was also analysed, for comparative purposes, and showed evidence of clonality after HpaII digestion. RESULTS: All patients were heterozygous for the HUMARA polymorphism and informative for analysis. In all patients, including four with a nodular form of Kaposi''s sarcoma and more than 70% spindle cells in the lesion, a polyclonal pattern of inactivation could be demonstrated. CONCLUSIONS: The Kaposi''s sarcoma lesion is first of all a polyclonal cell proliferation.     

Lymphadenopathic tumor exhibiting intermingled features of Kaposi's sarcoma, malignant lymphoma, and angiofollicular hyperplasia.

A 56-year-old man presented with an inguinal lymph node enlargement. Histologic study of the tumor revealed three intermingled pathologic lesions: a nodular small cell lymphoma, an angiofollicular hyperplasia of vasculohyaline type, and a vascular neoplasia closely resembling Kaposi's sarcoma. The patient was immunocompetent and denied any homosexual relationships, transfusions, or drug use. The serum was negative for the presence of human immunodeficiency virus antibody. Computed tomographic scan and ultrasound examination revealed no other lymphadenopathies. This case shows that both hyperplastic and neoplastic lymphoid proliferations can occur simultaneously with vascular neoplasia. It thereby suggests that the neoplastic populations might interact to favor the tumor growth, the sequence and the nature of the stimulating events remaining unclear.