Angiogenic properties of Kaposi's sarcoma-derived cells after long-term culture in vitro

Cytochemical and molecular properties of simian virus 40 transformed Kaposi's sarcoma-derived cells: evidence for the secretion of a member of the fibroblast growth factor family

Contact-inhibited Kaposi's sarcoma-derived cells (KS cells) were transfected with Simian Virus 40 (SV40) DNA. Transformed cells (SV-KSC) were selected for their capacity to form foci on monolayers of the low-malignant KS cells. Isolated SV-KSC foci were found to contain integrated SV40 DNA sequences and to express SV40 large T-antigen. Several differentiation properties of KS cells are retained in the SV40 transformants, e.g., expression of vimentin and the endothelial cell marker BMA 120. In contrast to the maternal KS cells, SV-KSC are capable of growing in platelet-derived growth factor (PDGF)-depleted platelet-poor-plasma serum (PPPS) and in soft agar. However, they are not tumorigenic in nude mice. Expression of the oncogenes c-myc, c-N-ras, c-Ha-ras, and p53 is significantly elevated in SV-KSC, whereas c-fos and c-erb B expression is comparable to that of KS cells and fibroblasts. Conditioned medium from SV-KSC can substitute for PDGF when PDGF-dependent, nontransformed KS cells are grown in PPPS. Biochemical analysis of the SV-KSC supernatant and PDGF A and B mRNA expression analysis provide evidence that the mitogenic activity is not due to a PDGF-like growth factor. On the other hand, there is evidence to indicate that the SV-KSC mitogen is a member of the fibroblast growth factor family. SV-KSC represent an interesting model system for the study of different degrees of malignancy of cultured mesenchymal cells and especially provide an important source for the isolation of a potent growth factor for KS cells and other mesenchymal cells in vitro.

Cytocidal effect caused by the envelope glycoprotein of a newly isolated avian hemangioma-inducing retrovirus

We isolated a field strain of avian hemangioma retrovirus (AHV) which induces a cytopathic effect (CPE) on cultured avian and mammalian cells shortly after infection. The kinetics of cell killing were dependent on the multiplicity of infection. The CPE on avian and mammalian cells was independent of virus replication, because UV-irradiated virus led to cell death as well. Biochemical and genetic experiments indicated that AHV env gene products were responsible for the CPE. Partially purified AHV envelope glycoproteins (gp85), but not those of the Rous sarcoma virus Prague C strain, induced a CPE. Rous-associated virus type 1, in which the env region was replaced by the AHV gp85 region, induced a CPE on avian and mammalian cultured cells. Therefore, we suggest that CPE is induced by AHV via interaction between viral gp85 and the cell membrane. This mode of CPE is unique among avian sarcoma-leukemia viruses.

Phenotypic comparison between mesothelial and microvascular endothelial cell lineages using conventional endothelial cell markers, cytoskeletal protein markers and in vitro assays of angiogenic potential

Endothelial and mesothelial cells are mesodermally derived simple squamous epithelial cells. A controversy concerning the ontogenetic origin of neoplasms derived from these cell types, commonly cited in the literature, is whether Kaposi's sarcoma is a mesothelioma or an angioma. To assess the similarities and differences between these cell types, pulmonary microvascular endothelial cells (PMVEC) and pericardial mesothelial cells (PMC) were cultured in vitro. PMVEC and PMC were found to be difficult to distinguish from one another by histological criteria alone. Both cell types formed contact-inhibited, and 'cobblestone', monolayers typical of simple epithelial cells. PMVEC and PMC demonstrated positive immunoreactivity to Factor VIII-related antigen and angiotensin-converting enzyme (ACE) antigen. They also showed uptake of 1,1'-dioctacecyl-1,3,3,3',3-tetramethyl-indocarbocyanine perchlorate acetylated low density lipoprotein (DiI-Ac-LDL) in 4 h. Both PMVEC and PMC expressed low ACE activities when compared to macrovessel endothelial cells. PMVEC and PMC shared similar isoform profiles for vimentin and actin. Both cell types expressed the simple epithelial keratins, cytokeratins 8 and 19, though PMC contained 50% more cytokeratins than PMVEC. Additionally, PMC contained cytokeratin 18, an intermediate filament protein not detectable in PMVEC. PMC formed 15 times as many epithelial ringlets or "stomata" as PMVEC. PMVEC but not PMC could be induced in vitro to differentiate into branching tube-like structures in response to their culture environment. Reorganization of PMVEC into vessel-like structures was more rapid and complete than PMC when embedded in three-dimensional collagen I lattices, cultured on Matrigel or exposed to a shaped-pulsed electromagnetic field. The angiogenic response of PMVEC to specialized culture conditions in vitro may reflect their phenotypic differentiation state characterized by anastomosing vascular structures in vivo, whereas PMC remain differentiated into monolayer sheet-like structures.

Human retroviruses: their role in neoplasia and immunodeficiency

Human retroviruses (HTLVs and HIVs) infect the cells of the immune system and cause mild-to-severe immune dysfunction. They are directly or indirectly responsible for associated neoplasia and central nervous system disorders. The study of these viruses is of great importance, not only because they cause grave illnesses like AIDS, neoplasias, and CNS disease, but also because they have the ability to exert such fine levels of gene regulatory control in their replication and expression. These studies will ultimately shed light on fundamental mechanisms of genetic control in human cells in their normal state and the alterations of these controls in neoplastic or immunologically aberrant states.

Endothelioma cells expressing the polyoma middle T oncogene induce hemangiomas by host cell recruitment

Mouse endothelioma cells expressing the polyoma middle T oncogene induced hemangiomas in a variety of species such as mice, rats, chicks, and quails. In embryos and newborn mice the hemangiomas expanded within 10-18 hr of injection, disrupting the vasculature and causing the death of the animal. In contrast, the hemangiomas formed a stable structure reminiscent of benign human hemangiomas in adult mice within 5 days. Analysis of the cells comprising the hemangioma revealed that over 95% of the endothelial cells were host derived. No induction of host cell proliferation was detected, and no endothelial mitogens were secreted by the endothelioma cells in vitro. The maintenance of the hemangioma appeared to require the continuous presence of endothelioma cells. The results indicate that these endothelioma cells act as a potent stimulating agent in the rapid formation of hemangiomas by recruiting nonproliferating host endothelial cells.

Cells derived from sporadic and AIDS-related Kaposi's sarcoma reveal identical cytochemical and molecular properties in vitro

We have established 40 cell cultures from biopsies of 5 patients with sporadic Kaposi's sarcoma (KS) and compared them with cell cultures derived from KS biopsies of AIDS patients. Immunocytochemical staining of sporadic KS cells revealed the same endothelial cell markers as those expressed on AIDS-KS cells, indicating that both types of KS might be of endothelial cell origin. In contrast to clinical features, in vitro growth properties showed no differences. KS cells of both types reveal a low degree of malignancy but can be distinguished from fibroblasts by a higher passage number in low serum concentrations and a more pronounced dependence on platelet-derived growth factor (PDGF). The DNA of 12 cell lines of both types of KS was negative for genomic equivalents of hepatitis B virus (HBV), cytomegalovirus (CMV) and, in the case of AIDS-KS, for human immunodeficiency virus (HIV). No rearrangements or amplifications of several oncogenes, often involved in human tumors, were detected. The expression of these oncogenes by sporadic and AIDS-KS cells, as analyzed by Northern blotting, was comparable to that of normal dermal fibroblasts from the same patients. Our results indicate that the 2 types of Kaposi's sarcoma possess identical cytochemical and molecular properties. They are probably weakly malignant neoplasms of endothelial cell origin, and paracrine growth stimulation appears to be important for their maintenance and progression.

Analysis of human KS biopsies and cloned cell lines for cytomegalovirus, HIV-1, and other selected DNA virus sequences

Investigation into a possible role of several human viruses, including human cytomegalovirus (HCMV), human immunodeficiency virus (HIV-1), hepatitis B virus (HBV), human herpesvirus 6 (HHV6), and Epstein-Barr virus (EBV) in the pathogenesis of Kaposi's sarcoma (KS) has resulted in the lack of an association of these viruses in KS biopsy and cloned KS cell line specimens. Since nearly all patients with KS, including those with HIV-associated KS, have a high incidence of HCMV infection, HCMV has been proposed to be etiologically associated with KS. Moreover, our previous studies showed the retention of HCMV morphological transforming region II (mtrII) in both transformed and tumor-derived cell lines. As a result, we focused on the nucleic acid hybridization analysis of both KS biopsies from AIDS patients as well as cloned KS endothelial cell lines for HCMV mtrII sequences. We also analyzed KS biopsy and KS cloned cell line specimens for HIV-1, HBV, HHV6, and EBV sequences, since these viruses have also been implicated in the etiology of KS. In one set of experiments, Southern blot analysis revealed the presence of HCMV mtrII sequences in two of six KS biopsies; in other experiments, HBV sequences were found in one of seven KS biopsies. No hybridization in any biopsy tissue was detected for HIV-1 DNA sequences. The analysis of six independently derived cloned KS cell lines was next studied. All these lines were negative for hybridization to the HCMV mtrII transforming fragment as well as to subgenomic fragments of HHV6 and EBV.(ABSTRACT TRUNCATED AT 250 WORDS)

An immunohistological and genotypic study of the plasma cell form of Castleman's disease

The plasma cell variant of Castleman's disease (angiofollicular hyperplasia) is an uncommon and poorly understood lymphoproliferative disorder which may be associated with a wide variety of systemic features. The clinical, pathological, immunophenotypic and genotypic features of a series of five cases are presented. The clinical manifestations were variable but systemic features were present in four cases. Histologically, all five cases were similar. The characteristic follicle-like structures are composed of concentric rings of B-lymphocytes with a mantle zone phenotype, surrounding an inner core of dendritic reticulum cells. The central regions are composed of plump cells that express Factor VIII related antigen, stain with Ulex europaeus I and are associated with laminin immunoreactivity. Many of these cells stain with Ki67 indicating cellular proliferation. Between these 'follicles', plasma cells are present interspersed between high endothelial venules. Using immunohistochemical techniques two cases were polyclonal, whilst in two others unequivocal lambda/IgA restriction was present; in the other case an intermediate picture of lambda/IgA predominance was apparent. Genotypic studies in three cases indicated immunoglobulin gene rearrangements but germ line T-cell receptor genes. The significance of the apparent clonal proliferation of plasma cells is discussed and a unifying model of Castleman's disease is proposed.

Human immunodeficiency virus and acquired immunodeficiency syndrome: correlation but not causation

AIDS is an acquired immunodeficiency syndrome defined by a severe depletion of T cells and over 20 conventional degenerative and neoplastic diseases. In the U.S. and Europe, AIDS correlates to 95% with risk factors, such as about 8 years of promiscuous male homosexuality, intravenous drug use, or hemophilia. Since AIDS also correlates with antibody to a retrovirus, confirmed in about 40% of American cases, it has been hypothesized that this virus causes AIDS by killing T cells. Consequently, the virus was termed human immunodeficiency virus (HIV), and antibody to HIV became part of the definition of AIDS. The hypothesis that HIV causes AIDS is examined in terms of Koch's postulates and epidemiological, biochemical, genetic, and evolutionary conditions of viral pathology. HIV does not fulfill Koch's postulates: (i) free virus is not detectable in most cases of AIDS; (ii) virus can only be isolated by reactivating virus in vitro from a few latently infected lymphocytes among millions of uninfected ones; (iii) pure HIV does not cause AIDS upon experimental infection of chimpanzees or accidental infection of healthy humans. Further, HIV violates classical conditions of viral pathology. (i) Epidemiological surveys indicate that the annual incidence of AIDS among antibody-positive persons varies from nearly 0 to over 10%, depending critically on nonviral risk factors. (ii) HIV is expressed in less than or equal to 1 of every 10(4) T cells it supposedly kills in AIDS, whereas about 5% of all T cells are regenerated during the 2 days it takes the virus to infect a cell. (iii) If HIV were the cause of AIDS, it would be the first virus to cause a disease only after the onset of antiviral immunity, as detected by a positive "AIDS test." (iv) AIDS follows the onset of antiviral immunity only after long and unpredictable asymptomatic intervals averaging 8 years, although HIV replicates within 1 to 2 days and induces immunity within 1 to 2 months. (v) HIV supposedly causes AIDS by killing T cells, although retroviruses can only replicate in viable cells. In fact, infected T cells grown in culture continue to divide. (vi) HIV is isogenic with all other retroviruses and does not express a late, AIDS-specific gene. (vii) If HIV were to cause AIDS, it would have a paradoxical, country-specific pathology, causing over 90% Pneumocystis pneumonia and Kaposi sarcoma in the U.S. but over 90% slim disease, fever, and diarrhea in Africa.(viii) It is highly improbable that within the last few years two viruses (HIV-1 and HIV-2) that are only 40% sequence-related would have evolved that could both cause the newly defined syndrome AIDS. Also, viruses are improbable that kill their only natural host with efficiencies of 50-100%, as is claimed for HIVs. It is concluded that HIV is not sufficient for AIDS and that it may not even be necessary for AIDS because its activity is just as low in symptomatic carriers as in asymptomatic carriers. The correlation between antibody to HIV and AIDS does not prove causation, because otherwise indistinguishable diseases are now set apart only on the basis of this antibody. I propose that AIDS is not a contagious syndrome caused by one conventional virus or microbe. No such virus or microbe would require almost a decade to cause primary disease, nor could it cause the diverse collection of AIDS diseases. Neither would its host range be as selective as that of AIDS, nor could it survive if it were as inefficiently transmitted as AIDS. Since AIDS is defined by new combinations of conventional diseases, it may be caused by new combinations of conventional pathogens, including acute viral or microbial infections and chronic drug use and malnutrition. The long and unpredictable intervals between infection with HIV and AIDS would then reflect the thresholds for these pathogenic factors to cause AIDS diseases, instead of an unlikely mechanism of HIV pathogenesis.

AIDS-Kaposi's sarcoma-derived cells express cytokines with autocrine and paracrine growth effects

When grown in vitro, cells from Kaposi's sarcoma lesions of AIDS patients (AIDS-KS cells) constitutively release several growth promoting activities. When inoculated into nude mice, the AIDS-KS cells induce a KS-like lesion of mouse origin. Here it is shown that the AIDS-KS cells express messenger RNA for a complex mixture of cytokines that correlate with several of the biological activities of these cells. Basic fibroblast growth factor, which is a potent angiogenic factor, and interleukin-1 messenger RNAs are expressed at very high levels and seem to account for a large proportion of the activities, since their corresponding proteins are released in biologically active form into the culture media where they induce autocrine and paracrine growth effects.

Human retroviruses: cancer and AIDS

Human retroviruses are associated with a wide spectrum of clinical entities including cancers, immune deficiency and neurological disorders. They have become the focal point of all retrovirology by virtue of their extreme clinical relevance, their novel and complex biologic and genetic properties, as well as their regulation strategies. The study of these viruses is of great importance as understanding of their interactions with the host will ultimately shed light on fundamental mechanisms of genetic controls in human cells in their normal state and the alterations in these controls in neoplastic or immunologically aberrant states.

Kaposi's sarcoma cells: long-term culture with growth factor from retrovirus-infected CD4+ T cells

Studies of the biology and pathogenesis of Kaposi's sarcoma (KS) have been hampered by the inability to maintain long-term cultures of KS cells in vitro. In this study AIDS-KS-derived cells with characteristic spindle-like morphology were cultured with a growth factor (or factors) released by CD4+ T lymphocytes infected with human T-lymphotropic virus type I or II (HTLV-I or HTLV-II) or with human immunodeficiency virus type 1 or 2 (HIV-1 or HIV-2). Medium conditioned by HTLV-II-infected, transformed lines of T cells (HTLV-II CM) contained large amounts of this growth activity and also supported the temporary growth of normal vascular endothelial cells, but not fibroblasts. Interleukin-1 and tumor necrosis factor-alpha stimulated the growth of the KS-derived cells, but the growth was only transient and these could be distinguished from that in HTLV-II CM. Other known endothelial cell growth promoting factors, such as acidic and basic fibroblast growth factors and epidermal growth factor, did not support the long-term growth of the AIDS-KS cells. The factor released by CD4+ T cells infected with human retroviruses should prove useful in studies of the pathogenesis of KS.

Angiogenic properties of Kaposi's sarcoma-derived cells after long-term culture in vitro

Cells derived from lung biopsies and pleural effusions from AIDS patients with Kaposi's sarcoma (KS) of the lungs were established in long-term culture with the aid of conditioned medium from HTLV-II-transformed T cells (HTLV-II CM). These AIDS-KS cells were similar to the so-called spindle cells in KS lesions and had some of their features. They produced factors that supported their own growth (autocrine) and the growth of other cells (paracrine), including umbilical vein endothelium and fibroblasts. That the AIDS-KS cells also expressed potent angiogenic activity was demonstrated by the chorioallantoic membrane assay and by subcutaneous inoculation of AIDS-KS cells into nude mice, which resulted in the development of angiogenic lesions composed of mouse cells and showing histological features similar to those of human KS lesions. These data suggest that AIDS-associated KS and possibly other types of KS may be initiated by signals that induce the growth of particular cells (spindle cells of lymphatic or vascular origin) and the expression of autocrine and paracrine activities.