Sarcoma Spindle Cells Research Articles

Evidence for Kaposi Sarcoma Originating from Mesenchymal Stem Cell through KSHV-induced Mesenchymal-to-Endothelial Transition.

The major transmission route for Kaposi sarcoma-associated herpesvirus (KSHV) infection is the oral cavity through saliva. Kaposi sarcoma (KS) frequently occurs in the oral cavity in HIV-positive individuals and is often the first presenting sign of AIDS. However, the oral target cells for KSHV infection and the cellular origin of Kaposi sarcoma remain unknown. Here we present clinical and experimental evidences that Kaposi sarcoma spindle cells may originate from virally modified oral mesenchymal stem cells (MSC). AIDS-KS spindle cells expressed neuroectodermal stem cell marker (Nestin) and oral MSC marker CD29, suggesting an oral/craniofacial MSC lineage of AIDS-associated Kaposi sarcoma. Furthermore, oral MSCs were highly susceptible to KSHV infection, and infection promoted multilineage differentiation and mesenchymal-to-endothelial transition (MEndT). KSHV infection of oral MSCs resulted in expression of a large number of cytokines, a characteristic of Kaposi sarcoma, and upregulation of Kaposi sarcoma signature and MEndT-associated genes. These results suggest that Kaposi sarcoma may originate from pluripotent MSC and KSHV infection transforms MSC to Kaposi sarcoma-like cells through MEndT.Significance: These findings indicate that Kaposi sarcomas, which arise frequently in AIDS patients, originate from neural crest-derived mesenchymal stem cells, with possible implications for improving the clnical treatment of this malignancy. Cancer Res; 78(1); 230-45. ©2017 AACR.

Expression of PROX‐1 in oral Kaposi's sarcoma spindle cells

The histogenesis of neoplastic spindle cells of Kaposi's sarcoma is still uncertain, but some studies consider it a lymphatic vessel differentiation. Prox-1 is a nuclear transcription factor that plays a major role during embryonic lymphangiogenesis, and it has been considered a specific and sensitive lymphatic endothelial cell marker. The aim of this study was to determine the expression of Prox-1 in oral Kaposi's sarcoma comparing the results with oral benign vascular tumors including capillary hemangiomas and pyogenic granulomas. Expression of Prox-1 and HHV-8 was evaluated by immunohistochemistry in 30 oral Kaposi's sarcoma, 5 oral capillary hemangiomas, and 10 oral pyogenic granulomas. The labeling index was expressed as the percentage of positive cells for each case studied. Statistical comparison was performed using the Wilcoxon-Mann-Whitney rank sum test. Twenty-eight (93.3%) and 30 oral Kaposi's sarcoma cases were positive for Prox-1 and HHV-8, respectively, while all oral benign vascular tumors were negative for these markers. The number of Prox-1 and HHV-8 oral Kaposi's sarcoma-positive cells increased significantly from patch/plaque to nodular histological stages. The expression of Prox-1 in the neoplastic spindle cells supports the view of a lymphatic differentiation in oral Kaposi's sarcoma. Prox-1 may also be involved in the pathogenesis of oral Kaposi's sarcoma as the number of positive spindle cells increased progressively from patch to nodular stages and could be eventually useful as an additional diagnostic tool for differential diagnosis between oral Kaposi's sarcoma and benign oral vascular lesions.

Reconstitution of immune responses against Kaposi sarcoma-associated herpesvirus

Reconstitution of immune responses against Kaposi sarcoma-associated herpesvirus

Lymphatic and vascular origin of Kaposi's sarcoma spindle cells during tumor development

The histogenesis of Kaposi's sarcoma (KS) tumor spindle cells (SC) remains controversial but several immunohistochemical studies favor a lymphatic origin. Twenty KS surgical biopsies were analyzed for the coexpression of LANA, CD34, LYVE-1, D2-40, VEGFR-2, VEGFR3 by using double or triple immunostaining. Most of the SC in both early and late KS expressed the lymphatic markers LYVE-1, D2-40 and VEGFR-3 and the blood vascular endothelial/endothelial precursor cell markers CD34 and endothelial stem cell marker VEGFR-2. All the LANA+ SC in early and late KS were LYVE-1+, but only 75% of these LANA+ cells were CD34(+). The CD34(+)/LANA+ cells increased from early- (68.8%) to late-stage KS (82.2%). However, approximately 18% of the LANA+ SC in early KS were CD34(-) but were LYVE-1+, suggesting that resident lymphatic endothelial cells (LEC) are targeted for primary infection by human herpesvirus-8. This LANA+/LYVE-1+/CD34(-) (resident LEC) cell population clearly decreased during the development of KS from early (18.7%) to late KS (2.9%). Thus, in late stages of KS, most SC were LANA+/CD34(+)/LYVE-1+. However, in both early- and late-stage KS, approximately 18% of the SC were CD34(+)/LANA-/LYVE-1 -- and could represent newly recruited endothelial precursor cells, which become infected in the lesion and eventually undergo a phenotype switch expressing LEC markers. Our study apparently indicates that KS represents a unique variant of tumor growth with continues recruitment of tumor precursor cells as well as proliferation and decreased apoptosis of SC.

Spindle cells and their role in Kaposi's sarcoma

Spindle cells represent the main cell type of the advanced final nodular stage of Kaposi's sarcoma lesions. Despite some clinical and epidemiological differences, the four Kaposi's sarcoma forms (classic, endemic, post-transplant and epidemic) display very similar histopathological features, with the proliferation of spindle cells (considered as the Kaposi's sarcoma tumor cells) associated with inflammation and neo-angiogenesis. Electron-microscopy and immuno-histochemistry studies have led to the consensus that the spindle cells originated from the endothelial lineage. However, only recently, studies that used specific lymphatic immunological markers (such as podoplanin) and molecular features (gene expression microarrays) strongly linked Kaposi's sarcoma spindle cells to the endothelium lymphatic cell lineage. Both hybridization and immuno-histochemistry techniques have demonstrated that human herpesvirus 8 also known as Kaposi's sarcoma associated herpesvirus was present in spindle cells at all stages of the disease (patch, plaque, nodule). Interestingly, while the human herpesvirus 8 latent genes are expressed in nearly all tumor spindle cells, only a small fraction of them expresses markers of viral lytic replication. Recent findings showing that nodular Kaposi's sarcoma lesions display all patterns of human herpesvirus 8 clonality support the model according to which this tumor begins as a polyclonal disease with a subsequent evolution to a mono/oligoclonal process involving infected spindle cells. Spindle cells appear to be the central masterpiece in KS tumorigenesis, however the exact respective role of each human herpesvirus 8 gene, in the initiation and the disease progression is still under investigation and the question of whether or not this tumor is a reactive process or a true malignant proliferation of spindle cells remains yet unclear.

Alpha-chemokine-mediated signal transduction in human Kaposi's sarcoma spindle cells

The role of chemokines and their receptors in HIV biology and Kaposi's sarcoma (KS) pathogenesis has recently gained considerable attention. It has been shown that KS-associated human herpes virus type 8 (KSHV/HHV-8) encodes functional homologues of certain chemokines and chemokine receptors. This suggests that chemokines may contribute to the growth and spread of KS seen in AIDS. We found the expression of CXCR4 in primary KS tissue by using in situ hybridization (ISH). Recently, alpha-chemokine receptors CXCR1 and CXCR2 have also been shown to be expressed by KS tissues. We further characterized the expression of these chemokines as well as the signaling events induced upon binding to their respective cognate ligands in the KS 38 spindle cell line. These cells express authentic characteristics of primary KS spindle cells and provide a useful in vitro model for these studies. We observed using RT-PCR that KS 38 cells express mRNA for the alpha-chemokine receptors CXCR1, CXCR2, and CXCR4. We also confirmed the cell surface protein expression by FACS analysis. Characterization of signaling pathways revealed that the alpha-chemokines, IL-8 and stromal cell-derived factor 1α (SDF1α/CXCL12), activated members of the mitogen-activated protein (MAP) kinase family, including Erk kinase, c-Jun amino terminal kinase (JNK)/stress-activated protein kinase (SAPK) and the p38 MAP kinase. Furthermore, using DNA protein-binding experiments, we have shown that IL-8 increased AP-1 and NF Kappa B activity in these cells. IL-8 also enhanced the chemotaxis of KS cells. These results reveal that chemokine-induced signaling pathways may mediate cell growth, transcriptional activation and cell migration in KS.

Expression of K13/v-FLIP Gene of Human Herpesvirus 8 and Apoptosis in Kaposi's Sarcoma Spindle Cells

Human herpesvirus 8 (HHV8) infection is associated with all forms of Kaposi's sarcoma (KS). The HHV8 genome locus ORFK13-72-73 (ORF = open reading frame) encodes proteins that may be important in HHV8-mediated pathogenesis, i.e., the latency-associated nuclear antigen (encoded by ORF73), viral-cyc-D (v-cyc-D), a viral homologue of cellular cyclin D (encoded by ORF72), and viral-FLIP (v-FLIP), a homologue of the cellular FLICE (Fas-associated death domain-like interleukin 1 beta-converting enzyme) inhibitory protein (encoded by ORFK13; is an inhibitor of apoptosis [programmed cell death]). Through differential splicing events, this locus expresses individual RNA transcripts that encode all three proteins (tricistronic transcripts) or just two of them (v-FLIP and v-cyc-D; bicistronic transcripts). We examined expression of these transcripts in KS tissues. We collected tissues from patients with KS of different stages. By use of an optimized in situ hybridization procedure, we examined different ORFK13-72-73 locus transcripts in HHV8-infected cells in skin lesions and in one adjacent lymph node. Apoptosis in KS lesions was determined by use of an in situ assay. Our results indicate the following: 1) Transcripts from the ORFK13-72-73 locus appear to be spliced differentially in latently infected KS cells in skin lesions and in HHV8-infected cells in lymph nodes; specifically, ORFK13-ORF72 bicistronic transcripts were expressed abundantly in KS cells, whereas ORFK13-ORF72-ORF73 tricistronic transcripts were detected only in lymph node cells. 2) Sequences encoding the antiapoptotic protein v-FLIP are expressed at very low levels in early KS lesions, but expression increases dramatically in late-stage lesions. 3) The increase in expression of v-FLIP-encoding transcripts is associated with a reduction in apoptosis in KS lesions. These data suggest that functional v-FLIP is produced in vivo and that antiapoptotic mechanisms may be involved in the rapid growth of KS lesions, where only a few cells undergoing mitosis are generally observed.

Expression of Human Herpesvirus 8-Encoded Cyclin D in Kaposi's Sarcoma Spindle Cells

Human herpesvirus 8 (HHV-8) DNA sequences have been detected in Kaposi's sarcoma, in primary effusion lymphoma (an unusual high-grade non-Hodgkin's lymphoma seen primarily in patients with acquired immunodeficiency syndrome [AIDS]), and in Castleman's disease (a rare lymphoproliferative disorder); however, proof that HHV-8 is involved in the pathogenesis of these diseases remains to be established. HHV-8 contains a gene, i.e., v-cyclin D, that is a homologue of the cellular cyclin D2 gene, which encodes a protein that promotes passage through G1 phase of the cell cycle. Previous studies have identified v-cyclin D messenger RNA (mRNA) in biopsy specimens of Kaposi's sarcoma. In this study, we isolated a full-length v-cyclin D complementary DNA and characterized the pattern of v-cyclin D mRNA expression in Kaposi's sarcoma. Standard methods were used to construct and to screen HHV-8 genomic and complementary DNA libraries. Reverse transcription-polymerase chain reaction (RT-PCR) methods and in situ hybridization with RNA probes were used to examine v-cyclin D mRNA expression. RT-PCR demonstrated the presence of v-cyclin D mRNA in biopsy specimens of AIDS-related Kaposi's sarcoma, in early-passage spindle cells from classical (i.e., not AIDS-related) Kaposi's sarcoma, and in spindle cells isolated from the peripheral blood of patients with AIDS-related Kaposi's sarcoma. In situ hybridization indicated that mRNAs for v-cyclin D and kaposin, an HHV-8 latency-associated gene, were present in approximately 1% of the spindle cells in early patch lesions and approximately 60% of the spindle cells in late nodular lesions of Kaposi's sarcoma. Spindle cells of Kaposi's sarcoma, which have been regarded as the tumor cells of this cancer, contain v-cyclin D mRNA. Expression of v-cyclin D protein may be involved in the pathogenesis of Kaposi's sarcoma by promoting cell proliferation.

Spindle cells isolated from Kaposi's sarcoma-like lesions of BKV/tat-transgenic mice co-express markers of different cell types.

To characterize murine spindle cells isolated from Kaposi's sarcoma-like skin lesions developed in BK virus (BKV)/tat-transgenic mice. Kaposi's sarcoma-like spindle cells isolated from the lesions were propagated in vitro, and their phenotype was investigated using a panel of antibodies against various cell markers and angiogenic factors. Immunofluorescence and Western blot techniques were used. We observed co-expression of antigens specific for endothelial, smooth muscle and antigen-presenting cells, suggesting that cells from the TTB cell line represent poorly differentiated vascular precursors. Since TTB cells were derived from highly vascularized skin lesions, it is noteworthy that they synthesize a complex mixture of angiogenic factors, including fibroblast growth factor-2, vascular endothelial growth factor, placental growth factor, and hepatocyte growth factor. Due to their role in invasiveness and angiogenesis, we also observed the expression of urokinase plasminogen activator (uPA), uPA receptor, and plasminogen activator inhibitor-type 1 by TTB cells. Our results suggest that TTB cells share several features with human Kaposi's sarcoma spindle cells and can be a useful in vitro system to study the molecular mechanisms involved in Kaposi's sarcoma pathogenesis. Moreover, they synthesize a complex mixture of angiogenic factors and are growth-inhibited by the anti-angiogenic drug AGM-1470.

An Autocrine Loop of HIV Type-1 Tat Protein Responsible for the Improved Survival/Proliferation Capacity of Permanently Tat-Transfected Cells and Required for Optimal HIV-1 LTR Transactivating Activity

Human immunodeficiency virus type 1 (HIV-1) transactivating Tat protein is pivotal to virus replication. Tat's potential effects on HIV-1 pathogenesis, however, go well beyond its role in the virus's life cycle. Current data indicate that biologically active Tat is released from HIV-1-infected cells and readily endocytosed and targeted to the nucleus of nearby, or perhaps distant, cells, where it may exert a series of pleiotropic effects. This paracrine action has been extensively investigated, and depending on the amounts of exogenously added Tat, its effects may extend from the suppression of immunocompetent cells to transactivation of heterologous genes to the promotion of growth of Kaposi's sarcoma spindle cells. We have already observed that various cell lines, either permanently transfected with an expressive HIV-1 tat gene construct or cultured in the presence of exogenously added Tat protein, are protected from programmed cell death after serum withdrawal or other apoptotic stimuli. The present article shows that various types (lymphoblastoid, epithelial, neuronal) of permanently tat-transfected cell lines actively release fully bioactive Tat protein. The addition of anti-Tat antibody to the culture medium completely abolishes their increased survival/proliferation capacity in serum-free culture. In these conditions, therefore, the enhanced survival/proliferation potential of permanently tat-transfected cells seems entirely dependent on a Tat-protein autocrine loop. The finding that anti-Tat antibody, added to culture medium, exerts a negative influence on the expression of a Tat-responsive HIV-1 long terminal repeat chloramphenicol-acetyltransferase construct, transiently transfected into permanently tat-transfected cells, suggests that the Tat autocrine loop may also be required for optimal HIV-1 long terminal repeat transactivation.

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells.

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

HIV-associated Kaposi's sarcoma spindle cells: smooth muscle origin and immunological link

Here I will focus on (i) a possible smooth muscle cell (SMC) origin of HIV-associated Kaposi's sarcoma (KS) spindle cells, and (ii) their growth control by activated immune cell-derived cytokines. Biomedical Reviews 1993; 2: 77-78.

AIDS-associated Kaposi's sarcoma pathogenesis, clinical features, and treatment.

Kaposi's sarcoma is the most common tumor associated with HIV-1 infection. Kaposi's sarcoma is seen most frequently among homosexual or bisexual men, the reasons for which are unknown. Culture of Kaposi's sarcoma spindle cells has been very useful to study various biologic features of the tumor and to develop novel drug therapy. Treatment of AIDS-associated Kaposi's sarcoma is planned based on tumor burden, immunologic status of the patient, and bone marrow rescue. All treatment types at present only provide palliation, whereas efforts to find more effective therapy and possibly preventive therapy are in progress.